United States

Department of

Commerce

Technology

Administration

National

Institute of

Standards and

Technology

SPECIFICATIONS, TOLERANCES,

AND OTHER TECHNICAL

REQUIREMENTS FOR WEIGHING

AND MEASURING DEVICES

as adopted by

the 87th

National

Conference on

Weights and

Measures 2002

44

2003

NIST Handbook
Specifications, Tolerances,

and Other Technical 

Requirements for 

Weighing and Measuring Devices

as adopted by the 87th National Conference on Weights and Measures 2002

Editors:

Terry L. Grimes

Richard Suiter

Juana Williams

Henry V. Oppermann, Chief

NIST Weights and Measures Division

Gaithersburg, MD 20899-2600

U.S. Department of Commerce

Donald L. Evans, Secretary

Technology Administration

Phillip J. Bond, Under Secretary

of Commerce for Technology

National Institute of

Standards and Technology

Arden L. Bement, Jr., Director

NIST Handbook 44

2003 Edition (issued November 2002)

Supersedes NIST Handbook 44, 2002 Edition

December 2002
Certain commercial entities, equipment, or materials may be indentified in this document 

in order to describe an experimental procedure or concept adequately. Such

identification is not intended to imply recommendation or endorsement by the National 

Institute of Standards and Technology, nor is it intended to imply that the entities, 

materials, or equipment are necessarily the best available for the purpose.

National Institute of Standards and Technology Handbook 44, 2003 Edition

Natl. Inst. Stand. Technol. Handb. 44, 2003 Ed., 309 pages (Dec. 2002)

CODENL NIHAE2

U. S. GOVERNMENT PRINTING OFFICE

WASHINGTON: 2002

For sale by the Superintendent of Documents, U.S. Government Printing Office

Internet: bookstore.gpo.gov — Fax: (202) 512-2250

Mail: Stop SSOP, Washington, DC 20402-0001
iii

Foreword

Handbook 44 was first published in 1949, having been preceded by similar handbooks of various designations and 

in several forms, beginning in 1918.

Handbook 44 is published in its entirety each year following the Annual Meeting of the National Conference on 

Weights and Measures (NCWM). The Committee on Specifications and Tolerances of the NCWM developed the 

2003 Edition with the assistance of the Weights and Measures Division (WMD) of the National Institute of 

Standards and Technology (NIST). This handbook includes amendments endorsed by the 87th National Conference 

on Weights and Measures during its Annual Meeting in 2002.

NIST has a statutory responsibility for "cooperation with the States in securing uniformity of weights and measures 

laws and methods of inspection." In partial fulfillment of this responsibility, NIST is pleased to publish these 

recommendations of the NCWM.

Arden L. Bement, Jr. 

Director

National Institute of Standards

 and Technology

This handbook conforms to the concept of primary use of SI (metric) measurements recommended in the Omnibus 

Trade and Competitiveness Act of 1988 by citing SI units before inch-pound units where both units appear together 

and placing separate sections containing requirements in SI units before corresponding sections containing 

requirements in inch-pound units. In some cases, however, trade practice is currently restricted to the use of inchpound units; therefore, some requirements in this handbook will continue to specify only inch-pound units until the 

NCWM achieves a broad consensus on the permitted SI units. 

In accord with NIST policy, the meter/liter spellings are used in this document. However, the metre/litre spellings 

are acceptable, and are preferred by the NCWM.

It should be noted that a space has been inserted instead of commas in all numerical values greater than 9999 in this 

document, following a growing practice, originating in tabular work, to use spaces to separate large numbers into 

groups of three digits. This avoids conflict with the practice in many countries to use the comma as a decimal 

marker.
iv

Committee on Specifications and Tolerances

of the 87th Conference

Mark Coyne, Brockton, MA

Clark Cooney, OR

Gary L. Ebinger, Huron County, OH (Interim Meeting)

Jack Kane, MT

Craig Van Buren, MI

Richard W. Wotthlie, Maryland

Ted Kingsbury, Canada, Technical Advisor

Juana Williams and Richard Suiter, NIST, Technical Advisors

Past Chairmen of the Committee

Conference Chairman Conference Chairman

8-11 L.A. Fischer, NBS

12-28 F.S. Holbrook, NBS

29-38 J.P. McBride, MA

39-42 R.E. Meek, IN

43-44 J.E. Brenton, CA

45-47 C.L. Jackson, WI

48 T.C. Harris, VA

49-50 R.E. Meek, IN

51-52 G.L. Johnson, KY

53 H.D. Robinson, ME

54-55 R. Rebuffo, NE

56-57 D.E. Konsoer, WI

58 J.C. Mays, FL

59 T.F. Brink, VT

60 W.S. Watson, CA

61 K.J. Simila, OR

62 W.E. Czaia, MN

63 M.L. Kinlaw, NC

64 J.A. Bird, NJ

65 D.A. Guensler, CA

66 G.A. Delano, MT

67 F.C. Nagele, MI

68 L.H. DeGrange, MD

69 S.A. Colbrook, IL

70 D.A. Guensler, CA

71-72 F. Gerk, NM

74 R. Andersen, NY

75 D. Watson, TX

76 J. Truex, OH

77 C. Carroll, MA

78 C. Carroll, MA

79 J. Jeffries, FL

80 R. Suiter, NE

81 G. West, NM

82 R. Murdock, NC

83 R. Murdock, NC

84 D. Brown, IA

85 M. Hopper, CA

86 G. Schefcheck, OR
v

Outline of Contents

 Page

Foreword iii

2002 Amendments vii

Introduction 1

Section 1.

1.10. General Code 1-1

Section 2.

2.20. Scales 2-3

2.21. Belt-Conveyor Scale Systems 2-41

2.22. Automatic Bulk Weighing Systems 2-51

2.23. Weights 2-57

2.24. Automatic Weighing Systems - Tentative Code 2-61

Section 3.

3.30. Liquid-Measuring Devices 3-3

3.31. Vehicle-Tank Meters 3-23

3.32. Liquefied Petroleum Gas and Anhydrous

Ammonia Liquid-Measuring Devices 3-31

3.33. Hydrocarbon Gas Vapor-Measuring Devices 3-41

3.34. Cryogenic Liquid-Measuring Devices 3-49

3.35. Milk Meters 3-57

3.36. Water Meters 3-63

3.37. Mass Flow Meters 3-67

3.38. Carbon Dioxide Liquid-Measuring Devices 3-77

Section 4.

4.40. Vehicle Tanks Used as Measures 4-3

4.41. Liquid Measures 4-7

4.42. Farm Milk Tanks 4-9

4.43. Measure-Containers 4-15

4.44. Graduates 4-19

4.45. Dry Measures 4-23

4.46. Berry Baskets and Boxes 4-25
vi

Outline of Contents (Continued)

Section 5.

5.50. Fabric-Measuring Devices 5-3

5.51. Wire- and Cordage-Measuring Devices 5-7

5.52. Linear Measures 5-11

5.53. Odometers 5-13

5.54. Taximeters 5-17

5.55. Timing Devices 5-23

5.56.(a) Grain Moisture Meters 5-27

5.56.(b) Grain Moisture Meters 5-35

5.57. Near-Infrared Grain Analyzers 5-41

5.58. Multiple Dimension Measuring Devices - Tentative Code 5-49

Appendices

A. Fundamental Considerations A-1

B. Units and Systems of Measurement B-1

C. General Tables of Units of Measurement C-1

D. Definitions D-1
vii

2002 Amendments

The following table lists the codes, paragraphs, and pages in which amendments were made by the 87th National 

Conference on Weights and Measures. In the column headed "Action," changes are noted as "added," "amended," 

"deleted," or "renumbered." Each code, section, or paragraph that has been changed will be noted as "Added 2002" 

or "Amended 2002."

SECTION CODE S&T ITEM 

NO.

PARAGRAPH ACTION PAGE

2.20. Scales 320-1A

S.6.1. Amended 2-14

Table S.6.3.a.

Note 22

Amended 2-15

Table S.6.3.b.

Item 9

Amended 2-16

Table S.6.3.b.

Item 12

Amended 2-16

Table S.6.3.b.

Item 14

Amended 2-17

Table S.6.3.b.

Item 22

Amended 2-17

2.21. Belt-Conveyor

321-1 S.1.4.1. Added 2-41

UR.3.2. (f) Added 2-49

321-2 S.3.1. Amended 2-42

321-3

N.1. Amended 2-43

N.3.2. Amended 2-44

321-4

N.3.1.1 Added 2-44

N.3.1.2. Added 2-44

N.3.1.3. Added 2-44

N.3.1.4. Added 2-44

321-5 UR.2.2. (a) Amended 2-47

321-6 UR.3.2. (b) Amended 2-48

321-7 UR.3.3. Amended 2-49

3.30. Liquid–Measuring 

Devices

330-1 S.3.2. Amended 3-12

330-3A Tolerances

Table T.2

Added Table 3-16

T.3. Repeatability test

Renumbered

3-16

T.4. Automatic 

Temperature 

Compensating 

Systems

Renumbered

3-17

330-8 S.4.4.1 Amended 3-13

S.4.4.2. Section Added 3-13

3.31. Vehicle-Tank Meters

331-3 Tolerances Table 1. Added Table 1 3-28

T.4.3. Renumbered 

Repeatability

3-28

3.3.

Hydrocarbon Gas 

Vapor-Measuring 

Devices

333-1 N.4.1.2. Added 3-46
viii

SECTION CODE S&T ITEM 

NO.

PARAGRAPH ACTION PAGE

T.2. Added 3-47

3.34. Cryogenic LiquidMeasuring Devices334-1 S.1.1.2. Amended 3-51

S.1.1.3. Amended 3-51

S.2.4. Amended 3-53

3.35. Milk Meters 335-1 N.4.1.1. Added 3-62

T.3. Added 3-63

3.36 Water Meters 336-1 A.1. Amended 3-65

S.1.1.1. Amended 3-65

N.4.1. Amended 3-67

Table 1 Amended 3-68

Table 2 Amended 3-69

336-2 N.4.1.1. Added 3-67

T.1.1 Added 3-67

3.37. Mass Flow Meters 337-1 S.4.1. Amended 3-74

3.38. Carbon Dioxide LiquidMeasuring Devices338-1 Changed the Code 

from tentative to 

permanent

3-81

338-2 N.4.1.1. Added 3-84

T.2.3. Added 3-85

3.57. Near-Infrared Grain 

Analyzers

357-1A Changed the Code 

from tentative to 

permanent

5-43

310-2B Appendix D. Element Added D-6

321-1 Automatic zero-setting 

mechanism

Added D-2

Zero-load reference 

(belt-conveyor scales)

Added D-20

Zero-setting mechanism 

(belt-conveyor scales)

Added D-20

330-5 Contract sale Amended D-4

330-6 Dry hose Amended D-6

Wet hose Amended D-20

Wet-hose type Amended D-20
ix

2002 Editorial Changes

Section Code Paragraph Action Page

2.20 Scales Table S.6.3.a. Added CC marking requirement to be 

consistent with G-S.1.(g) (Added 2001)

2-15

Table S.6.3.b. Added note 23 to be consistent with GS.1.(g) (Added 2001)2-17

2.21 Belt-Conveyor 

Scales

S.3.1. Edited 2002 adopted language for clarity 2-42

2.21 Belt-Conveyor 

Scales

UR.3.3. Changed the term “chart recorder” in 2002 

adopted language to “analog or digital 

recorder” to be consistent with existing H 44 

terminology.

2-49

2.24.

Automatic 

Weighing 

Systems

Table S.7.a. Added CC marking requirement to be 

consistent with G-S.1.(g) (Added 2001)

2-65

Table S.7.b. Added note 23 to be consistent with 

G-S.1.(g) (Added 2001)

2-66

3.30.

5.56.(a)

Grain 

Moisture 

Meters

Table S.1.2. Amended 5-28

5.57.

Near Infrared 

Grain 

Analyzers

Entire Code Deleted “and effective” from nonretroactive 

statements for consistency with other 

references.

5-37 

through 

42

5.58

Multiple 

Dimension 

Measuring 

Devices

N.1.3. Reference to T.7. corrected to T.6. 5-53

Table S.4.1.a. Added CC marking requirement to be 

consistent with G-S.1.(g) (Added 2001)

5-58

Table S.4.1.b. Added note 23 to be consistent with GS.1.(g) (Added 2001)5-58

Appendix 

C

General 

Tables of 

Units of 

Measurement

Italicized “statute mile” and “survey foot” for 

consistency and to eliminate ambiguity with 

NIST SP 811.

C-15

Appendix 

D

Definitions Updated code references to definitions -

Belt-Conveyor 

Scale

“Chart recorder” amended to “Analog or 

digital recorder” (Code Amended 1989)

D-1

Scales Definition of “coal-mine scale” deleted (term 

is not used in H 44)

Liquid Measuring 

Devices

“Gravity type” amended to “Gravity 

discharge” (Gravity type is not used in H 44)

D-8

Hydrocarbon Gas 

Vapor-Measuring 

Devices

“Portable cubic foot standard” deleted. (term 

is not used in H 44)

-

Farm Milk Tanks “Prover test method” amended. The word 

test in not used in association with the term 

“prover method.”

D-14
x
Introduction

1

Introduction

A. Source. - The specifications, tolerances, and other technical requirements published herein comprise, in their latest 

form, all of the current codes as adopted by the National Conference on Weights and Measures (NCWM), Inc.1

 NCWM 

is supported by the National Institute of Standards and Technology (NIST), which provides the NCWM secretariat and 

publishes documents. NIST also develops technical publications for use by weights and measures agencies; these 

publications may subsequently be endorsed or adopted by the NCWM.

The NCWM Committee on Specifications and Tolerances,2 acting at the request of the NCWM or upon its own initiative, 

with the technical assistance of NIST, annually prepares proposed revisions, amendments, or additions to the material 

previously adopted by the NCWM. (See paragraph C.) Such revisions, amendments, or additions are then presented to 

the Conference as a whole, where they are discussed by weights and measures officials and representatives of interested 

manufacturers and industries. Eventually the proposals of the Committee are voted upon only by the weights and 

measures officials.

All of the specifications, tolerances, and other technical requirements given herein are recommended by the National 

Conference on Weights and Measures for official promulgation in and use by the States in exercising their control of 

commercial weighing and measuring apparatus. A similar recommendation is made with respect to the local jurisdictions 

within a State in the absence of the promulgation of specifications, tolerances, and other technical requirements by a State 

agency.

B. Purpose. - The purpose of these technical requirements is to eliminate from use, weights and measures and weighing 

and measuring devices that give readings that are false, that are of such construction that they are faulty (that is, that are 

not reasonably permanent in their adjustment or will not repeat their indications correctly), or that facilitate the 

perpetration of fraud, without prejudice to apparatus that conforms as closely as practicable to the official standards.

C. Amendments. - The Committee on Specifications and Tolerances of the NCWM provides a mechanism for 

consideration of amendments or additions to the specifications, tolerances, and other technical requirements. 

D. Submission of Agenda Items - Preamble. - The Constitution of the NCWM requires that its officers and Committees 

observe the principles of due process for the protection of the rights and interests of affected parties. Specifically, it 

requires that Committees and Officers: (a) give reasonable advance notice of contemplated studies, issues to be 

considered for action, and tentative or definite recommendations for conference vote, and (b) provide that all interested 

parties have an opportunity to be heard. 

E. Submission Process. - Anyone introducing an issue to the Committee shall use the regional weights and measures 

associations to initially consider its merits. Using the regional associations ensures discussion and evaluation of issues at 

the grass-roots level by involving the regional members in the development, evaluation, and justification of proposals. 

The regions include the Central, Northeastern, Southern, and Western Weights and Measures Associations. For 

information on the regional associations contact NCWM, Inc., 15245 Shady Grove Road, Suite 130, Rockville, MD 

20850 or by telephone at (240) 632-9454.

_____________________________________________________________________________________________

1 When sitting as a voting body, the National Conference on Weights and Measures (NCWM) is made up of State and 

local weights and measures officials from all parts of the United States. The NCWM normally meets annually.

2 Communications to this committee may be addressed as follows: Executive Secretary, National Conference on Weights 

and Measures, National Institute of Standards and Technology, 100 Bureau Drive, Stop 2600, Gaithersburg, MD 20899-

2600.
Introduction

2

F. Procedures.

The Committee will consider issues according to the following procedures:

a. All issues to be considered by the Committee for action at the upcoming Interim Meeting must be submitted in 

writing to the Committee by October 15. Although use of NCWM Form 15 (see page 6) is not required, it is 

recommended for use in submitting proposals to the NCWM. Proposals shall be sent to the Committee at:

NIST Office of Weights and Measures

100 Bureau Drive, Stop 2600

Gaithersburg, Maryland 20899-2600

Attention: Specifications and Tolerances Committee 

b. A copy of the proposal must be sent to the NCWM’s Executive Secretary at the same address. 

G. Criteria for Inclusion in the Committee’s Agenda.

a. Any issue approved by at least one regional association and received by the November 1 deadline will be 

automatically placed on the Committee’s Interim Meeting Agenda. 

b. Issues that have not been approved by a regional association, but which are received by November 1, will be 

evaluated by the Committee using the criteria in Section H, Exceptions to Policy and Section I, Committee Agenda.

c. Any proposal received after the November 1 deadline, but prior to the Interim Meeting, will be evaluated by the 

Committee according to Section H, Exceptions to Policy and Section I, Committee Agenda. Only those issues 

determined to be a national “Priority” will be included on its agenda. 

d. Proposals must be in writing and must include: 

(1) a concise statement of the issue or problem outlining the purpose and national need for its consideration. 

When possible, an electronic copy of the background material and proposed amendment(s) should be submitted in 

a PC compatible word processing document format (e.g., Corel WordPerfect or Microsoft Word) on a high 

density 8.9 cm (3.5 inch) disk or by electronic mail using the same format;

(2) background material including test data, analysis of test data, or other appropriately researched and 

documented material from which the Committee will be able to make a judgment for either a firm recommendation or consideration of the need for further study; 

(3) proposed solutions to problems stated in specific language in amendment form to Conference documents; and

(4) practical, realistic, and specific recommendations for both regulations and test methods to provide for proper 

enforcement if a proposal involves a new area of weights and measures activity.

When proposals are to modify or add requirements to existing publications, such as Handbook 44, the proposal 

should:

(i) Identify the pertinent portion, section, and paragraph of the existing publication that would be changed 

(e.g., Sec. 1.10. General Code, paragraph G-A.1. Commercial and Law-Enforcement Equipment.).

(ii) Provide evidence of consistency with other NCWM publications such as with other specific device code 

sections.

(iii) Provide evidence of consistency with Federal laws and regulations (e.g., USDA)

(iv) Relay the positions of businesses, industries, or trade associations affected by the proposal including 

supporting and opposing points of view.
Introduction

3

H. Exceptions to Policy for Submission of Issues to a Committee Agenda; Submission of “Priority” Issues.

The Committee will use the following criteria to evaluate issues that have not been approved by a regional association, 

but has been received by the November 1 deadline. If an issue is received after the November 1 deadline, it will be 

included on an agenda if the Committee determines that it is a national “Priority.” 

Criteria for Inclusion in the Committee’s Agenda when no Regional Association has Approved the Issues.

(1) Issues must have significant legal impact on weights and measures laws and/or regulations involving:

(a) court cases/attorney general opinions; or

(b) pre-emption by Federal statute or regulation; or

(c) conflict with international standards; or

(d) relationship to laws or regulations of an urgent nature which could affect health and safety.

(2) The Committee may contact parties that are potentially affected by a issue (e.g., trade associations, industry, and 

consumer groups) for comments. The Committee may consider these comments and any other information in 

determining if the issue should be included on its agenda.

(3) When the Committee determines that it should consider an issue as a “Priority” (using the criteria in (1), the issue 

will be handled in the following manner:

a. A “Priority” issue received prior to the Interim Meeting may be added to the Interim Meeting agenda by 

majority vote of the Committee.

b. A “Priority” issue received after the Interim Meeting may be added to the Committee’s Annual Meeting 

agenda as: (i) a discussion issue by majority vote of the Committee, or (ii) as a voting item by majority vote of 

the Committee and the NCWM Board of Directors.

I. Committee Agenda.

a. The Committee will review issues that have been submitted and selected by majority vote to be included on its 

agenda. The Committee will only include those issues that have been (1) approved by at least one of the regional 

associations; or (2) forwarded by other committees, subcommittees, NTETC Sectors, task forces, or work groups, or 

those issues that meet the criteria in Section H, Exceptions to Policy.

b. The Committee will publish an agenda which identifies the issues to be discussed during the Interim Meetings. 

This agenda shall be distributed to members approximately 30 days prior to the meetings. The agenda will be 

provided upon request to all other interested parties.

(Amended 1998)

J. Interim Meeting.

a. The Committee shall hold public hearings at the Interim Meeting for the purpose of discussing and taking 

comments on all issues on its agenda.

b. Upon request, the Committee will provide the opportunity for presentations by government officials, industry 

representatives, consumer groups, or other interested parties during the Interim Meeting. Requests to make presentations must be received by the Committee Chairman or Technical Advisor at least two weeks prior to the start of the 

meetings.
Introduction

4

K. Interim Meeting Report.

a. Issues under consideration by the Committee and upon which it offers comments or recommendations for 

Conference action during the Annual Meetings, will be included in the Committee’s Interim Reports published in the 

Annual Meeting, Program and Committee Reports. 

b. The Annual Meeting Program and Committee Reports will be prepared and distributed to Conference members 

approximately 3 months prior to the NCWM Annual Meeting.

L. Classifications for Agenda Items.

At the Interim Meeting, the Committee can classify items for voting by the NCWM membership (indicated with a “V” 

after the item number in the agenda or prior to the voting session). The Committee may also decide to carry issues over 

as “Informational” items for further study, comment, and development (indicated with an “I” after the item number). 

Items marked “W” in the agenda have been withdrawn from consideration.

M. Developing Issues.

At the 1998 Annual Meeting, the NCWM established a process for disseminating information on issues which may have 

merit but are insufficiently developed for Committee action. Past practice for handling these issues had been to either 

“carry” them forward as informational issues or withdraw them. Conference members felt that carrying undeveloped 

information items drained NCWM resources, but they also believed that withdrawn items were often prematurely 

discarded despite the valuable work that had gone into developing the issue. The NCWM was also interested in providing 

a mechanism to inform parties about issues that are developing in different localities or in the regional associations. 

The NCWM established a new “Developing” designation to allow the Committees to notify the submitter of the issue, 

that, while it may have merit, it may not be adequately developed for action at the national level. The NCWM agreed that 

“Developing” issues should be submitted by the regional associations with a recommendation that they be presented as 

“D” issues on the national agenda. The Committees will present “D” issues in list format at the end of their reports and 

include a point of contact (including the name and telephone number of the submitter) so that interested parties can obtain 

additional information. No comments will be taken on a “Developing” issue, unless the Committee agrees to receive the 

new information in advance of the hearing. In these cases, the Chairman will announce in advance that an issue will be 

discussed in the session. The use of this “D” designator is seen as an issue management tool, as well as a way to keep the 

membership informed of emerging issues.

N. Comments on Interim Reports.

a. Weights and measures officials, industry representatives, and all other parties are encouraged to submit written 

comments on issues in the Committees' Interim Reports. 

b. All comments on the Interim Meeting Reports must be submitted to the Committee, along with a copy to the 

Executive Secretary, no later than 1 month preceding the opening of the Annual Meeting.

O. Annual Meeting.

a. The Committee will hold a public hearing at the Annual Meeting to discuss issues on its agenda.

b. Those who want to speak on an issue during the public hearings should request time from the Committee 

Chairman. Time limitations on presentations, the discussion of a question, or amendments may be imposed by the 

Committee Chairman.

P. Final Committee Reports and Conference Action.

a. Following the public hearings, the Committee will prepare its final report for action by the voting membership of 

the Conference. Prior to the session during which it will be acted on, copies of each final report will be provided for 

study.
Introduction

5

b. The Chairman of the Committee will present the final report of the Committee to the Conference body. A vote 

will be taken on issues, proposals, or sections in the report as circumstances require. The Conference will vote on the 

entire final report as presented in accordance with established Conference voting procedures. Parliamentary procedure according to Roberts Rules of Order as amended by NCWM Publication No. 1, Bylaws, will be adhered to in 

the presentation of and action on Standing Committee reports.

(Amended 1998)

Q. System of Paragraph Designation. - In order that technical requirements of a similar nature, or those directed to a 

single characteristic, may be grouped together in an orderly fashion, and to facilitate the location of individual 

requirements, the paragraphs of each code are divided into sections. Each section is designated by a letter and a name, 

and each subsection is given a letter-number designation and a side title.

The letter that appears first in a paragraph designation has a specific meaning, as follows:

G. The letter G is a prefix and indicates that the requirement is part of the General Code.

A. Application. These paragraphs pertain to the application of the requirements of a code.

S. Specification. These paragraphs relate to the design of equipment. Specification paragraphs are directed 

particularly to manufacturers of devices.

N. Note. These paragraphs apply to the official testing of devices.

T. Tolerance. Tolerances are performance requirements. They fix the limit of allowable error or departure 

from true performance or value.

Sensitivity. The sensitivity requirements, applicable only to nonautomatic-indicating scales, are 

performance requirements and are lettered with a T.

UR. User Requirement. These paragraphs are directed particularly to the owner and operator of a device.

User requirements apply to the selection, installation, use, and maintenance of devices.

D. Definitions of Terms. A definitions section appears in Appendix D to provide the definition of the terms 

having a special meaning.

The numerical designation after a letter follows the decimal system of paragraph identification that fixes both the 

relationship and the limitation of the requirements of the paragraph. For example, in the Scales Code, under 

Specifications, the following numerical designations occur:

S. Specifications

S.1. Design of Indicating and Recording Elements and of Recorded Representations.

S.1.1. Zero Indication.

S.1.1.1. Digital Indicating Elements.

S.1.1.2. No-Load Reference Value.

S.1.2. Value of Scale Division Units.

S.1.2.1. Weight Units.

S.1.3. Graduations.

S.1.3.1. Length.

S.1.3.2. Width.

 S.1.3.3. Clear Space Between Graduations.

In this example, Paragraphs S.1.1., S.1.2., and S.1.3. are directed and limited to paragraph S.1., which pertains to the 

design of indicating and recording elements and of recorded representations. Paragraphs S.1.1.1. and S.1.1.2. are directly 
Introduction

6

related to each other, but they are limited to the design of zero indication. Likewise, paragraphs S.1.3.1., S.1.3.2., and 

S.1.3.3. are directly related to each other, but they are limited to the design of graduations.

This handbook conforms to the concept of primary use of SI (metric) measurements recommended in the Omnibus Trade 

and Competitiveness Act of 1988 by citing SI metric units before inch-pound units where both units appear together and 

placing separate sections containing requirements for metric units before corresponding sections containing requirements 

for customary units. Occasionally, a paragraph or table carries the suffix "M" because the requirement in SI units is 

shown as a separate statement, rather than combined with the inch-pound units. In these few instances, separate 

requirements were judged to be more easily understood than attempting to combine SI and inch-pound units in a single 

paragraph or table. In some cases, however, trade practice is currently restricted to the use of customary units; therefore, 

some requirements in this Handbook will continue to specify only customary units until the Conference achieves a broad 

consensus on the permitted metric units. 

R. Classification of Requirements. - The classification of requirements into "retroactive" and "nonretroactive" status is 

made in order that the requirements may be put into force and effect without unnecessary hardship and without wholesale 

condemnation of apparatus. Retroactive requirements are enforceable with respect to all equipment and are printed in 

upright roman type. Nonretroactive requirements are those that, while clearly desirable, are not so vital that they should 

at once be enforced with respect to all apparatus. Nonretroactive requirements are printed in italic type.

It is not expected that, after their promulgation in a given jurisdiction, nonretroactive requirements will always remain 

nonretroactive. It is entirely proper that a weights and measures official, following a careful analysis of existing 

conditions, fix reasonable periods for the continuance of the nonretroactive application of particular requirements, after 

which such requirements will become retroactive. These periods should be long enough to avoid undue hardship to the 

owners or operators of apparatus and, in the case of some requirements, should approximate the average useful life of the 

apparatus in question. 

In order that all interested parties may have timely and ample notice of impending changes in the status of requirements, 

the following procedure is suggested for the official who plans to change the classification of requirements. If sufficient 

data are available to make such action feasible, publish in combination with the codes themselves the date or dates at 

which nonretroactive requirements are to become retroactive. In other cases, give equally effective notice at the earliest 

practicable date.

A nonretroactive requirement, in italic type, will indicate the year from which it should be enforced and, in some cases, 

the date the requirement shall be changed to retroactive status. For example, [Nonretroactive as of 1978 and to become 

retroactive on January 1, 1985]. As a general rule, each nonretroactive requirement is reviewed after it has been in effect 

for 10 years to determine the appropriateness of its nonretroactive status.

S. Using the Handbook. - Handbook 44 is designed to be a working tool for the weights and measures official, the 

equipment manufacturer, installer, and repairman. The section on Fundamental Considerations (Appendix A) should be 

studied until its contents are well known. The General Code, with general requirements pertaining to all devices, 

obviously must be well known to a user of the Handbook. The makeup of the specific codes, the order of paragraph 

presentation, and particularly paragraph designation are worthy of careful study.

It is not deemed advisable for a user to attempt to commit to memory tolerances or tolerance tables, even though these are 

used frequently. For the Handbook to serve its purpose, it should be available when any of its requirements are to be 

applied. Direct reference is the only sure way to apply a requirement properly and to check whether other requirements 

may be applicable.

This Handbook supplies criteria which enables the inspector to determine the suitability, accuracy, and repetitive 

consistency of a weighing or measuring device, both in the laboratory and in the field. However, not all code sections can 

be appropriately applied in both settings. Since some sections are designed to be applied specifically to tests performed 

under laboratory conditions, it would be impractical or unrealistic to apply them to field tests. Not all tests described in

the “Notes” section of the Handbook are required to be performed in the field as an official test. An inspector may 

officially approve or reject a device which has been tested in accordance with those sections applicable to the type of test 

being conducted.

(Paragraph added 1996)
Introduction

7

NCWM Form 15

Proposal to a Standing Committee

Committee: ______________________

Date: Regional Association: 

Name/Address of Contact Person

Phone:

Fax:

email:

Regional Actions: (votes for and against)

Please Attach Additional Pages and Information as Needed

Proposal: (Proposed solutions to problems stated in specific language in amendment form to handbooks, if a 

proposal involves a new area of weights and measures activity, the recommendations for both regulations and test 

methods for proper enforcement must be provided.)

Problem/Justification: (Include a concise statement of the issue or problem outlining the purpose and national need 

for its consideration.)

Other Contacts: (Provide position statements, comments, etc. from names and addresses of individuals, firms, 

manufacturers, and/or trade associations included in developing the proposal.)

Other Reasons For: (If none, please indicate none have emerged.)

Other Reasons Against:

Additional Considerations: (provide cost estimates and state the anticipated benefits for all parties or indicate how 

the proposal may affect other requirements, programs, etc.) 

Attachments: (list the accompanying documents, data, 

studies etc.) 

Suggested Action: (Be specific on what action the 

committee should take on the issue.) 

Recommend NCWM  Adoption  Withdraw

 Developing Issue 

 Informational Issue 

 Other (Please describe)

1.10. General Code

1-1

Sec. 1.10. General Code

G-A. Application

G-A.1. Commercial and Law-Enforcement Equipment. - These specifications, tolerances, and other technical 

requirements apply as follows:

(a) To commercial weighing and measuring equipment; that is, to weights and measures and weighing and 

measuring devices commercially used or employed in establishing the size, quantity, extent, area, or measurement of quantities, things, produce, or articles for distribution or consumption, purchased, offered, or 

submitted for sale, hire, or award, or in computing any basic charge or payment for services rendered on the 

basis of weight or measure.

(b) To any accessory attached to or used in connection with a commercial weighing or measuring device when such 

accessory is so designed that its operation affects the accuracy of the device.

(c) To weighing and measuring equipment in official use for the enforcement of law or for the collection of 

statistical information by government agencies.

(These requirements should be used as a guide by the weights and measures official when, upon request, courtesy 

examinations of noncommercial equipment are made.)

G-A.2. Code Application. - This General Code shall apply to all classes of devices as covered in the specific codes. The 

specific code requirements supersede General Code requirements in all cases of conflict. 

(Amended 1972)

G-A.3. Special and Unclassified Equipment. - Insofar as they are clearly appropriate, the requirements and provisions 

of the General Code and of specific codes apply to equipment failing, by reason of special design or otherwise, to fall 

clearly within one of the particular equipment classes for which separate codes have been established. With respect to 

such equipment, code requirements and provisions shall be applied with due regard to the design, intended purpose, and 

conditions of use of the equipment.

G-A.4. Metric Equipment. - Employment of the weights and measures of the metric system is lawful throughout the 

United States. These specifications, tolerances, and other requirements shall not be understood or construed as in any 

way prohibiting the manufacture, sale, or use of equipment designed to give results in terms of metric units. The specific 

provisions of these requirements and the principles upon which the requirements are based shall be applied to metric 

equipment insofar as appropriate and practicable. The tolerances on metric equipment, when not specified herein, shall 

be equivalent to those specified for similar equipment constructed or graduated in the inch-pound system.

G-A.5. Retroactive Requirements. - "Retroactive" requirements are enforceable with respect to all equipment. 

Retroactive requirements are printed herein in upright roman type.

G-A.6. Nonretroactive Requirements. - "Nonretroactive" requirements are enforceable after the effective date for:

(a) devices manufactured within a State after the effective date;

(b) both new and used devices brought into a State after the effective date; and

(c) devices used in noncommercial applications which are placed into commercial use after the effective date.

Nonretroactive requirements are not enforceable with respect to devices that are in commercial service in the State as of 

the effective date or to new equipment in the stock of a manufacturer or a dealer in the State as of the effective date.

(Nonretroactive requirements are printed in italic type.)

(Amended 1989)
1.10. General Code

1-2

G-A.7. Effective Enforcement Dates of Code Requirements. - Unless otherwise specified, each new or amended code 

requirement shall not be subject to enforcement prior to January 1 of the year following the adoption by the National 

Conference on Weights and Measures and publication by the National Institute of Standards and Technology.

G-S. Specifications

G-S.1. Identification. - All equipment, except weights and separate parts necessary to the measurement process but not 

having any metrological effect, shall be clearly and permanently marked for the purposes of identification with the 

following information:

(a) the name, initials, or trademark of the manufacturer or distributor;

(b) a model designation that positively identifies the pattern or design of the device;

(c) the model designation shall be prefaced by the term "Model," "Type," or "Pattern." These terms may be 

followed by the term "Number" or an abbreviation of that word. The abbreviation for the word "Number" shall, 

as a minimum, begin with the letter "N" (e.g., No or No.). The abbreviation for the word “Model” shall be 

“Mod” or “Mod.”

[Nonretroactive January 1, 2003]

(Added 2000) (Amended 2001)

[Note: Prefix lettering may be initial capitals, all capitals or all lower case.]

(d) except for equipment with no moving or electronic component parts, a nonrepetitive serial number; 

[Nonretroactive as of January 1, 1968]

(e) the serial number shall be prefaced by words, an abbreviation, or a symbol, that clearly identifies the number as 

the required serial number; and

[Nonretroactive as of January 1, 1986]

(f) the serial number shall be prefaced by the words "Serial Number" or an abbreviation of that term. 

Abbreviations for the word "Serial" shall, as a minimum, begin with the letter "S," and abbreviations for the 

word "Number" shall, as a minimum, begin with the letter "N" (e.g., S/N, SN, Ser. No, and S No.).

[Nonretroactive as of January 1, 2001]

(g) For devices that have an NTEP Certificate of Conformance (CC) Number or a corresponding CC addendum 

number, the NTEP CC shall be prefaced by the terms "NTEP CC," "CC," or "Approval." These terms may be 

followed by the term "Number" or an abbreviation of that word. The abbreviation for the word "Number" shall, 

as a minimum, begin with the letter "N" (e.g., No or No.)

[Nonretroactive as of January 1, 2003]

The required information shall be so located that it is readily observable without the necessity of the disassembly of a part 

requiring the use of any means separate from the device.

(Amended 1985, 1991, 1999 and 2000)

G-S.1.1. Remanufactured Devices and Remanufactured Main Elements. - All remanufactured devices and 

remanufactured main elements shall be clearly and permanently marked for the purposes of identification with the 

following information:

(a) the name, initials, or trademark of the last remanufacturer or distributor;

(b) the remanufacturer's or distributor's model designation if different than the original model designation.

[Nonretroactive as of January 1, 2002] 

(Added 2001)

Note: Definitions for “manufactured device,” “repaired device,” and “repaired element” are also included (along 

with definitions for “remanufactured device” and “remanufactured element”) in Appendix D, Definitions.
1.10. General Code

1-3

G-S.2. Facilitation of Fraud. - All equipment and all mechanisms and devices attached thereto or used in connection 

therewith shall be so constructed, assembled, and installed for use such that they do not facilitate the perpetration of fraud.

G-S.3. Permanence. - All equipment shall be of such materials, design, and construction as to make it probable that, 

under normal service conditions:

(a) accuracy will be maintained,

(b) operating parts will continue to function as intended, and

(c) adjustments will remain reasonably permanent.

Undue stresses, deflections, or distortions of parts shall not occur to the extent that accuracy or permanence is 

detrimentally affected.

G-S.4. Interchange or Reversal of Parts. - Parts of a device that may readily be interchanged or reversed in the course 

of field assembly or of normal usage shall be:

(a) so constructed that their interchange or reversal will not affect the performance of the device, or

(b) so marked as to show their proper positions.

G-S.5. Indicating and Recording Elements.

G-S.5.1. General. - All weighing and measuring devices shall be provided with indicating or recording elements 

appropriate in design and adequate in amount. Primary indications and recorded representations shall be clear, 

definite, accurate, and easily read under any conditions of normal operation of the device.

G-S.5.2. Graduations, Indications, and Recorded Representations.

G-S.5.2.1. Analog Indication and Representation. - Graduations and a suitable indicator shall be provided in 

connection with indications designed to advance continuously.

G-S.5.2.2. Digital Indication and Representation. - Digital elements shall be so designed that:

(a) All digital values of like value in a system agree with one another.

(b) A digital value coincides with its associated analog value to the nearest minimum graduation.

(c) A digital value "rounds off" to the nearest minimum unit that can be indicated or recorded.

(d) A digital zero indication includes the display of a zero for all places that are displayed to the right of 

the decimal point and at least one place to the left. When no decimal values are displayed, a zero shall 

be displayed for each place of the displayed scale division.

[Nonretroactive as of January 1, 1986.]

(Amended 1973 and 1985)

G-S.5.2.3. Size and Character. - In any series of graduations, indications, or recorded representations,

corresponding graduations and units shall be uniform in size and character. Graduations, indications, or 

recorded representations that are subordinate to, or of a lesser value than others with which they are associated, 

shall be appropriately portrayed or designated. [Made retroactive as of January 1, 1975.]

G-S.5.2.4. Values. - If graduations, indications, or recorded representations are intended to have specific values, 

these shall be adequately defined by a sufficient number of figures, words, symbols, or combinations thereof, 

uniformly placed with reference to the graduations, indications, or recorded representations and as close thereto 

as practicable, but not so positioned as to interfere with the accuracy of reading.
1.10. General Code

1-4

G-S.5.2.5. Permanence. - Graduations, indications, or recorded representations and their defining figures, 

words, and symbols shall be of such character that they will not tend easily to become obliterated or illegible.

G-S.5.3. Values of Graduated Intervals or Increments. - In any series of graduations, indications, or recorded 

representations, the values of the graduated intervals or increments shall be uniform throughout the series.

G-S.5.3.1. On Devices That Indicate or Record in More Than One Unit. - On devices designed to indicate 

or record in more than one unit of measurement, the values indicated and recorded shall be identified with an 

appropriate word, symbol, or abbreviation.

[Made retroactive 1990] (Amended 1978 and 1986)

G-S.5.4. Repeatability of Indications. - A device shall be capable of repeating, within prescribed tolerances, its 

indications and recorded representations. This requirement shall be met irrespective of repeated manipulation of any 

element of the device in a manner approximating normal usage (including displacement of the indicating elements to 

the full extent allowed by the construction of the device and repeated operation of a locking or relieving mechanism) 

and of the repeated performance of steps or operations that are embraced in the testing procedure.

G-S.5.5. Money Values, Mathematical Agreement. - Any recorded money value and any digital money-value 

indication on a computing-type weighing or measuring device used in retail trade shall be in mathematical agreement 

with its associated quantity representation or indication to the nearest 1 cent of money value. This does not apply to 

auxiliary digital indications intended for the operator’s use only, when these indications are obtained from existing 

analog customer indications that meet this requirement.

(Amended 1973)

G-S.5.6. Recorded Representations. - Insofar as they are appropriate, the requirements for indicating and recording 

elements shall also apply to recorded representations. All recorded values shall be printed digitally.

[Made retroactive 1990] (Amended 1975)

G-S.5.6.1. Recorded Representation of Metric Units on Equipment with Limited Character Sets. - The 

appropriate defining symbols are shown in Table 1.

(Added 1977)

G-S.5.7. Magnified Graduations and Indications. - All requirements for graduations and indications apply to a 

series of graduations and an indicator magnified by an optical system or as magnified and projected on a screen. 

G-S.6. Marking Operational Controls, Indications, and Features. - All operational controls, indications, and features, 

including switches, lights, displays, push buttons, and other means, shall be clearly and definitely identified. The use of 

approved pictograms or symbols shall be acceptable. 

[Nonretroactive as of January 1, 1977]

(Amended 1978 and 1995)

G-S.7. Lettering. - All required markings and instructions shall be distinct and easily readable and shall be of such 

character that they will not tend to become obliterated or illegible.

G-S.8. Provision for Sealing Electronic Adjustable Components. - A device shall be designed with provision(s) for 

applying a security seal that must be broken, or for using other approved means of providing security (e.g., data change 

audit trail available at the time of inspection), before any change that detrimentally affects the metrological integrity of 

the device can be made to any electronic mechanism.

[Nonretroactive as of January 1, 1990]

A device may be fitted with an automatic or a semi-automatic calibration mechanism. This mechanism shall be 

incorporated inside the device. After sealing, neither the mechanism nor the calibration process shall facilitate fraud.

(Added 1985)(Amended 1989 and 1993)
1.10. General Code

1-5

Table 1.

Representation of Units

Representation

Form I Form II

Name of Unit

International 

symbol (common 

use symbol)

(double case) (single case lower) (single case upper)

Base SI units

meter m m m M

kilogram kg kg kg KG

Derived SI units

newton N N n N

pascal Pa Pa pa PA

watt W W w W

volt V V v V

degree Celsius °C °C °c °C

Other units

liter l or L L l L

gram g g g G

metric ton t t tne TNE

bar bar bar bar BAR

G-N. Notes

G-N.1. Conflict of Laws and Regulations. - If any particular provisions of these specifications, tolerances, and other 

requirements are found to conflict with existing State laws, or with existing regulations or local ordinances relating to 

health, safety, or fire prevention, the enforcement of such provisions shall be suspended until conflicting requirements can 

be harmonized. Such suspension shall not affect the validity or enforcement of the remaining provisions of these specifications, tolerances, and other requirements.

G-N.2. Testing With Nonassociated Equipment. - Tests to determine conditions, such as radio frequency interference 

(RFI), that may adversely affect the performance of a device shall be conducted with equipment and under conditions that 

are usual and customary with respect to the location and use of the device.

(Added 1976)

G-T. Tolerances

G-T.1. Acceptance Tolerances. - Acceptance tolerances shall apply to:

(a) equipment to be put into commercial use for the first time;
1.10. General Code

1-6

(b) equipment that has been placed in commercial service within the preceding 30 days and is being officially tested 

for the first time;

(c) equipment that has been returned to commercial service following official rejection for failure to conform to performance requirements and is being officially tested for the first time within 30 days after corrective service;

(d) equipment that is being officially tested for the first time within 30 days after major reconditioning or overhaul; 

and

(e) equipment undergoing type evaluation.

(Amended 1989)

G-T.2. Maintenance Tolerances. - Maintenance tolerances shall apply to equipment in actual use, except as provided in 

G-T.1.

G-T.3. Application. - Tolerances "in excess" and tolerances "in deficiency" shall apply to errors in excess and to errors 

in deficiency, respectively. Tolerances "on overregistration" and tolerances "on underregistration" shall apply to errors in 

the direction of overregistration and of underregistration, respectively. (See Appendix D, Definitions.)

G-T.4. For Intermediate Values. - For a capacity, indication, load, value, etc., intermediate between two capacities, 

indications, loads, values, etc., listed in a table of tolerances, the tolerances prescribed for the lower capacity, indication, 

load, value, etc., shall be applied.

G-UR. User Requirements

G-UR.1. Selection Requirements.

G-UR.1.1. Suitability of Equipment. - Commercial equipment shall be suitable for the service in which it is used 

with respect to elements of its design, including but not limited to its weighing capacity (for weighing devices), its

computing capability (for computing devices), its rate of flow (for liquid-measuring devices), the character, number, 

size, and location of its indicating or recording elements, and the value of its smallest unit and unit prices.

(Amended 1974)

G-UR.1.2. Environment. - Equipment shall be suitable for the environment in which it is used including, but not 

limited to, the effects of wind, weather, and RFI.

(Added 1976)

G-UR.1.3. Liquid-Measuring Devices. - To be suitable for its application, the minimum delivery for liquidmeasuring devices shall be no less than 100 divisions, except that the minimum delivery for retail analog devices 

shall be no less than 10 divisions. Maximum division values and tolerances are stated in the specific codes.

(Added 1995)

G-UR.2. Installation Requirements.

G-UR.2.1. Installation. - A device shall be installed in accordance with the manufacturer's instructions, including 

any instructions marked on the device. A device installed in a fixed location shall be installed so that neither its 

operation nor its performance will be adversely affected by any characteristic of the foundation, supports, or any 

other detail of the installation.

G-UR.2.1.1. Visibility of Identification. - Equipment shall be installed in such a manner that all required 

markings are readily observable.

(Added 1978)

G-UR.2.2. Installation of Indicating or Recording Element. - A device shall be so installed that there is no 

obstruction between a primary indicating or recording element and the weighing or measuring element; otherwise 

there shall be convenient and permanently installed means for direct communication, oral or visual, between an 

individual located at a primary indicating or recording element and an individual located at the weighing or 

measuring element. [See also G-UR.3.3.]
1.10. General Code

1-7

G-UR.2.3. Accessibility for Inspection, Testing, and Sealing Purposes. - A device shall be located, or such facilities for normal access thereto shall be provided, to permit:

(a) inspecting and testing the device;

(b) inspecting and applying security seals to the device; and

(c) readily bringing the testing equipment of the weights and measures official to the device by customary 

means and in the amount and size deemed necessary by such official for the proper conduct of the test.

Otherwise, it shall be the responsibility of the device owner or operator to supply such special facilities, including 

such labor as may be needed to inspect, test, and seal the device, and to transport the testing equipment to and from 

the device, as required by the weights and measures official.

(Amended 1991)

G-UR.3. Use Requirements.

G-UR.3.1. Method of Operation. - Equipment shall be operated only in the manner that is obviously indicated by 

its construction or that is indicated by instructions on the equipment.

G-UR.3.2. Associated and Nonassociated Equipment. - A device shall meet all performance requirements when 

associated or nonassociated equipment is operated in its usual and customary manner and location.

(Added 1976)

G-UR.3.3. Position of Equipment. - A device or system equipped with a primary indicating element and used in 

direct sales, except for prescription scales, shall be positioned so that its indications may be accurately read and the 

weighing or measuring operation may be observed from some reasonable "customer" and “operator” position. The 

permissible distance between the equipment and a reasonable customer and operator position shall be determined in 

each case upon the basis of the individual circumstances, particularly the size and character of the indicating element.

(Amended 1974 and 1998)

G-UR.3.4. Responsibility, Money-Operated Devices. - Money-operated devices other than parking meters shall 

have clearly and conspicuously displayed thereon, or immediately adjacent thereto, adequate information detailing 

the method for the return of monies paid when the product or service cannot be obtained. This information shall 

include the name, address, and phone number of the local responsible party for the device. This requirement does not 

apply to devices at locations where employees are present and responsible for resolving any monetary discrepancies 

for the customer.

(Amended 1977 and 1993)

G-UR.4. Maintenance Requirements.

G-UR.4.1. Maintenance of Equipment. - All equipment in service and all mechanisms and devices attached thereto 

or used in connection therewith shall be continuously maintained in proper operating condition throughout the period 

of such service. Equipment in service at a single place of business found to be in error predominantly in a direction 

favorable to the device user shall not be considered "maintained in a proper operating condition."

(Amended 1973 and 1991)

G-UR.4.2. Abnormal Performance. - Unstable indications or other abnormal equipment performance observed 

during operation shall be corrected and, if necessary, brought to the attention of competent service personnel.

(Added 1976)

G-UR.4.3. Use of Adjustments. - Weighing elements and measuring elements that are adjustable shall be adjusted 

only to correct those conditions that such elements are designed to control, and shall not be adjusted to compensate 

for defective or abnormal installation or accessories or for badly worn or otherwise defective parts of the assembly. 

Any faulty installation conditions shall be corrected, and any defective parts shall be renewed or suitably repaired, 

before adjustments are undertaken. Whenever equipment is adjusted, the adjustments shall be so made as to bring 

performance errors as close as practicable to zero value.
1.10. General Code

1-8

G-UR.4.4. Assistance in Testing Operations. - If the design, construction, or location of any device is such as to 

require a testing procedure involving special equipment or accessories or an abnormal amount of labor, such 

equipment, accessories, and labor shall be supplied by the owner or operator of the device as required by the weights 

and measures official.

G-UR.4.5. Security Seal. - A security seal shall be appropriately affixed to any adjustment mechanism designed to 

be sealed.

G-UR.4.6. Testing Devices at a Central Location. 

(a) When devices in commercial service require special test facilities, or must be removed from service for 

testing, or are routinely transported for the purpose of use (e.g., vehicle-mounted devices and devices used 

in multiple locations), the official with statutory authority may require that the devices be brought to a 

central location for testing. The dealer or owner of these devices shall provide transportation of the devices 

to and from the test location.

(b) When the request for removal and delivery to a central test location involves devices used in submetering 

(e.g., electric, hydrocarbon vapor, or water meters), the owner or operator shall not interrupt the utility 

service to the customer or tenant except for the removal and replacement of the device. Provisions shall be 

made by the owner or operator to minimize inconvenience to the customer or tenant. All replacement or 

temporary meters shall be tested and sealed by a weights and measures official or bear a current, valid 

approval seal prior to use.

(Added 1994)
2-1 

Section 2 

Page 

2.20. Scales 2-3 

2.21. Belt-Conveyor Scale Systems 2-41 

2.22. Automatic Bulk Weighing Systems 2-51 

2.23. Weights 2-57 

2.24. Automatic Weighing Systems - Tentative Code 2-61 
2-2 
2.20. Scales 

2-3 

Sec. 2.20. Scales 

A. Application 

A.1. General. - This code applies to all types of weighing devices other than automatic bulk-weighing systems, 

belt-conveyor scales, and automatic weighing systems. The code comprises requirements that generally apply to all 

weighing devices, and specific requirements that are applicable only to certain types of weighing devices. 

(Amended 1972 and 1983) 

A.2. Wheel-Load Weighers, Portable Axle-Load Weighers, and Axle-Load Scales. - The requirements for 

wheel-load weighers, portable axle-load weighers, and axle-load scales apply only to such scales in official use for the 

enforcement of traffic and highway laws or for the collection of statistical information by government agencies. 

A.3. Also see General Code requirements. 

S. Specifications 

S.1. Design of Indicating and Recording Elements and of Recorded Representations.

S.1.1. Zero Indication.

(a) On a scale equipped with indicating or recording elements, provision shall be made to either indicate or 

record a zero-balance condition. 

(b) On an automatic-indicating scale or balance indicator, provision shall be made to indicate or record an 

out-of-balance condition on both sides of zero. 

(c) A zero-balance condition may be indicated by other than a continuous digital zero indication, provided that 

an effective automatic means is provided to inhibit a weighing operation or to return to a continuous digital 

indication when the scale is in an out-of-balance condition. 

(Added 1987) (Amended 1987 and 1993) 

S.1.1.1. Digital Indicating Elements.

(a) A digital zero indication shall represent a balance condition that is within ±1⁄2 the value of the scale 

division. 

(b) A digital indicating device shall either automatically maintain a "center-of-zero" condition to ±1⁄4 scale

division or less, or have an auxiliary or supplemental "center-of-zero" indicator that defines a 

zero-balance condition to ±1⁄4 of a scale division or less. 

[Nonretroactive as of January 1, 1993]

(Amended 1992) 

S.1.1.2. No-Load Reference Value. - On a single draft manually operated receiving hopper scale installed 

below grade, used to receive grain, and utilizing a no-load reference value, provision shall be made to indicate 

and record the no-load reference value prior to the gross load value. 

(Added 1983) 

S.1.2. Value of Scale Division Units. - Except for batching scales and weighing systems used exclusively for 

weighing in predetermined amounts, the value of a scale division "d" expressed in a unit of weight shall be equal to: 

 

(a) 1, 2, or 5; or 

(b) a decimal multiple or submultiple of 1, 2, or 5; 

(c) a binary submultiple of a specific unit of weight. 
2.20. Scales 

2-4 

Examples: scale divisions may be 0.01, 0.02, 0.05; 0.1, 0.2, or 0.5; 1, 2, or 5; 10, 20, 50, or 100; or, scale 

divisions may be 1/2, 1/4, 1/8, 1/16, etc. 

[Nonretroactive as of January 1, 1986]

S.1.2.1. Weight Units. - Except for postal scales, a digital-indicating scale shall indicate weight values using 

only a single unit of measure. Weight values shall be presented in a decimal format with the value of the scale 

division expressed as 1, 2, or 5, or a decimal multiple or submultiple of 1, 2, or 5. 

[Nonretroactive as of January 1, 1989]

(Added 1987) 

S.1.2.2. Verification Scale Interval. 

S.1.2.2.1. Class I and II Scales and Dynamic Monorail Scales. If e  d, the verification scale interval 

"e" shall be determined by the expression: 

d < e < 10 d 

If the displayed division (d) is less than the verification division (e), then the verification division shall be 

less than or equal to 10 times the displayed division. 

The value of e must satisfy the relationship, e = 10k

 of the unit of measure, where k being a positive or 

negative whole number or zero. This requirement does not apply to a Class I device with d < 1 mg where e 

= 1 mg. If e  d, the value of "d" shall be a decimal submultiple of "e," and the ratio shall not be more than 

10:1. If e  d, and both "e" and "d" are continuously displayed during normal operation, then "d" shall be 

differentiated from "e" by size, shape, color, etc. throughout the range of weights displayed as "d." 

(Added 1999) 

S.1.2.2.2. Class III and IIII. The value of "e" is specified by the manufacturer as marked on the device. 

Except for dynamic monorail scales, "e" must be less than or equal to "d." 

(Added 1999) 

S.1.3. Graduations.

S.1.3.1. Length. - Graduations shall be so varied in length that they may be conveniently read. 

S.1.3.2. Width. - In any series of graduations, the width of a graduation shall in no case be greater than the 

width of the clear space between graduations. The width of main graduations shall be not more than 50 percent 

greater than the width of subordinate graduations. Graduations shall be not less than 0.2 mm (0.008 in) wide. 

S.1.3.3. Clear Space Between Graduations. - The clear space between graduations shall be not less than 

0.5 mm (0.02 in) for graduations representing money values, and not less than 0.75 mm (0.03 in) for other 

graduations. If the graduations are not parallel, the measurement shall be made: 

 (a) along the line of relative movement between the graduations at the end of the indicator, or 

 (b) if the indicator is continuous, at the point of widest separation of the graduations. 

 

S.1.4. Indicators.

S.1.4.1. Symmetry. - The index of an indicator shall be of the same shape as the graduations, at least throughout 

that portion of its length associated with the graduations. 

S.1.4.2. Length. - The index of an indicator shall reach to the finest graduations with which it is used, unless the 

indicator and the graduations are in the same plane, in which case, the distance between the end of the indicator 

and the ends of the graduations, measured along the line of the graduations, shall be not more than 1.0 mm 

(0.04 in). 
2.20. Scales 

2-5 

S.1.4.3. Width. - The width of the index of an indicator in relation to the series of graduations with which it is 

used shall be not greater than: 

 (a) the width of the narrowest graduation,

 [Nonretroactive as of January 1, 2002]

 (b) the width of the clear space between weight graduations, and 

 (c) three-fourths of the width of the clear space between money value graduations. 

When the index of an indicator extends along the entire length of a graduation, that portion of the index of the 

indicator that may be brought into coincidence with the graduation shall be of the same width throughout the 

length of the index that coincides with the graduation. 

S.1.4.4. Clearance. - The clearance between the index of an indicator and the graduations shall in no case be 

more than 1.5 mm (0.06 in). 

S.1.4.5. Parallax. - Parallax effects shall be reduced to the practicable minimum. 

 

S.1.5. Weighbeams.

 

S.1.5.1. Normal Balance Position. - The normal balance position of the weighbeam of a beam scale shall be 

horizontal. 

S.1.5.2. Travel. - The weighbeam of a beam scale shall have equal travel above and below the horizontal. The 

total travel of the weighbeam of a beam scale in a trig loop or between other limiting stops near the weighbeam 

tip shall be not less than the minimum travel shown in Tables 1M and 1. When such limiting stops are not 

provided, the total travel at the weighbeam tip shall be not less than 8 percent of the distance from weighbeam 

fulcrum to the weighbeam tip. 

S.1.5.3. Subdivision. - A subdivided weighbeam bar shall be subdivided by scale division graduations, notches, 

or a combination of both. Graduations on a particular bar shall be of uniform width and perpendicular to the top 

edge of the bar. Notches on a particular bar shall be uniform in shape and dimensions and perpendicular to the 

face of the bar. When a combination of graduations and notches is employed, the graduations shall be positioned 

in relation to the notches to indicate notch values clearly and accurately. 

S.1.5.4. Readability. - A subdivided weighbeam bar shall be so subdivided and marked, and a weighbeam poise 

shall be so constructed, that the weight corresponding to any normal poise position can easily and accurately be 

read directly from the beam, whether or not provision is made for the optional recording of representations of 

weight. 

S.1.5.5. Capacity. - On an automatic-indicating scale having a nominal capacity of 15 kg (30 lb) or less and 

used for direct sales to retail customers: 

Table 1. 

Minimum Travel of Weighbeam of Beam Scale 

Between Limiting Stops 

Distance from weighbeam 

fulcrum to limiting stops 

(inches) 

Minimum travel 

between limiting stops 

(inch) 

12 or less 

12+ to 20, inclusive 

20+ to 40, inclusive 

Over 40 

0.4 

0.5 

0.7 

0.9 

Table 1M. 

Minimum Travel of Weighbeam of Beam Scale 

Between Limiting Stops 

Distance from weighbeam 

fulcrum to limiting stops 

(centimeters) 

Minimum travel between 

 limiting stops 

(millimeter) 

30 or less 

30+ to 50, inclusive 

50+ to 100, inclusive 

Over 100 

10 

13 

18 

23 
2.20. Scales 

2-6 

(a) the capacity of any weighbeam bar shall be a multiple of the reading-face capacity, 

(b) each bar shall be subdivided throughout or shall be subdivided into notched intervals, each equal to the 

reading-face capacity; and 

(c) the value of any turnover poise shall be equal to the reading-face capacity. 

 

S.1.5.6. Poise Stop. - Except on a steelyard with no zero graduation, a shoulder or stop shall be provided on 

each weighbeam bar to prevent a poise from traveling and remaining back of the zero graduation. 

S.1.6. Poises.

S.1.6.1. General. - No part of a poise shall be readily detachable. A locking screw shall be perpendicular to the 

longitudinal axis of the weighbeam and shall not be removable. Except on a steelyard with no zero graduation, a 

poise shall not be readily removable from a weighbeam. The knife edge of a hanging poise shall be hard and 

sharp and so constructed as to allow the poise to swing freely on the bearing surfaces in the weighbeam notches. 

S.1.6.2. Adjusting Material. - The adjusting material in a poise shall be securely enclosed and firmly fixed in 

position; if softer than brass, it shall not be in contact with the weighbeam. 

S.1.6.3. Pawl. - A poise, other than a hanging poise, on a notched weighbeam bar shall have a pawl that will 

seat the poise in a definite and correct position in any notch, wherever in the notch the pawl is placed, and hold it 

there firmly and without appreciable movement. The dimension of the tip of the pawl that is transverse to the 

longitudinal axis of the weighbeam shall be at least equal to the corresponding dimension of the notches. 

S.1.6.4. Reading Edge or Indicator. - The reading edge or indicator of a poise shall be sharply defined, and a 

reading edge shall be parallel to the graduations on the weighbeam. 

S.1.7. Capacity Indication, Weight Ranges, and Unit Weights. - 

(a) Gross Capacity. An indicating or recording element shall not display nor record any values when the total 

platform load (not counting the initial dead load that has been canceled by an initial zero-setting mechanism) 

is in excess of 105 percent of scale capacity. 

(b) Capacity Indication. Electronic computing scales (excluding postal scales and weight classifiers) shall 

neither display nor record a gross or net weight in excess of scale capacity plus 9 d. 

The total value of weight ranges and of unit weights in effect or in place at any time shall automatically be accounted 

for on the reading face and on any recorded representation. 

This requirement does not apply to: (1) single-revolution dial scales, (2) multi-revolution dial scales not equipped 

with unit weights, (3) scales equipped with two or more weighbeams, nor (4) devices that indicate mathematically 

derived totalized values. 

[Nonretroactive as of January 1, 1993]

(Amended 1990, 1992, and 1995) 

S.1.8. Computing Scales.

S.1.8.1.M. Money-Value Graduations, Metric Unit Prices. - The value of the graduated intervals representing 

money values on a computing scale with analog indications shall not exceed: 

(a) 1 cent at all unit prices of 55 cents per kilogram and less; 

(b) 2 cents at unit prices of 56 cents per kilogram through $2.75 per kilogram (special graduations defining 

5-cent intervals may be employed but not in the spaces between regular graduations); 

(c) 5 cents at unit prices of $2.76 per kilogram through $7.50 per kilogram; or 
2.20. Scales 

2-7 

(d) 10 cents at unit prices above $7.50 per kilogram. 

Value figures and graduations shall not be duplicated in any column or row on the graduated chart. (See also 

S.1.8.2.) 

S.1.8.1. Money-Value Graduations, Inch-Pound Unit Prices. - The value of the graduated intervals 

representing money values on a computing scale with analog indications shall not exceed: 

(a) 1 cent at all unit prices of 25 cents per pound and less; 

(b) 2 cents at unit prices of 26 cents per pound through $1.25 per pound (special graduations defining 

5-cent intervals may be employed but not in the spaces between regular graduations); 

(c) 5 cents at unit prices of $1.26 per pound through $3.40 per pound; or 

(d) 10 cents at unit prices above $3.40 per pound. 

Value figures and graduations shall not be duplicated in any column or row on the graduated chart. (See also 

S.1.8.2.) 

S.1.8.2. Money-Value Computation. - A computing scale with analog quantity indications used in retail trade 

may compute and present digital money values to the nearest quantity graduation when the value of the 

minimum graduated interval is 0.005 kg (0.01 lb) or less. (Also see Sec. 1.10; G-S.5.5.) 

S.1.8.3. Customer's Indications. - Weight indications shall be shown on the customer's side of computing 

scales when these are used for direct sales to retail customers. Computing scales equipped on the operator's side 

with digital indications, such as the net weight, unit price, or total price, shall be similarly equipped on the 

customer's side. Unit price displays visible to the customer shall be in terms of single whole units of weight and 

not in common or decimal fractions of the unit. Scales indicating in metric units may indicate price per 

100 grams. 

(Amended 1985 and 1995) 

S.1.8.3.1. Scales that will function as either a normal round off scale or as a weight classifier shall be 

provided with a sealable means for selecting the mode of operation and shall have a clear indication 

(annunciator), adjacent to the weight display on both the operator's and customer's side whenever the scale 

is operating as a weight classifier. 

[Nonretroactive as of January 1, 2001] 

(Added 1999) 

S.1.8.4. Recorded Representations, Point-of-Sale Systems. - The sales information recorded by cash registers 

when interfaced with a weighing element shall contain the following information for items weighed at the 

checkout stand: 

 

(a) the net weight,1

(b) the unit price,1 

(c) the total price, and 

(d) the product class or, in a system equipped with price look-up capability, the product name or code 

number. 

 

1

 Weight values shall be identified by kilogram, kg, grams, g, ounces, oz, pound, lb, or the sign "#." For devices 

interfaced with scales indicating in metric units, the unit price may be expressed in price per 100 grams. 

(Amended 1995) 
2.20. Scales 

2-8 

S.1.9. Prepackaging Scales.

S.1.9.1. Value of the Scale Division. - On a prepackaging scale, the value of the intervals representing weight 

values shall be uniform throughout the entire reading face. The recorded weight values shall be identical with 

those on the indicator. 

S.1.9.2. Label Printer. - A prepackaging scale or a device that produces a printed ticket to be used as the label 

for a package shall print all values digitally and of such size, style of type, and color as to be clear and 

conspicuous on the label. 

S.1.10. Adjustable Components. - An adjustable component such as a pendulum, spring, or potentiometer shall be 

held securely in adjustment and, except for a zero-load balance mechanism, shall be located within the housing of the 

element. 

(Added 1986) 

S.1.11. Provision for Sealing.

(a) Except on Class I scales, provision shall be made for applying a security seal in a manner that requires the 

security seal to be broken before an adjustment can be made to any component affecting the performance of an 

electronic device. 

 [Nonretroactive as of January 1, 1979] 

(b) Except on Class I scales, a device shall be designed with provision(s) for applying a security seal that must be 

broken, or for using other approved means of providing security (e.g., data change audit trail available at the 

time of inspection), before any change that detrimentally affects the metrological integrity of the device can be 

made to any electronic mechanism. 

 [Nonretroactive as of January 1, 1990] 

 (c) Except on Class I scales, audit trails shall use the format set forth in Table S.1.11. 

 [Nonretroactive as of January 1, 1995]

A device may be fitted with an automatic or a semi-automatic calibration mechanism. This mechanism shall be 

incorporated inside the device. After sealing, neither the mechanism nor the calibration process shall facilitate fraud. 

(Amended 1989, 1991 and 1993) 

Table S.1.11. Categories of Device and Methods of Sealing

Categories of Device Method of Sealing

Category 1: No remote configuration capability. Seal by physical seal or two event counters: one for calibration 

parameters and one for configuration parameters. 

Category 2: Remote configuration capability, but 

access is controlled by physical hardware. 

Device shall clearly indicate that it is in the 

remote configuration mode and record such 

message if capable of printing in this mode. 

The hardware enabling access for remote communication must be at 

the device and sealed using a physical seal or two event counters: 

one for calibration parameters and one for configuration 

parameters. 

Category 3: Remote configuration capability 

access may be unlimited or controlled through a 

software switch (e.g., password). 

An event logger is required in the device; it must include an event 

counter (000 to 999), the parameter ID, the date and time of the 

change, and the new value of the parameter. A printed copy of the 

information must be available through the device or through 

another on-site device. The event logger shall have a capacity to 

retain records equal to ten times the number of sealable parameters 

in the device, but not more than 1000 records are required. (Note: 

Does not require 1000 changes to be stored for each parameter.) 

[Nonretroactive as of January 1, 1995]

(Table added 1993) 
2.20. Scales 

2-9 

S.1.12. Manual Gross Weight Entries. - A device shall accept an entry of a manual weight value only when the 

scale is at gross load zero and the scale indication is zero in the gross weights display mode. Recorded manual 

weight entries, except those on labels generated for packages of standard weights, shall identify the weight value as a 

manual weight entry by one of the following terms: "Manual Weight," "Manual Wt," or "MAN WT." The use of a 

symbol to identify multiple manual weight entries on a single document is permitted, provided that the symbol is 

defined on the same page on which the manual weight entries appear and the definition of the symbol is 

automatically printed by the recording element as part of the document. 

 [Nonretroactive as of January 1, 1993]

 (Added 1992)

S.1.13. Vehicle On-Board Weighing Systems: Vehicle in Motion. - When the vehicle is in motion, a vehicle onboard weighing system shall either: 

(a) be accurate; or 

(b) inhibit the weighing operation. 

(Added 1993) 

S.2. Design of Balance, Tare, Level, Damping, and Arresting Mechanisms.

 S.2.1. Zero-Load Adjustment.

S.2.1.1. General. - A scale shall be equipped with means by which the zero-load balance may be adjusted. Any 

loose material used for this purpose shall be enclosed so that it cannot shift in position and alter the balance 

condition of the scale. 

S.2.1.2. Scales used in Direct Sales. - A manual zero-setting mechanism (except on a digital scale with an 

analog zero-adjustment mechanism with a range of not greater than one scale division) shall be operable or 

accessible only by a tool outside of and entirely separate from this mechanism, or it shall be enclosed in a 

cabinet. Except on Class I or II scales, a balance ball shall either meet this requirement or not itself be rotatable. 

A semiautomatic zero-setting mechanism shall be operable or accessible only by a tool outside of and separate 

from this mechanism or it shall be enclosed in a cabinet, or it shall be operable only when the indication is stable 

within: 

(a) plus or minus 3 scale divisions for scales of more than 2000 kg (5000 lb) capacity in service prior to 

January 1, 1981, and for all axle load, railway track, and vehicle scales; or 

(b) plus or minus 1 scale division for all other scales. 

S.2.1.3. Scales Equipped with an Automatic Zero-Setting Mechanism. - Under normal operating conditions 

the maximum load that can be "rezeroed," when either placed on or removed from the platform all at once, shall 

be: 

(a) for bench, counter, and livestock scales: 0.6 scale division; 

(b) for vehicle, axle-load, and railway track scales: 3.0 scale divisions; and 

(c) for all other scales: 1.0 scale division. 

[Nonretroactive and enforceable as of January 1, 1981]

S.2.1.3.1. Automatic Zero-Setting Mechanism on Class III L Devices - Class III L devices equipped with 

automatic zero setting mechanisms shall be designed with a sealable means to allow the automatic zero 

setting to be disabled during the inspection and test of the device. 

[Nonretroactive as of January 1, 2001] 

(Added 1999) 
2.20. Scales 

2-10 

S.2.1.4. Monorail Scales. - On a static monorail scale equipped with digital indications, means shall be 

provided for setting the zero-load balance to within 0.02 percent of scale capacity. On a dynamic monorail 

weighing system, means shall be provided to automatically maintain these conditions. 

(Amended 1999) 

S.2.1.5. Initial Zero-Setting Mechanism. 

(a) Scales of accuracy classes I, II, and III may be equipped with an initial zero-setting device. 

(b) An initial zero-setting mechanism shall not zero a load in excess of 20 percent of the maximum capacity 

of the scale unless tests show that the scale meets all applicable tolerances for any amount of initial load 

compensated by this device within the specified range. 

(Added 1990) 

S.2.1.6. Combined Zero-Tare ("0/T") Key. - Scales not intended to be used in direct sales applications may be 

equipped with a combined zero and tare function key, provided that the device is clearly marked as to how the 

key functions. The device must also be clearly marked on or adjacent to the weight display with the statement 

“Not for Direct Sales.” 

(Added 1998) 

S.2.2. Balance Indicator. - On a balance indicator consisting of two indicating edges, lines, or points, the ends of 

the indicators shall be sharply defined. When the scale is in balance, the ends shall be separated by not more than 1.0 

mm (0.04 in). 

S.2.2.1. Dairy-Product Test, Grain-Test, Prescription, and Class I and II Scales. - Except on digital 

indicating devices, a dairy-product-test, grain-test, prescription, or Class I or II scale shall be equipped with a 

balance indicator. If an indicator and a graduated scale are not in the same plane, the clearance between the 

indicator and the graduations shall be not more than 1.0 mm (0.04 in). 

S.2.2.2. Equal-Arm Scale. - An equal-arm scale shall be equipped with a balance indicator. If the indicator 

and balance graduation are not in the same plane, the clearance between the indicator and the balance 

graduation shall be not more than 1.0 mm (0.04 in).

[Nonretroactive as of January 1, 1989]

(Added 1988) 

S.2.3. Tare. - On any scale (except a monorail scale equipped with digital indications), the value of the tare division 

shall be equal to the value of the scale division.* The tare mechanism shall operate only in a backward direction 

(that is, in a direction of underregistration) with respect to the zero-load balance condition of the scale. A device 

designed to automatically clear any tare value shall also be designed to prevent the automatic clearing of tare until a 

complete transaction has been indicated.* 

(Amended 1985) 

[Note: On a computing scale, this requires the input of a unit price, the display of the unit price, and a computed 

positive total price at a readable equilibrium. Other devices require a complete weighing operation, including tare, 

net, and gross weight determination]* 

[*Nonretroactive as of January 1, 1983] 

S.2.3.1. Monorail Scales Equipped with Digital Indications. - On a static monorail weighing system equipped 

with digital indications, means shall be provided for setting any tare value of less than 5 percent of the scale 

capacity to within 0.02 percent of scale capacity. On a dynamic monorail weighing system, means shall be 

provided to automatically maintain this condition. 

(Amended 1999) 

S.2.4. Level-Indicating Means. - Except for portable wheel-load weighers and portable axle-load scales, a portable 

scale shall be equipped with level-indicating means if its weighing performance is changed by an amount greater than 

the appropriate acceptance tolerance when it is moved from a level position and rebalanced in a position that is out of 
2.20. Scales 

2-11 

level in any upright direction by 5 percent (approximately 3 degrees). The level-indicating means shall be readable 

without removing any scale parts requiring a tool. 

[This requirement is nonretroactive as of January 1, 1986, for prescription, jewelers', and dairy-product-test scales 

and scales marked I and II]

[Note: Portable wheel-load weighers and portable axle-load scales shall be accurate when placed out of level up to 

and including 5 percent (approximately 3 degrees).] 

(Amended 1991) 

S.2.4.1. Vehicle On-Board Weighing Systems. - A vehicle on-board weighing system shall operate within 

tolerance when the weighing system is out of level up to 3 degrees or 5 percent. If the accuracy of the system is 

affected by out-of-level conditions normal to the use of the device, the system shall be equipped with an 

out-of-level sensor that inhibits the weighing operation when the system is out of level to the extent that the 

accuracy limits are exceeded. 

(Added 1992) 

S.2.5. Damping Means. - An automatic-indicating scale and a balance indicator shall be equipped with effective 

means to damp oscillations and to bring the indicating elements quickly to rest. 

S.2.5.1. Digital Indicating Elements. - Digital indicating elements equipped with recording elements shall be 

equipped with effective means to permit the recording of weight values only when the indication is stable within: 

(a) plus or minus 3 scale divisions for scales of more than 2000 kg (5000 lb) capacity in service prior to 

January 1, 1981, hopper (other than grain hopper) scales with a capacity exceeding 22 000 kg 

(50 000 lb), and for all vehicle, axle load, livestock, and railway track scales; 

(b) plus or minus 1 scale division for all other scales. 

The values recorded shall be within applicable tolerances. 

(Amended 1995) 

S.2.5.2. Jewelers', Prescription, and Class I and Class II Scales. - A jewelers', prescription, Class I, or 

Class II scale shall be equipped with appropriate means for arresting the oscillation of the mechanism. 

S.3. Design of Load-Receiving Elements.

S.3.1. Travel of Pans of Equal-Arm Scale. - The travel between limiting stops of the pans of a 

nonautomatic-indicating equal-arm scale not equipped with a balance indicator shall be not less than the 

minimum travel shown in Table 2M and 2. 

Table 2M. 

Minimum Travel of Pans of 

Nonautomatic Indicating Equal-Arm Scale 

Without Balance Indicator 

Nominal capacity 

(kilograms) 

Minimum travel of pans 

(millimeters) 

2 or less 

2+ to 5 inclusive 

5+ to 12, inclusive 

Over 12 

9 

13 

19 

25 

Table 2. 

Minimum Travel of Pans of 

Nonautomatic Indicating Equal-Arm Scale 

Without Balance Indicator 

Nominal capacity 

(pounds) 

Minimum travel of pans 

(inch) 

4 or less 

4+ to 12, inclusive 

12+ to 26, inclusive 

Over 26 

0.35 

0.5 

0.75 

1.0 
2.20. Scales 

2-12 

S.3.2. Drainage. - A load-receiving element intended to receive wet commodities shall be so constructed as to drain 

effectively. 

S.3.3. Scoop Counterbalance. - A scoop on a scale used for direct sales to retail customers shall not be 

counterbalanced by a removable weight. A permanently attached scoop-counterbalance shall indicate clearly on both 

the operator's and customer's sides of the scale whether it is positioned for the scoop to be on or off the scale. 

S.4. Design of Weighing Elements.

S.4.1. Antifriction Means. - Frictional effects shall be reduced to a minimum by suitable antifriction elements. 

Opposing surfaces and points shall be properly shaped, finished, and hardened. A platform scale having a frame 

around the platform shall be equipped with means to prevent interference between platform and frame. 

S.4.2. Adjustable Components. - An adjustable component such as a nose-iron or potentiometer shall be held 

securely in adjustment. The position of a nose-iron on a scale of more than 1000-kg (2000-lb) capacity, as 

determined by the factory adjustment, shall be accurately, clearly, and permanently defined. 

(Amended 1986) 

S.4.3. Multiple Load-Receiving Elements. - Except for mechanical bench and counter scales, a scale with a single 

indicating or recording element, or a combination indicating-recording element, that is coupled to two or more loadreceiving elements with independent weighing systems, shall be provided with means to prohibit the activation of 

any load-receiving element (or elements) not in use, and shall be provided with automatic means to indicate clearly 

and definitely which load-receiving element (or elements) is in use. 

S.5. Design of Weighing Devices, Accuracy Class.

S.5.1. Designation of Accuracy Class. - Weighing devices are divided into accuracy classes and shall be designated 

as I, II, III, III L, or IIII. 

[Nonretroactive as of January 1, 1986]

S.5.2. Parameters for Accuracy Class. - The accuracy class of a weighing device is designated by the manufacturer 

and shall comply with parameters shown in Table 3. 

[Nonretroactive as of January 1, 1986]

S.5.3. Multi-Interval and Multiple Range Scales, Division Value. - On a multi-interval scale and multiple range 

scale, the value of "e" shall be equal to the value of "d."2

 

(Added 1986) (Amended 1995) 

S.5.4. Relationship of Load Cell Verification Interval Value to the Scale Division. - The relationship of the value 

for the load cell verification scale interval, vmin, to the scale division, d, for a specific scale installation shall be:

(a) where N is the number of load cells in the scale for scales without lever systems: 

N

d

vmin 

 and,

(b) for scales with lever systems: multiple) (scalex 

min

N

d

v 

 [Nonretroactive as of January 1, 1994] 

 [Note: When the value of the scale division, d, is different than the verification scale division, e, for the scale, 

the value of e must be used in the formulae above] 

This requirement does not apply to complete scales and weighing elements which satisfy the following criteria: 

 

2 See Footnote 1 to Table 3 Parameters for Accuracy Classes
2.20. Scales 

2-13 

(1) The device has been evaluated for compliance with T.N.8.1. Temperature under the National Type 

Evaluation Program (NTEP); 

(2) The device has received an NTEP Certificate of Conformance; and 

(3) The device must be equipped with an automatic zero-setting mechanism which cannot be made 

inoperative in the normal weighing mode. (A test mode which permits the disabling of the automatic 

zero-setting mechanism is permissible, provided the scale cannot function normally while in this mode.) 

 (Added 1993) (Amended 1996) 

Table 3 

Parameters for Accuracy Classes

Class Value of the verification scale division 

(d or e1

)

Number of scale4 divisions (n)

Minimum Maximum

SI Units

I equal to or greater than 1 mg 50 000 --

II 1 to 50 mg, inclusive 100 100 000

equal to or greater than 100 mg 5 000 100 000

III2 0.1 to 2 g, inclusive 100 10 000

equal to or greater than 5 g 500 10 000

III L3 equal to or greater than 2 kg 2 000 10 000

IIII equal to or greater than 5 g 100 1 200

INCH-POUND Units 

III 0.0002 lb to 0.005 lb, inclusive 100 10 000

0.005 oz to 0.125 oz, inclusive 100 10 000

equal to or greater than 0.01 lb 500 10 000

equal to or greater than 0.25 oz 500 10 000

III L3 equal to or greater than 5 lb 2 000 10 000

IIII greater than 0.01 lb 100 1 200

greater than 0.25 oz 100 1 200

1

For Class I and II devices equipped with auxiliary reading means (i.e., a rider, a vernier, or a least significant decimal 

differentiated by size, shape, or color), the value of the verification scale division“e” is the value of the scale division 

immediately preceding the auxiliary means. 

2

 A scale marked “For prescription weighing only” may have a scale division not less than 0.01 g. (Added 1986) 

3

 The value of a scale division for crane and hopper (other than grain hopper) scales shall be not less than 0.2 kg (0.5 lb). 

The minimum number of scale divisions shall be not less than 1 000. 

4

On a multiple range or multi-interval scale the number of divisions for each range independently shall not exceed the 

maximum specified for the accuracy class. The number of scale divisions, n, for each weighing range is determined by 

dividing the scale capacity for each range by the verification scale division, e, for each range. On a scale system with 

multiple load receiving elements and multiple indications, each element considered shall not independently exceed the 

maximum specified for the accuracy class. If the system has a summing indicator, the nmax for the summed indication 

shall not exceed the maximum specified for the accuracy class.

[Nonretroactive as of January 1, 1986.] (Amended 1986, 1987, 1997, 1998, and 1999) (Footnote 4 Added 1997) 
2.20. Scales 

2-14 

S.6. Marking Requirements. [See also G-S.1., G-S.4., G-S.6., G-S.7., G-UR.2.1.1., and UR.3.4.1.] 

S.6.1. Nominal Capacity; Vehicle and Axle-Load Scales. - For all vehicle, axle-load, scales, the marked nominal 

capacity shall not exceed the concentrated load capacity (CLC) times the quantity of the number of sections in the 

scale minus 0.5. 

As a formula, this is stated as: nominal capacity < CLC x (N - 0.5) 

where N = the number of sections in the scale. 

 (See N.1.3.4. and T.N.3.1.) 

 [Nonretroactive as of January 1, 1989]

[Note: When the device is used in a combination railway track and vehicle weighing application, the above formula 

shall apply only to the vehicle scale application.] 

(Added 1988) (Amended 1999 and 2002) 

S.6.2. Location of Marking Information. - Scales that are not permanently attached to an indicating element, and 

for which the load-receiving element is the only part of the weighing/load-receiving element visible after installation, 

may have the marking information required in G-S.1. of the General Code and S.6. of the Scales Code located in an 

area that is accessible only through the use of a tool; provided that the information is easily accessible (e.g., the 

information may appear on the junction box under an access plate). The identification information for these scales 

shall be located on the weighbridge (load-receiving element) near the point where the signal leaves the weighing 

element or beneath the nearest access cover. 

(Added 1989) 

S.6.3. Scales, Main Elements, and Components of Scales or Weighing Systems. - Scales, main elements of scales 

when not contained in a single enclosure for the entire scale, load cells for which Certificates of Conformance (CC) 

have been issued under the National Type Evaluation Program, and other equipment necessary to a weighing system, 

but having no metrological effect on the weighing system, shall be marked as specified in Table S.6.3.a. and 

explained in the accompanying notes (Table S.6.3.b.) 

(Added 1990) 

S.6.4. Railway Track Scales. - A railway track scale shall be marked with the maximum capacity of each section of 

the load-receiving element of the scale. Such marking shall be accurately and conspicuously presented on, or 

adjacent to, the identification or nomenclature plate that is attached to the indicating element of the scale. The 

nominal capacity of a scale with more than two sections shall not exceed twice its rated section capacity. The 

nominal capacity of a two-section scale shall not exceed its rated section capacity.

[*Nonretroactive as of January 1, 2002] 

 (Amended 1988, 2001, and 2002) 

S.6.5. Livestock Scales. –A livestock scale shall be marked with the maximum capacity of each section of the 

load-receiving element of the scale. Such marking shall be accurately and conspicuously presented on, or adjacent to 

the identification or nomenclature plate that is attached to the indicating element of the scale. The nominal capacity 

of a scale with more than two sections shall not exceed twice its rated section capacity. The nominal capacity of a 

two-section scale shall not exceed its rated section capacity*. 

[*Nonretroactive as of January 1, 2003] 

 (Added 2002) 
2.20. Scales 

2-15 

Table S.6.3.a. 

Marking Requirements

To Be Marked With 

Weighing Equipment 

Weighing, loadreceiving, and 

indicating 

element in same 

housing or 

covered on the 

same CC1

Indicating element 

not permanently 

attached to weighing 

and load-receiving 

element or covered 

by a separate CC 

Weighing and loadreceiving element 

not permanently 

attached to 

indicating element 

or covered by a 

separate CC 

Load 

cell 

with 

CC 

(11) 

Other 

equipment 

or device 

(10) 

Manufacturer's ID (1) x x x x x 

Model Designation and Prefix (1) x x x x x 

Serial Number and Prefix (2) x x x x x (16) 

Certificate of Conformance Number 

(CC) (23) x x x x x (23) 

Accuracy Class (17) x x (8) x (19) x 

Nominal Capacity (3)(18)(20) x x x 

Value of Scale Division, "d" (3) x x 

Value of "e" (4) x x 

Temperature Limits (5) x x x x 

Concentrated Load Capacity (CLC) 

 (12)(20)(22) x x (9) 

Special Application (13) x x x 

Maximum Number of Scale 

Divisions (nmax) (6) x (8) x (19) x 

Minimum Verification Scale 

Division (emin) x (19) 

"S" or "M" (7) x 

Direction of Loading (15) x 

Minimum Dead Load x 

Maximum Capacity x 

Safe Load Limit x 

Load Cell Verification Interval 

 (vmin) (21) x 

Section Capacity (14)(20)(22) x x 

Note: For applicable notes, see Table S.6.3.b. 1

Weighing/load receiving elements and indicators which are in the same housing or which are permanently attached will 

generally appear on the same CC. If not in the same housing, elements shall be hard wired together or sealed with a 

physical seal or an electronic link. This requirement does not apply to peripheral equipment that has no input or effect on 

device calibrations or configurations. 

 (Added 1990) (Amended 1992, 1999, 2000, 2001 and 2002) (Footnote 1 Added 2001) 
2.20. Scales 

2-16 

Table S.6.3.b. 

Notes For Table S.6.3.a. 

1. Manufacturer's identification and model designation and model designation prefix*. 

 *[Nonretroactive as of January 1, 2003] 

(See also G-S.1.) [Prefix lettering may be initial capitals, all capitals or all lower case]

 (Amended 2000) 

2. Serial number [Nonretroactive as of January 1, 1968] and prefix [Nonretroactive as of January 1, 1986]. (See also 

G-S.1.) 

3. The nominal capacity and value of the scale division shall be shown together (e.g., 50 000 x 5 kg, 100 000 x 10 lb, 15 

x 0.005 kg , or 30 x 0.01 lb) adjacent to the weight display when the nominal capacity and value of the scale division 

are not immediately apparent. Each scale division value or weight unit shall be marked on multiple range or 

multi-interval scales. [Nonretroactive as of January 1, 1983]

4. Required only if different from "d." [Nonretroactive as of January 1, 1986]

5. Required only on Class III, III L, and IIII devices if the temperature range on the NTEP CC is narrower than and 

within -10 C to 40 C (14 F to 104 F). [Nonretroactive as of January 1, 1986]

6. This value may be stated on load cells in units of 1000; e.g., n: 10 is 10 000 divisions. [Nonretroactive as of 

January 1, 1988]

7. Denotes compliance for single or multiple load cell applications. It is acceptable to use a load cell with the “S” or 

Single Cell designation in multiple load cell applications as long as all other parameters meet applicable 

requirements. A load cell with the “M” or Multiple Cell designation can be used only in multiple load cell 

applications.[Nonretroactive as of January 1, 1988]

 (Amended 1999) 

8. An indicating element not permanently attached to a weighing element shall be clearly and permanently marked with 

the accuracy Class of I, II, III, III L, or IIII, as appropriate, and the maximum number of scale divisions, nmax , for 

which the indicator complies with the applicable requirement. Indicating elements that qualify for use in both Class 

III and III L applications may be marked III/III L and shall be marked with the maximum number of scale divisions 

for which the device complies with the applicable requirements for each accuracy class. [Nonretroactive as of 

January 1, 1988] 

9. For vehicle and axle-load scales only. The CLC shall be added to the load-receiving element of any such scale not 

previously marked at the time of modification. [Nonretroactive as of January 1, 1989] 

 (Amended 2002) 

10. Necessary to the weighing system but having no metrological effect, e.g., auxiliary remote display, keyboard, etc. 

11. The markings may be either on the load cell or in an accompanying document; except that, if an accompanying 

document is provided, the serial number shall appear both on the load cell and in the document. [Nonretroactive as 

of January 1, 1988] The manufacturer's name or trademark, the model designation, and identifying symbols for the 

model and serial numbers as required by paragraph G.-S.1. shall also be marked both on the load cell and in any 

accompanying document. [Nonretroactive as of January 1, 1991] 

12. Required on the indicating element and the load-receiving element of vehicle and axle-load scales. Such marking 

shall be identified as "concentrated load capacity" or by the abbreviation "CLC."* 

 [*Nonretroactive as of January 1, 1989]

 (Amended 2002) 
2.20. Scales 

2-17 

Table S.6.3.b. 

Notes For Table S.6.3.a. 

13. A scale designed for a special application rather than general use shall be conspicuously marked with suitable 

words visible to the operator and customer restricting its use to that application, e.g., postal scale, prepack scale, 

weight classifier, etc.* When a scale is installed with an operational counting feature, the scale shall be marked on 

both the operator and customer side with the statement "The counting feature is not legal for trade." 

[*Nonretroactive as of January 1, 1986]

 (Amended 1994) 

14. Required on livestock* and railway track scales. When marked on vehicle and axle-load scales manufactured 

before January 1, 1989, it may be used as the CLC. For livestock scales manufactured between January 1, 1989 and 

January 1, 2003, required markings may be either CLC or section capacity. [*Nonretroactive as of January 1, 2003. 

 (Amended 2002) 

15. Required if the direction of loading the load cell is not obvious. [Nonretroactive as of January 1, 1988]

16. Serial number [Nonretroactive as of January 1, 1968] and prefix [Nonretroactive as of January 1, 1986]. (See also 

G-S.1.) Modules without "intelligence" on a modular system (e.g., printer, keyboard module, cash drawer, and 

secondary display in a point-of-sale system) are not required to have serial numbers. 

17. The accuracy Class of a device shall be marked on the device with the appropriate designation as I, II, III, III L, or 

IIII. [Nonretroactive as of January 1, 1986] 

18. The nominal capacity shall be conspicuously marked as follows: 

(a) on any scale equipped with unit weights or weight ranges; 

(b) on any scale with which counterpoise or equal-arm weights are intended to be used; 

(c) on any automatic-indicating or recording scale so constructed that the capacity of the indicating or recording 

element, or elements, is not immediately apparent; 

(d) on any scale with a nominal capacity less than the sum of the reading elements; and 

(e) on the load-receiving element (weigh-bridge) of vehicle, axle-load, and livestock scales.* 

 [*Nonretroactive as of January 1, 1989]

 (Amended 1992) 

19. [Nonretroactive as of January, 1, 1988] 

 (Amended 1992) 

20. Combination vehicle/railway track scales must be marked with both the nominal capacity and CLC for vehicle 

weighing and the nominal capacity and section capacity for railway weighing. All other requirements relating to 

these markings will apply. [Nonretroactive as of January 1, 2000] 

 (Added 1999) 

21. The value of the load cell verification interval (vmin) must be stated in mass units. In addition to this information, a 

device may be marked with supplemental representations of vmin. [Nonretroactive as of January 1, 2001]

 (Added 1999) 

22. Combination vehicle/livestock scales must be marked with both the CLC for vehicle weighing and the section 

capacity for livestock weighing. All other requirements relative to these markings will apply. 

 [Nonretroactive as of January 1, 2003] 

 (Added 2002) 

23. Required only if a CC has been issued for the device or equipment. 

 [Nonretroactive as of January 1, 2003] 

 (G-S.1. Identification (f) Added 2001) 
2.20. Scales 

2-18 

N. Notes 

N.1. Test Procedures.

N.1.1. Increasing-Load Test. - The increasing-load test shall be conducted on all scales with the test loads 

approximately centered on the load-receiving element of the scale, except on a scale having a nominal capacity 

greater than the total available known test load. When the total test load is less than the nominal capacity, the test 

load is used to greatest advantage by concentrating it, within prescribed load limits, over the main load supports of 

the scale. 

N.1.2. Decreasing-Load Test (Automatic Indicating Scales). - The decreasing-load test shall be conducted with 

the test load approximately centered on the load- receiving element of the scale. 

N.1.2.1. Scales Marked I, II, III, or IIII. - Except for portable wheel load weighers, decreasing-load tests shall 

be conducted on scales marked I, II, III or IIII and with n equal to or greater than 1000 with test loads equal to 

the maximum test load at each tolerance value. For example, on a Class III scale, at test loads equal to 4000 d, 

2000 d, and 500 d; for scales with n less than 1000, the test load shall be equal to one-half of the maximum load 

applied in the increasing-load test. (See Table 6) 

(Amended 1998) 

N.1.2.2. All Other Scales. - On all other scales, except for portable wheel load weighers, the decreasing-load 

test shall be conducted with a test load equal to one-half of the maximum load applied in the increasing-load test. 

 

(Amended 1998) 

N.1.3. Shift Test.

N.1.3.1. Bench or Counter Scales. - A shift test shall be conducted with a half-capacity test load centered 

successively at four points equidistant between the center and the front, left, back, and right edges of the 

load-receiving element. 

N.1.3.2. Dairy-Product-Test Scales. - A shift test shall be conducted with a test load of 18 grams successively 

positioned at all points on which a weight might reasonably be placed in the course of normal use of the scale. 

N.1.3.3. Equal-Arm Scales. - A shift test shall be conducted with a half-capacity test load positioned on each 

pan as prescribed in N.1.3.1. An equal test load shall be centered on the other pan. 

N.1.3.4. Vehicle Scales, Axle-Load Scales, and Livestock Scales. - At least one shift test shall be conducted 

with a minimum test load of 12.5 percent of scale capacity and may be performed anywhere on the 

load-receiving element using the prescribed test patterns and maximum test loads specified below. (Two-section 

livestock scales shall be tested consistent with N.1.3.8.) 

(Amended 1991 and 2000) 

(a) Prescribed Test Pattern. - The normal prescribed test pattern shall be an area of 1.2 m (4 ft) in length and 

3.0 m (10 ft) in width or the width of the scale platform, whichever is less. Multiple test patterns may be 

utilized when loaded in accordance with Paragraph (b). 

(Part (a) Amended 1997 and 2001) 

(b) Maximum Loading. - When loading the scale for testing, one side of the test pattern shall be loaded to no 

more than half of the concentrated load capacity or test load before loading the other side. The area 

covered by the test load may be less than 1.2 m (4 ft) x the width of the scale; for test patterns less than 1.2 

m (4 ft) in length the maximum loading shall meet the formula: [(wheel base of test cart or length of test 

load divided by 48 in) x 0.9 x CLC]. The maximum test load applied to each test pattern shall not exceed 

the concentrated load capacity of the scale. When the test pattern exceeds 1.2 m (4 ft), the maximum test 

load applied shall not exceed the concentrated load capacity times the largest “r” factor in Table UR.3.2.1. 

for the length of the area covered by the test load. For weighing elements installed prior to January 1, 
2.20. Scales 

2-19 

1989, the rated section capacity may be substituted for concentrated load capacity to determine maximum 

loading. An example of a possible test pattern is shown below. 

4’ 4’ 4’ 4’ 4’ 

 

 

Section 

1 

 Midway between 

sections 1 and 2 

 Section 

2 

 Midway between 

sections 2 and 3 

 Section 

3 

(Part (b) Amended 1997) 

(c) Multiple Pattern Loading. - To test to the nominal capacity, multiple patterns may be simultaneously 

loaded in a manner consistent with the method of use. 

(d) Other Designs. - Special design scales and those that are wider than 3.7 m (12 ft) shall be tested in a 

manner consistent with the method of use but following the principles described above. 

(Amended 1988) 

N.1.3.5. Railway Track Scales Weighing Individual Cars in Single Drafts. - A shift test shall be conducted 

with at least two different test loads, if available, distributed over, to the right and left of, each pair of main 

levers or other weighing elements supporting each section of the scale. 

N.1.3.6. Monorail Scales, Static Test. - A shift test shall be conducted with a test load equal to the largest load 

that can be anticipated to be weighed in a given installation, but never less than one-half scale capacity. The 

load shall be placed successively on the right end, the left end, and the center of the live rail. 

(Added 1985) 

N.1.3.6.1. Dynamic Monorail Weighing Systems. - Dynamic tests with livestock carcasses should be 

conducted to duplicate actual use conditions. No less than 20 test loads using carcasses or portions of 

carcasses of the type normally weighed should be used in the dynamic test; two additional test loads may be 

included in the test run for use in the event that one or two test loads are rendered unusable during the 

dynamic test. Prior to starting the dynamic test, the test carcasses must be positioned far enough ahead of 

the scale so that their swaying motion settles to duplicate the normal sway of a continuously running plant 

chain. If the plant conveyer chain does not space or prevent the carcasses from touching one another, 

dynamic tests should not be conducted until this condition has been corrected. 

All carcasses shall be individually weighed statically on either the same scale being tested dynamically or 

another monorail scale with the same or smaller divisions and in close proximity. (The scale selected for 

weighing the carcasses shall first be tested statically with test weights.) 

If the scale being tested is used for weighing freshly slaughtered animals, (often referred to as a "hot scale") 

care must be taken to get a static weighment as quickly as possible before or following the dynamic 

weighment to avoid loss due to shrink. If multiple dynamic tests are conducted using the same carcasses, 

static weights should be obtained before and after multiple dynamic tests. If the carcass changes weight 

between static tests, the amount of weight change should be taken into account, or the carcass should be 

disregarded for tolerance purposes. 

(Note: For a dynamic monorail test, the reference scale shall comply with the principles in the in the 

Fundamental Considerations Paragraph 3.2. Tolerances for Standards.) 

 (Added 1996) (Amended 1999) 

N.1.3.7. Vehicle On-Board Weighing Systems. - The shift test for a vehicle on-board weighing system shall be 

conducted in a manner consistent with its normal use. For systems that weigh as part of the lifting cycle, the 

center of gravity of the load may be shifted in the vertical direction as well as from side to side. In other cases, 

the center of gravity may be moved to the extremes of the load-receiving element using loads of a magnitude that 

reflect normal use (i.e., the load for the shift test may exceed one-half scale capacity), and may, in some cases, 

be equal to the capacity of the scale. The shift test may be conducted when the weighing system is out of level 

to the extent that the weighing system remains operational. 

(Added 1992) 
2.20. Scales 

2-20 

N.1.3.8. All Other Scales Except Crane Scales, Hanging Scales, Hopper Scales, Wheel-Load Weighers, 

and Portable Axle-Load Weighers. - A shift test shall be conducted with a half-capacity test load centered, as 

nearly as possible, successively at the center of each quarter of the load-receiving element, or with a quarter 

capacity test load centered, as nearly as possible, successively over each main load support. 

(Amended 1987) 

N.1.4. Sensitivity Test. – A sensitivity test shall be conducted on nonautomatic-indicating (weighbeam) scales only, 

with the weighing device in equilibrium at zero-load and at maximum test load. The test shall be conducted by 

increasing or decreasing the test load in an amount equal to the applicable value specified in T.2. or T.N.6. 

N.1.5. Discrimination Test. - A discrimination test shall be conducted on all automatic indicating scales with the 

weighing device in equilibrium at zero load and at maximum test load, and under controlled conditions in which 

environmental factors are reduced to the extent that they will not affect the results obtained. 

[Nonretroactive as of January 1, 1986]

(Added 1985) 

N.1.5.1. Digital Device. - On a digital device, this test is conducted from just below the lower edge of the zone 

of uncertainty for increasing load tests, or from just above the upper edge of the zone of uncertainty for 

decreasing-load tests. 

 

N.1.6. RFI Susceptibility Tests, Field Evaluation. - An RFI test shall be conducted at a given installation when 

the presence of RFI has been verified and characterized if those conditions are considered "usual and customary." 

(Added 1986) 

N.1.7. Ratio Test. - A ratio test shall be conducted on all scales employing counterpoise weights and on 

nonautomatic-indicating equal-arm scales. 

N.1.8. Material Tests. - A material test shall be conducted on all customer-operated bulk weighing systems for 

recycled materials using bulk material for which the device is used. Insert into the device, in a normal manner, 

several accurately pre-weighed samples (free of foreign material) in varying amounts approximating average drafts. 

N.1.9. Zero-Load Balance Change. - A zero-load balance change test shall be conducted on all scales after the 

removal of any test load. The zero-load balance should not change by more than the minimum tolerance applicable. 

(Also see G-UR.4.2.) (Renumbered 1988) 

N.2. Verification (Testing) Standards. - Field standard weights used in verifying weighing devices shall comply with 

requirements of NIST Handbook 105-1 (Class F) or the tolerances expressed in Fundamental Considerations, paragraph 

3.2. (i.e., one-third of the smallest tolerance applied). 

(Amended 1986) 

N.3. Minimum Test Weights and Test Loads2

. - The minimum test weights and test loads for in-service tests (except 

railway track scales) are shown in Table 4. [See Table 4 for footnote 2

.] 

(Added 1984) (Amended 1988) 

N.3.1. Minimum Test-Weight Load and Recommended Strain-Load Test for Railway Track Scales. 

(Amended 1990) 

N.3.1.1. Approval. - The test-weight load shall be not less than 35 000 kg (80 000 lb). A strain-load test 

conducted up to the used capacity of the weighing system is recommended. 

(Added 1990) 

N.3.1.2. Interim Approval. - A test-weight load of not less than 13 500 kg (30 000 lb) and a strain-load test up 

to at least 25 percent of scale capacity may be used to return a scale into service following repairs. 

(Added 1990) 

Note: The length of time the scale may be used following an interim test is at the discretion of the official with 

statutory authority. 

(Added 1990) 
2.20. Scales 

2-21 

N.3.1.3. Enforcement Action for Inaccuracy. - To take enforcement action on a scale that is found to be 

inaccurate, a minimum test load of 13 500 kg (30 000 lb) must be used. 

(Added 1990) 

Table 4. 

Minimum Test Weights and Test Loads1

Device capacity Minimums (in terms of device capacity) (where practicable) 

Test weights (greater of) Test loads2

0 to 150 kg 

(0 to 300 lb) 100 % 

151 to 1 500 kg 

(301 to 3 000 lb) 25 % or 150 kg (300 lb) 75 % Test weights to dial face capacity, 

1 000 d, or test load to used capacity, if 

greater than minimums specified 

During initial verification, a scale 

should be tested to capacity. 

1 501 to 20 000 kg 

(3 001 to 40 000 lb) 12.5 % or 500 kg (1 000 lb) 50 % 

20 001 kg+ 

(40 001 lb+) 12.5 % or 5 000 kg (10 000 lb) 25 %3

1

 If the amount of test weight in Table 4 combined with the load on the scale would result in an unsafe condition, then 

the appropriate load will be determined by the official with statutory authority. 

2

The term "test load" means the sum of the combination of field standard test weights and any other applied load used 

in the conduct of a test using substitution test methods. Not more than three substitutions shall be used during 

substitution testing, after which the tolerances for strain load tests shall be applied to each set of test loads. 

3

 The scale shall be tested from zero to at least 12.5 % of scale capacity using known test weights and then to at least 

25 % of scale capacity using either a substitution or strain load test that utilizes known test weights of at least 12.5 % 

of scale capacity. Whenever practical, a strain load test should be conducted to the used capacity of the scale. When a 

strain load test is conducted, the tolerance applies only to the known test load. 

(Amended 1988, 1989 and 1994) 

N.4. Coupled-in-Motion Railroad Weighing Systems3

N.4.1. Weighing Systems Used to Weigh Trains of Less Than 10 Cars. - These weighing systems shall be tested 

using a consecutive-car test train consisting of the number of cars weighed in the normal operation run over the 

weighing system a minimum of five times in each mode of operation following the final calibration. 

(Added 1990) (Amended 1992) 

N.4.2. Weighing Systems Placed in Service Prior to January 1, 1991, and Used to Weigh Trains of 10 or More 

Cars. - The minimum test train shall be a consecutive-car test train of no less than 10 cars run over the scale a 

minimum of five times in each mode of operation following final calibration. 

(Added 1990) (Amended 1992) 

N.4.3. Weighing Systems Placed in Service on or After January 1, 1991, and Used to Weigh Trains of 10 or 

More Cars. – 

(a) These weighing systems shall be tested using a consecutive-car test train of no less than 10 cars run over the 

scale a minimum of five times in each mode of operation following final calibration; or 

 

3

 A test weight car that is representative of one of the types of cars typically weighed on the scale under test may be used 

wherever reference weight cars are specified. 

(Added 1991) 
2.20. Scales 

2-22 

(b) if the official with statutory authority determines it necessary, the As Used Test Procedures outlined in 

N.4.3.1. shall be used. 

 (Added 1990) (Amended 1992) 

N.4.3.1. As Used Test Procedures - A weighing system shall be tested in a manner that represents the normal 

method of operation and length(s) of trains normally weighed. The weighing systems may be tested using either: 

(1) a consecutive-car test train of a length typical of train(s) normally weighed; or 

(2) a distributed-car test train of a length typical of train(s) normally weighed. 

However, a consecutive-car test train of a shorter length may be used provided that initial verification test results 

for the shorter consecutive-car test train agree with the test results for the distributed-car or full-length 

consecutive-car test train as specified in N.4.3.1.1. 

The official with statutory authority shall be responsible for determining the minimum test train length to be used 

on subsequent tests. 

(Added 1990) (Amended 1992) 

N.4.3.1.1. Initial Verification. - Initial verification tests should be performed on any new weighing system 

and whenever either the track structure or the operating procedure changes. If a consecutive-car test train of 

length shorter than trains normally weighed is to be used for subsequent verification, the shorter 

consecutive-car test train results shall be compared either to a distributed-car or to a consecutive-car test 

train of length(s) typical of train(s) normally weighed. 

The difference between the total train weight of the train(s) representing the normal method of operation and 

the weight of the shorter consecutive-car test train shall not exceed 0.15 percent. If the difference in test 

results exceeds 0.15 percent, the length of the shorter consecutive-car test train shall be increased until 

agreement within 0.15 percent is achieved. Any adjustments to the weighing system based upon the use of a 

shorter consecutive-car test train shall be offset to correct the bias that was observed between the full-length 

train test and the shorter consecutive-car test train. 

(Added 1990) (Amended 1992 and 1993) 

N.4.3.1.2. Subsequent Verification. - The test train may consist of either a consecutive-car test train with a 

length not less than that used in initial verification, or a distributed-car test train representing the number of 

cars used in the normal operation. 

(Added 1990) 

 

N.4.3.1.3. Distributed Car Test Trains. - 

(a) The length of the train shall be typical of trains that are normally weighed. 

(b) The reference weight cars shall be split into three groups, each group consisting of 10 cars or 10 

percent of the train length, whichever is less. 

(Amended 1991) 

(c) The test groups shall be placed near the front, around the middle, and near the end of the train. 

(d) Following the final adjustment, the distributed-car test train shall be run over the scale at least three 

times or shall produce 50 weight values, whichever is greater. 

(e) The weighing system shall be tested in each mode of operation. 

(Added 1990) (Amended 1992) 

N.4.3.1.4. Consecutive-Car Test Trains. -

 (a) A consecutive-car test train shall consist of at least 10 cars. 
2.20. Scales 

2-23 

 (b) If the consecutive-car test train consists of between 10 cars and 20 cars, inclusive, it shall be run 

over the scale a minimum of five times in each mode of operation following the final calibration. 

 (c) If the consecutive-car test train consists of more than 20 cars, it shall be run over the scale a 

minimum of three times in each mode of operation. 

 (Added 1990) (Amended 1992) 

N.5. Uncoupled-in-Motion Railroad Weighing System. - An uncoupled-in-motion scale shall be tested statically 

before being tested in motion by passing railroad reference weight cars over the scale. When an uncoupled-in-motion 

railroad weighing system is tested, the car speed and the direction of travel shall be the same as when the scale is in 

normal use. The minimum in-motion test shall be three reference weight cars passed over the scale three times. The cars 

shall be selected to cover the range of weights that are normally weighed on the system and to reflect the types of cars 

normally weighed. 

(Added 1993) 

N.6. Nominal Capacity of Prescription Scales. - The nominal capacity of a prescription scale shall be assumed to be 

1/2 apothecary ounce, unless otherwise marked. (Applicable only to scales not marked with an accuracy class.) 

T. Tolerances Applicable to Devices 

not Marked I, II, III, III L, or IIII

T.1. Tolerance Values.

T.1.1. General. - The tolerances applicable to devices not marked with an accuracy class shall have the tolerances 

applied as specified in Table T.1.1. 

(Amended 1990) 

T.1.2. Postal and Parcel Post Scales. - The tolerances for postal and parcel post scales are given in Table T.1.1. and 

Table 5. 

(Amended 1990) 

T.2. Sensitivity Requirement (SR)

T.2.1. Application. - The sensitivity requirement (SR) is applicable to all nonautomatic-indicating scales not marked 

I, II, III, III L, or IIII, and is the same whether acceptance or maintenance tolerances apply. 

T.2.2. General. - Except for scales specified in paragraphs T.2.3. through T.2.8.: 2 d, 0.2 percent of the scale 

capacity, or 40 lb, whichever is least. 

T.2.3. Prescription Scales. 6 mg (0.1 grain). 

T.2.4. Jewelers' Scales.

T.2.4.1. With One-Half Ounce Capacity or Less. - 6 mg (0.1 grain). 

T.2.4.2. With More Than One-Half Ounce Capacity. - 1 d or 0.05 percent of the scale capacity, whichever is 

less. 

T.2.5. Dairy-Product-Test Scales. 

T.2.5.1. Used in Determining Butterfat Content. - 32 mg (0.5 grain). 

T.2.5.2. Used in Determining Moisture Content. - 19 mg (0.3 grain). 
2.20. Scales 

2-24 

Table T.1.1. Tolerances for Unmarked Scales

Type of Device Subcategory Min. Tol. Accept. Tol. Maint. Tol. Decreasing-Load Multiplier1 

Vehicle, axle-load, livestock, railway track (weighing statically), crane, and hopper (other than grain hopper) 

 Class III L, T.N.3.1 (Table 6) and T.N.3.2. 1.0 

TTT

Grain test scales n # 10 000 n > 10 000 Class III, T.N.3.1. (Table 6) and T.N.3.2. Class II, T.N.3.1. (Table 6) and T.N.3.2. 1.0 Railway track scales weighing in motion 

T.N.3.6. except that for T.N.3.6.2. (a), no single error shall exceed four times the maintenance tolerance. 1.0 

Monorail Scales, In-Motion T.N.3.8. 1.0 Customer-Operated BulkWeighing Systems for Recycled Materials 

± 5 % of applied material test load. Average error on 10 or more test loads # 2.5 %. 1.0 

Wheel-load weighers and portable axle-load scales 

Tested individually or in pairs2

0.5 d or 50 lb, whichever is greater 1 % of test load 2 % of test load 1.53

Prescription scales 0.1 grain (6 mg) 0.1 % of test load load 0.1 % of test load 1.5 Jewelers' scales Graduated 0.5 d 

0.05 % of test load 0.05 % of test load

1.5 

 Ungraduated 

Sensitivity or smallest weight, whichever is less 

Dairy-product-test scale Loads < 18 g 18 g load 0.2 grain 0.2 grain 0.2 grain 0.3 grain 0.2 grain 0.5 grain 1.5 Postal and parcel post scales Designed/used to weigh loads < 2 lb 

Loads < 2 lb 

15 grain, 1 g, 1/32 oz, 0.03 oz, or 0.002 lb 

15 grain, 1 g, 1/32 oz, 0.03 oz, or 0.002 lb 

15 grain, 1 g, 1/32 oz, 0.03 oz, or 0.002 lb 

1.5 

 Loads $ 2 lb Table 5 Table 5 Table 5 Other postal and parcel post scales Table 5 Table 5 Table 5 1.5 All other scales 

n > 5000 

0.5d or 0.05 % of scale capacity, whichever is less 

0.05 % of test load 0.1 % of test load 1.5 T

T

n # 5000 Class III, T.N.3.1., Table 6 and T.N.3.2. 1.0 

TTT

1 The decreasing load test applies only to automatic indicating scales. 2 If marked and tested as a pair, the tolerance shall be applied to the sum of the indications. (Table Added 1990; Amen

 3 The decreasing load test does not apply to portable wheel load weighers. 
2.20. Scales 

2-25 

Table 5. 

Maintenance and Acceptance Tolerances for Unmarked 

Postal and Parcel Post Scales

Scale capacity Test loads Maintenance tolerance 

(±) 

Acceptance tolerance 

(±) 

(lb) (lb) (oz) (lb) (oz) (lb) 

0 to 4, inclusive* 0 to 1, inclusive 1/32 0.002 1/32 0.002 

 over 1 1/8 0.008 1/16 0.004 

over 4* 0 to 7, inclusive 3/16 0.012 3/16 0.012 

7+ to 24, inclusive 3/8 0.024 3/16 0.012 

24+ to 30, inclusive 1/2 0.030 1/4 0.015 

over 30 0.1 % of Test Load 0.05 % of Test Load 

*See Table T.1.1. for scales designed and/or used to weigh loads less than 2 lb. 

T.2.7. Vehicle, Axle-Load, Livestock, and Animal Scales.

T.2.7.1. Equipped With Balance Indicators. - 1 d. 

T.2.7.2. Not Equipped With Balance Indicators. - 2 d or 0.2 percent of the scale capacity, whichever is less. 

 T.2.8. Railway Track Scales. - 3 d or 100 lb, whichever is less. 

T.3. Sensitivity Requirement, Equilibrium Change Required.

The minimum change in equilibrium with test loads equal to the values specified in T.2. shall be as follows: 

(a) Scale With a Trig Loop but Without a Balance Indicator. - The position of rest of the weighbeam shall change 

from the center of the trig loop to the top or bottom, as the case may be. 

(b) Scale With a Single Balance Indicator and Having a Nominal Capacity of Less Than 250 kg (500 lb). - The 

position of rest of the indicator shall change 1.0 mm (0.04 in) or one division on the graduated scale, whichever 

is greater. 

(c) Scale With a Single Balance Indicator and Having a Nominal Capacity of 250 kg (500 lb) or Greater. - The 

position of rest of the indicator shall change 6.4 mm (0.25 in) or one division on the graduated scale or the width 

of the central target area, whichever is greater. However, the indicator on a batching scale shall change 3.2 mm 

(0.125 in) or one division on the graduated scale, whichever is greater. 

(d) Scale With Two Opposite-Moving Balance Indicators. - The position of rest of the two indicators moving in 

opposite directions shall change 1.0 mm (0.04 in) with respect to each other. 

(e) Scale With Neither a Trig Loop nor a Balance Indicator. - The position of rest of the weighbeam or lever system 

shall change from the horizontal, or midway between limiting stops, to either limit of motion. 

T.4. Radio Frequency Interference (RFI) and Other Electromagnetic Interference Susceptibility. - The difference 

between the weight indication with the disturbance and the weight indication without the disturbance, shall not exceed 

one scale division (d) or the equipment shall: 

(a) blank the indication, or 

 

(b) provide an error message, or 

 
2.20. Scales 

2-26 

(c) the indicator shall be so completely unstable that it could not be interpreted, or transmitted into memory or to a 

recording element, as a correct measurement value. 

(Added 1986) 

T.5. Operating Temperature. - An indicating or recording element shall not display or record any usable values until the 

operating temperature necessary for accurate weighing and a stable zero-balance condition has been attained. 

[Nonretroactive and effective January 1, 1981]

(Added 1986) 

T.N. Tolerances Applicable to Devices 

Marked I, II, III, III L, & IIII.

T.N.1. Principles.

T.N.1.1. Design. - The tolerance for a weighing device is a performance requirement independent of the design 

principle used. 

T.N.1.2. Accuracy Classes. - Weighing devices are divided into accuracy classes according to the number of scale 

divisions (n) and the value of the scale division (d). 

T.N.1.3. Scale Division. - The tolerance for a weighing device is related to the value of the scale division (d) or the 

value of the verification scale division (e) and is generally expressed in terms of d or e. 

T.N.2. Tolerance Application.

T.N.2.1. General. - The tolerance values are positive (+) and negative (-) with the weighing device adjusted to zero 

at no load. When tare is in use, the tolerance values are applied from the tare zero reference; the tolerance values 

apply to certified test loads only. 

T.N.2.2. Type Evaluation Examinations. - For type evaluation examinations, the tolerance values apply to 

increasing and decreasing load tests within the temperature, power supply, and barometric pressure limits specified in 

T.N.8. 

T.N.2.3. Subsequent Verification Examinations. - For subsequent verification examinations, the tolerance values 

apply regardless of the influence factors in effect at the time of the conduct of the examination. (Also see G-N.2.) 

T.N.2.4. Multi-Interval and Multiple Range (Variable Division-Value) Scales. - For multi-interval and multiple 

range scales, the tolerance values are based on the value of the scale division of the range in use. 

T.N.2.5. Ratio Tests. - For ratio tests, the tolerance values are 0.75 of the applicable tolerances. 

T.N.3. Tolerance Values.

T.N.3.1. Maintenance Tolerance Values. - The maintenance tolerance values are as specified in Table 6. 

T.N.3.2. Acceptance Tolerance Values. - The acceptance tolerance values shall be one-half the maintenance 

tolerance values. 

T.N.3.3. Wheel-Load Weighers and Portable Axle-Load Weighers of Class IIII. - The tolerance values are two 

times the values specified in T.N.3.1. and T.N.3.2. 

(Amended 1986) 

T.N.3.4. Crane and Hopper (Other than Grain Hopper) Scales. - The maintenance and acceptance tolerances 

shall be as specified in T.N.3.1. and T.N.3.2. for Class III L, except that the tolerance for crane and construction 

materials hopper scales shall not be less than 1 d or 0.1 percent of the scale capacity, whichever is less. 

(Amended 1986) 
2.20. Scales 

2-27 

Table 6. 

Maintenance Tolerances 

(All values in this table are in scale divisions)

Tolerance in scale divisions 

 1 2 3 5 

Class Test Load 

 I 0 - 50 000 50 001 - 200 000 200 001 + 

 II 0 - 5 000 5 001 - 20 000 20 001 + 

 III 0 - 500 501 - 2 000 2 001 - 4 000 4 001 + 

 IIII 0 - 50 51 - 200 201 - 400 401 + 

 III L 0 - 500 501 - 1 000 (Add 1d for each additional 500 d or fraction thereof) 

T.N.3.5. Separate Main Elements: Load Transmitting Element, Indicating Element, Etc. - If a main element 

separate from a weighing device is submitted for type evaluation, the tolerance for the element is 0.7 that for the 

complete weighing device. This fraction includes the tolerance attributable to the testing devices used. 

T.N.3.6. Coupled-In-Motion Railroad Weighing Systems. - The maintenance and acceptance tolerance values for 

the group of weight values appropriate to the application must satisfy the following conditions: 

(Amended 1990 and 1992) 

T.N.3.6.1. - For any group of weight values, the difference in the sum of the individual in-motion car weights of 

the group as compared to the sum of the individual static weights shall not exceed 0.2 percent. 

(Amended 1990) 

T.N.3.6.2. - If a weighing system is used to weigh trains of five or more cars, and if the individual car weights 

are used, any single weight value within the group must meet the following criteria: 

 

(a) no single error may exceed three times the static maintenance tolerance; 

(b) not more than 5 percent of the errors may exceed two times the static maintenance tolerance; and 

(c) not more than 35 percent of the errors may exceed the static maintenance tolerance. 

(Amended 1990 and 1992) 

T.N.3.6.3. - For any group of weight values wherein the sole purpose is to determine the sum of the group, 

T.N.3.6.1. alone applies. 

(Amended 1990) 

T.N.3.6.4. - For a weighing system used to weigh trains of less than five cars, no single car weight within the 

group may exceed the static maintenance tolerance. 

(Amended 1990 and 1992) 

T.N.3.7. Uncoupled-in-Motion Railroad Weighing Systems. - The maintenance and acceptance tolerance values 

for any single weighment within a group of non-interactive (i.e., uncoupled) loads, the weighment error shall not 

exceed the static maintenance tolerance. 

(Amended 1992) 

T.N.3.8. Dynamic Monorail Weighing System. - Acceptance tolerance shall be the same as the maintenance 

tolerance shown in Table 6. On a dynamic test of 20 or more individual test loads, 10 percent of the individual test 

loads may be in error, each not to exceed two times the tolerance. The error on the total of the individual test loads 

shall not exceed ± 0.2 percent. (See also Note in N.1.3.6.1.) For equipment undergoing type evaluation, a tolerance 

equal to one-half the maintenance tolerance values shown in Table 6 shall apply. 

[Nonretroactive January 1, 2002]

 (Added 1986) (Amended 1999 and 2001) 
2.20. Scales 

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T.N.3.9. Materials Test on Customer-Operated Bulk Weighing Systems for Recycled Materials. - The 

maintenance and acceptance tolerance shall be ± 5 percent of the applied materials test load except that the average 

error on 10 or more test materials test loads shall not exceed ± 2.5 percent. 

(Added 1986) 

T.N.4. Agreement of Indications.

T.N.4.1. Multiple Indicating/Recording Elements. - In the case of a scale or weighing system equipped with more 

than one indicating element or indicating element and recording element combination, where the indicators or 

indicator/recorder combination are intended to be used independently of one another, tolerances shall be applied 

independently to each indicator or indicator/recorder combination. 

(Amended 1986) 

T.N.4.2. Single Indicating/Recording Element. - In the case of a scale or weighing system with a single indicating 

element or an indicating/recording element combination, and equipped with component parts such as unit weights, 

weighbeam and weights, or multiple weighbeams that can be used in combination to indicate a weight, the difference 

in the weight value indications of any load shall not be greater than the absolute value of the applicable tolerance for 

that load, and shall be within tolerance limits. 

(Amended 1986) 

T.N.4.3. Single Indicating Element/Multiple Indications. - In the case of an analog indicating element equipped 

with two or more indicating means within the same element, the difference in the weight indications for any load 

other than zero shall not be greater than one-half the value of the scale division (d) and be within tolerance limits. 

(Amended 1986) 

T.N.4.4. Shift or Section Tests. - The range of the results obtained during the conduct of a shift test or a section test 

shall not exceed the absolute value of the maintenance tolerance applicable and each test result shall be within 

applicable tolerances. 

(Added 1986) 

T.N.4.5. Time Dependence. - At constant test conditions, the indication 20 seconds after the application of a load 

and the indication after 1 hour shall not differ by more than: 

(a) one-half of the absolute value of the applicable tolerance for the applied load for class III L devices; and 

(b) the absolute value of the applicable tolerance for the applied load for all other devices. 

(Amended 1989) 

T.N.5. Repeatability. - The results obtained from several weighings of the same load under reasonably static test 

conditions shall agree within the absolute value of the maintenance tolerance for that load, and shall be within applicable 

tolerances. 

T.N.6. Sensitivity. - This section is applicable to all nonautomatic-indicating scales marked I, II, III, III L, or IIII. 

T.N.6.1. Test Load.

(a) The test load for sensitivity for nonautomatic-indicating vehicle, axle-load, livestock, and animal scales shall 

be 1 d for scales equipped with balance indicators, and 2 d or 0.2 percent of the scale capacity, whichever is 

less, for scales not equipped with balance indicators. 

(b) For all other nonautomatic-indicating scales, the test load for sensitivity shall be 1 d at zero and 2 d at 

maximum test load. 

T.N.6.2. Minimum Change of Indications. - The addition or removal of the test load for sensitivity shall cause a 

minimum permanent change as follows: 
2.20. Scales 

2-29 

(a) for a scale with trig loop but without a balance indicator, the position of the weighbeam shall change from 

the center to the outer limit of the trig loop; 

 

(b) for a scale with balance indicator, the position of the indicator shall change one division on the graduated 

scale, the width of the central target area, or the applicable value as shown below, whichever is greater: 

 

Scale of Class I or II: 1 mm (0.04 in), 

 Scale of Class III or IIII with a maximum capacity of 30 kg (70 lb) or less: 2 mm (0.08 in), 

Scale of Class III, III L, or IIII with a maximum capacity of more than 30 kg (70 lb): 5 mm 0.20 in); 

(c) for a scale without a trig loop or balance indicator, the position of rest of the weighbeam or lever system 

shall change from the horizontal or midway between limiting stops to either limit of motion. 

(Amended 1987) 

T.N.7. Discrimination.

T.N.7.1. Analog Automatic Indicating (i.e., Weighing Device With Dial, Drum, Fan, Etc.). - A test load 

equivalent to 1.4 d shall cause a change in the indication of at least 1.0 d. (See N.1.5.) 

T.N.7.2. Digital Automatic Indicating. - A test load equivalent to 1.4 d shall cause a change in the indicated or 

recorded value of at least 2.0 d. This requires the zone of uncertainty to be not greater than three-tenths of the value 

of the scale division. (See N.1.5.1.) 

T.N.8. Influence Factors. - The following factors are applicable to tests conducted under controlled conditions only, 

provided that: 

(a) types of devices approved prior to January 1, 1986, and manufactured prior to January 1, 1988, need not meet 

the requirements of this section, and 

(b) new types of devices submitted for approval after January 1, 1986, shall comply with the requirements of this 

section, and 

 

(c) all devices manufactured after January 1, 1988, shall comply with the requirements of this section. 

 (Amended 1985) 

T.N.8.1. Temperature. - Devices shall satisfy the tolerance requirements under the following temperature 

conditions: 

T.N.8.1.1. If not specified in the operating instructions for Class I or II scales, or if not marked on the device for 

Class III, III L, or IIII scales, the temperature limits shall be: 

-10 C to 40 C (14 F to 104 F) 

T.N.8.1.2. If temperature limits are specified for the device, the range shall be at least that specified in Table 

T.N.8.1.2. 

Table T.N.8.1.2. 

Temperature Range by Class 

Class Temperature Range 

I 5 EC (9 F) 

II 15 EC (27 F) 

III, III L, & IIII 30 EC (54 F) 
2.20. Scales 

2-30 

T.N.8.1.3. Temperature Effect on Zero-Load Balance. - The zero-load indication shall not vary by more than: 

(a) three divisions per 5 C (9 F) change in temperature for Class III L devices; or 

(b) one division per 5 C (9 F) change in temperature for all other devices. 

(Amended 1990) 

T.N.8.1.4. Operating Temperature. - Except for Class I and II devices, an indicating or recording element 

shall not display nor record any usable values until the operating temperature necessary for accurate weighing 

and a stable zero balance condition have been attained. 

T.N.8.2. Barometric Pressure. - Except for Class I scales, the zero indication shall not vary by more than one scale 

division for a change in barometric pressure of 1 kPa over the total barometric pressure range of 95 kPa to 105 kPa 

(28 in to 31 in of Hg). 

 T.N.8.3. Electric Power Supply.

T.N.8.3.1. Power Supply, Voltage and Frequency.

(a) Weighing devices that operate using alternating current must perform within the conditions defined in 

paragraphs T.N.3. through T.N.7., inclusive, over the line voltage range of 100 V to 130 V or 200 V to 

250 V rms as appropriate, and over the frequency range of 59.5 Hz to 60.5 Hz. 

(b) Battery operated instruments shall not indicate nor record values outside the applicable tolerance limits 

when battery power output is excessive or deficient. 

T.N.8.3.2. Power Interruption. - A power interruption shall not cause an indicating or recording element to 

display or record any values outside the applicable tolerance limits. 

T.N.9. Radio Frequency Interference (RFI) and Other Electromagnetic Interference Susceptibility. - The difference 

between the weight indication due to the disturbance and the weight indication without the disturbance shall not exceed 

one scale division (d); or the equipment shall: 

(a) blank the indication, or 

(b) provide an error message, or 

(c) the indication shall be so completely unstable that it cannot be interpreted, or transmitted into memory or to a 

recording element, as a correct measurement value. 

The tolerance in T.N.9. is to be applied independently of other tolerances. For example, if indications are at allowable 

basic tolerance error limits when the disturbance occurs, then it is acceptable for the indication to exceed the applicable 

basic tolerances during the disturbance. [Editors' Note: Following the 1997 NCWM Annual Meeting, the text in this 

paragraph was revised with concurrence of the S&T Committee to clarify its application.] 

(Amended 1997) 

UR. User Requirements 

UR.1. Selection Requirements. - Equipment shall be suitable for the service in which it is used with respect to elements 

of its design, including but not limited to, its capacity, number of scale divisions, value of the scale division or 

verification scale division, minimum capacity, and computing capability.4

 

4 Purchasers and users of scales such as railway track, hopper, and vehicle scales should be aware of possible additional 

requirements for the design and installation of such devices. 

(Footnote Added 1995) 
2.20. Scales 

2-31 

UR.1.1. General.

 

(a) For devices marked with a class designation, the typical class or type of device for particular weighing 

applications is shown in Table 7a. 

(b) For devices not marked with a class designation, Table 7b applies. 

Table 7a. 

Typical Class or Type of Device for Weighing Operations

Class Weighing Application or Scale Type 

I Precision laboratory weighing 

II Laboratory weighing, precious metals and gem weighing, grain test scales 

III 

All commercial weighing not otherwise specified, grain test scales, retail precious metals and semi-precious 

gem weighing, animal scales, postal scales, scales used to determine laundry charges, and vehicle on-board 

weighing systems 

III L Vehicle, axle-load, livestock, railway track scales, crane, hopper (other than grain hopper) scales, and 

vehicle on-board weighing systems 

IIII Wheel-load weighers and portable axle-load weighers used for highway weight enforcement 

Note: A scale with a higher accuracy class than that specified as "typical" may be used. 

(Amended 1985, 1986, 1987, 1988, 1992, and 1995) 

Table 7b. 

Applicable to Devices not Marked With a Class Designation

Scale Type or Design Maximum Value of d 

Retail Food Scales, 50-lb capacity and less 1 ounce 

Animal Scales 1 pound 

Grain Hopper Scales 

 Capacity up to and incl. 50 000 lb 

 Capacity over 50 000 lb 

10 pounds (not greater than 0.05 % of capacity) 

20 pounds 

Crane Scales not greater than 0.2 % of capacity 

Vehicle and Axle-Load Scales Used in Combination 

 Capacity up to and including 200 000 lb 

 Capacity over 200 000 lb 

20 pounds 

50 pounds 

Railway Track Scales 

 With weighbeam 

 Automatic indicating 

20 pounds 

100 pounds 

Scales with capacities greater than 500 lb except otherwise specified 0.1 % capacity (but not greater than 50 lb) 

Wheel-Load Weighers 0.25 % capacity (but not greater than 50 lb) 

Note: For scales not specified in this table, G-UR.1.1. and UR.1. apply. 

(Added 1985) (Amended 1989) 

UR.1.2. Grain Hopper Scales. - The minimum number of scale divisions for a Class III Hopper Scale used for 

weighing grain shall be 2000. 
2.20. Scales 

2-32 

UR.1.3. Value of the Indicated and Recorded Scale Division. - The value of the scale division as recorded shall be 

the same as the division value indicated. 

[Nonretroactive as of January 1, 1986] 

(Added 1995) (Amended 1999)

UR.1.3.1. Exceptions. - The provisions of UR.1.3.Value of the Indicated and Recorded Scale Division shall not 

apply to: 

(a) Class I scales, or 

(b) Dynamic monorail weighing systems when the value of d is less than the value of e.

[Nonretroactive as of January 1, 1986]

(Added 1999) 

UR.1.4. Grain-Test Scales: Value of the Scale Divisions. - The scale division for grain-test scales shall not exceed 

0.2 g for loads through 500 g, and shall not exceed 1 g for loads above 500 g through 1000 g. 

(Added 1992) 

UR.1.5. Recording Element, Class III L Railway Track Scales. - Class III L Railway Track Scales must be 

equipped with a recording element. [Nonretroactive as of January 1, 1996]

(Added 1995) 

UR.2. Installation Requirements.

UR.2.1. Supports. - A scale that is portable and that is being used on a counter, table, or the floor shall be so 

positioned that it is firmly and securely supported. 

UR.2.2. Suspension of Hanging Scale. - A hanging scale shall be freely suspended from a fixed support when in 

use. 

UR.2.3. Protection From Environmental Factors. - The indicating elements, the lever system or load cells, and 

the load-receiving element of a permanently installed scale, and the indicating elements of a scale not intended to be 

permanently installed, shall be adequately protected from environmental factors such as wind, weather, and RFI that 

may adversely affect the operation or performance of the device. 

UR.2.4. Foundation, Supports, and Clearance. - The foundation and supports of any scale installed in a fixed 

location shall be such as to provide strength, rigidity, and permanence of all components, and clearance shall be 

provided around all live parts to the extent that no contacts may result when the load-receiving element is empty, nor 

throughout the weighing range of the scale. On vehicle and livestock scales, the clearance between the 

load-receiving elements and the coping at the bottom edge of the platform shall be greater than at the top edge of the 

platform. 

[Nonretroactive as of January 1, 1973]

UR.2.5. Access to Weighing Elements. - Adequate provision shall be made for ready access to the pit of a vehicle, 

livestock, animal, axle-load, or railway track scale for the purpose of inspection and maintenance. Any of these 

scales without a pit shall be installed with adequate means for inspection and maintenance of the weighing elements. 

(Amended 1985) 

 UR.2.6. Approaches.

UR.2.6.1. Vehicle Scales. - On the entrance and exit ends of a vehicle scale installed in any one location for a 

period of 6 months or more, there shall be a straight approach as follows: 

(a) the width at least the width of the platform, 

(b) the length at least one-half the length of the platform but not required to be more than 12 m (40 ft), and 
2.20. Scales 

2-33 

(c) not less than 3 m (10 ft) of any approach adjacent to the platform shall be constructed of concrete or 

similar durable material to ensure that this portion remains smooth and level and in the same plane as 

the platform. However, grating of sufficient strength to withstand all loads equal to the concentrated 

load capacity of the scale may be installed in this portion. Any slope in the remaining portion of the 

approach shall ensure (1) ease of vehicle access, (2) ease for testing purposes, and (3) drainage away 

from the scale. 

[Nonretroactive as of 1976]

 (Amended 1977, 1983, and 1993) 

UR.2.6.2. Axle-Load Scales. - At each end of an axle-load scale there shall be a straight paved approach in the 

same plane as the platform. The approaches shall be the same width as the platform and of sufficient length to 

insure the level positioning of vehicles during weight determinations. 

UR.2.7. Stock Racks. - A livestock or animal scale shall be equipped with a suitable stock rack, with gates as 

required, which shall be securely mounted on the scale platform. Adequate clearances shall be maintained around the 

outside of the rack. 

UR.2.8. Hoists. - On vehicle scales equipped with means for raising the load-receiving element from the weighing 

element for vehicle unloading, means shall be provided so that it is readily apparent to the scale operator when the 

load receiving element is in its designed weighing position. 

UR.2.9. Provision for Testing Dynamic Monorail Weighing Systems. - Provisions shall be made at the time of 

installation of a dynamic monorail weighing systems for testing in accordance with N.1.3.6.1. (a rail around or other 

means for returning the test carcasses to the scale being tested). 

[Nonretroactive as of January 1, 1998] 

 (Added 1997) (Amended 1999)

UR.3. Use Requirements.

UR.3.1. Recommended Minimum Load. - A recommended minimum load is specified in Table 8 since the use of a 

device to weigh light loads is likely to result in relatively large errors. 

Table 8. 

Recommended Minimum Load

Class Value of scale division 

(d or e*) 

Recommended minimum load 

(d or e*) 

I equal to or greater than 0.001 g 100 

II 0.001 g to 0.05 g, inclusive 20 

equal to or greater than 0.1 g 50 

III All** 20 

III L All 50 

IIII All 10 

*For Class I and II devices equipped with auxiliary reading means (i.e., a rider, a vernier, or a least significant decimal differentiated by size, shape or color), the value of the verification scale division "e" is the value 

of the scale division immediately preceding the auxiliary means. For Class III and IIII devices the value of 

"e" is specified by the manufacturer as marked on the device; "e" must be less than or equal to "d." 

**A minimum load of 10 d is recommended for a weight classifier marked in accordance with a statement 

identifying its use for special applications. 

(Amended 1990) 

UR.3.1.1. Minimum Load, Grain Dockage Determination. - When determining the quantity of foreign 

material (dockage) in grain, the weight of the sample shall be equal to or greater than 500 scale divisions. 

(Added 1985) 
2.20. Scales 

2-34 

UR.3.2. Maximum Load. - A scale shall not be used to weigh a load of more than the nominal capacity of the scale. 

UR.3.2.1. Maximum Loading for Vehicle Scales. - A vehicle scale shall not be used to weigh loads exceeding 

the maximum load capacity of its span as specified in Table UR.3.2.1. 

(Added 1996) 

UR.3.3. Single-Draft Vehicle Weighing. - A vehicle or a coupled vehicle combination shall be commercially 

weighed on a vehicle scale only as a single draft. That is, the total weight of such a vehicle or combination shall not 

be determined by adding together the results obtained by separately and not simultaneously weighing each end of 

such vehicle or individual elements of such coupled combination. However: 

(a) the weight of a coupled combination may be determined by uncoupling the various elements (tractor, 

semitrailer, trailer), weighing each unit separately as a single draft, and adding together the results, or 

(b) the weight of a vehicle or coupled-vehicle combination may be determined by adding together the weights 

obtained while all individual elements are resting simultaneously on more than one scale platform. 

Note: This paragraph does not apply to highway-law-enforcement scales and scales used for the collection of 

statistical data. 

(Added 1992) 

 UR.3.4. Wheel-Load Weighing.

UR.3.4.1. Use in Pairs. - When wheel-load weighers or portable axle-load weighers are to be regularly used in 

pairs, both weighers of each such pair shall be appropriately marked to identify them as weighers intended to be 

used in combination. 

UR.3.4.2. Level Condition. - A vehicle of which either an axle-load determination or a gross-load determination 

is being made utilizing wheel-load weighers or portable axle-load weighers, shall be in a reasonably level 

position at the time of such determination. 

 

UR.3.5. Special Designs. - A scale designed and marked for a special application (such as a prepackaging scale) 

shall not be used for other than its intended purpose5

. 

UR.3.6. Wet Commodities. - Wet commodities not in watertight containers shall be weighed only on a scale having 

a pan or platform that will drain properly. 

(Amended 1988) 

UR.3.7. Minimum Load on a Vehicle Scale. - A vehicle scale shall not be used to weigh net loads smaller than: 

(a) 10 d when weighing scrap material for recycling; 

(b) 50 d for all other weighing. 

As used in this paragraph, scrap materials for recycling shall be limited to ferrous metals, paper (including 

cardboard), textiles, plastic, and glass. 

(Amended 1988 and 1992) 

 

5 Prepackaging scales (and other commercial devices) used for putting up packages in advance of sale are acceptable for 

use in commerce if all appropriate provisions of Handbook 44 are met. Users of such devices must be alert to the legal 

requirements relating to the declaration of quantity on a package. Such requirements are to the effect that, on the average, 

the contents of the individual packages of a particular commodity comprising a lot, shipment, or delivery must contain at 

least the quantity declared on the label. The fact that a prepackaging scale may overregister, but within established 

tolerances, and is approved for commercial service is not a legal justification for packages to contain, on the average, less 

than the labeled quantity.
2.20. Scales 

2-35 

UR.3.8. Minimum Load for Weighing Livestock. - A scale with scale divisions greater than 2 kg (5 lb) shall not 

be used for weighing net loads smaller than 500 d. 

(Amended 1989) 

UR.3.9. Use of Manual Gross Weight Entries. - Manual gross weight entries are permitted for use in the 

following applications only: (1) when credit is given for a weighed item on point-of-sale systems interfaced with 

scales; (2) when a device or system generates labels for standard weight packages; (3) when postal scales or weight 

classifiers generate manifests for packages to be picked up at a later time; or (4) when livestock and vehicle scale 

systems generate weight tickets to correct erroneous tickets. 

(Added 1992) (Amended 2000) 

UR.3.10. Dynamic Monorail Weighing Systems. - When the value of d is different from the value of e, the 

commercial transaction must be based on e. 

(Added 1999) 

UR.4. Maintenance Requirements.

UR.4.1. Balance Condition. - The zero-load adjustment of a scale shall be maintained so that, with no load on the 

load-receiving element and with all load-counterbalancing elements of the scale (such as poises, drop weights, or 

counterbalance weights) set to zero, the scale shall indicate or record a zero balance condition. A scale not equipped 

to indicate or record a zero-load balance shall be maintained in balance under any no-load condition. 

UR.4.2. Level Condition. - If a scale is equipped with a level-condition indicator, the scale shall be maintained in 

level. 

UR.4.3. Scale Modification. - The dimensions (e.g., length, width, thickness, etc.) of the load receiving element of a 

scale shall not be changed beyond the manufacturer’s specifications, nor shall the capacity of a scale be increased 

beyond its design capacity by replacing or modifying the original primary indicating or recording element with one 

of a higher capacity, except when the modification has been approved by a competent engineering authority, 

preferably that of the engineering department of the manufacturer of the scale, and by the weights and measures 

authority having jurisdiction over the scale. 

(Amended 1996) 

UR.5. Coupled-in-Motion Railroad Weighing Systems. - A coupled-in-motion weighing system placed in service on 

or after January 1, 1991, should be tested in the manner in which it is operated, with the locomotive either pushing or 

pulling the cars at the designed speed and in the proper direction. The cars used in the test train should represent the 

range of gross weights that will be used during the normal operation of the weighing system. Except as provided in 

N.4.2. and N.4.3.(a), normal operating procedures should be simulated as nearly as practical. Approach conditions for a 

train length in each direction of the scale site are more critical for a weighing system used for individual car weights than 

for a unit-train-weights-only facility, and should be considered prior to installation. 

(Added 1990) (Amended 1992) 
2.20. Scales 

2-36 

Table UR.3.2.1. 

Span Maximum Load 

Distance in feet 

between the 

extremes of any 

two or more 

consecutive axles 

Ratio of CLC to maximum Load (“r” factor) carried on any 

group of 2 or more consecutive axles. 

2 axles 3 axles 4 axles 5 axles 6 axles 7 axles 8 axles 9 axles 

41 1.000 INSTRUCTIONS: 

1. Determine the scale’s CLC. 

2. Count the number of axles on the vehicle in a given span and 

determine the distance in feet between the first and last axle in the 

span. 

3. Multiply the CLC by the corresponding multiplier in the table*. 

4. The resulting number is the scale's maximum concentrated load for a 

single span based on the vehicle configuration. 

*See note and formula on next page. 

51 1.000 

61 1.000 

71 1.000 

8 and less1 1.000 1.000 

More than 81 1.118 1.235 

9 1.147 1.257 

10 1.176 1.279 

11 1.206 1.301 

12 1.235 1.324 1.471 1.632 

13 1.265 1.346 1.490 1.651 

14 1.294 1.368 1.510 1.669 

15 1.324 1.390 1.529 1.688 1.853 

16 1.353 1.412 1.549 1.706 1.871 

17 1.382 1.434 1.569 1.724 1.888 

18 1.412 1.456 1.588 1.743 1.906 

19 1.441 1.478 1.608 1.761 1.924 

20 1.471 1.500 1.627 1.779 1.941 

21 1.500 1.522 1.647 1.798 1.959 

22 1.529 1.544 1.667 1.816 1.976 

23 1.559 1.566 1.686 1.835 1.994 

24 1.588 1.588 1.706 1.853 2.012 2.176 

25 1.618 1.610 1.725 1.871 2.029 2.194 

26 1.632 1.745 1.890 2.047 2.211 

27 1.654 1.765 1.908 2.065 2.228 

28 1.676 1.784 1.926 2.082 2.245 2.412 

29 1.699 1.804 1.945 2.100 2.262 2.429 

30 1.721 1.824 1.963 2.118 2.279 2.445 

31 1.743 1.843 1.982 2.135 2.297 2.462 

32 1.765 1.863 2.000 2.153 2.314 2.479 2.647 

33 1.882 2.018 2.171 2.331 2.496 2.664 

34 1.902 2.037 2.188 2.348 2.513 2.680 

35 1.922 2.055 2.206 2.365 2.529 2.697 

36 2.0002 2.074 2.224 2.382 2.546 2.713 

37 2.0002 2.092 2.241 2.400 2.563 2.730 

38 2.0002 2.110 2.259 2.417 2.580 2.746 

39 2.000 2.129 2.276 2.434 2.597 2.763 

40 2.020 2.147 2.294 2.451 2.613 2.779 

41 2.039 2.165 2.312 2.468 2.630 2.796 

42 2.059 2.184 2.329 2.485 2.647 2.813 

43 2.078 2.202 2.347 2.502 2.664 2.829 

44 2.098 2.221 2.365 2.520 2.681 2.846 

45 2.118 2.239 2.382 2.537 2.697 2.862 

46 2.137 2.257 2.400 2.554 2.714 2.879 

47 2.157 2.276 2.418 2.571 2.731 2.895 
2.20. Scales 

2-37 

Table UR.3.2.1. 

Span Maximum Load 

Distance in feet 

between the 

extremes of any 

two or more 

consecutive axles 

Ratio of CLC to maximum Load (“r” factor) carried on any 

group of 2 or more consecutive axles. 

2 axles 3 axles 4 axles 5 axles 6 axles 7 axles 8 axles 9 axles 

48 2.176 2.294 2.435 2.588 2.748 2.912 

49 2.196 2.313 2.453 2.605 2.765 2.928 

50 2.216 2.331 2.471 2.623 2.782 2.945 

51 2.235 2.349 2.488 2.640 2.798 2.961 

52 2.255 2.368 2.506 2.657 2.815 2.978 

53 2.275 2.386 2.524 2.674 2.832 2.994 

54 2.294 2.404 2.541 2.691 2.849 3.011 

55 2.314 2.423 2.559 2.708 2.866 3.028 

56 2.333 2.441 2.576 2.725 2.882 3.044 

57 2.3533 2.460 2.594 2.742 2.899 3.061 

58 2.478 2.612 2.760 2.916 3.077 

59 2.496 2.629 2.777 2.933 3.094 

60 2.515 2.647 2.794 2.950 3.110 

*Note: This table was developed based upon the following formula. Values may be rounded in some cases for ease of 

use. 



 



   

 





  36 12 1

 500 N

N

LN rW

1 Tandem Axle Weight. 2 Exception - These values in the third column correspond to the maximum loads in which the inner bridge dimensions 

of 36, 37, and 38 feet are considered to be equivalent to 39 feet. This allows a weight of 68 000 lb on axles 2 through 5. 3

 Corresponds to the Interstate Gross Weight Limit. 
2.20. Scales 

2-38 

Scales Code Index 

Acceptance ..................................... 10, 23, 25, 26, 27, 28 

Acceptance tolerance ........................... 10, 25, 26, 27, 28 

Accuracy ...................... 10, 11, 12, 13, 15, 16, 23, 26, 31 

Accuracy class ................... 10, 12, 13, 15, 16, 23, 26, 31 

Adjustable components ............................................ 8, 12 

Adjustment ............................................... 8, 9, 12, 22, 35 

Approaches ............................................................ 32, 33 

Audit trail ....................................................................... 8 

Automatic indicating scales ............................. 18, 20, 24 

Automatic zero-setting mechanism .......................... 9, 13 

Axle-load scales ......................... 3, 10, 11, 18, 24, 31, 33 

Balance condition .............................. 3, 9, 10, 26, 30, 35 

Balance indicator ............................. 3, 10, 11, 25, 28, 29 

Balance indicators .................................................. 25, 28 

Balance position ............................................................. 5 

Barometric pressure ............................................... 26, 30 

Capacity 5, 6, 8, 9, 10, 11, 12, 13, 14, 15, 16, 18, 19, 20, 

21, 23, 24, 25, 26, 28, 29, 30, 31, 33, 34, 35 

Capacity indication ........................................................ 6 

Center-of-zero ................................................................ 3 

Certificate of Conformance .......................................... 13 

Class .... 4, 8, 9, 10, 11, 12, 13, 15, 16, 18, 20, 24, 26, 27, 

29, 30, 31, 32, 33 

CLC...................................................... 14, 15, 16, 18, 36 

Clearance ........................................................... 5, 10, 32 

Computing scale ........................................................ 6, 7 

Concentrated Load Capacity ........................................ 15 

Consecutive-car test ......................................... 21, 22, 23 

Coupled-in-motion ................................................. 27, 35 

Coupled-in-motion railroad weighing systems ............ 27 

Crane and hopper (other than grain hopper) ................ 13 

Crane scales ........................................................... 20, 31 

Dairy-product-test ...................................... 10, 11, 18, 23 

Damping means ........................................................... 11 

Decreasing load test ............................................... 24, 26 

Direct sales ................................................. 5, 7, 9, 10, 12 

Discrimination test ....................................................... 20 

Distributed-car test ....................................................... 22 

Electric power supply .................................................. 30 

Environmental factors ............................................ 20, 32 

Foundation ................................................................... 32 

Graduations .................................................. 4, 5, 6, 7, 10 

Grain test scales ........................................................... 31 

Grain-test ............................................................... 10, 32 

Hanging scale ......................................................... 20, 32 

Hanging scales ............................................................. 20 

Hoists ........................................................................... 33 

Hopper scales ................................................... 20, 26, 31 

I 4, 8, 9, 10, 11, 12, 13, 16, 18, 23, 24, 26, 27, 28, 29, 

30, 31, 32, 33 

II 4, 9, 10, 11, 12, 13, 16, 18, 23, 24, 26, 27, 28, 29, 30, 

31, 33 

III 4, 9, 10, 12, 13, 16, 18, 23, 24, 26, 27, 28, 29, 30, 31, 

32, 33 

III L .. 9, 12, 13, 16, 23, 24, 26, 27, 28, 29, 30, 31, 32, 33 

IIII ................ 4, 12, 13, 16, 18, 23, 26, 27, 28, 29, 31, 33 

Index of an indicator .................................................. 4, 5 

Indicating element ............... 3, 11, 14, 15, 16, 27, 28, 32 

Indicator ... 3, 4, 5, 6, 8, 10, 11, 13, 16, 25, 26, 28, 29, 35 

Influence factors .................................................... 26, 29 

Initial verification .................................................. 21, 22 

Initial zero-setting mechanism ................................. 6, 10 

Installation requirements ............................................. 32 

Level .......................................... 9, 10, 11, 19, 33, 34, 35 

Level condition ................................................ 11, 34, 35 

Level-indicating means ................................................ 10 

Livestock scales ........................................... 9, 14, 16, 32 

Load cell .............................................. 12, 14, 15, 16, 32 

Load cell verification interval ................................ 12, 16 

Main elements ....................................................... 14, 27 

Maintenance ...................... 23, 24, 25, 26, 27, 28, 32, 35 

Maintenance requirements ........................................... 35 

Maintenance tolerance ......................... 23, 24, 26, 27, 28 

Manual gross weight entries .................................... 9, 35 

Marking requirements ........................................ 14, 15 

Material test ........................................................... 20, 24 

Minimum load ................................................. 33, 34, 35 

Minimum test weights ........................................... 20, 21 

Money-value computation ............................................. 7 

Money-value graduations .......................................... 6, 7 

Monorail scale ............................................. 4, 10, 19, 24 

Multi-interval ............................................. 12, 13, 16, 26 

Multiple Range ...................................................... 12, 26 

No-load reference value ................................................. 3 

Nominal capacity ........... 5, 14, 15, 16, 18, 19, 23, 25, 34 

Operating temperature ........................................... 26, 30 

Parallax .......................................................................... 5 

Parcel post scales ............................................. 23, 24, 25 

Poise .......................................................................... 5, 6 

Portable axle-load weighers ................... 3, 20, 26, 31, 34 

Postal ..................................... 4, 6, 16, 23, 24, 25, 31, 35 

Power interruption ....................................................... 30 

Prepackaging scale .................................................. 8, 34 

Prescription .......................................... 10, 11, 13, 23, 24 

Railway track scales ...... 9, 11, 14, 16, 19, 20, 25, 31, 32 

Ratio test ................................................................ 20, 26 

Readability ..................................................................... 5 

Recorded representations ........................................... 3, 7 

Recording elements ........................................... 3, 11, 28 

Repeatability ................................................................ 28 

RFI ............................................................. 20, 25, 30, 32 

Scale modification ....................................................... 35 

Sealing ........................................................................... 8 

Security seal ................................................................... 8 

Sensitivity requirement .......................................... 23, 25 

Sensitivity test ............................................................. 20 

Shift test ..................................................... 18, 19, 20, 28 

Stock racks ................................................................... 33 

Strain-load test ............................................................. 20 

Subsequent verification ......................................... 22, 26 

Supports ................................................................. 18, 32 

Symmetry ...................................................................... 4 
2.20. Scales 

2-39 

Tare .................................................................... 9, 10, 26 

Temperature ................................... 13, 15, 16, 26, 29, 30 

Test loads ..................... 18, 19, 20, 21, 24, 25, 26, 27, 28 

Time dependence ......................................................... 28 

Tolerances ........ 10, 11, 19, 20, 21, 23, 24, 26, 28, 30, 34 

Travel ................................................................. 5, 11, 23 

Type evaluation .......................................... 13, 14, 26, 27 

Uncoupled-in-motion ................................................... 23 

Uncoupled-in-motion railroad weighing system .......... 23 

Unit weights ....................................................... 6, 16, 28 

Use requirements ......................................................... 33 

Vehicle on-board weighing system ............. 9, 11, 19, 31 

Vehicle scale ........................ 9, 14, 18, 30, 32, 33, 34, 35 

Vehicle scales .................................. 9, 18, 30, 32, 33, 34 

Verification scale interval ........................................ 4, 12 

Weighing elements .................................... 12, 18, 19, 32 

Weight ranges .......................................................... 6, 16 

Weight units ................................................................... 4 

Wheel-load weighers ................. 3, 10, 11, 20, 26, 31, 34 

Zero indication ......................................................... 3, 30 

Zero-load adjustment ............................................... 9, 35 

Zero-load balance .............................. 8, 9, 10, 20, 30, 35 
2.20. Scales 

2-40 
2.21. Belt-Conveyor Scale Systems

2-41

Sec. 2.21. Belt-Conveyor Scale Systems

A. Application

A.1. This code applies to belt-conveyor scale systems used for the weighing of bulk materials.

A.2. The code does not apply to:

(a) devices used for discrete weighing while moving on conveyors;

(b) devices that measure quantity on a time basis;

(c) check-weighers; or

(d) controllers or other auxiliary devices except as they may affect the weighing performance of the belt-conveyor 

scale.

A.3. See also General Code requirements.

S. Specifications

S.1. Design of Indicating and Recording Elements.

S.1.1. General. - A belt-conveyor scale shall be equipped with a primary indicating element in the form of a master 

weight totalizer and shall also be equipped with a recording element, and a rate of flow indicator and recorder 

(which may be analog). * An auxiliary indicator shall not be considered part of the master weight totalizer.

*[Nonretroactive as of January 1, 1986]

(Amended 1986)

 

S.1.2. Units. - A belt-conveyor scale shall indicate and record weight units in terms of pounds, tons, long tons, 

metric tons, or kilograms. The value of a scale division (d) expressed in a unit of weight shall be equal to:

(a) 2, or 5, or

(b) a decimal multiple or submultiples of 1, 2, or 5.

S.1.3. Value of the Scale Division.

S.1.3.1. For Scales Installed After January 1, 1986. - The value of the scale division shall not be greater than 

0.1 percent (1/1000) of the minimum totalized load. 

[Nonretroactive as of January 1, 1986]

S.1.3.2. For Scales Installed Before January 1, 1986. - The value of the scale division shall not be greater than 

1/1200 of the rated capacity of the device. However, provision shall be made so that compliance with the 

requirements of the zero-load test as prescribed in N.3.1. may be readily and accurately determined in 

20 minutes of operation.

S.1.4. Recording Elements and Recorded Representations. - The value of the scale division of the recording 

element shall be the same as that of the indicating element. The belt-conveyor scale system shall record the initial 

indication and the final indication of the master weight totalizer*, the quantity delivered*, the unit of measurement 

(i.e., kilograms, tonnes, pounds, tons, etc.), the date, and time. This information shall be recorded for each delivery.*

[Nonretroactive as of January 1, 1986]

[*Nonretroactive as of January 1, 1994]

(Amended 1993)
2.21. Belt-Conveyor Scale Systems

2-42

S.1.4.1. The belt-conveyor scale system shall be capable of recording the results of automatic or semi-automatic 

zero load tests.**

[**Nonretroactive as of January 1, 2004]

(Added 2002)

S.1.5. Rate of Flow Indicators and Recorders. - A belt-conveyor scale shall be equipped with a rate of flow 

indicator and an analog or digital recorder. Permanent means shall be provided to produce an audio or visual 

signal when the rate of flow is equal to or less than 35 percent and when the rate of flow is equal to or greater than 

98 percent of the rated capacity of the scale. The type of alarm (audio or visual) shall be determined by the 

individual installation.

[Nonretroactive as of January 1, 1986]

(Amended 1989)

S.1.6. Advancement of Primary Indicating or Recording Elements. - The master weight totalizer shall advance 

only when the belt conveyor is in operation and under load.

(Amended 1989)

S.1.7. Master Weight Totalizer. - The master weight totalizer shall not be resettable without breaking a security 

means.

[Nonretroactive as of January 1, 1986]

 

S.1.8. Power Loss. - In the event of a power failure of up to 24 hours, the accumulated measured quantity on the 

master weight totalizer of an electronic digital indicator shall be retained in memory during the power loss.

[Nonretroactive as of January 1, 1986]

(Amended 1989)

S.2. Design of Weighing Elements. - A belt-conveyor scale system shall be designed to combine automatically belt 

travel with belt load to provide a determination of the weight of the material that has passed over the scale.

S.2.1. Speed Measurement. - A belt-conveyor scale shall be equipped with a belt speed or travel sensor that will 

accurately sense the belt speed or travel whether the belt is empty or loaded.

 

S.2.2. Adjustable Components. - An adjustable component that can affect the performance of the device (except as 

prescribed in S.3.1.) shall be held securely in adjustment.

(Amended 1998)

S.2.3. Overload Protection. - The load-receiving elements shall be equipped with means for overload protection of 

not less than 150 percent of rated capacity. The accuracy of the scale in its normal loading range shall not be affected 

by overloading.

S.3. Zero Setting.

S.3.1. Design of Zero-Setting Mechanism. - Automatic and semiautomatic zero-setting mechanisms shall be so 

constructed that the resetting operation is carried out only after a whole number of belt revolutions and the 

completion of the setting or the whole operation is indicated. An audio or visual signal shall be given when the 

automatic and semiautomatic zero-setting mechanisms reach the limit of adjustment of the zero-setting mechanism.*

(Amended 1999 and 2002)

Except for systems that do not record the zero load reference at the beginning and end of a delivery, the range of the 

zero-setting mechanism shall not be greater than ±2 percent of the rated capacity of the scale without breaking the 

security means. For systems that record the zero load reference at the beginning and end of a delivery, the range of 

zero-setting mechanism shall not be greater than ± 5 percent without breaking the security means.**

[*Nonretroactive as of January 1, 1990]

[**Nonretroactive as of January 1, 2004]

(Amended 1989 and 2002) 
2.21. Belt-Conveyor Scale Systems

2-43

S.3.2. Sensitivity at Zero Load (For Type Evaluation). - When a system is operated for a time period equal to the 

time required to deliver the minimum test load and with a test load calculated to indicate two scale divisions applied 

directly to the weighing element, the totalizer shall advance not less than one or more than three scale divisions. An 

alternative test of equivalent sensitivity, as specified by the manufacturer, shall also be acceptable.

[Nonretroactive as of January 1, 1986]

S.4. Marking Requirements. - A belt-conveyor scale shall be marked with the following: (Also see G-S.1.)

(a) the rated capacity in units of weight per hour (minimum and maximum);

(b) the value of the scale division;

(c) the belt speed in terms of feet (or meters) per minute at which the belt will deliver the rated capacity;

(d) the load in terms of pounds per foot or kilograms per meter (determined by materials tests);

(e) the operational temperature range if other than -10 °C to 40 °C (14 °F to 104 °F). 

[Nonretroactive as of January 1, 1986]

S.5. Provision for Sealing. - A device shall be designed using the format set forth in Table S.5. with provision(s) for 

applying a security seal that must be broken, or for using other approved means of providing security (e.g. data change 

audit trail available at the time of inspection), before any change that affects the metrological integrity of the device can

be made to any electronic mechanism.

[Nonretroactive as of January 1, 1999]

(Added 1998)

Table S.5. Categories of Device and Methods of Sealing

Categories of Devices Method of Sealing

Category 1: No remote configuration capability.

Seal by physical seal or two event counters: one for calibration 

parameters and one for configuration parameters.

Category 3: Remote configuration capability.

An event logger is required in the device; it must include an event 

counter (000 to 999), the parameter ID, the date and time of the 

change, and the new value of the parameter. A printed copy of the 

information must be available through the device or through another 

on-site device. The event logger shall have a capacity to retain 

records equal to ten times the number of sealable parameters in the 

device, but not more than 1000 records are required. (Note: Does not 

require 1000 changes to be stored for each parameter.)

[Nonretroactive as of January 1, 1998] (Table Added 1998)

N. Notes

N.1. General. - Belt-conveyor scales are capable of weighing bulk material accurately. (See Tolerances.) However, their 

performance can be detrimentally affected by the conditions of the installation. (See User Requirements.) The 

performance of the equipment is not to be determined by averaging the results of the individual tests. The results of all 

tests shall be within the tolerance limits.

(Amended 2002)

N.1.1. Official Test. - An official test of a belt-conveyor scale system shall be a materials test.

N.1.2. Simulated Test. - Simulated loading conditions as recommended by the manufacturer and approved by the 

official with statutory authority may be used to properly monitor the system operational performance between official 

tests, but shall not be used for official certification.

(Amended 1991)
2.21. Belt-Conveyor Scale Systems

2-44

N.2. Conditions of Tests. - A belt-conveyor scale shall be tested after it is installed on the conveyor system with which it 

is to be used and under such environmental conditions as may normally be expected. It shall be tested at normal use 

capacity and may also be tested at any other rate of flow that may be used at the installation. Each test shall be conducted 

for:

(a) not less than 1000 scale divisions,

(b) at least three revolutions of the belt, and

(c) at least 10 minutes of operation, or for a normal weighment.

(Amended 1986)

N.3. Test Procedures.

N.3.1. Zero Load Tests. - A zero-load test shall be conducted to establish that the belt scale system (including the 

conveyor) is capable of holding a stable, in-service zero.

(Amended 1989 and 2002)

N.3.1.1. Determination of Zero. - A “Zero-Load Test” is a determination of the error in zero, expressed as an 

internal reference, a percentage of the full-scale capacity, or a change in a totalized load over a whole number of 

complete belt revolutions. For belt-conveyor scales with electronic integrators, the test must be performed over 

a period of at least 3 minutes and with a whole number of complete belt revolutions. For belt-conveyor scales 

with mechanical integrators, the test shall be performed with no less than three complete revolutions or 

10 minutes operation, whichever is greater.

(Added 2002)

N.3.1.2. Initial Stable Zero. - The conveyor system shall be run to warm up the belt and the belt scale shall be 

zero adjusted as required. A series of zero-load tests shall be carried out until three consecutive zero-load tests 

each indicate an error which does not exceed 0.06 % of the full-scale capacity or 1 division, whichever is less. 

No adjustments can be made during the three consecutive zero-load test readings.

(Added 2002)

N.3.1.3. Test of Zero Stability. - The conveyor system shall be run to warm up the belt and the belt scale shall 

be zero adjusted as required. A series of zero-load tests shall be carried out immediately before the simulated or 

materials test until the three consecutive zero-load tests each indicate an error which does not exceed 0.06 % of 

the full-scale capacity or 1 division, whichever is less. No adjustments can be made during the three 

consecutive zero-load test readings.

Immediately after material has been weighed over the belt-conveyor scale during the conduct of the materials 

test, the zero-load test shall be repeated. The zero error from this test shall not exceed 0.12 % of the full-scale 

capacity or 2 divisions, whichever is less.

(Added 2002)

N.3.1.4. Check For Consistency of the Conveyor Belt Along Its Entire Length. - After a zero-load test with 

flow rate filtering disabled, the totalizer shall not change more than three scale divisions from its initial 

indication during one complete belt revolution. 

(Added 2002)

N.3.2. Material Tests. – Material tests should be conducted using actual belt loading conditions. These belt loading 

conditions shall include, but are not limited to conducting materials tests using different belt loading points, all types 

and sizes of products weighed on the scale, at least one other belt speed, and in both directions of weighing.

On initial verification, at least three individual tests shall be conducted. On subsequent verifications, at least two 

individual tests shall be conducted. The results of all these tests shall be within the tolerance limits.

Either pass a quantity of pre-weighed material over the belt-conveyor scale in a manner as similar as feasible to 

actual loading conditions, or weigh all material that has passed over the belt-conveyor scale. Means for weighing the 
2.21. Belt-Conveyor Scale Systems

2-45

material test load will depend on the capacity of the belt-conveyor scale and availability of a suitable scale for the 

test. To assure that the test load is accurately weighed and determined, the following precautions shall be observed:

(Amended 2002)

(a) The containers, whether railroad cars, trucks, or boxes, must not leak, and shall not be overloaded to the 

point that material will be lost.

(b) The actual empty or tare weight of the containers shall be determined at the time of the test. Stenciled tare 

weight of railway cars or trucks shall not be used. Gross and tare weights shall be determined on the same 

scale.

(c) When a pre-weighed test load is passed over the scale, the belt-loading hopper shall be examined before and 

after the test to assure that the hopper is empty and that only the material of the test load has passed over the 

scale.

(d) Where practicable, a reference scale should be tested within 24 hours preceding the determination of the 

weight of the test load used for a belt-conveyor scale material test.

A reference scale which is not "as found" within maintenance tolerance should have its accuracy re-verified 

after the belt-conveyor test with a suitable known weight load if the "as found" error of the belt-conveyor 

scale material test exceeds maintenance tolerance values. 

(e) If any suitable known weight load other than a certified test weight load is used for re-verification of the 

reference scale accuracy, its weight shall be determined on the reference scale after the reference scale 

certification and before commencing the belt scale material test.

Note: Even if the reference scale is within maintenance tolerance it may require adjusting to be able to meet 

paragraph N.3.2.1.

(f) The test shall not be conducted if the weight of the test load has been affected by environmental conditions.

(Amended 1986, 1989, 1998, 2000, and 2002)

N.3.2.1. Accuracy of Material. - The quantity of material used to conduct a material test shall be weighed on a 

reference scale to an accuracy within 0.1 percent. Scales typically used for this purpose include Class III and III 

L scales or a scale without a class designation as described in Handbook 44, Section 2.20., Table T.1.1.

(Added 1989) (Amended 1991, 1993, 1998 and 2000)

N.3.3. Simulated Load Tests. -

(a) As required by the official with statutory authority, simulated load tests as recommended by the 

manufacturer are to be conducted between material tests to monitor the system's operational performance, 

but shall not be used for official certification.

(Amended 1991)

(b) A simulated load test consisting of at least three consecutive test runs shall be conducted as soon as possible, 

but not more than 12 hours after the completion of the material test, to establish the factor to relate the 

results of the simulated load test to the results of the material tests.

(Added 1990)

(c) The results of the simulated load test shall repeat within 0.1 percent.

(Added 1990) 

(Amended 1989 and 1990)
2.21. Belt-Conveyor Scale Systems

2-46

T. Tolerances

T.1. Tolerance Values1

(Amended 1993)

. - Maintenance and acceptance tolerances on materials tests, relative to the weight of the 

material, shall be ± 0.25 percent of the test load.

T.2. Tolerance Values, Repeatability Tests. - The variation in the values obtained during the conduct of materials tests 

shall not be greater than 0.25 percent (1/400).

T.3. Influence Factors. - The following factors are applicable to tests conducted under controlled conditions only, 

provided that:

(a) types of devices approved prior to January 1, 1986, and manufactured prior to January 1, 1988, need not meet the 

requirements of this Section; and 

(b) new types of devices submitted for approval after January 1, 1986, shall comply with the requirements of the 

Section; and 

(c) all devices manufactured after January 1, 1988, shall comply with the requirements of this Section.

T.3.1. Temperature. - Devices shall satisfy the tolerance requirements at temperatures from -10 °C to 40 °C 

(14 °F to 104 °F).

T.3.1.1. Effect on Zero-Load Balance. - The zero-load indication shall not change by more than 0.07 percent 

of the rated capacity of the scale (without the belt) for a change in temperature of 10 °C (18 °F) at a rate not to 

exceed 5 °C (9 °F) per hour.

T.3.1.2. Temperature Limits. - If a temperature range other than -10 °C to 40 °C (14 °F to 104 °F) is specified 

for the device, the range shall be at least 30°C (54 °F).

[Nonretroactive as of January 1, 1990] (Added 1989)

T.3.2. Power Supply, Voltage, and Frequency. - A belt-conveyor scale system shall satisfy the tolerance 

requirements over a range of 100 V to 130 V or 200 V to 250 V as appropriate and over a frequency range of 59.5 Hz 

to 60.5 Hz.

UR. User Requirements

UR.1. Use Requirements. - A belt-conveyor scale system shall be operated between 35 percent and 98 percent of its 

rated capacity.

UR.1.1. Minimum Totalized Load. - Delivered quantities of less than the minimum test load shall not be 

considered a valid weighment.

UR.1.2. Security Means. - When a security means has been broken, it shall be reported to the official with statutory 

authority.

(Amended 1991)

UR.2. Installation Requirements.

UR.2.1. Protection from Environmental Factors. - The indicating elements, the lever system or load cells, and the 

load-receiving element of a belt-conveyor scale shall be adequately protected from environmental factors such as 

 1 The variables and uncertainties included in the relative tolerance represent only part of the variables that affect the 

accuracy of the material weighed on belt-conveyor scales. If this tolerance was based on an error analysis beginning with 

mass standards through all of the test processes and following the principle expressed in Section 3.2. of the Fundamental 

Considerations in Appendix A, the tolerance would be 0.5 percent. 

(Added 1993)
2.21. Belt-Conveyor Scale Systems

2-47

wind, moisture, dust, weather, and radio frequency interference (RFI) and electromagnetic interference (EMI) that 

may adversely affect the operation or performance of the device.

 

UR.2.2. Conveyor Installation. - The design and installation of the conveyor leading to and from the belt-conveyor 

scale is critical with respect to scale performance. The conveyor cay be horizontal or inclined, but if inclined, the 

angle shall be such that slippage of material along the belt doe not occur. Installation shall be in accordance with the 

scale manufacturer's instructions and the following:

(Amended 2002)

(a) Installation - General. - A belt-conveyor scale shall be so installed that neither its performance nor operation 

will be adversely affected by any characteristic of the installation, including but not limited to, the foundation, 

supports, covers, or any other equipment.

(Amended 2002)

(b) Live Portions of Scale. - All live portions of the scale shall be protected by appropriate guard devices to 

prevent accidental interference with the weighing operation.

(c) Storage of Simulated Load Equipment. - Suitable protection shall be provided for storage of any simulated 

load equipment.

(d) Take-up Device. - If the belt length is such that a take-up device is required, this device shall be of the 

counter-weighted type for either vertical or horizontal travel.

(e) Scale Location and Training Idlers. - The scale shall be so installed that the first weigh idler of the scale is 

at least 6 m (20 ft) or 5 idler spaces, whichever is greater, from loading point, skirting, head or tail pulley, or 

convex curve in the conveyor. Any training idler shall be located at least 18 m (60 ft) from the centerline of 

the weigh span of the scale. Training idlers shall not be restrained at any time in order to force belt alignment.

(Amended 1998)

(f) Concave Curve. - If there is a concave curve in the conveyor, before or after the scale, the scale shall be 

installed so that the belt is in contact with all the idler rollers at all times for at least 6 m (20 ft) or 5 idler 

spaces, whichever is greater, before and after the scale.2

(Amended 1998)

 A concave curve shall start no closer than 12 m 

(40 ft) from the scale to the tangent point of the concave curve.

(g) Tripper and Movable Pulleys. - There shall be no tripper or movable head pulleys in the conveyor.

(h) Conveyor Length. - The conveyor shall be no longer than 300 m (1000 ft) nor shorter than 12 m (40 ft) from 

head to tail pulley.

[Nonretroactive as of January 1, 1986]

(i) Conveyor Orientation. - The conveyor may be horizontal or inclined, but, if inclined, the angle shall be such 

that slippage of material along the belt does not occur. 

(j) Conveyor Stringers. - Conveyor stringers at the scale and for not less than 6 m (20 ft) before and beyond the 

scale shall be continuous or securely joined and of sufficient size and so supported as to eliminate relative 

deflection between the scale and adjacent idlers when under load. The conveyor stringers should be so 

designed that the deflection between any two adjacent idlers within the weigh area does not exceed 0.6 mm 

(0.025 in) under load.

 2 Installing the belt scale 5 idler spaces from the tail pulley or the infeed skirting will be in the area of least belt tension on 

the conveyor and should produce the best accuracy. The performance of a belt-conveyor scale may be adversely affected 

by a concave curve in the conveyor that is located between the loading point and the scale. Therefore, whenever possible, 

a belt-conveyor scale should not be installed with a concave curve in the conveyor between the loading point and the 

scale. 

(Amended 1995 and 1998)
2.21. Belt-Conveyor Scale Systems

2-48

(k) Identification of Scale Area. - The scale area and 5 idlers on both ends of the scale shall be of a contrasting 

color, or other suitable means shall be used to distinguish the scale from the remainder of the conveyor installation, and the scale shall be readily accessible.

(Amended 1998)

(l) Belt Composition and Maintenance. - Conveyor belting shall be no heavier than is required for normal use. 

In a loaded or unloaded condition, the belt shall make constant contact with horizontal and wing rollers of the 

idlers in the scale area. Splices shall not cause any undue disturbance in scale operation (see N.3.).

(Amended 1998, 2000, and 2001)

(m) Uniformity of Belt Loading and Flow. - The conveyor loading mechanism shall be designed to provide 

uniform belt loading. The distance from the loading point to the scale shall allow for adequate settling time of 

the material on the belt before it is weighed. Feeding mechanisms shall have a positive closing or stopping 

action so that material leakage does not occur. Feeders shall provide an even flow over the scale through the 

full range of scale operation. Sufficient impact idlers shall be provided in the conveyor under each loading 

point to prevent deflection of the belt during the time material is being loaded.

(n) Belt Alignment. - The belt shall not extend beyond the edge of the idler roller in any area of the conveyor.

(Amended 1998)

UR.2.3. Material Test. - A belt-conveyor scale shall be installed so that a material test can be conveniently 

conducted.

[Nonretroactive as of January 1, 1981]

 

UR.2.4. Belt Travel (Speed or Velocity). - The belt travel sensor shall be so positioned that it accurately represents 

the travel of the belt over the scale for all flow rates between the maximum and minimum values. The belt travel 

sensor shall be so designed and installed that there is no slip.

UR.3. Use Requirements.

UR.3.1. Loading. - The feed of material to the scale shall be controlled to assure that, during normal operation, the 

material flow is in accordance with manufacturer's recommendation for rated capacity.

 

UR.3.2. Maintenance. - Belt-conveyor scales and idlers shall be maintained and serviced in accordance with 

manufacturer's instructions and the following:

(a) The scale and area surrounding the scale shall be kept clean of debris or other foreign material that can 

detrimentally affect the performance of the system.

(b) Simulated load tests or material tests, and zero load tests shall be conducted at periodic intervals between 

official tests in order to provide reasonable assurance that the device is performing correctly. 

The action to be taken as a result of the material tests or simulated load tests is as follows:

(Amended 2002)

- if the error is less than 0.25 percent, no adjustment is to be made;

- if the error is at least 0.25 percent but not more than 0.6 percent, adjustment may be made if the official 

with statutory authority is notified;

(Amended 1991)

- if the error is greater than 0.6 percent but does not exceed 0.75 percent, adjustments shall be made only by 

a competent service person and the official with statutory authority shall be notified. After such an adjustment, if the results of a subsequent test require adjustment in the same direction, an official test shall be 

conducted;

(Amended 1991)
2.21. Belt-Conveyor Scale Systems

2-49

- if the error is greater than 0.75 percent, an official test is required.

(Amended 1987)

(c) Scale Alignment. - Alignment checks shall be conducted in accordance with the manufacturer's 

recommendation when conveyor work is performed in the scale area. A material test is required after any 

realignment. 

(Amended 1986 and 2000)

(d) Simulated Load Equipment. - Simulated load equipment shall be clean and properly maintained.

(e) Zero Load Reference Information. – When zero load reference information is recorded for a delivery, the 

information must be based upon zero load tests performed as a minimum both immediately before and 

immediately after the totalized load.

(Added 2002)

(Amended 2002)

UR.3.3. Retention of Maintenance, Test, and Analog or Digital Recorder Information. - Records of calibration 

and maintenance, including conveyor alignment, analog or digital recorder, zero-load test, and material test data shall 

be maintained on site for at least the three concurrent years as a history of scale performance. Copies of any report as 

a result of a test or repair shall be mailed to the official with statutory authority as required. The current date and 

correction factor(s) for simulated load equipment shall be recorded and maintained in the scale cabinet.

(Added 2002)

UR.4. Compliance. - Prior to initial verification, the scale manufacturer or installer shall certify to the owner that the 

scale meets code requirements. Prior to initial verification and each subsequent verification, the scale owner or his agent 

shall notify the official with statutory authority in writing that the belt-conveyor scale system is in compliance with this 

specification and ready for material testing. 

(Amended 1991)
2.21. Belt-Conveyor Scale Systems

2-50
2.22. Automatic Bulk Weighing Systems

2-51

Sec. 2.22. Automatic Bulk Weighing Systems1

A. Application

A.1. General. - This code applies to automatic bulk weighing systems, that is, weighing systems adapted to the 

automatic weighing of a commodity in successive drafts of predetermined amounts automatically recording the no-load 

and loaded weight values and accumulating the net weight of each draft.

(Amended 1987)

A.2. Also see General Code Requirements.

S. Specifications

S.1. Design of Indicating and Recording Elements and Recorded Representations.

S.1.1. Zero Indication. - Provisions shall be made to indicate and record a no-load reference value and, if the noload reference value is a zero value indication, to indicate and record an out-of-balance condition on both sides of 

zero.

S.1.1.1. Digital Zero Indication. - A digital zero indication shall represent a balance condition that is within 

±1/2 the value of the scale division.

S.1.2. Value of Scale Division (d). - The value of the scale division (d), expressed in a unit of weight, shall be equal 

to: 

(a) 1, 2, or 5; or

(b) a decimal multiple or submultiple of 1, 2, or 5; or

(c) a binary submultiple of a unit of weight.

Examples: Scale divisions may be 0.01, 0.02, or 0.05; 0.1, 0.2, or 0.5; 1, 2, or 5; 10, 20, or 50; or 1/2, 1/4, 1/8, 

1/16, etc.

[Nonretroactive as of January 1, 1986]

(Amended 1987)

S.1.3. Capacity Indication and Recorded Representation. - An indicating or recording element shall not indicate 

or record any values when the gross load is in excess of 105 percent of the capacity of the system.

S.1.4. Weighing Sequence. - For systems used to receive (weigh in), the no-load reference value shall be 

determined and recorded only at the beginning of each weighing cycle. For systems used to deliver (weigh out), the 

no-load reference value shall be determined and recorded only after the gross load reference value for each weighing 

cycle has been indicated and recorded.

S.1.5. Recording Sequence. - Provision shall be made so that all weight values are indicated until the completion of 

the recording of the indicated value.

S.1.6. Provision for Sealing Adjustable Components on Electronic Devices. - Provision shall be made for 

applying a security seal in a manner that requires the security seal to be broken before an adjustment can be made to 

any component affecting the performance of the device.

 1

(Title amended 1986)
2.22. Automatic Bulk Weighing Systems

2 - 52

S.2. Design of Balance and Damping Mechanism.

S.2.1. Zero-Load Adjustment. - The weighing system shall be equipped with manual or semiautomatic means by 

which the zero-load balance or no-load reference value indication may be adjusted. An automatic zero setting 

mechanism is prohibited.

S.2.1.1. Manual. - A manual zero-load or no-load reference value setting mechanism shall be operable or 

accessible only by a tool outside of or entirely separate from this mechanism or enclosed in a cabinet.

S.2.1.2. Semiautomatic. - A semiautomatic zero-load or no-load reference value setting mechanism shall meet 

the provisions of S.2.1.1. or shall be operable only when:

(a) the indication is stable within ±3 scale divisions, and

(b) cannot be operated during a weighing operation.

S.2.2. Damping Means. - A system shall be equipped with effective means necessary to bring the indications 

quickly to a readable, stable equilibrium. Effective means shall also be provided to permit the recording of weight 

values only when the indication is stable within plus or minus three scale divisions for devices with 10 000 scale 

divisions, or plus or minus one division for devices with less than 10 000 scale divisions.

S.3. Interlocks and Gate Control.

S.3.1. Gate Position. - Provision shall be made to clearly indicate to the operator the position of the gates leading 

directly to and from the weigh hopper.

S.3.2. Interlocks. - Each automatic bulk weighing system shall have operating interlocks to provide for the 

following:

(a) Product cannot be cycled and weighed if the weight recording element is disconnected or subjected to a 

power loss.

(b) The recording element cannot print a weight if either of the gates leading directly to or from the weigh 

hopper is open.

(c) A "low paper" sensor, when provided, is activated.

(d) The system will operate only in the proper sequence in all modes of operation.

(e) When an overfill alarm is activated, the system shall indicate and record an overfill condition.

(Amended 1993)

S.3.3. Overfill Sensor.

(a) The weigh hopper shall be equipped with an overfill sensor which will cause the feed gate to close, activate 

an alarm, and inhibit weighing until the overfill condition has been corrected.

(Part (a) Added 1993)
2.22. Automatic Bulk Weighing Systems

2-53

(b) If the system is equipped with a lower garner or surge bin, that garner shall also be equipped with an 

overfill sensor which will cause the gate of the weigh hopper to remain open, activate an alarm, and inhibit 

weighing until the overfill condition has been corrected.

[Nonretroactive as of January 1, 1998] (Part (b) Amended 1997)

S.4. Design of Weighing Elements.

S.4.1. Antifriction Means. - At all points at which a live part of the mechanism may come into contact with another 

part in the course of normal usage, frictional effects shall be reduced to a minimum by means of suitable antifriction 

means, opposing surfaces and points being properly shaped, finished, and hardened.

S.4.2. Adjustable Components. - An adjustable component, such as a potentiometer, shall be held securely in 

adjustment and, except for a component for adjusting level or a no-load reference value, shall not be adjustable from 

the outside of the device.

S.4.3. Multiple Load-Receiving Elements. - A system with a single indicating or recording element, or a 

combination indicating recording element, that is coupled to two or more load-receiving elements with independent 

weighing systems, shall be provided with means to prohibit the activation of any load-receiving element (or 

elements) not in use, and shall be provided with automatic means to indicate clearly and definitely which loadreceiving element (or elements) is in use.

S.4.4. Venting. - All weighing systems shall be vented so that any internal or external pressure will not affect the 

accuracy or operation of the system.

S.5. Marking Requirements. (See also G-S.1.)

S.5.1. Capacity and Value of the Scale Division. - The capacity of the weighing system and the value of the scale 

division shall be clearly and conspicuously marked on the indicating element near the weight value indications.

S.5.2. Weighing Elements. - On a weighing element not permanently attached to an indicating element, there shall 

be clearly and permanently marked for the purposes of identification, the name, initials, or trademark of the manufacturer, the manufacturer's designation that positively identifies the pattern or design, and the nominal capacity.

S.5.3. Temperature Limits. - Unless the temperature range is -10 C to +40 C (14 F to 104 F), the 

temperature range shall be marked on the device. [Nonretroactive as of January 1, 1986]

(Added 1985)

S.5.4. Accuracy Class.

(a) All systems used to weigh grain shall be marked Class III*.

(b) All other systems shall be marked either Class III or III L*.

(*See Section 2.20 Scales Code for the parameters for these accuracy classes for scales. The specific requirements 

for automatic bulk weighing systems apply to these devices when there is a conflict between the Scales Code and the 

Automatic Bulk Weighing Systems Code.)

[Nonretroactive as of January 1, 1986]

(Added 1985) (Amended 1992)

N. Notes

N.1. Testing Procedures.

N.1.1. Test Weights. - The increasing load test shall be conducted using test weights equal to at least 10 percent of 

the capacity of the system:

(a) on automatic grain bulk-weighing systems installed after January 1, 1984, and
2.22. Automatic Bulk Weighing Systems

2 - 54

(b) on other automatic bulk-weighing systems installed after January 1, 1986. 

(Amended 1987)

N.1.2. Increasing-Load Test. - An increasing-load test consisting of substitution and strain-load tests shall be 

conducted up to the used capacity of the weighing system.

(Amended 1987)

N.1.3. Decreasing-Load Test. - A decreasing-load test shall be conducted on devices used to weigh out.

(Added 1986)

N.1.4. Zero Balance or No-Load Reference Value Change Test. - A test for change of zero-balance or no-load 

reference value shall be conducted on all scales after the removal of any test load. The change shall not be more than 

the minimum tolerance applicable.

N.1.5. Discrimination Test. - A discrimination test shall be conducted on all automatic indicating scales with the 

weighing device in equilibrium at zero-load and at maximum test load, and under controlled conditions in which 

environmental factors are reduced to the extent that they will not affect the results obtained.

[Nonretroactive as of January 1, 1986]

N.1.5.1. Digital Device. - On a digital device, this test is conducted from just below the lower edge of the zone 

of uncertainty for increasing-load tests, or from just above the upper edge of the zone of uncertainty for 

decreasing-load tests.

(Added 1987)

N.2. Verification (Testing) Standards. - Standard weights and masses used in verifying weighing devices shall comply 

with requirements of NIST Handbook 105-1 (Class F) or the tolerances expressed in Appendix A, Fundamental 

Considerations, paragraph 3.2. (i.e., one-third of the smallest tolerance applied).

T. Tolerances

T.1. Tolerance Application. - Tolerance values shall be applied to all indications and recorded representations of a 

weighing system.

T.1.1. To Errors of Underregistration and Overregistration. - The tolerances hereinafter prescribed shall be 

applied equally to errors of underregistration and errors of overregistration.

 

T.1.2. To Increasing-Load Tests. - Basic tolerances shall be applied.

T.1.3. To Decreasing-Load Tests. - Basic tolerances shall be applied to systems used to weigh out.

(Added 1986)

T.1.4. To Tests Involving Digital Indications or Representations. - To the tolerances that would otherwise be 

applied, there shall be added an amount equal to one-half the value of the scale division. This does not apply to 

digital indications or recorded representations that have been corrected for rounding using error weights.

(Added 1986)

 

T.2. Minimum Tolerance Values. - The minimum tolerance value shall not be less than half the value of the scale 

division.

 

T.2.1. For Systems used to Weigh Construction Materials. - The minimum maintenance and acceptance tolerance 

shall be 0.1 percent of the weighing capacity of the system, or the value of the scale division, whichever is less.

(Added 1986)

T.3. Basic Tolerance Values.

 

T.3.1. Acceptance Tolerance. - The basic acceptance tolerance shall be one-half the basic maintenance tolerance.

 

T.3.2. For Systems used to Weigh Grain. - The basic maintenance tolerance shall be 0.1 percent of test load.
2.22. Automatic Bulk Weighing Systems

2-55

T.3.3. For all Other Systems. - The basic maintenance tolerance shall be 0.2 percent of test load.

(Amended 1986)

 

T.4. Time Dependence. - At constant test conditions, the indication 20 seconds after the application of a load and the 

indication after 1 hour shall not differ by more than the absolute value of the applicable tolerance for the applied load.

[Nonretroactive and enforceable as of January 1, 1987]

(Added 1986)

T.5. Repeatability. - The results obtained by several weighings of the same load under reasonably static test conditions 

shall agree within the absolute value of the maintenance tolerance for that load, and shall be within applicable tolerances.

(Added 1986)

T.6. Discrimination, Digital Automatic Indicating Scales. - A test load equivalent to 1.4 d shall cause a change in the 

indicated or recorded value of at least 2.0 d. This requires the zone of uncertainty to be not greater than 0.3 times the 

value of the scale division. 

(Added 1985)

T.7. Influence Factors. - The following factors are applicable to tests conducted under controlled conditions only, 

provided that:

(a) types of devices approved prior to January 1, 1986, and manufactured prior to January 1, 1988, need not meet 

the requirements of this section; and

(b) new types of devices submitted for approval after January 1, 1986, shall comply with the requirements of this 

section; and

(c) all devices manufactured after January 1, 1988, shall comply with the requirements of this section.

[Nonretroactive as of January 1, 1986]

T.7.1. Temperature. - Devices shall satisfy the tolerance requirements under the following temperature conditions: 

T.7.1.1. If not marked on the device, the temperature limits shall be:

 

-10 oC to 40 oC (14 oF to 104 oF)

 

T.7.1.2. If temperature limits are specified for the device, the range shall be at least 30 C (54 F).

 

T.7.1.3. Temperature Effect on Zero-Load Balance. - The zero-load indicator shall not vary by more than 1 

division per 5 oC (9 oF) change in temperature.

 

T.7.1.4. Operating Temperature. - An indicating or recording element shall not display or record any usable 

values until the operating temperature necessary for accurate weighing and a stable zero-balance condition has 

been attained.

[Nonretroactive as of January 1, 1986]

T.7.2. Barometric Pressure. - The zero indication shall not vary by more than one scale division for a change in 

barometric pressure of 1 kPa over the total barometric range of 95 kPa to 105 kPa (28 in to 31 in of mercury).

[Nonretroactive as of January 1, 1986] 

T.7.3. Electric Power Supply.

T.7.3.1. Power Supply, Voltage and Frequency.

 

(a) Weighing devices that operate using alternating current must perform within the conditions defined in 

paragraphs T.2. through T.7. inclusive over the line voltage range of 100 V to 130 V or 200 V to 250 V 

rms as appropriate and over the frequency range of 59.5 Hz to 60.5 Hz.
2.22. Automatic Bulk Weighing Systems

2 - 56

(b) Battery-operated instruments shall not indicate nor record values outside the applicable tolerance limits 

when battery power output is excessive or deficient.

T.7.3.2. Power Interruption. - A power interruption shall not cause an indicating or recording element to 

display or record any values outside the applicable tolerance limits.

[Nonretroactive as of January 1, 1986]

(Added 1985)

UR. User Requirements

UR.1. Selection Requirements.

UR.1.1. For Systems used to Weigh Grain. - The number of scale divisions of a weighing system shall not be less 

than 2 000 nor greater than 10 000 divisions.

[Nonretroactive as of January 1, 1984]

(Amended 1986 and 1992)

U.R.1.2. For Systems used to Weigh Commodities other than Grain. - The number of scale divisions shall not be 

less than 500 nor greater than 10 000.

[Nonretroactive as of January 1, 1987]

(Added 1986)

UR.2. Installation Requirements.

UR.2.1. Protection From Environmental Factors. - The indicating elements, the lever system or load cells, the 

load-receiving element, and any permanently installed test weights shall be adequately protected from environmental 

factors such as wind, weather, and RFI that may adversely affect the operation or performance of the system.

UR.2.2. Foundation, Supports, and Clearance. - The foundation and supports of any system shall be such as to 

provide strength, rigidity, and permanence of all components, and clearance shall be provided around all live parts so 

that no contact can result before or during operation of the system.

UR.3. Loading Requirements.

UR.3.1. For Systems Used to Weigh Grain. - A system shall not be used to weigh drafts less than 40 percent of 

the weighing capacity of the system except for a final partial draft. Loads shall not normally be retained on the 

weighing element for a period longer than a normal weighing cycle.

(Amended 1986)

UR.3.2. For Systems Used to Weigh Commodities Other than Grain. - A system shall not be used to weigh drafts 

less than 20 percent of the weighing capacity of the system except for a final partial draft. Loads shall not normally 

be retained on the weighing element for a period longer than a normal weighing cycle.

[Nonretroactive as of January 1, 1987]

(Added 1986)

UR.4. System Modification. - The weighing system shall not be modified except when the modification has been 

approved by a competent engineering authority, preferably that of the engineering department of the manufacturer of the 

scale, and the official with statutory authority having jurisdiction over the scale.

(Amended 1991)
2.23. Weights

2-57

Sec. 2.23. Weights

A. Application

A.1. This code applies to commercial weights; that is, weights used in connection with commercial weighing devices.

A.2. This code does not apply to test weights or to other "standards" of mass.

A.3. See also General Code requirements.

S. Specifications

S.1. Material. - The material used for weights shall be as follows:

(a) Weights of 6 g or 100 gr and larger shall be made of a metal, or a metal alloy, not softer than brass.

(b) Weights of less than 6 g or 100 gr may be made of aluminum, but shall not be made of iron or of unplated steel, 

except stainless steel.

S.2. Design.

S.2.1. Surface. - The surface of a weight shall be smooth and shall not be coated with thick, soft, or brittle material. 

A weight of more than 2 g or 30 gr or shall not have sharp edges, points, or corners.

 

S.2.2. Ring. - A ring on a weight shall not be split or removable.

S.3. Adjusting Material. - Adjusting material shall be securely positioned and shall not project beyond the surface of the 

weight.

S.4. Marking Requirements.

S.4.1. General. - A weight shall be marked to show clearly its nominal value, which shall include identification of 

the unit; however, the nominal value of a weight of 30 gr or 2 g, or less, may be designated by dots, lines, figures, 

distinctive shape, or other appropriate means.

 

S.4.2. Apothecaries' Weights. - On apothecaries' dram, ounce, and pound weights, the letters "ap" shall be used in 

combination with the nominal value and the appropriate abbreviation of or symbol for the unit.

S.4.3. Troy Weights. - On troy ounce and pound weights, the letter "t" shall be used in combination with the 

nominal value and the appropriate symbol of the unit.

S.4.4. Metric Weights. - On metric weights, the symbols "kg," "g," and "mg" shall be used in combination with the 

nominal value of kilograms, grams, and milligrams, respectively.

S.4.5. Carat Weights. - On carat weights, the letter "c" shall be used in combination with the nominal value.

S.4.6. Counterpoise Weight. - A counterpoise weight shall be marked to show clearly both its nominal value and 

the value it represents when used on the multiplying-lever scale for which it is intended.

N. Notes

N.1. Testing Procedures. - Commercial weights should be tested on a precision balance using standard weights, the 

errors of which, when used without correction, do not exceed 1/3 of the smallest tolerance to be applied. (See Appendix 

A; Fundamental Considerations paragraphs 3.2. and 3.3.)
2.23. Weights

2-58

T. Tolerances

T.1. In Excess and in Deficiency. - The tolerances hereinafter prescribed shall be applied equally to errors in excess and 

errors in deficiency.

T.2. On Avoirdupois Weights. - The maintenance tolerances shall be as shown in Table 1. Acceptance tolerances shall 

be one-half the maintenance tolerances.

Table 1.

Maintenance Tolerance for Avoirdupois Weights

Maintenance Tolerance

Nominal 

Value

Equal-Arm

Weights

Counterpoise Weights

For scales with multiples of 

less than 1000

For scales with multiples of 

1000 or over

oz grains mg grains mg grains mg

1/64 0.1 6

1/32 0.3 19

1/16 0.4 26

1/8 0.5 32

1/4 1.0 65

1/2 1.5 97 1.0 65

1 1.7 110 1.0 65

2 2.0 130 1.0 65

3 2.0 130 1.5 97

4 3.0 190 1.5 97 1.0 65

5 3.5 230 1.5 97 1.0 65

6 3.5 230 1.5 97

8 4.0 260 2.0 130 1.5 97

10 4.0 260 2.5 160 2.0 130

12 5.0 320 2.5 160 2.0 130

lb grains mg grains mg grains mg

1 5.0 320 3.0 190 2.5 160

2 7.0 450 6.0 390 4.0 260

3 9.0 580 9.0 580 5.0 320

4 11.0 710 11.0 710 6.0 390

5 15 970 12.0 780 6.5 420

6 17 1190

7 19 1200

8 21 1400 15.0 970 9.0 580

9 23 1500

10 25 1600 18.0 1160 10.0 650

15 28 1800

20 30 1900

25 35 2300

30 40 2600

40 45 2900

50 50 3200
2.23. Weights

2-59

T.3. On Metric Weights. - The maintenance tolerances shall be as shown in Table 2. Acceptance tolerances shall be 

one-half the maintenance tolerances.

T.4. On Carat Weights. - The maintenance tolerances shall be as shown in Table 2. Acceptance tolerances shall be 

one-half the maintenance tolerances.

Table 2.

Maintenance Tolerances for Metric Weights

Nominal

Value

(mg)

Maintenance

Tolerance

(mg)

Nominal Value

(g)

Maintenance

Tolerance

(mg)

5 or less

10

20

30

50

100

200

300

500

0.1

0.3

0.4

0.6

0.8

1.0

1.5

2.0

3.0

1

2

3

5

10

20

30

50

100

200

300

500

4

6

8

10

15

20

30

40

70

100

150

175

Nominal

Value

(kg)

Maintenance

Tolerance

(mg)

Nominal

Value

(carats)

Maintenance

Tolerance

(mg)

1

2

3

5

10

20

250

400

500

800

1000

1500

0.25*

0.5**

1.0

2.0

3.0

5.0

10.0

20.0

30.0

50.0

100.0

0.6

1.0

1.5

2.0

3.0

4.0

6.0

10.0

12.0

15.0

25.0

*25 points or less

**50 points
2.23. Weights

2-60

T.5. On Apothecaries' and Troy Weights. - The maintenance tolerances shall be as shown in Table 3. Acceptance 

tolerances shall be one-half the maintenance tolerances.

Table 3.

Maintenance Tolerances

For Apothecaries' and Troy Weights

Nominal

Value Maintenance Tolerance Nominal

Value Maintenance Tolerance

grains grains mg oz grains mg

1

2

3

5

10

20

0.01

0.02

0.03

0.03

0.04

0.06

0.6

1.3

2.0

2.0

2.5

4.0

1

2

3

4

5

0.4

0.6

1.0

1.5

1.6

25.0

40.0

65.0

100.0

105.0

scruples grains mg oz grains mg

1

2

0.06

0.10

4.0

6.5

6

7

8

9

10

1.8

1.9

2.0

2.1

2.2

115.0

125.0

130.0

135.0

145.0

dr grains mg oz grains mg

0.5

1.0

2.0

3.0

4.0

5.0

6.0

0.07

0.10

0.20

0.30

0.40

0.50

0.60

4.5

6.5

13.0

20.0

25.0

30.0

40.0

11

12

20

30

50

2.4

2.5

2.9

3.7

5.4

155.0

160.0

190.0

240.0

350.0

dwt grains mg oz grains mg

1

2

3

4

5

10

0.06

0.10

0.15

0.20

0.30

0.40

4.0

6.5

10.0

13.0

20.0

25.0

100

200

300

500

1000

7.7

12.3

15.4

23.1

38.6

500.0

800.0

1000.0

1500.0

2500.0
2.24. Automatic Weighing Systems

2-61

Section 2.24. Automatic Weighing Systems - Tentative Code

This tentative code has only a trial or experimental status and is not intended to be enforced by weights and 

measures officials. The requirements are designed for study prior to the development and adoption of a final Code 

for Automatic Weighing Systems. The tentative code is intended to be used by the National Type Evaluation 

Program for type evaluation of automatic weighing systems. If upgraded to become a permanent code, all 

requirements, except those for tolerances, will be nonretroactive as of the effective date of the permanent code; 

tolerance requirements will apply retroactively as of the effective date of the permanent code.

(Tentative Code Added 1995) (Amended 1998)

A. Application

A.1. - This code applies to devices used to weigh or fill packages while the object is in motion. Some weigh-labelers may 

also include a scale that is incorporated in a conveyor system that weighs packages in a static weighing mode.

This includes:

(a) Weigh-labelers, static and dynamic

(b) Automatic checkweighers

(Amended 1997)

A.2. - This code does not apply to:

(a) Belt-Conveyor Scale Systems

(b) Railway Track Scales

(c) Monorail Scales

(d) Automatic Bulk-Weighing Systems

(e) Devices that measure quantity on a time basis

(f) Controllers or other auxiliary devices except as they may affect the weighing performance

A.3. - Also see General Code requirements.

A.4. Type Evaluation. - The National Type Evaluation Program will accept for type evaluation only those devices that 

comply with all requirements of this code.

(Added 1998)

S. Specifications

S.1. Design of Indicating and Recording Elements and of Recorded Representations.

S.1.1. Zero Indication. 

(a) A weigh-labeler shall be equipped with an indicating or recording element. It shall either indicate or record 

a zero-balance condition and an out-of-balance condition on both sides of zero.

(b) An automatic checkweigher may be equipped with an indicating or recording element.

(c) A zero-balance condition may be indicated by other than a continuous digital zero indication, provided that 

effective automatic means is provided to inhibit a weighing operation or to return to a continuous digital 

indication when the device is in an out-of-balance condition.
2.24. Automatic Weighing Systems

2-62

S.1.1.1. Digital Indicating Elements. 

(a) A digital zero indication shall represent a balance condition that is within ± 1⁄2 scale division.

(b) A digital indicating device shall either automatically maintain a "center of zero" condition to ± 1⁄4 scale 

division or less, or have an auxiliary or supplemental "center-of-zero" indicator that defines a 

zero-balance condition to ± 1⁄4 scale division or less.

(c) Verification of the accuracy of the center of zero indication to ± 1⁄4 scale division or less during dynamic 

operation is not required on automatic checkweighers.

S.1.2. Value of Division Units. - The value of a division "d" expressed in a unit of weight shall be equal to:

(a) 1, 2, or 5; or 

(b) a decimal multiple or submultiple of 1, 2, or 5.

S.1.2.1. Weight Units. - A device shall indicate weight values using only a single unit of measure. 

S.1.3. Provision for Sealing. 

(a) Automatic Weighing Systems, Except Automatic Checkweighers. - A device shall be designed with 

provision(s) as specified in Table S.1.3., "Categories of Device and Methods of Sealing," for applying a 

security seal that must be broken, or for using other approved means of providing security (e.g., data change 

audit trail available at the time of inspection), before any change that detrimentally affects the metrological 

integrity of the device can be made to any electronic mechanism.

(b) For Automatic Checkweighers. - Security seals are not required in field applications where it would 

prohibit an authorized user from having access to the calibration functions of a device. 

Table S.1.3.

Categories of Device and Methods of Sealing

Categories of Device Method of Sealing

Category 1: No Remote configuration capability. Seal by physical seal or two event counters: one for 

calibration parameters and one for configuration parameters.

Category 2: Remote configuration capability, but access is 

controlled by physical hardware.

Device shall clearly indicate that it is in the remote 

configuration mode and record such message if capable of 

printing in this mode.

The hardware enabling access for remote communication 

must be at the device and sealed using a physical seal or two 

event counters: one for calibration parameters and one for 

configuration parameters.

Category 3: Remote configuration capability access may 

be unlimited or controlled through a software switch (e.g., 

password).

An event logger is required in the device; it must include an 

event counter (000 to 999), the parameter ID, the date and 

time of the change, and the new value of the parameter. A 

printed copy of the information must be available through 

the device or through another on-site device. The event 

logger shall have a capacity to retain records equal to ten 

times the number of sealable parameters in the device, but 

not more than 1000 records are required. (Note: Does not 

require 1000 changes to be stored for each parameter.)

S.1.4. Automatic Calibration. - A device may be fitted with an automatic or a semi-automatic calibration 

mechanism. This mechanism shall be incorporated inside the device. After sealing, neither the mechanism nor the 

calibration process shall facilitate fraud.
2.24. Automatic Weighing Systems

2-63

N

d

vmin ≤

S.1.5. Adjustable Components. - Adjustable components shall be held securely in adjustment and, except for a 

zero-load balance mechanism, shall be located within the housing of the element.

S.2. Design of Zero and Tare Mechanisms.

S.2.1. Zero Load Adjustment.

S.2.1.1. Automatic Zero-Setting Mechanism. - Except for automatic checkweighers, under normal operating 

conditions the maximum load that can be "rezeroed," when either placed on or removed from the platform all at 

once, shall be 1.0 scale division.

S.2.1.2. Initial Zero-Setting Mechanism. - Except for automatic checkweighers, an initial zero-setting 

mechanism shall not zero a load in excess of 20 percent of the maximum capacity of the automatic weighing 

system unless tests show that the scale meets all applicable tolerances for any amount of initial load compensated 

by this device within the specified range.

S.2.2. Tare. - On any automatic weighing system the value of the tare division shall be equal to the value of the 

division. The tare mechanism shall operate only in a backward direction (i.e., in a direction of underregistration) 

with respect to the zero-load balance condition of the automatic weighing system. A device designed to 

automatically clear any tare value shall also be designed to prevent the automatic clearing of tare until a complete 

transaction has been indicated.

Note: On a computing automatic weighing system, this requires the input of a unit price, the display of the unit 

price, and a computed positive total price at a readable equilibrium. Other devices require a complete weighing 

operation, including tare, net, and gross weight determination.

S.3.1. Multiple Range and Multi-Interval Automatic Weighing System. The value of "e" shall be equal to the 

value of "d."

S.3.2. Load Cell Verification Interval Value. - The relationship of the value for the load cell verification scale 

interval, vmin, to the scale division "d" for a specific scale installation shall be:

 , where N is the number of load cells in the scale.

Note: When the value of the scale division "d" differs from the verification scale division "e" for the scale, the value 

of "e" must be used in the formula above.

S.3.3. - For automatic checkweighers, the value of "e" shall be specified by the manufacturer and may be larger than 

"d," but in no case can "e" be more than 10 times the value of "d."

S.4. Weight Indicators, Weight Displays, Reports, and Labels.

S.4.1. Weight Units. - An indicating or recording element shall indicate weight values using only a single unit of 

measure.

S.4.2. Additional Digits in Displays. - Auxiliary digital displays that provide additional digits for use during 

performance evaluation may be included on automatic checkweighers. However, in cases where these indications are 

not valid for determining the actual weight of a package (e.g., only appropriate for use in statistical process control 

programs by users) they shall be clearly and distinctly differentiated from valid weight displays by indicating them to 

the user. 

For example, the additional digits may be differentiated by color, partially covered by placing crosshatch overlays on 

the display, or made visible only after the operator presses a button or turns a key to set the device in a mode which 

enables the additional digits.

S.4.3. Damping. - An indicating element equipped with other than automatic recording elements shall be equipped 

with effective means to permit the recording of weight values only when the indication is stable within plus or minus 

one scale division. The values recorded shall be within applicable tolerances.
2.24. Automatic Weighing Systems

2-64

S.4.4. Over Capacity Indication. - An indicating or recording element shall not display nor record any values when 

the scale capacity is exceeded by nine scale divisions.

S.4.5. Label Printer. - A device that produces a printed ticket to be used as the label for a package shall print all 

values digitally and of such size, style of type, and color as to be clear and conspicuous on the label.

S.4.5.1. Label Printing. - If an automatic checkweigher prints a label containing weight information that will be 

used in a commercial transaction, it must conform to all of the requirements specified for weigh-labelers so that 

the printed ticket meets appropriate requirements.

S.5. Accuracy Class.

S.5.1. Marking. - Weigh-labelers and automatic checkweighers shall be Class III devices and shall be marked 

accordingly, except that a weigh-labeler marked Class IIIS may be used in package shipping applications.

(Amended 1997)

S.6. Parameters for Accuracy Classes. - The number of divisions for device capacity is designated by the manufacturer 

and shall comply with parameters shown in Table S.6.

Table S.6.

Parameters for Accuracy Classes

Number of divisions (n) 

Class Value of the verification division (d or e) Minimum Maximum

SI Units

III 0.1 to 2g inclusive 100 10 000

equal to or greater than 5g 500 10 000

INCH-POUND Units

III

0.0002 lb to 0.005 lb, inclusive 100 10 000

0.005 oz to 0.125 oz, inclusive 100 10 000

equal to or greater than 0.01 lb 500 10 000

equal to or greater than 0.25 oz 500 10 000

IIIS greater than 0.01 lb 100 1000

greater than 0.25 oz 100 1000

For Class III devices, the value of "e" is specified by the manufacturer as marked on the device; "d" shall not be 

smaller than 0.1 "e." "e" shall be differentiated from "d" by size, shape, or color.

S.7. Marking Requirements. [See also G-S.1., G-S.4., G-S.6., G-S.7., G-U.2.1.1., and UR.3.3.]

S.7.1. Location of Marking Information. - Automatic weighing systems which are not permanently attached to an 

indicating element, and for which the load-receiving element is the only part of the weighing/load-receiving element 

visible after installation, may have the marking information required in G-S.1. of the General Code and Table S.7.a. 

and S.7.b. of the Automatic Weighing Systems Code located in an area that is accessible only through the use of a 

tool; provided that the information is easily accessible (e.g., the information may appear on the junction box under an 

access plate). The identification information for these automatic weighing systems shall be located on the 

weighbridge (load-receiving element) near the point where the signal leaves the weighing element or beneath the 

nearest access cover.
2.24. Automatic Weighing Systems

2-65

Table S.7.b.

Notes for Table S.7.a.

1. Manufacturer's identification and model designation. (See G-S.1.)

2. Serial number and prefix. (See G-S.1.)

3. The nominal capacity and value of the automatic weighing system division shall be shown together (e.g., 50 000 x 

5 kg, or 30 x 0.01 lb) adjacent to the weight display when the nominal capacity and value of the automatic weighing 

system division are not immediately apparent. Each division value or weight unit shall be marked on 

variable-division value or division-unit automatic weighing systems.

4. Required only if different from "d."

5. Required only on automatic weighing systems if the range is other than -10 C to 40 C (14 F to 104 F).

Table S.7.a. Marking Requirements

Weighing

Equipment

To Be

Marked With ⇓

Weighing,

load-receiving,

and

indicating

element in

same housing

Indicating

element not

permanently

attached to

weighing and

load-receiving

element

Weighing and

load-receiving

element not

permanently

attached to

indicating

element

Load

cell

with CC

(10)

Other

equipment or

device

(9)

Manufacturer's ID (1) x x x x x

Model Designation (1) x x x x x

Serial Number and Prefix (2) x x x x x (13)

Certificate of Conformance 

Number (16) x x x x x (16)

Accuracy Class (14) x x (8) x x

Nominal Capacity (3)(15) x x x

Value of Division, d (3) x x

Value of "e" (4) x x

Temperature Limits (5) x x x x

Special Application (11) x x x

Maximum Number of 

Scale Divisions, nmax (6) x (8) x x

Minimum Verification

Division, (emin) x 

"S" or "M" (7) x

Direction of Loading (12) x

Minimum Dead Load x

Maximum Capacity (Max) x x

Minimum Capacity (Min) x

Safe Load Limit x

Load Cell Verification

Interval (vmin)

x

Maximum Belt Speed (m/sec 

or m/min)

x x

Note: See Table S.7.b. for applicable parenthetical notes.

(Amended 1999)
2.24. Automatic Weighing Systems

2-66

Table S.7.b.

Notes for Table S.7.a.

6. This value may be stated on load cells in units of 1000; (e.g., n: 10 is 10 000 divisions.)

7. Denotes compliance for single or multiple load cell applications.

8. An indicating element not permanently attached to a weighing element shall be clearly and permanently marked with 

the accuracy Class III, or IIIS and the maximum number of divisions, nmax.

9. Necessary to the weighing system but having no metrological effect, e.g., auxiliary remote display, keyboard, etc.

10. The markings may be either on the load cell or in an accompanying document; except that, if an accompanying 

document is provided, the serial number shall appear both on the load cell and in the document. The manufacturer's 

name or trademark, the model designation, and identifying symbol for the serial number shall also be marked both 

on the load cell and in any accompanying document.

11. An automatic weighing system designed for a special application rather than general use shall be conspicuously 

marked with suitable words visible to the operator and customer restricting its use to that application.

12. Required if the direction of loading the load cell is not obvious. 

13. Serial number and prefix (See G-S.1) Modules without "intelligence" on a modular system (e.g., printer, keyboard 

module, cash drawer, and secondary display in a point-of-sale system) are not required to have serial numbers.

14. The accuracy Class of a device shall be marked on the device with the appropriate designation.

15. The nominal capacity shall be conspicuously marked on any automatic-indicating or recording automatic weighing 

system so constructed that the capacity of the indicating or recording element, or elements, is not immediately 

apparent.

16. Required only if a CC has been issued for the equipment.

S.7.2. Marking Required on Components of Automatic Weighing Systems. - The following components of 

automatic weighing systems shall be marked as specified in Tables S.7.a. and S.7.b.:

(a) Main elements and components when not contained in a single enclosure for the entire automatic weighing 

system;

(b) Load cells for which Certificates of Conformance (CC) have been issued under the National Type 

Evaluation Program; and

(c) Other equipment necessary to a weighing system but having no metrological effect on the weighing system.

N. Notes

N.1. Test Requirements for Automatic Weighing Systems.

N.1.1. Test Pucks and Packages.

(a) Test pucks and packages shall be:

(i) representative of the type, size, and weight ranges to be weighed on a device, and

(ii) stable while in motion, hence the length and width of a puck or package should be greater than its height.
2.24. Automatic Weighing Systems

2-67

(b) For type evaluation the manufacturer shall supply the test pucks or packages for each range of test loads.

(Amended 1997)

N.1.2. Accuracy of Test Pucks or Packages. - The error in any test puck or package shall not exceed one-fourth 

(1/4) of the acceptance tolerance. If packages are used to conduct field tests on automatic weighing systems, the 

package weights shall be determined on a reference scale or balance with an inaccuracy that does not exceed 

one-fifth (1/5) of the smallest tolerance that can be applied to the device under test.

N.1.3. Verification (Testing) Standards. - Field standard weights shall comply with requirements of NIST 

Handbook 105-1 (Class F) or the tolerances expressed in Fundamental Considerations, paragraph 3.2. (i.e., one-third 

of the smallest tolerance applied).

N.2. Test Requirements for Automatic Weighing Systems.

N.2.1. Tests Loads. - A performance test shall consist of four separate test runs conducted at different test loads 

according to Table N.3.2.

N.2.2. Influence Factor Testing. - Influence factor testing shall be conducted statically.

N.3. Test Procedures - Weigh-Labelers. - If the device is designed for use in static weighing, it shall be tested statically 

using mass standards.

Note: If the device is designed for only dynamic weighing, it shall only be tested dynamically.

N.3.1. Laboratory - Static Tests .

N.3.1.1. Increasing-Load Test. - The increasing-load test shall be conducted with the test loads approximately 

centered on the load-receiving element of the scale.

N.3.1.2. Decreasing-Load Test. - The decreasing-load test shall be conducted with the test loads approximately 

centered on the load-receiving element of the scale.

N.3.1.3. Shift Test. - To determine the effect of off-center loading, a test load equal to one-half (1⁄2) maximum 

capacity shall be placed in the center of each of the four points equidistant between the center and front, left, 

back, and right edges of the load receiver. 

N.3.1.4. Discrimination Test. - A discrimination test shall be conducted with the weighing device in 

equilibrium at zero load and at maximum test load, and under controlled conditions in which environmental 

factors are reduced to the extent that they will not affect the results obtained. This test is conducted from just 

below the lower edge of the zone of uncertainty for increasing load tests, or from just above the upper edge of 

the zone of uncertainty for decreasing-load tests.

N.3.1.5. Zero-Load Balance Change. - A zero-load balance change test shall be conducted on all automatic 

weighing systems after the removal of any test load. The zero-load balance should not change by more than the 

minimum tolerance applicable. (Also see G-UR.4.2.) 

N.3.1.6. Influence Factor Testing. - Influence factor testing shall be conducted.

N.3.2. Laboratory - Dynamic Tests. -

The device shall be tested at the highest 

speed for each weight range using 

standardized test pucks or packages. Test 

runs shall be conducted using four test 

loads as described in Table N.3.2. Each 

test load shall be run a minimum of 10 

consecutive times.

Table N.3.2. Test Loads

At or near minimum capacity

At or near maximum capacity

At two (2) critical points between minimum and maximum capacity

Test may be conducted at other loads if the device is intended for use at 

other specific capacities
2.24. Automatic Weighing Systems

2-68

N.3.2.1. Shift Test. - To determine the effect of eccentric loading, for devices without a means to align 

packages, a test load equal to one-third (1/3) maximum capacity shall be passed over the load receiver or 

transport belt (1) halfway between the center and front edge, and (2) halfway between the center and back edge.

N.3.3. Field Test Procedures. 

N.3.3.1. Static Tests. - If the automatic weighing system is designed to operate statically, and used in that 

manner, during normal use operation, it shall be tested statically using mass standards. The device shall not be 

tested statically if it is used only dynamically.

N.3.3.2. Dynamic Tests. - The device shall be tested at the normal operating speed using packages. Test runs 

should be conducted using at least two test loads distributed over its normal weighing range (e.g., at the lowest 

and highest ranges in which the device is typically operated.) Each test load should be run a minimum of 10 

consecutive times.

N.4. Test Procedures - Automatic Checkweigher.

N.4.1. Laboratory - Static Tests. - If the scale is designed to operate statically during normal user operation, it shall 

be tested statically using the applicable weigh-labeler requirements.

N.4.2. Laboratory - Dynamic Tests. - The device shall be tested at the highest speed in each weight range using 

standardized test pucks or packages. Test runs shall be conducted using four test loads. The number of consecutive 

test weighments shall be as described in Table N.4.2.

Table N.4.2. Number of Sample Weights per Test for Automatic Checkweighers

Weighing Range

m = mass of test load Number of sample weights per test

20 divisions < m < 10 kg

20 divisions < m < 22 lb 60

10 kg <m < 25 kg

22 lb <m < 55 lb 32

25 kg <m < 100 kg

55 lb <m < 220 lb 20

100 kg (220 lb) < m 10

N.4.3. Field Test Procedures.

N.4.3.1. Static Tests. - If the scale is designed to operate statically during normal user operation, it shall be 

tested statically according to Sections N.3.1.1. through N.3.1.5.

N.4.3.2. Dynamic Tests. - The device shall be tested dynamically at the highest normal operating speed using 

packages at two test loads distributed over its normal weighing range. The number of consecutive weighments 

shall be one-half (1⁄2) of those specified in Table N.4.2., but not less than 10.

T. Tolerances

T.1. Principles.

T.1.1. Design. - The tolerance for a weighing device is a performance requirement independent of the design 

principle used.

T.1.2. Scale Division. - The tolerance for a weighing device is related to the value of the scale division (d) or the 

value of the verification scale division (e) and is generally expressed in terms of d or e. The random tolerance for 

automatic checkweighers is expressed in terms of Maximum Allowable Variance (MAV).
2.24. Automatic Weighing Systems

2-69

T.2. Tolerance Application.

T.2.1. General. - The tolerance values are positive (+) and negative (-) with the weighing device adjusted to zero at 

no load. When tare is in use, the tolerance values are applied from the tare zero reference; the tolerance values apply 

to certified test loads only.

T.2.2. Type Evaluation Examinations. - For type evaluation examinations, the tolerance values apply to increasing 

and decreasing load tests within the temperature, power supply, and barometric pressure limits specified in T.7.

T.2.3. Multiple Range and Multi-Interval Automatic Weighing System. - For multiple range and multi-interval 

devices, the tolerance values are based on the value of the scale division of the range in use.

T.3. Tolerance Values. 

T.3.1. Tolerance Values - Class III Weigh-Labeler. (See T.3.2. for Class IIIS Weigh-Labelers)

T.3.1.1. Static Tests. - Tolerance values shall be as 

specified in Table T.3. Class III - Tolerances in 

Divisions.

T.3.1.2. Dynamic Tests. - Acceptance tolerance 

values shall be the same as maintenance tolerance 

values specified in Table T.3., Class III - Tolerances 

in Divisions.

T.3.2. Tolerance Values - Class IIIS Weigh-labelers in Package Shipping Applications.

(Added 1997)

T.3.2.1. Static Tests. - Tolerance values shall be as specified in Table T.3.2.1. Static Tolerances for Class IIIS 

Weigh-labelers.

T.3.2.2. Dynamic Tests. - Tolerance values specified in Table T.3.2.2. Dynamic Tolerances for Class IIIS 

Weigh-labelers shall be applied.

Table T.3.2.2. Dynamic Tolerance

for Class IIIS Weigh-labelers

Test Load in 

Divisions Tolerance in Divisions

Class IIIS Acceptance Maintenance

0 - 50 ± 1.5 ± 2

51 - 20 ± 2 ± 3

201 - 1000 ± 2.5 ± 4

(Added 1997)

T.3.3. Tolerance Values. - Automatic Checkweighers.

T.3.3.1. Laboratory Tests for Automatic Checkweighers.

T.3.3.1.1. Static Tests. - The acceptance tolerance values specified in Table T.3., Class III-Tolerances in 

Divisions, shall be applied.

T.3.3.1.2. Dynamic Tests.

(a) The systematic error for each test run must be within the acceptance tolerances for the test load as 

specified in Table N.3.2.

Table T.3. Class III - Tolerance in Divisions (d)

Test Load in 

Divisions Tolerance in Divisions

Class III Acceptance Maintenance

0 - 500 ± 0.5 ± 1

501 - 2000 ± 1 ± 2

2001 - 4000 ± 1.5 ± 3

4001 + ± 2.5 ± 5

Table T.3.2.1. Static Tolerance 

for Class IIIS Weigh-labelers

Test Load in 

Divisions Tolerance in Divisions

Class IIIS Acceptance Maintenance

0 - 50 ± 0.5 ± 1

51 - 200 ± 1 ± 2

201 - 1000 ± 1.5 ± 3

(Added 1997)
2.24. Automatic Weighing Systems

2-70

(b) The standard deviation of the results shall not exceed one-ninth (1/9) of the Maximum Allowable 

Variation (MAV) for specific package weights (3 standard deviations cannot exceed one-third (1/3) 

of the MAV value) as required in the 4th Edition of NIST Handbook 133. This value does not 

change regardless of whether acceptance, or maintenance tolerances are being applied to the device 

under test.

(i) For U.S. Department of Agriculture (USDA) inspected meat and poultry products packaged at 

a plant subject to inspection by the USDA Food Safety and Inspection Service, use Handbook 

133 Table 2-9, U.S. Department of Agriculture, Meat and Poultry, Groups and Lower Limits 

for Individual Packages, or

(ii) for all other packages with a labeled net quantity in terms of weight use Handbook 133 Table 

2-5, Maximum Allowable Variations for Packages Labeled by Weight.

(iii) For all packages with a labeled net quantity in terms of liquid or dry volume use 

Handbook 133 Table 2-6, Maximum Allowable Variations for Packages Labeled by Liquid or 

Dry Volume.

T.3.3.2. Field Tests for Automatic Checkweighers.

T.3.3.2.1. Static Test Tolerances. - The tolerance values shall be as specified in Table T.3., Class IIITolerances in Divisions.

T.3.3.2.2. Dynamic Test Tolerances. -

(a) The systematic error requirement is not applied in a field test.

(b) The standard deviation of the test results shall not exceed one-ninth (1/9) of the Maximum 

Allowable Variation (MAV) for specific package weights (3 standard deviations cannot exceed 

one-third (1/3) of the MAV value) as required in the 4th Edition of NIST Handbook 133. This 

value does not change regardless of whether acceptance or maintenance tolerances are being 

applied to the device under test.

(i) For U.S. Department of Agriculture (USDA) inspected meat and poultry products packaged at 

a plant subject to inspection by the USDA Food Safety and Inspection Service, use Handbook 

133 Table 2-9, U.S. Department of Agriculture, Meat and Poultry, Groups and Lower Limits 

for Individual Packages, or

(ii) for all other packages with a labeled net quantity in terms of weight use Handbook 133 Table 

2-5, Maximum Allowable Variations for Packages Labeled by Weight.

(iii) For all packages with a labeled net quantity in terms of liquid or dry volume use Handbook 

133 Table 2-6. Maximum Allowable Variations for Packages Labeled by Liquid or Dry 

Volume.

T.4. Agreement of Indications. - In the case of a weighing system equipped with more than one indicating element or 

indicating element and recording element combination, the difference in the weight value indications of any load shall not 

be greater than the absolute value of the applicable tolerance for that load, and shall be within tolerance limits.

T.5. Repeatability. - The results obtained from several weighings of the same load under reasonably static test conditions 

shall agree within the absolute value of the maintenance tolerance for that load, and shall be within applicable tolerances.

T.6. Discrimination. - A test load equivalent to 1.4 d shall cause a change in the indicated or recorded value of at least 

2.0 d. This requires the zone of uncertainty to be not greater than 0.3 d (See N.3.1.4.)

T.7. Influence Factors. - The following factors are applicable to tests conducted under controlled conditions only.

T.7.1. Temperature. - Devices shall satisfy the tolerance requirements under the following temperature conditions:
2.24. Automatic Weighing Systems

2-71

T.7.1.1. - If not specified in the operating instructions or if not marked on the device, the temperature limits shall 

be: -10 C to 40 C (14 F to 104 F).

T.7.1.2. - If temperature limits are specified for the device, the range shall be at least 30 C (54 F).

T.7.1.3. Temperature Effect on Zero-Load Balance. - The zero-load indication shall not vary by more than 

one division per 5 C (9 F) change in temperature.

T.7.1.4. Operating Temperature. - The indicating or recording element shall not display nor record any usable 

values until the operating temperature necessary for accurate weighing and a stable zero balance condition have 

been attained.

T.7.2. Barometric Pressure. - The zero indication shall not vary by more than one division for a change in barometric pressure of 1 kPa over the total barometric pressure range of 95 kPa to 105 kPa (28 in to 31 in of Hg).

T.7.3. Electric Power Supply. 

T.7.3.1. Power Supply, Voltage and Frequency.

(a) Alternating Current. - Weighing devices that operate using alternating current must perform within the 

conditions defined in paragraphs T.3. through T.7., inclusive, over the line voltage range of 100 V to 130 V 

or 200 V to 250 V rms as appropriate, and over the frequency range of 59.5 Hz to 60.5 Hz.

Note: This requirement applies only to metrologically significant voltage supplies.

(Amended 2001)

(b) Battery. - Battery operated instruments shall not indicate nor record values outside the applicable 

tolerance limits when battery power output is excessive or deficient.

T.7.3.2. Power Interruption. - A power interruption shall not cause an indicating or recording element to 

display or record any values outside the applicable tolerance limits.

T.8. Radio Frequency Interference (RFI) and Other Electromagnetic Interference Susceptibility. - The difference 

between the weight indication with the disturbance and the weight indication without the disturbance shall not exceed one 

scale division (d) or the equipment shall:

(a) blank the indication, or

(b) provide an error message, or

(c) the indication shall be so completely unstable that it could not be interpreted, or transmitted into memory or to a 

recording element, as a correct measurement value.

UR. User Requirements

UR.1. Selection Requirements. - Equipment shall be suitable for the service in which it is used with respect to elements 

of its design, including but not limited to, its capacity, number of scale divisions, value of the scale division or 

verification scale division, minimum capacity, and computing capability.

UR.1.1. General. - Automatic Weighing Systems shall be designated by the manufacturer for that service.

UR.1.2. Value of the Indicated and Recorded Scale Division. - The value of the division as recorded shall be the 

same as the division value indicated.
2.24. Automatic Weighing Systems

2-72

UR.2. Installation Requirements.

UR.2.1. Protection From Environmental Factors. - The indicating elements, the lever system or load cells, and the 

load-receiving element of a permanently installed scale, and the indicating elements of a scale not intended to be 

permanently installed, shall be adequately protected from environmental factors such as wind, weather, and RFI that 

may adversely affect the operation or performance of the device.

UR.2.2. Foundation, Supports, and Clearance. - The foundation and supports of any scale installed in a fixed 

location shall be such as to provide strength, rigidity, and permanence of all components, and clearance shall be 

provided around all live parts to the extent that no contacts may result when the load-receiving element is empty, nor 

throughout the weighing range of the scale.

UR.2.3. Entry and Departure From Weighing Area. - The belt or other conveyance that introduces the weighed 

load to the weighing zone and that carries the weighed load away from the weighing zone shall be maintained per the 

manufacturers recommendations.

UR.3. Use Requirements.

UR.3.1. Minimum Load. - The minimum load shall be as specified by the manufacturer, but not less than 

20 divisions since the use of a device to weigh light loads is likely to result in relatively large errors.

UR.3.1.1. Minimum Load for Class IIIS Weigh-labelers. - The minimum load shall be as specified by the 

manufacturer, but not less than 10 divisions since the use of a device to weigh light loads is likely to result in 

relatively large errors.

(Added 1997)

UR.3.2. Maximum Load. - An automatic weighing system shall not be used to weigh a load of more than the 

maximum capacity of the automatic weighing system.

UR.3.3. Special Designs. - An automatic weighing system designed and marked for a special application shall not be 

used for other than its intended purpose.

UR.3.4. Use of Manual Gross Weight Entries. - Manual entries are permitted only when a device or system is 

generating labels for standard weight packages.

UR.4. Maintenance Requirements.

UR.4.1. Balance Condition. - If an automatic weighing system is equipped with a zero-load display, the zero-load 

adjustment of an automatic weighing system shall be maintained so that the device indicates or records a zero balance 

condition.

UR.4.2. Level Condition. - If an automatic weighing system is equipped with a level-condition indicator, the 

automatic weighing system shall be maintained in level.

UR.4.3. Automatic Weighing System Modification. - The length or the width of the load-receiving element of an 

automatic weighing system shall not be increased beyond the manufacturer's design dimension, nor shall the capacity 

of an automatic weighing system be increased beyond its design capacity by replacing or modifying the original 

primary indicating or recording element with one of a higher capacity, except when the modification has been 

approved by competent engineering authority, preferably that of the engineering department of the manufacturer of 

the automatic weighing system, and by the weights and measures authority having jurisdiction over the automatic 

weighing system.
2.24. Automatic Weighing Systems

2-73

D. Definitions

automatic checkweigher. - A dynamic automatic weighing system used to subdivide items of different weights into one 

or more subgroups, such as identifying packages that have acceptable or unacceptable fill levels. These systems may be 

used to fill standard packages for compliance with net weight requirements.

automatic weighing system (AWS). - An automatic weighing system is a weighing device that, in combination with 

other hardware and/or software components, automatically weighs discrete items. Examples include, but are not limited 

to, weigh-labelers and checkweighers.

package rate. - PPM - Packages per minute.

random error(s). - The sample standard deviation of the error (indicated values) for a number of consecutive automatic 

weighings of a load, or loads, passed over the load receptor, shall be expressed mathematically as:

or

where:

x = error of a load indication

n = the number of loads

systematic (average) error (x). - The mean value of the error (of indication) for a number of consecutive automatic 

weighings of a load, or loads, passed over the load receiving element (e.g., weigh-table), shall be expressed 

mathematically as:

n

x

x = ∑

where:

x = error of a load indication

n = the number of loads

test puck. – A metal or plastic object used to simulate a package. Pucks can be made in a variety of dimensions and have 

different weights to represent a wide range of package sizes. Metal versions may be covered with rubber cushions to 

eliminate the possibility of damage to weighing and handling equipment. The puck mass is adjusted to specific accuracy 

so that pucks can be used to conduct performance tests.

weigh-labeler. - An automatic weighing system that determines the weight of a package and prints a label or other 

document bearing a weight declaration for each discrete item (usually a label also includes unit and total price 

declarations). Typically, this type of weighing system determines the weight of packages dynamically, but may also 

include a scale that is incorporated in a conveyor system that weighs packages in a static weighing mode. Weigh-labelers 

are sometimes used to weigh and label standard and random packages (also called "Prepackaging Scales").

∑( − ) − = x x

n i

2

1

1

s ( )















 − − = ∑ ∑ 2

2

 1

1

n n

s x

x

i

i
2.24. Automatic Weighing Systems

2-74
3.30. Liquid-Measuring Devices

3-1

Section 3

Page

3.30. Liquid-Measuring Devices 3-3

3.31.Vehicle-Tank Meters 3-23

3.32. LPG and Anhydrous Ammonia Liquid-Measuring Devices 3-31

3.33. Hydrocarbon Gas Vapor-Measuring Devices 3-41

3.34. Cryogenic Liquid-Measuring Devices 3-49

3.35. Milk Meters 3-57

3.36. Water Meters 3-63

3.37. Mass Flow Meters 3-67

3.38. Carbon Dioxide Liquid-Measuring Devices - Tentative Code 3-77

Note: In this section of Handbook 44, the reference temperature for the temperature compensation of refined 

petroleum products is shown as "15 C (60 F)." Although these values are not exact equivalents, they reflect 

industry usage when the SI and inch-pound units are used in measurements.
3.30. Liquid-Measuring Devices

3-2
3.30. Liquid-Measuring Devices

3-3

Sec. 3.30. Liquid-Measuring Devices

A. Application

A.1. - This code applies to:

(a) devices used for the measurement of liquids, including liquid fuels and lubricants, and

(b) wholesale devices used for the measurement and delivery of agri-chemical liquids such as fertilizers, feeds, 

herbicides, pesticides, insecticides, fungicides, and defoliants.

(Added 1985)

A.2. - This code does not apply to:

(a) meters mounted on vehicle tanks (see Sec. 3.31. Code for Vehicle-Tank Meters),

(b) devices used for dispensing liquefied petroleum gases (see Sec. 3.32. Code for Liquefied Petroleum Gas 

and Anhydrous Ammonia Liquid-Measuring Devices),

(c) devices used for dispensing other liquids that do not remain in a liquid state at atmospheric pressures and 

temperatures,

(d) water meters,

(e) devices used solely for dispensing a product in connection with operations in which the amount dispensed 

does not affect customer charges, or

(f) mass flow meters (see Sec. 3.37. Code for Mass Flow Meters.)

(Added 1994)

A.3. - In addition to the requirements of this code, liquid-measuring devices shall meet the requirements of Section 

1.10. General Code.

S. Specifications

S.1. Indicating and Recording Elements and Recorded Representations.

S.1.1. General. - A liquid-measuring device:

(a) shall be equipped with a primary indicating element, and

(b) may be equipped with a primary recording element.

S.1.2. Units. - A liquid-measuring device shall indicate, and record if the device is equipped to record, its 

deliveries in liters, gallons, quarts, pints, or binary-submultiples or decimal subdivisions of the liter or gallon.

(Amended 1987, 1994)

S.1.2.1. Retail Motor-Fuel Devices. - Deliveries shall be indicated and recorded, if the device is equipped 

to record, in liters or gallons and decimal subdivisions or fractional equivalents thereof.

(Added 1979)

S.1.2.2. Agri-Chemical Liquid Devices.
3.30. Liquid-Measuring Devices

3-4

S.1.2.2.1. Liquid Measure. - Deliveries shall be indicated and recorded in liters or gallons and 

decimal subdivisions or fractional equivalents thereof.

S.1.2.3. Value of Smallest Unit. - The value of the smallest unit of indicated delivery, and recorded 

delivery if the device is equipped to record, shall not exceed the equivalent of:

(a) 0.5 L (1 pt) on retail devices;

(b) 5 L (1 gal) on wholesale devices.

This requirement does not apply to manually operated devices equipped with stops or stroke-limiting 

means.

(Amended 1983 and 1986)

S.1.3. Advancement of Indicating and Recording Elements. - It shall not be possible to advance primary 

indicating and recording elements except by the mechanical operation of the device. Clearing a device by 

advancing its elements to zero is permitted, but only if:

(a) once started, the advancement movement cannot be stopped until zero is reached, and

(b) in the case of indicating elements only, such elements are automatically obscured until the elements 

reach the correct zero position. 

S.1.4. Graduations.

S.1.4.1. Length. - Graduations shall be varied in length so that they may be conveniently read.

S.1.4.2. Width. - In a series of graduations, the width of:

(a) every graduation shall be at least 0.2 mm (0.008 in) but not greater than the minimum clear interval

between graduations, and

(b) main graduations shall be not more than 50 percent greater than the width of subordinate graduations.

S.1.4.3. Clear Interval Between Graduations. -The clear interval between graduations shall be not less 

than 1.0 mm (0.04 in). If the graduations are not parallel, the measurement shall be made:

(a) along the line of movement of the tip of the index of the indicator as it passes over the graduations, or

(b) if the indicator extends over the entire length of the graduations, at the point of widest separation 

of the graduations.

S.1.5. Indicators.

S.1.5.1. Symmetry. - The portion of the index of an indicator associated with the graduations shall be 

symmetrical with respect to the graduations.

S.1.5.2. Length.

(a) If the indicator and the graduations are in different planes, the index of the indicator shall extend 

to each graduation with which it is to be used.

(b) If the indicator is in the same plane as the graduations, the distance between the index of the 

indicator and the ends of the graduations, measured along the line of the graduations, shall be not 

more than 1.0 mm (0.04 in).
3.30. Liquid-Measuring Devices

3-5

S.1.5.3. Width.

(a) The index of an indicator shall not be wider than the width of the narrowest graduation. 

[Nonretroactive as of January 1, 2002.]

(Amended 2000)

(b) If the index of an indicator extends over the entire length of a graduation, it shall be of uniform 

width throughout the portion that coincides with the graduation.

S.1.5.4. Clearance. - If the indicator and the graduations are in different planes, the clearance between the 

index of an indicator and the plane of the graduations shall be no greater than 1.5 mm (0.06 in).

S.1.5.5. Parallax. - Parallax effects shall be reduced to the practical minimum.

S.1.6. Operating Requirements, Retail Devices (Except Slow Flow Meters).

S.1.6.1. Indication of Delivery. - The device shall automatically show on its face the initial zero condition 

and the quantity delivered (up to the nominal capacity). 

However, the first 0.03 L (or 0.009 gal) of a delivery and its associated total sales price need not be 

indicated.

(Amended 1982)

S.1.6.2. Provisions for Power Loss.

S.1.6.2.1. Transaction Information. - In the event of a power loss, the information needed to complete any 

transaction in progress at the time of the power loss (such as the quantity and unit price, or sales price) 

shall be determinable for at least 15 minutes at the dispenser or at the console if the console is accessible 

to the customer.

[Nonretroactive as of January 1, 1983.]

S.1.6.2.2. User Information. - The device memory shall retain information on the quantity of fuel 

dispensed and the sales price totals during power loss.

[Nonretroactive as of January 1, 1983.]

S.1.6.3. Return to Zero.

(a) The primary indicating elements, and primary recording elements if the device is equipped to record, 

shall be readily returnable to a definite zero indication. However, a key-lock operated or other selfoperated device may be equipped with cumulative indicating or recording elements, provided that it is 

also equipped with a zero-return indicating element.

(b) It shall not be possible to return primary indicating elements, or primary recording elements beyond 

the correct zero position.

(Amended 1972)

S.1.6.4. Display of Unit Price and Product Identity.

S.1.6.4.1. Unit Price.

(a) A computing or money-operated device shall be able to display on each face the unit price at 

which the device is set to compute or to dispense.
3.30. Liquid-Measuring Devices

3-6

(b) Whenever a grade, brand, blend, or mixture is offered for sale from a device at more than one unit 

price, then all of the unit prices at which that product is offered for sale shall be displayed or shall 

be capable of being displayed on the dispenser using controls available to the customer prior to 

the delivery of the product. It is not necessary that all of the unit prices for all grades, brands, 

blends, or mixtures be simultaneously displayed prior to the delivery of the product. This 

subsection shall not apply to fleet sales, other contract sales, or truck refueling sales (e.g., sales 

from dispensers used to refuel trucks).

[Nonretroactive as of January 1, 1991.]

(Amended 1989 and 1997)

S.1.6.4.2. Product Identity.

(a) A device shall be able to conspicuously display on each side the identity of the product being 

dispensed.

(b) A device designed to dispense more than one grade, brand, blend, or mixture of product also shall be 

able to display on each side the identity of the grade, brand, blend, or mixture being dispensed.

S.1.6.5. Money-Value Computations.

(a) A computing device shall compute the total sales price at any single-purchase unit price (i.e., 

excluding fleet sales, other price contract sales, and truck stop dispensers used only to refuel trucks) 

for which the product being measured is offered for sale at any delivery possible within either the 

measurement range of the device or the range of the computing elements, whichever is less.

[Nonretroactive as of January 1, 1991]

(b) The analog sales price indicated for any delivered quantity shall not differ from a mathematically 

computed price (quantity x unit price = total sales price) by an amount greater than the value in Table 

1.

(Amended 1984, 1989, and 1993)

S.1.6.5.1. Money-Value Divisions, Analog. - The values of the graduated intervals representing money 

values on a computing type device shall be no greater than those in Table 1.

(Amended 1991)
3.30. Liquid-Measuring Devices

3-7

S.1.6.5.2. Money-Value Divisions, Digital. - A computing type device with digital indications shall 

comply with the requirements of paragraph G.S.5.5. Money Values, Mathematical Agreement, and the total 

price computation shall be based on quantities not exceeding 0.05 L for devices indicating in metric units 

and 0.01-gal. intervals for devices indicating in inch-pound units.

(Added 1980)

S.1.6.5.3. Auxiliary Elements. - If a system is equipped with auxiliary indications, all indicated money 

value divisions of the auxiliary element shall be identical with those of the primary element.

[Nonretroactive as of January 1, 1985.]

S.1.6.5.4. Selection of Unit Price. - Except for dispensers used exclusively for fleet sales, other price 

contract sales, and truck refueling (e.g., truck stop dispensers used only to refuel trucks), when a product 

or grade is offered for sale at more than one unit price through a computing device, the selection of the unit 

price shall be made prior to delivery using controls on the device or other customer-activated controls. A 

system shall not permit a change to the unit price during delivery of product.

[Nonretroactive as of January 1, 1991.]

(Added 1989)(Amended 1991, 1992, 1993, and 1996)

S.1.6.5.5. Display of Quantity and Total Price. - When a delivery is completed, the total price and 

quantity for that transaction shall be displayed on the face of the dispenser for at least 5 minutes or 

until the next transaction is initiated by using controls on the device or other customer-activated 

controls.

[Nonretroactive as of January 1, 1994.]

(Added 1992)(Amended 1996)

S.1.6.6. Agreement Between Indications. - When a quantity value indicated or recorded by an auxiliary 

element is a derived or computed value based on data received from a retail motor fuel dispenser, the value 

may differ from the quantity value displayed on the dispenser, provided the following conditions are met:

(a) all total money values for an individual sale that are indicated or recorded by the system agree; 

and

Table 1.

Money-Value Divisions and

Maximum Allowable Variations for Money-Value

Computations on Mechanical Analog Computers

Unit Price

Money Value

Division

Maximum

Allowable Variation

From To and including Design

Test

Field

Test

0 0.25/liter or

$1.00/gallon 1¢ ± 1¢ ± 1¢

0.25/liter or

$1.00/gallon

0.75/liter or

$3.00/gallon 1¢ or 2¢ ± 1¢ ± 2¢

0.75/liter or

$3.00/gallon

2.50/liter or

$10.00/gallon 1¢ or 2¢ ± 1¢ ± 2¢

0.75/liter or

$3.00/gallon

2.50/liter or

$10.00/gallon 5¢ ± 2 1/2¢ ± 5¢
3.30. Liquid-Measuring Devices

3-8

(b) within each element, the values indicated or recorded meet the formula (quantity x unit price = 

total sales price) to the closest cent.

[Nonretroactive as of January 1, 1988.]

(Added 1985)(Amended 1987 and 1988)

S.1.6.7. Recorded Representations. - Except for fleet sales and other price contract sales, a printed receipt 

providing the following information shall be available through a built-in or separate recording element for 

all transactions conducted with point-of-sale systems or devices activated by debit cards, credit cards, 

and/or cash:

(a) the total volume of the delivery,

(b) the unit price,

(c) the total computed price, and

(d) the product identity by name, symbol, abbreviation, or code number.

[Nonretroactive as of January 1, 1986.]

(Added 1985) (Amended 1997)

S.1.6.8. Lubricant Devices, Travel of Indicator. -The indicator shall move at least 2.5 cm (1 in) in 

relation to the graduations, if provided, for a delivery of 0.5 L (1 pt).

S.1.7. Operating Requirements, Wholesale Devices Only.

S.1.7.1. Travel of Indicator. - A wholesale device shall be readily operable to deliver accurately any 

quantity from 200 L (50 gal) to the capacity of the device. If the most sensitive element of the indicating 

system utilizes an indicator and graduations, the relative movement of these parts corresponding to a 

delivery of 4 L (1 gal) shall be not less than 5 mm (0.20 in).

(Amended 1987)

S.1.7.2. Money Values-Mathematical Agreement. - Any digital money-value indication and any 

recorded money value on a computing-type device shall be in mathematical agreement with its associated 

quantity indication or representation to within one cent of money value.

S.2. Measuring Elements.

S.2.1. Vapor Elimination.

(a) A liquid-measuring device shall be equipped with a vapor or air eliminator or other automatic means to 

prevent the passage of vapor and air through the meter.

(b) Vent lines from the air or vapor eliminator shall be made of metal tubing or other rigid material.

(Amended 1975)

S.2.1.1. Vapor Elimination on Loading Rack Metering Systems.

(a) A loading rack metering system shall be equipped with a vapor or air eliminator or other 

automatic means to prevent the passage of vapor and air through the meter unless the system is 

designed or operationally controlled by a method, approved by the weights and measures 

jurisdiction having control over the device, such that air and/or vapor cannot enter the system.

(b) Vent lines from the air or vapor eliminator (if present) shall be made of metal tubing or other 

rigid material.

(Added 1994)
3.30. Liquid-Measuring Devices

3-9

S.2.2. Provision for Sealing. - Adequate provision shall be made for an approved means of security (e.g., data 

change audit trail) or physically applying security seals in such a manner that no adjustment may be made of: 

(a) any measurement element, or

(b) any adjustable element for controlling delivery rate when such rate tends to affect the accuracy of 

deliveries.

When applicable, the adjusting mechanism shall be readily accessible for purposes of affixing a security

seal.

(c) Audit trails shall use the format set forth in Table S.2.2. [Nonretroactive as of January 1, 1995.]

(Amended 1991, 1993, and 1995)

S.2.3. Directional Flow Valves. - Valves intended to prevent reversal of flow shall be automatic in operation.

S.2.4. Stop Mechanism.

S.2.4.1. Indication. - The delivery for which the device is set shall be conspicuously indicated.

(Amended 1983)

S.2.4.2. Stroke Limiting Elements. - Stops or other stroke limiting elements subject to direct pressure or 

impact shall be: 

(a) made secure by positive, nonfrictional engagement of these elements; and

(b) adjustable to provide for deliveries within tolerances.

(Amended 1983) 

S.2.4.3. Setting. - If two or more stops or other elements may be selectively brought into operation to 

permit predetermined quantities of deliveries,

(a) the position for the proper setting of each such element shall be accurately defined; and

(b) any inadvertent displacement from the proper setting shall be obstructed.

(Amended 1983)
3.30. Liquid-Measuring Devices

3-10

S.2.5. Zero-Set-Back Interlock, Retail Motor-Fuel Devices. - A device shall be constructed so that:

(a) after a delivery cycle has been completed by moving the starting lever to any position that shuts off the 

device, an automatic interlock prevents a subsequent delivery until the indicating elements, and 

recording elements if the device is equipped and activated to record, have been returned to their zero 

positions;

(b) the discharge nozzle cannot be returned to its designed hanging position (that is, any position where 

the tip of the nozzle is placed in its designed receptacle and the lock can be inserted) until the starting 

lever is in its designed shut-off position and the zero-set-back interlock has been engaged; and

(c) in a system with more than one dispenser supplied by a single pump, an effective automatic control 

valve in each dispenser prevents product from being delivered until the indicating elements on that 

dispenser are in a correct zero position.

(Amended 1981 and 1985)

Table S.2.2. Categories of Device and Methods of Sealing

Categories of Device Method of Sealing

Category 1: No remote configuration capability. Seal by physical seal or two event counters: one for calibration 

parameters and one for configuration parameters.

Category 2: Remote configuration capability, 

but access is controlled by physical hardware. 

Device shall clearly indicate that it is in the 

remote configuration mode and record such 

message if capable of printing in this mode. 

[Category 2 applies only to devices 

manufactured prior to January 1, 2005. Devices 

with remote configuration capability 

manufactured after that date must meet the 

sealing requirements outlined in Category 3. 

Devices without remote configuration capability 

manufactured after that date will be required to 

meet the minimum criteria outlined in 

Category 1.]

[The hardware enabling access for remote communication must 

be on-site. The hardware must be sealed using a physical seal or 

an event counter for calibration parameters and an event counter 

for configuration parameters. The event counters may be located 

either at the individual measuring device or at the system 

controller; however, an adequate number of counters must be 

provided to monitor the calibration and configuration parameters 

of the individual devices at a location. If the counters are located

in the system controller rather than at the individual device, 

means must be provided to generate a hard copy of the 

information through an on-site device.]*

[*Nonretroactive as of January 1, 1996]

Category 3: Remote configuration capability 

access may be unlimited or controlled through a 

software switch (e.g., password).

The device shall clearly indicate that it is in the 

remote configuration mode and record such 

message if capable of printing in this mode or 

shall not operate while in this mode.

[Nonretroactive as of January 1, 2001]

Nonretroactive as of January 1, 2005, all devices 

with remote configuration capability must 

comply with the sealing requirements of 

Category 3.

An event logger is required in the device; it must include an event 

counter (000 to 999), the parameter ID, the date and time of the 

change, and the new value of the parameter. A printed copy of the 

information must be available through the device or through 

another on-site device. The event logger shall have a capacity to 

retain records equal to ten times the number of sealable 

parameters in the device, but not more than 1000 records are 

required. (Note: Does not require 1000 changes to be stored for 

each parameter.)

[Nonretroactive as of January 1, 1995.] (Table Added 1993) (Amended 1995, 1998, and 1999)
3.30. Liquid-Measuring Devices

3-11

S.2.6. Temperature Determination and Wholesale Devices. - For test purposes, means shall be provided to 

determine the temperature of the liquid either:

(a) in the liquid chamber of the meter, or 

(b) immediately adjacent to the meter in the meter inlet or discharge line.

[Nonretroactive as of January 1, 1985.]

(Added 1984)(Amended 1986)

S.2.7. Wholesale Devices Equipped with Automatic Temperature Compensators.

S.2.7.1. Automatic Temperature Compensation. - A device may be equipped with an automatic means 

for adjusting the indication and registration of the measured volume of product to the volume at 15 C (60 

F).

S.2.7.2. Provision for Deactivating. - On a device equipped with an automatic temperature-compensating 

mechanism that will indicate or record only in terms of gallons compensated to 15 C (60 F), provision 

shall be made for deactivating the automatic temperature-compensating mechanism so that the meter can 

indicate, and record if it is equipped to record, in terms of the uncompensated volume. (Amended 1972)

S.2.7.3. Provision for Sealing Automatic Temperature Compensating Systems. - Provision shall be 

made for applying security seals in such a manner that an automatic temperature-compensating system 

cannot be disconnected and that no adjustment may be made to the system without breaking the seal.

S.2.7.4. Temperature Determination with Automatic Temperature Compensation. - For test purposes, 

means shall be provided (e.g., thermometer well) to determine the temperature of the liquid either:

(a) in the liquid chamber of the meter, or 

(b) immediately adjacent to the meter in the meter inlet or discharge line.

(Amended 1987)

S.2.8. Exhaustion of Supply, Lubricant Devices Other than Meter Types. - When the level of the supply of 

lubricant becomes so low as to compromise the accuracy of measurement, the device shall:

(a) become inoperable automatically, or

(b) give a conspicuous and distinct warning. 

S.3. Discharge Lines and Valves.

S.3.1. Diversion of Measured Liquid. - No means shall be provided by which any measured liquid can be 

diverted from the measuring chamber of the meter or its discharge line. Two or more delivery outlets may be 

installed only if automatic means are provided to ensure that:

(a) liquid can flow from only one outlet at a time, and

(b) the direction of flow for which the mechanism may be set at any time is clearly and conspicuously 

indicated.

A manually controlled outlet that may be opened for purging or draining the measuring system or for 

recirculating product in suspension shall be permitted only when the system is measuring food products or agrichemicals. Effective means shall be provided to prevent passage of liquid through any such outlet during 

normal operation of the measuring system and to inhibit meter indications (or advancement of indications) and 

recorded representations while the outlet is in operation.

(Amended 1991, 1995, and 1996)
3.30. Liquid-Measuring Devices

3-12

S.3.2. Exceptions. - The provisions of S.3.1. Diversion Prohibited shall not apply to truck refueling devices 

when diversion of flow to other than the receiving vehicle cannot readily be accomplished and is readily 

apparent. Allowable deterrents include, but are not limited to, physical barriers to adjacent driveways, visible 

valves, or lighting systems that indicate which outlets are in operation, and explanatory signs;

(Amended 1982, 1990,1991, and 2002)

S.3.3. Pump-Discharge Unit. - A pump-discharge unit equipped with a flexible discharge hose shall be of the 

wet-hose type.

S.3.4. Gravity-Discharge Unit. - On a gravity-discharge unit:

(a) the discharge hose or equivalent pipe shall be of the dry-hose type with no shutoff valve at its outlet 

end unless the hose or pipe drains to the same level under all conditions of use;

(b) the dry hose shall be sufficiently stiff and only as long as necessary to facilitate drainage;

(c) an automatic vacuum breaker, or equivalent mechanism, shall be incorporated to prevent siphoning 

and to ensure rapid and complete drainage; and

(d) the inlet end of the hose or outlet pipe shall be high enough to ensure complete drainage.

S.3.5. Discharge Hose, Reinforcement. - A discharge hose shall be reinforced so that the performance of the 

device is not affected by the expansion or contraction of the hose.

S.3.6. Discharge Valve. - A discharge valve may be installed in the discharge line only if the device is of the 

wet-hose type. Any other shutoff valve on the discharge side of the meter shall be of the automatic or semiautomatic predetermined-stop type or shall be operable only:

(a) by means of a tool (but not a pin) entirely separate from the device, or

(b) by mutilation of a security seal with which the valve is sealed open.

S.3.7. Antidrain Means. - In a wet-hose pressure-type device, means shall be incorporated to prevent the 

drainage of the discharge hose.

(Amended 1990)

S.4. Marking Requirements.

S.4.1. Limitation on Use. - The limitations on its use shall be clearly and permanently marked on any device 

intended to measure accurately only:

(a) products having particular properties; or

(b) under specific installation or operating conditions; or

(c) when used in conjunction with specific accessory equipment.

S.4.2. Air Pressure. - If a device is operated by air pressure, the air pressure gauge shall show by special 

graduations or other means the maximum and minimum working pressures recommended by the manufacturer.

S.4.3. Wholesale Devices.

S.4.3.1. Discharge Rates. - A wholesale device shall be marked to show its designed maximum and 

minimum discharge rates. However, the minimum discharge rate shall not exceed 20 percent of the maximum discharge rate. 
3.30. Liquid-Measuring Devices

3-13

S.4.3.2. Temperature Compensation. - If a device is equipped with an automatic temperature compensator, the primary indicating elements, recording elements, and recorded representation shall be clearly and 

conspicuously marked to show that the volume delivered has been adjusted to the volume at 15 C (60 F).

S.4.4. Retail Devices.

S.4.4.1. Discharge Rates. - On a retail device with a designed maximum discharge rate of 115 L (30 gal) 

per minute or greater, the maximum and minimum discharge rates shall be marked on an exterior surface 

of the device and shall be visible after installation. The minimum discharge rate shall not exceed 20 

percent of the maximum discharge rate.

[Nonretroactive as of January 1, 1985.]

(Added 1984)(Amended 2002)

S.4.4.2. Location of Marking Information; Retail Motor-Fuel Dispensers. – The required marking 

information in the General Code, Paragraph G-S.1. shall appear as follows:

(a) Placement of this information shall not be on a portion of the device that can be readily removed 

or interchanged without the use of a tool separate from the device.

(b) The information shall appear 24 inches to 60 inches from the base of the dispenser when placed 

on the outside of the device.

(c) When placed behind an access door or panel the information shall appear 24 inches to 60 inches 

from the base of the dispenser in a readily legible position. The use of a dispenser key shall not be 

considered a tool separate from the device.

[Nonretroactive as of January 1, 2003]

(Added 2002)

S.5. Totalizers for Retail Motor-Fuel Dispensers. - Retail motor-fuel dispensers shall be equipped with a 

nonresettable totalizer for the quantity delivered through the metering device. 

[Nonretroactive as of January 1, 1995.]

(Added 1993; Amended 1994)

N. Notes

N.1. Test Liquid.

N.1.1. Type of Liquid. - The liquid used for testing a liquid-measuring device shall be the type the device is 

used to measure, or another liquid with the same general physical characteristics.

N.1.2. Labeling. - Following the completion of a successful examination of a wholesale device, the weights 

and measures official should attach a label or tag indicating the type of liquid used during the test.

N.2. Volume Change. - Care shall be taken to minimize changes in volume of the test liquid due to temperature 

changes and evaporation losses.

N.3. Test Drafts.

N.3.1. Retail Piston-Type and Visible-Type Devices. - Test drafts shall include the full capacity delivery and 

each intermediate delivery for which the device is designed.

N.3.2. Slow Flow Meters. - Test drafts shall be equal to at least four times the minimum volume that can be

measured and indicated through either a visible indication or an audible signal.
3.30. Liquid-Measuring Devices

3-14

N.3.3. Lubricant Devices. - Test drafts shall be 1 L (1 qt). Additional test drafts may include 0.5 L (1 pt), 4 L 

(4 qt), and 6 L (6 qt).

N.3.4. Other Retail Devices. - On devices with a designed maximum discharge rate of:

(a) less than 80 L (20 gal) per minute, tests shall include drafts of one or more amounts, including a draft 

of at least 19 L (5 gal).

(b) 80 L (20 gal) per minute or greater, tests shall include drafts of one or more amounts, including a draft 

of at least the amount delivered by the device in one minute at the maximum flow rate of the installation. 

(Amended 1984)

N.3.5. Wholesale Devices. - The delivered quantity should be equal to at least the amount delivered by the 

device in one minute at its maximum discharge rate, and shall in no case be less than 200 L (50 gal).

(Amended 1987 and 1996)

N.4. Testing Procedures.

N.4.1. Normal Tests. - The "normal" test of a device shall be made at the maximum discharge flow rate 

developed under the conditions of installation. Any additional tests conducted at flow rates down to and 

including one-half of the sum of the maximum discharge flow rate and the rated minimum discharge flow rate 

shall be considered normal tests.

(Amended 1991)

N.4.1.1. Wholesale Devices Equipped with Automatic Temperature-Compensating Systems. - On 

wholesale devices equipped with automatic temperature compensating systems, normal tests shall be 

conducted:

(a) by comparing the compensated volume indicated or recorded to the actual delivered volume 

corrected to 15 C (60 F); and 

(b) with the temperature compensating system deactivated, comparing the uncompensated volume 

indicated or recorded to the actual delivered volume.

The first test shall be performed with the automatic temperature-compensating system operating in the "as 

found" condition.

On devices that indicate or record both the compensated and uncompensated volume for each delivery, the 

tests in (a) and (b) may be performed as a single test.

(Amended 1987)

N.4.1.2. Repeatability Tests. - Tests for repeatability should include a minimum of three consecutive test 

drafts of approximately the same size and be conducted under controlled conditions where variations in 

factors, such as temperature, pressure, and flow rate are reduced to the extent that they will not affect the 

results obtained.

(Added 2001)

N.4.2. Special Tests. - "Special" tests, to develop the operating characteristics of a liquid-measuring device and 

any special elements and accessories attached to or associated with the device, shall be made as circumstances 

require. Any test except as set forth in N.4.1. shall be considered a special test. 

N.4.2.1. Slow-Flow Meters. - A "special" test shall be made at a flow rate:

(a) not larger than twice the actual minimum flow rate, and 
3.30. Liquid-Measuring Devices

3-15

(b) not smaller than the actual minimum flow rate of the installation.

N.4.2.2. Retail Motor-Fuel Devices.

(a) Devices with a flow-rate capacity less than 100 L (25 gal) per minute shall have a "special" test 

performed at the slower of the following rates:

(1) 19 L (5 gal) per minute, or 

(2) the minimum discharge rate marked on the device, or 

(3) the minimum discharge rate at which the device will deliver when equipped with an 

automatic discharge nozzle set at its slowest setting.

(b) Devices marked with a flow-rate capacity 100 L (25 gal) or more per minute, shall have a 

"special" test performed at the slowest of the following rates:

(1) the minimum discharge rate marked on the device, or

(2) the minimum discharge rate at which the device will deliver when equipped with an automatic

discharge nozzle set at its slowest setting.

(Added 1984)

N.4.2.3. Other Retail Devices. - "Special" tests of other retail devices shall be made at the slower of the 

following rates:

(a) 50 percent of the maximum discharge rate developed under the conditions of installation, or

(b) the minimum discharge rate marked on the device.

N.4.2.4. Wholesale Devices. - "Special" tests shall be made to develop the operating characteristics of a 

measuring system and any special associated or attached elements and accessories. "Special" tests shall 

include a test at the slower of the following rates:

(a) 20 percent of the marked maximum discharge rate; or

(b) the minimum discharge rate marked on the device.

N.4.3. Money-Value Computation Tests.

N.4.3.1. Laboratory Tests. - When testing the device in the laboratory:

(a) compliance with paragraph S.1.6.5., Money Value Computations, shall be determined by using the 

cone gear as a reference for the total quantity delivered;

(b) the indicated quantity shall agree with the cone gear representation with the index of the indicator 

within the width of the graduation; and

(c) the maximum allowable variation of the indicated sales price shall be as shown in Table 1. 

(Amended 1984)

N.4.3.2. Field Tests. - In the conduct of field tests to determine compliance with paragraph S.1.6.5., the 

maximum allowable variation in the indicated sales price shall be as shown in Table 1.

(Added 1982; Amended 1984)
3.30. Liquid-Measuring Devices

3-16

N.5. Temperature Correction on Wholesale Devices. - Corrections shall be made for any changes in volume 

resulting from the differences in liquid temperatures between time of passage through the meter and time of 

volumetric determination in the prover. When adjustments are necessary, appropriate petroleum measurement tables 

should be used.

(Amended 1974)

T. Tolerances

T.1. Application to Underregistration and to Overregistration. - The tolerances hereinafter prescribed shall be 

applied to errors of underregistration and errors of overregistration, whether or not a device is equipped with an 

automatic temperature compensator.

T.2. Tolerance Values. Maintenance, Acceptance, and Special Test Tolerances shall be as shown in Table T.2.

Table T.2. Accuracy Classes for Liquid Measuring Devices Covered in

NIST Handbook 44 Section 3.30

Accuracy 

Class Application Acceptance Tolerance

Maintenance 

Tolerance

Special 

Test 

Tolerance

0.3

Petroleum products including large capacity motor 

fuel devices (flow rates over 115 L/min (30 gpm))**, 

heated products at or greater than 50 °C asphalt at 

or below temperatures 50 °C, all other liquids not 

shown where the typical delivery is over 200 L (50 

gal)

0.2 % 0.3 % 0.5 %

0.3A Asphalt at temperatures greater than 50 °C 0.3 % 0.3 % 0.5 %

0.5*

Petroleum products delivered from small capacity 

(at 4 L/min (1 gpm) through 115 L/min (30 gpm))** 

motor-fuel devices, agri-chemical liquids, and all 

other applications not shown.

0.3 % 0.5 % 0.5%

1.1

Petroleum products and other normal liquids from 

devices with flow rates** less than 1 gpm and devices 

designed to deliver less than one gallon.

0.75 % 1.0 % 1.25%

*The maintenance tolerances on normal and special tests for 5-gallon and 10-gallon test drafts are 6 cubic 

inches and 11 cubic inches, respectively. Acceptance tolerances on normal and special tests are 3 cubic inches 

and 5.5 cubic inches. 

** Flow rate refers to designed or marked maximum flow rate.

(Added 2002)

T.3 Repeatability. - When multiple tests are conducted at approximately the same flow rate and draft size, the 

range of the test results for the flow rate shall not exceed 40 percent of the absolute value of the maintenance

tolerance and the results of each test shall be within the applicable tolerance. This tolerance does not apply to the 

test of the automatic temperature compensating system. See also N.4.1.2.

(Added 1992) (Amended 2001and 2002)
3.30. Liquid-Measuring Devices

3-17

T.4. Automatic Temperature Compensating Systems. - The difference between the meter error (expressed as a 

percentage) for results determined with and without the automatic temperature compensating system activated shall 

not exceed:

(a) 0.2 percent for mechanical automatic temperature compensating systems; and

(b) 0.1 percent for electronic automatic temperature compensating systems.

The delivered quantities for each test shall be approximately the same size. The results of each test shall be within 

the applicable acceptance or maintenance tolerance.

[Nonretroactive as of January 1, 1988.]

(Added 1987) (Amended 1992, 1996 and 2002)

UR. User Requirements

UR.1. Selection Requirements.

UR.1.1. Discharge Hose.

UR.1.1.1. Length. - The length of the discharge hose on a retail motor-fuel device:

(a) shall be measured from its housing or outlet of the discharge line to the inlet of the discharge 

nozzle;

(b) shall be measured with the hose fully extended if it is coiled or otherwise retained or connected 

inside a housing; and

(c) shall not exceed 5.5 m (18 ft) unless it can be demonstrated that a longer hose is essential to 

permit deliveries to be made to receiving vehicles or vessels.

An unnecessarily remote location of a device shall not be accepted as justification for an abnormally long 

hose.

(Amended 1972 and 1987)

UR.1.1.2. Marinas and Airports.

UR.1.1.2.1. Length. - The length of the discharge hose shall be as short as practicable, and shall not 

exceed 15 m (50 ft) unless it can be demonstrated that a longer hose is essential.

UR.1.1.2.2. Protection. - Discharge hoses exceeding 8 m (26 ft) in length shall be adequately 

protected from weather and other environmental factors when not in use.

(Made retroactive 1974 and amended 1984)

UR.2. Installation Requirements.

UR.2.1. Manufacturer's Instructions. - A device shall be installed in accordance with the manufacturer's 

instructions, and the installation shall be sufficiently secure and rigid to maintain this condition.

(Added 1987)

UR.2.2. Discharge Rate. - A device shall be installed so that the actual maximum discharge rate will not 

exceed the rated maximum discharge rate. Automatic means for flow regulation shall be incorporated in the 

installation if necessary.
3.30. Liquid-Measuring Devices

3-18

UR.2.3. Suction Head. - A piston-type device shall be installed so that the total effective suction head will not 

be great enough to cause vaporization of the liquid being dispensed under the highest temperature and lowest 

barometric pressure likely to occur.

UR.2.4. Diversion of Liquid Flow. - A motor-fuel device equipped with two delivery outlets used exclusively 

in the fueling of trucks shall be so installed that any diversion of flow to other than the receiving vehicle cannot 

be readily accomplished and is readily apparent. Allowable deterrents include, but are not limited to, physical 

barriers to adjacent driveways, visible valves, or lighting systems that indicate which outlets are in operation, 

and explanatory signs.

(Amended 1991)

UR.2.5. Product Storage Identification.

(a) The fill connection for any petroleum product storage tank or vessel supplying motor-fuel devices shall 

be permanently, plainly, and visibly marked as to product contained.

(b) When the fill connection device is marked by means of a color code, the color code key shall be 

conspicuously displayed at the place of business.

(Added 1975 and Amended 1976)

UR.3. Use of Device.

UR.3.1. Return of Indicating and Recording Elements to Zero. - On any dispenser used in making 

retail deliveries, the primary indicating element, and recording element if so equipped, shall be returned to 

zero before each delivery.

Exceptions to this requirement are totalizers on key-lock-operated or other self-operated dispensers and the 

primary recording element if the device is equipped to record.

UR.3.2. Unit Price and Product Identity.

(a) The following information shall be conspicuously displayed or posted on the face of a retail 

dispenser used in direct sale:

(1) except for dispensers used exclusively for fleet sales, other price contract sales, and truck 

refueling (e.g., truck stop dispensers used only to refuel trucks), all of the unit prices at which 

the product is offered for sale; and

(2) in the case of a computing type or money-operated type, the unit price at which the dispenser 

is set to compute.

Provided that the dispenser complies with S.1.6.4.1., it is not necessary that all the unit prices for 

all grades, brands, blends, or mixtures be simultaneously displayed or posted.

(b) The following information shall be conspicuously displayed or posted on each side of a retail 

dispenser used in direct sale:

(1) the identity of the product in descriptive commercial terms, and

(2) the identity of the grade, brand, blend, or mixture that a multi-product dispenser is set to 

deliver.

(Amended 1972, 1983, 1987, 1989, 1992, and 1993)
3.30. Liquid-Measuring Devices

3-19

UR.3.3. Computing Device.

(a) Any computing device used in an application where a product or grade is offered for sale at more than 

one unit price (excluding fleet sales and other price contract sales), shall be used only for sales for 

which the device computes and displays the sales price for the selected transaction. 

(Added 1989) (Amended 1992)

(Became Retroactive 1999)

(b) A truck stop dispenser used exclusively for refueling trucks is exempt from the requirements in (a) if 

all purchases of fuel are accompanied by a printed receipt of the transaction containing the applicable 

price per gallon, the total gallons delivered, and the total price of the sale.

(Added 1993)

(c) Unless a truck stop dispenser used exclusively for refueling trucks complies with S.1.6.4.1. (Display of 

Unit Price), the price posted on the dispenser and the price at which the dispenser is set to compute 

shall be the highest price for any transaction which may be conducted.

(Added 1993)

UR.3.4. Printed Ticket. - The total price, the total volume of the delivery, and the price per gallon or liter shall 

be shown, either printed or in clear hand script, on any printed ticket issued by a device and containing any one 

of these values.

(Amended 2001)

UR.3.5. Steps After Dispensing. - After delivery to a customer from a retail motor-fuel device:

(a) the starting lever shall be returned to its shutoff position and the zero-set-back interlock engaged; and

(b) the discharge nozzle shall be returned to its designed hanging position unless the primary indicating 

elements, and recording elements, if the device is equipped and activated to record, have been returned 

to a definite zero indication.

UR.3.6. Temperature Compensation, Wholesale.

UR.3.6.1. Automatic.

UR.3.6.1.1. When to be Used. - If a device is equipped with a mechanical automatic temperature compensator, it shall be connected, operable, and in use at all times. An electronic or mechanical automatic 

temperature compensating system may not be removed, nor may a compensated device be replaced with an 

uncompensated device, without the written approval of the responsible weights and measures jurisdiction.

[Note: This requirement does not specify the method of sale for product measured through a meter.]

(Amended 1989)

UR.3.6.1.2. Invoices.

(a) A written invoice based on a reading of a device that is equipped with an automatic temperature 

compensator shall show that the volume delivered has been adjusted to the volume at 15 C (60 

F).

(b) The invoice issued from an electronic wholesale device equipped with an automatic temperature 

compensating system shall also indicate: (1) the API gravity, specific gravity or coefficient of 

expansion for the product; (2) product temperature; and (3) gross reading.

(Amended 1987)
3.30. Liquid-Measuring Devices

3-20

UR.3.6.2. Nonautomatic.

UR.3.6.2.1. Temperature Determination. - If the volume of the product delivered is adjusted to the 

volume at 15 C (60 F), the product temperature shall be taken during the delivery in:

(a) the liquid chamber of the meter, or

(b) the meter inlet or discharge line adjacent to the meter, or 

(c) the compartment of the receiving vehicle at the time it is loaded.

UR.3.6.2.2. Invoices. - The accompanying invoice shall indicate that the volume of the product has 

been adjusted for temperature variations to a volume at 15 C (60 F) and shall also state the product 

temperature used in making the adjustment.
3.30. Liquid-Measuring Devices

3-21

Liquid-Measuring Device Code Index

Acceptance ........................................................16, 17

Adjustable element ....................................................9

Advancement.......................................................4, 11

Agreement .............................................................7, 8

Agri-chemical ................................................3, 11, 16

Antidrain means.......................................................12

Automatic ........ 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 19

Automatic temperature compensating systems.11, 14, 

17

Automatic temperature compensation .....................11

Auxiliary elements.....................................................7

Blend ...................................................................6, 18

Clear interval .............................................................4

Clearance ...................................................................5

Computing device............................................6, 7, 19

Directional flow valves..............................................9

Discharge hose...................................................12, 17

Discharge lines ........................................................11

Discharge rate..................................12, 13, 14, 15, 17

Discharge rates ........................................................13

Dry hose...................................................................12

Fleet sales ..............................................6, 7, 8, 18, 19

Grade .........................................................6, 7, 18, 19

Graduations..................................................4, 5, 8, 12

Gravity-discharge unit .............................................12

Index of an indicator..............................................4, 5

Indicating element ...........................3, 4, 5, 10, 13, 18

Indicators...................................................................4

Installation requirements .........................................17

Interlock.............................................................10, 19

Invoices..............................................................19, 20

Key-lock ..............................................................5, 18

Lubricant devices...........................................8, 11, 14

Maintenance .......................................................16,17

Marking requirements..............................................12

Mass.......................................................................1, 3

Mass flow meters...................................................1, 3

Measuring elements...................................................8

Money values-mathematical agreement ....................8

Money-value computation...................................6, 15

Money-value computations .......................................6

Money-value divisions ..........................................6, 7

Motor-fuel device ..................3, 10, 15, 16, 17, 18, 19

Nonautomatic ..........................................................20

Normal tests.............................................................14

Operating requirements .........................................5, 8

Parallax......................................................................5

Power loss..................................................................5

Price contract sales ...................................6, 8, 18, 19

Primary indicating element..................3, 5, 13, 18, 19

Printed ticket............................................................19

Product identity ...........................................5, 6, 8, 18

Pump-discharge unit................................................12

Quantity .......................................5, 6, 7, 8, 13, 14, 15

Recording element.................3, 4, 5, 8, 10, 13, 18, 19

Repeatability......................................................14, 16

Retail devices.......................................4, 5, 13, 14, 15

Retail motor-fuel device ....................3, 10, 15, 17, 19

Retail motor-fuel dispensers....................................13

Seal ..........................................................9, 10, 11, 12

Sealing ...........................................................9, 10, 11

Security..........................................................9, 11, 12

Slow flow meters.................................................5, 13

Special tests.......................................................14, 16

Stop mechanism.........................................................9

Temperature correction............................................16

Temperature determination................................11, 20

Test drafts....................................................13, 14, 16

Tolerances............................................................9, 16

Total price............................................................7, 19

Totalizers...........................................................13, 18

Truck refueling ..........................................6, 7, 12, 18

Unit price ...........................................5, 6, 7, 8, 18, 19

User information........................................................5

Valves......................................................9, 11, 12, 18

Vapor elimination......................................................8

Wet-hose..................................................................12

Wholesale devices ...............3, 4, 8, 11, 12, 14, 15, 16

Zero-set-back interlock......................................10, 19
3.31. Vehicle-Tank Meters

3-23

Sec. 3.31. Vehicle-Tank Meters

A. Application

A.1. - This code applies to meters mounted on vehicle tanks including those used for the measurement and delivery of 

petroleum products or agri-chemical liquids such as fertilizers, feeds, pesticides, defoliants, and bulk deliveries of water.

(Amended 1985 and 1995)

A.2. - This code does not apply to the following devices:

(a) Devices used for dispensing liquefied petroleum gases (for which see Sec. 3.32; Code for Liquefied Petroleum 

Gas and Anhydrous Ammonia Liquid-Measuring Devices), or other liquids that do not remain in a liquid state at 

atmospheric pressures and temperatures.

(b) Devices used solely for dispensing a product in connection with operations in which the amount dispensed does 

not affect customer charges.

(c) Vehicle tanks used as measures (for which see Sec. 4.40; Code for Vehicle Tanks Used as Measures).

(d) Mass flow meters (see Sec. 3.37. Code for Mass Flow Meters)

(Added 1994)

A.3. - See also Sec. 1.10; General Code requirements.

S. Specifications

S.1. Design of Indicating and Recording Elements and of Recorded Representations.

S.1.1. Primary Elements.

S.1.1.1. General. - A meter shall be equipped with a primary indicating element and may also be equipped with 

a primary recording element.

[Note: Except for systems used solely for the sale of aviation fuel into aircraft and for aircraft-related operations, 

vehicle-tank meters shall be equipped with a primary recording element as required by paragraph UR.2.2.] 

(Amended 1993)

S.1.1.2. Units. -

(a) A meter shall indicate, and record if the meter is equipped to record, its deliveries in terms of liters 

(gallons). Fractional parts of the liter (gallon) shall be in terms of either decimal or binary subdivisions.

(b) When it is an industry practice to purchase and sell milk by weight based upon 1.03 kg/L (8.6 lb/gal), 

the primary indicating element may indicate in kilograms (pounds) and decimal kilograms (pounds). 

The weight value division shall be a decimal multiple or submultiple of 1, 2, or 5. (See S.5.5.)

S.1.1.3. Value of Smallest Unit. - The value of the smallest unit of indicated delivery, and recorded delivery if 

the meter is equipped to record, shall not exceed the equivalent of:

(a) 0.5 L (0.1 gal) or 0.5 kg (1 lb) on milk-metering systems 

(b) 0.5 L (0.1 gal) on meters with a rated maximum flow rate of 500 L/min (100 gal/min) or less used for 

retail deliveries of liquid fuel, or

(c) 5 L (1 gal) on other meters.

(Amended 1989 and 1994)
3.31. Vehicle-Tank Meters

3-24

S.1.1.4. Advancement of Indicating and Recording Elements. - Primary indicating and recording elements 

shall be susceptible to advancement only by the mechanical operation of the meter. However, a meter may be 

cleared by advancing its elements to zero, but only if:

(a) the advancing movement, once started, cannot be stopped until zero is reached, or

(b) in the case of indicating elements only, such elements are automatically obscured until the elements 

reach the correct zero position.

S.1.1.5. Return to Zero. - Primary indicating elements shall be readily returnable to a definite zero indication. 

Means shall be provided to prevent the return of primary indicating elements, and of primary recording elements 

if these are returnable to zero, beyond their correct zero position.

S.1.2. Graduations.

S.1.2.1. Length. - Graduations shall be so varied in length that they may be conveniently read.

S.1.2.2. Width. - In any series of graduations, the width of a graduation shall in no case be greater than the 

width of the minimum clear interval between graduations, and the width of main graduations shall be not more 

than 50 percent greater than the width of subordinate graduations. Graduations shall in no case be less than 

0.2 mm (0.008 in) wide.

S.1.2.3. Clear Interval Between Graduations. - The clear interval shall be not less than 2.5 mm (0.10 in). If 

the graduations are not parallel, the measurement shall be made:

(a) along the line of relative movement between the graduations at the end of the indicator, or

(b) if the indicator is continuous, at the point of widest separation of the graduations.

(Amended 1986)

S.1.3. Indicators.

S.1.3.1. Symmetry. - The index of an indicator shall be symmetrical with respect to the graduations at least 

throughout that portion of its length associated with the graduations.

S.1.3.2. Length. - The index of an indicator shall reach to the finest graduations with which it is used, unless the 

indicator and the graduations are in the same plane, in which case the distance between the end of the indicator 

and the ends of the graduations, measured along the line of the graduations, shall be not more than 1.0 mm 

(0.04 in).

S.1.3.3. Width. - The width of the index of an indicator in relation to the series of graduations with which it is 

used shall be not greater than:

(a) the width of the narrowest graduation*, and

[*Nonretroactive as of January 1, 2002]

(Amended 2001)

(b) the width of the minimum clear interval between graduations.

When the index of an indicator extends along the entire length of a graduation, that portion of the index of the 

indicator that may be brought into coincidence with the graduation shall be of the same width throughout the 

length of the index that coincides with the graduation.

S.1.3.4. Clearance. - The clearance between the index of an indicator and the graduations shall in no case be 

more than 1.5 mm (0.06 in).

S.1.3.5. Parallax. - Parallax effects shall be reduced to the practicable minimum.
3.31. Vehicle-Tank Meters

3-25

S.1.3.6. Travel of Indicator. - If the most sensitive element of the primary indicating element utilizes an 

indicator and graduations, the relative movement of these parts corresponding to the smallest indicated value 

shall not be less than 5 mm (0.20 in).

S.1.4. Computing-Type Device.

S.1.4.1. Display of Unit Price. - In a device of the computing type, means shall be provided for displaying on 

the outside of the device, in a manner clear to the operator and an observer, the unit price at which the device is 

set to compute.

(Amended 1983)

S.1.4.2. Printed Ticket. - If a computing-type device issues a printed ticket which displays the total computed 

price, the ticket shall also have printed clearly thereon the total quantity of the delivery, the appropriate fraction 

of the quantity, and the price per unit of quantity.

(Amended 1989)

S.1.4.3. Money-Value Computations. - Money-value computations shall be of the full-computing type in 

which the money value at a single unit price, or at each of a series of unit prices, shall be computed for every 

delivery within either the range of measurement of the device or the range of the computing elements, whichever 

is less. Value graduations shall be supplied and shall be accurately positioned. The value of each graduated 

interval shall be 1 cent. On electronic devices with digital indications, the total price may be computed on the 

basis of the quantity indicated when the value of the smallest division indicated is equal to or less than 0.2 L 

(0.1 gal) or 0.2 kg (1 lb).

(Amended 1979, 1989)

S.1.4.4. Money Values, Mathematical Agreement. - Any digital money-value indication and any recorded 

money value on a computing-type device shall be in mathematical agreement with its associated quantity 

indication or representation to within 1 cent of money value.

S.2. Design of Measuring Elements.

S.2.1. Vapor Elimination. - A metering system shall be equipped with an effective vapor or air eliminator or other 

automatic means to prevent the passage of vapor and air through the meter. Vent lines from the air or vapor 

eliminator shall be made of metal tubing or some other suitable rigid material.

(Amended 1993)

S.2.2. Provision for Sealing. - Except on devices for metering milk, adequate provision shall be made for applying 

security seals in such a manner that no adjustment may be made of:

(a) any measurement element, and

(b) any adjustable element for controlling delivery rate when such rate tends to affect the accuracy of deliveries.

S.2.2.1. Milk-Metering Systems. - Adequate provision shall be made for applying security seals to the 

adjustment mechanism and the register. The adjusting mechanism shall be readily accessible for purposes of 

affixing a security seal.

S.2.3. Directional Flow Valves. - Valves intended to prevent reversal of flow shall be automatic in operation. 

However, on equipment used exclusively for fueling aircraft, such valves may be manual in operation.

S.3. Design of Discharge Lines and Discharge Line Valves.

(Not applicable to milk-metering systems.)

S.3.1. Diversion of Measured Liquid. – Except on equipment used exclusively for fueling aircraft, no means shall 

be provided by which any measured liquid can be diverted from the measuring chamber of the meter or the discharge 

line therefrom. However, two or more delivery outlets may be installed if means is provided to insure that:

(a) liquid can flow from only one such outlet at one time, and
3.31. Vehicle-Tank Meters

3-26

(b) the direction of flow for which the mechanism may be set at any time is definitely and conspicuously 

indicated.

S.3.2. Pump-Discharge Unit. – On a pump-discharge unit, the discharge hose shall be of the wet-hose type with a 

shutoff valve at its outlet end. However, a pump-discharge unit may be equipped also with a dry hose without a 

shutoff valve at its outlet end, but only if:

(a) the dry hose is as short as practicable, and

(b) there is incorporated in the discharge piping, immediately adjacent to the meter, effective means to insure 

that liquid can flow through only one of the discharge hoses at any one time and that the meter and the wet 

hose remain full of liquid at all times.

S.3.3. Gravity-Discharge Unit. – On a gravity-discharge unit, the discharge hose or equivalent pipe shall be of the 

dry-hose type with no shutoff valve at its outlet end. The dry hose shall be of such stiffness and only of such length 

as to facilitate its drainage. The inlet end of the hose or of an equivalent outlet pipe shall be of such height as to provide for proper drainage of the hose or pipe. There shall be incorporated an automatic vacuum breaker or equivalent 

means to prevent siphoning and to insure the rapid and complete drainage.

S.3.4. Discharge Hose. – A discharge hose shall be adequately reinforced.

S.3.5. Discharge Valve. – A discharge valve may be installed in the discharge line only if the device is of the wethose type, in which case such valve shall be at the discharge end of the line. Any other shutoff valve on the discharge 

side of the meter shall be of the automatic or semiautomatic predetermined-stop type or shall be operable only:

(a) by means of a tool (but not a pin) entirely separate from the device, or

(b) by mutilation of a security seal with which the valve is sealed open.

S.3.6. Antidrain Valve. – In a wet-hose, pressure-type device, an effective antidrain valve shall be incorporated in 

the discharge valve or immediately adjacent thereto. The antidrain valve shall function so as to prevent the drainage 

of the discharge hose. However, a device used exclusively for fueling and defueling aircraft may be of the pressure 

type without an antidrain valve.

S.4. Design of Intake Lines (for Milk-Metering Systems).

S.4.1. Diversion of Liquid to be Measured. – No means shall be provided by which any liquid can be diverted 

from the supply tank to the receiving tank without being measured by the device.

S.4.2. Intake Hose. – The intake hose shall be:

(a) of the dry-hose type;

(b) adequately reinforced;

(c) not more than 6 m (20 ft) in length, unless it can be demonstrated that a longer hose is essential to permit 

pickups from a supply tank; and

(d) connected to the pump at horizontal or above, to permit complete drainage of the hose.

S.5. Marking Requirements

S.5.1. Limitation of Use. – If a meter is intended to measure accurately only liquids having particular properties, or 

to measure accurately only under specific installation or operating conditions, or to measure accurately only when 

used in conjunction with specific accessory equipment, these limitations shall be clearly and permanently stated on 

the meter.
3.31. Vehicle-Tank Meters

3-27

S.5.2. Discharge Rates. – A meter shall be marked to show its designed maximum and minimum discharge rates. 

However, the minimum discharge rate shall not exceed 20 percent of the maximum discharge rate.

S.5.3. Measuring Components Milk-Metering System. – All components that affect the measurement of milk that 

are disassembled for cleaning purposes shall be clearly and permanently identified with a common serial number.

S.5.4. Flood Volume, Milk-Metering System. – When applicable, the volume of product necessary to flood the 

system when dry shall be clearly, conspicuously, and permanently marked on the air eliminator.

S.5.5. Conversion Factor. – When the conversion factor of 1.03 kg/L (8.6 lb/gal) is used to convert the volume of 

milk to weight, the conversion factor shall be clearly marked on the primary indicating element and recorded on the 

delivery ticket.

(Added 1989)

N. Notes

N.1. Test Liquid.

(a) A measuring system shall be tested with the liquid to be commercially measured or with a liquid of the same 

general physical characteristics. Following a satisfactory examination, the weights and measures official should 

attach a seal or tag indicating the product used during the test.

(Amended 1975)

(b) A milk measuring system shall be tested with the type of milk to be measured when the accuracy of the system is 

affected by the characteristics of milk (e.g., positive displacement meters).

(Part (b) added 1989)

N.2. Evaporation and Volume Change. - Care shall be exercised to reduce to a minimum, evaporation losses and 

volume changes resulting from changes in temperature of the test liquid.

N.3. Test Drafts. - Test drafts should be equal to at least the amount delivered by the device in 1 minute at its maximum 

discharge rate, and shall in no case be less than 180 L (50 gal) or 225 kg (500 lb).

(Amended 1989)

N.4. Testing Procedures

N.4.1. Normal Tests. - The "normal" test of a measuring system shall be made at the maximum discharge rate that 

may be anticipated under the conditions of the installation. Any additional tests conducted at flow rates down to and 

including one-half of the sum of the maximum discharge flow rate and the rated minimum discharge flow rate shall 

be considered normal tests.

(Amended 1992)

N.4.1.1. Milk Measuring System. - The "normal" test shall include a determination of the effectiveness of the 

air elimination system.

N.4.1.2. Repeatability Tests. - Tests for repeatability should include a minimum of three consecutive test 

drafts of approximately the same size and be conducted under controlled conditions where variations in factors 

such as, temperature pressure and flow rate are reduced to the extent that they will not affect the results obtained.

(Added 2001)

N.4.2. Special Tests (Except Milk-Measuring Systems). - "Special" tests shall be made to develop the operating 

characteristics of a measuring system and any special elements and accessories attached to or associated with the 

device. Any test except as set forth in N.4.1. shall be considered a special test. Special test of a measuring system 

shall be made as follows:

(a) at a minimum discharge rate of 20 percent of the marked maximum discharge rate or at the minimum 

discharge rate marked on the device whichever is less;
3.31. Vehicle-Tank Meters

3-28

(b) to develop operating characteristics of the measuring system during a split-compartment delivery.

(Amended 1978)

N.4.3. Antidrain Valve Test. - The effectiveness of the antidrain valve shall be tested after the pump pressure in the 

measuring system has been released and a valve between the supply tank and the discharge valve is closed.

N.4.4. System Capacity. - The test of a milk-measuring system shall include the verification of the volume of 

product necessary to flood the system as marked on the air eliminator.

T. Tolerances

T.1. Application.

T.1.1. To Underregistration and to Overregistration. - The tolerances hereinafter prescribed shall be applied to 

errors of underregistration and errors of overregistration.

T.2. Tolerance Values. – Maintenance, acceptance, and special test tolerances shall be as shown in Tables 1 and 2.

(Amended 1995 and 2002)

T.3. Repeatability. - When multiple tests are conducted at approximately the same flow rate and draft size, the range of 

the test results for the flow rate shall not exceed 40 percent absolute value of the maintenance tolerance and the results of 

each test shall be within the applicable tolerance. See also N.4.1.2.

(Added 1992) (Amended 2001 and 2002)

Tolerances, Table 1. Accuracy Classes for Vehicle-Tank Meters

Accuracy 

Class

Application Acceptance 

Tolerance

Maintenance 

Tolerance

Special Test 

Tolerance

0.3

Petroleum products including large capacity motor fuel 

devices (flow rates over 115 L/min (30 gpm))**, heated 

products at or greater than 50 °C asphalt at or below 

temperatures 50 °C, all other liquids not shown where 

the typical delivery is over 200 L (50 gal)

0.15 % 0.3 % 0.45 %

0.3A Asphalt at temperatures greater than 50 °C 0.3 % 0.3 % 0.5 %

0.5*

Petroleum products delivered from small capacity (at 4 

L/min (1 gpm) through 115 L/min (30 gpm))** motorfuel devices, agri-chemical liquids, and all other 

applications not shown.

0.3 % 0.5 % 0.5 %

1.1

Petroleum products and other normal liquids from 

devices with flow rates** less than 1 gpm and devices 

designed to deliver less than one gallon.

0.75 % 1.0 % 1.25 %

1.5 Water

Overregistration 1.5 % 1.5 % 1.5 %

Underregistration 1.5 % 1.5 % 5.0 %

*The maintenance tolerances on normal and special tests for 5-gallon and 10-gallon test drafts are 6 cubic inches and 11 

cubic inches, respectively. Acceptance tolerances on normal and special tests are 3 cubic inches and 5.5 cubic inches. 

** Flow rate refers to designed or marked maximum flow rate.

(Added 2002)
3.31. Vehicle-Tank Meters

3-29

Table 2. Tolerances for

Vehicle-Mounted Milk Meters

Indication Maintenance Acceptance

gallons gallons gallons

100 0.5 0.3

200 0.7 0.4

300 0.9 0.5

400 1.1 0.6

500 1.3 0.7

Over 500 Add 0.002 gallon per indicated gallon 

over 500

Add 0.001 gallon per indicated gallon 

over 500

(Added 1989)

UR. User Requirements

UR.1. Installation Requirements.

UR.1.1. Discharge Rate. - A meter shall be so installed that the actual maximum discharge rate will not exceed the 

rated maximum discharge rate. If necessary, means for flow regulation shall be incorporated in the installation, in 

which case this shall be fully effective and automatic in operation.

UR.1.2. Unit Price. - There shall be displayed on the face of a device of the computing type the unit price at which 

the device is set to compute.

UR.1.3. Intake Hose. - The intake hose in a milk-metering system shall be installed to permit complete drainage and 

ensure that all available product is measured following each pickup.

UR.2. Use Requirements.

UR.2.1. Return of Indicating and Recording Elements to Zero. - The primary indicating elements (visual), and 

the primary recording elements, when these are returnable to zero, shall be returned to zero immediately before each 

delivery is begun and after the pump has been activated and the product to be measured has been supplied to the 

measuring system.

(Amended 1981)

UR.2.2. Ticket Printer; Customer Ticket. - Vehicle-mounted metering systems shall be equipped with a ticket 

printer which shall be used for all sales where product is delivered through the meter. A copy of the ticket issued by 

the device shall be left with the customer at the time of delivery or as otherwise specified by the customer.

(Added 1993) (Amended 1994)

UR.2.2.1. Exceptions for the Sale of Aviation Fuel. - The provisions of UR.2.2. Ticket Printer; Customer 

Ticket shall not apply to vehicle-mounted metering systems used solely for the sale of aviation fuel into aircraft 

and for aircraft-related operations.

(Added 1999)
3.31. Vehicle-Tank Meters

3-30

UR.2.3. Ticket in Printing Device. - A ticket shall not be inserted into a device equipped with a ticket printer until 

immediately before a delivery is begun, and in no case shall a ticket be in the device when the vehicle is in motion 

while on a public street, highway, or thoroughfare.

UR.2.4. Credit for Flood Volume. - The volume of product necessary to flood the system as marked on the air 

eliminator shall be individually recorded on the pickup ticket of each seller affected.
3.32. LPG and Anhydrous Ammonia Liquid-Measuring Devices

3-31

Sec. 3.32. Liquefied Petroleum Gas and Anhydrous Ammonia

Liquid-Measuring Devices1

A. Application.

A.1. - This code applies to devices used for the measurement of liquefied petroleum gas and anhydrous ammonia in the 

liquid state, whether such devices are installed in a permanent location or mounted on a vehicle.

A.2. - Insofar as they are clearly appropriate, the requirements and provisions of the code may be applied to devices used 

for the measurement of other liquids that do not remain in a liquid state at atmospheric pressures and temperatures.

A.3. - See also Sec. 1.10; General Code requirements.

A.4. - This code does not apply to mass flow meters (see Sec. 3.37. Code for Mass Flow Meters)

(Added 1994)

S. Specifications

S.1. Design of Indicating and Recording Elements and of Recorded Representations.

S.1.1. Primary Elements

S.1.1.1. General. - A device shall be equipped with a primary indicating element and may also be equipped 

with a primary recording element.

[Note: Vehicle-mounted metering systems shall be equipped with a primary recording element as required by 

paragraph UR.2.6.]

S.1.1.2. Units. - A device shall indicate, and record if the device is equipped to record, its deliveries in terms of 

gallons, quarts, pints, or binary-submultiple or decimal subdivisions of the gallon.

(Amended 1987)

S.1.1.3. Value of Smallest Unit. - The value of the smallest unit of indicated delivery, and recorded delivery if 

the device is equipped to record, shall not exceed the equivalent of:

(a) 0.5 L (1 pt) on retail devices, or

(b) 5 L (1 gal) on wholesale devices.

(Amended 1987)

S.1.1.4. Advancement of Indicating and Recording Elements. - Primary indicating and recording elements 

shall be susceptible to advancement only by the mechanical operation of the device. However, a device may be 

cleared by advancing its elements to zero, but only if:

(a) the advancing movement, once started, cannot be stopped until zero is reached, or

(b) in the case of indicating elements only, such elements are automatically obscured until the elements 

reach the correct zero position.

S.1.1.5. Money Values--Mathematical Agreement. - Any digital money-value indication and any recorded 

money value on a computing-type device shall be in mathematical agreement with its associated quantity 

 1

Title amended 1986.
3.32. LPG and Anhydrous Ammonia Liquid-Measuring Devices

3-32

indication or representation to within one cent of money value; except that a stationary retail computing-type 

device must compute and indicate to the nearest 1 cent of money value (see Sec. 1.10., G-S.5.5.).

(Amended 1984, 1988)

S.1.1.6. Printed Ticket. - Any printed ticket issued by a device of the computing type on which there is printed 

the total computed price, shall have printed clearly thereon the total volume of the delivery in terms of liters or 

gallons, and the appropriate decimal fraction of the liter or gallon, and the corresponding price per liter or gallon.

(Added 1979; Amended 1987)

S.1.2. Graduations.

S.1.2.1. Length. - Graduations shall be so varied in length that they may be conveniently read.

S.1.2.2. Width. - In any series of graduations, the width of a graduation shall in no case be greater then 

the width of the minimum clear interval between graduations, and the width of main graduations shall be not 

more than 50 percent greater than the width of subordinate graduations. Graduations shall in no case be less than 

0.2 mm (0.008 in) width.

S.1.2.3. Clear Interval Between Graduations. - The clear interval shall be not less than 1.0 mm (0.04 in). If 

the graduations are not parallel, the measurement shall be made:

(a) along the line of relative movement between the graduations at the end of the indicator, or

(b) if the indicator is continuous, at the point of widest separation of the graduations.

S.1.3. Indicators.

S.1.3.1. Symmetry. - The index of an indicator shall be symmetrical with respect to the graduations, at least 

throughout that portion of its length associated with the graduations.

S.1.3.2. Length. - The index of an indicator shall reach to the finest graduations with which it is used, unless the 

indicator and the graduations are in the same plane, in which case the distance between the end of the indicator 

and the ends of the graduations, measured along the line of graduations, shall be not more than 1.0 mm (0.04 in).

S.1.3.3. Width. - The width of the index of an indicator in relation to the series of graduations with which it is 

used shall be not greater than:

(a) the width of the narrowest graduation* , and

[*Nonretroactive as of January 1, 2002]

(Amended 2001)

(b) the width of the minimum clear interval between graduations.

When the index of an indicator extends along the entire length of a graduation, that portion of the index of the 

indicator that may be brought into coincidence with the graduation shall be of the same width throughout the 

length of the index that coincides with the graduation.

S.1.3.4. Clearance. - The clearance between the index of an indicator and the graduations shall in no case be 

more than 1.5 mm (0.06 in).

S.1.3.5. Parallax. - Parallax effects shall be reduced to the practicable minimum.

S.1.4. For Retail Devices Only.

S.1.4.1. Indication of Delivery. - A retail device shall be constructed to show automatically its initial zero 

condition and the amounts delivered up to the nominal capacity of the device.
3.32. LPG and Anhydrous Ammonia Liquid-Measuring Devices

3-33

S.1.4.2. Return to Zero.

(a) Primary indicating elements shall be readily returnable to a definite zero indication.

(b) Primary recording elements on a stationary retail device shall be readily returnable to a definite zero 

indication if the device is equipped to record.

(c) Means shall be provided to prevent the return of primary indicating elements, and of primary recording 

elements if these are returnable to zero, beyond their correct zero position.

(Amended 1990)

S.1.5. For Stationary Retail Devices Only.

S.1.5.1. Display of Unit Price and Product Identity. - In a device of the computing type, means shall be 

provided for displaying on each face of the device the unit price at which the device is set to compute or to 

deliver as the case may be, and there shall be conspicuously displayed on each side of the device the identity of 

the product that is being dispensed. If a device is so designed as to dispense more than one grade, brand, blend, 

or mixture of product, the identity of the grade, brand, blend, or mixture being dispensed shall also be displayed 

on each face of the device.

S.1.5.2. Money-Value Computations. - A computing device shall compute the total sales price at any singlepurchase unit price (excluding fleet sales and other price contract sales) for which the product is offered for sale 

at any delivery possible within either the measurement range of the device or the range of the computing 

elements, whichever is less. The analog money value indication shall not differ from the mathematically

computed money value (quantity x unit price = sales price), for any delivered quantity, by an amount greater 

than the values shown in Table 1.

(Amended 1995)

Table 1.

Money-Value Divisions and

Maximum Allowable Variations for Money-Value

Computations on Mechanical Analog Computers

Unit Price Money 

Value

Division

Maximum

Allowable Variation

From To and including Design

Test

Field

Test

0 $0.25/liter or

$1.00/gallon 1¢ ± 1¢ ± 1¢

$0.25/liter or

$1.00/gallon

$0.75/liter or

$3.00/gallon 1¢ or 2¢ ± 1¢ ± 2¢

$0.75/liter or

$3.00/gallon

$2.50/liter or

$10.00/gallon 1¢ or 2¢ ± 1¢ ± 2¢

$0.75/liter or

$3.00/gallon

$2.50/liter or

$10.00/gallon 5¢ ± 2 1/2¢ ± 5¢

S.1.5.2.1. Money-Value Divisions, Analog. - The value of the graduated intervals representing money 

values on a computing-type device with analog indications shall be as follows:

(a) Not more than 1 cent at all unit prices up to and including $0.25 per liter or $1.00 per gallon.

(b) Not more than 2 cents at unit prices greater than $0.25 per liter or $1.00 per gallon up to and 

including $0.75 per liter or $3.00 per gallon.
3.32. LPG and Anhydrous Ammonia Liquid-Measuring Devices

3-34

(c) Not more than 5 cents at all unit prices greater than $0.75 per liter or $3.00 per gallon.

(Amended 1984)

S.1.5.2.2. Money-Value Divisions, Digital. - A computing-type device with digital indications shall 

comply with the requirements of paragraph G.-S.5.5., Money Values, Mathematical Agreement, and the 

total price computation shall be based on quantities not exceeding 0.01-gallon intervals for devices 

indicating in inch-pound units and 0.05 liter for devices indicating in metric units.

S.1.5.2.3. Money-Value Divisions, Auxiliary Indications. In a system equipped with auxiliary indications, 

all indicated money-value divisions shall be identical.

[Nonretroactive as of January 1, 1985.]

S.1.6. For Wholesale Devices Only.

S.1.6.1. Travel of Indicator. - A wholesale device shall be readily operable to deliver accurately any quantity 

from 180 L (50 gal) to the capacity of the device. If the most sensitive element of the indicating system uses an 

indicator and graduations, the relative movement of these parts corresponding to a delivery of 5 L (1 gal) shall be 

not less than 5 mm (0.20 in).

(Amended 1987)

S.2. Design of Measuring Elements.

S.2.1. Vapor Elimination. - A device shall be equipped with an effective vapor eliminator or other effective means 

to prevent the passage of vapor through the meter.

S.2.2. Provision for Sealing. - Adequate provision shall be made for applying security seals in such a manner that 

no adjustment may be made of:

(a) any measurement element, and

(b) any adjustable element for controlling delivery rate, when such rate tends to affect the accuracy of 

deliveries.

The adjusting mechanism shall be readily accessible for purposes of affixing a security seal.

S.2.3. Directional Flow Valves. - A measuring system shall be equipped with a valve or other effective means, 

automatic in operation and installed in or adjacent to the measuring element, to prevent reversal of flow of the 

product being measured.

(Amended 1982).

S.2.4. Maintenance of Liquid State. - A device shall be so designed and installed that the product being measured 

will remain in a liquid state during the passage through the meter.

S.2.5. Thermometer Well. - For test purposes, means shall be provided to determine the temperature of the liquid 

either:

(a) in the liquid chamber of the meter, or

(b) in the meter inlet or discharge line and immediately adjacent to the meter.

(Amended 1987)

S.2.6. Automatic Temperature Compensation. - A device may be equipped with an adjustable automatic means 

for adjusting the indication and registration of the measured volume of product to the volume at 15 C (60 F).
3.32. LPG and Anhydrous Ammonia Liquid-Measuring Devices

3-35

S.2.6.1. Provision for Deactivating. - On a device equipped with an automatic temperature compensating 

mechanism that will indicate or record only in terms of liters compensated to 15 C or gallons to 60 F, 

provision shall be made to facilitate the deactivation of the automatic temperature compensating mechanism so 

that the meter may indicate, and record if it is equipped to record, in terms of the uncompensated volume. 

(Amended 1972)

S.2.6.2. Provision for Sealing. - Provision shall be made for applying security seals in such a manner that an 

automatic temperature-compensating system cannot be disconnected and that no adjustment may be made to the 

system.

S.3. Design of Discharge Lines and Discharge Line Valves.

S.3.1. Diversion of Measured Liquid. - No means shall be provided by which any measured liquid can be diverted 

from the measuring chamber of the meter or the discharge line therefrom. However, two or more delivery outlets 

may be permanently installed if means are provided to insure that:

(a) liquid can flow from only one such outlet at one time, and

(b) the direction of flow for which the mechanism may be set at any time is definitely and conspicuously 

indicated.

In addition, a manually controlled outlet that may be opened for the purpose of emptying a portion of the system to 

allow for repair and maintenance operations shall be permitted. Effective means shall be provided to prevent the 

passage of liquid through any such outlet during normal operation of the device and to indicate clearly and 

unmistakably when the valve controls are so set as to permit passage of liquid through such outlet.

(Amended 1975).

S.3.2. Delivery Hose. - The delivery hose of a retail device shall be of the wet-hose type with a shutoff valve at its 

outlet end.

S.4. Marking Requirements.

S.4.1. Limitation of Use. - If a device is intended to measure accurately only products having particular properties, 

or to measure accurately only under specific installation or operating conditions, or to measure accurately only when 

used in conjunction with specific accessory equipment, these limitations shall be clearly and permanently stated on 

the device.

S.4.2. Discharge Rates. - A device shall be marked to show its designed maximum and minimum discharge rates. 

The marked minimum discharge rate shall not exceed:

(a) 20 L (5 gal) per minute for stationary retail devices, or

(b) 20 percent of the marked maximum discharge rate for other retail devices and for wholesale devices.

(Amended 1987)

S.4.3. Temperature Compensation. - If a device is equipped with an automatic temperature compensator, the 

primary indicating elements, recording elements, and recorded representation shall be clearly and conspicuously 

marked to show that the volume delivered has been adjusted to the volume at 15 C (60 F).

N. Notes

N.1. Test Liquid. - A device shall be tested with the liquid to be commercially measured or with a liquid of the same 

general physical characteristics.

N.2. Vaporization and Volume Change. - Care shall be exercised to reduce to a minimum, vaporization and volume 

changes.
3.32. LPG and Anhydrous Ammonia Liquid-Measuring Devices

3-36

N.3. Test Drafts. - Test drafts should be equal to at least the amount delivered by the device in 1 minute at its normal 

discharge rate.

(Amended 1982)

N.4. Testing Procedures.

N.4.1. Normal Tests. - The "normal" test of a device shall be made at the maximum discharge flow rate developed 

under the conditions of the installation. Any additional tests conducted at flow rates down to and including one-half 

the sum of the maximum discharge flow rate and the rated minimum discharge flow rate shall be considered normal 

tests.

(Amended 1998)

N.4.1.1. Automatic Temperature Compensation. - On devices equipped with automatic temperature 

compensating systems, normal tests shall be conducted as follows:

(a) by comparing the compensated volume indicated or recorded to the actual delivered volume corrected 

to 15 C (60 F); and,

(b) with the temperature compensating system deactivated, comparing the uncompensated volume 

indicated or recorded to the actual delivered volume.

The first test shall be performed with the automatic temperature-compensating system operating in the "as 

found" condition. On devices that indicate or record both the compensated and uncompensated volume for each 

delivery, the tests in (a) and (b) may be performed as a single test.

(Amended 1987)

N.4.1.2. Repeatability Tests. - Tests for repeatability should include a minimum of three consecutive test drafts 

of approximately the same size and be conducted under controlled conditions where variations in factors such as, 

temperature pressure and flow rate are reduced to the extent that they will not affect the results obtained.

(Added 2001)

N.4.2. Special Tests. - "Special" tests, to develop the operating characteristics of a device and any special elements 

and accessories attached to or associated with the device, shall be made as circumstances require. Any test except as 

set forth in N.4.1. shall be considered a special test.

N.4.2.1. For Motor-Fuel Devices. - A motor-fuel device shall be so tested at a minimum discharge rate of:

(a) 20 L (5 gal) per minute, or

(b) the minimum discharge rate marked on the device, whichever is less.

N.4.2.2. For Other Retail Devices. - A retail device other than a motor-fuel device shall be tested at a 

minimum discharge rate of:

(a) the minimum discharge rate that can be developed under the conditions of installation, or

(b) the minimum discharge rate marked on the device, whichever is greater.

(Amended 1973)

N.4.2.3. For Wholesale Devices. - A wholesale device shall be so tested at a minimum discharge rate of:

(a) 40 L (10 gal) per minute for a device with a rated maximum discharge less than 180 L (50 gal) per 

minute.

(b) 20 percent of the marked maximum discharge rate for a device with a rated maximum discharge of 

180 L (50 gal) per minute or more, or
3.32. LPG and Anhydrous Ammonia Liquid-Measuring Devices

3-37

(c) the minimum discharge rate marked on the device, whichever is least.

(Amended 1987)

N.4.3. Money-Value Computation Tests.

N.4.3.1. Laboratory Design Evaluation Tests. - In the conduct of laboratory design evaluation tests, 

compliance with paragraph S.1.5.2. shall be determined by using the cone gear as a reference for the total 

quantity delivered. The indicated delivered quantity shall agree with the cone gear representation with the index 

of the indicator within the width of the graduation. The maximum allowable variation of the indicated sales 

price shall be as shown in Table 1.

N.4.3.2. Field Tests. - In the conduct of field tests to determine compliance with paragraph S.1.5.2. the 

maximum allowable variation in the indicated sales price shall be as shown in Table 1.

(Added 1984)

N.5. Temperature Correction. - Corrections shall be made for any changes in volume resulting from the differences in 

liquid temperatures between time of passage through the meter and time of volumetric determination in the test measure.

T. Tolerances

T.1. Application.

T.1.1. To Underregistration and to Overregistration. - The tolerances hereinafter prescribed shall be applied to 

errors of underregistration and errors of overregistration, whether or not a device is equipped with an automatic 

temperature compensator.

T.2. Tolerance Values. - The maintenance and acceptance tolerances for normal and special tests shall be:

Acceptance 

Tolerance

Maintenance 

Tolerance

Normal Tests 0.6% 1.0%

Special Tests 1.0% 1.0%

(Amended 1988 and 1992)

T.3. Repeatability. -When multiple tests are conducted at approximately the same flow rate and draft size, the range of 

the test results for the flow rate shall not exceed 40 percent of the absolute value of the maintenance tolerance and the 

results of each test shall be within applicable tolerance. This tolerance does not apply to the test of the automatic 

temperature compensating system. See also N.4.1.2.

(Added 1992) (Amended 1997 and 2001) 

T.4. Automatic Temperature Compensating Systems. - The difference between the meter error (expressed as a 

percentage) for results determined with and without the automatic temperature compensating system activated shall not 

exceed:

(a) 1.0 percent for mechanical automatic temperature compensating systems; and

(b) 0.5 percent for electronic automatic temperature compensating systems.

The delivered quantities for each test shall be approximately the same size. The results of each test shall be within the 

applicable acceptance or maintenance tolerance.

(Added 1991)(Amended 1992, 1996, and 1997)
3.32. LPG and Anhydrous Ammonia Liquid-Measuring Devices

3-38

UR. User Requirements

UR.1. Installation Requirements.

UR.1.1. Discharge Rate. - A device shall be so installed that the actual maximum discharge rate will not exceed the 

rated maximum discharge rate. If necessary, means for flow regulation shall be incorporated in the installation, in 

which case this shall be fully effective and automatic in operation.

UR.1.2. Length of Discharge Hose. - The length of the discharge hose on a stationary motor-fuel device shall not 

exceed 5.5 m (18 ft), measured from the outside of the housing of the device to the inlet end of the discharge nozzle, 

unless it can be demonstrated that a longer hose is essential to permit deliveries to be made to receiving vehicles or 

vessels. Unnecessarily remote location of a device shall not be accepted as justification for an abnormally long hose.

(Amended 1991)

UR.2. Use Requirements.

UR.2.1. Return of Indication and Recording Elements to Zero. - The primary indicating elements (visual), and 

the primary recording elements when these are returnable to zero, shall be returned to zero before each delivery.

UR.2.2. Condition of Fill of Discharge Hose. - The discharge hose shall be completely filled with liquid before the 

"zero" condition is established prior to the start of a commercial delivery, whether this condition is established by 

resetting the primary indicating elements to zero indication or by recording the indications of the primary indicating 

elements. (Also see UR.2.1.)

UR.2.3. Vapor-Return Line. - During any metered delivery of liquefied petroleum gas from a supplier's tank to a 

receiving container, there shall be no vapor-return line from the receiving container to the supplier's tank:

(a) in the case of any receiving container to which normal deliveries can be made without the use of such vaporreturn line, or

(b) in the case of any new receiving container when the ambient temperature is below 90 F.

UR.2.4. Temperature Compensation.

UR.2.4.1. Use of Automatic Temperature Compensators. - If a device is equipped with an automatic 

temperature compensator, this shall be connected, operable, and in use at all times. Such automatic temperature 

compensator may not be removed, nor may a compensated device be replaced with an uncompensated device, 

without the written approval of the weights and measures authority having jurisdiction over the device.

UR.2.4.2. Temperature Compensated Sale. - All sales of liquefied petroleum gas in a liquid state, when the 

quantity is determined by an approved measuring system equipped with a temperature compensating mechanism, 

or by weight and converted to liters or gallons, or by a calibrated container, shall be in terms of liters at 15 C or 

the United States gallon of 231 in3 at 60 F.

(Added 1984)

UR.2.4.3. Invoices. - Any invoice based on a reading of a device that is equipped with an automatic temperature 

compensator or based on a weight converted to gallons, or based on the volume of a calibrated container, shall 

have shown thereon that the volume delivered has been adjusted to the volume at 15 C (60 F).

(Amended 1984)

UR.2.4.4. Automated Temperature-Compensating Systems. - Means for determining the temperature of 

measured liquid in an automatic temperature-compensating system shall be so designed and located that, in any 

"usual and customary" use of the system,the resulting indications and/or recorded representations are within 

applicable tolerances.

(Added 1987)
3.32. LPG and Anhydrous Ammonia Liquid-Measuring Devices

3-39

UR.2.5. Ticket in Printing Device. - A ticket shall not be inserted into a device equipped with a ticket printer until 

immediately before a delivery is begun, and in no case shall a ticket be in the device when the vehicle is in motion 

while on a public street, highway, or thoroughfare.

UR.2.6. Ticket Printer; Customer Ticket. - Vehicle-mounted metering systems shall be equipped with a ticket 

printer. The ticket printer shall be used for all sales; a copy of the ticket issued by the device shall be left with the 

customer at the time of delivery.

(Added 1992)
3.32. LPG and Anhydrous Ammonia Liquid-Measuring Devices

3-40
3.33. Hydrocarbon Gas Vapor-Measuring Devices

3-41

Sec. 3.33. Hydrocarbon Gas Vapor-Measuring Devices1

A. Application

A.1. - This code applies to devices used for the measurement of hydrocarbon gas in the vapor state, such as propane, 

propylene, butanes, butylenes, ethane, methane, natural gas and any other hydrocarbon gas/air mix.

(Amended 1984, 1986, 1988, 1991)

A.2. - This code does not apply to:

(a) Liquid-measuring devices used for dispensing liquefied petroleum gases in liquid form (for which see Sec. 3.32; 

Code for Liquefied Petroleum Gas and Anhydrous Ammonia Liquid-Measuring Devices).

(b) Natural, liquefied petroleum, and manufactured-gas-vapor meters when these are operated in a public utility 

system.

(c) Mass flow meters (see Sec. 3.37. Code for Mass Flow Meters)

(Added 1994)

A.3. - See also Sec. 1.10; General Code requirements.

S. Specifications

S.1. Design of Indicating and Recording Elements and of Recorded Representations.

S.1.1. Primary Elements.

S.1.1.1. General. - A device shall be equipped with a primary indicating element and may also be equipped 

with a primary recording element.

S.1.1.2. Units. - A volume-measuring device shall indicate, and record if equipped to record, its deliveries in 

terms of cubic meters or cubic feet, or multiple or decimal subdivisions of cubic meters or cubic feet.

(Amended 1972, 1991)

S.1.1.3. Value of Smallest Unit. - Volume-Measuring Devices: The value of the smallest unit of indicated 

delivery, and recorded delivery if the device is equipped to record, shall not exceed:

(a) 1 m3 (1000 dm3

) (100 ft3) when the maximum rated gas capacity is less than 100 m3/h (10 000 ft3/h);

(b) 10 m3 (1000 ft3

) when the maximum rated gas capacity is 280 m3/h (10 000 ft3/h) up to but not 

including 1700 m3

/h (60 000 ft 3/h);

(c) 100 m3 (10 000 ft3

) when the maximum rated gas capacity is 1700 m3/h (60 000 ft3/h) or more.

(Amended 1972, 1988, 1991)

S.1.1.4. Advancement of Indicating and Recording Elements. - Primary indicating and recording elements 

shall advance digitally or continuously and be susceptible to advancement only by the mechanical operation of 

the device.

S.1.1.5. Proving Indicator. - Devices rated less than 280 m3

/h (10 000 ft3/h) gas capacity shall be equipped 

with a proving indicator measuring 0.025, 0.05, 0.1, 0.2, or 0.25 m3 per revolution, (1, 2, 5, or 10 ft 3 per 

revolution) for testing the meter. Devices with larger capacities shall be equipped as follows:

 1

Title changed 1986.
3.33. Hydrocarbon Gas Vapor-Measuring Devices

3-42

(a) Devices rated 280 m3 (10 000 ft3

) up to but not including 1700 m3/h (60 000 ft3/h) gas capacity shall be 

equipped with a proving indicator measuring not greater than 1 m3 (100 ft3

) per revolution.

(b) Devices rated 1700 m3

/h (60 000 ft3/h) gas capacity or more shall be equipped with a proving indicator 

measuring not more than 10 m3 (1000 ft3

) per revolution.

The test circle of the proving indicator shall be divided into 10 equal parts. Additional subdivisions of one or 

more of such equal parts may be made.

(Amended 1973 and 1988)

S.1.2. Graduations.

S.1.2.1. Length. - Graduations shall be so varied in length that they may be conveniently read.

S.1.2.2. Width. - In any series of graduations, the width of a graduation shall in no case be greater than the 

width of the minimum clear interval between graduations, and in no case should it exceed 1.0 mm (0.04 in) for 

indicating elements and 0.5 mm (0.02 in) for proving circles.

S.1.2.3. Clear Interval Between Graduations. - The clear interval shall be not less than 1.0 mm (0.04 in). If 

the graduations are not parallel, the measurement shall be made:

(a) along the line of relative movement between the graduations at the end of the indicator, or

(b) if the indicator is continuous, at the point of widest separation of the graduations.

S.1.3. Indicators.

S.1.3.1. Symmetry. - The index of an indicator shall be symmetrical with respect to the graduations, at least 

throughout that portion of its length associated with the graduations.

S.1.3.2. Length. - The index of an indicator shall reach to the finest graduations with which it is used.

S.1.3.3. Width. - The width of the index of an indicator in relation to the series of graduations with which it is 

used shall be not greater than:

(a) the width of the narrowest graduation* , and

[*Nonretroactive as of January 1, 2002]

(Amended 2001)

(b) the width of the minimum clear interval between graduations.

When the index of an indicator extends along the entire length of a graduation, that portion of the index of the 

indicator that may be brought into coincidence with the graduation shall be of the same width throughout the 

length of the index that coincides with the graduation.

S.1.3.4. Clearance. - The clearance between the index of an indicator and the graduations shall in no case be 

more than 1.5 mm (0.06 in).

S.1.3.5. Parallax. - Parallax effects shall be reduced to the practicable minimum.

S.2. Design of Measuring Elements.

S.2.1. Pressure Regulation. - Except when measured as a retail motor fuel, the vapor should be measured at a 

normal gauge pressure (psig) of:

(Amended 1991)

(a) 2740 Pa ± 685 Pa (11 in of water column (0.40 psig) ± 2.75 in of water column (0.10 psig)) for liquefied 

petroleum gas vapor; or
3.33. Hydrocarbon Gas Vapor-Measuring Devices

3-43

(b) 1744 Pa ± 436 Pa (7 in of water column (0.25 psig) ± 1.75 in of water column (0.06 psig)) for natural and 

manufactured gas.

When vapor is measured at a pressure other than what is specified above for the specific product, a volume multiplier 

shall be applied within the meter or to the billing invoice based on the following equation:

AAP NGP

AAP GP VPM +

+ = , where

VPM = Volume pressure multiplier

AAP = Assumed atmospheric pressure in psia

GP = Gauge pressure in pascal or psig

NGP = Normal gauge pressure in pascal or psig

The assumed atmospheric pressure is to be taken from Tables 2 and 2M.

When liquefied petroleum gas vapor is measured at a pressure of 6900 Pa (1 psig) or more, the delivery pressure shall 

be maintained within ±1725 Pa (±0.25 psig).

Pressure variations due to regulator lock off shall not increase the operating pressure by more than 25 percent.

(Amended 1980, 1984, 1991)

S.2.2. Provision for Sealing. - Adequate provision shall be made for applying security seals in such a manner that 

no adjustment may be made of any measurement element.

S.2.3. Maintenance of Vapor State. - A device shall be so designed and installed that the product being measured 

will remain in a vapor state during passage through the meter.

S.2.4. Automatic Temperature Compensation. - A device may be equipped with an adjustable automatic means 

for adjusting the indication and registration of the measured volume of vapor product to the volume at 15 C (60 F).

S.3. Design of Discharge Lines

S.3.1. Diversion of Measured Vapor. - No means shall be provided by which any measured vapor can be diverted 

from the measuring chamber of the meter or the discharge line therefrom.

S.4. Marking Requirements.

S.4.1. Limitations of Use. - If a device is intended to measure accurately only products having particular properties, 

or to measure accurately only under specific installation or operating conditions, or to measure accurately only when 

used in conjunction with specific accessory equipment, these limitations shall be clearly and permanently stated on 

the device.

S.4.2. Discharge Rates. - A volume-measuring device shall be marked to show its rated gas capacity in cubic meters 

per hour or cubic feet per hour.

S.4.3. Temperature Compensation. - If a device is equipped with an automatic temperature compensator, this shall 

be indicated on the badge or immediately adjacent to the badge of the device and on the register.

S.4.4. Badge. - A badge affixed in a prominent position on the front of the device shall show the manufacturer's 

name, serial number and model number of the device, and capacity rate of the device for the particular products that 

it was designed to meter as recommended by the manufacturer.
3.33. Hydrocarbon Gas Vapor-Measuring Devices

3-44

N. Notes

N.1. Test Medium. - The device shall be tested with air or the product to be measured.

(Amended 1991)

N.2. Temperature and Volume Change. - Care should be exercised to reduce to a minimum any volume changes. The 

temperature of the air, bell-prover oil, and the meters under test should be within 1 C (2 F) of one another. The devices 

should remain in the proving room for at least 16 hours before starting any proving operations to allow the device 

temperature to approximate the temperature of the proving device.

N.3. Test Drafts. - Except for low-flame tests, test drafts shall be at least equal to one complete revolution of the largest 

capacity proving indicator, and shall in no case be less than 0.05 m3 or 2 ft3

. All flow rates shall be controlled by suitable 

outlet orifices.

(Amended 1973 and 1991)

Table 1.

Capacity of Low-Flow Test Rate Orifices

With Respect to Device Capacity

Metric Units Inch-Pound Units

Rated Capacity Low-Flow Test Rate Rated Capacity Low-Flow Test Rate

Up to and including 

7 m3

/h 0.007 m3

/h Up to and including 250 

ft3

/h 0.25 ft3

/h

Over 7 m3/h up to and 

including 14 m3

/h 0.014 m3

/h Over 250 ft3

/h up to and 

including 500 ft3

/h 0.50 ft3

/h

Over 14 m3/h 0.1% of capacity rate Over 500 ft3/h 0.1% of capacity rate

N.4. Test Procedures. - If a device is equipped with an automatic temperature compensator, the proving device reading 

shall be corrected to 15 C (60 F), using an approved table.

(Amended 1972)

N.4.1. Normal Tests. - The normal test of a device shall be made at a rate not to exceed the capacity rate given on 

the badge of the meter.

(Amended 1988)

N.4.1.1. Automatic Temperature Compensation. - If a device is equipped with an automatic temperature 

compensator, the quantity of the test draft indication of the standard shall be corrected to 15 C (60 F).

N.4.1.2. Repeatability Tests. – Tests for repeatability should include a minimum of three consecutive test drafts 

of approximately the same size and be conducted under controlled conditions where variations in factors, such 

as temperature pressure, and flow rate are reduced to the extent that they will not affect the results obtained.

 (Added 2002)

N.4.2. Special Tests. - "Special" tests, to develop the operating characteristics of a device, and any special elements 

and accessories attached to or associated with the device, shall be made as circumstances require. Any test except as 

set forth in N.4.1. is a special test.

N.4.2.1. Slow Test. - The device shall be tested at a rate not less than 20 percent of the marked capacity rate, or 

(at the check rate) not less than the minimum flow rate if marked on the device, whichever is less.

(Amended 1988)

N.4.2.2. Low-Flame Test. - The device shall be tested at an extremely low-flow rate as given in Table 1. The 

test shall consist of passing air at a pressure of 375 Pa (1.5 in water column) through the meter for not less than 

60 minutes. The meter shall continue to advance at the conclusion of the test period.

(Amended 1990, 1991)
3.33. Hydrocarbon Gas Vapor-Measuring Devices

3-45

N.4.2.3. Pressure Regulation Test. - On devices operating at a pressure of 6900 Pa (1 psig) or more, a pressure 

regulation test shall be made at both the minimum and maximum use load to determine the proper operation of 

the regulator and the proper sizing of the piping and dispensing equipment. These tests may include a test of 24 

hours during which the pressure is recorded.

(Added 1984)

N.5. Temperature Correction. - Corrections shall be made for any changes in volume resulting from the difference in 

air temperatures between time of passage through the device and time of volumetric determination in the proving device.

N.6. Frequency of Test. - A hydrocarbon gas vapor-measuring device shall be tested before installation and allowed to 

remain in service for 10 years from the time last tested without being retested, unless a test is requested by:

(a) the purchaser of the product being metered,

(b) the seller of the product being metered, or

(c) the weights and measures official.

T. Tolerances

T.1. Tolerance Values on Normal Tests and on Special Tests Other Than Low-Flame Tests. - Maintenance and 

acceptance tolerances for hydrocarbon gas vapor-measuring devices shall be 3 percent (1.03 proof) of the test draft on 

underregistration and 1.5 percent (0.985 proof) of the test draft on overregistration.

(Amended 1981)

T.2. Repeatability – When multiple tests are conducted at approximately the same flow rate and draft size, the range of 

the test results for the flow rate shall not exceed 0.9 percent and the results of each test shall be within the applicable 

tolerance. See also N.4.1.2.

(Added 2002)

UR. User Requirements

UR.1. Installation Requirements.

UR.1.1. Capacity Rate. - A device shall be so installed that the actual maximum flow rate will not exceed the 

capacity rate except for short durations. If necessary, means for flow regulation shall be incorporated in the 

installation, in which case this shall be fully effective and automatic in operation.

UR.1.2. Leakage. - The metering system shall be installed and maintained as a pressure-tight and leak-free 

system.

UR.2. Use Requirements.

UR.2.1. Automatic Temperature Compensation. - A compensated device may not be replaced with an 

uncompensated device without the written approval of the weights and measures authority having jurisdiction over 

the device.

UR.2.2. Invoices. - A customer purchasing hydrocarbon gas measured by a vapor meter for other than motor fuel 

shall receive from the seller an invoice for each billing period. The invoice shall clearly and separately show the 

following:

(a) The opening and closing meter readings and the dates of those readings.

(b) The altitude correction factor.

(c) The total cubic meters (cubic feet) billed, corrected for elevation.

(d) The charge per cubic meter (cubic foot) after correction for elevation.
3.33. Hydrocarbon Gas Vapor-Measuring Devices

3-46

(e) All periodic charges independent of the measured gas, such as meter charges, meter reading fees, service 

charges or a minimum charge for a minimum number of cubic meters (cubic feet).

(f) The total charge for the billing period.

If the vapor meter is equipped with an automatic temperature compensator, or any other means are used to 

compensate for temperature, the invoice shall show that the volume has been adjusted to the volume at 15 C 

(60 F).

(Amended 1988, 1991)

UR.2.3. Correction for Elevation. - The metered volume of gas shall be corrected for changes in the atmospheric 

pressure with respect to elevation to the standard pressure of 101.56 kPa (14.73 psia). The appropriate altitude 

correction factor from Table 2M or 2 shall be used. (The table is modified from NIST Handbook 117.) 

(Amended 1988)

Elevation correction factors (ACF) were obtained by using the following equation:

base pressure

GP of gas AAP ACF + = , where

GP = gauge pressure

AAP = assumed atmospheric pressure

base pressure = 101.560 kPa = 14.73 psia

2740 Pa = 11 in of water column = 0.397 psig

1744 Pa = 7 in of water column = 0.253 psig

(Added 1988)

UR.2.4. Valves and Test Tee. - All gas meter installations shall be provided with a shut-off valve located adjacent to 

and on the inlet side of the meter. In the case of a single meter installation utilizing a liquefied petroleum gas tank, 

the tank service valve may be used in lieu of the shut-off valve. All gas meter installations shall be provided with a 

test tee located adjacent to and on the outlet side of the meter.

[Nonretroactive as of January 1, 1990.]

(Added 1989)

UR.2.5. Use of Auxiliary Heated Vaporizer Systems.-Automatic temperature compensation shall be used on 

hydrocarbon gas vapor meters equipped with an auxiliary heated vaporizer system unless there is sufficient length of 

underground piping to provide gas at a uniform temperature to the meter inlet. When required by weights and 

measures officials, a thermometer well (appropriately protected against freezing) shall be installed immediately upstream of the meter.

(Added 1990)
3.33. Hydrocarbon Gas Vapor-Measuring Devices

3-47

Table 2M. Corrections for Altitude, Metric Units

Elevation

(meters)

Altitude

Correction

Factor

Assumed

Atmospheric

Pressure

Assumed Atmospheric

Pressure Plus

Gauge Pressure

2.74 kPa

Gauge

Pressure

1.74 kPa

Gauge

Pressure

(kPa)

2.74 kPa

Gauge

Pressure

1.74 kPa

Gauge

Pressure

above

above

above

above

above

above

above

above

above

above

above

above

above

above

above

above

above

above

above

above

above

-50 to

120 to

300 to

470 to

650 to

830 to

1020 to

1210 to

1400 to

1590 to

1790 to

2000 to

2210 to

2420 to

2640 to

2860 to

3080 to

3320 to

3560 to

3800 to

4050 to

4310 to

120

300

470

650

830

1020

1210

1400

1590

1790

2000

2210

2420

2640

2860

3080

3320

3560

3800

4050

4310

4580

1.02

1.00

0.98

0.96

0.94

0.92

0.90

0.88

0.86

0.84

0.82

0.80

0.78

0.76

0.74

0.72

0.70

0.68

0.66

0.64

0.62

0.60

1.01

0.99

0.97

0.95

0.93

0.91

0.89

0.87

0.85

0.83

0.81

0.79

0.77

0.75

0.73

0.71

0.69

0.67

0.65

0.63

0.61

0.59

100.85

98.82

96.79

94.76

92.73

90.70

88.66

86.63

84.60

82.57

80.54

78.51

76.48

74.45

72.41

70.38

68.35

66.32

64.29

62.26

60.23

58.20

103.59

101.56

99.53

97.50

95.47

93.44

91.40

89.37

87.34

85.31

83.28

81.25

79.22

77.19

75.15

73.12

71.09

69.06

67.03

65.00

62.97

60.94

102.58

100.54

98.51

96.48

94.45

92.42

90.39

88.36

86.33

84.29

82.26

80.23

78.20

76.17

74.15

72.12

70.08

68.05

66.01

63.98

61.95

59.92
3.33. Hydrocarbon Gas Vapor-Measuring Devices

3-48

Table 2. Corrections for Altitude, Inch-Pound Units

Elevation

(feet)

Altitude

Correction

Factor

Assumed

Atmospheric

Pressure

Assumed Atmospheric 

Pressure Plus Gauge 

Pressure

11 inch 

WC

7 inch 

WC (psia) 11 inch WC(psia)

7 inch WC

(psia)

above

above

above

above

above

above

above

above

above

above

above

above

above

above

above

above

above

above

above

above

above

-150 to

400 to

950 to

1550 to

2100 to

2700 to

3300 to

3950 to

4550 to

5200 to

5850 to

6500 to

7200 to

7900 to

8600 to

9350 to

10 100 to

10 850 to

11 650 to

12 450 to

13 250 to

14 100 to

400

950

1550

2100

2700

3300

3950

4550

5200

5850

6500

7200

7900

8600

9350

10 100

10 850

11 650

12 450

13 250

14 100

14 950

1.02

1.00

0.98

0.96

0.94

0.92

0.90

0.88

0.86

0.84

0.82

0.80

0.78

0.76

0.74

0.72

0.70

0.68

0.66

0.64

0.62

0.60

1.01

0.99

0.97

0.95

0.93

0.91

0.89

0.87

0.85

0.83

0.81

0.79

0.77

0.75

0.73

0.71

0.69

0.67

0.65

0.63

0.61

0.59

14.64

14.35

14.05

13.76

13.46

13.17

12.87

12.58

12.28

11.99

11.69

11.40

11.10

10.81

10.51

10.22

9.92

9.63

9.33

9.04

8.75

8.45

15.04

14.74

14.45

14.15

13.86

13.56

13.27

12.97

12.68

12.38

12.09

11.79

11.50

11.20

10.91

10.61

10.32

10.03

9.73

9.44

9.14

8.85

14.89

14.60

14.30

14.01

13.71

13.42

13.12

12.83

12.53

12.24

11.94

11.65

11.35

11.06

10.76

10.47

10.17

9.88

9.58

9.29

9.00

8.70
3.34. Cryogenic Liquid-Measuring Devices

3-49

Sec. 3.34. Cryogenic Liquid-Measuring 

Devices

A. Application

A.1. - This code applies to devices used for the measurement of cryogenic liquids such as, but not limited to oxygen, 

nitrogen, hydrogen, and argon.

(Amended 1986 and 1995)

A.2. - This code does not apply to the following:

(a) Devices used for dispensing liquefied petroleum gases (for which see Sec. 3.32; Code for Liquefied Petroleum 

Gas and Anhydrous Ammonia Liquid-Measuring Devices).

(b) Devices used solely for dispensing a product in connection with operations in which the amount dispensed does 

not affect customer charges.

(c) Devices used solely for dispensing liquefied natural gas.

(d) mass flow meters (see Sec. 3.37. Code for Mass Flow Meters)

(Added 1994)

A.3. - See also Sec. 1.10; General Code requirements.

S. Specifications

S.1. Design of Indicating and Recording Elements and of Recorded Representations.

S.1.1. Primary Elements.

S.1.1.1. General. - A device shall be equipped with a primary indicating element and may also be equipped 

with a primary recording element.

S.1.1.2. Units. - A device shall indicate and record, if equipped to record, its deliveries in terms of: kilograms 

or pounds; liters or gallons of liquid at the normal boiling point of the specific cryogenic product; cubic meters 

(cubic feet) of gas at a normal temperature of 21 C (70 F) and an absolute pressure of 101.325 kPa (14.696 

psia); or decimal subdivisions or multiples of the measured units cited above.

(Amended 2002)

S.1.1.3. Value of Smallest Unit. - The value of the smallest unit of indicated delivery, and recorded delivery, if 

the device is equipped to record, shall not exceed the equivalent of:

(a) for small delivery devices

(1) 1 L

(2) 0.1 gal

(3) 1 kg

(4) 1 lb

(5) 0.1 m3 of gas

(6) 10 cubic feet of gas

(b) for large delivery devices

(1) 10 L

(2) 1 gal

(3) 10 kg

(4) 10 lb

(5) 1m3 of gas

(6) 100 ft3 of gas
3.34. Cryogenic Liquid-Measuring Devices

3-50

(Amended 2002)

S.1.1.4. Advancement of Indicating and Recording Elements. - Primary indicating and recording elements 

shall be susceptible to advancement only by the normal operation of the device. However, a device may be 

cleared by advancing its elements to zero, but only if:

(a) the advancing movement, once started, cannot be stopped until zero is reached, or

(b) in the case of indicating elements only, such elements are automatically obscured until the elements 

reach the correct zero position.

S.1.1.5. Return to Zero. - Primary indicating and recording elements shall be readily returnable to a definite 

zero indication. Means shall be provided to prevent the return of primary indicating elements and of primary 

recording elements beyond their correct zero position.

S.1.2. Graduations.

S.1.2.1. Length. - Graduations shall be so varied in length that they may be conveniently read.

S.1.2.2. Width. - In any series of graduations, the width of a graduation shall in no case be greater than the 

width of the minimum clear interval between graduations, and the width of main graduations shall be not more 

than 50 percent greater than the width of subordinate graduations. Graduations shall in no case be less than 0.2 

mm (0.008 in) in width.

S.1.2.3. Clear Interval Between Graduations. - The clear interval shall be no less than 1.0 mm (0.04 in). If 

the graduations are not parallel, the measurement shall be made:

(a) along the line of relative movement between the graduations at the end of the indicator, or

(b) if the indicator is continuous, at the point of widest separation of the graduations.

(See also S.1.3.6.)

S.1.3. Indicators.

S.1.3.1. Symmetry. - The index of an indicator shall be symmetrical with respect to the graduations, at least 

throughout that portion of its length associated with the graduations.

S.1.3.2. Length. - The index of an indicator shall reach to the finest graduations with which it is used, unless the 

indicator and the graduations are in the same plane, in which case the distance between the end of the indicator 

and the ends of the graduations, measured along the line of the graduations, shall be not more than 1.0 mm 

(0.04 in).

S.1.3.3. Width. - The width of the index of an indicator in relation to the series of graduations with which it is 

used shall be not greater than:

(a) the width of the narrowest graduation* , and

[*Nonretroactive as of January 1, 2002]

(Amended 2001)

(b) the width of the minimum clear interval between graduations.

When the index of an indicator extends along the entire length of a graduation, that portion of the index of the 

indicator that may be brought into coincidence with the graduation shall be of the same width throughout the 

length of the index that coincides with the graduation.

S.1.3.4. Clearance. - The clearance between the index of an indicator and the graduations shall in no case be 

more than 1.5 mm (0.06 in).
3.34. Cryogenic Liquid-Measuring Devices

3-51

S.1.3.5. Parallax. - Parallax effect shall be reduced to the practicable minimum.

S.1.3.6. Travel of Indicator. - If the most sensitive element of the primary indicating element uses an indicator 

and graduations, the relative movement of these parts corresponding to the smallest indicated value shall be not 

less than 0.5 mm (0.20 in).

S.1.4. Computing-Type Device.

S.1.4.1. Printed Ticket. - Any printed ticket issued by a device of the computing type on which there is printed 

the total computed price shall have printed clearly thereon also the total quantity of the delivery and the price per 

unit.

S.1.4.2. Money-Value Computations. - Money-value computations shall be of the full-computing type in 

which the money value at a single unit price, or at each of a series of unit prices, shall be computed for every 

delivery within either the range of measurement of the device or the range of the computing elements, whichever 

is less. Value graduations shall be supplied and shall be accurately positioned. The total price shall be computed 

on the basis of the quantity indicated when the value of the smallest division indicated is equal to or less than the 

values specified in S.1.1.3.

S.1.4.3. Money Values, Mathematical Agreement. - Any digital money-value indication and any recorded 

money value on a computing type device shall be in mathematical agreement with its associated quantity 

indication or representation to within one cent of money value.

S.2. Design of Measuring Elements.

S.2.1. Vapor Elimination. - A measuring system shall be equipped with an effective vapor eliminator or other 

effective means to prevent the measurement of vapor that will cause errors in excess of the applicable tolerances. 

(See Section T. Tolerances)

S.2.2. Directional Flow Valves. - A valve or valves or other effective means, automatic in operation, to prevent the 

reversal of flow shall be installed in or adjacent to the measuring device.

(Amended 1978)

S.2.3. Maintenance of Liquid State. - A device shall be so designed that the product being measured will remain in 

a liquid state during passage through the device.

S.2.4. Automatic Temperature or Density Compensation. - A device shall be equipped with automatic means for 

adjusting the indication and/or recorded representation of the measured quantity of the product, to indicate and/or 

record in terms of: kilograms or pounds; or liters or gallons of liquid at the normal boiling point of the specific 

cryogenic product; or the equivalent cubic meters (cubic feet) of gas at a normal temperature of 21 C (70 F) and an 

absolute pressure of 101.325 kPa (14.696 lb/in2 absolute). When a compensator system malfunctions, the indicating 

and recording elements may indicate and record in uncompensated volume if the mode of operation is clearly 

indicated, e.g., by a marked annunciator, recorded statement, or other obvious means.*

[*Nonretroactive as of January 1, 1992]

(Amended 1991 and 2002)

S.2.5. Provision for Sealing. - Adequate provision shall be made for applying security seals in such a manner that 

no adjustment or interchange may be made of:

(a) any measurement element,

(b) any adjustable element for controlling delivery rate when such rate tends to affect the accuracy of deliveries, 

and

(c) any automatic temperature or density compensating system.

Any adjusting mechanism shall be readily accessible for purposes of affixing a security seal.
3.34. Cryogenic Liquid-Measuring Devices

3-52

S.3. Design of Discharge Lines and Discharge Line Valves.

S.3.1. Diversion of Measured Liquid. - No means shall be provided by which any measured liquid can be diverted 

from the measuring chamber of the device or the discharge line therefrom, except that a manually controlled outlet 

that may be opened for purging or draining the measuring system shall be permitted. Effective means shall be 

provided to prevent the passage of liquid through any such outlet during normal operation of the device and to 

indicate clearly and unmistakably when the valve controls are so set as to permit passage of liquid through such 

outlet.

S.3.2. Discharge Hose. - The discharge hose of a measuring system shall be of the completely draining dry-hose 

type.

S.4. Level Condition, On-Board Weighing Systems. - Provision shall be made for automatically inhibiting the delivery 

of a cryogenic liquid when the vehicle is out of level beyond the limit required for the performance to be within 

applicable tolerance.

(Added 1986)

S.5. Marking Requirements.

S.5.1. Limitation of Use. - If a measuring system is intended to measure accurately only liquids having particular 

properties, or to measure accurately only under specific installation or operating conditions, or to measure accurately 

only when used in conjunction with specific accessory equipment, these limitations shall be clearly and permanently 

marked on the device.

S.5.2. Discharge Rates. - A meter shall be marked to show its designed maximum and minimum discharge rates.

S.5.3. Temperature or Density Compensation. - Devices equipped with an automatic temperature or density 

compensator, shall be clearly and conspicuously marked on the primary indicating elements, recording elements, and 

recorded representations to show that the quantity delivered has been adjusted to the conditions specified in S.2.4.

N. Notes

N.1. Test Liquid. - A meter shall be tested with the liquid to be commercially measured except that, in a type evaluation 

examination, nitrogen may be used.

N.2. Vaporization and Volume Change. - Care shall be exercised to reduce to a minimum vaporization and volume 

changes. When testing by weight, the weigh tank and transfer systems shall be pre-cooled to liquid temperature prior to 

the start of the test to avoid the venting of vapor from the vessel being weighed.

N.3. Test Drafts.

N.3.1. Gravimetric Test. - Weight test drafts shall be equal to at least the amount delivered by the device in two 

minutes at its maximum discharge rate, and shall in no case be less than 907 kg (2000 lb).

N.3.2. Transfer Standard Test. - When comparing a meter with a calibrated transfer standard, the test draft shall be 

equal to at least the amount delivered by the device in two minutes at its maximum discharge rate, and shall in no 

case be less than 180 L (50 gal) or equivalent thereof. When testing uncompensated volumetric meters in a 

continuous recycle mode, appropriate corrections shall be applied if product conditions are abnormally affected by 

this test mode. 

(Amended 1976)
3.34. Cryogenic Liquid-Measuring Devices

3-53

N.4. Density. - Temperature and pressure of the metered test liquid shall be measured during the test for the 

determination of density or volume correction factors when applicable. For Liquid Density and Volume Correction 

Factors (with respect to temperature and pressure) the following publication shall apply: "Thermophysical Properties of 

Fluids. 1. Argon, Ethylene, Parahydrogen, Nitrogen, Nitrogen Trifluoride, and Oxygen," published in the Journal of 

Physical and Chemical Reference Data, Volume 11, 1982, Supplement No. 1, and published by the American Chemical 

Society and the American Institute of Physics for the National Institute of Standards and Technology.

(Amended 1986)

N.5. Testing Procedures.

N.5.1. Normal Tests. - The "normal" tests of a device shall be made over a range of discharge rates that may be 

anticipated under the conditions of installation.

N.5.1.1. Repeatability Tests. - Tests for repeatability should include a minimum of three consecutive test drafts 

of approximately the same size and be conducted under controlled conditions where variations in factors, such as, 

temperature pressure and flow rate are reduced to the extent that they will not affect the results obtained.

(Added 2001)

N.5.2. Special Tests. - Any test except as set forth in N.5.1. shall be considered a "special" test. Tests shall be 

conducted, if possible, to evaluate any special elements or accessories attached to or associated with the device. 

A device shall be tested at a minimum discharge rate of:

(a) 50 percent of the maximum discharge rate developed under the conditions of installation, or the 

minimum discharge rate marked on the device, whichever is less, or

(b) the lowest discharge rate practicable under conditions of installation.

Special tests may be conducted to develop any characteristics of the device that are not normally anticipated under 

the conditions of installation as circumstances require.

N.6. Temperature Correction. - Corrections shall be made for any changes in volume resulting from the differences in 

liquid temperature between time of passage through the meter and time of volumetric determination of test draft.

N.7. Automatic Temperature or Density Compensation. - When a device is equipped with an automatic temperature 

or density compensator, the compensator shall be tested by comparing the quantity indicated or recorded by the device 

(with the compensator connected and operating) with the actual delivered quantity corrected to the normal boiling point of 

the cryogenic product being measured or to the normal temperature and pressure as applicable.

T. Tolerances

T.1. Application.

T.1.1. To Underregistration and to Overregistration. - The tolerances hereinafter prescribed shall be applied to 

errors of underregistration and errors of overregistration.

T.2. Tolerance Values.

T.2.1. On Normal Tests. - The maintenance tolerance on "normal" tests shall be two and one-half percent (2.5%) of 

the indicated quantity. The acceptance tolerance shall be one and one-half percent (1.5%) of the indicated quantity.

T.2.2. On Special Tests. - The maintenance and acceptance tolerance on "special" tests shall be two and one-half 

percent (2.5%) of the indicated quantity.

T.3. On Tests Using Transfer Standards. - To the basic tolerance values that would otherwise be applied, there shall be 

added an amount equal to two times the standard deviation of the applicable transfer standard when compared to a basic 

reference standard.

(Added 1976)
3.34. Cryogenic Liquid-Measuring Devices

3-54

T.4. Repeatability. - When multiple tests are conducted at approximately the same flow rate and draft size, the range of 

the test results for the flow rate shall not exceed 40 percent of the absolute value of the maintenance tolerance and the 

results of each test shall be within the applicable tolerance. See also N.5.1.1.

(Added 2001)

UR. User Requirements

UR.1. Installation Requirements.

UR.1.1. Discharge Rate. - A device shall be so installed that the actual maximum discharge rate will not exceed the 

rated maximum discharge rate. If necessary, means for flow regulation shall be incorporated in the installation.

UR.1.2. Length of Discharge Hose. - The discharge hose shall be of such a length and design as to keep 

vaporization of the liquid to a minimum.

UR.1.3. Maintenance of Liquid State. - A device shall be so installed and operated that the product being measured 

shall remain in the liquid state during passage through the meter.

UR.2. Use Requirements.

UR.2.1. Return of Indicating and Recording Elements to Zero. - The primary indicating elements (visual) and 

the primary recording elements shall be returned to zero immediately before each delivery.

UR.2.2. Condition of Discharge System. - The discharge system, up to the measuring element, shall be precooled 

to liquid temperatures before a "zero" condition is established prior to the start of a commercial delivery.

UR.2.3. Vapor Return Line. - A vapor return line shall not be used during a metered delivery.

(Amended 1976)

UR.2.4. Drainage of Discharge Line. - On a dry-hose system, upon completion of a delivery, the vendor shall leave 

the discharge line connected to the receiving container with the valve adjacent to the meter in the closed position and 

the valve at the discharge line outlet in the open position for a period of at least

(a) 1 minute for small delivery devices, and

(b) 3 minutes for large delivery devices,

to allow vaporization of some product in the discharge line to force the remainder of the product in the line to flow 

into the receiving container.

(Amended 1976)

UR.2.5. Conversion Factors. - Established conversion values (see references in N.4.) shall be used whenever 

metered liquids are to be billed in terms of:

(a) kilograms or pounds based on a meter indication of liters, gallons, cubic meters of gas, or cubic feet of gas; 

or,

(b) cubic meters or cubic feet of gas based on a meter indication of liters or gallons, kilograms, or pounds; or,

(c) liters or gallons based on a meter indication of kilograms or pounds, cubic meters of gas or cubic feet of gas.

All sales of cryogenic liquids shall be based on either kilograms or pounds, liters or gallons at NBP1

, cubic meters of 

gas or cubic feet of gas at NTP1

(Amended 1986)

.

 1

See Appendix D, Definitions.
3.34. Cryogenic Liquid-Measuring Devices

3-55

UR.2.6. Temperature or Density Compensation.

UR.2.6.1. Use of Automatic Temperature or Density Compensators. - If a device is equipped with an 

automatic temperature or density compensator, this shall be connected, operable, and in use at all times. Such 

automatic temperature or density compensator may not be removed, nor may a compensated device be replaced 

with an uncompensated device, without the written approval of the weights and measures authority having 

jurisdiction over the device.

UR.2.6.2. Tickets or Invoices. - Any written invoice or printed ticket based on a reading of a device that is 

equipped with an automatic temperature or density compensator shall have shown thereon that the quantity 

delivered has been adjusted to the quantity at the NBP of the specific cryogenic product or the equivalent volume 

of gas at NTP.

UR.2.6.3. Printed Ticket. - Any printed ticket issued by a device of the computing type on which there is 

printed the total computed price, the total quantity of the delivery, or the price per unit, shall also show the other 

two values (either printed or in clear hand script).

UR.2.6.4. Ticket in Printing Device. - A ticket shall not be inserted into a device equipped with a ticket printer 

until immediately before a delivery is begun, and in no case shall a ticket be in the device when the vehicle is in 

motion while on a public street, highway, or thoroughfare.

UR.2.7. Pressure of Tanks with Volumetric Metering Systems without Temperature Compensation. - When 

the saturation pressure of the product in the vendor's tank exceeds 240 kPa (35 psia), a correction shall be applied to 

the written invoice or printed ticket using the appropriate tables as listed in N.4.; or the saturation pressure shall be 

reduced to 207 kPa (30 psia) (if this can be safely accomplished) prior to making a delivery.

(Added 1976)
3.34. Cryogenic Liquid-Measuring Devices

3-56
3.35. Milk Meters

3-57

Sec. 3.35. Milk Meters

A. Application

A.1. - This code applies to devices used for the measurement of milk; generally applicable to, but not limited to, meters 

used in dairies, milk processing plants, and cheese factories, to measure incoming bulk milk.

A.2. - See also Sec. 1.10; General Code requirements.

A.3. - This code does not apply to mass flow meters (see Sec. 3.37. Code for Mass Flow Meters).

(Added 1994)

S. Specifications

S.1. Design of Indicating and Recording Elements and of Recorded Representations.

S.1.1. Primary Elements

S.1.1.1. General. - A meter shall be equipped with a primary indicating element and may also be equipped with 

a primary recording element.

S.1.1.2. Units. -

(a) A meter shall indicate, and record if the meter is equipped to record, its deliveries in terms of liters or 

gallons. Fractional parts of the liter shall be in terms of decimal subdivisions. Fractional parts of the 

gallon shall be in terms of either decimal or binary subdivisions.

(b) (b) When it is an industry practice to purchase and sell milk by weight based upon 1.03 kg/L 

(8.6 lb/gal), the primary indicating element may indicate in kilograms or pounds. The weight value 

division shall be a decimal multiple or submultiple of 1, 2, or 5. Fractional parts of the kilogram or 

pound shall be in decimal subdivisions. (See S.4.5.)

S.1.1.3. Value of Smallest Unit. - The value of the smallest unit of indicated quantity and recorded quantity, if 

the meter is equipped to record, shall not exceed the equivalent of:

(a) 0.5 L or 5 kg (1 pt or 1 lb) when measuring quantities less than or equal to 4000 L or 4000 kg (1000 gal 

or 8600 lb), or

(b) 5 L or 5 kg (1 gal or 10 lb) when measuring quantities in excess of 4000 L or 4000 kg (1000 gal or 

8600 lb).

(Amended 1989)

S.1.1.4. Advancement of Indicating and Recording Elements. - Primary indicating and recording elements 

shall be susceptible to advancement only by the mechanical operation of the meter. However, a meter may be 

cleared by advancing its elements to zero, but only if:

(a) the advancing movement, once started, cannot be stopped until zero is reached, or

(b) in the case of indicating elements only, such elements are automatically obscured until the elements 

reach the correct zero position.

S.1.1.5. Return to Zero. - Primary indicating elements and primary recording elements, if the device is 

equipped to record, shall be readily returnable to a definite zero indication. Means shall be provided to prevent 

the return of the primary indicating elements and the primary recording elements, if the device is so equipped, 

beyond their correct zero position.
3.35. Milk Meters

3-58

S.1.1.6. Indication of Measurement. A meter shall be constructed to show automatically its initial zero 

condition and the volume measured up to the nominal capacity of the device.

S.1.2. Graduations.

S.1.2.1. Length. - Graduations shall be so varied in length that they may be conveniently read.

S.1.2.2. Width. - In any series of graduations, the width of a graduation shall in no case be greater then the 

width of the minimum clear interval between graduations, and the width of main graduations shall be not more 

than 50 percent greater than the width of subordinate graduations. Graduations shall in no case be less than 

0.2 mm (0.008 in) in width.

S.1.2.3. Clear Interval Between Graduations. - The clear interval shall be not less than 1.0 mm (0.04 in). If 

the graduations are not parallel, the measurement shall be made:

(a) along the line of relative movement between the graduations at the end of the indicator, or

(b) if the indicator is continuous, at the point of widest separation of the graduations.

S.1.3. Indicators.

S.1.3.1. Symmetry. - The index of an indicator shall be symmetrical with respect to the graduations, at least 

throughout that portion of its length associated with the graduations.

S.1.3.2. Length. - The index of an indicator shall reach to the finest graduations with which it is used, unless the 

indicator and the graduations are in the same plane, in which case the distance between the end of the indicator 

and the ends of the graduations, measured along the line of graduations, shall be not more than 1.0 mm (0.04 in).

S.1.3.3. Width. - The width of the index of an indicator in relation to the series of graduations with which it is 

used shall be not greater than:

(a) the width of the narrowest graduation* , and

[*Nonretroactive as of January 1, 2002]

(Amended 2001)

(b) the width of the minimum clear interval between graduations.

When the index of an indicator extends along the entire length of a graduation, that portion of the index of the 

indicator that may be brought into coincidence with the graduation shall be of the same width throughout the 

length of the index that coincides with the graduation.

S.1.3.4. Clearance. - The clearance between the index of an indicator and the graduations shall in no case be 

more than 1.5 mm (0.06 in).

S.1.3.5. Parallax. - Parallax effects shall be reduced to the practicable minimum.

S.1.3.6. Travel of Indicator. - If the most sensitive element of the primary indicating element utilizes an 

indicator and graduations, the relative movement of these parts corresponding to the smallest indicated value 

shall be not less than 5 mm (0.20 in).

S.1.4. Computing-Type Devices.

S.1.4.1. Display of Unit Price. - In a device of the computing type, means shall be provided for displaying on 

the outside of the device, and in close proximity to the display of the total computed price, the price per unit at 

which the device is set to compute.
3.35. Milk Meters

3-59

S.1.4.2. Printed Ticket. - If a computing-type device issues a printed ticket which displays the total computed 

price, the ticket also shall have printed clearly thereon the total quantity of the delivery, the appropriate fraction 

of the quantity, and the price per unit of quantity.

(Amended 1989)

S.1.4.3. Money-Value Computations. - Money-value computations shall be of the full-computing type in 

which the money value at a single unit price, or at each of a series of unit prices, shall be computed for every 

delivery within either the range of measurement of the device or the range of the computing elements, whichever 

is less. Value graduations shall be supplied and shall be accurately positioned. The value of each graduated 

interval shall be 1 cent.

S.1.4.4. Money Values, Mathematical Agreement. Any digital money-value indication and any recorded 

money value on a computing-type device shall be in mathematical agreement with its associated quantity 

indicating or representation to within 1 cent of money value.

S.2. Design of Measuring Elements.

S.2.1. Vapor Elimination. - A metering system shall be equipped with an effective vapor eliminator or other 

effective means automatic in operation to prevent the passage of vapor and air through the meter. Vent lines from the 

air (or vapor) eliminator shall be made of metal tubing or some other suitably rigid material.

S.2.2. Maintaining Flooded Condition. - The vent on the vapor eliminator shall be positioned or installed in such a 

manner that the vapor eliminator cannot easily be emptied between uses.

S.2.3. Provision for Sealing. - Adequate provision shall be made for applying security seals to the adjustment 

mechanism and the register.

S.2.4. Directional Flow Valves. - Valves intended to prevent reversal of flow shall be automatic in operation.

S.3. Design of Intake Lines.

S.3.1. Diversion of Liquid to be Measured. - No means shall be provided by which any liquid can be diverted from 

the supply tank to the receiving tank without being measured by the device. A manually controlled outlet that may 

be opened for purging or draining the measuring system shall be permitted. Effective means shall be provided to 

prevent passage of liquid through any such outlet during normal operation of the measuring system.

(Amended 1994)

S.3.2. Intake Hose. - The intake hose shall be:

(a) of the dry-hose type,

(b) adequately reinforced,

(c) not more than 6 m (20 ft) in length unless it can be demonstrated that a longer hose is essential to permit 

transfer from a supply tank; and

(d) connected to the pump at horizontal or above to permit complete drainage of the hose.

(Amended 1991)

S.4. Marking Requirements.

S.4.1. Limitation of Use. - If a meter is intended to measure accurately only liquids having particular properties, or 

to measure accurately only under specific installation or operating conditions, or to measure accurately only when 

used in conjunction with specific accessory equipment, these limitations shall be clearly and permanently stated on 

the meter.

S.4.2. Discharge Rates. - A meter shall be marked to show its designed maximum and minimum discharge rates. 

However, the minimum discharge rate shall not exceed 20 percent of the maximum discharge rate.
3.35. Milk Meters

3-60

S.4.3. Measuring Components. - All components that affect the measurement of milk that are disassembled for 

cleaning purposes shall be clearly and permanently identified with a common serial number.

S.4.4. Flood Volume. - When applicable, the volume of product (to the nearest minimum division of the meter) 

necessary to flood the system when dry shall be clearly, conspicuously, and permanently marked on the air 

eliminator.

S.4.5. Conversion Factor. - When the conversion factor of 1.03 kg/L (8.6 lb/gal) is used to convert the volume of 

milk to weight, the conversion factor shall be clearly marked on the primary indicating element and recorded on the 

delivery ticket.

N. Notes

N.1. Test Liquid.

(a) A meter shall be tested with the liquid to be commercially measured or with a liquid of the same general physical 

characteristics. Following a satisfactory examination, the weights and measures official should attach a seal or 

tag indicating the product used during the test.

(b) (Amended 1989)

(c) A milk measuring system shall be tested with the type of milk to be measured when the accuracy of the system is 

affected by the characteristics of milk (e.g., positive displacement meters).

(Added 1989)

N.2. Evaporation and Volume Change. - Care shall be exercised to reduce to a minimum, evaporation losses and 

volume changes resulting from changes in temperature of the test liquid.

N.2.1. Temperature Correction. - Corrections shall be made for any changes in volume resulting from the 

differences in liquid temperatures between time of passage through the meter and time of volumetric determination in 

the test measure. When adjustments are necessary, appropriate tables should be used.

N.3. Test Drafts. - Test drafts should be equal to at least the amount delivered by the device in one minute at its 

maximum discharge rate, and shall in no case be less than 400 L or 400 kg (100 gal or 1000 lb).

(Amended 1989)

N.4. Testing Procedures.

N.4.1. Normal Tests. - The "normal" test of a meter shall be made at the maximum discharge rate that may be 

anticipated under the conditions of the installation. The "normal" test shall include a determination of the 

effectiveness of the air elimination system.

N.4.1.1. Repeatability Tests. – Tests for repeatability should include a minimum of three consecutive test 

drafts of approximately the same size and be conducted under controlled conditions where variations in factors, 

such as temperature, pressure, and flow rate are reduced to the extent that they will not affect the results 

obtained.

(Added 2002) 

N.4.2. Special Tests. - "Special" tests to develop the operating characteristics of a meter and any special elements 

and accessories attached to or associated with the meter, shall be made as circumstances require. Any test except as 

set forth in N.4.1. shall be considered a special test.

N.4.3. System Capacity. - The test of a milk-metering system shall include the verification of the volume of product 

necessary to flood the system as marked on the air eliminator.
3.35. Milk Meters

3-61

T. Tolerances

T.1. Application.

T.1.1. To Underregistration and to Overregistration. -

The tolerances hereinafter prescribed shall be applied to 

errors of underregistration and errors of overregistration.

T.2. Tolerance Values. - Maintenance and acceptance 

tolerances shall be as shown in Table 1.

(Amended 1989)

T.3. Repeatability – When multiple tests are conducted at 

approximately the same flow rate and draft size, the range of 

the test results for the flow rate shall not exceed 40 percent of 

the absolute value of the maintenance tolerance and the 

results of each test shall be within the applicable tolerance. 

See also N.4.1.1.

(Added 2002)

UR. User Requirements

UR.1. Installation Requirements.

UR.1.1. Plumb and Level Condition. - A device installed in a fixed location shall be installed plumb and level, and 

the installation shall be sufficiently strong and rigid to maintain this condition.

UR.1.2. Discharge Rate. - A meter shall be so installed that the actual maximum discharge rate will not exceed the 

rated maximum discharge rate. If necessary, means for flow regulation shall be incorporated in the installation, in 

which case this shall be fully effective and automatic in operation.

UR.1.3. Unit Price. - There shall be displayed on the face of a device of the computing type the unit price at which 

the device is set to compute.

UR.1.4. Intake Hose. - The intake hose shall be so installed as to permit complete drainage and that all available 

product is measured following each transfer.

UR.2. Use Requirements.

UR.2.1. Return of Indicating and Recording Elements to Zero. - The primary indicating elements (visual), and 

the primary recording elements when these are returnable to zero, shall be returned to zero before each transfer.

UR.2.2. Printed Ticket. - Any printed ticket issued by a device of the computing type on which there is printed the 

total computed price, the total quantity, or the price per unit of quantity, shall also show the other two values (either 

printed or in clear script).

(Amended 1989)

UR.2.3. Ticket in Printing Device. - A ticket shall not be inserted into a device equipped with a ticket printer until 

immediately before a transfer is begun. If the meter is mounted on a vehicle, in no case shall a ticket be in the device 

when the vehicle is in motion while on a public street, highway, or thoroughfare.

UR.2.4. Credit for Flood Volume. - The volume of product necessary to flood the system as marked on the air 

eliminator shall be individually recorded on the ticket of each transfer affected.

Table 1. Tolerances for Milk Meters

Indication Maintenance Acceptance

gallons gallons gallons

100 0.5 0.3

200 0.7 0.4

300 0.9 0.5

400 1.1 0.6

500 1.3 0.7

Over 500 Add 0.002 gallon 

per indicated 

gallon over 500

Add 0.001 gallon per indicated 

gallon over 500

(Added 1989)
3.35. Milk Meters

3-62
3.36. Water Meters

3-63

Sec. 3.36. Water Meters

A. Application

A.1. - This code applies to devices used for the measurement of water; generally applicable to, but not limited to, utilities 

type meters installed in residences or business establishments and meters installed in batching systems.

(Amended 2002)

A.2. - This code does not apply to:

(a) water meters mounted on vehicle tanks (for which see Sec. 3.31; Code for Vehicle-Tank Meters).

(b) mass flow meters (see Sec. 3.37. Code for Mass Flow Meters)

(Added 1994)

A.3. - See also Sec. 1.10; General Code requirements.

S. Specifications

S.1. Design of Indicating and Recording Elements and of Recorded Representations.

S.1.1. Primary Elements.

S.1.1.1. General. - A water meter shall be equipped with a primary indicating element and may also be 

equipped with a primary recording element. Such elements shall be visible at the point of measurement or be 

stored in non-volatile and nonresettable memory. The display may be remotely located provided it is readily 

accessible to the customer.

(Amended 2002)

S.1.1.2. Units. - A water meter shall indicate and record, if the device is equipped to record, its deliveries in 

terms of liters, gallons or cubic feet or binary or decimal subdivisions thereof except batch plant meters, which 

shall indicate deliveries in terms of liters, gallons or decimal subdivisions of the liter or gallon only.

S.1.1.3. Value of Smallest Unit. - The value of the smallest unit of indicated delivery and recorded delivery, if 

the device is equipped to record, shall not exceed the equivalent of:

(a) 50 L (10 gal) on utility type meters,

(b) 0.2 L (1/10 gal) on batching meters delivering less than 375 L/min (100 gal/min), or

(c) 5 L (1 gal) on batching meters delivering 375 L/min (100 gal/min) or more.

S.1.1.4. Advancement of Indicating and Recording Elements. - Primary indicating and recording elements 

shall be susceptible to advancement only by the mechanical operation of the device.

S.1.1.5. Return to Zero. - If the meter is so designed that the primary indicating elements are readily returnable 

to a definite zero indication, means shall be provided to prevent the return of these elements beyond their correct 

zero position.

S.1.2. Graduations.

S.1.2.1. Length. - Graduations shall be so varied in length that they may be conveniently read.

S.1.2.2. Width. - In any series of graduations, the width of a graduation shall in no case be greater than the 

width of the minimum clear interval between graduations, and the width of main graduations shall be not more 

than 50 percent greater than the width of subordinate graduations. Graduations shall in no case be less than 0.2 

mm (0.008 in) in width.
3.36. Water Meters

3-64

S.1.2.3. Clear Interval Between Graduations. - The clear interval shall not be less than 1.0 mm (0.04 in). If 

the graduations are not parallel, the measurement shall be made:

(a) along the line of relative movement between the graduations at the end of the indicator, or

(b) if the indicator is continuous, at the point of widest separation of the graduations.

S.1.3. Indicators.

S.1.3.1. Symmetry. - The index of an indicator shall be symmetrical with respect to the graduations, at least 

throughout that portion of its length associated with the graduations.

S.1.3.2. Length. - The index of an indicator shall reach to the finest graduations with which it is used, unless the 

indicator and the graduations are in the same plane, in which case the distance between the end of the indicator 

and the ends of the graduations, measured along the line of the graduations, shall be not more than 1.0 mm 

(0.04 in).

S.1.3.3. Width. - The width of the index of an indicator in relation to the series of graduations with which it is 

used shall not be greater than:

(a) the width of the narrowest graduation* , and

[*Nonretroactive as of January 1, 2002]

(Amended 2001)

(b) the width of the minimum clear interval between graduations.

When the index of an indicator extends along the entire length of a graduation, that portion of the index of the 

indicator that may be brought into coincidence with the graduation shall be of the same width throughout the 

length of the index that coincides with the graduation.

S.1.3.4. Clearance. - The clearance between the index of an indicator and the graduations shall in no case be 

more than 1.5 mm (0.06 in).

S.1.3.5. Parallax. - Parallax effects shall be reduced to the practicable minimum.

S.2. Design of Measuring Elements.

S.2.1. Provision for Sealing. - Adequate provision shall be made for applying security seals in such a manner that

no adjustment may be made of:

(a) any measurement elements, and

(b) any adjustable element for controlling delivery rate when such rate tends to affect the accuracy of deliveries.

The adjusting mechanism shall be readily accessible for purposes of affixing a security seal.

S.2.2. Batching Meters Only.

S.2.2.1. Air Elimination. - Batching meters shall be equipped with an effective air eliminator.

S.2.2.2. Directional Flow Valves. - Valves intended to prevent reversal of flow shall be automatic in operation.

N. Notes

N.1. Test Liquid. - A meter shall be tested with water.
3.36. Water Meters

3-65

N.2. Evaporation and Volume Change. - Care shall be exercised to reduce to a minimum, evaporation losses and 

volume changes resulting from changes to temperature of the test liquid.

N.3. Test Drafts. - Test drafts should be equal to at least the amount delivered by the device in 2 minutes and in no case 

less than the amount delivered by the device in 1 minute at the actual maximum flow rate developed by the installation. 

The test drafts shown in Table 1, next page, shall be followed as closely as possible.

N.4. Testing Procedures.

N.4.1. Normal Tests. The normal test of a meter shall be made at the maximum discharge rate developed by the 

installation. Meters with maximum gallon per minute ratings higher than Table 1 values may be tested up to the 

meter rating, with meter indications no less than those shown.

(Amended 1990 and 2002)

N.4.1.1. Repeatability Tests. – Tests for repeatability should include a minimum of three consecutive test 

drafts of approximately the same size and be conducted under controlled conditions where variations in factors, 

such as temperature, pressure, and flow rate are reduced to the extent that they will not affect the results 

obtained.

(Added 2002)

N.4.2. Special Tests. - Special tests to develop the operating characteristics of meters may be made according to the 

rates and quantities shown in Table 2.

N.4.3. Batching Meter Tests. - Tests on batching meters should be conducted at the maximum and intermediate 

rates only.

T. Tolerances

T.1. Tolerance Values. - Maintenance and acceptance tolerances shall be as shown in Table 1 and Table 2.

T.1.1. Repeatability. – When multiple tests are conducted at approximately the same flow rate, the range of the 

test results shall not exceed 0.6 percent for tests performed at the normal and intermediate flow rates, and 1.3 

percent for tests performed at the minimum flow rate, and each test shall be within the applicable tolerance.

(Added 2002)

Table 1. Tolerances for Water Meters

Normal Tests

Meter size

(inches)

Rate of flow

(gal/min)

Maximum Rate

Meter

indication

Tolerance on overand undergal ft registration 3

Less than 5/8 8 50 5

1.5%

5/8 15 50 5

3/4 25 50 5

1 40 100 10

1 1/2 80 300 40

2 120 500 40

3 250 500 50

4 350 1 000 100

6 700 1 000 100
3.36. Water Meters

3-66

UR. User Requirements

UR.1. Batching Meters Only.

UR.1.1. Strainer. - A filter or strainer shall be provided if it is determined that the water contains excessive amounts 

of foreign material.UR.1.2. Siphon Breaker. - An automatic siphon breaker or other effective means shall be 

installed in the discharge piping at the highest point of outlet, in no case below the top of the meter, to prevent 

siphoning of the meter and permit rapid drainage of the pipe or hose.

UR.1.3. Provision for Testing. - Acceptable provisions for testing shall be incorporated into all meter systems. 

Such provisions shall include a two-way valve, or manifold valving, and a pipe or hose installed in the discharge line 

accessible to the proper positioning of the test measure.

Table 2. Tolerances for Water Meters

Special Tests

Meter size 

(inches)

Intermediate Rate Minimum Rate

Rate of 

flow 

(gal/

min)

Meter

indication Tolerance on 

over- and 

underregistration

Rate of 

flow

(gal/

min)

Meter

indication Tolerance

gal ft3 gal ft3

UnderregistrationOverregistration

Less than or 

equal to 5/8 2 10 1

1.5%

1/4 5 1

5.0% 1.5%

3/4 3 10 1 1/2 5 1

1 4 10 1 3/4 5 1

1 1/2 8 50 5 1 1/2 10 1

2 15 50 5 2 10 1

3 20 50 5 4 10 1

4 40 100 10 7 50 5

6 60 100 10 12 50 5
3.37. Mass Flow Meters

3-67

Sec. 3.37. Mass Flow Meters

A. Application

A.1. Liquids. - This code applies to devices that are designed to dynamically measure the mass, or the mass and density 

of liquids. It also specifies the relevant examinations and tests that are to be conducted.

(Amended 1997)

A.2. Vapor (Gases). - This code applies to devices that are designed to dynamically measure the mass of hydrocarbon 

gas in the vapor state. Examples of these products are propane, propylene, butanes, butylenes, ethane, methane, natural 

gas and any other hydrocarbon gas/air mix.

S. Specifications

S.1. Indicating and Recording Elements.

S.1.1. Indicating Elements. - A measuring assembly shall include an indicating element. Indications shall be clear, 

definite, accurate, and easily read under normal conditions of operation of the instrument.

S.1.2. Compressed Natural Gas Dispensers. - Except for fleet sales and other price contract sales, a compressed 

natural gas dispenser used to refuel vehicles shall be of the computing type and shall indicate the quantity, the unit 

price, and the total price of each delivery. The dispenser shall display the mass measured for each transaction either 

continuously on an external or internal display accessible during the inspection and test of the dispenser, or display 

the quantity in mass units by using controls on the device.

(Added 1994)

S.1.3. Units. -

S.1.3.1. Units of Measurement. - Deliveries shall be indicated and recorded in grams, kilograms, metric tons, 

pounds, tons, and/or liters, gallons, quarts, pints and decimal subdivisions thereof. The indication of a delivery 

shall be on the basis of apparent mass versus a density of 8.0 g/cm3. The volume indication shall be based on 

the mass measurement and an automatic means to determine and correct for changes in product density.

(Amended 1993 and 1997)

S.1.3.1.1. Compressed Natural Gas Used as an Engine Fuel. - When compressed natural gas is dispensed 

as an engine fuel, the delivered quantity shall be indicated in "gasoline liter equivalent (GLE) units" or 

"gasoline gallon equivalent (GGE) units" (see definitions).

(Added 1994)

S.1.3.2. Numerical Value of Quantity-Value Divisions. - The value of a scale interval shall be equal to: 

- 1, 2, or 5, or

- a decimal multiple or submultiple of 1, 2, or 5.

S.1.3.3. Maximum Value of Quantity-Value Divisions.

(a) The maximum value of the quantity-value division for liquids shall be not greater than 0.2 percent of 

the minimum measured quantity.

(b) For dispensers of compressed natural gas used to refuel vehicles, the value of the division for the 

gasoline liter equivalent shall not exceed 0.01 GLE; the division for gasoline gallon equivalent (GGE) 

shall not exceed 0.001 GGE. The maximum value of the mass division shall not exceed 0.001 kg or 

0.001 lb.

(Amended 1994)
3.37. Mass Flow Meters

3-68

S.1.3.4. Values Defined. - Indicated values shall be adequately defined by a sufficient number of figures, 

words, symbols, or combinations thereof. A display of "zero" shall be a zero digit for all displayed digits to the 

right of the decimal mark and at least one to the left.

S.2. Operating Requirements.

S.2.1. Return to Zero. - Except for measuring assemblies in a pipeline:

(a) One indicator and the primary recording elements, if the device is equipped to record, shall be provided with 

a means for readily returning the indication to zero either automatically or manually.

(b) It shall not be possible to return primary indicating elements, or primary recording elements, beyond the 

correct zero position.

(Amended 1993)

S.2.2. Indicator Reset Mechanism. - The reset mechanism for the indicating element shall not be operable during a 

delivery. Once the zeroing operation has begun, it shall not be possible to indicate a value other than the latest 

measurement, or "zeros" when the zeroing operation has been completed. 

S.2.3. Nonresettable Indicator. - An instrument may also be equipped with a nonresettable indicator if the indicated 

values cannot be construed to be the indicated values of the resettable indicator for a delivered quantity.

S.2.4. Provisions for Power Loss.

S.2.4.1. Transaction Information. - In the event of a power loss, the information needed to complete any 

transaction in progress at the time of the power loss (such as the quantity and unit price, or sales price) shall be 

determinable for at least 15 minutes at the dispenser or at the console if the console is accessible to the customer.

(Added 1993)

S.2.4.2. User Information. - The device memory shall retain information on the quantity of fuel dispensed and 

the sales price totals during power loss.

(Added 1993)

S.2.5. Display of Unit Price and Product Identity.

S.2.5.1. Unit Price. - A computing or money-operated device shall be able to display on each face the unit 

price at which the device is set to compute or to dispense.

(Added 1993)

S.2.5.2. Product Identity. - A device shall be able to conspicuously display on each side the identity of the 

product being dispensed.

(Added 1993)

S.2.5.3. Selection of Unit Price. - Except for dispensers used exclusively for fleet sales, other price contract 

sales, and truck refueling (e.g., truck stop dispensers used only to refuel trucks), when a product or grade is 

offered for sale at more than one unit price through a computing device, the selection of the unit price shall be 

made prior to delivery using controls on the device or other customer-activated controls. A system shall not 

permit a change to the unit price during delivery of a product. 

[Nonretroactive as of January 1, 1998]

(Added 1997)

S.2.5.4. Agreement Between Indications. - When a quantity value indicated or recorded by an auxiliary 

element is a derived or computed value based on data received from a retail motor fuel dispenser, the value may 

differ from the quantity value displayed on the dispenser, provided the following conditions are met:

(a) all total money values for an individual sale that are indicated or recorded by the system agree; and
3.37. Mass Flow Meters

3-69

(b) within each element the values indicated or recorded meet the formula (quantity x unit price = total 

sales price) to the closest cent.

[Nonretroactive as of January 1, 1998]

(Added 1997)

S.2.6. Money-Value Computations. - A computing device shall compute the total sales price at any single-purchase 

unit price (i.e., excluding fleet sales, other price contract sales, and truck stop dispensers used only to refuel trucks) 

for which the product being measured is offered for sale at any delivery possible within either the measurement range 

of the device or the range of the computing elements, whichever is less.

(Added 1993)

S.2.6.1. Auxiliary Elements. - If a system is equipped with auxiliary indications, all indicated money value and 

quantity divisions of the auxiliary element shall be identical with those of the primary element.

(Added 1993)

S.2.6.2. Display of Quantity and Total Price. - When a delivery is completed, the total price and quantity for 

that transaction shall be displayed on the face of the dispenser for at least 5 minutes or until the next transaction 

is initiated by using controls on the device or other user-activated controls.

(Added 1993)

S.2.7. Recorded Representations, Point of Sale Systems. - The sales information recorded by cash registers when 

interfaced with a retail motor-fuel dispenser shall contain the following information for products delivered by the 

dispenser:

(a) the total volume of the delivery,

(b) the unit price,

(c) the total computed price, and

(d) the product identity by name, symbol, abbreviation, or code number.

[Nonretroactive as of January1, 1986]

(Added 1993)

S.2.8. Indication of Delivery. - The device shall automatically show on its face the initial zero condition and the 

quantity delivered (up to the nominal capacity). However, the first 0.03 L (0.009 gal) of a delivery and its associated 

total sales price need not be indicated.

[Nonretroactive as of January 1, 1998]

(Added 1997)

S.3. Measuring Elements and Measuring Systems.

S.3.1. Maximum and Minimum Flow-Rates.

(a) The ratio of the maximum to minimum flow-rates specified by the manufacturer for devices measuring 

liquified gases shall be 5:1 or greater.

(b) The ratio of the maximum to minimum flow-rates specified by the manufacturer for devices measuring other 

than liquified gases shall be 10:1 or greater.

S.3.2. Adjustment Means. - An assembly shall be provided with means to change the ratio between the indicated 

quantity and the quantity of liquid measured by the assembly. A bypass on the measuring assembly shall not be used 

for these means.

S.3.2.1. Discontinuous Adjusting Means. When the adjusting means changes the ratio between the indicated 

quantity and the quantity of measured liquid in a discontinuous manner, the consecutive values of the ratio shall 

not differ by more than 0.1 percent.
3.37. Mass Flow Meters

3-70

S.3.3. Vapor Elimination. - A liquid-measuring instrument or measuring system shall be equipped with an effective 

vapor or air eliminator or other effective means, automatic in operation, to prevent the measurement of vapor and air. 

Vent lines from the air or vapor eliminator shall be made of metal tubing or some other suitable rigid material.

(Amended 1999)

S.3.3.1. Vapor Elimination on Loading Rack Liquid Metering Systems. -

(a) A loading rack liquid metering system shall be equipped with a vapor or air eliminator or other 

automatic means to prevent the passage of vapor and air through the meter unless the system is 

designed or operationally controlled by a method, approved by the weights and measures jurisdiction 

having statutory authority over the device, such that neither air nor vapor can enter the system.

(b) Vent lines from the air or vapor eliminator (if present) shall be made of metal tubing or other rigid 

material.

(Added 1995)

S.3.4. Maintenance of Liquid State. - A liquid-measuring device shall be installed so that the measured product 

remains in a liquid state during passage through the instrument.

S.3.5. Provision for Sealing. - Adequate provision shall be made for an approved means of security (e.g., data 

change audit trail) or physically applying security seals in such a manner that no adjustment may be made of:

(a) any measurement element;

(b) any adjustable element for controlling delivery rate when such rate tends to affect the accuracy of deliveries; 

or

(c) the zero adjustment mechanism.

When applicable, the adjusting mechanism shall be readily accessible for purposes of affixing a security seal.

Audit trails shall use the format set forth in Table S.3.5.

(Amended 1992 and 1995)

S.3.6. Automatic Density Correction.

(a) An automatic means to determine and correct for changes in product density shall be incorporated in any 

mass flow metering system that is affected by changes in the density of the product being measured.

(b) Volume-measuring devices with automatic temperature compensation used to measure natural gas as a 

motor vehicle engine fuel shall be equipped with an automatic means to determine and correct for changes 

in product density due to changes in the temperature, pressure, and composition of the product.

(Amended 1994 and 1997)

S.3.7. Pressurizing the Discharge Hose. - The discharge hose for compressed natural gas shall 

automatically pressurize prior to the device beginning to register the delivery.

(Added 1993)
3.37. Mass Flow Meters

3-71

Nonretroactive as of January 1, 1995]

(Table Added 1995)(Amended 1995, 1998, and 1999)

S.3.8. Zero-Set-Back Interlock, Retail Motor-Fuel Devices. - A device shall be constructed so that:

(a) after a delivery cycle has been completed by moving the starting lever to any position that shuts off the 

device, an automatic interlock prevents a subsequent delivery until the indicating elements, and recording 

elements if the device is equipped and activated to record, have been returned to their zero positions;

(b) the discharge nozzle cannot be returned to its designed hanging position (that is, any position where the tip 

of the nozzle is placed in its designed receptacle and the lock can be inserted) until the starting lever is in its 

designed shut-off position and the zero-set-back interlock has been engaged; and

(c) in a system with more than one dispenser supplied by a single pump, an effective automatic control valve in 

each dispenser prevents product from being delivered until the indicating elements on that dispenser are in a 

correct zero position.

(Added 1993)

Table S.3.5. Categories of Device and Methods of Sealing

Categories of Device Method of Sealing

Category 1: No remote configuration 

capability.

Seal by physical seal or two event counters: one for calibration 

parameters and one for configuration parameters.

Category 2: Remote configuration capability, 

but access is controlled by physical hardware. 

Device shall clearly indicate that it is in the 

remote configuration mode and record such 

message if capable of printing in this mode or 

shall not operate while in this mode.

[Category 2 applies to only devices 

manufactured prior to January 1, 2005. 

Devices with remote configuration capability 

manufactured or in use after that date must 

meet the sealing requirements outlined in 

Category 3. Devices without remote 

configuration capability manufactured after 

that date will be required to meet the 

minimum criteria outlined in Category 1].

[The hardware enabling access for remote communication 

must be on-site. The hardware must be sealed using a physical 

seal or event counter for calibration parameters and an event 

counter for configuration parameters. The event counters may 

be located either at the individual measuring device or at the 

system controller; however, an adequate number of counters 

must be provided to monitor the calibration and configuration 

parameters of the individual devices at a location. If the 

counters are located in the system controller rather than at the 

individual device, means must be provided to generate a hard 

copy of the information through an on-site device.]*

[*Nonretroactive as of January 1, 1996]

Category 3: Remote configuration capability 

access may be unlimited or controlled through 

a software switch (e.g., password).

The device shall clearly indicate that it is in 

the remote configuration mode and record 

such message if capable of printing in this 

mode or shall not operate while in this mode.

[Nonretroactive as of January 1, 2001]

Nonretroactive as of January 1, 2005, all 

devices with remote configuration capability 

must comply with the sealing requirements of 

Category 3.

An event logger is required in the device; it must include an 

event counter (000 to 999), the parameter ID, the date and time 

of the change, and the new value of the parameter. A printed 

copy of the information must be available through the device 

or through another on-site device. The event logger shall have 

a capacity to retain records equal to ten times the number of 

sealable parameters in the device, but not more than 1000 

records are required. (Note: Does not require 1000 changes to 

be stored for each parameter.)
3.37. Mass Flow Meters

3-72

S.4. Discharge Lines and Valves.

S.4.1. Diversion of Measured Product. - No means shall be provided by which any measured product can be 

diverted from the measuring instrument. However, two or more delivery outlets may be permanently installed and 

operated simultaneously, provided that any diversion of flow to other than the intended receiving receptacle cannot 

be readily accomplished or is readily apparent. Such means include physical barriers, visible valves or indications 

that make it clear which outlets are in operation, and explanatory signs if deemed necessary.

A manually controlled outlet that may be opened for purging or draining the measuring system, or for recirculating 

product if recirculation is required in order to maintain the product in a deliverable state shall be permitted.. 

Effective means shall be provided to prevent the passage of liquid through any such outlet during normal operation of 

the measuring system and to inhibit meter indications (or advancement of indications) and recorded representations 

while the outlet is in operation.

(Amended 2002)

S.4.2. Pump-Discharge Unit. - A pump-discharge unit for liquids equipped with a flexible discharge hose shall be 

of the wet-hose type.

(Added 1993)

S.4.3. Directional Flow Valves. - If a reversal of flow could result in errors that exceed the tolerance for the 

minimum measured quantity, a valve or valves or other effective means, automatic in operation (and equipped with a 

pressure limiting device, if necessary) to prevent the reversal of flow shall be properly installed in the system. (See 

N.1.)

S.4.4. Discharge Valves. - A discharge valve may be installed on a discharge line only if the system is a wet-hose 

type. Any other shutoff valve on the discharge side of the instrument shall be of the automatic or semiautomatic 

predetermined-stop type or shall be operable only:

- by means of a tool (but not a pin) entirely separate from the device, or

- by means of a security seal with which the valve is sealed open.

S.4.5. Antidrain Means. - In a wet-hose type device, effective means shall be provided to prevent the drainage of 

the hose between transactions.

S.4.6. Other Valves. - Check valves and closing mechanisms that are not used to define the measured quantity shall 

have relief valves (if necessary) to dissipate any abnormally high pressure that may arise in the measuring assembly.

S.5. Markings. - A measuring system shall be legibly and indelibly marked with the following information:

(a) pattern approval mark (i.e., type approval number);

(b) name and address of the manufacturer or his trademark and, if required by the weights and measures authority, 

the manufacturer's identification mark in addition to the trademark;

(c) model designation or product name selected by the manufacturer;

(d) nonrepetitive serial number;

(e) the accuracy class of the meter as specified by the manufacturer consistent with Table T.2.;*

(Added 1994)

(f) maximum and minimum flow rates in pounds per unit of time;

(g) maximum working pressure;

(h) applicable range of temperature if other than -10 C to +50 C;
3.37. Mass Flow Meters

3-73

(i) minimum measured quantity; and

(j) product limitations, if applicable.

[*Nonretroactive as of January 1, 1995]

S.5.1. Marking of Gasoline Volume Equivalent Conversion Factor. - A device dispensing compressed natural gas 

shall have either the statement "1 Gasoline Liter Equivalent (GLE) is Equal to 0.678 kg of Natural Gas" or "1 

Gasoline Gallon Equivalent (GGE) is Equal to 5.660 lb of Natural Gas" permanently and conspicuously marked on 

the face of the dispenser according to the method of sale used.

(Added 1994)

S.6. Printer. - When an assembly is equipped with means for printing the measured quantity, the following conditions 

apply:

(a) the scale interval shall be the same as that of the indicator;

(b) the value of the printed quantity shall be the same value as the indicated quantity;

(c) a quantity for a delivery (other than an initial reference value) cannot be recorded until the measurement and 

delivery has been completed;

(d) the printer is returned to zero when the resettable indicator is returned to zero; and 

(e) the printed values shall meet the requirements applicable to the indicated values.

S.6.1. Printed Receipt. - Any delivered, printed quantity shall include an identification number, the time and date, 

and the name of the seller. This information may be printed by the device or pre-printed on the ticket.

S.7. Totalizers for Retail Motor-Fuel Devices.- Retail motor-fuel dispensers shall be equipped with a nonresettable 

totalizer for the quantity delivered through the metering device.

[Nonretroactive as of January 1, 1998]

(Added 1997)

N. Notes

N.1. Minimum Measured Quantity. - The minimum measured quantity shall be specified by the manufacturer.

N.2. Test Medium.

N.2.1. Liquid-Measuring Devices. - The device shall be tested with the liquid that the device is intended to measure 

or another liquid with the same general physical characteristics.

N.2.2. Vapor-Measuring Devices. - The device shall be tested with air or the product to be measured.

N.3. Test Drafts. - The minimum test shall be one test draft at the maximum flow rate of the installation and one test 

draft at the minimum flow rate. More tests may be performed at these or other flow rates. (See T.3.)

N.4. Minimum Measured Quantity. - The device shall be tested for a delivery equal to the declared minimum measured 

quantity when the device is likely to be used to make deliveries on the order of the minimum measured quantity.

N.5. Motor Fuel Dispenser. - When a device is intended for use as a liquid motor-fuel dispenser, the type evaluation test 

shall include a test for accuracy using five starts and stops during a delivery to simulate the operation of the automatic 

shut-off nozzle. This test may be conducted as part of the normal inspection and test of the meter.
3.37. Mass Flow Meters

3-74

N.6 Testing Procedures.

N.6.1. Normal Tests. - The normal test of a meter shall be made at the maximum discharge rate developed by the 

installation. Any additional tests conducted at flow rates down to and including the rated minimum discharge flow 

rate shall be considered normal tests.

(Added 1999)

N.6.1.1. Repeatability Tests. - Tests for repeatability should include a minimum of three consecutive test drafts 

of approximately the same size and be conducted under controlled conditions where variations in factors, such 

as, temperature pressure and flow rate are reduced to the extent that they will not affect the results obtained.

(Added 2001)

N.6.2. Special Tests. - Special tests to develop the operating characteristics of a meter and any special elements 

and accessories attached to or associated with the device, shall be made as circumstances require. Any test except as 

set forth in N.6.1. shall be considered a special test. Special test of a measuring system shall be made to develop 

operating characteristics of the measuring systems during a split compartment delivery. (See Table T.2.)

(Added 1999)

T. Tolerances

T.1. Tolerances, General.

(a) The tolerances apply equally to errors of underregistration and errors of overregistration.

(b) The tolerances apply to all products at all temperatures measured at any flow rate within the rated measuring 

range of the meter.

(Amended 1999)

T.2. Tolerances. - The tolerances for mass flow meters for specific liquids, gases, and applications are listed in Table 

T.2.

(Amended 1994 and 1999)

Table T.2. Accuracy Classes for Mass Flow Meter Applications

Accuracy Class Application or Commodity Being Measured Acceptance 

Tolerance

Maintenance 

Tolerance

Special 

Tolerance

0.3 Loading rack meters, vehicle-tank meters, 

home heating oil, heated products (except 

asphalt above 50 C), asphalt 50 C or 

below, milk and other food products, large 

capacity motor-fuel dispensers (maximum 

discharge flow rates greater than 100 L or 

25 gallon per minute), all other liquid 

applications not shown in the table where 

the minimum delivery is at least 700 kg 

(1500 lb)

0.2% 0.3% 0.5%

0.3A Asphalt above 50 C 0.3% 0.3% 0.5%

0.5 Small capacity (retail) motor-fuel 

dispensers, agri-chemical liquids, all other 

liquid applications not shown in the table

0.3% 0.5% 0.5%

1.0 Anhydrous ammonia, LP Gas (including 

vehicle tank meters)

0.6% 1.0% 1.0%

2.0 Compressed natural gas as a motor fuel 1.5% 2.0% 2.0%

2.5 Cryogenic liquid meters, liquefied 

compressed gases other than LP Gas

1.5% 2.5% 2.5%

(Added 1994) (Amended 1999 and 2001)
3.37. Mass Flow Meters

3-75

T.3. Repeatability. - When multiple tests are conducted at approximately the same flow rate and draft size, the range of 

the test results for the flow rate shall not exceed 40 percent of the absolute value of the maintenance tolerance and the 

results of each test shall be within the applicable tolerance. See also N.6.1.1.

(Amended 1992, 1994, and 2001)

T.4. Type Evaluation Examinations for Liquid-Measuring Devices. - For type evaluation examinations, the tolerance 

values shall apply under the following conditions:

(a) with any one liquid within the range of liquids,

(b) at any one liquid temperature and pressure within the operating range of the meter, and

(c) at all flow rates within the range of flow rates.

(Added 1993) (Amended 1994)

UR. User Requirements

UR.1. Selection Requirements.

UR.1.1. Discharge Hose-Length. - The length of the discharge hose on a retail motor-fuel device shall not exceed 

4.6 m (15 ft) unless it can be demonstrated that a longer hose is essential to permit deliveries to be made to receiving 

vehicles or vessels.

[Nonretroactive as of January 1, 1998]

(Added 1997)

UR.1.2. Minimum Measured Quantity.

(a) The minimum measured quantity shall be specified by the manufacturer. 

(b) The minimum measured quantity appropriate for a transaction may be specified by the weights and 

measures authority. A device may have a minimum measured quantity smaller than that specified by the 

weights and measures authority; however, the device must perform within the performance requirements for 

the declared minimum measured quantity.

UR.2. Installation Requirements. 

UR.2.1. Manufacturer's Instructions. - A device shall be installed in accordance with the manufacturer’s 

instructions, and the installation shall be sufficiently secure and rigid to maintain this condition.

(Added 1997)

UR.2.2. Discharge Rate.- A device shall be installed so that the actual maximum discharge rate will not exceed the 

rated maximum discharge rate. Automatic means of flow regulation shall be incorporated in the installation if 

necessary.

(Added 1997)

UR.2.3. Low-Flow Cut-Off Valve. - If a metering system is equipped with a programmable or adjustable "lowflow cut-off" feature:

(a) the low-flow cut-off value shall not be set at flow rates lower than the minimum operating flow rate 

specified by the manufacturer on the meter; and

(b) the system shall be equipped with flow control valves which prevent the flow of product and stop the 

indicator from registering product flow whenever the product flow rate is less than the low-flow cut-off 

value.

(Added 1992)
3.37. Mass Flow Meters

3-76

UR.3. Use of Device.

UR.3.1. Unit Price and Product Identity for Retail Dispensers. - The following information shall be conspicuously displayed or posted on the face of a retail dispenser used in direct sale:

(a) Except for dispensers used exclusively for fleet sales, other price contract sales, and truck refueling (e.g., 

truck stop dispensers used only to refuel trucks), all of the unit prices at which the product is offered for 

sale; and

(b) in the case of a computing type or money-operated type, the unit price at which the dispenser is set to compute.

(Added 1993)

UR.3.2. Vapor-Return Line. - During any metered delivery of liquefied petroleum gas and other liquids from a 

supplier's tank to a receiving container, there shall be no vapor-return line from the receiving container to the 

supplier's tank:

(a) in the case of any receiving container to which normal deliveries can be made without the use of such vaporreturn line, or

(b) in the case of any new receiving container when the ambient temperature is below 90 F.

(Added 1993)

UR.3.3. Ticket Printer; Customer Ticket. - Vehicle-mounted metering systems shall be equipped with a ticket 

printer which shall be used for all sales where product is delivered through the meter. A copy of the ticket issued by 

the device shall be left with the customer at the time of delivery or as otherwise specified by the customer. 

[Nonretroactive as of January 1, 1995. To become retroactive as of January 1, 1999.]

(Added 1994)

UR.3.4. Printed Ticket. - The total price, the total quantity of the delivery, and the price per unit shall be printed on 

any ticket issued by a device of the computing type and containing any one of these values.

(Added 1993)

UR.3.5. Ticket in Printing Device. - A ticket shall not be inserted into a device equipped with a ticket printer until 

immediately before a delivery is begun, and in no case shall a ticket be in the device when the vehicle is in motion 

while on a public street, highway, or thoroughfare.

(Added 1993)

UR.3.6. Steps After Dispensing. - After delivery to a customer from a retail motor-fuel device:

(a) the starting lever shall be returned to its shutoff position and the zero-set-back interlock engaged; and

(b) the discharge nozzle shall be returned to its designed hanging position unless the primary indicating 

elements, and recording elements, if the device is equipped and activated to record, have been returned to a 

definite zero indication.

(Added 1993)

UR.3.7. Return of Indicating and Recording Elements to Zero. - The primary indicating elements (visual), and 

the primary recording elements when these are returnable to zero, shall be returned to zero immediately before each 

delivery. Exceptions to this requirement are totalizers on key-lock-operated or other self-operated dispensers and the 

primary recording element if the device is equipped to record.

(Added 1995) (Amended 1997)

UR.3.8. Return of Product to Storage, Retail Compressed Natural Gas Dispensers.- Provisions at the site shall 

be made for returning product to storage or disposing of the product in a safe and timely manner during or following 

testing operations. Such provisions may include return lines, or cylinders adequate in size and number to permit this 

procedure.

(Added 1998)
3.38. Carbon Dioxide Liquid-Measuring Devices

3-77

Section 3.38. Carbon Dioxide1

Liquid-Measuring Devices 

A. Application

A.1. This code applies to carbon dioxide liquid-measuring devices used for the measurement of liquid carbon dioxide.

A.2. This code does not apply to devices used solely for dispensing a product in connection with operations in which the 

amount dispensed does not affect customer charges.

A.3. See also, Sec. 1.10; General Code requirements.

S. Specifications

S.1. Design of Indicating and Recording Elements and of Recorded Representations. 

S.1.1. Primary Elements. -

S.1.1.1. General. - A device shall be equipped with a primary indicating element and may also be equipped 

with a primary recording element.

S.1.1.2. Units. - A device shall indicate and record, if equipped to record, its deliveries in terms of pounds or 

kilograms or decimal subdivisions or multiples thereof.

S.1.1.3. Value of Smallest Unit. - The value of the smallest unit of indicated delivery, and recorded delivery, if 

the device is equipped to record, shall not exceed the equivalent of:

(a) for small delivery devices:

(1) 1 kilogram, or

(2) 1 pound 

(b) for large delivery devices:

(1) 10 kilograms , or

(2) 10 pounds

S.1.1.4. Advancement of Indicating and Recording Elements. - Primary indicating and recording elements 

shall be susceptible to advancement only by the normal operation of the device. However, a device may be 

cleared by advancing its elements to zero, but only if:

(a) the advancing movement, once started, cannot be stopped until zero is reached, or

(b) in the case of indicating elements only, such elements are automatically obscured until the elements 

reach the correct zero position.

S.1.1.5. Return to Zero. - Primary indicating and recording elements shall be readily returnable to a definite 

zero indication. Means shall be provided to prevent the return of primary indicating elements and of primary 

recording elements beyond their correct zero position.

S.1.2. Graduations. -

S.1.2.1. Length. - Graduations shall be so varied in length that they may be conveniently read.

 1 The Carbon Dioxide Liquid-Measuring Devices Code was updated from a tentative code to a permanent code in 2002, 

effective January 1, 2003.
3.38. Carbon Dioxide Liquid-Measuring Devices

3-78

S.1.2.2. Width. - In any series of graduations, the width of a graduation shall in no case be greater than the 

width of the minimum clear interval between graduations. The width of main graduations shall be not more than 

50 percent greater than the width of subordinate graduations. Graduations shall in no case be less than 0.2 mm 

(0.008 in) in width.

S.1.2.3. Clear Interval Between Graduations. - The clear interval shall be not less than 1.0 mm (0.04 in). If 

the graduations are not parallel, the measurement shall be made:

(a) along the line of relative movement between the graduations at the end of the indicator, or

(b) if the indicator is continuous, at the point of widest separation of the graduations.

(See also S.1.3.6.)

S.1.3. Indicators. -

S.1.3.1. Symmetry. - The index of an indicator shall be of the same shape as the graduations at least throughout 

that portion of its length associated with the graduations.

S.1.3.2. Length. - The index of an indicator shall reach to the finest graduations with which it is used, unless 

the indicator and the graduations are in the same plane, in which case the distance between the end of the 

indicator and the ends of the graduations, measured along the line of the graduations, shall be not more than 1.0 

mm (0.04 in).

S.1.3.3. Width. - The width of the index of the indicator in relation to the series of graduations with which it is 

used shall be not greater than:

(a) the width of the narrowest graduation*, and

[*Nonretroactive as of January 1, 2002]

(Amended 2001)

(b) the width of the minimum clear interval between graduations.

When the index of an indicator extends along the entire length of a graduation, that portion of the index of the 

indicator that may be brought into coincidence with the graduation shall be of the same width throughout the 

length of the index that coincides with the graduation.

S.1.3.4. Clearance. - The clearance between the index of an indicator and the graduations shall in no case be 

more than 1.5 mm (0.06 in).

S.1.3.5. Parallax. - Parallax effects shall be reduced to the practicable minimum.

S.1.3.6. Travel of Indicator. - If the most sensitive element of the primary indicating element utilizes an 

indicator and graduations, the relative movement of these parts corresponding to the smallest indicated value 

shall be no less than 5 mm (0.20 in).

S.1.4. Computing-Type Devices. -

S.1.4.1. Printed Ticket. - Any printed ticket issued by a device of the computing type on which there is printed 

the total computed price shall have printed clearly thereon also the total quantity of the delivery and the price per 

unit.

S.1.4.2. Money-Value Computations. - Money-value computations shall be of the full-computing type in 

which the money value at a single unit price, or at each of a series of unit prices, shall be computed for every 

delivery within either the range of measurement of the device or the range of the computing elements, whichever 

is less.
3.38. Carbon Dioxide Liquid-Measuring Devices

3-79

The total price shall be computed on the basis of the quantity indicated when the value of the smallest division 

indicated is equal to or less than the value specified in S.1.1.3.

S.1.4.3. Money-Values, Mathematical Agreement. - Any digital money-value indication and any recorded 

money value on a computing-type device shall be in mathematical agreement with its associated quantity 

indication or representation to within one cent of money value.

S.2. Design of Measuring Elements.

S.2.1. Vapor Elimination. - A measuring system shall be equipped with an effective vapor eliminator or other 

effective means to prevent the measurement of vapor that will cause errors in excess of the applicable tolerances.

S.2.2. Reverse Flow Measurement. - Effective means, automatic in operation, shall be installed to prevent reverse 

flow measurement. 

S.2.3. Maintenance of Liquid State. - A device shall be so designed that the product being measured will remain in 

a liquid state during passage through the device.

S.2.4. Automatic Temperature or Density Compensation. - A volumetric device shall be equipped with automatic 

means for adjusting the indication and recorded representation of the measured quantity of the product to indicate or 

record the quantity of the product measured in terms of pounds.

S.2.5. Provision for Sealing. - Adequate provision shall be made for applying security seals in such a manner that 

no adjustment or interchange may be made of:

(a) any measurement element,

(b) any adjustable element for controlling delivery rate when such rate tends to affect the accuracy of deliveries, 

and

(c) any automatic temperature or density compensating system.

Any adjusting mechanism shall be readily accessible for purposes of affixing a security seal.

S.3. Design of Discharge Lines and Discharge Line Valves.

S.3.1. Diversion of Measured Liquid. - No means shall be provided by which any measured liquid can be diverted 

from the measuring chamber of the device or the discharge line therefrom, except that a manually controlled outlet 

that may be opened for purging or draining the measuring system shall be permitted. Effective means shall be 

provided to prevent the passage of liquid through any such outlet during normal operation of the device and to 

indicate clearly and unmistakably when the valve controls are so set as to permit passage of liquid through such 

outlet.

S.3.2. Discharge Hose. - The discharge hose of a measuring system shall be of a wet hose type with a shutoff valve 

at its outlet end.

S.4. Marking Requirements.

S.4.1. Limitation of Use . - If a measuring system is intended to measure accurately only liquids having particular 

properties, or to measure accurately only under specific installation or operating conditions, or to measure accurately 

only when used in conjunction with specific accessory equipment, these limitations shall be clearly and permanently 

marked on the device.

S.4.2. Discharge Rates. - A meter shall be marked to show its designed maximum and minimum discharge rates. 

The marked minimum discharge rate shall not exceed 20 percent of the maximum discharge rate.
3.38. Carbon Dioxide Liquid-Measuring Devices

3-80

S.5. Level Condition, On-Board Weighing Systems. - Provision shall be made for automatically inhibiting the 

delivery of liquid carbon dioxide when the vehicle is out of level beyond the limit required for the performance to be 

within the applicable tolerances.

N. Notes

N.1. Test Liquid. - The test liquid shall be carbon dioxide in a compressed liquid state.

N.2. Vaporization and Volume Change. - Care shall be exercised to reduce vaporization and volume changes to a 

minimum. When testing by weight, the weigh tank and transfer systems shall be pre-cooled to liquid temperature prior to 

the start of the test to avoid the venting of vapor from the vessel being weighed.

N.3. Test Drafts.

N.3.1. Gravimetric Test. - Weight test drafts shall be equal to at least the amount delivered by the device in two 

minutes at its maximum discharge rate.

N.3.2. Transfer Standard Test. - When comparing a meter with a calibrated transfer standard, the test draft shall 

be equal to at least the amount delivered by the device in two minutes at its maximum discharge rate.

N.3.3. Volumetric Prover Test Drafts. - Test drafts shall be equal to at least the amount delivered in one minute at 

normal discharge rate.

N.4. Testing Procedures.

N.4.1. Normal Tests. - The "normal" test of a device shall be made at the maximum discharge flow rate developed 

under the conditions of installation. Any additional tests conducted at flow rates down to and including one-half of 

the sum of the maximum discharge flow rate and the rated minimum discharge flow rate shall be considered normal 

tests.

N.4.1.1. Repeatability Tests. – Tests for repeatability should include a minimum of three consecutive test drafts 

of approximately the same size and be conducted under controlled conditions where variations in factors, such as 

temperature, pressure, and flow rate are reduced to the extent that they will not affect the results obtained.

(Added 2002)

N.4.2. Special Tests. - Any test except as set forth in N.4.1. shall be considered a special test. Tests shall be 

conducted, if possible, to evaluate any special elements or accessories attached to or associated with the device. A 

device shall be tested at a minimum discharge rate of:

(a) not less than the minimum rated capacity or 20 percent of the maximum rated discharge rate of the device, 

whichever is less, or

(b) the lowest discharge rate practicable under the conditions of installation.

"Special" tests may be conducted to develop any characteristics of the device anticipated under the conditions of 

installation as circumstances require.

N.4.3. Density. - Temperature and pressure of the metered test liquid shall be measured during the test for the 

determination of density or volume correction when applicable. The appropriate correction values shall apply as 

specified in Table 1.

N.4.4. Automatic Temperature or Density Compensation. - If a device is equipped with an automatic temperature 

or density compensator, the compensator shall be tested by comparing the quantity indicated or recorded by the 

device (with the compensator connected and operating) with the actual delivered quantity. The appropriate 

correction values shall apply as specified in Table 1.
3.38. Carbon Dioxide Liquid-Measuring Devices

3-81

T. Tolerances

T.1. Application.

T.1.1. To Underregistration and to Overregistration. - The tolerances hereinafter prescribed shall be applied to 

errors of underregistration and errors of overregistration.

T.2. Tolerance Values.

T.2.1. On Normal Tests. - The maintenance tolerance on "normal" tests shall be two and one-half percent (2.5%) of 

the indicated quantity. The acceptance tolerances shall be one and one-half percent (1.5%) of the indicated quantity.

T.2.2. On Special Tests. - The maintenance and acceptance tolerance on "special" tests shall be two and one-half 

percent (2.5%) of the indicated quantity.

T.2.3. Repeatability. – When multiple tests are conducted at approximately the same flow rate and draft size, the 

range of the test results for the flow rate shall not exceed 40 percent of the absolute value of the maintenance 

tolerance and the results of each test shall be within the applicable tolerance. See also N.4.1.1.

(Added 2002)

T.3. On Tests Using Transfer Standards. - To the basic tolerance values that would otherwise be applied, there shall be 

added an amount equal to two times the standard deviation of the applicable transfer standard when compared to a basic 

reference standard.

UR. User Requirements

UR.1. Installation Requirements.

UR.1.1. Discharge Rate. - A device shall be so installed that the actual maximum discharge rate will not exceed the 

rated maximum discharge rate. If necessary, means for flow regulation shall be incorporated in the installation.

UR.1.2. Length of Discharge Hose. - The discharge hose shall be of such a length and design as to keep 

vaporization of the liquid to a minimum.

UR.1.3. Maintenance of Liquid State. - A device shall be so installed and operated that the product being 

measured shall remain in the liquid state during passage through the meter.

UR.2. Use Requirements.

UR.2.1. Return of Indicating and Recording Elements to Zero. - The primary indicating elements (visual) and 

the primary recording elements shall be returned to zero immediately before each delivery.

UR.2.2. Condition of Discharge System. - The discharge hose, up to the valve at the end of the discharge hose, 

shall be completely filled and precooled to liquid temperatures before a "zero" condition is established and prior to 

the start of a commercial delivery. Means shall be provided to fill the discharge hose with liquid prior to the start of a 

delivery.

UR.2.3. Vapor Equalization Line. - A vapor equalization line shall not be used during a metered delivery unless 

the quantity of vapor displaced from the buyer's tank to the seller's tank is deducted from the metered quantity. The 

appropriate correction values shall apply as specified in Table 2.

UR.2.4. Temperature or Density Compensation.

UR.2.4.1. Use of Automatic Temperature or Density Compensators. - Devices equipped with an automatic 

temperature or density compensator shall have the compensator connected, operable, and in use at all times. 

Such automatic temperature or density compensator may not be removed.
3.38. Carbon Dioxide Liquid-Measuring Devices

3-82

UR.2.4.2. Tickets or Invoices. - Any written invoice or printed ticket based on a reading of a device that is 

equipped with an automatic temperature or density compensator shall have shown thereon that the quantity 

delivered has been temperature or density compensated.

UR.2.5. Ticket in Printing Device. - A ticket shall not be inserted into a device equipped with a ticket printer until 

immediately before a delivery is begun, and in no case shall a ticket be in the device when the vehicle is in motion 

while on a public street, highway, or thoroughfare.

UR.2.6. Sale by Weight. - All quantity determinations shall be made by means of an approved and sealed weighing or 

measuring device. All sales shall be stated in kilograms or pounds.

D. Definitions

The terms defined here have a special and technical meaning when used in the Code for Carbon Dioxide LiquidMeasuring Devices.

automatic temperature or density compensation. The use of integrated or ancillary equipment to obtain, from the 

output of a volumetric meter, an equivalent mass indication.

carbon dioxide liquid-measuring device. A system including a mechanism or machine of (a) the meter or (b) a 

weighing type of device mounted on a vehicle designed to measure and deliver liquid carbon dioxide. Means may be 

provided to indicate automatically, for one of a series of unit prices, the total money value of the quantity measured.

large-delivery devices. Devices used primarily for single deliveries greater than 1000 pounds or 500 kilograms.

small-delivery device. Any device other than a large-delivery device.

transfer standard. A measurement system designed for use in proving and testing carbon dioxide liquid-measuring 

devices.

vapor equalization credit. The quantity deducted from the metered quantity of liquid carbon dioxide when a vapor 

equalizing line is used to facilitate the transfer of liquid during a metered delivery.

vapor equalization line. A hose or pipe connected from the vapor space of the seller's tank to the vapor space of the 

buyer's tank that is used to equalize the pressure during a delivery.

wet-hose type. A type of device in which it is intended that the discharge hose be completely filled prior to each 

commercial delivery.
3.38. Carbon Dioxide Liquid-Measuring Devices

3-83

Table 1.

Temp

 F

Pressure Liquid Density Vapor Density Vapor 

Displacement

% PSIA PSIG lb/gal (lb-oz)/gal lb/cu ft lb/gal

- 30.00 177.89 163.19 9.127 9 - 2.0 1.989 0.266 2.9

- 29.75 178.75 164.05 9.122 9 - 2.0 1.999 0.267 2.9

- 29.50 179.62 164.92 9.117 9 - 1.9 2.008 0.268 2.9

- 29.25 180.49 165.79 9.113 9 - 1.8 2.018 0.270 3.0

- 29.00 181.36 166.67 9.108 9 - 1.7 2.028 0.271 3.0

- 28.75 182.24 167.54 9.103 9 - 1.7 2.038 0.272 3.0

- 28.50 183.12 168.42 9.098 9 - 1.6 2.048 0.274 3.0

- 28.25 184.00 169.31 9.094 9 - 1.5 2.058 0.275 3.0

- 28.00 184.89 170.19 9.089 9 - 1.4 2.067 0.276 3.0

- 27.75 185.78 171.08 9.084 9 - 1.3 2.077 0.278 3.1

- 27.50 186.67 171.98 9.080 9 - 1.3 2.087 0.279 3.1

- 27.25 187.57 172.87 9.075 9 - 1.2 2.098 0.280 3.1

- 27.00 188.47 173.77 9.070 9 - 1.1 2.108 0.282 3.1

- 26.75 189.37 174.67 9.065 9 - 1.0 2.118 0.283 3.1

- 26.50 190.28 175.58 9.061 9 - 1.0 2.128 0.284 3.1

- 26.25 191.18 176.49 9.056 9 - 0.9 2.138 0.286 3.2

- 26.00 192.10 177.40 9.051 9 - 0.8 2.148 0.287 3.2

- 25.75 193.01 178.32 9.046 9 - 0.7 2.159 0.289 3.2

- 25.50 193.93 179.23 9.041 9 - 0.7 2.169 0.290 3.2

- 25.25 194.85 180.16 9.037 9 - 0.6 2.179 0.291 3.2

- 25.00 195.78 181.08 9.032 9 - 0.5 2.190 0.293 3.2

- 24.75 196.70 182.01 9.027 9 - 0.4 2.200 0.294 3.3

- 24.50 197.64 182.94 9.022 9 - 0.4 2.211 0.296 3.3

- 24.25 198.57 183.87 9.017 9 - 0.3 2.221 0.297 3.3

- 24.00 199.51 184.81 9.013 9 - 0.2 2.232 0.298 3.3

- 23.75 200.45 185.75 9.008 9 - 0.1 2.243 0.300 3.3

- 23.50 201.39 186.70 9.003 9 - 0.0 2.253 0.301 3.3
3.38. Carbon Dioxide Liquid-Measuring Devices

3-84

Table 1.

Temp

 F Pressure Liquid Density Vapor Density

Vapor 

Displacement

%

PSIA PSIG lb/gal (lb-oz)/gal lb/cu ft lb/gal

- 23.25 202.34 187.64 8.998 9 - 0.0 2.264 0.303 3.4

- 23.00 203.29 188.60 8.993 8 - 15.9 2.275 0.304 3.4

- 22.75 204.25 189.55 8.989 8 - 15.8 2.286 0.306 3.4

- 22.50 205.20 190.51 8.984 8 - 15.7 2.296 0.307 3.4

- 22.25 206.16 191.47 8.979 8 - 15.7 2.307 0.308 3.4

- 22.00 207.13 192.43 8.974 8 - 15.6 2.318 0.310 3.5

- 21.75 208.09 193.40 8.969 8 - 15.5 2.329 0.311 3.5

- 21.50 209.06 194.37 8.964 8 - 15.4 2.340 0.313 3.5

- 21.25 210.04 195.34 8.959 8 - 15.4 2.351 0.314 3.5

- 21.00 211.02 196.32 8.955 8 - 15.3 2.362 0.316 3.5

- 20.75 212.00 197.30 8.950 8 - 15.2 2.374 0.317 3.5

- 20.50 212.98 198.28 8.945 8 - 15.1 2.385 0.319 3.6

- 20.25 213.97 199.27 8.940 8 - 15.0 2.396 0.320 3.6

- 20.00 214.96 200.26 8.935 8 - 15.0 2.407 0.322 3.6

- 19.75 215.95 201.26 8.930 8 - 14.9 2.419 0.323 3.6

- 19.50 216.95 202.25 8.925 8 - 14.8 2.430 0.325 3.6

- 19.25 217.95 203.25 8.920 8 - 14.7 2.441 0.326 3.7

- 19.00 218.95 204.26 8.915 8 - 14.6 2.453 0.328 3.7

- 18.75 219.96 205.27 8.911 8 - 14.6 2.464 0.329 3.7

- 18.50 220.97 206.28 8.906 8 - 14.5 2.476 0.331 3.7

- 18.25 221.99 207.29 8.901 8 - 14.4 2.488 0.333 3.7

- 18.00 223.01 208.31 8.896 8 - 14.3 2.499 0.334 3.8

- 17.75 224.03 209.33 8.891 8 - 14.3 2.511 0.336 3.8

- 17.50 225.05 210.36 8.886 8 - 14.2 2.523 0.337 3.8

- 17.25 226.08 211.38 8.881 8 - 14.1 2.534 0.339 3.8

- 17.00 227.11 212.42 8.876 8 - 14.0 2.546 0.340 3.8

- 16.75 228.15 213.45 8.871 8 - 13.9 2.558 0.342 3.9

- 16.50 229.18 214.49 8.866 8 - 13.9 2.570 0.344 3.9
3.38. Carbon Dioxide Liquid-Measuring Devices

3-85

Table 1.

Temp

 F

Pressure Liquid Density Vapor Density Vapor 

Displacement

% PSIA PSIG lb/gal (lb-oz)/gal lb/cu ft lb/gal

- 16.25 230.23 215.53 8.861 8 - 13.8 2.582 0.345 3.9

- 16.00 231.27 216.58 8.856 8 - 13.7 2.594 0.347 3.9

- 15.75 232.32 217.62 8.851 8 - 13.6 2.606 0.348 3.9

- 15.50 233.37 218.68 8.846 8 - 13.5 2.618 0.350 4.0

- 15.25 234.43 219.73 8.841 8 - 13.5 2.630 0.352 4.0

- 15.00 235.49 220.79 8.836 8 - 13.4 2.643 0.353 4.0

- 14.75 236.55 221.86 8.831 8 - 13.3 2.655 0.355 4.0

- 14.50 237.62 222.92 8.826 8 - 13.2 2.667 0.357 4.0

- 14.25 238.69 223.99 8.821 8 - 13.1 2.680 0.358 4.1

- 14.00 239.76 225.07 8.816 8 - 13.1 2.692 0.360 4.1

- 13.75 240.84 226.14 8.811 8 - 13.0 2.704 0.362 4.1

- 13.50 241.92 227.22 8.806 8 - 12.9 2.717 0.363 4.1

- 13.25 243.00 228.31 8.801 8 - 12.8 2.729 0.365 4.1

- 13.00 244.09 229.39 8.796 8 - 12.7 2.742 0.367 4.2

- 12.75 245.18 230.49 8.791 8 - 12.7 2.755 0.368 4.2

- 12.50 246.28 231.58 8.786 8 - 12.6 2.767 0.370 4.2

- 12.25 247.37 232.68 8.781 8 - 12.5 2.780 0.372 4.2

- 12.00 248.48 233.78 8.776 8 - 12.4 2.793 0.373 4.3

- 11.75 249.58 234.89 8.771 8 - 12.3 2.806 0.375 4.3

- 11.50 250.69 236.00 8.765 8 - 12.2 2.819 0.377 4.3

- 11.25 251.80 237.11 8.760 8 - 12.2 2.832 0.379 4.3

- 11.00 252.92 238.22 8.755 8 - 12.1 2.845 0.380 4.3

- 10.75 254.04 239.34 8.750 8 - 12.0 2.858 0.382 4.4

- 10.50 255.16 240.47 8.745 8 - 11.9 2.871 0.384 4.4

- 10.25 256.29 241.60 8.740 8 - 11.8 2.884 0.386 4.4

- 10.00 257.42 242.73 8.735 8 - 11.8 2.897 0.387 4.4

- 9.75 258.56 243.86 8.730 8 - 11.7 2.911 0.389 4.5

- 9.50 259.70 245.00 8.725 8 - 11.6 2.924 0.391 4.5
3.38. Carbon Dioxide Liquid-Measuring Devices

3-86

Table 1.

Temp

 F

Pressure Liquid Density Vapor Density Vapor 

Displacement

% PSIA PSIG lb/gal (lb-oz)/gal lb/cu ft lb/gal

- 9.25 260.84 246.14 8.719 8 - 11.5 2.937 0.393 4.5

- 9.00 261.98 247.29 8.714 8 - 11.4 2.951 0.394 4.5

- 8.75 263.13 248.44 8.709 8 - 11.3 2.964 0.396 4.5

- 8.50 264.29 249.59 8.704 8 - 11.3 2.978 0.398 4.6

- 8.25 265.44 250.75 8.699 8 - 11.2 2.991 0.400 4.6

- 8.00 266.60 251.91 8.694 8 - 11.1 3.005 0.402 4.6

- 7.75 267.77 253.07 8.688 8 - 11.0 3.019 0.404 4.6

- 7.50 268.93 254.24 8.683 8 - 10.9 3.032 0.405 4.7

- 7.25 270.11 255.41 8.678 8 - 10.8 3.046 0.407 4.7

- 7.00 271.28 256.59 8.673 8 - 10.8 3.060 0.409 4.7

- 6.75 272.46 257.76 8.668 8 - 10.7 3.074 0.411 4.7

- 6.50 273.64 258.95 8.662 8 - 10.6 3.088 0.413 4.8

- 6.25 274.83 260.13 8.657 8 - 10.5 3.102 0.415 4.8

- 6.00 276.02 261.32 8.652 8 - 10.4 3.116 0.417 4.8

- 5.75 277.21 262.52 8.647 8 - 10.3 3.130 0.418 4.8

- 5.50 278.41 263.72 8.641 8 - 10.3 3.144 0.420 4.9

- 5.25 279.61 264.92 8.636 8 - 10.2 3.159 0.422 4.9

- 5.00 280.82 266.12 8.631 8 - 10.1 3.173 0.424 4.9

- 4.75 282.03 267.33 8.626 8 - 10.0 3.187 0.426 4.9

- 4.50 283.24 268.55 8.620 8 - 9.9 3.202 0.428 5.0

- 4.25 284.46 269.76 8.615 8- 9.8 3.216 0.430 5.0

- 4.00 285.68 270.98 8.610 8 - 9.8 3.231 0.432 5.0

- 3.75 286.90 272.21 8.604 8 - 9.7 3.245 0.434 5.0

- 3.50 288.13 273.44 8.599 8 - 9.6 3.260 0.436 5.1

- 3.25 289.37 274.67 8.594 8 - 9.5 3.275 0.438 5.1

- 3.00 290.60 275.91 8.589 8 - 9.4 3.289 0.440 5.1

- 2.75 291.84 277.15 8.583 8 - 9.3 3.304 0.442 5.1

- 2.50 293.09 278.39 8.578 8 - 9.2 3.319 0.444 5.2
3.38. Carbon Dioxide Liquid-Measuring Devices

3-87

Table 1.

Temp

 F

Pressure Liquid Density Vapor Density Vapor 

Displacement

% PSIA PSIG lb/gal (lb-oz)/gal lb/cu ft lb/gal

- 2.25 294.33 279.64 8.573 8 - 9.2 3.334 0.446 5.2

- 2.00 295.58 280.89 8.567 8 - 9.1 3.349 0.448 5.2

- 1.75 296.84 282.14 8.562 8 - 9.0 3.364 0.450 5.3

- 1.50 298.10 283.40 8.556 8 - 8.9 3.379 0.452 5.3

- 1.25 299.36 284.67 8.551 8 - 8.8 3.395 0.454 5.3

- 1.00 300.63 285.93 8.546 8 - 8.7 3.410 0.456 5.3

- 0.75 301.90 287.21 8.540 8 - 8.6 3.425 0.458 5.4

- 0.50 303.18 288.48 8.535 8 - 8.6 3.440 0.460 5.4

- 0.25 304.46 289.76 8.530 8 - 8.5 3.456 0.462 5.4

0.00 305.74 291.74 8.524 8 - 8.4 3.471 0.464 5.4

0.25 307.03 292.33 8.519 8 - 8.3 3.487 0.466 5.5

0.50 308.32 293.62 8.513 8 - 8.2 3.503 0.468 5.5

0.75 309.61 294.92 8.508 8 - 8.1 3.518 0.470 5.5

1.00 310.91 296.21 8.502 8 - 8.0 3.534 0.472 5.6

1.25 312.21 297.52 8.497 8 - 8.0 3.550 0.475 5.6

1.50 313.52 298.82 8.491 8 - 7.9 3.566 0.477 5.6

1.75 314.83 300.13 8.486 8 - 7.8 3.582 0.479 5.6

2.00 316.15 301.45 8.480 8-7.7 3.598 0.481 5.7

2.25 317.46 302.77 8.475 8 - 7.6 3.614 0.483 5.7

2.50 318.79 304.09 8.469 8 - 7.5 3.630 0.485 5.7

2.75 320.11 305.42 8.464 8 - 7.4 3.646 0.487 5.8

3.00 321.45 306.75 8.458 8 - 7.3 3.662 0.490 5.8

3.25 322.78 308.08 8.453 8 - 7.2 3.679 0.492 5.8

3.50 324.12 309.42 8.447 8 - 7.2 3.695 0.494 5.8

3.75 325.46 310.77 8.442 8 - 7.1 3.712 0.496 5.9

4.00 326.81 312.11 8.436 8 - 7.0 3.728 0.498 5.9

4.25 328.16 313.46 8.431 8 - 6.9 3.745 0.501 5.9

4.50 329.52 314.82 8.425 8 - 6.8 3.761 0.503 6.0
3.38. Carbon Dioxide Liquid-Measuring Devices

3-88

Table 1.

Temp

 F

Pressure Liquid Density Vapor Density Vapor 

Displacement

% PSIA PSIG lb/gal (lb-oz)/gal lb/cu ft lb/gal

4.75 330.88 316.18 8.420 8 - 6.7 3.778 0.505 6.0

5.00 332.24 317.54 8.414 8 - 6.6 3.795 0.507 6.0

5.25 333.61 318.91 8.408 8 - 6.5 3.812 0.510 6.1

5.50 334.98 320.28 8.403 8 - 6.4 3.829 0.512 6.1

5.75 336.35 321.66 8.397 8 - 6.4 3.846 0.514 6.1

6.00 337.73 323.04 8.392 8 - 6.3 3.863 0.516 6.2

6.25 339.12 324.42 8.386 8 - 6.2 3.880 0.519 6.2

6.50 340.51 325.81 8.380 8 - 6.1 3.897 0.521 6.2

6.75 341.90 327.20 8.375 8 - 6.0 3.915 0.523 6.3

7.00 343.30 328.60 8.369 8 - 5.9 3.932 0.526 6.3

7.25 344.70 330.00 8.363 8 - 5.8 3.949 0.528 6.3

7.50 346.10 331.41 8.358 8 - 5.7 3.967 0.530 6.3

7.75 347.51 332.82 8.352 8 - 5.6 3.984 0.533 6.4

8.00 348.92 334.23 8.346 8 - 5.5 4.002 0.535 6.4

8.25 350.34 335.65 8.341 8 - 5.4 4.020 0.537 6.4

8.50 351.76 337.07 8.335 8 - 5.4 4.038 0.540 6.5

8.75 353.19 338.49 8.335 8-5.4 4.038 0.540 6.5

9.00 354.62 339.92 8.323 8 - 5.2 4.073 0.545 6.5

9.25 356.06 341.36 8.318 8 - 5.1 4.091 0.547 6.6

9.50 357.49 342.80 8.312 8 - 5.0 4.110 0.549 6.6

9.75 358.94 344.24 8.306 8 - 4.9 4.128 0.552 6.6

10.00 360.38 345.69 8.300 8 - 4.8 4.146 0.554 6.7

10.25 361.84 347.14 8.295 8 - 4.7 4.164 0.557 6.7

10.50 363.29 348.60 8.289 8 - 4.6 4.183 0.559 6.7

10.75 364.75 350.06 8.283 8 - 4.5 4.201 0.562 6.8

11.00 366.22 351.52 8.277 8 - 4.4 4.220 0.564 6.8

11.25 367.68 352.99 8.271 8 - 4.3 4.238 0.567 6.8
3.38. Carbon Dioxide Liquid-Measuring Devices

3-89

Table 1.

Temp

 F

Pressure Liquid Density Vapor Density Vapor 

Displacement

% PSIA PSIG lb/gal (lb-oz)/gal lb/cu ft lb/gal

11.50 369.16 354.46 8.266 8 - 4.2 4.257 0.569 6.9

11.75 370.64 355.94 8.260 8 - 4.2 4.276 0.572 6.9

12.00 372.12 357.42 8.254 8 - 4.1 4.295 0.574 7.0

12.25 373.60 358.91 8.248 8 - 4.0 4.314 0.577 7.0

12.50 375.09 360.40 8.242 8 - 3.9 4.333 0.579 7.0

12.75 376.59 361.89 8.236 8 - 3.8 4.352 0.582 7.1

13.00 378.09 363.39 8.230 8 - 3.7 4.371 0.584 7.1

13.25 379.59 364.89 8.224 8 - 3.6 4.390 0.587 7.1

13.50 381.10 366.40 8.219 8 - 3.5 4.410 0.589 7.2

13.75 382.61 367.91 8.213 8 - 3.4 4.429 0.592 7.2

14.00 384.13 369.43 8.207 8 - 3.3 4.449 0.595 7.2

14.25 385.65 370.95 8.201 8 - 3.2 4.468 0.597 7.3

14.50 387.17 372.48 8.195 8 - 3.1 4.488 0.600 7.3

14.75 388.70 374.01 8.189 8 - 3.0 4.508 0.603 7.4

15.00 390.24 375.54 8.183 8 - 2.9 4.527 0.605 7.4

15.25 391.78 377.08 8.177 8 - 2.8 4.547 0.608 7.4

15.50 393.32 378.62 8.171 8 - 2.7 4.567 0.611 7.5

15.75 394.87 380.17 8.165 8 - 2.6 4.587 0.613 7.5

16.00 396.42 381.72 8.159 8 - 2.5 4.608 0.616 7.5

16.25 397.98 383.28 8.153 8 - 2.4 4.628 0.619 7.6

16.50 399.54 384.84 8.147 8 - 2.3 4.648 0.621 7.6

16.75 401.10 386.41 8.141 8 - 2.2 4.669 0.624 7.7

17.00 402.67 387.98 8.134 8 - 2.2 4.689 0.627 7.7

17.25 404.25 389.55 8.128 8 - 2.1 4.710 0.630 7.7

17.50 405.82 391.13 8.122 8 - 2.0 4.731 0.632 7.8

17.75 407.41 392.71 8.116 8 - 1.9 4.751 0.635 7.8

18.00 409.00 394.30 8.110 8 - 1.8 4.772 0.638 7.9
3.38. Carbon Dioxide Liquid-Measuring Devices

3-90

Table 1.

Temp

 F

Pressure Liquid Density Vapor Density Vapor 

Displacement

% PSIA PSIG lb/gal (lb-oz)/gal lb/cu ft lb/gal

18.25 410.59 395.89 8.104 8 - 1.7 4.793 0.641 7.9

18.50 412.19 397.49 8.098 8 - 1.6 4.814 0.644 7.9

18.75 413.79 399.09 8.092 8 - 1.5 4.835 0.646 8.0

19.00 415.39 400.70 8.085 8 - 1.4 4.857 0.649 8.0

19.25 417.00 402.31 8.079 8 - 1.3 4.878 0.652 8.1

19.50 418.62 403.92 8.073 8 - 1.2 4.900 0.655 8.1

19.75 420.24 405.54 8.067 8 - 1.1 4.921 0.658 8.2

20.00 421.86 407.17 8.061 8 - 1.0 4.943 0.661 8.2
4-1

SECTION 4

Page

4.40. Vehicle Tanks Used as Measures 4-3

4.41. Liquid Measures 4-7

4.42. Farm Milk Tanks 4-9

4.43. Measure-Containers 4-15

4.44. Graduates 4-19

4.45. Dry Measures 4-23

4.46. Berry Baskets and Boxes 4-25
4-2
4.40. Vehicle Tanks Used as Measures

4-3

Sec. 4.40. Vehicle Tanks Used as Measures

A. Application

A.1. - This code applies to vehicle tanks when these are used as commercial measures.

A.2. - This code does not apply to the following devices:

(a) Devices used solely for dispensing a product in connection with operations in which the amount dispensed does 

not affect customer charges.

(b) Meters mounted on vehicle tanks (for which see Sec. 3.31; Code for Vehicle-Tank Meters).

A.3. - Also see Sec. 1.10; General Code requirements.

S. Specifications

S.1. Design of Compartments.

S.1.1. Compartment Distortion. - The shell and bulkheads of a vehicle tank shall be so constructed that under any 

condition of liquid lading they will not become distorted sufficiently to cause a change in the capacity of any 

compartment (as determined by volumetric test) equal to more than 0.25 L per 750 L (0.5 pt per 200 gal), or fraction 

thereof, of the nominal compartment capacity, or to more than 0.5 L (1 pt), whichever is greater. (This specification 

prescribes a limit on permissible distortion only, and is not to be construed as setting up a secondary tolerance on 

compartment capacities to be added to the values given in tolerance paragraph T.2.)

S.1.2. Venting. - During filling operations, effective venting of a compartment shall be provided to permit air to 

escape from all spaces designed to be filled with liquid and to permit the influx of air to the compartment during the 

discharge of liquid therefrom. Venting shall prevent any formation of air pockets.

S.1.3. Completeness of Delivery. - A tank shall be so constructed that, when it is standing on a level surface, 

complete delivery can be made from any compartment through its delivery faucet or valve whether other 

compartments are full or empty, and whether or not the delivery is through a manifold.

S.1.4. Fill or Inspection Opening. - The fill or inspection opening of a compartment shall be of such size and 

location that it can readily be determined by visual inspection that the compartment has been properly filled or 

completely emptied and shall be so positioned with respect to the ends of the compartment that the indicator may be 

positioned as required. In no case shall the opening, if circular, have a diameter of less than 20 cm (7-5/8 in), or, if 

other than circular, have an effective area of less than 290 cm2 (45 in2

).

S.1.5. Dome Flange and Baffle Plates. - Any dome flange extending into a compartment shall be provided with 

sufficient perforations or openings flush with the compartment shell to prevent any trapping of air. All baffle plates 

in a compartment shall be so cut away at top and bottom, and elsewhere as necessary, as to facilitate loading and 

unloading.

S.1.6. Compartment and Piping Capacities and Emergency Valve. - If a compartment is equipped with an 

emergency (or safety) valve, this shall be positioned at the lowest point of outlet from the compartment, and the compartment capacity or capacities shall be construed as excluding the capacity of the piping leading therefrom. 

However, the capacity of the piping leading from such a compartment shall be separately determined and reported, 

and may be separately marked as specified in S.4.

S.1.6.1. On Vehicle Tanks Equipped for Bottom Loading. - On equipment designed for bottom loading, the 

compartment capacity shall include the piping of a compartment to the valve located on the upstream side of the 

manifold and immediately adjacent thereto or, if not manifolded, to the outlet valve, provided that on or immediately adjacent to the marking as specified in S.4. the following words or a statement of similar meaning 

shall be affixed: "Warning: Emergency valves must be opened before checking measurement."
4.40. Vehicle Tanks Used as Measures

4-4

S.1.7. Expansion Space. - When a compartment is filled to the level of the highest indicator in the compartment, 

there shall remain an expansion space of at least 0.75 percent of the nominal compartment capacity as defined by that 

indicator.

S.2. Design of Compartment Indicators.

S.2.1. General. - An indicator shall be so designed that it will distinctly and unmistakably define a capacity point of 

its compartment when liquid is in contact with the lowest portion of the indicator.

S.2.2. Number of Indicators. - In no case shall a compartment be provided with more than five indicators.

(Amended 1972)

S.2.3. Identification of Multiple Indicators. - If a compartment is provided with multiple indicators, each such 

indicator shall be conspicuously marked with an identifying letter or number.

S.2.4. Location. - An indicator shall be located:

(a) midway between the sides of its compartment;

(b) as nearly as practicable midway between the ends of its compartment, and in no case offset by more than 10 

percent of the compartment space or 15 cm (6 in), whichever is less;

(Amended 1972)

(c) so that it does not extend into, nor more than 15 cm (6 in) from that section of the compartment defined by a 

vertical projection of the fill opening;

(Amended 1974)

(d) at a depth, measuring from the top of the dome opening, not lower than 46 cm (18 in) for fill openings of 

less than 38 cm (15 in) in diameter, or, if other than circular, an effective area of less than 1130 cm2

(175 in2

), and not lower than 61 cm (24 in) for larger fill openings; and

(e) to provide a clearance of not less than 5 cm (2 in) between indicators.

S.2.5. Permanence. - Any indicator that is not intended to remain adjustable and all brackets or supports shall be 

securely welded in position.

S.2.6. Adjustable Indicators. - Adequate provision shall be made for conveniently affixing a security seal or seals:

(a) to any indicator intended to remain adjustable, so that no adjustment of the indicator can be made without 

mutilating or destroying the seal, and

(b) to any removable part to which an indicator may be attached, so that the part cannot be removed without 

mutilating or destroying the seal.

S.2.7. Sensitiveness. - The position of any indicator in its compartment shall be such that at the level of the indicator 

a change of 1.0 mm (0.04 in) in the height of the liquid surface will represent a volume change of not more than the 

value of the tolerance for the nominal compartment capacity as defined by that indicator.

S.3. Design of Compartment Discharge Manifold. - When two or more compartments discharge through a common 

manifold or other single outlet, effective means shall be provided to ensure:

(a) that liquid can flow through the delivery line leading from only one compartment at one time and that flow of 

liquid from one compartment to any other is automatically prevented, or

(b) that all compartments will discharge simultaneously.
4.40. Vehicle Tanks Used as Measures

4-5

If the discharge valves from two or more compartments are automatically controlled so that they can only be operated 

together, thus effectively connecting these compartments to one another, such compartments shall, for purposes of this 

paragraph, be construed to be one compartment.

S.4. Marking of Compartments.

S.4.1. Compartment Identification. - Each compartment of a multiple-compartment tank shall be conspicuously 

identified by a letter or number marked on the dome or immediately below the fill opening. Such letters or numbers 

shall be in regular sequence from front to rear, and the delivery faucets or valves shall be marked to correspond with 

their respective compartments.

S.4.2. Compartment Capacity, Single Indicator. - A compartment provided with a single indicator shall be clearly, 

permanently, and conspicuously marked with a statement of its capacity as defined by its indicator.

S.4.3. Compartment Capacity, Multiple Indicators. - A compartment provided with two or more indicators shall 

be clearly, permanently, and conspicuously marked with a statement identifying:

(a) each indicator by a letter or number and, immediately adjacent thereto,

(b) the capacity of the compartment as defined by the particular indicator.

N. Notes

N.1. Test Liquid. - Water or light fuel oil shall be used as the test liquid for a vehicle-tank compartment.

N.2. Evaporation and Volume Change. - Care shall be exercised to reduce to a minimum, evaporation losses and 

volume changes resulting from changes in temperature of the test liquid.

N.3. To Deliver. - A vehicle-tank compartment shall be gauged "to deliver." If the compartment is gauged by measuring 

the test liquid into the tank, the inside tank walls shall first be thoroughly wetted.

N.4. Gauging of Compartments. - When a compartment is gauged to determine the proper position for an indicator or 

to determine what a capacity marking should be, whether on a new vehicle tank or following repairs or modifications that 

might affect compartment capacities, tolerances are not applicable, and the indicator shall be set and the compartment 

capacity shall be marked as accurately as practicable.

N.5. Adjustment and Remarking. - When a compartment is found upon test to have an error in excess of the applicable 

tolerance, the capacity of the compartment shall be adjusted to agree with its marked capacity, or its marked capacity shall 

be changed to agree with its capacity as determined by the test.
4.40. Vehicle Tanks Used as Measures

4-6

T. Tolerances

T.1. Application.

T.1.1. To Excess and to Deficiency. - The tolerances hereinafter prescribed shall be applied to errors in excess and 

in deficiency.

T.2. Tolerance Values. - Maintenance and acceptance tolerances shall be as shown in Table 1.

Table 1.

Maintenance and Acceptance Tolerances

on Vehicle-Tank Compartments

Nominal capacity of compartment Maintenance and acceptance tolerances

gallons Expressed in quarts Expressed in gallons

200 or less 2 0.5

201 to 400, inclusive 3 0.75

401 to 600, inclusive 4 1.0

601 to 800, inclusive 5 1.25

801 to 1000, inclusive 6 1.50

over 1000 Add 1 quart per 200 gallons or 

fraction thereof

Add 0.25 gallon per 200 gallons or 

fraction thereof

UR. User Requirements

UR.1. Conditions of Use.

UR.1.1. Filling. - A vehicle shall stand upon a level surface during the filling of a compartment.

UR.1.2. Delivering. - During a delivery, a vehicle shall be so positioned as to assure complete emptying of a compartment. Each compartment shall be used for an individual delivery only; that is, an individual delivery shall consist 

of the entire contents of a compartment or compartments.

(Amended 1976)
4.41. Liquid Measures

4-7

Sec. 4.41. Liquid Measures

A. Application

A.1. - This code applies to liquid measures; that is, to rigid measures of capacity designed for general and repeated use in 

the measurement of liquids.

A.2. - The code does not apply to test measures or other volumetric standards.

A.3. - See also Sec. 1.10; General Code requirements.

S. Specifications

S.1. Units. -

a. The capacity of a liquid measure shall be 0.1 L, 0.2 L, 0.5 L, 1 L, 2 L, 5 L, or a multiple of 5 L, and the measure 

shall not be subdivided. 

b. The capacity of a liquid measure shall be 1 gill, 1/2 liquid pint, 1 liquid pint, 1 liquid quart, 1/2 gallon, 1-

1/4 gallon, 1-1/2 gallon, or a multiple of 1 gallon, and the measure shall not be subdivided. However, 3-pint and 

5-pint brick molds and 2-1/2 gallon (10-quart) cans shall be permitted when used exclusively for ice cream.

S.2. Material. - Measures shall be made of metal, glass, earthenware, enameled ware, composition, or similar and 

suitable material. If made of metal, the thickness of the metal shall not be less than the appropriate value given in 

Table 1.

S.3. Capacity Point. - The capacity of a measure shall be determined to a definite edge, or to the lowest portion of a 

plate, bar, or wire, at or near the top of the measure, and shall not include the capacity of any lip or rim that may be 

provided.

S.4. Reinforcing Rings. - Reinforcing rings, if used, shall be attached to the outside of the measure and shall show no 

divisions or lines on the inside surface of the measure.

S.5. Discharge. - A measure equipped with a discharge faucet or valve shall be susceptible to complete discharge 

through the faucet or valve when the measure is standing on a level surface.

S.6. Marking Requirements. - A measure shall be marked on its side with a statement of its capacity. If the capacity is 

stated in terms of the pint or quart, the word "Liquid" or the abbreviation "Liq" shall be included.

Table 1.

Minimum Thickness of Metal for Liquid Measures

Nominal capacity

Minimum thickness

For iron or steel, plated or 

unplated (inch) For copper or aluminum (inch)

1 pint or less 0.010 0.020

1 quart, 1/2 gallon, 1 gallon 0.014 0.028

Over 1 gallon 0.016 0.032
4.41. Liquid Measures

4-8

T. Tolerances

T.1. - Maintenance tolerances in excess and in deficiency shall be as shown in Table 2. Acceptance tolerances shall be 

one-half the maintenance tolerances.

Table 2.

Maintenance Tolerances, in Excess and in Deficiency, for Liquid Measures

Nominal capacity

Tolerance

In excess In deficiency

fluid drams cubic inches fluid drams cubic inches

1/2 pint or less 2.0 0.4 1.0 0.2

1 pint 3.0 0.7 1.5 0.3

1 quart 4.0 0.9 2.0 0.5

1/2 gallon 6.0 1.4 3.0 0.7

fluid

ounces

cubic

inches

fluid

drams

cubic

inches

1 and 1-1/4 gallons 1.0 1.8 4.0 0.9

1-1/2 gallons 1.5 2.7 6.0 1.4

fluid

ounces

cubic

inches

fluid

ounces

cubic

inches

2 gallons 2.0 3.5 1.0 1.8

3 and 4 gallons 4.0 7.0 2.0 3.6

5 gallons 6.0 11.0 3.0 5.4

10 gallons 10.0 18.0 5.0 9.0
4.42. Farm Milk Tanks

4-9

Sec. 4.42. Farm Milk Tanks

A. Application

A.1. - This code applies to farm milk tanks on the premises of producers when these are used, or are to be used, for the 

commercial measurement of milk.

A.2. - This code does not apply to tanks mounted on highway vehicles.

A.3. - See also Sec. 1.10; General Code requirements.

S. Specifications

S.1. Components. - A farm milk tank, whether stationary or portable, shall be considered suitable for commercial use 

only when it comprises:

(a) a vessel, whether or not it is equipped with means for cooling its contents;

(b) means for reading the level of liquid in the tank, such as a removable gauge rod or surface gauge; and

(c) a chart for converting level-of-liquid readings to volume.

Each compartment of a subdivided tank shall, for the purposes of this code, be construed to be a farm milk tank.

S.2. Design of Tank.

S.2.1. Level. - A farm milk tank shall be designed to be in normal operating position when it is in level. The tank 

shall be so constructed that it will maintain its condition of level under all normal conditions of lading.

S.2.2. Level-Indicating Means. - A tank shall be permanently equipped with sensitive means by which the level of 

the tank can be determined.

S.2.2.1. On a Stationary Tank. - A stationary tank shall be provided with such level-indicating means as a twoway or circular level, a plumb bob, two-way leveling lugs, or the like; or the top edge or edges of the tank shall 

be so constructed throughout as to provide an accurate reference for level determinations; provided, that when 

leveling lugs or the top edge or edges of the tank are used as the reference for level determinations, there shall be 

supplied with the tank a sensitive spirit level of appropriate dimensions, and the positions where such level is 

intended to be used shall be permanently marked on the reference surface of the tank; and provided further, that 

when leveling lugs are used they shall be so designed, constructed, and installed at the factory that any alteration 

of the original position or condition, such as by hammering or filing, would be difficult and would become 

obvious. A stationary tank with a nominal capacity of 2000 L or 500 gal, or greater shall be provided with at 

least two similar level-indicating means, and these shall be located in opposite and distant positions from each 

other to facilitate an accurate level determination in both directions of the tank's horizontal plane.

(Amended 1980)

S.2.2.2. On a Portable Tank. - A portable tank shall be provided with either a two-way or a circular level.

S.2.3. Portable Tank. - A portable tank shall be of the center-reading type; that is, it shall be so designed that the 

gauge rod or surface gauge, when properly positioned for use, will be approximately in the vertical axis of the tank, 

centrally positioned with respect to the tank walls.

S.2.4. Capacity. - A farm milk tank shall be clearly and permanently marked on a surface visible after installation 

with its capacity as determined by the manufacturer. The capacity shall not exceed an amount that can be agitated 

without overflowing and that can be measured accurately with the liquid at rest.

[Nonretroactive as of January 1, 1979]
4.42. Farm Milk Tanks

4-10

S.3. Design of Indicating Means.

S.3.1. General. - A tank shall include indicating means and shall be calibrated over the entire range of the 

volume of the tank from 5 percent of capacity or 2 m3 (500 gal) whichever is less, to its maximum capacity.

[Nonretroactive as of January 1, 1986]

(Added 1985)

S.3.2. Gauge-Rod Bracket or Supports. - If a tank is designed for use with a gauge rod, a substantial and rigid 

gauge-rod bracket or other suitable supporting elements for positioning the gauge rod shall be provided. A gauge rod 

and its brackets or other supporting elements shall be so constructed that, whenever the rod is placed in engagement 

with the bracket or supports and released, the rod will automatically seat itself at a fixed height and in a vertical 

position. When a gauge rod is properly seated on its brackets or supports, there shall be a clearance of at least 7.5 cm 

(3 in) between the graduated face of the rod and any tank wall or other surface that it faces.

S.3.3. Gauge Rod. - When properly seated in position, a rod shall not touch the bottom of the tank unless this is 

required by the design of the supporting elements. The rod shall be graduated throughout an interval corresponding 

to the volume range within which readings of liquid level are to be made.

S.3.4. Surface-Gauge Bracket or Supports. - If a tank is designed for use with a surface gauge, a substantial and 

rigid surface-gauge bracket or other suitable supporting elements for positioning the surface gauge shall be provided. 

A surface gauge and its brackets or other supporting elements shall be so constructed that, whenever the gauge 

assembly is placed in engagement with the bracket or supports, the indicator, if not permanently mounted on the tank, 

will automatically seat itself in correct operating position, and the graduated element will be vertically positioned and 

will be securely held at any height to which it may be manually set.

S.3.5. Surface Gauge. - When properly engaged with its bracket and set to its lowest position, a surface gauge shall 

not touch the bottom of the tank. The gauge shall be graduated throughout an interval corresponding to the volume 

range within which readings of liquid level are to be made.

S.3.6. External Gauge Assemblies (Added 1977)

S.3.6.1. Design and Installation. - The gauge assembly shall be designed to meet sanitary requirements and 

shall be readily accessible for cleaning purposes. The gauge assembly shall be mounted in a vertical position 

and equipped with a sliding mechanism to assist in determining the liquid level.

S.3.6.2. Gauge Tube. - The gauge tube shall be borosilicate glass or approved rigid plastic or rigidly supported 

flexible tubing with a uniform internal diameter not less than 2 cm (3/4 in). It shall be designed and constructed 

so that all product in the gauge can be discarded in such a manner that no product in the gauge tube will enter the 

discharge line or tank.

(Amended 1983)

S.3.6.3. Scale Plate. - The scale plate shall be mounted adjacent to and parallel with the gauge tube and be no 

more than 7 mm (1/4 in) from the tube.

S.3.6.4. Scale Graduations. - The graduation lines shall be clear and easily readable and shall comply with the 

requirements of paragraphs included under S.3.7. Graduations.

S.3.6.5. Venting. - An external gauge tube shall be adequately vented at the top, open to the atmosphere. Any 

attachment to the gauge tube shall not adversely affect the operation of this vent.

(Added 1984)

S.3.7. Graduations.

S.3.7.1. Spacing and Width of Graduations. - On a gauge rod or surface gauge, the spacing of the graduations, 

center to center, shall be not more than 1.6 mm (0.0625 in or 1/16 in) and shall not be less than 0.8 mm (0.03125 

in or 1/32 in). The graduations shall not be less than 0.12 mm (0.005 in) in width, and the clear interval between 

adjacent edges of successive graduations shall be not less than 0.4 mm (0.015625 in or 1/64 in).
4.42. Farm Milk Tanks

4-11

S.3.7.2. Values of Graduations. - On a gauge rod or surface gauge, the graduations may be designated in 

inches or in centimeters and fractions thereof, or may be identified in a numerical series without reference to 

inches or centimeters or fractions thereof. In either case, a volume chart shall be provided for each such rod or 

gauge and each tank with which it is associated, showing values in terms of the graduation on the rod or gauge. 

If a rod or gauge is associated with but one tank, in lieu of linear or numerical series graduations and volume 

chart, values in terms of volume of liquid in the tank may be shown directly on the rod or gauge.

S.3.7.3. Value of Graduated Interval. - The value of a graduated interval on a gauge rod or surface gauge 

(exclusive on the interval from the bottom of the tank to the lowest graduation) shall not exceed:

(a) 2 L for a tank of a nominal capacity of 1000 L or less; 1/2 gal for a tank of a nominal capacity of 250 

gal or less; 

(b) 4 L for a tank of a nominal capacity of 1001 L to 2000 L, inclusive; 1 gal for a tank of a nominal 

capacity of 251 gal to 500 gal, inclusive,

(c) 6 L for a tank of a nominal capacity of 2001 L to 6000 L, inclusive; 1-1/2 gal for a tank of a nominal 

capacity of 501 gal to 1500 gal, inclusive,

(d) 8 L for a tank of a nominal capacity of 6001 L to 10 000 L, inclusive; 2 gal for a tank of a nominal 

capacity of 1501 gal to 2500 gal, inclusive, 

(e) 8 L plus 4 L for each additional 10 000 L or fraction thereof, for tanks of nominal capacity above 

10 000 L or 2 gal plus 1 gal for each additional 2500 gal or fraction thereof, for tanks with nominal 

capacity above 2500 gal.

(Amended 1980)

S.3.8. Design of Indicating Means on Tanks with a Capacity Greater than 8000 Liters or 2000 gallon. - Any farm 

milk tank with a capacity greater than 8000 L, or 2000 gal, shall be equipped with an external gauge assembly.

[Nonretroactive and applicable only to tanks manufactured after January 1, 1981]

(Added 1980)

S.4. Design of Volume Chart.

S.4.1. General. - A volume chart shall show volume values only, over the entire range of the volume of the tank 

from 5 percent of capacity or 2 m3 (500 gal) whichever is less, to its maximum capacity.* All letters and figures on 

the chart shall be distinct and easily readable. The chart shall be substantially constructed, and the face of the chart 

shall be so protected that its lettering and figures will not tend easily to become obliterated or illegible. 

[*Nonretroactive as of January 1, 1986]

(Amended 1985)

S.4.2. For a Tank of 1000 Liters, or 250 Gallons, or Less. - The volume chart for a tank of nominal capacity of 

1000 L, or 250 gal, or less shall show values at least to the nearest 1 L, or 1/4 gal.

S.4.3. For a Tank of 1001 Liters to 2000 Liters, or 251 to 500 Gallons. - The volume chart for a tank of nominal 

capacity of 1001 L to 2000 L, or 251 gal to 500 gal, inclusive, shall show values at least to the nearest 2 L, or 1/2 gal.

S.4.4. For a Tank of Greater than 2000 Liters, or 500 Gallons. - The volume chart for a tank of nominal capacity 

of greater than 2000 L, or 500 gal, shall show values at least to the nearest gallon, or 4 L.

(Amended 1980)

S.5. Gauging.

S.5.1. Level. - A farm milk tank shall be level, as shown by the level-indicating means, during the original gauging 

operation.
4.42. Farm Milk Tanks

4-12

S.5.2. To Deliver. - A farm milk tank shall be originally gauged "to deliver." If the tank is gauged by measuring the 

test liquid into the tank, the inside tank walls shall first be thoroughly wetted and the tank shall then be drained for 30 

seconds after the main drainage flow has ceased.

S.5.3. Preparation of Volume Chart. - When a tank is gauged for the purposes of preparing a volume chart, 

tolerances are not applicable, and the chart shall be prepared as accurately as practicable.

S.6. Identification. - A tank and any gauge rod, surface gauge, spirit level, and volume chart intended to be used 

therewith shall be mutually identified, as by a common serial number, in a prominent and permanent manner.

N. Notes

N.1. Test Liquid. - Water shall be used as the test liquid for a farm milk tank.

N.2. Evaporation and Volume Change. - Care shall be exercised to reduce to a minimum, evaporation losses and

volume changes resulting from changes in temperature of the test liquid.

N.3. To Deliver. - A farm milk tank shall be tested "to deliver." If the tank is gauged by measuring the test liquid 

delivered into the tank, the inside tank walls shall first be thoroughly wetted and the tank then shall be drained for 30 

seconds after the main drainage flow has ceased.

N.4. Level. - A farm milk tank shall be level, as shown by the level-indicating means, during gauging and testing.

N.5. Test Methods. - Acceptance tests of milk tanks may be of either the prover method or the master meter method 

provided that the master metering system is capable of operating within 25 percent of the applicable tolerance found in 

T.3. Subsequent tests may be of either the prover method or the master meter method provided that the master metering 

system is capable of operating within 25 percent of the applicable tolerance found in T.4.

N.5.1. Verification of Master Metering Systems. - A master metering system used to gauge a milk tank shall be 

verified before and after the gauging process. A master metering system used to calibrate a milk tank, shall be 

verified before starting the calibration and reverified at least every quarter of the tank capacity, or every 2000 L (500 

gal), whichever is greater.

(Added 2001)

N.5.2. Temperature Changes in Water Supply. - When using a master metering system to gauge or calibrate a milk 

tank, the official shall monitor the temperature of the water before and after changing sources of supply. If the water 

temperature of the new source changes by more than 2.8 °C (5 °F) from the previous supply, the official shall 

reverify the accuracy of the master metering system as soon as possible after the system reaches temperature 

equilibrium with the new supply source.

(Added 2001)

N.6. Reading the Meniscus. - When a reading or setting is to be obtained from a meniscus formed by milk or other 

opaque liquid, the index or reading line is the position of the highest point of the center of the meniscus. When 

calibrating a device with water and the device is to be used with an opaque liquid, the reading should be obtained 

accordingly; that is, the position of the highest point of the center of the meniscus.

(Added 1984)

T. Tolerances

T.1. Application. - The tolerances hereinafter prescribed shall be applied equally to errors in excess and errors in 

deficiency.

T.2. Minimum Tolerance Values. - On a particular tank, the maintenance and acceptance tolerance applied shall be not 

smaller than the volume corresponding to the graduated interval at the point of test draft on the indicating means or 2 L 

(1/2 gal), whichever is greater.

(Amended 1980)
4.42. Farm Milk Tanks

4-13

T.3. Basic Tolerance Values. - The basic maintenance and acceptance tolerance shall be 0.2 percent of the volume of 

test liquid in the tank at each test draft.

(Amended 1975)

T.4. Basic Tolerance Values, Master Meter Method. - The basic maintenance and acceptance tolerance for tanks tested 

by the master meter method shall be 0.4 percent of the volume of test liquid in the tank at each test draft.

(Added 1975)

UR. User Requirements

UR.1. Installation. - A stationary tank shall be rigidly installed in level without the use of removable blocks or shims 

under the legs. If such tank is not mounted permanently in position, the correct position on the floor for each leg shall be 

clearly and permanently defined.

UR.2. Level Condition.

UR.2.1. Stationary Tank. - A stationary farm milk tank shall be maintained in level.

UR.2.1.1. Leveling Lugs. - If leveling lugs are provided on a stationary tank, such lugs shall not be hammered 

or filed to establish or change a level condition of the tank.

UR.2.2. Portable Tank. - On a portable tank, measurement readings shall be made only when the tank is 

approximately level; that is, when it is not out of level by more than 5 percent or approximately 3 degrees in any 

direction.

UR.3. Weight Chart. - An auxiliary weight chart may be provided, on which shall be prominently displayed the weight 

per unit volume value used to derive the weight values from the official volume chart.

UR.4. Use. - A farm milk tank shall not be used to measure quantities greater than an amount that can be agitated without 

overflowing.
4.43. Measure-Containers

4-15

Sec. 4.43. Measure-Containers

A. Application

A.1. - This code applies to measure-containers, including lids or closures if such are necessary to provide total enclosure 

of the measured commodity, as follows:

(a) Retail measure-containers intended to be used only once to determine at the time of retail sale, and from bulk 

supply, the quantity of commodity on the basis of liquid measure. The retail measure-container serves as the 

container for the delivery of the commodity.

(b) Prepackaged measure-containers intended to be used only once to determine in advance of sale the quantity of a 

commodity (such as ice cream, ice milk, or sherbet) on the basis of liquid measure. The prepackaged measure--

container serves as the container for the delivery of the commodity, in either a wholesale or a retail marketing 

unit.

A.2. - This code does not apply to rigid containers used for milk, cream, or other fluid dairy products, which are covered 

by packaging requirements.

A.3. - See also Sec. 1.10; General Code requirements.

S. Specifications

S.1. Units. - The capacity of a measure-container shall be a multiple of or a binary submultiple of a quart or a liter, and 

the measure shall not be subdivided. However, for prepackaged measure-containers, any capacity less than 1/4 L or 1/2 

liquid pint shall be permitted.

(Amended 1979)

S.2. Capacity Point. - The capacity of a measure-container shall be sharply defined by:

(a) the top edge,

(b) a line near the top edge, or

(c) the horizontal cross-sectional plane established by the bottom surface of the removable lid or cap when seated in 

the container.

S.3. Shape. - A measure-container shall be designed as some suitable geometrical shape, and its capacity shall be 

determined without distortion from its normal assembled shape.

S.4. Marking.

S.4.1. Capacity Point. - If the capacity point of a measure-container is defined by a line, the container shall be 

marked conspicuously on its side with a suitable statement clearly identifying this line as the capacity point.

S.4.2. Capacity Statement. - A measure-container shall be clearly and conspicuously marked with a statement of its 

capacity in terms of one of the units prescribed in S.1.
4.43. Measure-Containers

4-16

N. Notes

N.1. Test Liquid. - Water shall be used as the test liquid for a measure-container.

N.2. Preparation of Container for Test.

N.2.1. General. - Before an actual test is begun, a measure-container shall, if necessary, be so restrained that it will 

maintain its normal assembled shape and that its sides will not bulge when it is filled with water.

N.2.2. Restraining Form for Test.

N.2.2.1. For Rectangular Containers of One Liter, One Quarter Less. - Bulging of the sides of a rectangular 

measure-container of 1-liter (1-quart) capacity or less may be controlled by holding against each side of the 

container, with a cord, rubber bands, or tape, a metal plate or a piece of heavy cardboard slightly smaller than the 

side of the container.

(Amended 1979)

N.2.2.2. For Rectangular Prepackaged Measure-container of Two Quarts or Two Liters or Greater. - A 

rectangular prepackaged measure-container of 2-liter (2-quart) capacity or greater shall be supported during a 

test by a rigid restraining form. This form shall restrain not less than the entire area of the central two-thirds of 

each side of the container, measured from bottom to top. The inside width dimension of any side panel of the 

restraining form shall be 1.6 mm (1/16 in) greater than the corresponding outside dimension of the container. 

(The outside width dimension of any side panel of the container shall be established by adding to the inner side 

center-of-score to center-of-score dimension two thicknesses of the board used, and the sum thus obtained shall 

be rounded off to the nearest 0.4 mm (1/64 in).

(Amended 1979)

T. Tolerances

T.1. Tolerances on an Individual Measure. - The acceptance tolerances in excess and in deficiency on an individual 

measure shall be as shown in Table 1.

T.2. Tolerance on Average Capacity. - The average capacity on a random sample of ten measures selected from a lot of 

25 or more shall be equal to or greater than the nominal capacity.

(Amended 1979)

UR. User Requirements

UR.1. Limitation of Use. - The use of a measure-container with a rectangular cross section of a capacity of 2 L (2 qt) or 

greater shall be limited to the packaging, in advance of sale, of ice cream, sherbet, or other similar frozen desserts.

(Amended 1979)
4.43. Measure-Containers

4-17

Table 1.

Acceptance Tolerances,

in Excess and in Deficiency, for Measure-Containers

Nominal Capacity Tolerance

In excess In deficiency

milliliters milliliters

1/4 liter or less 10 5.0

1/2 liter 15 7.5

1 liter 20 10.0

Over 1 liter Add per liter

10 milliliters

Add per liter

5.0 milliliters

fluid drams cubic inches fluid drams cubic inches

1/2 pint or less 3 0.6 1.5 0.3

1 pint 4 1.0 2.0 0.5

1 quart 6 1.4 3.0 0.7

2 quarts 9 2.0 4.5 1.0

3 quarts 10 2.4 5.0 1.2

4 quarts 12 2.8 6.0 1.2

Over 4 quarts Add per quart 3 

fluid drams

Add per quart 

0.7 cubic inch

Add per quart 

1.5 fluid drams

Add per quart 0.35 

cubic inch
4.44. Graduates

4-19

Sec. 4.44. Graduates

A. Application

A.1. - This code applies to subdivided glass measures of capacity, either cylindrical or conical in shape.

A.2. - See also Sec. 1.10; General Code requirements.

S. Specifications

S.1. Units. - Nominal capacities, graduation ranges, values of graduated intervals, and numbered graduations applicable 

to single-scale graduates and to the appropriate portions of double scale graduates shall be as shown in Table 1.

Table 1.

Design Details for Graduates

Nominal

capacity To be graduated between

Value of

graduated intervals

Number at each 

graduation divisible by

milliliters milliliters milliliters milliliters

5

10

25

50

100

500

1 000

1 and

2 and 

5 and 

10 and 

20 and

100 and 

200 and 

5

10

25

50

100

500

1 000

1/2

1

5

5

10

25

50

1

2

5

10

20

50

100

minims minims minims minims

60

120

15 and

30 and

60

120

5

10

10a

20b

fluid drams fluid drams fluid drams fluid drams

4

8

1 and

2 and

4

8

1/2

1

1

2

fluid ounces fluid ounces fluid ounces fluid ounces

2

4

8

16

32

1/2 and

1 and

2 and

4 and

8 and

2

4

8

16

32

1/4

1/2

1/2

1

2

1/2

1

1

2

4

a

 And, in addition, at the first (15-minim) graduation.

b

 And, in addition, at the first (30-minim) graduation.

S.2. Initial Interval. - A graduate shall have an initial interval that is not subdivided, equal to not less than one-fifth and 

not more than one-fourth of the capacity of the graduate.
4.44. Graduates

4-20

S.3. Shape. - A graduate of a capacity of more than 15 mL (4 fluid drams) may be of either the cylindrical or circular 

conical type. A graduate of a capacity of 15 mL (4 fluid drams) or less shall be of the single-scale cylindrical type.

S.4. Material. - A graduate shall be made of good-quality, thoroughly annealed, clear, transparent glass, free from 

bubbles and streaks that might affect the accuracy of measurement. The glass shall be uniform in thickness and shall not 

be excessively thick.

S.5. Dimensional Proportions.

S.5.1. On a Circular Conical Graduate. - The inside measurement from the bottom of a circular conical graduate 

to the capacity graduation shall be not less than two times the inside diameter at the capacity graduation. The inside 

measurement from the bottom of the graduate to the point representing one-fourth of the capacity shall be not less 

than the inside diameter at that point.

S.5.2. On a Cylindrical Graduate. - The inside measurement from the bottom of a cylindrical graduate to the capacity graduation shall be not less than five times the inside diameter at the capacity graduation.

S.6. Base. - The base of the graduate shall be perpendicular to the vertical axis of the graduate. The diameter of the base 

shall be of such size that the empty graduate will remain standing on an inclined surface of 25 percent, or approximately 

15 degrees, from the horizontal.

S.7. Design of Graduations.

S.7.1. General. - Graduations shall be perpendicular to the vertical axis of the graduate and parallel to each other. 

Graduations shall be continuous, of uniform thickness not greater than 0.4 mm (0.015 in), clearly visible, permanent, 

and indelible under normal conditions of use.

(Amended 1977)

S.7.2. On a Single-Scale Graduate. - On a single-scale graduate, the main graduations shall completely encircle the 

graduate and subordinate graduations shall extend at least one-half the distance around the graduate.

S.7.3. On a Double-Scale or a Duplex Graduate. -

On a double-scale or duplex graduate, there shall be a 

clear space between the ends of the main graduations 

on the two scales, and this space shall be 

approximately 90 degrees from the lip of the graduate 

and shall conform to the requirements of Table 2.

S.8. Basis of Graduation. - A graduate shall be graduated 

"to deliver" when the temperature of the graduate is 20 C 

(68 F), and shall be marked accordingly in a permanent 

and conspicuous manner.

S.9. Marking Requirements. - Each main graduation shall be marked to show its value. Intermediate graduations shall 

not be marked. Value figures shall be uniformly positioned either directly upon or immediately above the graduations to 

which they refer. Figures placed upon graduations shall be set in from the ends of the graduations a sufficient distance to 

allow the ends of the graduations to be used in making a setting.

N. Notes

N.1. Test Liquid. - Water shall be used as the test liquid for graduates.

N.2. Temperature Control. - During the test of a graduate, appropriate precautions shall be exercised to reduce any 

detrimental temperature effects to the practicable minimum.

Table 2.

Clear Space Between Ends of Main

Graduations on Double Scale Graduates

Inside diameter of graduate at 

the graduations

(inches)

Clear space between ends 

of main graduations

(inch)

Less than 1.5 1/8 to 1/4

1.5 to 3, inclusive 1/4 to 1/2

Over 3 3/8 to 5/8
4.44. Graduates

4-21

T. Tolerances

T.1. - Maintenance and acceptance tolerances in excess and in deficiency shall be as shown in Table 3 for graduates that 

are graduated "to contain" or "to deliver." (The tolerance to be applied at any graduation is determined by the inside 

diameter of the graduate at the graduation in question.)

Table 3.

Maintenance and Acceptance Tolerances, in Excess and

in Deficiency, for Graduates

Inside diameter of graduate

Tolerance

Inside diameter of 

graduate Tolerance

From to but not 

including From to but not including

millimeters milliliters inches minims

0

16

21

26

31

36

41

46

51

56

61

66

71

76

81

86

91

96

16

21

26

31

36

41

46

51

56

61

66

71

76

81

86

91

96

101

0.1

0.2

0.4

0.6

0.8

1.1

1.4

1.8

2.2

2.8

3.4

4.1

4.8

5.6

6.4

7.2

8.1

9.0

0

9/16

13/16

1 1/16

1 5/16

1 9/16

1 13/16

2 1/16

2 5/16

2 9/16

2 13/16

3 1/16

3 5/16

3 9/16

3 3/16

9/16

13/16

1 1/16

1 5/16

1 9/16

1 13/16

2 1/16

2 5/16

2 9/16

2 13/16

3 1/16

3 5/16

3 9/16

3 13/16

4 1/16

2

3

6

10

15

20

30

40

50

65

80

95

110

130

150

(Table Amended 1974)
4.45. Dry Measures

4-23

Sec. 4.45. Dry Measures

A. Application

A.1. - This code applies to rigid measures of capacity designed for general and repeated use in the measurement of solids, 

including capacities of 1/2 bushel or more.

A.2. - This code does not apply to "standard containers" used for the measurement of fruits and vegetables and as 

shipping containers thereof.

A.3. - This code does not apply to berry baskets and boxes (for which, see Sec. 4.48; Code for Berry Baskets and Boxes).

(Added 1976)

A.4. - See also Sec. 1.10; General Code requirements.

S. Specifications

S.1. Units. - The capacity of a measure shall be 1 bushel, a multiple of the bushel, or a binary submultiple of the bushel, 

and the measure shall not be subdivided or double-ended.

S.2. Material. - A dry measure shall be made of any suitable material that will retain its shape during normal usage.

S.3. Shape. - A measure, other than a basket, of a capacity of 1/2 

bushel or less, shall be cylindrical or conical in shape. The top 

diameter shall in no case be less than the appropriate minimum

diameter shown in Table 1 (next page). The bottom of a measure, 

other than a basket, shall be perpendicular to the vertical axis of 

the measure and shall be flat, except that a metal bottom may be 

slightly corrugated. The bottom of a measure shall not be 

adjustable or movable.

S.3.1. Conical Dry Measure. - If conical, the top diameter 

shall exceed the bottom diameter by not more than 10 percent 

of the bottom diameter.

S.4. Capacity Point. - The capacity of a measure shall be determined by the top edge of the measure.

S.5. Top Reinforcement. - The top edge of a measure shall be reinforced. On a wooden measure other than a basket, of 

a capacity of 1 quart or more, this reinforcement shall be in the form of a firmly attached metal band.

S.6. Marking Requirements. - A measure shall be conspicuously marked on its side with a statement of its capacity. If 

the capacity is stated in terms of the pint or quart, the word "Dry" shall be included. The capacity statement shall be in 

letters of the following dimensions:

(a) At least 1/2 inch high and 1/4 inch wide on a measure of any capacity between 1/2 pint and 1 peck.

(b) At least 1 inch high and 1/2 inch wide on a measure of a capacity of 1/2 bushel or more.

(c) On a measure of a capacity of 1/4 pint or less, the statement shall be as prominent as practicable, considering the 

size and design of such measure.

N. Notes

N.1. Testing Medium.

N.1.1. Watertight Dry Measures. - Water shall be used as the testing medium for watertight dry measures.

Table 1.

Minimum Top Diameters for 

Dry Measures other than Baskets

Nominal capacity Minimum top diameter 

inches

1 pint 4

1 quart 5 3/8

2 quarts 6 5/8

1/2 peck 8 1/2

1 peck 10 7/8

1/2 bushel 13 3/4
4.45. Dry Measures

4-24

N.1.2. Nonwatertight Dry Measures. - A dry measure shall be tested either volumetrically using rape seed as a 

testing medium or geometrically through inside measurement and calculation.

(Amended 1988)

T. Tolerances

T.1. - Maintenance tolerances in excess and in deficiency shall be as shown in Table 2. Acceptance tolerances shall be 

one-half the maintenance tolerances.

Table 2.

Maintenance Tolerances, in Excess and in Deficiency,

for Dry Measures

Nominal capacity

Tolerance

In excess

cubic inches

In deficiency

cubic inches

1/32 pint or less 0.1 0.05

1/16 pint 0.15 0.1

1/8 pint 0.25 0.15

1/4 pint 0.5 0.3

1/2 pint 1.0 0.5

1 pint 2.0 1.0

1 quart 3.0 1.5

2 quarts 5.0 2.5

1/2 peck 10.0 5.0

1 peck 16.0 8.0

1/2 bushel 30.0 15.0

1 bushel 50.0 25.0
4.46. Berry Baskets and Boxes

4-25

Sec. 4.46. Berry Baskets and Boxes

A. Application

A.1. - This code applies to baskets and boxes for berries and small fruits in capacities of 1 dry quart and less.

A.2. - See also Sec. 1.10; General Code requirements.

S. Specifications

S.1. Units. - The capacity of a berry basket or box shall be 1/2 dry pint, 1 dry pint, or 1 dry quart.

S.2. Materials. - A berry basket or box shall be made of any suitable materials that will retain its shape during normal 

filling, storage, and handling.

S.3. Capacity Point. - The capacity of a berry basket or box shall be determined by its top edges.

N. Notes

N.1. Method of Test. - A berry basket or box may be tested either volumetrically, using rape seed as the testing medium, 

or geometrically through accurate inside dimension measurement and calculation.

T. Tolerances

T.1. Tolerances on Individual Measures. - Maintenance and acceptance tolerances in excess and deficiency on an 

individual measure shall be as shown in Table 1.

T.2. Tolerances on Average Capacity. - The average capacity on a random sample of 10 measures selected from a lot 

of 25 or more shall be equal to or greater than the nominal capacity.

(Amended 1979)

Table 1.

Maintenance and Acceptance Tolerances

in Excess and in Deficiency

Nominal Capacity Tolerance

In excess

cubic inches

In deficiency

cubic inches

1/2 pint 1 0.5

1 pint 2 1.0

1 quart 3 1.5
5-1

Section 5

Page

5.50. Fabric-Measuring Devices 5-3

5.51. Wire- and Cordage-Measuring Devices 5-7

5.52. Linear Measures 5-11

5.53. Odometers 5-13

5.54. Taximeters 5-17

5.55. Timing Devices 5-23

5.56.(a) Grain Moisture Meters 5-27

5.56.(b) Grain Moisture Meters 5-35

5.57. Near-Infrared Grain Analyzers - Tentative Code 5-41

5.58. Multiple Dimension Measuring Devices - Tentative Code 5-49
5-2
5.50. Fabric-Measuring Devices

5-3

Sec. 5.50. Fabric-Measuring Devices

A. Application

A.1. - This code applies only to mechanisms and machines designed to indicate automatically (with or without 

value-computing capabilities) the length of fabric passed through the measuring elements.

A.2. - Insofar as they are clearly appropriate, the requirements and provisions of this code apply also to devices 

designed for the commercial measurement of other material similar to fabrics, in sheet, roll, or bolt form.

A.3. - See also Sec. 1.10; General Code requirements.

S. Specifications

S.1. Units. - A fabric-measuring device shall indicate lengths in terms of 10 cm (1/8 yd), 25 cm (1/4 yd), 50 cm 

(1/2 yd), and meters (yd). In addition, lengths may be indicated in terms of any or all of the following subdivisions:

30 cm (1/3 yd), 6 cm (1/16 yd), meters and centimeters (feet and inches). Digital indicators may indicate values in 

decimal fractions.

(Amended 1977)

S.2. Design of Indicating Elements.

S.2.1. Graduations.

S.2.1.1. Length. - Graduations shall be so varied in length that they may be conveniently read.

S.2.1.2. Width. - In any series of graduations, the width of a graduation shall in no case be greater than the 

width of the minimum clear interval between graduations, and the width of main graduations shall be not 

more than 50 percent greater than the width of subordinate graduations. Graduations shall in no case be 

less than 0.2 mm (0.008 in) in width.

S.2.1.3. Clear Interval Between Graduations. - The clear interval between graduations shall be at least 

6 mm for cm graduations (1/4 in) for 1/8-yard graduations), and 3 mm for 20-cm graduations (1/8 inch for 

1-inch graduations).

S.2.2. Indicator.

S.2.2.1. Symmetry. - The index of an indicator shall be symmetrical with respect to the graduations, at 

least throughout that portion of its length associated with the graduations.

S.2.2.2. Length. - The index of an indicator shall reach to the finest graduations with which it is used, 

unless the indicator and the graduations are in the same plane, in which case the distance between the end 

of the indicator and the ends of the graduations, measured along the line of the graduations, shall be not 

more than 1.0 mm (0.04 in).

S.2.2.3. Width. - The index of an indicator shall not be wider than the narrowest graduations with which it 

is used, and shall in no case exceed 0.4 mm (0.015 in).

S.2.2.4. Clearance. - The clearance between the index of an indicator and the graduations shall in no case 

be more than 1.5 mm (0.06 in).

S.2.2.5. Parallax. - Parallax effects shall be reduced to the practicable minimum.
5.50. Fabric-Measuring Devices

5-4

S.2.3. Money-Value Computations.

S.2.3.1. Full-Computing Type. - In this type, the money value at each of a series of unit prices shall be 

computed automatically for every length within the range of measurement of the fabric-measuring device.

Value graduations shall be provided and shall be accurately positioned. The value of each graduated 

interval shall be 1 cent at all prices per yard of 30 cents and less, and shall not exceed 2 cents at higher 

prices per yard. Five-cent intervals may be represented in the 2-cent range by special graduations, but these 

shall not be positioned in the clear intervals between graduations of the regular series.

S.2.3.2. Limited-Computing Type. - In this type, the money value at each of a series of unit prices shall 

be computed automatically only for lengths corresponding to a definite series of length graduations. There 

shall be no value graduations. At no position that the chart can assume shall two value figures at the same 

price per yard be completely and clearly exposed to view at one time. Money values shown shall be 

mathematically accurate, except that a fraction of less than 1/2 cent shall be dropped and the next higher 

cent shall be shown in the case of a fraction of 1/2 cent or more. One of the following requirements shall 

be met:

(a) There shall be a money-value computation for each length graduation within the range of measurement of the device.

(b) No money-value computation shall be exposed to view except at such times as the device shows a 

length indication for which a corresponding series of value indications is computed.

(c) Each column or row of money-value computations shall be marked to show the length to which 

the computations correspond, the device shall be marked to show the character and limitations of 

the computations, and there shall be computations corresponding to at least 10 cm (1/8 yd) 

throughout the range of measurement of the device.

S.2.4. Return to Zero. - Primary indicating elements shall be readily returnable to a definite zero indication.

Means shall be provided to prevent the return of the indicating elements beyond their correct zero positions.

S.3. Marking Requirements. - If a device will not accurately measure all fabrics, it shall be marked to indicate 

clearly its limitations.

S.4. Design Accuracy. - Indications of length and money value shall be accurate whether the values of the 

indications are being increased or decreased.

N. Notes

N.1. Testing Medium. - A fabric-measuring device shall be tested with a suitable testing tape approximately 

7.62 cm (3 in) wide and with a graduated length of at least 11 m (12 yd), made from such material and having such 

surface finish as to provide dimensional stability and reduce slippage to the practicable minimum.
5.50. Fabric-Measuring Devices

5-5

T. Tolerances

T.1. Tolerance Values. - Maintenance and acceptance tolerances shall be as shown in Table 1.

Table 1.

Maintenance and Acceptance Tolerances

for Fabric-Measuring Devices

Indication of

device

(yards)

Maintenance tolerance Acceptance tolerance

On underregistration

(inches)

On overregistration

(inches)

On underregistration

(inches)

On overregistration

(inches)

2 or less 3/8 1/4 1/4 1/8

3 3/8 5/16 1/4 5/32

4 1/2 5/16 1/4 5/32

5 5/8 3/8 5/16 3/16

6 3/4 3/8 3/8 3/16

7 and 8 1 1/2 1/2 1/4

9 1-1/4 5/8 5/8 5/16

10 and 11 1-1/2 3/4 3/4 3/8

12 and 13 1-3/4 7/8 7/8 7/16

14 and 15 2 1 1 1/2

Over 15 Add 1/8 inch per 

indicated yard

Add 1/16 inch per 

indicated yard

Add 1/16 inch per 

indicated yard

Add 1/32 inch per 

indicated yard

UR. User Requirements

UR.1. Installation Requirements.

UR.1.1. Installation. - A fabric-measuring device shall be securely supported and firmly fixed in position.

UR.2. Use Requirements.

UR.2.1. Limitation of Use. - A fabric-measuring device shall be used to measure only those fabrics that it was 

designed to measure, and in no case shall it be used to measure a fabric that a marking on the device indicates 

should not be measured.

UR.2.2. Return of Indicating Elements to Zero. - The primary indicating elements shall be returned to zero 

before each measurement.
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5.51. Wire- and Cordage-Measuring Devices

5-7

Sec. 5.51. Wire- and Cordage-Measuring Devices

A. Application

A.1. - This code applies to mechanisms and machines designed to indicate automatically the length of cordage, rope, wire, 

cable, or similar flexible material passed through the measuring elements.

A.2. - See also Sec. 1.10; General Code requirements.

S. Specifications

S.1. Units. - A wire- or cordage-measuring device shall indicate lengths in terms of feet, yards, or meters, or combinations of units of the same measurement system, and shall have minimum increments with values that do not exceed the 

equivalent of 0.1 meter or 0.1 yard.

(Amended 1989)

S.2. Design of Indicating Elements.

S.2.1. Graduations.

S.2.1.1. Length. - Graduations shall be so varied in length that they may be conveniently read.

S.2.1.2. Width. - In any series of graduations, the width of a graduation shall in no case be greater than the 

width of the minimum clear interval between graduations, and the width of main graduations shall be not more 

than 50 percent greater than the width of subordinate graduations. Graduations shall in no case be less than 0.2 

mm (0.008 in), nor more than 1.0 mm (0.04 in), in width.

S.2.1.3. Clear Interval Between Graduations. - The clear interval between graduations shall be at least as 

wide as the widest graduation, and in no case less than 0.8 mm (0.03 in).

S.2.2. Indicator.

S.2.2.1. Symmetry. - The index of an indicator shall be symmetrical with respect to the graduations, at least 

throughout that portion of its length associated with the graduations.

S.2.2.2. Length. - The index of an indicator shall reach to the finest graduations with which it is used, unless the 

indicator and the graduations are in the same plane, in which case the distance between the end of the indicator 

and the ends of the graduations, measured along the line of the graduations, shall be not more than 1.0 mm 

(0.04 in).

S.2.2.3. Width. - The index of an indicator shall not be wider than the narrowest graduations with which it is 

used, and shall in no case exceed 0.4 mm (0.015 in).

S.2.2.4. Clearance. - The clearance between the index of an indicator and the graduations shall in no case be 

more than 1.5 mm (0.06 in).

S.2.2.5. Parallax. - Parallax effects shall be reduced to the practicable minimum.

S.2.3. Zero Indication. - Primary indicating elements shall be readily returnable to a definite zero indication.

S.3. Design of Measuring Elements.

S.3.1. Sensitiveness. - If the most sensitive element of the indicating system utilizes an indicator and graduations, 

the relative movement of these parts corresponding to a measurement of 30 cm (1 ft) shall be not less than 6 mm 

(1/4 in).
5.51. Wire- and Cordage-Measuring Devices

5-8

S.3.2. Slippage. - The measuring elements of a wire- or cordage-measuring device shall be so designed and 

constructed as to reduce to the practicable minimum any slippage of material being measured and any lost motion in 

the measuring mechanism.

S.3.3. Accessibility. - A wire- or cordage-measuring device shall be so constructed that the measuring elements are 

readily visible and accessible, without disassembly of any supporting frame or section of the main body, for purposes 

of cleaning or removing any foreign matter carried into the mechanism by the material being measured.

S.4. Marking Requirements.

S.4.1. Limitation of Use. - If a device will measure accurately only certain configurations, diameters, types, or 

varieties of materials, or with certain accessory equipment, all limitations shall be clearly and permanently stated on 

the device.

S.4.2. Operating Instructions. - Any necessary operating instructions shall be clearly stated on the device.

S.4.3. Indications. - Indicating elements shall be identified by suitable words or legends so that the values of the 

indications will be unmistakable.

S.5. Design Accuracy. - Indications of length shall be accurate whether the values of the indications are being 

increased or decreased.

N. Notes

N.1. Testing Medium. - Wherever feasible, a wire- or cordage-measuring device shall be tested with a steel tape not less 

than 10 mm (3/8 in) in width and at least 15 m (50 ft) in length. When a device cannot be tested in this manner because 

of the design of the device, it shall be tested with a dimensionally stable material appropriately marked and compared at 

frequent periodic intervals with a steel tape in order to assure that any marked interval is not in error by more than 1/3 of

the tolerance of the device at that particular interval.

(Amended 1981)

N.2. Minimum Test. - Tests shall be conducted at a minimum initial increment of 5 m (20 ft) and appropriate increments 

up to at least 15 m (50 ft).

T. Tolerances

T.1. Tolerance Values. - Maintenance and acceptance tolerances shall be as shown in Table 1.

Table 1.

Maintenance and Acceptance Tolerances for

Wire- and Cordage-Measuring Devices

Indication of device

(feet)

Acceptance and maintenance tolerances

On underregistration

(inches)

On overregistration

(inches)

20

Over 20 to 30

Over 30 to 40

Over 40 to 50

Over 50

6

8

10

12

Add 2 inches per indicated 10 feet

3

4

5

6

Add 1 inch per indicated 10 feet
5.51. Wire- and Cordage-Measuring Devices

5-9

UR. User Requirements

UR.1. Installation Requirements.

UR.1.1. Installation. - A wire- or cordage-measuring device shall be securely supported and firmly fixed in 

position.

UR.2. Use Requirements.

UR.2.1. Limitation of Use. - A wire- or cordage-measuring device shall be used to measure only those materials 

that it was designed to measure, and in no case shall it be used to measure a material that a marking on the device 

indicates should not be measured.

UR.2.2. Return to Zero. - The primary indicating elements of a wire- or cordage-measuring device shall be 

returned to zero before each measurement.

UR.2.3. Operation of Device. - A wire- or cordage-measuring device shall not be operated in such a manner as to 

cause slippage or inaccurate measurement.

UR.2.4. Cleanliness. - The measuring elements of a wire- or cordage-measuring device shall be kept clean to 

prevent buildup of dirt and foreign material that would adversely affect the measuring capability of the device.

5.52. Linear Measures

5-11

Sec. 5.52. Linear Measures

A. Application

A.1. - This code applies to any linear measure or measure of length, whether flexible or inflexible, permanently installed 

or portable.

A.2. - See also Sec. 1.10; General Code requirements.

S. Specifications

S.1.M. Units. - A linear measure may be in total length, and the total length may be subdivided in any or all of the 

following:

(a) centimeters and tenths of the centimeter;

(b) meters; and

(c) multiples of meters

A 1-m measure may be graduated, in addition, to show 0.1-m and multiples of 0.1-m subdivisions.

S.1. Units. - A linear measure may be in total length, and the total length may be subdivided in any or all of the 

following:

(a) inches and binary submultiples of the inch;

(b) feet;

(c) yards and multiples of yards.

A 1-yd measure may be graduated, in addition, to show 1/3-yd and 2/3-yd subdivisions. A flexible tape may be graduated 

in tenths or hundredths of a foot, or both tenths and hundredths of a foot. (Any other subdivisions are allowable only on 

measures of special purposes and when required for such purposes.)

S.2. Material.

S.2.1. Flexible Tape. - A flexible tape shall be made of metal.

S.2.2. End Measure. - If an end measure is made of material softer than brass, the ends of the measure shall be 

protected by brass (or other metal at least equally hard) securely attached.

S.3. Finish. - Measures shall be smoothly finished.

S.4. Design.

S.4.1. Rigid Measure. - A rigid measure shall be straight.

S.4.2. Folding Measure. - A folding measure shall open to a definite stop, and when so opened shall be straight.

S.5. Graduations.

S.5.1. General. - Graduations shall be perpendicular to the edge of the measure.

S.5.2. Width. - The width of the graduations on any measure shall not exceed one-half the width of the smallest 

graduated interval on the measure, and in no case shall be wider than 0.75 mm (0.03 in).

(Amended 1982)
5.52. Linear Measures

5-12

T. Tolerances

T.1. For Measures Except Metal Tapes. - Maintenance tolerances in excess and in deficiency for measures except 

metal tapes shall be as shown in Table 1. Acceptance tolerances shall be one-half the maintenance tolerances.

T.2. For Metal Tapes. - Maintenance and acceptance tolerances in excess and in deficiency for metal tapes shall be as 

shown in Table 2. Tapes of 10 m (25 ft) or over shall be tested at a tension resulting from a load of 5 kg (10 lb). Tapes 

less than 10 m (25 ft) shall be tested at a tension resulting from a load of 2.5 kg (5 lb). However, flexible metal tapes of 

10 m (25 ft) or less that are not normally used under tension shall be tested with no tension applied. All tapes shall be 

supported throughout on a horizontal flat surface whenever tested. 

(Amended 1972)

Table 1.

Maintenance Tolerances, in Excess

and in Deficiency, for Linear Measures Except 

Metal Tapes

Nominal interval

from zero Tolerance

feet inch

1/2 or less

1

2

3

4

5

6

1/64

1/32

1/16

3/32

1/8

5/32

3/16

Table 2.

Maintenance and Acceptance Tolerances,

in Excess and in Deficiency, for 

Metal Tapes

Nominal interval

from zero Tolerance

feet inch

6 or less

7 to 30, inclusive

31 to 55, inclusive

56 to 80, inclusive

81 to 100, inclusive

1/32

1/16

1/8

3/16

1/4
5.53. Odometers

5-13

Sec. 5.53. Odometers

A. Application

A.1. - This code applies to odometers that are used or are to be used to determine the charges for rent or hire of passenger 

vehicles and trucks and buses. (When official examinations are undertaken on odometers that form the basis for the 

payment of fees or taxes to, or the preparation of reports for, governmental agencies, and in similar cases, the 

requirements of this code shall be applied insofar as they are applicable and appropriate to the conditions of such special 

uses.)

(Amended 1977)

A.2. - This code does not apply to taximeters (for which see Sec. 5.54; Code for Taximeters).

(Amended 1977)

A.3. - See also Sec. 1.10; General Code requirements.

S. Specifications

S.1. Design of Indicating Elements.

S.1.1. General. - The primary indicating element of an odometer may be:

(a) the distance-traveled portion of the "speedometer" assembly of a motor vehicle;

(b) a special cable-driven distance-indicating device; or

(c) a hub odometer attached to the hub of a wheel on a motor vehicle.

(Amended 1977)

S.1.2. Units. - An odometer shall indicate in terms of miles or kilometers.

(Amended 1977)

S.1.3. Minimum Indicated Value. - The value of the interval of indicated distance shall be:

(a) for odometers indicating in kilometers, 0.1 kilometer; or 

(b) for odometers indicating in miles, 0.1 mile.

(Amended 1977)

S.1.4. Advancement of Indicating Elements. - The most sensitive indicating elements of an odometer may advance 

continuously or intermittently; all other elements shall advance intermittently. Except when the indications are being 

returned to zero, the indications of an installed odometer shall be susceptible to advancement only by the rotation of 

the vehicle wheel or wheels. (Amended 1977)

S.1.5. Readability. - Distance figures and their background shall be of sharply contrasting colors. Figures indicating 

tenth units shall be differentiated from other figures with different colors, or with a decimal point, or by other equally 

effective means. Except during the period of advance of any decade to the next higher indication, only one figure in 

each decade shall be exposed to view. Any protective covering intended to be transparent shall be in such condition 

that it can be made transparent by ordinary cleaning of its exposed surface.

(Amended 1977)

S.1.6. Digital Indications and Representation. - Digital indicating odometers (discontinuous registration) shall 

"round off" indications to the nearest minimum division or truncate indications to the lower minimum division.

(Added 1990)
5.53. Odometers

5-14

N. Notes

N.1. Testing Procedures.

N.1.1. Test Methods. - To determine compliance with distance tolerances, a distance test of an odometer shall be 

conducted using one or more of the following test methods:

(a) Road Test. - A road test consists of driving the vehicle over a precisely measured road course.

(b) Fifth-Wheel Test. - A fifth-wheel test consists of driving the vehicle over any reasonable road course and 

determining the distance actually traveled through the use of a mechanism known as a "fifth wheel" that is 

attached to the vehicle and that independently measures and indicates the distance.

(c) Simulated-Road Test. - A simulated road test consists of determining the distance traveled by use of a roller 

device, or by computation from rolling circumference and wheel-turn data.

(Amended 1977)

N.1.2. Test Runs. - Not less than two test runs shall be conducted. Acceleration and deceleration shall be carefully 

controlled to avoid spinning or skidding the wheels.

(Amended 1977)

N.1.2.1. For Devices Indicating in Miles. - The test runs shall be 2 miles in length, shall start from, and finish 

at, a dead stop with a minimum of 80 percent of the run between 30 miles per hour and 45 miles per hour.

(Added 1977)

N.1.2.2. For Devices Indicating in Kilometers. - The test runs shall be 3 kilometers in length, shall start from, 

and finish at, a dead stop with a minimum of 80 percent of the run between 50 kilometers per hour and 75 

kilometers per hour. (Added 1977)

N.1.3. Test Conditions.

N.1.3.1. Tire Stabilization. - Road tests or fifth-wheel tests shall be preceded by a run of at least 8 kilometers 

or 5 miles, for the purpose of stabilizing tire pressures. Simulated road tests on a roller device shall be made at 

stable tire pressures.

(Amended 1977)

N.1.3.2. Tire Pressure. - At the completion of the test run or runs, the tires of the vehicle under test shall be 

checked to determine that the tire pressure is that operating tire pressure posted in the vehicle. If not, the tire 

pressure should be adjusted to the posted tire pressure and further tests may be conducted to determine the 

operating characteristics of the odometer.

(Amended 1977)

N.1.3.3. Vehicle Loading.

(a) Passenger Load. - During the distance test of an odometer, the vehicle may carry two persons.

(b) Truck Cargo Load. - Truck odometers shall be tested by one of the following methods:

(1) the truck is loaded with one-half of the maximum cargo load; or

(2) unloaded if unloaded test tolerances are applied.

(Amended 1977 and 1987)

T. Tolerances

T.1. To Underregistration and to Overregistration. The tolerances hereinafter prescribed shall be applied to errors of 

underregistration and errors of overregistration.
5.53. Odometers

5-15

T.2. Tolerance Values. - Except for unloaded trucks, maintenance and acceptance tolerances on odometers shall be 4 

percent of the interval under test.

(Amended 1977and 1987)

T.2.1. Tolerances for Unloaded Trucks. - Maintenance and acceptance tolerances on truck odometers shall be 5 

percent for underregistration and 3 percent for overregistration of the interval under test.

(Added 1987)

UR. User Requirements

UR.1. Inflation of Vehicle Tires. - The operational tire pressure of passenger vehicle and truck tires shall be posted in 

the vehicle and tires shall be maintained at the posted pressure.

(Amended 1977)

5.54. Taximeters

5-17

Sec. 5.54. Taximeters

A. Application

A.1. This code applies to taximeters; that is, to devices that automatically calculate at a predetermined rate or rates and 

indicate the charge for hire of a vehicle.

A.2. This code does not apply to odometers on vehicles that are rented on a distance basis (for which see Sec. 5.53 Code 

for Odometers).

(Amended 1977)

A.3. See also Sec. 1.10; General Code requirements.

S. Specifications

S.1. Design of Indicating and Recording Elements.

S.1.1. General. - A taximeter shall be equipped with a primary indicating element and may be equipped with a 

recording element.

(Amended 1988)

S.1.2. Advancement of Indicating Elements. - Except when a taximeter is being cleared, the primary indicating 

and recording elements shall be susceptible of advancement only by the movement of the vehicle or by the time 

mechanism. (Amended 1988)

S.1.3. Visibility of Indications. - The indications of fare, including extras, and the mode of operation, such as "time" 

or "hired," shall be constantly displayed whenever the meter is in operation. All indications of passenger interest 

shall be easily read from a distance of 1.2 m (4 ft) under any condition of normal operation.

(Amended 1977, 1986, and 1988)

S.1.3.1. Minimum Height of Figures, Words, and Symbols. - The minimum height of the figures used to 

indicate the fare shall be 10 mm and for extras, 8 mm. The minimum height of the figures, words, or symbols 

used for other indications, including those used to identify or define, shall be 3.5 mm.

(Added 1986)

S.1.3.2. Lighting of Indications. - Integral lighting shall be provided to illuminate the fare, extras, the rate or 

rate code, and the taximeter status (i.e., vacant, hired, and time off).

[Nonretroactive as of January 1, 1989]

(Added 1988)(Amended 1990)

S.1.4. Actuation of Fare-Indicating Mechanism. - When a taximeter designed to calculate fares upon the basis of a 

combination of distance traveled and time elapsed is operative with respect to fare indication, the fare-indicating 

mechanism shall be actuated by the distance mechanism whenever the vehicle is in motion at such a speed that the 

rate of distance revenue equals or exceeds the time rate, and may be actuated by the time mechanism whenever the 

vehicle speed is less than this and when the vehicle is not in motion. Means shall be provided for the vehicle 

operator to render the time mechanism either operative or inoperative with respect to the fare-indicating mechanism.

(Amended 1977)

S.1.5. Operating Condition.

S.1.5.1. General. - When a taximeter is cleared, the indication "Not Registering," "Vacant," or an equivalent 

expression shall be shown. Whenever a taximeter is set to register charges, it shall indicate "Registering," 

"Hired," or an equivalent expression and the rate at which it is set shall be automatically indicated (Rate 1 or 

Rate A, for example).

(Amended 1988)
5.54. Taximeters

5-18

S.1.5.2. Time not Recording. - When a taximeter is set for fare registration with the time mechanism 

inoperative, it shall indicate "Time Not Recording" or an equivalent expression.

(Amended 1988)

S.1.6. Fare Identification. - Fare indications shall be identified by the word "Fare" or by an equivalent expression. 

Values shall be defined by suitable words or monetary signs.

S.1.7. Extras. - Extras shall be indicated as a separate item and shall not be included in the fare indication. They 

shall be identified by the word "Extras" or by an equivalent expression. Values shall be defined by suitable words or 

monetary signs. Means may be provided to totalize the fare and extras if the totalized amount returns to separate 

indications of fare and extras within 5 seconds or less.

(Amended 1988)

S.1.7.1. Nonuse of Extras. - If and when taximeter extras are prohibited by legal authority or are discontinued 

by a vehicle operator, the extras mechanisms shall be rendered inoperable or the extras indications shall be 

effectively obscured by permanent means.

S.1.8. Protection of Indications. - Indications of fare and extras shall be displayed through and entirely protected by 

glass or other suitable transparent material securely attached to the housing of the taximeter.

S.1.9. Recorded Representation. - A printed receipt issued from a taximeter, whether through an integral or separate 

recording element, shall include the following:

(a) date

(b) unique vehicle identification number, such as the medallion number, taxi number, vehicle identification 

number (VIN) or permit number*

(c) start and end time of trip*

(d) distance traveled, maximum increment of 0.1 kilometer (0.1 mile)*

(e) fare in $

(f) for multi-rate taximeters, each rate at which fare was computed and the associated fare at that rate*

(g) additional charges where permitted such as extras, surcharge, telephone use, tip and tax shall be identified 

and itemized*

(h) total fare in $ (total charge)*

[Nonretroactive as of January 1, 1989] *[Nonretroactive as of January 1, 2000]

(Added 1988)(Amended 1999)

S.1.9.1. Multiple Recorded Representations.

S.1.9.1.1. Duplicate Receipts. - A recording element may produce a duplicate receipt for the previous 

transaction provided the information printed is identical to the original with the exception of time issued. 

The duplicate receipt shall include the words "duplicate" or "copy." The feature to print a duplicate receipt 

shall be deactivated at the time the meter is hired for the next fare.

[Nonretroactive as of January 1, 2000]

(Added 1999)
5.54. Taximeters

5-19

S.1.10. Non-fare Information. - The fare and extras displays may be used to display auxiliary information 

provided the meter is in the vacant condition and such information is only displayed for ten seconds, or less. If 

the information consists of a list of information, the list may be displayed one item after another, provided that 

each item is displayed for ten seconds, or less.

[Nonretroactive as of January 1, 2002]

(Added 2000)

S.2. Basis of Fare Calculations. - A taximeter shall calculate fares only upon the basis of:

(a) distance traveled,

(b) time elapsed, or

(c) a combination of distance traveled and time elapsed.

(Amended 1977)

S.2.1. Initial Time and Distance Intervals. - The time and distance intervals of a taximeter shall be directly 

proportional as expressed in the following formula:

Distance per Non Initial Mileage Interval

Distance of Initial Mileage Interval

Seconds per Non Initial Time Interval

Seconds of Initial Time Interval

− = −

(Added 1990)

S.3. Design of Operating Control.

S.3.1. Positions of Control. - The several positions of the operating controls shall be clearly defined and shall be so 

constructed that accidental or inadvertent changing of the operating condition of the taximeter is improbable. 

Movement of the operating controls to an operating position immediately following movement to the cleared position 

shall be delayed enough to permit the taximeter to come to a complete rest in the cleared position.

(Amended 1988)

S.3.2. Flag. - If the control for the operating condition is a lever-arm and flag, the flag shall be at its highest position 

when the taximeter is cleared, and in this position the whole of the flag shall be above the level of the taximeter 

housing.

S.3.3. Control for Extras Mechanism. - The knob, handle, or other means provided to actuate the extras mechanism shall be inoperable whenever the taximeter is cleared.

S.4. Interference. - The design of a taximeter shall be such that there will be no interference between the time and the 

distance portions of the mechanism device at any speed of operation.

(Amended 1977 and 1988)

S.5. Provision for Security Seals. - Adequate provision shall be made to provide security for a taximeter. Security may 

be provided either by:

(a) Affixing security seals to the taximeter and to all other components required for service operation of a complete 

installation on a vehicle, so that no adjustments, alterations, or replacements affecting accuracy or indications of 

the device or the assembly can be made without mutilating the seal or seals; or
5.54. Taximeters

5-20

(b) Using a combination of security seals described in paragraph (a) and, in the case of a component that may be 

removed from a vehicle (e.g., slide mounting the taximeter), providing a physical or electronic link between 

components affecting accuracy or indications of the device to ensure that its performance is not affected and 

operation is permitted only with those components having the same unique properties.

The sealing means shall be such that it is not necessary to disassemble or remove any part of the device or of the 

vehicle to apply or inspect the seals.

(Amended 1988 and 2000)

S.6. Power Interruption, Electronic Taximeters.

(a) After a power interruption of 3 seconds or less, the fare and extras indications shall return to the previously 

displayed indications and may be susceptible to advancement without the taximeter being cleared.

(b) After a power interruption exceeding 3 seconds, the fare and extras indications shall return to the previously 

displayed indications and shall not be susceptible to advancement until the taximeter is cleared.

After restoration of power following an interruption exceeding 3 seconds, the previously displayed fare shall be displayed 

for a maximum of 1 minute at which time the fare shall automatically clear and the taximeter shall return to the vacant 

condition.*

*[Nonretroactive as of January 1, 2002]

(Added 1988) (Amended 1989, 1990, and 2000)

S.7. Anti-fraud Provisions, Electronic Taximeters. - An electronic taximeter may have provisions to detect and 

eliminate distance input that is inconsistent with output of the vehicle's distance sensor. When a taximeter equipped with 

this feature detects input inconsistent with the distance sensor:

(a) The meter shall either filter out the inconsistent distance input signals or cease to increment fare based on 

distance until the distance input signal returns to normal. If the meter ceases to increment fare based on distance,

the taximeter may continue to increment fare based on elapsed time;

(b) The taximeter shall provide a visible or audible signal that inconsistent input signals are being detected; and

(c) The taximeter shall record the occurrence in an event logger. The event logger shall include an event counter 

(000 to 999), the date, and the time of at least the last 1000 occurrences.

(Added 2001)

N. Notes

N.1. Distance Tests.

N.1.1. Test Methods. - To determine compliance with distance tolerances, a distance test of a taximeter shall be 

conducted utilizing one or more of the following test methods:

(a) Road Test. - A road test consists of driving the vehicle over a precisely measured road course.

(b) Fifth-Wheel Test. - A fifth-wheel test consists of driving the vehicle over any reasonable road course and 

determining the distance actually traveled through the use of a mechanism known as a "fifth wheel" that is 

attached to the vehicle and that independently measures and indicates the distance.

(c) Simulated-Road Test. - A simulated road test consists of determining the distance traveled by use of a 

roller device, or by computation from rolling circumference and wheel-turn data.

(Amended 1977)
5.54. Taximeters

5-21

N.1.2. Test Procedures. - The distance test of a taximeter, whether a road test, a simulated-road test, or a fifth-wheel 

test, shall include at least duplicate runs of sufficient length to cover at least the third money drop or 1 mile, 

whichever is greater, and shall be at a speed approximating the average speed traveled by the vehicle in normal 

service. In the case of metric-calibrated taximeters, the test should cover at least the third money drop or 2 km, 

whichever is greater.

(Amended 1977)

N.1.3. Test Conditions.

N.1.3.1. Vehicle Lading. - During the distance test of a taximeter, the vehicle shall carry two persons, or in the 

case of a simulated-road test, 70 kg or 150 lb of test weights may be substituted in lieu of the second person.

N.1.3.2. Tire Pressure. - At the completion of test run or runs, the tires of the vehicle under test shall be 

checked to determine that the tire pressure is that operating tire pressure posted in the vehicle. If not, the tire 

pressure should be adjusted to the posted tire pressure and further tests may be conducted to determine the 

operating characteristics of the odometer.

(Amended 1977)

N.2. Time Test. - If a taximeter is equipped with a timing device through which charges are made for time intervals, the 

timer shall be tested at the initial interval, four separate subsequent intervals, and an average time test of at least four 

consecutive subsequent time intervals.

(Amended 1988)

N.3. Interference Test. - If a taximeter is equipped with a timing device through which charges are made for time 

intervals, a test shall be conducted to determine whether there is interference between the time and distance elements.

During the interference test, the vehicle's operating speed shall be 3 km/h or 4 km/h, or 2 mi/h or 3 mi/h faster than the 

speed at which the basic distance rate equals the basic time rate. The basic rate per hour divided by the basic rate per mile 

is the speed (km/h or mi/h) at which the basic time rate and basic distance rate are equal.

(Amended 1988)

T. Tolerances

T.1. Tolerance Values.

T.1.1. On Distance Tests. - Maintenance and acceptance tolerances for taximeters shall be as follows:

(a) On Overregistration: 1 percent of the interval under test.

(b) On Underregistration: 4 percent of the interval under test, with an added tolerance of 30 m or 100 ft 

whenever the initial interval is included in the interval under test.

T.1.2. On Time Tests.

T.1.2.1. On Individual Time Intervals. - Maintenance and acceptance tolerances on individual time intervals 

shall be as follows:

(a) On Overregistration: 3 seconds per minute (5 percent).

(b) On Underregistration: 9 seconds per minute (15 percent) on the initial interval, and 6 seconds per 

minute (10 percent) on subsequent intervals.
5.54. Taximeters

5-22

T.1.2.2. On Average Time Interval Computed After the Initial Interval. - Except for the initial interval, 

maintenance and acceptance tolerances on the average time interval shall be as follows:

(a) On Overregistration: 0.2 second per minute (0.33 percent).

(b) On Underregistration: 3 seconds per minute (5 percent).

(Amended 1991)

T.1.3. On Interference Tests.

T.1.3.1. The registration of a taximeter in the "time on" position shall agree within one percent of its 

performance in the "time off" position.

(Added 1988)

UR. User Requirements

UR.1. Inflation of Vehicle Tires. - The operational tire pressure of passenger vehicles and truck tires shall be posted in 

the vehicle and shall be maintained at the posted pressure.

(Amended 1977)

UR.2. Position and Illumination of Taximeter. - A taximeter shall be so positioned and illuminated that its indications, 

operational markings, and controls of passenger interest can be conveniently read by a passenger seated in the back seat 

of the vehicle.

(Amended 1985 and 1986)

UR.3. Statement of Rates. - The distance and time rates for which a taximeter is set, including the initial distance 

interval and the initial time interval, the local tax rate, and the schedule of extras when an extras indication is provided,

shall be conspicuously displayed inside the front and rear passenger compartments. The words "Rate," "Rates," or "Rates 

of Fare" shall precede the rate statement. The rate statement shall be fully informative, self-explanatory, and readily 

understandable by the ordinary passenger, and shall either be of a permanent character or be protected by glass or other 

suitable transparent material.

(Amended 1977, 1988, 1990, and 1999)
5.55. Timing Devices

5-23

Sec. 5.55. Timing Devices

A. Application

A.1. - This code applies to devices used to measure time during which services are being dispensed (such as vehicle 

parking, laundry drying, and car washing).

A.2. - See also Sec. 1.10; General Code requirements.

S. Specifications

S.1. Design of Indicating and Recording Elements and of Recorded Representations.

S.1.1. Primary Elements.

S.1.1.1. General. - A timing device shall be equipped with a primary indicating element, and may also be 

equipped with a primary recording element. A readily observable in-service light or other equally effective 

means that automatically indicates when laundry driers, vacuum cleaners, and car washes are in operation shall 

be deemed an appropriate primary indicating element.

(Amended 1979)

S.1.1.2. Units. - A timing device shall indicate and record, if the device is equipped to record, the time in terms 

of minutes for time intervals of 60 minutes or less and in hours and minutes for time intervals greater than 

60 minutes.

S.1.1.3. Value of Smallest Unit. - The value of the smallest unit of indicated time and recorded time, if the 

device is equipped to record, shall not exceed the equivalent of:

(a) one-half hour on parking meters indicating time in excess of 2 hours;

(b) six minutes on parking meters indicating time in excess of 1 but not greater than 2 hours; or

(c) five minutes on all other devices, except those equipped with an in-service light.

(Amended 1975)

S.1.1.4. Advancement of Indicating and Recording Elements. - Primary indicating and recording elements 

shall be susceptible to advancement only during the mechanical operation of the device, except that clocks may 

be equipped to manually reset the time.

S.1.1.5. Operation of In-Service Indicator Light. - The in-service light indicator shall be operative only 

during the time the device is in operation.

S.1.1.6. Discontinuous Indicating Parking Meters. - An indication of the time purchased shall be provided at 

the time the meter is activated in units of no more than 1 minute for times less than 1 hour and not more than 

2 minutes for times of 1 hour or more. Convenient means shall be provided to indicate to the purchaser the 

unexpired time.

(Added 1975 and amended 1976)

S.1.2. Graduations.

S.1.2.1. Length. - Graduations shall be so varied in length that they may be conveniently read.

S.1.2.2. Width. - In any series of graduations, the width of a graduation shall in no case be greater than the 

width of the minimum clear interval between graduations and the width of main graduations shall be not more 

than 50 percent greater than the width of subordinate graduations. Graduations shall in no case be less than 0.2 

mm (0.008 in) in width.
5.55. Timing Devices

5-24

S.1.2.3. Clear Interval Between Graduations. - The clear interval shall be not less than 0.75 mm (0.03 in). If 

the graduations are not parallel, the measurement shall be made:

(a) along the line of relative movement between the graduations at the end of the indicator, or

(b) if the indicator is continuous, at the point of widest separation of the graduations.

S.1.3. Indicators.

S.1.3.1. Symmetry. - The index of an indicator shall be symmetrical with respect to the graduations, at least 

throughout that portion of its length associated with the graduations.

S.1.3.2. Length. - The index of an indicator shall reach to the finest graduations with which it is used, unless the 

indicator and the graduations are in the same plane, in which case the distance between the end of the indicator 

and the ends of the graduations, measured along the line of the graduations, shall be not more than 1.0 mm 

(0.04 in).

S.1.3.3. Width. - The width of the index of an indicator in relation to the series of graduations with which it is 

used shall be not greater than

(a) the width of the widest graduation, and

(b) the width of the minimum clear interval between the graduations.

S.1.3.4. Parallax. - Parallax effect shall be reduced to a practicable minimum.

S.1.4. Printed Tickets. - A printed ticket issued or stamped by a timing device shall have printed clearly thereon:

(a) the time and day when the service ends and the time and day when the service begins, except that a self-service money-operated device that clearly displays the time of day need not record the time and day when the 

service begins; or

(b) the time interval purchased, and the time and day that the service either begins or ends.

(Amended 1983)

S.2. Marking Requirements, Operating Instructions. - Operating instructions shall be clearly stated on the device.

N. Notes

N.1. Test Method. - A timing device shall be tested with a timepiece with an error of not greater than plus or minus 15 

seconds per 24-hour period. In the test of timing devices with a nominal capacity of 1 hour or less, stopwatches with a 

minimum division of not greater than one-fifth second shall be used. In the test of timing devices with a nominal capacity 

of more than 1 hour, the value of the minimum division on the timepiece shall be not greater than 1 second. Time pieces 

and stopwatches shall be calibrated with standard time signals as described in National Institute of Standards and 

Technology Special Publication 432, NIST Time and Frequency Dissemination Services, or any superseding publication.

(Amended 1978)

N.2. Broadcast Times and Frequencies. - Time and frequency standards are broadcast by the stations listed in 

Table N.2.
5.55. Timing Devices

5-25

Table N.2.* Broadcast Times and Frequencies

Station

Location,

Latitude,

Longitude

Frequency

(MHz)

Times of 

Transmission

(UTC)

WWV

Fort Collins,

Colorado

4041' N

10502' W

2.5

5.0

10.0

15.0

20.0

Continuous

WWVH

Kauai, Hawaii

2159' N

15946' W

2.5

5.0

10.0

15.0

Continuous

CHU

Ottawa, Canada

4518' N

7545' W

 3.330

 7.335

 14.670

Continuous

*From NIST Special Publication 559, "Time and Frequency Users' Manual," 1990.

(Added 1988)

T. Tolerances

T.1. Tolerance Values. - Maintenance and acceptance tolerances for timing devices shall be as follows:

T.1.1. For Timing Devices Other Than Those Specified in T.1.2. and T.1.3. - The maintenance and acceptance 

tolerances shall be:

(a) On Overregistration: 5 seconds for any time interval of 1 minute or more; and

(Amended 1986)

(b) On Underregistration: 6 seconds per indicated minute.

(Amended 1975)

T.1.2. For Time Clocks and Time Recorders. - The maintenance and acceptance tolerances on overregistration and 

under registration shall be 3 seconds per hour, but not to exceed 1 minute per day. 

(Amended 1975) 

T.1.3. On Parking Meters. - The maintenance and acceptance tolerances are shown in Table T.1.3.

Table T.1.3.

Maintenance and Acceptance Tolerances

for Parking Meters

Maintenance and Acceptance Tolerances

Nominal time capacity On overregistration On underregistration

30 minutes or less No tolerance

10 seconds per minute, but not less 

than 2 minutes

Over 30 minutes to and

including 1 hour No tolerance

5 minutes plus 4 seconds per 

minute over 30 minutes

Over 1 hour No tolerance

7 minutes plus 2 minutes per hour 

over 1 hour
5.55. Timing Devices

5-26

T.2. Tests Involving Digital Indications or Representations. - To the tolerances that would otherwise be applied, there 

shall be added an amount equal to one-half the minimum value that can be indicated or recorded.

UR. User Requirements

UR.1. Statement of Rates. - The price in terms of money per unit or units of time for the service dispensed and the 

number of coins the device will accept and be activated by at one time, shall be clearly, prominently, and conspicuously 

displayed.

(Amended 1976)

UR.2. Time Representations. - Any time representation shall be within plus or minus 2 minutes of the correct time in 

effect in the area, except on an individual clock used only for "time out"; in addition, the time indication of the "time-out" 

clock shall be the same as or less than that of the "time-in" clock.

(Amended 1975)
5.56.(a) Grain Moisture Meters

5-27

Sec. 5.56.(a) Grain Moisture Meters

Section 5.56. has been reorganized into two sections. This Section, 5.56.(a), applies to all NTEP grain moisture 

meters. It also applies to any grain moisture meter manufactured or placed into service after January 1, 1998. 

(Code reorganized and renumbered 1996.) 

A. Application

A.1. This code applies to grain moisture meters; that is, devices used to indicate directly the moisture content of cereal 

grain and oil seeds. The code consists of general requirements applicable to all moisture meters and specific requirements 

applicable only to certain types of moisture meters.

A.2. This code does not apply to devices used for in-motion measurement of grain moisture content or seed moisture 

content.

A.3. Type Evaluation - The National Type Evaluation Program will accept for type evaluation only those devices that 

comply with this code. State enforcement will be based upon the effective dates identified with each requirement when 

specific dates are shown.

(Added 1993)

A.4. See also Sec. 1.10; General Code requirements.

S. Specifications

S.1. Design of Indicating, Recording, and Measuring Elements.

S.1.1. Digital Indications and Recording Elements.

(a) Meters shall be equipped with a digital indicating element.

(b) The minimum height for the digits used to display moisture content shall be 10 mm.

(c) Meters shall be equipped with a communication interface that permits interfacing with a recording element 

and transmitting the date, grain type, grain moisture results, and calibration version identification.

(d) A digital indicating element shall not display, and a recording element shall not record, any moisture content 

values before the end of the measurement cycle.

(e) Moisture content results shall be displayed and recorded as percent moisture content, wet basis. 

Subdivisions of this unit shall be in terms of decimal subdivisions (not fractions).

(f) A meter shall not display or record any moisture content values when the moisture content of the grain 

sample is beyond the operating range of the device, unless the moisture representation includes a clear error 

indication (and recorded error message with the recorded representation).

(g) On multi-constituent meters (e.g., meters which also measure grain protein), provision shall be made for 

displaying and recording the constituent label (such as moisture, protein, etc.) to make it clear which 

constituent is associated with each of the displayed and recorded values.

(Added 1995)

(Amended 1993, 1994, 1995 and 1996)

S.1.2. Grain or Seed Kind and Class Selection and Recording. - Provision shall be made for selecting and 

recording the kind and class (as appropriate) of grain or seed to be measured. The means to select the kind and class 

of grain or seed shall be readily visible and the kind and class of grain or seed selected shall be clearly and definitely 

identified. Abbreviations for grain types indicated on the meter must meet the minimum acceptable abbreviations 

listed in Table S.1.2. Meters shall have the capability (i.e., display capacity) of indicating the grain type using a 

minimum of four characters in order to accommodate the four-character abbreviations listed in Table S.1.2. 
5.56.(a) Grain Moisture Meters

5-28

(Amended 1993 and 1995) 

S.1.3. Operating Range. - A meter shall automatically and clearly indicate when the operating range of the meter 

has been exceeded. The operating range shall specify the following:

(a) Temperature Range of the Meter. - The temperature range over which the meter may be used and still 

comply with the applicable requirements shall be specified. The minimum temperature range shall be 10 C 

to 30 C. No moisture value may be displayed when the temperature range is exceeded. An appropriate 

message shall be displayed when the temperature of the meter is outside its specified operating range.

Table S.1.2. Grain Types Considered for Type Evaluation and Calibration

and Minimum Acceptable Abbreviations

Grain Type

Minimum 

Acceptable 

Abbreviation

Grain Type Minimum Acceptable 

Abbreviation

Corn CORN Soybeans SOYB

Durum Wheat

Soft White Wheat

Hard Red Spring Wheat

Hard Red Winter Wheat

Soft Red Winter Wheat

Hard White Wheat

DURW

SWW

HRSW

HRWW

SRWW

HDWW

Two-rowed Barley

Six-rowed Barley

Oats

TRB

SRB

OATS

Sunflower seed (Oil) SUNF Long Grain Rough Rice

Medium Grain Rough Rice

LGRR

MGRR

Grain Sorghum SORG or

MILO

Small oil seeds (under 

consideration)

[Nonretroactive as of January 1, 1998] (Table Added 1993) (Amended 1995, 1998) 

(b) Temperature Range of each Grain or Seed. - The temperature range for each grain or seed for which the 

meter is to be used shall be specified. The minimum temperature range for each grain shall be 0 C to 

40 C. No moisture value may be displayed when the temperature range is exceeded. An appropriate error 

message shall be displayed when the temperature of the grain sample exceeds the specified temperature 

range for the grain.

(c) Moisture Range of the Grain or Seed. - The moisture range for each grain or seed for which the meter is to 

be used shall be specified. A moisture value may be displayed when the moisture range is exceeded if 

accompanied by a clear indication that the moisture range has been exceeded.

(d) Maximum Allowable Meter/Grain Temperature Difference. - The maximum allowable difference in 

temperature between the meter and the sample for which an accurate moisture determination can be made 

shall be specified. The minimum temperature difference shall be 10 C. No moisture value may be 

displayed when the maximum allowable temperature difference is exceeded. An appropriate error message 

shall be displayed when the difference in temperature between the meter and the sample exceeds the 

specified difference. (Added 1993) (Amended 1995)

S.1.4. Value of Smallest Unit. - The display shall permit constituent value determination to both 0.01 percent and 

0.1 percent resolution. The 0.1 percent resolution is for commercial transactions; the 0.01 percent resolution is for 

type evaluation and calibration purposes only, not for commercial purposes.

S.1.5. Operating Temperature.

(a) Warm up period: When a meter is turned on it shall not display or record any usable values until the operating temperature necessary for accurate determination has been attained, or the meter shall bear a 

conspicuous statement adjacent to the indication stating that the meter shall be turned on for a time period 

specified by the manufacturer prior to use.
5.56.(a) Grain Moisture Meters

5-29

(b) A meter shall meet the requirements of T.2. - Tolerance Values when operated in the temperature range of 

10 C to 30 C (50 F to 86 F) or within the range specified by the meter manufacturer.

(c) If the manufacturer specifies a temperature range, the range shall be at least 20 C (36 F).

(Added 1993) (Amended 1995 and 1996)

S.2. Design of Grain Moisture Meters

S.2.1. Minimum Sample Size. - Meters shall be designed to measure the moisture content of representative-size 

grain samples. The minimum allowable sample size used in analysis shall be 100 g or 400 kernels or seeds, 

whichever is smaller.

(Added 1993) (Amended 1995)

S.2.2. Electric Power Supply.

S.2.2.1. Power Supply, Voltage and Frequency.

(a) A meter that operates using alternating current must perform within the tolerances defined in Section 

T.2. - Tolerance Values over the line voltage range 100 V to 130 V, or 200 V to 250 V rms as designed, 

and over the frequency range of 59.5 Hz to 60.5 Hz.

(b) Battery-operated instruments shall not indicate or record values outside the applicable tolerance limits 

when battery power output is excessive or deficient.

S.2.2.2. Power Interruption. - A power interruption shall not cause an indicating or recording element to 

display or record any values outside the applicable tolerance limits.

(Added 1988)

S.2.3 Level Indicating Means. - A meter shall be equipped with a level indicator and leveling adjustments if its 

performance is changed by an amount greater than the applicable tolerance when the meter is moved from a level 

position to a position that is out of level in any upright direction by up to 5 percent (approximately 3 degrees). The 

level-indicating means shall be readable without removing any meter parts requiring a tool. 

(Added 1988) (Amended 1994)

S.2.4. Calibration Integrity

S.2.4.1. Calibration Version. - A meter must be capable of displaying either calibration constants, a unique 

calibration name, or a unique calibration version number for use in verifying that the latest version of the 

calibration is being used to make moisture content determinations.

(Added 1993)(Amended 1995)

S.2.4.2. Calibration Corruption. - If calibration constants are digitally stored in an electronically alterable 

form, the meter shall be designed to make automatic checks to detect corruption of calibration constants. An 

error message must be displayed if calibration constants have been electronically altered.

(Added 1993) (Amended 1995)

S.2.4.3. Calibration Transfer. - The instrument hardware/software design and calibration procedures shall 

permit calibration development and the transfer of calibrations between instruments of like models without 

requiring user slope or bias adjustments.

[Note: Only the manufacturer or the manufacturer's designated service agency may make standardization 

adjustments on moisture meters This does not preclude the possibility of the operator installing manufacturerspecified calibration constants under the instructions of the manufacturer or its designated service agency.] 

Standardization adjustments (not to be confused with grain calibrations) are those physical adjustments or 

software parameters which make meters of like type respond identically to the grain(s) being measured.

[Nonretroactive as of January 1, 1999]

(Added 1994) (Amended 1998)
5.56.(a) Grain Moisture Meters

5-30

S.2.5. Provision for Sealing. - Provision shall be made for applying a security seal in a manner that requires the 

security seal to be broken, or for using other approved means of providing security (e.g., audit trail available at the 

time of inspection as defined in Table S.2.5.*) before any change that affects the metrological integrity of the device 

can be made to any mechanism.

[*Note: Table S.2.5. is Nonretroactive as of January 1, 1999.]

[Note: Zero-setting and test point adjustments are considered to affect metrological characteristics and must be 

sealed.]

(Added 1993) (Amended 1995 and 1997)

S.2.6. Determination of Quantity and Temperature. - The moisture meter system shall not require the operator to 

judge the precise volume or weight and temperature needed to make an accurate moisture determination. External 

grinding, weighing, and temperature measurement operations are not permitted.

(Added 1994)(Amended 1995)

S.3. Accessory Equipment - When the operating instructions for a moisture meter require accessory equipment separate 

from and external to the moisture meter, such equipment shall be appropriate and complete for the measurement.

S.4. Operating Instructions and Use Limitations. - The manufacturer shall furnish operating instructions for the 

device and accessories that include complete information concerning the accuracy, sensitivity, and use of accessory 

equipment necessary in obtaining a moisture content. Operating instructions shall include the following information:

(a) name and address or trademark of the manufacturer;

(b) the type or design of the device with which it is intended to be used;

(c) date of issue;

(d) the kind or classes of grain or seed for which the device is designed to measure moisture content;

(e) the limitations of use, including but not confined to the moisture measurement range, grain or seed temperature, 

maximum allowable temperature difference between grain sample and meter, kind or class of grain or seed, 

moisture meter temperature, voltage and frequency ranges, electromagnetic interferences, and necessary 

accessory equipment.

(Added 1984)

N. Notes

N.1. Testing Procedures. Field evaluation of grain moisture meters shall be performed by one of the following 

methods:

N.1.1. Air Oven Reference Method Transfer Standards. - Official grain samples shall be used as the official 

transfer standards with moisture content values assigned by the reference methods. The reference methods shall be 

the oven drying methods as specified by the USDA GIPSA. Tolerances shall be applied to the average of at least 

three measurements on each official grain sample. Official grain samples shall be clean and naturally moist, but not 

tempered (i.e., water not added).

(Amended 1992 and 2001)

N.1.2. Minimum Test. - A minimum test of a grain moisture meter shall consist of tests:

(a) with samples (need not exceed three) of each grain or seed for which the device is used, and

(b) with samples having at least two different moisture content values within the operating range of the device.

(Amended 1986 and 1989)

N.1.3. Meter to Like-Type Meter Method Transfer Standards. - Properly standardized reference meters using 

National Type Evaluation Program approved calibrations shall be used as transfer standards. A reference meter shall 
5.56.(a) Grain Moisture Meters

5-31

be of the same type as the meter under test. Tests shall be conducted side-by-side using, as a comparison medium, 

grain samples that are clean and naturally moist, but not tempered (i.e., water not added).

(Added 2001)

T. Tolerances

T.1. To Underregistration and to Overregistration. - The tolerances hereinafter prescribed shall be applied to errors of 

under registration and errors of overregistration.

T.2. Tolerances

T.2.1. Air Oven Reference Method. - Maintenance and acceptance tolerances shall be as shown in Table T.2.1. 

Tolerances are expressed as a fraction of the percent moisture content of the official grain sample, together with a 

minimum tolerance.

(Amended 2001)

T.2.2. Meter to Like-Type Meter Method. - Maintenance and acceptance tolerances shall be as shown in Table 

T.2.2. The tolerances shall apply to all types of grain and seed.

(Added 2001)

Table T.2.1. Acceptance and Maintenance 

Tolerances Air Oven Reference Method

Type of Grain 

or Seed

Tolerance Minimum 

Tolerance

Corn, oats, rice, 

sorghum, 

sunflower

0.05 of the percent moisture 

content

0.8 percent 

in moisture 

content

All other cereal 

grains and oil 

seeds

0.04 of the percent moisture 

content

0.7 percent 

in moisture 

content

Table T.2.2. Acceptance and Maintenance 

Tolerances

Meter to Like Type Meter Method

Sample Reference 

Moisture

Tolerance

Up to 22 percent 0.5 percent in moisture 

content

(Amended 2001) (Table Added 2001)

T.3. For Test Weight Per Bushel Indications or Recorded Representations. - The maintenance and acceptance 

tolerances on test weight per bushel indications or recorded representations shall be 0.193 kg/hL or 0.15 lb/bu. The test 

methods used shall be those specified by the USDA GIPSA.

(Amended 1992)

UR. User Requirements

UR.1. Selection Requirements.

UR.1.1. Value of the Smallest Unit on Primary Indicating and Recording Elements. - The resolution of the 

moisture meter display shall be 0.1 percent moisture during commercial use.

UR.1.2. See G-UR.1.2.

UR.2. Installation Requirements. - The grain moisture meter shall be installed in an environment within the range of 

temperature and/or other environmental factors specified in the operating instructions.

UR.3. Use Requirements.

UR.3.1. Operating Instructions. - The operating instructions for the use of the grain moisture meter shall be readily 

available to the user, service technician, and weights and measures official at the place of installation. It shall include 

a list of accessory equipment and the kinds of grain or seed to be measured with the moisture meter.

(Amended 1988)
5.56.(a) Grain Moisture Meters

5-32

UR.3.2. Other Devices not used for Commercial Measurement. - If there are other moisture meters on the 

premises not used for trade or determining other charges for services, these devices shall be clearly and 

conspicuously marked "Not for Use in Trade or Commerce."

UR.3.3. Maintaining Integrity of Grain Samples. - Whenever there is a time lapse (temperature change) between 

taking the sample and testing the sample, means to prevent condensation of moisture or loss of moisture from grain 

samples shall be used. For example, a cold grain sample may be kept in a closed container in order to permit the cold 

grain to come to the operating temperature range of the meter before the grain moisture measurements are made.

UR.3.4. Printed Tickets.

(a) Printed tickets shall be free from any previous indication of moisture content or type of grain or seed 

selected.

(b) The customer shall be given a printed ticket showing the date, grain type, grain moisture results, and 

calibration version identification. The ticket shall be generated by the grain moisture meter system. 

(Amended 1993 and 1995)

UR.3.5. Accessory Devices. - Accessory devices, if necessary in the determination of a moisture content value, shall 

be in close proximity to the moisture meter and allow immediate use.

UR.3.6. Sampling. - A grain sample shall be obtained by following appropriate sampling methods and equipment.

These include, but are not limited to grain probes of appropriate length used at random locations in the bulk, the use 

of a pelican sampler, or other techniques and equipment giving equivalent results. The grain sample shall be taken 

such that it is representative of the lot.

UR.3.7. Location. - See G-UR.3.3. 

UR.3.8. Level Condition. - If equipped with a level indicator, a meter shall be maintained in a level condition.

(Added 1988)

UR.3.9. Current Calibration Data. - Grain moisture determinations shall be made using only the most recently 

published calibration data.

(Added 1988)

UR.3.10. Posting of Meter Operating Range. - The operating range of the grain moisture meter shall be clearly 

and conspicuously posted in the place of business such that the information is readily visible from a reasonable 

customer position. The posted information shall include the following:

(a) The temperature range over which the meter may be used and still comply with the applicable requirements. 

If the temperature range varies for different grains or seed, the range shall be specified for each.

(b) The moisture range for each grain or seed for which the meter is to be used.

(c) The temperature range for each grain or seed for which the meter is to be used.

(d) The maximum allowable difference in temperature that may exist between the meter and the sample for 

which an accurate moisture determination can be made. (Added 1988)
5.56.(a) Grain Moisture Meters

5-33

Table S.2.5. Categories of Device and Methods of Sealing

Categories of Device Method of Sealing

Category 1: No remote configuration 

capability.

Seal by physical seal or two event counters: one for calibration 

parameters (000 to 999) and one for configuration parameters (000 to 

999). If equipped with event counters, the device must be capable of 

displaying, or printing through the device or through another on-site 

device, the contents of the counters.

Category 2: Remote configuration capability, 

but access is controlled by physical hardware.

A device shall clearly indicate that it is in the 

remote configuration mode and shall not be 

capable of operating in the measure mode 

while enabled for remote configuration.

The hardware enabling access for remote communication must be at 

the device and sealed using a physical seal or two event counters; one 

for calibration parameters (000 to 999) and one for configuration 

parameters (000 to 999.) If equipped with event counters, the device 

must be capable of displaying, or printing through the device or 

through another on-site device, the contents of the counters.

Category 3: Remote configuration capability 

access may be unlimited or controlled through 

a software switch (e.g., password).

When accessed remotely for the purpose of 

modifying sealable parameters, the device 

shall clearly indicate that it is in the 

configuration mode and shall not be capable of 

operating in the measuring mode.

An event logger is required in the device; it must include an event 

counter (000 to 999), the parameter ID, the date and time of the 

change , and the new value of the parameter (for calibration changes 

consisting of multiple constants, the calibration version number may be 

used rather than the calibration constants). A printed copy of the 

information must be available through the device or through another 

on-site device. The event logger shall have a capacity to retain records 

equal to twenty-five (25) times the number of sealable parameters in

the device, but not more than 1000 records are required. (Note: Does 

not require 1000 changes to be stored for each parameter.)

Category 3a: No remote capability, but 

operator is able to make changes that affect 

the metrological integrity of the device (e.g., 

slope, bias, etc.) in normal operation.

Same as Category 3 

Category 3b: No remote capability, but

access to metrological parameters is 

controlled through a software switch (e.g., 

password).

Same as Category 3 

[Nonretroactive as of January 1, 1999.] (Amended 1998)

5.56.(b) Grain Moisture Meters

5-35

Sec. 5.56.(b) Grain Moisture Meters

Section 5.56. has been reorganized into two Sections. This Section, 5.56.(b), applies to all non-NTEP grain 

moisture meters manufactured or placed into service before January 1, 1998.

(Code reorganized and renumbered 1996.)

A. Application

A.1. - This code applies to grain moisture meters; that is, devices used to indicate directly or through conversion and/or 

correction tables the moisture content of cereal grain and oil seeds. The code consists of general requirements applicable 

to all moisture meters and specific requirements applicable only to certain types of moisture meters.

A.2. - This code does not apply to devices used for in-motion measurement of grain moisture content or seed moisture 

content.

A.3. - See also Sec. 1.10; General Code requirements.

S. Specifications

S.1. Design of Indicating and Recording Elements and of Recorded Representations.

S.1.1. Primary Elements, General. - A meter shall be equipped with a primary indicating element and may also be 

equipped with a primary recording element. If the meter indicates directly and/or is equipped to record, the meter 

shall indicate and/or record its measurements in terms of percent moisture content, wet basis. Subdivisions of this 

unit shall be in terms of decimal subdivisions (not fractions). If the meter indicates in the conventional scale and 

requires conversion or correction tables, the resulting values after use of such tables shall be in terms of percent 

moisture content, wet basis. Subdivisions of this unit shall be in terms of decimal subdivisions (not fractions).

S.1.2. Digital Indications.

S.1.2.1. Measurement Completion. - A digital indicating element shall not display any values (either moisture 

content or conventional scale) before the end of the measurement cycle.

S.1.3. Graduations.

S.1.3.1. Length. - Graduations shall be so varied in length that they may be conveniently read.

S.1.3.2. Width. - In any series of graduations, the width of a graduation shall in no case be greater than the 

width of the minimum clear interval between graduations, and the width of the main graduations shall be not 

more than 50 percent greater than the width of subordinate graduations. Graduations shall in no case be less than 

0.2 mm (0.008 in) in width.

S.1.3.3. Clear Interval Between Graduations. - The clear interval shall be not less than 0.75 mm (0.03 in) 

between graduations. If the graduations are not parallel, the measurement shall be made:

(a) along the line of relative movement between the graduations at the end of the indicator, or

(b) if the indicator is continuous, at the point of widest separation of the graduations.

S.1.4. Indicators.

S.1.4.1. Symmetry. - The index of an indicator shall be symmetrical with respect to the graduations, at least 

throughout that portion of its length associated with the graduations.

S.1.4.2. Length. - The index of an indicator shall reach to the finest graduations with which it is used, unless the 

indicator and the graduations are in the same plane, in which case the distance between the end of the indicator 
5.56.(b) Grain Moisture Meters

5-36

and the ends of the graduations, measured along the line of the graduations, shall be not more than 1.0 mm 

(0.04 in).

S.1.4.3. Width. - The width of the index of an indicator in relation to the series of graduations with which it is 

used shall be not greater than:

(a) the width of the widest graduation, nor

(b) the width of the minimum clear interval between graduations.

When the index of an indicator extends along the entire length of a graduation, that portion of the index of the 

indicator that may be brought into coincidence with the graduation shall be of the same width as the graduation 

throughout the length of the index that coincides with the graduation.

S.1.4.4. Clearance. - The clearance between the index of an indicator and the graduations shall in no case be 

more than 1.5 mm (0.06 in).

S.1.4.5. Parallax. - Parallax effects shall be reduced to the practicable minimum.

S.1.5. Recording Elements.

S.1.5.1. General. - If a meter is equipped with a recording element, it shall record in terms of percent moisture 

content, wet basis only, and not in terms of conventional scale.

S.1.5.2. Measurement Completion. - A recording element shall not record any values before the end of the 

measurement cycle.

S.1.5.3. Range of Moisture Content. - A recording element shall not record any values when the moisture 

content of the grain sample is beyond the operating range of the device.

S.1.6. Design of Direct Reading Grain Moisture Meters.

S.1.6.1. Grain or Seed Kind and Class Selection and Recording. - Provision shall be made for selecting and 

recording, if equipped to record, the kind and class (as appropriate) of grain or seed to be measured. The means 

to select the kind and class of grain or seed shall be readily visible and the kind and class of grain or seed 

selected shall be clearly and definitely identified in letters (such as Wheat or WHT, HRWW, etc.).

S.1.6.2. Operating Range. - A meter shall automatically and clearly indicate when the operating range of the 

meter has been exceeded or the manufacturer shall:

(a) clearly and conspicuously mark the operating ranges on the meter; or

(b) furnish the operating ranges of the meter and the means to clearly and conspicuously display this 

information on or immediately adjacent to the device.

The operating range shall specify the following:

(a) the temperature range over which the meter may be used and still comply with the applicable 

requirements;

(b) the moisture range for each grain or seed for which the meter is to be used;

(c) the temperature range for each grain or seed for which the meter is to be used; and

(d) the maximum allowable difference in temperature between the meter and the sample for which an 

accurate moisture determination can be made.
5.56.(b) Grain Moisture Meters

5-37

Examples of clearly indicating these conditions include an error indication, flashing the displayed moisture 

value, or blanking the display. 

[Nonretroactive as of January 1, 1989.]

(Amended 1986 and 1988)

S.1.6.3. Value of Smallest Unit.

(a) The value of the minimum indicated or recorded moisture indication shall not be greater than 

0.1 percent.

S.1.7. Electric Power Supply.

S.1.7.1. Power Supply, Voltage and Frequency.

(a) A meter that operates using alternating current must perform within the tolerances defined in Section 

T.2. - Tolerance Values over the line voltage range 100 V to 130 V, or 200 V to 250 V rms as designed, 

and over the frequency range of 59.5 Hz to 60.5 Hz.

(b) Battery-operated instruments shall not indicate or record values outside the applicable tolerance limits 

when battery power output is excessive or deficient.

[Nonretroactive as of January 1, 1989.]

S.1.7.2. Power Interruption. - A power interruption shall not cause an indicating or recording element to 

display or record any values outside the applicable tolerance limits.

[Nonretroactive as of January 1, 1989.]

(Added 1988)

S.1.8. Level Indicating Means. A meter shall be equipped with a level indicator and leveling adjustments if its 

performance is changed by an amount greater than the applicable tolerance when the meter is moved from a level 

position to a position that is out of level in any upright direction by up to 5 percent (approximately 3 degrees).

The level-indicating means shall be readable without removing any meter parts requiring a tool. [Nonretroactive as 

of January 1, 1989.]

(Added 1988) (Amended 1994)

S.1.9. Operating Temperature.

(a) A meter shall not display or record any usable values until the operating temperature necessary for 

accurate determination has been attained, or the meter shall bear a conspicuous statement adjacent to the 

indication stating that the meter shall be turned on for a time period specified by the manufacturer prior to 

use.

(b) A meter shall meet the requirements of T.2. - Tolerance Values when operated in the temperature range of 

2 C to 40 C (35 F to 104 F) or within the range specified by the meter manufacturer.

(c) If the manufacturer specifies a temperature range, the range shall be at least 10 C (20 F) and shall be 

marked on the device.

[Nonretroactive as of January 1, 1989.](Added 1988)

S.2. Design of Measuring Elements.

S.2.1. Design of Zero-Setting and Test Point Mechanisms. - If a grain moisture meter is equipped with a zero 

setting and/or test point mechanism(s), this (these) mechanism(s) shall be adjustable only with a tool outside and 

entirely separate from this mechanism or enclosed in a cabinet. This requirement shall not apply to manual 

operations that the operator must make (following operating instructions) in order to obtain a meter reading on a 

grain sample.
5.56.(b) Grain Moisture Meters

5-38

S.2.2. Provision for Sealing. - Provision shall be made for applying a security seal in a manner that requires the 

security seal to be broken before an adjustment can be made to any component of the grain moisture meter that is set 

by the manufacturer or authorized service representative and not intended to be adjusted by the user.

S.3. Accessory Equipment. - When the operating instructions for a moisture meter require accessory equipment separate 

from and external to the moisture meter, such equipment shall be appropriate and complete for the measurement.

S.3.1. Grain-Test Scale. - If the moisture meter requires the weighing of the grain sample, the weighing device shall 

meet the requirements of the General Code and those applicable portions of the Scales Code.

S.3.2. Thermometers or Other Temperature Sensing Equipment. 

(a) The temperature sensing equipment or thermometer shall be designed to be in direct contact with a grain 

sample in a closed container. It is acceptable to insert thermometer through a small hole in the lid of the 

container used to hold the grain sample.

(b) A separate thermometer or other temperature sensing equipment shall have temperature divisions not greater 

than the temperature increments used by the manufacturer in the correction table.

(Amended 1988)

S.3.3. Conversion and Correction Tables. - Conversion and correction tables, charts, graphs, slide rules, or other 

apparatus to convert the conventional scale values read from a moisture meter to moisture content values, if such 

apparatus is required, shall be appropriate and correct for the moisture meter being used and shall be marked with the 

following information:

(a) name and address or trademark of the manufacturer;

(b) the type or design of the device with which it is intended to be used;

(c) date of issue;

(d) the kind or classes of grain or seed for which the device is designed to measure moisture content;

(e) the limitations of use, including but not confined to the moisture measurement range, grain or seed temperature, kind or class of grain or seed, moisture meter temperature, voltage and frequency ranges, electromagnetic interferences, and necessary accessory equipment; but

(f) values exceeding any measurement range shall not be included.

(Added 1984)

S.3.4. Operating Instructions and Use Limitations. - Operating instructions shall be furnished by the manufacturer 

with each device with all of the information required by paragraph S.3.3. Complete information concerning the 

accuracy, sensitivity, and use of accessory equipment (e.g., test weight per bushel equipment, thermometer, etc.) 

necessary in obtaining a moisture content shall be included.

N. Notes

N.1. Testing Procedures.

N.1.1. Transfer Standards. - Official grain samples shall be used as the official transfer standards with moisture 

content values assigned by the reference methods. The reference methods shall be the oven drying methods as 

specified by the USDA GIPSA. Tolerances shall be applied to the average of at least three measurements on each 

official grain sample. Official grain samples shall be clean and naturally moist, but not tempered (i.e., water not 

added).

(Amended 1992)

N.1.2. Minimum Test.- A minimum test of a grain moisture meter shall consist of tests:
5.56.(b) Grain Moisture Meters

5-39

(a) with samples (need not exceed three) of each grain or seed for which the device is used, and

(b) with samples having at least two different moisture content values within the operating range of the device.

(Amended 1986, 1989)

N.1.3. Temperature Measuring Equipment. - The accuracy of accessory temperature measuring equipment shall 

be determined by comparison with a calibrated temperature sensor, such as a total immersion thermometer with 

0.1 C (0.2 F) subdivisions, indicating over a range of from 0 C to 40 C (32 F to 104 F) with a maximum error 

of ±0.1 C (0.2 F). Tests shall be conducted at two temperatures using liquid baths (e.g., ice water and room 

temperature water). The two temperatures selected shall not exceed the range of temperatures identified in the 

moisture meter operating instructions. (Amended 1988)

T. Tolerances1

T.1. To Underregistration and to Overregistration. - The tolerances hereinafter prescribed shall be applied to errors of 

under registration and errors of overregistration.

T.2. Tolerance Values. - Maintenance and acceptance 

tolerances shall be as shown in Table T.2. Tolerances are 

expressed as a fraction of the percent moisture content of the 

official grain sample, together with a minimum tolerance.

T.3. For Test Weight Per Bushel Indications or Recorded 

Representations. - The maintenance and acceptance 

tolerances on test weight per bushel indications or recorded 

representations shall be 0.193 kg/hL or 0.15 lb/bu. The test 

methods used shall be those specified by the USDA GIPSA.

(Amended 1992)

T.4. Thermometers or Other Temperature Sensing Equipment. - The tolerance for a separate thermometer or 

temperature sensing equipment used to determine the temperature of grain samples for the purpose of making temperature 

corrections in moisture determinations shall be ±0.5 C (1 F). (Added 1988)

UR. User Requirements

UR.1. Selection Requirements.

UR.1.1. Value of the Smallest Unit on Primary Indicating and Recording Elements. - The value of the smallest 

unit on a moisture meter, whether the moisture meter reads directly in terms of moisture content, or when the 

conventional scale unit is converted or corrected to moisture content, shall be equal to or less than 0.1 percent.

UR.1.2. See G-UR.1.2.

UR.2. Installation Requirements. - The grain moisture meter shall be installed in an environment within the range of 

temperature and/or other environmental factors specified (a) in the operating manual, and (b) on the conversion or 

correction tables if such tables are necessary for the operation of the device.

UR.3. Use Requirements.

UR.3.1. Operating Instructions. - The operating instructions for the use of the grain moisture meter shall be readily 

available to the user, service technician, and weights and measures official at the place of installation. It shall include 

a list of accessory equipment, conversion and correction charts if any are required to obtain moisture content values, 

and the kinds of grain or seed to be measured with the moisture meter.

(Amended 1988)

Table T.2. Acceptance and Maintenance Tolerances for 

Grain Moisture Meters

Type of grain 

or seed Tolerance MinimumTolerance

Corn, oats, 

rice, sorghum, 

sunflower

0.05 of the percent 

moisture content

0.8 percent in 

moisture

content

All other cereal 

grains and oil 

seeds

0.04 of the percent 

moisture content

0.7 percent in 

moisture

content

_______________________________________________________________________________________________ 1 These tolerances do not apply to tests in which grain moisture meters are the transfer standards.
5.56.(b) Grain Moisture Meters

5-40

UR.3.2. Other Devices not used for Commercial Measurement. - If there are other moisture meters on the

premises not used for trade or determining other charges for services, these devices shall be clearly and 

conspicuously marked "Not for Use in Trade or Commerce."

UR.3.3. Maintaining Integrity of Grain Samples. - Whenever there is a time lapse (temperature change) between 

taking the sample and testing the sample, means to prevent condensation of moisture or loss of moisture from grain 

samples shall be used. For example, a cold grain sample may be kept in a closed container in order to permit the cold 

grain to come to the operating temperature range of the meter before the grain moisture measurements are made.

UR.3.4. Printed Tickets. - Printed tickets shall be free from any previous indication of moisture content or type of 

grain or seed selected.

UR.3.5. Accessory Devices. - Accessory devices, if necessary in the determination of a moisture content value, shall 

be in close proximity to the moisture meter and allow immediate use.

UR.3.6. Sampling. - A grain sample shall be obtained by following appropriate sampling methods and equipment.

These include, but are not limited to, grain probes of appropriate length used at random locations in the bulk, the use 

of a pelican sampler, or other techniques and equipment giving equivalent results. The grain sample shall be taken 

such that it is representative of the lot.

UR.3.7. Location. - See G-UR.3.3. - Position of Equipment.

UR.3.8. Level Condition. - If equipped with a level indicator, a meter shall be maintained in a level condition.

(Added 1988)

UR.3.9. Operating Limitation. - Unless otherwise specified by the meter manufacturer, moisture determinations 

shall not be made when the difference in temperatures between the grain sample and the meter exceeds 10 C 

(20 F).

(Added 1988)

UR.3.10. Current Calibration Chart or Data. - Grain moisture determinations shall be made using only the most 

recently published calibration charts or calibration data.

(Added 1988)

UR.3.11. Posting of Meter Operating Range. - The operating range of the grain moisture meter shall be clearly 

and conspicuously posted in the place of business such that the information is readily visible from a reasonable 

customer position. The posted information shall include the following:

(a) The temperature range over which the meter may be used and still comply with the applicable requirements. 

If the temperature range varies for different grains or seed, the range shall be specified for each.

(b) The moisture range for each grain or seed for which the meter is to be used.

(c) The temperature range for each grain or seed for which the meter is to be used.

(d) The maximum allowable difference in temperature that may exist between the meter and the sample for 

which an accurate moisture determination can be made.

(Added 1988)
5.57. Near-Infrared Grain Analyzers

5-41

Sec. 5.57. Near-Infrared Grain Analyzers1

A. Application

A.1. - This code applies to near-infrared (NIR) grain analyzers; that is, devices used to indicate the constituent values 

(other than moisture content) of grain using near-infrared reflectance or transmittance technology. These instruments 

may analyze either whole grain or ground grain samples. The code consists of general requirements applicable to all NIR 

analyzers and specific requirements applicable only to certain types of NIR analyzers, grain types, or grain constituents. 

In addition to meeting the requirements of this code, a whole grain NIR analyzer that displays a measured moisture value 

must also comply with the requirements of the Grain Moisture Meters Code. 

(Added 2001)

A.2. - This code does not apply to devices used for in-motion measurement of grain constituent values.

A.3. Calibrations. - The National Type Evaluation Program Certificate of Conformance (CC) shall indicate the native 

moisture basis of each calibration. The "native" moisture basis is the default moisture basis of the sealable constituent 

calibration (or constituent calibration pair when a non-displayed moisture calibration is also involved). If an NIR 

analyzer uses a self-generated moisture measurement internally but does NOT display or record a moisture value, the 

moisture calibration shall be considered to be a part of the constituent calibration. For such calibrations, the CC shall 

state: "Includes non-displayed moisture calibration." Changes to any part of such calibrations shall require changes to the 

CC.

(Added 2001)

A.4. - See also Sec. 1.10; General Code requirements.

S. Specifications

S.1. Design of Indicating, Recording, and Measuring Elements.

S.1.1. Digital Indications and Recording Elements.

(a) Analyzers shall be equipped with a digital indicating element.

(b) The minimum height for the digits used to display constituent values shall be 10 mm.

(c) Analyzers shall be equipped with a communication interface that permits interfacing with a recording 

element and transmitting the date, grain type or class, constituent values, the moisture basis for each 

constituant value (except moisture), and calibration version identification.

(Amended 2001)

(d) A digital indicating element shall not display, and a recording element shall not record, any constituent 

value before the end of the measurement cycle.

(e) Constituent content shall be recorded and displayed as percent of total mass. The moisture basis shall also 

be recorded and displayed for each constituent content result (except moisture). If a whole grain analyzer 

that is calibrated to display results on an "as is" moisture basis does NOT display or record a moisture 

value, it must clearly indicate that results are expressed on an "as is" moisture basis. Ground grain

analyzers must ALWAYS display and record a moisture measurement for "as is" content results (except 

moisture).

(Amended 2001)

(f) An analyzer shall not display or record any constituent value that is beyond the operating range of the 

device unless the constituent value representation includes a clear error indication (and recorded error 

message with the recorded representation).

 1 The Near Infrared Grain Analyzer Code was updated from a tentative code to a permanent code in 2002, effective 

January 1, 2003.
5.57. Near-Infrared Grain Analyzers

5-42

(g) If an NIR analyzer is used to determine a moisture value, either to determine the moisture of an "as is" 

constituent content measurement or to convert from one moisture basis to another, the moisture 

measurement must be concurrent with the measurement of other constituents.

(Added 2001)

[Nonretroactive as of January 1, 2003]

S.1.2. Selecting Grain Class and Constituent. -

Provision shall be made for selecting, and recording the 

type or class of grain and the constituent(s) to be 

measured. The means to select the grain type or class 

and constituent(s) shall be readily visible and the type or 

class of grain and constituent(s) selected shall be clearly 

and definitely identified in letters (such as HRWW, 

HRSW, etc. or PROT, etc.). A symbol to identify the 

display of the type or class of grain and constituent(s) 

selected is permitted provided that it is clearly defined 

adjacent to the display. Minimum acceptable 

abbreviations are listed in Table S.1.2. Meters shall 

have the capability (i.e., display capacity) of indicating 

the grain type using a minimum of four characters in 

order to accommodate the abbreviations listed in Table 

S.1.2.

[Nonretroactive as of January 1, 2003]

S.1.3. Operating Range. - An analyzer shall automatically and clearly indicate when the operating range of the 

device has been exceeded. The statement of the operating range shall be specified in the operator's manual and shall 

operate as follows:

(a) The ambient temperature range over which the analyzer may be used and still comply with the applicable 

requirements shall be specified. The minimum temperature range shall be 10 C to 30 C. No constituent 

value may be displayed when the temperature range is exceeded. An appropriate error message shall be 

displayed when the temperature of the analyzer is outside its specified operating range.

(b) The constituent range at the moisture basis specified in Table N.1.1. shall be specified for each grain or 

seed for which the analyzer is to be used. A constituent value may be displayed when the constituent range 

is exceeded if accompanied by a clear indication that the constituent range has been exceeded.

(Amended 2001)

(c) For whole grain analyzers only, the temperature range shall be specified for each grain or seed for which 

an analyzer is to be used. The minimum temperature range for each grain shall be 10 C to 30 C. No 

constituent value may be displayed when the temperature range is exceeded. An appropriate error message 

shall be displayed when the temperature of the grain sample exceeds the temperature range for the grain. 

The requirements of this subsection (c) are not applicable to ground grain analyzers.

(d) For whole grain analyzers, the maximum allowable difference in temperature between the instrument 

environment (ambient temperature) and the sample for which an accurate constituent determination can be 

made shall be specified. The minimum temperature range shall cover at least 10 C. No constituent value 

may be displayed when the maximum allowable temperature difference is exceeded. An appropriate error 

message shall be displayed when the difference between the ambient temperature and the sample 

temperature exceeds the specified difference. The requirements of this subsection (d) are not applicable to 

ground grain analyzers.

[Nonretroactive and effective as of January 1, 2003]

Table S.1.2. Grain Types Considered for Type Evaluation and 

Calibration

and Minimum Acceptable Abbreviations

Grain Type Minimum Acceptable Abbreviation

Durum Wheat

Hard Red Spring Wheat 

Hard Red Winter Wheat

Hard White Wheat

Soft Red Winter Wheat

Soft White Wheat

Soybeans

Two-rowed Barley

Six-rowed Barley

Corn

DURW

HRSW

HRWW

HDWW

SRWW

SWW

SOYB

TRB

SRB

CORN

[Nonretroactive as of January 1, 2003]

(Table Amended 2001)
5.57. Near-Infrared Grain Analyzers

5-43

S.1.4. Operating Temperature:

(a) An analyzer shall not display or record any usable values until the internal operating temperature necessary 

to meet tolerance requirements has been attained, or the analyzer shall bear a conspicuous statement 

adjacent to the indication stating that the analyzer shall be turned on for a time period specified by the 

manufacturer prior to use.

(b) If an instrument does not meet tolerance requirements because there is an upper internal operating 

temperature limit that could be exceeded when operating within the ambient temperature range specified by 

the manufacturer, then a means of sensing and indicating an over-temperature condition must be provided.

[Nonretroactive as of January 1, 2003]

S.1.5. Value of Smallest Unit. - The display shall permit constituent value determination to both 0.01 percent and 

0.1 percent resolution. The 0.1 percent resolution is for commercial transactions; the 0.01 percent resolution is for 

calibration purposes only, not for commercial purposes.

[Nonretroactive as of January 1, 2003]

S.2. Design of NIR Analyzers

S.2.1. Minimum Sample Size. - Analyzers shall be designed to measure constituent values of representative size 

grain samples. The minimum allowable sample size used in analysis shall be 20 g.

[Nonretroactive as of January 1, 2003]

S.2.2. Electric Power Supply.

S.2.2.1. Power Supply, Voltage and Frequency. - An analyzer that operates using alternating current must 

perform within tolerance requirements over the line voltage range 100 V to 130 V and over the frequency range 

of 59.5 Hz to 60.5 Hz.

[Nonretroactive as of January 1, 2003]

S.2.2.2. Power Interruption. - A power interruption shall not cause an indicating or recording element to 

display or record any values outside the applicable tolerance limits.

[Nonretroactive as of January 1, 2003] 

S.2.3. Level Indicating Means. - Analyzers shall be equipped with a level indicator and leveling adjustments if its 

performance is changed by an amount greater than the tolerance requirement when the instrument is moved from a 

level position into a position that is out of level in any upright direction by up to 5 percent (approximately 3 degrees). 

The level-indicating means shall be readable without removing any instrument parts requiring a tool.

[Nonretroactive as of January 1, 2003]

S.2.4. Environmental Conditions. - Instrument optics and electronics must be protected from exposure to dust by 

either sealing these areas or by protecting them with a dust filtration system suitable for the removal of air-borne 

grain dust.

[Nonretroactive as of January 1, 2003]

S.2.5. Calibration Transfer and Verification.

S.2.5.1. Calibration Transfer. - The instrument hardware/software design and calibration procedures shall 

permit calibration development and the mathematical transfer of calibrations between instruments of like 

models.

Note: Only the manufacturer or the manufacturer's designated service agency may make calibration transfer or 

slope adjustments on near-infrared grain analyzers and, except for instrument failure and repair, only during a 

prescribed period of time during the year. This does not preclude the possibility of the operator installing the 

manufacturer-specified calibration constants or standardization parameters under the instructions of the 

manufacturer or the manufacturer's designated service agency. Nor does it preclude operator bias adjustments 

when made under the conditions specified in UR.2.8.
5.57. Near-Infrared Grain Analyzers

5-44

[Nonretroactive and effective as of January 1, 2003]

(Note added 1995) (Amended 1995)

S.2.5.2. Calibration Version. - An instrument must be capable of displaying either calibration constants, a 

unique calibration name, or a unique calibration version number for use in verifying that the latest version of the 

calibration is being used to make constituent determinations, and that the appropriate instrument settings have 

been made for the calibration being used.

[Nonretroactive as of January 1, 2003]. 

(Amended 2001)

S.2.5.3. Calibration Corruption. - If calibration constants are digitally stored in an electronically alterable 

form, the analyzer shall be designed to make automatic checks to detect corruption of calibration constants. An 

error message must be displayed if calibration constants have been electronically altered.

[Nonretroactive as of January 1, 2003]. 

S.2.6. Provision for Sealing. - An event logger is required in the device; it must include an event counter (000 to 

999), the parameter ID, the date and time of the change, and the new value of the parameter (for calibration changes 

consisting of multiple constants, the calibration version number may be used rather than the calibration constants.)

A printed copy of the information must be available through the device or through another on-site device. The event 

logger shall have a capacity to retain records equal to twenty-five (25) times the number of sealable parameters in 

the device, but not more than 1000 records are required. (Note: Does not require 1000 changes to be stored for 

each parameter.)

[Nonretroactive as of January 1, 2003]

(Amended 1997)

S.3. Accessory Equipment. When the operating instructions for a NIR analyzer require accessory equipment separate 

from and external to the analyzer, such equipment shall be appropriate and complete for the measurement.

[Nonretroactive as of January 1, 2003]

S.3.1. Grinders. - The make and model of grinder used for ground grain NIR analyzers must be specified by the 

manufacturer and required as auxiliary equipment in the determination of constituent values for applicable grain 

types.

[Nonretroactive as of January 1, 2003]

S.4. Operating Instructions and Use Limitations. - The manufacturer shall furnish operating instructions for the device 

and accessories that include complete information concerning the accuracy, sensitivity, and use of accessory equipment 

necessary in obtaining a constituent value. Operating instructions shall include the following information:

(a) name and address or trademark of the manufacturer;

(b) the type or design of the device for which the operating instructions are intended to be used;

(c) date of issue;

(d) the kind or classes of grain or seed for which the device is designed to measure constituent values; and

(e) the limitations of use, including but not limited to constituent range, grain or seed temperature, kind or class of 

grain or seed, instrument temperature, voltage and frequency ranges, electromagnetic interferences, and 

necessary accessory equipment.

[Nonretroactive as of January 1, 2003]

N. Notes

N.1. Testing Procedures.

N.1.1. Field Inspection. - Whole grain samples shall be used as the official field inspection standards. Five samples 

per grain type or class shall be used to check instrument performance. Each sample will be analyzed once. One of 
5.57. Near-Infrared Grain Analyzers

5-45

the samples will be analyzed an additional four 

times to test instrument repeatability. For ground 

grain instruments, the ground sample will be 

repacked four times. A new grind is not required. 

Test results must be converted to the standard 

moisture bases shown in Table N.1.1. before 

applying the tolerances of Table T.2. Test results 

on whole grain analyzers that produce results on an 

"as is" basis without displaying or recording a 

moisture value shall be converted to the standard 

moisture bases shown in Table N.1.1. using sample 

moisture values determined with the facility's 

moisture meter (which must be certified for 

commercial use).

(Amended 2001)

Constituent values shall be assigned to test samples 

by the Grain Inspection, Packers and Stockyards 

Administration (GIPSA). Tolerances shall be 

applied to individual sample measurements, the 

average of individual measurements on each of the 

five test samples, and the maximum difference 

(range) in results for five analyses on one of the 

test samples.

(Amended 2001)

N.1.2. Standard Reference Samples. - Reference samples used for field inspection purposes shall be clean and 

selected to reasonably represent the constituent range. These samples shall be selected such that the difference 

between constituent values obtained using the GIPSA standard reference method and an official GIPSA NIR grain 

analyzer does not exceed one-half of the acceptance tolerance shown in Table T.2. for individual test samples or 

0.375 times the acceptance tolerance shown for the average of five samples.

(Amended 2001)

T. Tolerances

T.1. To Underregistration and to Overregistration. - The tolerances hereinafter prescribed shall be applied to errors of 

underregistration and errors of overregistration and shall be based on constituent values expressed at the moisture bases 

shown in Table N.1.1.

(Amended 2001)

T.2. Tolerance Values. - Acceptance and maintenance tolerances shall be equal. Tolerances for individual samples and 

the average for five samples are as shown in Table T.2.

UR. User Requirements

UR.1. Installation Requirements. - The NIR analyzer shall be installed in an environment within the range of 

temperature and/or other environmental factors specified in the operating manual.

UR.2. User Requirements.

UR.2.1. Operating Instructions. - The operating instructions for the NIR analyzer shall be readily available to the 

user, service technician, and weights and measures official at the place of installation. It shall include a list of 

accessory equipment if any are required to obtain constituent values, and the type or class of grain to be measured 

with the NIR analyzer. If an NIR analyzer has the capability, the user is permitted to select the moisture basis to be 

used on any measurement.

(Amended 2001)

Table N.1.1. Constant Moisture Basis for Type Evaluation 

and Field Inspection

Grain Type or 

Class

Constituents(s) Moisture Basis

Durum Wheat, 

Hard Red Spring 

Wheat, Hard Red 

Winter Wheat, 

Hard White 

Wheat, Soft Red 

Winter Wheat, 

Soft White Wheat

Protein 12 percent

Soybeans Protein

Oil

13 percent

Two-rowed Barley

Six-rowed Barley

Protein 0 percent (dry basis)

Corn Protein

Oil

Starch

0 percent (dry basis)

Nonretroactive as of January 1, 2003]

(Table Added 2001)
5.57. Near-Infrared Grain Analyzers

5-46

UR.2.2. Other Devices not used for Commercial Measurement. - If there are other NIR analyzers on the premises 

not used for trade or determining other charges for services, these devices shall be clearly and conspicuously marked 

"Not for Use in Trade or Commerce."

Table T.2. Acceptance and Maintenance Tolerances 

for NIR Grain Analyzers

Type of Grain Constituent

Individual 

Samples

(percent)

Average 

for Five 

Samples

(percent)

Range for 

Five 

Retests

(percent)

Durum Wheat, Hard Red Spring Wheat, 

Hard Red Winter Wheat, Hard White 

Wheat, Soft Red Winter Wheat, Soft 

White Wheat

protein 0.60 0.40 0.40

Soybeans protein 0.80 0.60 0.60

oil 0.70 0.50 0.50

Two-rowed Barley

Six-rowed Barley protein 0.70 0.50 0.50

Corn

protein 0.80 0.60 0.60

oil 0.70 0.50 0.50

starch 1.00 0.80 0.80

(Amended 2001)

UR.2.3. Printed Tickets. -

(a) Printed tickets shall be free from any previous indication of constituent or grain type selected. The printed 

ticket shall indicate constituent values and the moisture basis associated with each constituent value (except 

moisture). If the analyzer is calibrated to display results on an "as is" moisture basis and does NOT display 

or record a moisture value, the ticket must clearly indicate that results are expressed on an "as is" moisture 

basis. 

(Amended 2001)

(b) The customer shall be given a printed ticket showing the date, grain type or class, constituent results, and 

calibration version identification. If the analyzer converts constituent results to a manually entered 

moisture basis, the "native" concentration and the "native" moisture basis must appear on the printed ticket 

in addition to the converted results and the manually entered moisture basis. If the manually entered

moisture basis is intended to be the moisture value for an "as is" constituent concentration measurement, 

that moisture value must have been obtained on the same sample and must have been measured on a 

moisture meter certified for commercial use. The information presented on the ticket shall be arranged in a 

consistent and unambiguous manner. The ticket shall be generated by the near-infrared grain analyzer 

system.

[Nonretroactive as of January 1, 2003]

(Amended 2001)

UR.2.4. Grinders. - Place grinders in a separate room from the NIR analyzer to avoid instrument contamination. If 

a separate room is not available, the grinder may be in the same room with the NIR analyzer provided the grinder is 

not placed within 1 meter of the air intake on the NIR.

UR.2.5. Sampling. - Samples shall be obtained by following appropriate sampling methods and equipment. These 

include, but are not limited to grain probes of appropriate length used at random locations in the bulk, the use of a 

pelican sampler, or other techniques and equipment giving equivalent results. The sample shall be taken such that it 

is representative of the lot. If an NIR analyzer permits user entry of the moisture value for an "as is" constituent 

measurement, that moisture value must have been obtained on the same sample and must have been measured on a 

moisture meter certified for commercial use.

(Amended 2001)

UR.2.6. Level Condition. - If equipped with a level indicator, an analyzer shall be maintained in a level condition.
5.57. Near-Infrared Grain Analyzers

5-47

UR.2.7. Operating Limitation. - Constituent determinations shall not be made when the difference in temperatures 

between the grain sample and the instrument environment (ambient temperature) exceeds manufacturer 

recommendations.

UR.2.8. Slope and Bias Adjustments. - Bias changes shall be made only on the basis of tests run on a current set of 

Standard Reference Samples (SRS) traceable to GIPSA Master Instruments.2

(Amended 1995)

 A written explanation and record of all 

calibration changes, including those changes made by a manufacturer or the manufacturer's designated service 

agency, shall be maintained. The log shall indicate the date and magnitude of changes in bias and slope constants 

and the instrument serial number. A Calibration Adjustment Data Sheet for each log entry shall be available for 

inspection upon request by the field inspector. Data Sheets shall be retained by the user for a period of no less than 

18 months following any calibration adjustment. The Data Sheet must show: Date of test and adjustment, serial 

number of the instrument, calibration identification, the nature of the adjustment, the unique identification number 

and source of sample sets used, and, for each sample in the set, reference values, initial instrument results (except in 

the cases of instrument failure and repair), and instrument results after calibration adjustment or instrument repair.

 2 Established error must be known.
5.58. Multiple Dimension Measuring Devices

5-49

Section 5.58. Multiple Dimension Measuring Devices 

This tentative code has only a trial or experimental status and is not intended to be enforced. The requirements are 

designed for study prior to the development and adoption of a final Code for Multiple Dimension Measuring Devices. 

If upgraded to become a permanent code, all requirements, except those for tolerances, will be non-retroactive as of 

the effective date of the permanent code; tolerance requirements will apply retroactively as of the effective date of the 

permanent code.

(Tentative code added 1995)

A. Application

A.1. General. - This code applies to dimension and volume measuring devices used for determining the dimensions 

and/or volume of objects for the purpose of calculating freight, storage, or postal charges based on the dimensions and/or 

volume occupied by the object.

A.2. Insofar as they are clearly applicable, the provisions of this code apply also to devices designed to make multiple 

measurements automatically to determine a volume for other applications as defined by General Code paragraph G-A.1.

A.3. In addition to the requirements of this code, multiple dimension measuring devices shall meet the requirements of 

Section 1.10. General Code.

A.4. This code does not apply to:

(a) devices designed to indicate automatically (with or without value-computing capabilities) the length of fabric passed 

through the measuring elements (see Sec. 5.50. for Fabric-Measuring Devices);

(b) devices designed to indicate automatically the length of cordage, rope, wire, cable, or similar flexible material passed 

through the measuring elements (see Sec. 5.51. for Wire- and Cordage-Measuring Devices); or

(c) any linear measure, measure of length, or devices used to measure individual dimensions for the purpose of assessing 

a charge per unit of measurement of the individual dimension (see Sec. 5.52. for Linear Measures).

A.5. Type Evaluation. - The National Type Evaluation Program will accept for type evaluation only those devices that 

comply with all requirements of this code.

S. Specifications

S.1. Design of Indicating and Recording Elements and of Recorded Representations.

S.1.1. Zero or Ready Indication.

(a) Provision shall be made to indicate or record either a zero or ready condition.

(b) A zero or ready condition may be indicated by other than a continuous digital zero indication, provided that an 

effective automatic means is provided to inhibit a measuring operation when the device is in an out-of-zero or 

non-ready condition.

S.1.2. Digital Indications. - Indicated and recorded values shall be presented digitally.

S.1.3. Negative Values. - Except when in the tare mode, negative values shall not be indicated or recorded.

S.1.4. Dimensions Indication. - If in normal operation the device indicates or records only volume, a testing mode 

shall be provided to indicate dimensions for all objects measured.

S.1.5. Value of Dimension/Volume Division Units. -The value of a device division "d" expressed in a unit of 

dimension shall be presented in a decimal format with the value of the division expressed as:

 
5.58. Multiple Dimension Measuring Devices

5-50

(a) 1, 2, or 5; or 

(b) a decimal multiple or submultiple of 1, 2, or 5; or

(c) a binary submultiple of a specific inch-pound unit of measure.

Examples: device divisions may be 0.01, 0.02, 0.05; 0.1, 0.2, or 0.5; 1, 2, or 5; 10, 20, 50, or 100; 0.5, 0.25, 0.125, 

0.0625, etc.

S.1.5.1. For Indirect Sales. - In addition to the values specified in S.1.5., the value of the division may be 

0.3 inch and 0.4 inch.

S.1.6. Customer Indications and Recorded Representations. - Multiple dimension measuring systems must 

provide information as specified in Table S.1.6. (See Table Appendix at the end of this code.)

S.1.7. Minimum Lengths. - The minimum length to be measured by a device is 12 divisions. The manufacturer 

may specify a longer minimum length.

S.1.8. Indications Below Minimum and Above Maximum. - Except for entries of tare, when objects are smaller 

than the minimum dimensions identified in paragraph S.1.7. or larger than 105 percent of the maximum dimensions 

and/or volume marked on the device, the indicating or recording element shall either:

(a) not display or record any usable values, or

(b) identify the displayed or recorded representation with an error indication.

S.1.9. Operating Temperature. - An indicating or recording element shall not display nor record any usable values 

until the operating temperature necessary for accurate measuring and a stable zero reference or ready condition have 

been attained.

S.1.10. Adjustable Components. - Adjustable components shall be held securely in adjustment and, except for a 

zeroing mechanism (when applicable), shall be located within the housing of the element.

S.1.11. Provision for Sealing.

(a) A device shall be designed with provision(s) for applying a security seal that must be broken, or for using other 

approved means of providing security (e.g., data change audit trail available at the time of inspection), before 

any change that detrimentally affects the metrological integrity of the device can be made to any measuring 

element.

(b) Audit trails shall use the format set forth in Table S.1.11. (See Table Appendix at the end of this code.)

S.2. Design of Zero and Tare.

S.2.1. Zero or Ready Adjustment. - A device shall be equipped with means by which the zero reference or ready 

condition can be adjusted, or the zero reference or ready condition shall be automatically maintained. The zero 

reference or ready control circuits shall be interlocked so that their use is prohibited during measurement operations.

S.2.2. Tare. - The tare function shall operate only in a backward direction (that is, in a direction of underregistration) 

with respect to the zero reference or ready condition of the device. The value of the tare division or increment shall 

be equal to the division of its respective axis on the device. There shall be a clear indication that tare has been taken.

S.3. Systems with Two or More Measuring Elements. - A multiple dimension measuring system with a single 

indicating or recording element, or a combination indicating-recording element, that is coupled to two or more measuring 

elements with independent measuring systems, shall be provided with means to prohibit the activation of any measuring 

element (or elements) not in use, and shall be provided with automatic means to indicate clearly and definitely which 

measuring element is in use.
5.58. Multiple Dimension Measuring Devices

5-51

S.4. Marking Requirements. [See also G-S.1., G-S.4., G-S.5.2.5., G-S.6., G-S.7., G-UR.2.1.1., and G-UR.3.1.]

S.4.1. Multiple Dimension Measuring Devices, Main Elements, and Components of Measuring Devices. -

Multiple dimension measuring devices, main elements of multiple dimension measuring devices when not contained 

in a single enclosure for the entire dimension/volume measuring device, and other components shall be marked as 

specified in Table S.4.1.a. and explained in the accompanying notes, Table S.4.1.b. (See Table Appendix at the end 

of this code.)

S.4.2. Location of Marking Information. - The required marking information shall be so located that it is readily 

observable without the necessity of the disassembly of a part requiring the use of any means separate from the device.

N. Notes

N.1. Test Procedures.

N.1.1. General. - The device shall be tested using test standards and objects of known and stable dimensions.

N.1.2. Position Test. - Measurements are made using different positions of the test object and consistent with the 

manufacturer's specified use for the device.

N.1.3. Disturbance Tests, Field Evaluation. - A disturbance test shall be conducted at a given installation when 

the presence of disturbances specified in T.6. has been verified and characterized if those conditions are considered 

"usual and customary."

N.1.4. Test Object Size. - Test objects may vary in size from the smallest dimension to the largest dimension 

marked on the device, and for field verification examinations, shall be an integer multiple of "d."

N.1.5. Digital Zero Stability. - A zero indication change test shall be conducted on all devices which show a digital 

zero. After the removal of any test object, the zero indication shall not change. (Also see G-UR.4.2.)

T. Tolerances

T.1. Design. - The tolerance for a multiple dimension measuring device is a performance requirement independent of the 

design principle used.

T.2. Tolerance Application.

T.2.1. Type Evaluation. - For type evaluations, the tolerance values apply to tests within the influence factor limits 

of temperature and power supply voltage specified in T.5.1. and T.5.2.

T.2.2. Subsequent Verification. - For subsequent verifications, the tolerance values apply regardless of the 

influence factors in effect at the time of the verification. (Also see G-N.2.)

T.2.3. Multi-interval (Variable Division-Value) Devices. - For multi-interval devices, the tolerance values are 

based on the value of the device division of the range in use.

T.3. Tolerance Values. - The maintenance and acceptance tolerance values shall be ±1 division. These tolerances apply 

regardless of the shape or material of the object being measured unless otherwise marked on the device.

T.4. Position Tests. - For a test standard measured several times in different positions by the device all indications shall 

be within applicable tolerances.

T.5. Influence Factors. - The following factors are applicable to tests conducted under controlled conditions only.

T.5.1. Temperature. - Devices shall satisfy the tolerance requirements under the following temperature conditions.
5.58. Multiple Dimension Measuring Devices

5-52

T.5.1.1. Temperature Limits. - If not marked on the device, the temperature limits shall be -10 C to 40 C 

(14 F to 104 F).

T.5.1.2. Minimum Temperature Range. - If temperature limits are specified for the device, the range shall be 

at least 30 C or 54 F.

T.5.1.3. Temperature Effect on Zero Indication. - The zero indication shall not vary by more than one 

division per 5 C (9 F) change in temperature.

T.5.2. Power Supply Voltage. - Devices shall satisfy the applicable tolerances when subjected to power supply 

voltage variation of -15 percent to +10 percent of the voltage rating specified by the manufacturer.

T.6. Disturbances, Field Evaluation. - The following requirements apply to devices when subjected to disturbances 

which may normally exist in the surrounding environment. These disturbances include radio frequency interference 

(RFI), electromagnetic interference (EMI), acoustic changes, ambient light emissions, etc. The difference between the 

measurement indication with the disturbance and the measurement indication without the disturbance shall not exceed one 

division "d" or the equipment shall:

(a) blank the indication, or

(b) provide an error message, or

(c) the indication shall be so completely unstable that it could not be interpreted, or transmitted into memory or to a 

recording element, as a correct measurement value.

T.7. Electric Power Supply. - Battery-operated instruments shall not indicate nor record values outside the applicable 

tolerance limits when battery power output is excessive or deficient.

(Added 1999)

UR. User Requirements

UR.1. Selection Requirements. - Equipment shall be suitable for the service in which it is used with respect to elements 

of its design, including but not limited to, its maximum capacity, value of the division, minimum capacity, and computing 

capability.

UR.1.1. Value of the Indicated and Recorded Division. - The value of the division recorded shall be the same as 

the division value indicated.

UR.2. Installation Requirements.

UR.2.1. Supports. - A device that is portable and is being used on a counter, table, or the floor shall be so 

positioned that it is firmly and securely supported.

UR.2.2. Foundation, Supports, and Clearance. - The foundations and support of a device installed in a fixed 

location shall be such as to provide strength, rigidity, and permanence of all components, and clearance shall be 

provided around all live parts to the extent that no contacts may result when the measuring element is empty, nor 

throughout the performance range of the device such that the operation or performance of the device is adversely 

affected.

UR.2.3. Protection From Environmental Factors. - The indicating and measuring elements of a device shall be 

adequately protected from environmental factors such as wind, weather, and RFI that may adversely affect the 

operation or performance of the device.

UR.3. Use Requirements.

UR.3.1. Minimum and Maximum Measuring Ranges. - A device shall not be used to measure objects smaller 

than the minimum or larger than the maximum dimensions marked on the device.
5.58. Multiple Dimension Measuring Devices

5-53

UR.3.2. Special Designs. - A multiple dimension measuring device designed and marked for a special application 

shall not be used for other than its intended purpose.

UR.4. Maintenance Requirements

UR.4.1. Zero or Ready Condition. – The zero-setting adjustment of a multiple dimension measuring device shall 

be maintained so that, with no object in or on the measuring element, the device shall indicate or record a zero or 

ready condition.

UR.4.2. Level Condition. – If a multiple dimension measuring device is equipped with a level-condition indicator, 

the device shall be maintained in a level condition.

UR.4.3. Device Modification. – The measuring capabilities of a device shall not be changed from the manufacturer’s 

design unless the modification has been approved by the manufacturer and the weights and measures authority 

having jurisdiction over the device.

D. Definitions

billed weight. The weight used in the computation of the freight, postal, or storage charge, whether actual weight or 

dimensional weight.

“d,” dimension division value. The smallest increment that the device displays for any axis and length of object in that 

axis.

dimensional weight (or dim, weight). A value computed by dividing the object’s volume by a conversion factor; it may 

be used for the calculation of charges when the value is greater than the actual weight.

measuring element. That portion of a complete device which does not include the indicating element.
5.58. Multiple Dimension Measuring Devices

5-54

Table S.1.6. Information to be Provided on Multiple Dimension Measuring Systems

Scenarios  Scenario 1.1 Scenario 1.2 Scenario 1.3 Scenarios 2, 3, 4

Information  Customer present

(printer only)

Customer present

(display only)

Customer present 

(printer and display) Customer is not present.

System ID P (only in multisystem applications)

D (only in multisystem applications)D or P (only in multisystem applications) P or A

Object ID N/A N/A N/A P or A

Dimensions and/or 

volume, units P D D and P P or A

Error indicator P D D and P N/A

Billing method P D D or P N/A

Billed weight P D D or P N/A

Total price P D D or P N/A

Dim weight (if 

applicable) P D D or P P or A

Scale weight (if 

applicable) P D D or P P or A

Tare (if applicable) P D D or P P or A

Oversized indicator P D D or P P or A

Dimensions are of 

smallest box P or M D or M D or P or M P or A

Billing rate or rate chart, 

conversion factors A A A P or A

D = DISPLAYED

A = AVAILABLE UPON REQUEST (retained for at least 30 days after invoice)

N/A: NOT APPLICABLE

P = PRINTED

M = MARKED ON THE DEVICE
5.58. Multiple Dimension Measuring Devices

5-55

Table S.1.11. Categories of Devices and Methods of Sealing for Multiple Dimension Measuring Systems

Categories of Devices Method of Sealing

Category 1: No remote configuration.

Seal by physical seal or two event counters: one for 

calibration parameters and one for configuration 

parameters.

Category 2: Remote configuration capability, but 

access is controlled by physical hardware.

Device shall clearly indicate that it is in the remote 

configuration mode and record such message if capable 

of printing in this mode.

The hardware enabling access for remote communication 

must be at the device and sealed using a physical seal or 

two event counters: one for calibration parameters and one 

for configuration parameters.

Category 3: Remote configuration capability access 

may be unlimited or controlled through a software 

switch (e.g., password).

An event logger is required in the device; it must include an 

event counter (000 to 999), the parameter ID, the date and 

time of the change, and the new value of the parameter. A 

printed copy of the information must be available through 

the device or through another on-site device. The event 

logger shall have a capacity to retain records equal to ten 

times the number of sealable parameters in the device, but 

not more than 1000 records are required. (Note: Does not 

require 1000 changes to be stored for each parameter.)
5.58. Multiple Dimension Measuring Devices

5-56

Table S.4.1.a. Marking Requirements for Multiple Dimension Measuring Systems

To Be Marked With 

Multiple Dimension Measuring Equipment

Multiple dimension 

measuring device 

and indicating 

element in same 

housing

Indicating element 

not permanently 

attached to multiple 

dimension 

measuring element

Multiple dimension 

measuring element 

not permanently 

attached to the 

indicating element

Other 

equipment

(1)

Manufacturer's ID x x x x

Model Designation x x x x

Serial Number and Prefix x x x x (2)

Certificate of Conformance Number (8) x x x x (8)

Minimum and Maximum Dimensions 

for Each Side (3) x x x

Value of Measuring Division, d x x x

Temperature Limits (4) x x x

Minimum & Maximum speed (5) x x x

Special Application (6) x x x

Limitation of Use (7) x x x

Multiple Dimension Measuring Systems Table S.4.1.b. Notes for Table S.4.1.a.

1. Necessary to the dimension and/or volume measuring system, but having no effect on the measuring value, e.g., 

auxiliary remote display, keyboard, etc.

2. Modules without "intelligence" on a modular system (e.g., printer, keyboard module, etc.) are not required to have 

serial numbers.

3. The minimum and maximum dimensions can be shown as follows:

 Length: min._______ max. _______

 Width: min._______ max. _______

 Height: min._______ max. _______

4. Required if the range is other than -10 C to 40 C (14 F to 104 F).

5. If the multiple dimension measuring device requires that the object or device be moved relative to one another, the 

minimum and maximum speeds are marked which enable the device to make measurements that are within the 

applicable tolerances shall be marked.

6. A device designed for a special application rather than general use shall be conspicuously marked with suitable words 

visible to the operator and the customer restricting its use to that application.

7. Materials, shapes, structures, or object orientations that are inappropriate for the device or those that are appropriate.

8. Required only if a Certificate of Conformance has been issued for the equipment.
Fundamental Considerations

A-1

Appendix A

Fundamental Considerations

Associated with the

Enforcement of Handbook 44 Codes

1. Uniformity of Requirements

1.1. National Conference Codes. - Weights and measures jurisdictions are urged to promulgate and adhere to the 

National Conference codes, to the end that uniform requirements may be in force throughout the country. This action is 

recommended even though a particular jurisdiction does not wholly agree with every detail of the National Conference 

codes. Uniformity of specifications and tolerances is an important factor in the manufacture of commercial equipment. 

Deviations from standard designs to meet the special demands of individual weights and measures jurisdictions are 

expensive, and any increase in costs of manufacture is, of course, passed on to the purchaser of equipment. On the other 

hand, if designs can be standardized by the manufacturer to conform to a single set of technical requirements, production 

costs can be kept down, to the ultimate advantage of the general public. Moreover, it seems entirely logical that 

equipment that is suitable for commercial use in the "specification" States should be equally suitable for such use in other 

States.

Another consideration supporting the recommendation for uniformity of requirements among weights and measures 

jurisdictions is the cumulative and regenerative effect of the widespread enforcement of a single standard of design and 

performance. The enforcement effort in each jurisdiction can then reinforce the enforcement effort in all other 

jurisdictions. More effective regulatory control can be realized with less individual effort under a system of uniform 

requirements than under a system in which even minor deviations from standard practice are introduced by independent 

State action.

Since the National Conference codes represent the majority opinion of a large and representative group of experienced 

regulatory officials, and since these codes are recognized by equipment manufacturers as their basic guide in the design 

and construction of commercial weighing and measuring equipment, the acceptance and promulgation of these codes by 

each State are strongly recommended.

1.2. Form of Promulgation. - A convenient and very effective form of promulgation already successfully used in a 

considerable number of States is promulgation by citation of National Institute of Standards and Technology Handbook 

44. It is especially helpful when the citation is so made that, as amendments are adopted from time to time by the 

National Conference on Weights and Measures, these automatically go into effect in the State regulatory authority. For 

example, the following form of promulgation has been used successfully and is recommended for consideration:

The specifications, tolerances, and other technical requirements for weighing and measuring devices as 

recommended by the National Conference on Weights and Measures and published in the National Institute of 

Standards and Technology Handbook 44, Specifications, Tolerances, and Other Technical Requirements for 

Weighing and Measuring Devices, and supplements thereto or revisions thereof, shall apply to commercial weighing 

and measuring devices in the State.

In some States, it is preferred to base technical requirements upon specific action of the State legislature rather than upon 

an act of promulgation by a State officer. The advantages cited above may be obtained and may yet be surrounded by 

adequate safeguards to insure proper freedom of action by the State enforcing officer if the legislature adopts the National 

Conference requirements by language somewhat as follows:

The specifications, tolerances, and other technical requirements for weighing and measuring devices as 

recommended by the National Conference on Weights and Measures shall be the specifications, tolerances, and other 

technical requirements for weighing and measuring devices of the State except insofar as specifically modified, 

amended, or rejected by a regulation issued by the State (insert title of enforcing officer).
Fundamental Considerations

A-2

2. Tolerances for Commercial Equipment

2.1. Acceptance and Maintenance Tolerances. - The official tolerances prescribed by a weights and measures 

jurisdiction for commercial equipment are the limits of inaccuracy officially permissible within that jurisdiction. It is 

recognized that errorless value or performance of mechanical equipment is unattainable. Tolerances are established, 

therefore, to fix the range of inaccuracy within which equipment will be officially approved for commercial use. In the 

case of classes of equipment on which the magnitude of the errors of value or performance may be expected to change as 

a result of use, two sets of tolerances are established: acceptance tolerances and maintenance tolerances.

Acceptance tolerances are applied to new or newly reconditioned or adjusted equipment, and are smaller than (usually 

one-half of) the maintenance tolerances. Maintenance tolerances thus provide an additional range of inaccuracy within

which equipment will be approved on subsequent tests, permitting a limited amount of deterioration before the equipment 

will be officially rejected for inaccuracy and before reconditioning or adjustment will be required. In effect, there is 

assured a reasonable period of use for equipment after it is placed in service before reconditioning will be officially 

required. The foregoing comments do not apply, of course, when only a single set of tolerance values is established, as is 

the case with equipment such as glass milk bottles and graduates, which maintain their original accuracy regardless of 

use, and measure-containers, which are used only once.

2.2. Theory of Tolerances. - Tolerance values are so fixed that the permissible errors are sufficiently small that there is 

no serious injury to either the buyer or the seller of commodities, yet not so small as to make manufacturing or 

maintenance costs of equipment disproportionately high. Obviously, the manufacturer must know what tolerances his 

equipment is required to meet, so that he can manufacture economically. His equipment must be good enough to satisfy 

commercial needs, but should not be subject to such stringent tolerance values as to make it unreasonably costly, complicated, or delicate.

2.3. Tolerances and Adjustments. - Tolerances are primarily accuracy criteria for use by the regulatory official. 

However, when equipment is being adjusted for accuracy, either initially or following repair or official rejection, the 

objective should be to adjust as closely as practicable to zero error. Equipment owners should not take advantage of 

tolerances by deliberately adjusting their equipment to have a value, or to give performance, at or close to the tolerance 

limit. Nor should the repair or service personnel bring equipment merely within tolerance range when it is possible to 

adjust closer to zero error.1

3. Testing Apparatus

3.1. Adequacy. - Tests can be made properly only if, among other things, adequate testing apparatus is available. 

Testing apparatus may be considered adequate only when it is properly designed for its intended use, when it is so 

constructed that it will retain its characteristics for a reasonable period under conditions of normal use, when it is 

available in denominations appropriate for a proper determination of the value or performance of the commercial 

equipment under test, and when it is accurately calibrated.

3.2. Tolerances for Standards.2 - The error in a standard used by a weights and measures official should be known and 

corrected for when the standard is used; or if the standard is to be used without correction, its error should be not greater

than one-third of the smallest tolerance to be applied when the standard is used. The reason for this is to keep at a 

minimum the proportion of the tolerance on the item tested that will be used up by the error of the standard. Expressed 

differently, the reason is to give the item being tested as nearly as practicable the full benefit of its own tolerance.

Field testing operations are complicated to some degree when corrections to standards are applied. Except for work of 

relatively high precision, it is recommended that the accuracy of standards used in testing commercial weighing and 

measuring equipment be so established and maintained that the use of corrections is not necessary. Also, whenever it can 

readily be done, it will be desirable to reduce the error on a standard below the one-third point previously mentioned.

 1 See General Code, Section 1.10.; User Requirement G-UR.4.3. 2 The numerical values of the tolerances recommended by the National Institute of Standards and Technology, for the 

standards of length, mass, and capacity used by weights and measures officials, may be obtained upon request from the 

Office of Weights and Measures of the National Institute of Standards and Technology.
Fundamental Considerations

A-3

3.3. Accuracy of Standards. - Prior to the official use of testing apparatus, its accuracy should invariably be verified. 

Standards should be re-verified as often as circumstances require. By their nature, metal volumetric standards are more 

susceptible to damage in handling than are standards of some other types. A standard should be re-calibrated whenever 

damage is known or suspected to have occurred or significant repairs have been made. In addition, standards, particularly 

volumetric standards, should be re-calibrated with sufficient frequency to affirm their continued accuracy, so that the 

official may always be in an unassailable position with respect to the accuracy of his testing apparatus. Secondary 

standards, such as special fabric testing tapes, should be verified much more frequently than such basic standards as steel 

tapes or volumetric provers to demonstrate their constancy of value or performance.

Accurate and dependable results cannot be obtained with faulty or inadequate standards. If either the service person or 

official is poorly equipped, their results cannot be expected to check consistently. Disagreements can be avoided and the 

servicing of commercial equipment can be expedited and improved if service persons and officials give equal attention to 

the adequacy and maintenance of their testing apparatus.

4. Inspection of Commercial Equipment

4.1. Inspection Versus Testing. - A distinction may be made between the inspection and the testing of commercial 

equipment that should be useful in differentiating between the two principal groups of official requirements; i.e., 

specifications and performance requirements. Although the term inspection is frequently loosely used to include 

everything that the official has to do in connection with commercial equipment, it is useful to limit the scope of that term 

primarily to examinations made to determine compliance with design, maintenance, and user requirements. The term 

testing may then be limited to those operations carried out to determine the accuracy of value or performance of the 

equipment under examination by comparison with the actual physical standards of the official. These two terms will be 

used herein in the limited senses defined.

4.2. Necessity for Inspection. - It is not enough merely to determine that the errors of equipment do not exceed the 

appropriate tolerances. Specification and user requirements are as important as tolerance requirements and should be 

enforced. Inspection is particularly important, and should be carried out with unusual thoroughness whenever the official 

examines a type of equipment not previously encountered.

This is the way the official learns whether or not the design and construction of the device conform to the specification 

requirements. But even a device of a type with which the official is thoroughly familiar and that he has previously found 

to meet specification requirements should not be accepted entirely on faith. Some part may have become damaged, or 

some detail of design may have been changed by the manufacturer, or the owner or operator may have removed an 

essential element or made an objectionable addition. Such conditions may be learned only by inspection. Some degree of 

inspection is therefore an essential part of the official examination of every piece of weighing or measuring equipment.

4.3. Specification Requirements. - A thorough knowledge by the official of the specification requirements is a 

prerequisite to competent inspection of equipment. The inexperienced official should have his specifications before him 

when making an inspection, and should check the requirements one by one against the equipment itself. Otherwise some 

important requirement may be overlooked. As experience is gained, the official will become progressively less dependent 

on the Handbook, until finally observance of faulty conditions becomes almost automatic and the time and effort required 

to do the inspecting are reduced to a minimum. The printed specifications, however, should always be available for 

reference to refresh the official's memory or to be displayed to support his decisions, and they are an essential item of his 

kit.

Specification requirements for a particular class of equipment are not all to be found in the separate code for that class. 

The requirements of the General Code apply, in general, to all classes of equipment, and these must always be considered 

in combination with the requirements of the appropriate separate code to arrive at the total of the requirements applicable 

to a piece of commercial equipment.

4.4. General Considerations. - The simpler the commercial device, the fewer are the specification requirements 

affecting it, and the more easily and quickly can adequate inspection be made. As mechanical complexity increases, 

however, inspection becomes increasingly important and more time consuming, because the opportunities for the 

existence of faulty conditions are multiplied. It is on the relatively complex device, too, that the official must be on the

alert to discover any modification that may have been made by an operator that might adversely affect the proper 

functioning of the device.
Fundamental Considerations

A-4

It is essential for the officials to familiarize themselves with the design and operating characteristics of the devices that he 

inspects and tests. Such knowledge can be obtained from the catalogs and advertising literature of device manufacturers, 

from trained service persons and plant engineers, from observation of the operations performed by service persons when 

reconditioning equipment in the field, and from a study of the devices themselves.

Inspection should include any auxiliary equipment and general conditions external to the device that may affect its 

performance characteristics. In order to prolong the life of the equipment and forestall rejection, inspection should also 

include observation of the general maintenance of the device and of the proper functioning of all required elements. The 

official should look for worn or weakened mechanical parts, leaks in volumetric equipment, or elements in need of 

cleaning.

4.5. Misuse of Equipment. - Inspection, coupled with judicious inquiry, will sometimes disclose that equipment is being 

improperly used, either through ignorance of the proper method of operation or because some other method is preferred 

by the operator. Equipment should be operated only in the manner that is obviously indicated by its construction or that is 

indicated by instructions on the equipment, and operation in any other manner should be prohibited.

4.6. Recommendations. - A comprehensive knowledge of each installation will enable the official to make constructive 

recommendations to the equipment owner regarding proper maintenance of his weighing and measuring devices and the 

suitability of his equipment for the purposes for which it is being used or for which it is proposed that it be used. Such 

recommendations are always in order and may be very helpful to an owner. The official will, of course, carefully avoid 

partiality toward or against equipment of specific makes, and will confine his recommendations to points upon which he 

is qualified, by knowledge and experience, to make suggestions of practical merit.

4.7. Accurate and Correct Equipment. - Finally, the weights and measures official is reminded that commercial 

equipment may be accurate without being correct. A piece of equipment is accurate when its performance or value (that 

is, its indications, its deliveries, its recorded representations, or its capacity or actual value, etc., as determined by tests 

made with suitable standards) conforms to the standard within the applicable tolerances and other performance 

requirements. Equipment that fails so to conform is inaccurate. A piece of equipment is correct when in addition to being 

accurate, it meets all applicable specification requirements. Equipment that fails to meet any of the requirements for 

correct equipment is incorrect. Only equipment that is correct should be sealed and approved for commercial use.3

5. Correction of Commercial Equipment

5.1. Adjustable Elements. - Many types of weighing and measuring instruments are not susceptible to adjustment for 

accuracy by means of adjustable elements. Linear measures, liquid measures, graduates, measure-containers, milk and 

lubricating-oil bottles, farm milk tanks, dry measures, and some of the more simple types of scales are in this category. 

Other types (for example, taximeters and odometers and some metering devices) may be adjusted in the field, but only by 

changing certain parts such as gears in gear trains.

Some types, of which fabric-measuring devices and cordage-measuring devices are examples, are not intended to be 

adjusted in the field and require reconditioning in shop or factory if inaccurate. Liquid-measuring devices and most 

scales are equipped with adjustable elements, and some vehicle-tank compartments have adjustable indicators. Field 

adjustments may readily be made on such equipment. In the discussion that follows, the principles pointed out and the 

recommendations made apply to adjustments on any commercial equipment, by whatever means accomplished.

5.2. When Corrections Should be Made. - One of the primary duties of a weights and measures official is to determine 

whether equipment is suitable for commercial use. If a device conforms to all legal requirements, the official "marks" or 

"seals" it to indicate approval. If it does not conform to all official requirements, the official is required to take action to 

ensure that the device is corrected within a reasonable period of time. Devices with performance errors that could result 

in serious economic injury to either party in a transaction should be prohibited from use immediately and not allowed to 

be returned to service until necessary corrections have been made. The official should consider the most appropriate 

action, based on all available information and economic factors.

Some officials contend that it is justifiable for the official to make minor corrections and adjustments if there is no service 

agency nearby or if the owner or operator depends on this single device and would be "out of business" if the use of the 

device were prohibited until repairs could be made.

 3 See Sec. 1.10.; General Code and Appendix D. Definitions.
Fundamental Considerations

A-5

Before adjustments are made at the request of the owner or the owner's representative, the official should be confident 

that the problem is not due to faulty installation or a defective part, and that the adjustment will correct the problem. The 

official should never undertake major repairs, or even minor corrections, if services of commercial agencies are readily 

available. The official should always be mindful of conflicts of interest before attempting to perform any services other 

than normal device examination and testing duties.

(Amended 1995)

5.3. Gauging. - In the majority of cases, when the weights and measures official tests commercial equipment, he is 

verifying the accuracy of a value or the accuracy of the performance as previously established either by himself or by 

someone else. There are times, however, when the test of the official is the initial test on the basis of which the 

calibration of the device is first determined or its performance first established. The most common example of such 

gauging is in connection with vehicle tanks the compartments of which are used as measures. Frequently the official 

makes the first determination on the capacities of the compartments of a vehicle tank, and his test results are used to 

determine the proper settings of the compartment indicators for the exact compartment capacities desired. Adjustments of 

the position of an indicator under these circumstances are clearly not the kind of adjustments discussed in the preceding 

paragraph.

6. Rejection of Commercial Equipment

6.1. Rejection and Condemnation. - The uniform Weights and Measures Law contains a provision stating that the 

director shall reject and order to be corrected such physical weights and measures or devices found to be incorrect. 

Weights and measures and devices that have been rejected may be seized if not corrected within a reasonable time or if 

used or disposed of in a manner not specifically authorized. The director shall remove from service and may seize 

weights and measures found to be incorrect that are not capable of being made correct.

These broad powers should be used by the official with discretion. The director should always keep in mind the property 

rights of an equipment owner, and cooperate in working out arrangements whereby an owner can realize at least 

something from equipment that has been rejected. In cases of doubt, the official should initially reject rather than 

condemn outright. Destruction and confiscation of equipment are harsh procedures. Power to seize and destroy is 

necessary for adequate control of extreme situations, but seizure and destruction should be resorted to only when clearly 

justified.

On the other hand, rejection is clearly inappropriate for many items of measuring equipment. This is true for most linear 

measures, many liquid and dry measures, and graduates, measure-containers, milk bottles, lubricating-oil bottles, and 

some scales. When such equipment is "incorrect," it is either impractical or impossible to adjust or repair it, and the 

official has no alternative to outright condemnation. When only a few such items are involved, immediate destruction or 

confiscation is probably the best procedure. If a considerable number of items are involved (as, for example, a stock of 

measures in the hands of a dealer or a large shipment of bottles), return of these to the manufacturer for credit or 

replacement should ordinarily be permitted provided that the official is assured that they will not get into commercial use. 

In rare instances, confiscation and destruction are justified as a method of control when less harsh methods have failed.

In the case of incorrect mechanisms such as fabric-measuring devices, taximeters, liquid-measuring devices, and most 

scales, repair of the equipment is usually possible, so rejection is the customary procedure. Seizure may occasionally be 

justified, but in the large majority of instances this should be unnecessary. Even in the case of worn-out equipment, some 

salvage is usually possible, and this should be permitted under proper controls.

(Amended 1995)

7. Tagging of Equipment

7.1. Rejected and Condemned. - It will ordinarily be practicable to tag or mark as rejected each item of equipment 

found to be incorrect and considered susceptible of proper reconditioning. However, it can be considered justifiable not 

to mark as rejected incorrect devices capable of meeting acceptable performance requirements if they are to be allowed to 

remain in service for a reasonable time until minor problems are corrected since marks of rejection may tend to be 

misleading about a device's ability to produce accurate measurements during the correction period. The tagging of 

equipment as condemned, or with a similar label to indicate that it is permanently out of service, is not recommended if 

there is any other way in which the equipment can definitely be put out of service. Equipment that cannot successfully be 
Fundamental Considerations

A-6

repaired should be dismantled, removed from the premises, or confiscated by the official rather than merely being tagged 

as "condemned."

(Amended 1995)

7.2. Nonsealed and Noncommercial. - Rejection is not appropriate if measuring equipment cannot be tested by the 

official at the time of his regular visit–for example, when there is no gasoline in the supply tank of a gasoline-dispensing 

device. Some officials affix to such equipment a nonsealed tag stating that the device has not been tested and sealed and 

that it must not be used commercially until it has been officially tested and approved. This is recommended whenever 

considerable time will elapse before the device can be tested.

Where the official finds in the same establishment, equipment that is in commercial use and also equipment suitable for 

commercial use that is not presently in service, but which may be put into service at some future time, he may treat the 

latter equipment in any of the following ways:

a. Test and approve the same as commercial equipment in use.

b. Refrain from testing it and remove it from the premises to preclude its use for commercial purposes.

c. Mark the equipment nonsealed.

Where the official finds commercial equipment and noncommercial equipment installed or used in close proximity, he 

may treat the noncommercial equipment in any of the following ways:

a. Test and approve the same as commercial equipment.

b. Physically separate the two groups of equipment so that misuse of the noncommercial equipment will be 

prevented.

c. Tag it to show that it has not been officially tested and is not to be used commercially.

8. Records of Equipment

8.1. The official will be well advised to keep careful records of equipment that is rejected, so that he may follow up to 

insure that the necessary repairs have been made. As soon as practicable following completion of repairs, the equipment 

should be retested. Complete records should also be kept of equipment that has been tagged as nonsealed or 

noncommercial. Such records may be invaluable should it subsequently become necessary to take disciplinary steps 

because of improper use of such equipment.

9. Sealing of Equipment

9.1. Types of Seals and Their Locations. - Most weights and measures jurisdictions require that all equipment officially 

approved for commercial use (with certain exceptions to be pointed out later) be suitably marked or sealed to show 

approval. This is done primarily for the benefit of the public to show that such equipment has been officially examined 

and approved. The seal of approval should be as conspicuous as circumstances permit and should be of such a character 

and so applied that it will be reasonably permanent. Uniformity of position of the seal on similar types of equipment is 

also desirable as a further aid to the public.

The official will need more than one form of seal to meet the requirements of different kinds of equipment. Good quality, 

weather-resistant, water-adhesive, or pressure-sensitive seals or decalcomania seals are recommended for 

fabric-measuring devices, liquid-measuring devices, taximeters, and most scales, because of their permanence and good 

appearance. Steel stamps are most suitable for liquid and dry measures, for some types of linear measures, and for 

weights. An etched seal, applied with suitable etching ink, is excellent for steel tapes, and greatly preferable to a seal 

applied with a steel stamp. The only practicable seal for a graduate is one marked with a diamond or carbide pencil, or 

one etched with glass-marking ink. For a vehicle tank, the official may wish to devise a relatively large seal, perhaps of 

metal, with provision for stamping data relative to compartment capacities, the whole to be welded or otherwise 

permanently attached to the shell of the tank. In general, the lead-and-wire seal is not suitable as an approval seal.
Fundamental Considerations

A-7

9.2. Exceptions. - Commercial equipment such as measure-containers, milk bottles, and lubricating-oil bottles are not 

tested individually because of the time element involved. Because manufacturing processes for these items are closely 

controlled, an essentially uniform product is produced by each manufacturer. The official normally tests samples of these 

items prior to their sale within his jurisdiction and subsequently makes spot checks by testing samples selected at random 

from new stocks.

Another exception to the general rule for sealing approved equipment is found in certain very small weights whose size 

precludes satisfactory stamping with a steel die.

10. Rounding Off Numerical Values

10.1. Definition. - To round off or round a numerical value is to change the value of recorded digits to some other value 

considered more desirable for the purpose at hand by dropping or changing certain figures. For example, if a computed, 

observed, or accumulated value is 4738, this can be rounded off to the nearest thousand, hundred, or ten, as desired. Such 

rounded-off values would be, respectively, 5000, 4700, 4740. Similarly, a value such as 47.382 can be rounded off to two 

decimal places, to one decimal place, or to the units place. The rounded-off figures in this example would be, 

respectively, 47.38, 47.4, 47.

10.2. General Rules. - The general rules for rounding off may be stated briefly as follows:

a. When the figure next beyond the last figure or place to be retained is less than 5, the figure in the last place 

retained is to be kept unchanged. When rounding off 4738 to the nearest hundred, it is noted that the figure 3 

(next beyond the last figure to be retained) is less than 5. Thus the rounded-off value would be 4700. Likewise, 

47.382 rounded to two decimal places becomes 47.38.

b. When the figure next beyond the last figure or place to be retained is greater than 5, the figure in the last place 

retained is to be increased by 1. When rounding off 4738 to the nearest thousand, it is noted that the figure 7 

(next beyond the last figure to be retained) is greater than 5. Thus the rounded-off value would be 5000. 

Likewise, 47.382 rounded to one decimal place becomes 47.4.

c. When the figure next beyond the last figure to be retained is 5 followed by any figures other than zero(s), treat as 

in (b) above; that is, the figure in the last place retained is to be increased by 1. When rounding off 4501 to the 

nearest thousand, 1 is added to the thousands figure and the result becomes 5000.

d. When the figure next beyond the last figure to be retained is 5 and there are no figures, or only zeros, beyond this 

5, the figure in the last place to be retained is to be left unchanged if it is even (0, 2, 4, 6, or 8) and is to be 

increased by 1 if it is odd (1, 3, 5, 7, or 9). This is the odd and even rule, and may be stated as follows: "If odd, 

then add." Thus, rounding off to the first decimal place, 47.25 would become 47.2 and 47.15 would become 

47.2. Also, rounded to the nearest thousand, 4500 would become 4000 and 1500 would become 2000.

It is important to remember that, when there are two or more figures to the right of the place where the last significant 

figure of the final result is to be, the entire series of such figures must be rounded off in one step and not in two or more

successive rounding steps. [Expressed differently, when two or more such figures are involved, these are not to be 

rounded off individually, but are to be rounded off as a group.] Thus, when rounding off 47.3499 to the first decimal 

place, the result becomes 47.3. In arriving at this result, the figures "499" are treated as a group. Since the 4 next beyond 

the last figure to be retained is less than 5, the "499" is dropped (see subparagraph (a) above). It would be incorrect to 

round off these figures successively to the left so that 47.3499 would become 47.350 and then 47.35 and then 47.4.

10.3. Rules for Reading of Indications. - An important aspect of rounding off values is the application of these rules to 

the reading of indications of an indicator-and-graduated-scale combination (where the majority of the indications may be 

expected to lie somewhere between two graduations) if it is desired to read or record values only to the nearest 

graduation. Consider a vertical graduated scale and an indicator. Obviously, if the indicator is between two graduations 

but is closer to one graduation than it is to the other adjacent graduation, the value of the closer graduation is the one to be 

read or recorded.

In the case where, as nearly as can be determined, the indicator is midway between two graduations, the odd-and-even

rule is invoked, and the value to be read or recorded is that of the graduation whose value is even. For example, if the 

indicator lies exactly midway between two graduations having values of 471 and 472, respectively, the indication should 
Fundamental Considerations

A-8

be read or recorded as 472, this being an even value. If midway between graduations having values of 474 and 475, the 

even value 474 should be read or recorded. Similarly, if the two graduations involved had values of 470 and 475, the 

even value of 470 should be read or recorded.

A special case not covered by the foregoing paragraph is that of a graduated scale in which successive graduations are 

numbered by twos, all graduations thus having even values; for example, 470, 472, 474, etc. When, in this case, an 

indication lies midway between two graduations, the recommended procedure is to depart from the practice of reading or 

recording only to the value of the nearest graduation and to read or record the intermediate odd value. For example, an 

indication midway between 470 and 472 should be read as 471.

10.4. Rules for Common Fractions. - When applying the rounding-off rules to common fractions, the principles are to 

be applied to the numerators of the fractions that have, if necessary, been reduced to a common denominator. The 

principle of "5s" is changed to the one-half principle; that is, add if more than one-half, drop if less than one-half, and 

apply the odd-and even rule if exactly one-half.

For example, a series of values might be 1-1/32, 1-2/32, 1-3/32, 1-4/32, 1-5/32, 1-6/32, 1-7/32, 1-8/32, 1-9/32. Assume 

that these values are to be rounded off to the nearest eighth (4/32). Then,

1-1/32 becomes 1. (1/32 is less than half of 4/32 and accordingly is dropped.)

1-2/32 becomes 1. (2/32 is exactly one-half of 4/32; it is dropped because it is round (down) to the "even" eighth, 

which in this instance is 0/8.)

1-3/32 becomes 1-4/32 or 1-1/8. (3/32 is more than half of 4/32,and accordingly is rounded "up" to 4/32 or 1/8).

1-4/32 remains unchanged, being an exact eighth (1-1/8).

1-5/32 becomes 1-4/32 or 1-1/8. (5/32 is 1/32 more than an exact 1/8; 1/32 is less than half of 4/32 and accordingly 

is dropped.)

1-6/32 becomes 1-2/8 or 1-1/4. (6/32 is 2/32 more than an exact 1/8; 2/32 is exactly one-half of 4/32, and the final 

fraction is rounded (up) to the "even" eighth, which in this instance is 2/8.)

1-7/32 becomes 1-2/8 or 1-1/4. (7/32 is 3/32 more than an exact 1/8; 3/32 is more than one-half of 4/32 and 

accordingly the final fraction is rounded (up) to 2/8 or 1/4.)

1-8/32 remains unchanged, being an exact eighth (1-2/8 or 1-1/4.)

1-9/32 becomes 1-2/8 or 1-1/4. (9/32 is 1/32 more than an exact 1/8; 1/32 is less than half of 4/32 and accordingly is 

dropped.)
Units and Systems

B-1

Appendix B

Units and Systems of Measurement

Their Origin, Development, and Present Status

1. Introduction

The National Institute of Standards and Technology (NIST) (formerly the National Bureau of Standards) was established 

by Act of Congress in 1901 to serve as a national scientific laboratory in the physical sciences, and to provide 

fundamental measurement standards for science and industry. In carrying out these related functions the Institute 

conducts research and development in many fields of physics, mathematics, chemistry, and engineering. At the time of 

its founding, the Institute had custody of two primary standards–the meter bar for length and the kilogram cylinder for 

mass. With the phenomenal growth of science and technology over the past century, the Institute has become a major 

research institution concerned not only with everyday weights and measures, but also with hundreds of other scientific 

and engineering standards that are necessary to the industrial progress of the Nation. Nevertheless, the country still looks 

to NIST for information on the units of measurement, particularly their definitions and equivalents.

The subject of measurement systems and units can be treated from several different standpoints. Scientists and engineers 

are interested in the methods by which precision measurements are made. State weights and measures officials are 

concerned with laws and regulations that assure equity in the marketplace, protect public health and safety, and with 

methods for verifying commercial weighing and measuring devices. But a vastly larger group of people is interested in 

some general knowledge of the origin and development of measurement systems, of the present status of units and 

standards, and of miscellaneous facts that will be useful in everyday life. This material has been prepared to supply that 

information on measurement systems and units that experience has shown to be the common subject of inquiry.

2. Units and Systems of Measurement

The expression "weights and measures" is often used to refer to measurements of length, mass, and capacity or volume, 

thus excluding such quantities as electrical and time measurements and thermometry. This section on units and 

measurement systems presents some fundamental information to clarify the concepts of this subject and to eliminate 

erroneous and misleading use of terms.

It is essential that the distinction between the terms "units" and "standards" be established and kept in mind.

A unit is a special quantity in terms of which other quantities are expressed. In general, a unit is fixed by definition and is 

independent of such physical conditions as temperature. Examples: the meter, the liter, the gram, the yard, the pound, the 

gallon.

A standard is a physical realization or representation of a unit. In general, it is not entirely independent of physical 

conditions, and it is a representation of the unit only under specified conditions. For example, a meter standard has a 

length of one meter when at some definite temperature and supported in a certain manner. If supported in a different 

manner, it might have to be at a different temperature to have a length of one meter.

2.1. Origin and Early History of Units and Standards.

2.1.1. General Survey of Early History of Measurement Systems. - Weights and measures were among the 

earliest tools invented by man. Primitive societies needed rudimentary measures for many tasks: constructing 

dwellings of an appropriate size and shape, fashioning clothing, or bartering food or raw materials.

Man understandably turned first to parts of the body and the natural surroundings for measuring instruments. Early 

Babylonian and Egyptian records and the Bible indicate that length was first measured with the forearm, hand, or 

finger and that time was measured by the periods of the sun, moon, and other heavenly bodies. When it was 

necessary to compare the capacities of containers such as gourds or clay or metal vessels, they were filled with plant 

seeds which were then counted to measure the volumes. When means for weighing were invented, seeds and stones 

served as standards. For instance, the "carat," still used as a unit for gems, was derived from the carob seed.
Units and Systems

B-2

Our present knowledge of early weights and measures comes from many sources. Archaeologists have recovered 

some rather early standards and preserved them in museums. The comparison of the dimensions of buildings with the 

descriptions of contemporary writers is another source of information. An interesting example of this is the 

comparison of the dimensions of the Greek Parthenon with the description given by Plutarch from which a fairly 

accurate idea of the size of the Attic foot is obtained. In some cases, we have only plausible theories and we must 

sometimes select the interpretation to be given to the evidence.

For example, does the fact that the length of the double-cubit of early Babylonia was equal (within two parts per 

thousand) to the length of the seconds pendulum at Babylon suggest a scientific knowledge of the pendulum at a very 

early date, or do we merely have a curious coincidence? By studying the evidence given by all available sources, and 

by correlating the relevant facts, we obtain some idea of the origin and development of the units. We find that they 

have changed more or less gradually with the passing of time in a complex manner because of a great variety of 

modifying influences. We find the units modified and grouped into measurement systems: The Babylonian system, 

the Egyptian system, the Phileterian system of the Ptolemaic age, the Olympic system of Greece, the Roman system, 

and the British system, to mention only a few.

2.1.2. Origin and Development of Some Common Customary Units. - The origin and development of units of 

measurement has been investigated in considerable detail and a number of books have been written on the subject. It 

is only possible to give here, somewhat sketchily, the story about a few units.

Units of length: The cubit was the first recorded unit used by ancient peoples to measure length. There were several 

cubits of different magnitudes that were used. The common cubit was the length of the forearm from the elbow to 

the tip of the middle finger. It was divided into the span of the hand (one-half cubit), the palm or width of the hand 

(one sixth), and the digit or width of a finger (one twenty-fourth). The Royal or Sacred Cubit, which was 7 palms or 

28 digits long, was used in constructing buildings and monuments and in surveying. The inch, foot, and yard evolved 

from these units through a complicated transformation not yet fully understood. Some believe they evolved from 

cubic measures; others believe they were simple proportions or multiples of the cubit. In any case, the Greeks and 

Romans inherited the foot from the Egyptians. The Roman foot was divided into both 12 unciae (inches) and 

16 digits. The Romans also introduced the mile of 1000 paces or double steps, the pace being equal to five Roman 

feet. The Roman mile of 5000 feet was introduced into England during the occupation. Queen Elizabeth, who 

reigned from 1558 to 1603, changed, by statute, the mile to 5280 feet or 8 furlongs, a furlong being 40 rods of 5-1/2 

yards each.

The introduction of the yard as a unit of length came later, but its origin is not definitely known. Some believe the 

origin was the double cubit, others believe that it originated from cubic measure. Whatever its origin, the early yard 

was divided by the binary method into 2, 4, 8, and 16 parts called the half-yard, span, finger, and nail. The 

association of the yard with the "gird" or circumference of a person's waist or with the distance from the tip of the 

nose to the end of the thumb of Henry I are probably standardizing actions, since several yards were in use in Great 

Britain.

The point, which is a unit for measuring print type, is recent. It originated with Pierre Simon Fournier in 1737. It 

was modified and developed by the Didot brothers, Francois Ambroise and Pierre Francois, in 1755. The point was 

first used in the United States in 1878 by a Chicago type foundry (Marder, Luse, and Company). Since 1886, a point 

has been exactly 0.3514598 millimeters, or about 1/72 inch. 

Units of mass: The grain was the earliest unit of mass and is the smallest unit in the apothecary, avoirdupois, Tower, 

and Troy systems. The early unit was a grain of wheat or barleycorn used to weigh the precious metals silver and 

gold. Larger units preserved in stone standards were developed that were used as both units of mass and of monetary 

currency. The pound was derived from the mina used by ancient civilizations. A smaller unit was the shekel, and a 

larger unit was the talent. The magnitude of these units varied from place to place. The Babylonians and Sumerians 

had a system in which there were 60 shekels in a mina and 60 minas in a talent. The Roman talent consisted of 100 

libra (pound) which were smaller in magnitude than the mina. The Troy pound used in England and the United 

States for monetary purposes, like the Roman pound, was divided into 12 ounces, but the Roman uncia (ounce) was 

smaller. The carat is a unit for measuring gemstones that had its origin in the carob seed, which later was 

standardized at 1/144 ounce and then 0.2 gram.
Units and Systems

B-3

Goods of commerce were originally traded by number or volume. When weighing of goods began, units of mass 

based on a volume of grain or water were developed. For example, the talent in some places was approximately 

equal to the mass of one cubic foot of water. Was this a coincidence or by design? The diverse magnitudes of units 

having the same name, which still appear today in our dry and liquid measures, could have arisen from the various 

commodities traded. The larger avoirdupois pound for goods of commerce might have been based on volume of 

water which has a higher bulk density than grain. For example, the Egyptian hon was a volume unit about 11 percent 

larger than a cubic palm and corresponded to one mina of water. It was almost identical in volume to the present 

U.S. pint.

The stone, quarter, hundredweight, and ton were larger units of mass used in Great Britain. Today only the stone 

continues in customary use for measuring personal body weight. The present stone is 14 pounds, but an earlier unit 

appears to have been 16 pounds. The other units were multiples of 2, 8, and 160 times the stone, or 28, 112, and 

2240 pounds, respectively. The hundredweight was approximately equal to two talents. In the United States the ton 

of 2240 pounds is called the “long ton.” The “short ton” is equal to 2000 pounds.

Units of time and angle: We can trace the division of the circle into 360 degrees and the day into hours, minutes, and 

seconds to the Babylonians who had a sexagesimal system of numbers. The 360 degrees may have been related to a 

year of 360 days.

2.2. The Metric System.

2.2.1. Definition, Origin, and Development. - Metric systems of units have evolved since the adoption of the first 

well defined system in France in 1791. During this evolution the use of these systems spread throughout the world, 

first to the non-English speaking countries, and more recently to the English speaking countries. The first metric 

system was based on the centimeter, gram, and second (cgs) and these units were particularly convenient in science 

and technology. Later metric systems were based on the meter, kilogram, and second (mks) to improve the value of 

the units for practical applications. The present metric system is the International System of Units (SI). It is also 

based on the meter, kilogram and second as well as additional base units for temperature, electric current, luminous 

intensity, and amount of substance. the International System of Units is referred to as the modern metric system.

The adoption of the metric system in France was slow, but its desirability as an international system was recognized 

by geodesists and others. On May 20, 1875, an international treaty known as the International Metric Convention or 

the Treaty of the Meter was signed by 17 countries including the United States. This treaty established the following 

organizations to conduct international activities relating to a uniform system for measurements:

1) The General Conference on Weights and Measures (French initials: CGPM), an intergovernmental conference 

of official delegates of member nations and the supreme authority for all actions;

2) The International Committee of Weights and Measures (French initials: CIPM), consisting of selected 

scientists and metrologists, which prepares and executes the decisions of the CGPM and is responsible for the 

supervision of the International Bureau of Weights and Measures;

3) The International Bureau of Weights and Measures (French initials: BIPM), a permanent laboratory and world 

center of scientific metrology, the activities of which include the establishment of the basic standards and scales 

of the principal physical quantities and maintenance of the international prototype standards.

The National Institute of Standards and Technology provides official United States representation in these 

organizations. The CGPM, the CIPM, and the BIPM have been major factors in the continuing refinement of the 

metric system on a scientific basis and in the evolution of the International System of Units. 

Multiples and submultiples of metric units are related by powers of ten. This relationship is compatible with the 

decimal system of numbers and it contributes greatly to the convenience of metric units.

2.2.2. International System of Units. - At the end of World War II, a number of different systems of measurement 

still existed throughout the world. Some of these systems were variations of the metric system, and others were 

based on the customary inch-pound system of the English-speaking countries. It was recognized that additional steps 

were needed to promote a worldwide measurement system. As a result the 9th GCPM, in 1948, asked the ICPM to 

conduct an international study of the measurement needs of the scientific, technical, and educational communities. 
Units and Systems

B-4

Based on the findings of this study, the 10th General Conference in 1954 decided that an international system should 

be derived from six base units to provide for the measurement of temperature and optical radiation in addition to 

mechanical and electromagnetic quantities. The six base units recommended were the meter, kilogram, second, 

ampere, Kelvin degree (later renamed the kelvin), and the candela.

In 1960, the 11th General Conference of Weights and Measures named the system based on the six base quantities 

the International System of Units, abbreviated SI from the French name: Le Système International d'Unités. The SI 

metric system is now either obligatory or permissible throughout the world.

2.2.3. Units and Standards of the Metric System. - In the early metric system there were two fundamental or base 

units, the meter and the kilogram, for length and mass. The other units of length and mass, and all units of area, 

volume, and compound units such as density were derived from these two fundamental units.

The meter was originally intended to be one ten-millionth part of a meridional quadrant of the earth. The Meter of 

the Archives, the platinum length standard which was the standard for most of the 19th century, at first was supposed 

to be exactly this fractional part of the quadrant. More refined measurements over the earth's surface showed that 

this supposition was not correct. In 1889, a new international metric standard of length, the International Prototype 

Meter, a graduated line standard of platinum-iridium, was selected from a group of bars because precise 

measurements found it to have the same length as the Meter of the Archives. The meter was then defined as the 

distance, under specified conditions, between the lines on the International Prototype Meter without reference to any 

measurements of the earth or to the Meter of the Archives, which it superseded. Advances in science and technology 

have made it possible to improve the definition of the meter and reduce the uncertainties associated with artifacts. 

From 1960 to 1983, the meter was defined as the length equal to 1 650 763.73 wavelengths in a vacuum of the 

radiation corresponding to the transition between the specified energy levels of the krypton 86 atom. Since 1983 the 

meter has been defined as the length of the path traveled by light in a vacuum during an interval of 1/299 792 458 of 

a second. 

The kilogram, originally defined as the mass of one cubic decimeter of water at the temperature of maximum density, 

was known as the Kilogram of the Archives. It was replaced after the International Metric Convention in 1875 by the 

International Prototype Kilogram which became the unit of mass without reference to the mass of a cubic decimeter 

of water or to the Kilogram of the Archives. Each country that subscribed to the International Metric Convention 

was assigned one or more copies of the international standards; these are known as National Prototype Meters and 

Kilograms.

The liter is a unit of capacity or volume. In 1964, the 12th GCPM redefined the liter as being one cubic decimeter. 

By its previous definition -- the volume occupied, under standard conditions, by a quantity of pure water having a 

mass of one kilogram -- the liter was larger than the cubic decimeter by 28 parts per 1 000 000. Except for 

determinations of high precision, this difference is so small as to be of no consequence.

The modern metric system (SI) includes two classes of units:

base units for length, mass, time, temperature, electric current, luminous intensity, and amount of 

substance; and

derived units for all other quantities (e.g., work, force, power) expressed in terms of the seven base units.

For details, see NIST Special Publication 330 (2001), The International System of Units (SI) and NIST Special 

Publication 811(1995), Guide for the Use of the International System of Units.

2.2.4. International Bureau of Weights and Measures. - The International Bureau of Weights and Measures 

(BIPM) was established at Sèvres, a suburb of Paris, France, by the International Metric Convention of May 20, 

1875. The BIPM maintains the International Prototype Kilogram, many secondary standards, and equipment for 

comparing standards and making precision measurements. The Bureau, funded by assessment of the signatory 

governments, is truly international. In recent years the scope of the work at the Bureau has been considerably 

broadened. It now carries on researches in the fields of electricity, photometry and radiometry, ionizing radiations, 

and time and frequency besides its work in mass, length, and thermometry.
Units and Systems

B-5

2.2.5. Status of the Metric System in the United States. - The use of the metric system in this country was 

legalized by Act of Congress in 1866, but was not made obligatory then or since.

Following the signing of the Convention of the Meter in 1875, the United States acquired national prototype 

standards for the meter and the kilogram. U.S. Prototype Kilogram No. 20 continues to be the primary standard for 

mass in the United States. It is recalibrated from time to time at the BIPM. The prototype meter has been replaced by 

modern stabilized lasers following the most recent definition of the meter.

From 1893 until 1959, the yard was defined as equal exactly to 3600/3937 meter. In 1959, a small change was made 

in the definition of the yard to resolve discrepancies both in this country and abroad. Since 1959, we define the yard 

as equal exactly to 0.9144 meter; the new yard is shorter than the old yard by exactly two parts in a million. At the 

same time, it was decided that any data expressed in feet derived from geodetic surveys within the United States 

would continue to bear the relationship as defined in 1893 (one foot equals 1200/3937 meter). We call this foot the 

U.S. Survey Foot, while the foot defined in 1959 is called the International Foot. Measurements expressed in U.S. 

statute miles, survey feet, rods, chains, links, or the squares thereof, and acres should be converted to the 

corresponding metric values by using pre-1959 conversion factors if more than five significant figure accuracy is 

required.

Since 1970, actions have been taken to encourage the use of metric units of measurement in the United States. A 

brief summary of actions by Congress is provided below as reported in the Federal Register Notice dated July 28, 

1998.

Section 403 of Public Law 93-380, the Education Amendment of 1974, states that it is the policy of the United States 

to encourage educational agencies and institutions to prepare students to use the metric system of measurement as 

part of the regular education program. Under both this act and the Metric Conversion Act of 1975, the "metric 

system of measurement" is defined as the International System of Units as established in 1960 by the General 

Conference on Weights and Measures and interpreted or modified for the United States by the Secretary of 

Commerce (sec. 4(4)- Pub. L. 94-168; sec. 403(a)(3)- Pub. L. 93-380). The Secretary has delegated authority under 

these subsections to the Director of the National Institute of Standards and Technology.

Section 5164 of Public Law 100-418, the Omnibus Trade and Competitiveness Act of 1988, amends Public Law 94-

168, The Metric Conversion Act of 1975. In particular, section 3 Metric Conversion Act is amended to read as 

follows:

"Sec. 3. It is therefore the declared policy of the United States–

(1) to designate the metric system of measurement as the preferred system of weights and measures for United 

States trade and commerce;

(2) to require that each Federal agency, by a date certain and to the extent economically feasible by the end of 

the fiscal year 1992, use the metric system of measurement in its procurements, grants, and other businessrelated activities, except to the extent that such use is impractical or is likely to cause significant inefficiencies or 

loss of markets to U.S. firms, such as when foreign competitors are producing competing products in non-metric 

units;

(3) to seek ways to increase understanding of the metric system of measurement through educational information 

and guidance and in Government publications; and

(4) to permit the continued use of traditional systems of weights and measures in nonbusiness activities."

The Code of Federal Regulations makes the use of metric units mandatory for agencies of the Federal Government. 

(Federal Register, Vol. 56, No. 23, page 160, January 2, 1991.)

2.3. British and United States Systems of Measurement. - In the past, the customary system of weights and measures 

in the British Commonwealth countries and that in the United States were very similar; however, the SI metric system is 

now the official system of units in the United Kingdom, while the customary units are still predominantly used in the 

United States. Because references to the units of the old British customary system are still found, the following 

discussion describes the differences between the U.S. and British customary systems of units.
Units and Systems

B-6

After 1959, the U.S. and the British inch were defined identically for scientific work and were identical in commercial 

usage. A similar situation existed for the U.S. and the British pound, and many relationships, such as 12 inches = 1 foot, 

3 feet = 1 yard, and 1760 yards = 1 international mile, were the same in both countries; but there were some very 

important differences.

In the first place, the U.S. customary bushel and the U.S. gallon, and their subdivisions differed from the corresponding 

British Imperial units. Also the British ton is 2240 pounds, whereas the ton generally used in the United States is the 

short ton of 2000 pounds. The American colonists adopted the English wine gallon of 231 cubic inches. The English of 

that period used this wine gallon and they also had another gallon, the ale gallon of 282 cubic inches. In 1824, the British 

abandoned these two gallons when they adopted the British Imperial gallon, which they defined as the volume of 10 

pounds of water, at a temperature of 62 F, which, by calculation, is equivalent to 277.42 cubic inches. At the same time, 

they redefined the bushel as 8 gallons.

In the customary British system the units of dry measure are the same as those of liquid measure. In the United States 

these two are not the same, the gallon and its subdivisions are used in the measurement of liquids; the bushel, with its 

subdivisions, is used in the measurement of certain dry commodities. The U.S. gallon is divided into four liquid quarts 

and the U.S. bushel into 32 dry quarts. All the units of capacity or volume mentioned thus far are larger in the customary 

British system than in the U.S. system. But the British fluid ounce is smaller than the U.S. fluid ounce, because the 

British quart is divided into 40 fluid ounces whereas the U.S. quart is divided into 32 fluid ounces.

From this we see that in the customary British system an avoirdupois ounce of water at 62 F has a volume of one fluid 

ounce, because 10 pounds is equivalent to 160 avoirdupois ounces, and 1 gallon is equivalent to 4 quarts, or 160 fluid 

ounces. This convenient relation does not exist in the U.S. system because a U.S. gallon of water at 62 F weighs about 

8-1/3 pounds, or 133-1/3 avoirdupois ounces, and the U.S. gallon is equivalent to 4 x 32, or 128 fluid ounces.

1 U.S. fluid ounce = 1.041 British fluid ounces

1 British fluid ounce = 0.961 U.S. fluid ounce

1 U.S. gallon= 0.833 British Imperial gallon

1 British Imperial gallon = 1.201 U.S. gallons

Among other differences between the customary British and the United States measurement systems, we should note that 

they abolished the use of the troy pound in England January 6, 1879, they retained only the troy ounce and its 

subdivisions, whereas the troy pound is still legal in the United States, although it is not now greatly used. We can 

mention again the common use, for body weight, in England of the stone of 14 pounds, this being a unit now unused in 

the United States, although its influence was shown in the practice until World War II of selling flour by the barrel of 196 

pounds (14 stone). In the apothecary system of liquid measure the British add a unit, the fluid scruple, equal to one third 

of a fluid drachm (spelled dram in the United States) between their minim and their fluid drachm. In the United States, 

the general practice now is to sell dry commodities, such as fruits and vegetables, by their mass.

2.4. Subdivision of Units. - In general, units are subdivided by one of three methods: (a) decimal, into tenths; (b) 

duodecimal, into twelfths; or (c) binary, into halves (twos). Usually the subdivision is continued by using the same 

method. Each method has its advantages for certain purposes, and it cannot properly be said that any one method is 

"best" unless the use to which the unit and its subdivisions are to be put is known.

For example, if we are concerned only with measurements of length to moderate precision, it is convenient to measure 

and to express these lengths in feet, inches, and binary fractions of an inch, thus 9 feet 4-3/8 inches. However, if these 

lengths are to be subsequently used to calculate area or volume, that method of subdivision at once becomes extremely 

inconvenient. For that reason, civil engineers, who are concerned with areas of land, volumes of cuts, fills, excavations, 

etc., instead of dividing the foot into inches and binary subdivisions of the inch, divide it decimally; that is, into tenths, 

hundredths, and thousandths of a foot.

The method of subdivision of a unit is thus largely made based on convenience to the user. The fact that units have 

commonly been subdivided into certain subunits for centuries does not preclude their also having another mode of 

subdivision in some frequently used cases where convenience indicates the value of such other method. Thus, while we 

usually subdivide the gallon into quarts and pints, most gasoline-measuring pumps, of the price-computing type, are 

graduated to show tenths, hundredths, or thousandths of a gallon. 
Units and Systems

B-7

Although the mile has for centuries been divided into rods, yards, feet, and inches, the odometer part of an automobile 

speedometer shows tenths of a mile. Although we divide our dollar into 100 parts, we habitually use and speak of halves 

and quarters. An illustration of rather complex subdividing is found on the scales used by draftsmen. These scales are of 

two types: (a) architects, which are commonly graduated with scales in which 3/32, 3/16, 1/8, 1/4, 3/8, 1⁄2, 3/4, 1, 1-1/2, 

and 3 inches, respectively, represent 1 foot full scale, and also having a scale graduated in the usual manner to 1/16 inch; 

and (b) engineers, which are commonly subdivided to 10, 20, 30, 40, 50, and 60 parts to the inch.

The dictum of convenience applies not only to subdivisions of a unit but also to multiples of a unit. Land elevations 

above sea level are given in feet although the height may be several miles; the height of aircraft above sea level as given 

by an altimeter is likewise given in feet, no matter how high it may be.

On the other hand, machinists, toolmakers, gauge makers, scientists, and others who are engaged in precision 

measurements of relatively small distances, even though concerned with measurements of length only, find it convenient 

to use the inch, instead of the tenth of a foot, but to divide the inch decimally to tenths, hundredths, thousandths, etc., 

even down to millionths of an inch. Verniers, micrometers, and other precision measuring instruments are usually 

graduated in this manner. Machinist scales are commonly graduated decimally along one edge and are also graduated 

along another edge to binary fractions as small as 1/64 inch. The scales with binary fractions are used only for relatively 

rough measurements.

It is seldom convenient or advisable to use binary subdivisions of the inch that are smaller than 1/64. In fact, 1/32-, 1/16-, 

or 1/8-inch subdivisions are usually preferable for use on a scale to be read with the unaided eye.

2.5. Arithmetical Systems of Numbers. - The subdivision of units of measurement is closely associated with 

arithmetical systems of numbers. The systems of units used in this country for commercial and scientific work, having 

many origins as has already been shown, naturally show traces of the various number systems associated with their 

origins and developments. Thus, (a) the binary subdivision has come down to us from the Hindus, (b) the duodecimal 

system of fractions from the Romans, (c) the decimal system from the Chinese and Egyptians, some developments having 

been made by the Hindus, and (d) the sexagesimal system (division by 60) now illustrated in the subdivision of units of 

angle and of time, from the ancient Babylonians. The use of decimal numbers in measurements is becoming the standard 

practice.

3. Standards of Length, Mass, and Capacity or Volume

3.1. Standards of Length. - The meter, which is defined in terms of the speed of light in a vacuum, is the unit on which 

all length measurements are based. 

The yard is defined1 as follows:

1 yard = 0.914 4 meter

and the inch is exactly equal to 25.4 millimeters.

3.1.1. Calibration of Length Standards. - NIST calibrates standards of length including meter bars, yard bars, 

miscellaneous precision line standards, steel tapes, invar geodetic tapes, precision gauge blocks, micrometers, and 

limit gauges. It also measures the linear dimensions of miscellaneous apparatus such as penetration needles, cement 

sieves, and hemacytometer chambers. In general, NIST accepts for calibration only apparatus of such material, 

design, and construction as to ensure accuracy and permanence sufficient to justify calibration by the Institute. NIST 

performs calibrations in accordance with fee schedules, copies of which may be obtained from NIST.

NIST does not calibrate carpenters’ rules, machinist scales, draftsman scales, and the like. Such apparatus, if they 

require calibration, should be submitted to State or local weights and measures officials.

3.2. Standards of Mass. - The primary standard of mass for this country is United States Prototype Kilogram 20, which 

is a platinum-iridium cylinder kept at NIST. We know the value of this mass standard in terms of the International 

Prototype Kilogram, a platinum-iridium standard which is kept at the International Bureau of Weights and Measures.

 1 See Federal Register for July 1, 1959. See also next to last paragraph of 2.2.5
Units and Systems

B-8

In Colonial Times the British standards were considered the primary standards of the United States. Later, the U.S. 

avoirdupois pound was defined in terms of the Troy Pound of the Mint, which is a brass standard kept at the United States 

Mint in Philadelphia. In 1911, the Troy Pound of the Mint was superseded, for coinage purposes, by the Troy Pound of 

the Institute.

The avoirdupois pound is defined in terms of the kilogram by the relation:

1 avoirdupois pound = 0.453 592 37 kilogram.2

These changes in definition have not made any appreciable change in the value of the pound.

The grain is 1/7000 of the avoirdupois pound and is identical in the avoirdupois, troy, and apothecary systems. The troy 

ounce and the apothecary ounce differ from the avoirdupois ounce but are equal to each other, and equal to 480 grains.

The avoirdupois ounce is equal to 437.5 grains.

3.2.1. Mass and Weight. - The mass of a body is a measure of its inertial property or how much matter it contains. 

The weight of a body is a measure of the force exerted on it by gravity or the force needed to support it. Gravity on 

earth gives a body a downward acceleration of about 9.8 m/s2

. (In common parlance, weight is often used as a 

synonym for mass as in weights and measures.) The incorrect use of weight in place of mass should be phased out, 

and the term mass used when mass is meant.

Standards of mass are ordinarily calibrated by comparison to a reference standard of mass. If two objects are 

compared on a balance and give the same balance indication, they have the same "mass" (excluding the effect of air 

buoyancy). The forces of gravity on the two objects are balanced. Even though the value of the acceleration of 

gravity, g, is different from location to location, because the two objects of equal mass in the same location (where 

both masses are acted upon by the same g) will be affected in the same manner and by the same amount by any 

change in the value of g, the two objects will balance each other under any value of g.

However, on a spring balance the mass of a body is not balanced against the mass of another body. Instead, the 

gravitational force on the body is balanced by the restoring force of a spring. Therefore, if a very sensitive spring 

balance is used, the indicated mass of the body would be found to change if the spring balance and the body were 

moved from one locality to another locality with a different acceleration of gravity. But a spring balance is usually 

used in one locality and is adjusted or calibrated to indicate mass at that locality.

3.2.2. Effect of Air Buoyancy. - Another point that must be taken into account in the calibration and use of 

standards of mass is the buoyancy or lifting effect of the air. A body immersed in any fluid is buoyed up by a force 

equal to the force of gravity on the displaced fluid. Two bodies of equal mass, if placed one on each pan of an 

equal-arm balance, will balance each other in a vacuum. A comparison in a vacuum against a known mass standard 

gives "true mass." If compared in air, however, they will not balance each other unless they are of equal volume. If 

of unequal volume, the larger body will displace the greater volume of air and will be buoyed up by a greater force 

than will the smaller body, and the larger body will appear to be of less mass than the smaller body.

The greater the difference in volume, and the greater the density of the air in which we make the comparison 

weighing, the greater will be the apparent difference in mass. For that reason, in assigning a precise numerical value 

of mass to a standard, it is necessary to base this value on definite values for the air density and the density of the 

mass standard of reference.

The apparent mass of an object is equal to the mass of just enough reference material of a specified density (at 20 C) 

that will produce a balance reading equal to that produced by the object if the measurements are done in air with a 

density of 1.2 mg/cm3 at 20 C. The original basis for reporting apparent mass is apparent mass versus brass. The 

apparent mass versus a density of 8.0 g/cm3 is the more recent definition, and is used extensively throughout the 

world. The use of apparent mass versus 8.0 g/cm3 is encouraged over apparent mass versus brass. The difference in 

these apparent mass systems is insignificant in most commercial weighing applications.

A full discussion of this topic is given in NIST Monograph 133, Mass and Mass Values, by Paul E. Pontius [for sale 

by the National Technical Information Service, 5285 Port Royal Road, Springfield, VA 22161 (COM 7450309).]

 2 See Federal Register for July 1, 1959.
Units and Systems

B-9

3.2.3. Calibrations of Standards of Mass. - Standards of mass regularly used in ordinary trade should be tested by 

State or local weights and measures officials. NIST calibrates mass standards submitted, but it does not manufacture 

or sell them. Information regarding the mass calibration service of NIST and the regulations governing the 

submission of standards of mass to NIST for calibration are contained in NIST Special Publication 250, Calibration 

and Related Measurement Services of NIST, latest edition.

3.3. Standards of Capacity. - Units of capacity or volume, being derived units, are in this country defined in terms of 

linear units. Laboratory standards have been constructed and are maintained at NIST. These have validity only by 

calibration with reference either directly or indirectly to the linear standards. Similarly, NIST has made and distributed 

standards of capacity to the several States. Other standards of capacity have been verified by calibration for a variety of 

uses in science, technology, and commerce.

3.3.1. Calibrations of Standards of Capacity. - NIST makes calibrations on capacity or volume standards that are 

in the customary units of trade; that is, the gallon, its multiples, and submultiples, or in metric units. Further, NIST 

calibrates precision-grade volumetric glassware which is normally in metric units. NIST makes calibrations in 

accordance with fee schedules, copies of which may be obtained from NIST.

3.4. Maintenance and Preservation of Fundamental Standard of Mass. - It is a statutory responsibility of NIST to 

maintain and preserve the national standard of mass at NIST and to realize all the other base units. The U.S. Prototype 

Kilogram maintained at NIST is fully protected by an alarm system. All measurements made with this standard are 

conducted in special air-conditioned laboratories to which the standard is taken a sufficiently long time before the 

observations to ensure that the standard will be in a state of equilibrium under standard conditions when the 

measurements or comparisons are made. Hence, it is not necessary to maintain the standard at standard conditions, but 

care is taken to prevent large changes of temperature. More important is the care to prevent any damage to the standard 

because of careless handling.

4. Specialized Use of the Terms "Ton" and "Tonnage"

As weighing and measuring are important factors in our everyday lives, it is quite natural that questions arise about the 

use of various units and terms and about the magnitude of quantities involved. For example, the words "ton" and 

"tonnage" are used in widely different senses, and a great deal of confusion has arisen regarding the application of these 

terms.

The ton is used as a unit of measure in two distinct senses: (1) as a unit of mass, and (2) as a unit of capacity or volume.

In the first sense, the term has the following meanings:

a. The short, or net ton of 2000 pounds.

b. The long, gross, or shipper's ton of 2240 pounds.

c. The metric ton of 1000 kilograms, or 2204.6 pounds.

In the second sense (capacity), it is usually restricted to uses relating to ships and has the following meaning:

a. The register ton of 100 cubic feet.

b. The measurement ton of 40 cubic feet.

c. The English water ton of 224 British Imperial gallons.

In the United States and Canada the ton (mass) most commonly used is the short ton. In Great Britain, it is the long ton, 

and in countries using the metric system, it is the metric ton. The register ton and the measurement ton are capacity or 

volume units used in expressing the tonnage of ships. The English water ton is used, chiefly in Great Britain, in statistics 

dealing with petroleum products.
Units and Systems

B-10

There have been many other uses of the term ton such as the timber ton of 40 cubic feet and the wheat ton of 20 bushels, 

but their use has been local and the meanings have not been consistent from one place to another.

Properly, the word "tonnage" is used as a noun only in respect to the capacity or volume and dimensions of ships, and to 

the amount of the ship's cargo. There are two distinct kinds of tonnage; namely, vessel tonnage and cargo tonnage and 

each of these is used in various meanings.

The several kinds of vessel tonnage are as follows:

Gross tonnage, or gross register tonnage, is the total cubical capacity or volume of a ship expressed in register tons of 100 

cubic feet, or 2.83 cubic meters, less such space as hatchways, bakeries, galleys, etc., as are exempted from measurement 

by different governments. There is some lack of uniformity in the gross tonnages as given by different nations due to lack 

of agreement on the spaces that are to be exempted. Official merchant marine statistics of most countries are published in 

terms of the gross register tonnage. Press references to ship tonnage are usually to the gross tonnage.

The net tonnage, or net register tonnage, is the gross tonnage less the different spaces specified by maritime nations in 

their measurement rules and laws. The spaces deducted are those totally unavailable for carrying cargo, such as the 

engine room, coal bunkers, crew quarters, chart and instrument room, etc. The net tonnage is used in computing how 

much cargo that can be loaded on a ship. It is used as the basis for wharfage and other similar charges.

The register under-deck tonnage is the cubical capacity of a ship under her tonnage deck expressed in register tons. In a 

vessel having more than one deck, the tonnage deck is the second from the keel.

There are several variations of displacement tonnage.

The dead weight tonnage is the difference between the "loaded" and "light" displacement tonnages of a vessel. It is 

expressed in terms of the long ton of 2240 pounds, or the metric ton of 2204.6 pounds, and is the weight of fuel, 

passengers, and cargo that a vessel can carry when loaded to its maximum draft.

The second variety of tonnage, cargo tonnage, refers to the weight of the particular items making up the cargo. In 

overseas traffic it is usually expressed in long tons of 2240 pounds or metric tons of 2204.6 pounds. The short ton is only 

occasionally used. Therefore, the cargo tonnage is very distinct from vessel tonnage. 
General Tables of Units of Measurement

C-1

Appendix C

General Tables of Units of Measurement

These tables have been prepared for the benefit of those requiring tables of units for occasional ready reference. In 

Section 4 of this Appendix, the tables are carried out to a large number of decimal places and exact values are indicated by underlining. In most of the other tables, only a limited number of decimal places are given, therefore 

making the tables better adopted to the average user.

1. TABLES OF METRIC UNITS OF MEASUREMENT

In the metric system of measurement, designations of multiples and subdivisions of any unit may be arrived at by 

combining with the name of the unit the prefixes deka, hecto, and kilo meaning, respectively, 10, 100, and 1 000, 

and deci, centi, and milli, meaning, respectively, one-tenth, one-hundredth, and one- thousandth. In some of the 

following metric tables, some such multiples and subdivisions have not been included for the reason that these have 

little, if any currency in actual usage.

In certain cases, particularly in scientific usage, it becomes convenient to provide for multiples larger than 1 000 and 

for subdivisions smaller than one-thousandth. Accordingly, the following prefixes have been introduced and these 

are now generally recognized:

yotta, (Y) meaning 1024 deci, (d), meaning 10-1

zetta, (Z), meaning 1021 centi, (c), meaning 10-2

exa, (E), meaning 1018 milli, (m), meaning 10-3

peta, (P), meaning 1015 micro, (μ), meaning 10-6

tera, (T), meaning 1012 nano, (n), meaning 10-9

giga, (G), meaning 109 pico, (p), meaning 10-12

mega, (M), meaning 106 femto, (f), meaning 10-15

kilo, (k), meaning 103 atto, (a), meaning 10-18

hecto, (h), meaning 102 zepto, (z), meaning 10-21

deka, (da), meaning 101 yocto, (y), meaning 10-24

 Thus a kilometer is 1000 meters and a millimeter is 0.001 meter.

Units of Length

10 millimeters (mm) = 1 centimeter (cm)

10 centimeters = 1 decimeter (dm) = 100 millimeters

10 decimeters = 1 meter (m) = 1000 millimeters

10 meters = 1 dekameter (dam)

10 dekameters = 1 hectometer (hm) = 100 meters

10 hectometers = 1 kilometer (km) = 1000 meters
General Tables of Units of Measurement

C-2

Units of Area

100 square millimeters (mm2

) = 1 square centimeter (cm2)

100 square centimeters = 1 square decimeter (dm2

)

100 square decimeters = 1 square meter (m2

)

100 square meters = 1 square dekameter (dam2

) = 1 are

100 square dekameters = 1 square hectometer (hm2

) = 1 hectare (ha)

100 square hectometers = 1 square kilometer (km2

)

Units of Liquid Volume

10 milliliters (mL) = 1 centiliter (cL)

10 centiliters = 1 deciliter (dL) = 100 milliliters

10 deciliters = 1 liter1

10 liters = 1 dekaliter (daL)

= 1000 milliliters

10 dekaliters = 1 hectoliter (hL) = 100 liters

10 hectoliters = 1 kiloliter (kL) = 1000 liters

Units of Volume

1000 cubic millimeters (mm3

) = 1 cubic centimeter (cm3)

1000 cubic centimeters = 1 cubic decimeter (dm3

)

= 1 000 000 cubic millimeters

1000 cubic decimeters = 1 cubic meter (m3

)

= 1 000 000 cubic centimeters

= 1 000 000 000 cubic millimeters

Units of Mass

10 milligrams (mg) = 1 centigram (cg)

10 centigrams = 1 decigram (dg) = 100 milligrams

10 decigrams = 1 gram (g) = 1000 milligrams

10 grams = 1 dekagram (dag)

10 dekagrams = 1 hectogram (hg) = 100 grams

10 hectograms = 1 kilogram (kg) = 1000 grams

1000 kilograms = 1 megagram (Mg) or 1 metric ton(t)

 1 By action of the 12th General Conference on Weights and Measures (1964) the liter is a special name for the cubic 

decimeter. 
General Tables of Units of Measurement

C-3

2. TABLES OF U.S. UNITS OF MEASUREMENT2

In these tables where foot or mile is underlined, it is survey foot or U.S. statute mile rather than international foot or 

mile that is meant.

Units of Length

12 inches (in) = 1 foot (ft)

3 feet = 1 yard (yd)

16-1/2 feet = 1 rod (rd), pole, or perch

40 rods = 1 furlong (fur) = 660 feet

8 furlongs = 1 U.S. statute mile (mi) = 5280 feet

1852 meters = 6076.115 49 feet (approximately)

= 1 international nautical mile

Units of Area3

144 square inches (in2) = 1 square foot (ft2)

9 square feet = 1 square yard (yd2

)

= 1296 square inches

272-1/4 square feet = 1 square rod (sq rd)

160 square rods = 1 acre = 43 560 square feet

640 acres = 1 square mile (mi2)

1 mile square = 1 section of land

6 miles square = 1 township

= 36 sections = 36 square miles

Units of Volume3

1728 cubic inches (in3

) = 1 cubic foot (ft3)

27 cubic feet = 1 cubic yard (yd3

)

Gunter's or Surveyors Chain Units of Measurement

0.66 foot (ft) = 1 link (li)

100 links = 1 chain (ch)

= 4 rods = 66 feet

80 chains = 1 U.S. statute mile (mi)

= 320 rods = 5280 feet

 2 This section lists units of measurement that have traditionally been used in the United States. In keeping with the 

Omnibus Trade and Competitiveness Act of 1988, the ultimate objective is to make the International System of 

Units the primary measurement system used in the United States.

3 Squares and cubes of customary but not of metric units are sometimes expressed by the use of abbreviations rather 

than symbols. For example, sq ft means square foot, and cu ft means cubic foot.
General Tables of Units of Measurement

C-4

Units of Liquid Volume4

4 gills (gi) = 1 pint (pt)= 28.875 cubic inches

2 pints = 1 quart (qt) = 57.75 cubic inches

4 quarts = 1 gallon (gal) = 231 cubic inches 

= 8 pints = 32 gills

Apothecaries Units of Liquid Volume

60 minims = 1 fluid dram (fl dr or ƒ ʒ )

= 0.225 6 cubic inch )

8 fluid drams = 1 fluid ounce (fl oz or ƒ ℥ )

 = 1.804 7 cubic inches

16 fluid ounces = 1 pint (pt)

= 28.875 cubic inches 

= 128 fluid drams

2 pints = 1 quart (qt) = 57.75 cubic inches 

= 32 fluid ounces = 256 fluid drams

4 quarts = 1 gallon (gal) = 231 cubic inches 

= 128 fluid ounces = 1024 fluid drams

Units of Dry Volume5

2 pints (pt) = 1 quart (qt) = 67.200 6 cubic inches

8 quarts = 1 peck (pk) = 537.605 cubic inches 

= 16 pints

4 pecks = 1 bushel (bu) = 2150.42 cubic inches

= 32 quarts

 4 When necessary to distinguish the liquid pint or quart from the dry pint or quart, the word "liquid" or the 

abbreviation "liq" should be used in combination with the name or abbreviation of the liquid unit.

5 When necessary to distinguish dry pint or quart from the liquid pint or quart, the word "dry" should be used in 

combination with the name or abbreviation of the dry unit.
General Tables of Units of Measurement

C-5

Avoirdupois Units of Mass6

[The "grain" (gr) is the same in avoirdupois, troy, and apothecaries units of mass.]

27-11/32 grains = 1 dram (dr)

16 drams = 1 ounce (oz)

= 437-1/2 grains

16 ounces = 1 pound (lb)

= 256 drams

= 7000 grains

100 pounds = 1 hundredweight (cwt)7

20 hundredweights = 1 ton

= 2000 pounds7

In "gross" or "long" measure, the following values are recognized:

112 pounds = 1 gross or long hundredweight 7

20 gross or long hundredweights = 1 gross or long ton

= 2240 pounds7

Troy Units of Mass

[The "grain" is the same in avoirdupois, troy, and apothecaries units of mass.]

24 grains = 1 pennyweight (dwt)

20 pennyweights = 1 ounce troy (oz t)= 480 grains

12 ounces troy = 1 pound troy (lb t)

= 240 pennyweights = 5760 grains

Apothecaries Units of Mass

[The "grain" is the same in avoirdupois, troy, and apothecaries units of mass.]

20 grains = 1 scruple (s ap or ℈ )

3 scruples = 1 dram apothecaries (dr ap or ʒ )

= 60 grains

8 drams apothecaries = 1 ounce apothecaries (oz ap or ℥ )

= 24 scruples = 480 grains 

12 ounces apothecaries = 1 pound apothecaries (lb ap)

= 96 drams apothecaries 

= 288 scruples = 5760 grains

 6 When necessary to distinguish the avoirdupois dram from the apothecaries dram, or to distinguish the avoirdupois

dram or ounce from the fluid dram or ounce, or to distinguish the avoirdupois ounce or pound from the troy or 

apothecaries ounce or pound, the word "avoirdupois" or the abbreviation "avdp" should be used in combination with 

the name or abbreviation of the avoirdupois unit.

7 When the terms "hundredweight" and "ton" are used unmodified, they are commonly understood to mean the 100-

pound hundredweight and the 2000-pound ton, respectively; these units may be designated "net" or "short" when 

necessary to distinguish them from the corresponding units in gross or long measure.
General Tables of Units of Measurement

C-6

3. NOTES ON BRITISH UNITS OF MEASUREMENT

In Great Britain, the yard, the avoirdupois pound, the troy pound, and the apothecaries pound are identical with the 

units of the same names used in the United States. The tables of British linear measure, troy mass, and apothecaries 

mass are the same as the corresponding United States tables, except for the British spelling "drachm" in the table of 

apothecaries mass. The table of British avoirdupois mass is the same as the United States table up to 1 pound; above 

that point the table reads:

14 pounds = 1 stone

2 stones = 1 quarter = 28 pounds

4 quarters = 1 hundredweight = 112 pounds

 20 hundredweight = 1 ton = 2240 pounds

The present British gallon and bushel--known as the "Imperial gallon" and "Imperial bushel"--are, respectively, 

about 20 percent and 3 percent larger than the United States gallon and bushel. The Imperial gallon is defined as the 

volume of 10 avoirdupois pounds of water under specified conditions, and the Imperial bushel is defined as 8 

Imperial gallons. Also, the subdivision of the Imperial gallon as presented in the table of British apothecaries fluid 

measure differs in two important respects from the corresponding United States subdivision, in that the Imperial 

gallon is divided into 160 fluid ounces (whereas the United States gallon is divided into 128 fluid ounces), and a 

"fluid scruple" is included. The full table of British measures of capacity (which are used alike for liquid and for dry 

commodities) is as follows:

 4 gills = 1 pint

 2 pints = 1 quart

 4 quarts = 1 gallon

 2 gallons = 1 peck

 8 gallons (4 pecks) = 1 bushel

 8 bushels = 1 quarter

The full table of British apothecaries measure is as follows:

20 minims = 1 fluid scruple

3 fluid scruples = 1 fluid drachm

= 60 minims

8 fluid drachms = 1 fluid ounce

 20 fluid ounces = 1 pint

8 pints = 1 gallon (160 fluid ounces)
General Tables of Units of Measurement

C-7

4. TABLES OF UNITS OF MEASUREMENT

(all underlined figures are exact)

Units of Length - International Measure8

Units Inches Feet Yards Miles Centimeters Meters

1 inch = 1 0.083 333 33 0.027 777 78 0.000 015 782 83 2.54 0.025 4

1 foot = 12 1 0.333 333 3 0.000 189 393 9 30.48 0.304 8

1 yard = 36 3 1 0.000 568 181 8 91.44 0.914 4

1 mile = 63 360 5 280 1 760 1 160 934.4 1609.344

1 centimeter = 0.393 700 8 0.032 808 40 0.010 936 13 0.000 006 213 712 1 0.01

1 meter = 39.370 08 3.280 840 1.093 613 0.000 621 371 2 100 1

Units of Length - Survey Measure8

Units Links Feet Rods Chains Miles Meters

1 link = 1 0.66 0.04 0.01 0.000 125 0.201 168 4

1 foot = 1.515 152 1 0.060 606 06 0.015 151 52 0.000 189 393 9 0.304 800 6

1 rod = 25 16.5 1 0.25 0.003 125 5.029 210

1 chain = 100 66 4 1 0.0125 20.116 84

1 mile = 8 000 5 280 320 80 1 1609.347

1 meter = 4.970 960 3.280 833 0.198 838 4 0.049 709 60 0.000 621 369 9 1

 8

 One international foot = 0.999 998 survey foot (exactly)

 One international mile = 0.999 998 survey mile (exactly)

Note: 1 survey foot = 1200/3937 meter (exactly)

 1 international foot = 12 x 0.0254 meter (exactly)

 1 international foot = 0.0254 x 39.37 survey foot (exactly)
General Tables of Units of Measurement

C-8

Units of Area - International Measure9

(all underlined figures are exact)

 

Units Square Inches Square Feet Square Yards

1 square inch = 1 0.006 944 444 0.000 771 604 9

1 square foot = 144 1 0.111 111 1

1 square yard = 1296 9 1

1 square mile = 4 014 489 600 27 878 400 3 097 600

1 square centimeter = 0.155 000 3 0.001 076 391 0.000 119 599 0

1 square meter = 1550.003 10.763 91 1.195 990

Units Square Miles Square Centimeters Square Meters

1 square inch = 0.000 000 000 249 097 7 6.451 6 0.000 645 16

1 square foot = 0.000 000 035 870 06 929.030 4 0.092 903 04

1 square yard = 0.000 000 322 830 6 8361.273 6 0.836 127 36

1 square mile = 1 25 899 881 103.36 2 589 988.110 336

1 square centimeter = 0.000 000 000 038 610 22 1 0.0001

1 square meter = 0.000 000 386 102 2 10 000 1

Units of Area - Survey Measure9

Units Square Feet Square Rods Square Chains Acres

1 square foot = 1 0.003 673 095 0.000 229 568 4 0.000 022 956 84

1 square rod = 272.25 1 0.062 5 0.006 25

1 square chain = 4356 16 1 0.1

1 acre = 43 560 160 10 1

1 square mile = 27 878 400 102 400 6400 640

1 square meter = 10.763 87 0.039 536 70 0.002 471 044 0.000 247 104 4

1 hectare = 107 638.7 395.367 0 24.710 44 2.471 044

 9 One square survey foot = 1.000 004 square international feet

 One square survey mile = 1.000 004 square international miles
General Tables of Units of Measurement

C-9

Units Square Miles Square Meters Hectares

1 square foot = 0.000 000 035 870 06 0.092 903 41 0.000 009 290 341

1 square rod = 0.000 009 765 625 25.292 95 0.002 529 295

1 square chain = 0.000 156 25 404.687 3 0.040 468 73

1 acre = 0.001 562 5 4 046.873 0.404 687 3

1 square mile = 1 2 589 998 258.999 8

1 square meter = 0.000 000 386 100 6 1 0.000 1

1 hectare = 0.003 861 006 10 000 1

Units of Volume

(all underlined figures are exact)

Units Cubic Inches Cubic Feet Cubic Yards

1 cubic inch = 1 0.000 578 703 7 0.000 021 433 47

1 cubic foot = 1728 1 0.037 037 04

1 cubic yard = 46 656 27 1

1 cubic centimeter = 0.061 023 74 0.000 035 314 67 0.000 001 307 951

1 cubic decimeter = 61.023 74 0.035 314 67 0.001 307 951

1 cubic meter = 61 023.74 35.314 67 1.307 951

Units Milliliters

(Cubic Centimeters)

Liters

(Cubic Decimeters) Cubic Meters

1 cubic inch = 16.387 064 0.016 387 064 0.000 016 387 064

1 cubic foot = 28 316.846 592 28.316 846 592 0.028 316 846 592

1 cubic yard = 764 554.857 984 764.554 857 984 0.764 554 857 984

1 cubic centimeter = 1 0.001 0.000 001

1 cubic decimeter = 1000 1 0.001

1 cubic meter = 1 000 000 1000 1
General Tables of Units of Measurement

C-10

Units of Capacity or Volume - Dry Volume Measure

Units Dry Pints Dry Quarts Pecks Bushels

1 dry pint = 1 0.5 0.062 5 0.015 625

1 dry quart = 2 1 0.125 0.031 25

1 peck = 16 8 1 0.25

1 bushel = 64 32 4 1

1 cubic inch = 0.029 761 6 0.014 880 8 0.001 860 10 0.000 465 025

1 cubic foot = 51.428 09 25.714 05 3.214 256 0.803 563 95

1 liter = 1.816 166 0.908 083 0 0.113 510 4 0.028 377 59

1 cubic meter = 1 816.166 908.083 0 113.510 4 28.377 59

Units Cubic Inches Cubic Feet Liters Cubic Meters

1 dry pint = 33.600 312 5 0.019 444 63 0.550 610 5 0.000 550 610 5

1 dry quart = 67.200 625 0.038 889 25 1.101 221 0.001 101 221

1 peck = 537.605 0.311 114 8.809 768 0.008 809 768

1 bushel = 2 150.42 1.244 456 35.239 07 0.035 239 07

1 cubic inch = 1 0.000 578 703 7 0.016 387 06 0.000 016 387 06

1 cubic foot = 1728 1 28.316 85 0.028 316 85

1 liter = 61.023 74 0.035 314 67 1 0.001

1 cubic meter = 61 023.74 35.314 67 1000 1
General Tables of Units of Measurement

C-11

Units of Capacity or Volume - Liquid Volume Measure

(All underlined figures are exact)

Units Minims Fluid Drams Fluid Ounces Gills

1 minim = 1 0.016 666 67 0.002 083 333 0.000 520 833 3

1 fluid dram = 60 1 0.125 0.031 25

1 fluid ounce = 480 8 1 0.25

1 gill = 1920 32 4 1

1 liquid pint = 7680 128 16 4

1 liquid quart = 15 360 256 32 8

1 gallon = 61 440 1024 128 32

1 cubic inch = 265.974 0 4.432 900 0.554 112 6 0.138 528 1

1 cubic foot = 459 603.1 7660.052 957.506 5 239.376 6

1 milliliter = 16.230 73 0.270 512 2 0.033 814 02 0.008 453 506

1 liter = 16 230.73 270.512 2 33.814 02 8.453 506

Units Liquid Pints Liquid Quarts Gallons Cubic Inches

1 minim = 0.000 130 208 3 0.000 065 104 17 0.000 016 276 04 0.003 759 766

1 fluid dram = 0.007 812 5 0.003 906 25 0.000 976 562 5 0.225 585 94

1 fluid ounce = 0.062 5 0.031 25 0.007 812 5 1.804 687 5

1 gill = 0.25 0.125 0.031 25 7.218 75

1 liquid pint = 1 0.5 0.125 28.875

1 liquid quart = 2 1 0.25 57.75

1 gallon = 8 4 1 231

1 cubic inch = 0.034 632 03 0.017 316 02 0.004 329 004 1

1 cubic foot = 59.844 16 29.922 08 7.480 519 1728

1 milliliter = 0.002 113 376 0.001 056 688 0.000 264 172 1 0.061 023 74

1 liter = 2.113 376 1.056 688 0.264 172 1 61.023 74
General Tables of Units of Measurement

C-12

Units Cubic Feet Milliliters Liters

1 minim = 0.000 002 175 790 0.061 611 52 0.000 061 611 52

1 fluid dram = 0.000 130 547 4 3.696 691 0.003 696 691

1 fluid ounce = 0.001 044 379 29.573 53 0.029 573 53

1 gill = 0.004 177 517 118.294 1 0.118 294 1

1 liquid pint = 0.016 710 07 473.176 5 0.473 176 5

1 liquid quart = 0.033 420 14 946.352 9 0.946 352 9

1 gallon = 0.133 680 6 3785.412 3.785 412

1 cubic inch = 0.000 578 703 7 16.387 06 0.016 387 06

1 cubic foot = 1 28 316.85 28.316 85

1 milliliter = 0.000 035 314 67 1 0.001

1 liter = 0.035 314 67 1000 1

Units of Mass Not Less Than Avoirdupois Ounces

(all underlined figures are exact)

Units Avoirdupois

Ounces

Avoirdupois

Pounds Short Hundred-weights Short tons

1 avoirdupois ounce = 1 0.0625 0.000 625 0.000 031 25

1 avoirdupois pound = 16 1 0.01 0.000 5

1 short 

hundredweight = 1600 100 1 0.05

1 short ton = 32 000 2000 20 1

1 long ton = 35 840 2240 22.4 1.12

1 kilogram = 35.273 96 2.204 623 0.022 046 23 0.001 102 311

1 metric ton = 35 273.96 2204.623 22.046 23 1.102 311

Units Long Tons Kilograms Metric Tons

1 avoirdupois ounce = 0.000 027 901 79 0.028 349 523 125 0.000 028 349 523 125

1 avoirdupois pound = 0.000 446 428 6 0.453 592 37 0.000 453 592 37

1 short hundredweight = 0.044 642 86 45.359 237 0.045 359 237

1 short ton = 0.892 857 1 907.184 74 0.907 184 74

1 long ton = 1 1016.046 908 8 1.016 046 908 8

1 kilogram = 0.000 984 206 5 1 0.001

1 metric ton = 0.984 206 5 1000 1
General Tables of Units of Measurement

C-13

Units of Mass Not Greater Than Pounds and Kilograms

(all underlined figures are exact)

Units Grains Apothecaries Scruples Pennyweights Avoirdupois Drams

1 grain = 1 0.05 0.041 666 67 0.036 571 43

1 apoth. scruple = 20 1 0.833 333 3 0.731 428 6

1 pennyweight = 24 1.2 1 0.877 714 3

1 avdp. dram = 27.343 75 1.367 187 5 1.139 323 1

1 apoth. dram = 60 3 2.5 2.194 286

1 avdp. ounce = 437.5 21.875 18.229 17 16

1 apoth. or troy oz. = 480 24 20 17.554 29

1 apoth. or troy pound = 5760 288 240 210.651 4

1 avdp. pound = 7000 350 291.666 7 256

1 milligram = 0.015 432 36 0.000 771 617 9 0.000 643 014 9 0.000 564 383 4

1 gram = 15.432 36 0.771 617 9 0.643 014 9 0.564 383 4

1 kilogram = 15432.36 771.617 9 643.014 9 564.383 4

Units Apothecaries Drams Avoirdupois Ounces Apothecaries or Troy 

Ounces

Apothecaries or Troy 

Pounds

1 grain = 0.016 666 67 0.002 285 714 0.002 083 333 0.000 173 611 1

1 apoth. scruple = 0.333 333 3 0.045 714 29 0.041 666 67 0.003 472 222

1 pennyweight = 0.4 0.054 857 14 0.05 0.004 166 667

1 avdp. dram = 0.455 729 2 0.062 5 0.56 966 15 0.004 747 179

1 apoth. dram = 1 0.137 142 9 0.125 0.010 416 67

1 avdp. ounce = 7.291 667 1 0.911 458 3 0.075 954 86

1 apoth. or troy ounce = 8 1.097 143 1 0.083 333 333

1 apoth. or troy pound = 96 13.165 71 12 1

1 avdp. pound = 116.666 7 16 14.583 33 1.215 278

1 milligram = 0.000 257 206 0 0.000 035 273 96 0.000 032 150 75 0.000 002 679 229

1 gram = 0.257 206 0 0.035 273 96 0.032 150 75 0.002 679 229

1 kilogram = 257.206 0 35.273 96 32.150 75 2.679 229
General Tables of Units of Measurement

C-14

Units Avoirdupois Pounds Milligrams Grams Kilograms

1 grain = 0.000 142 857 1 64.798 91 0.064 798 91 0.000 064 798 91

1 apoth. scruple = 0.002 857 143 1295.978 2 1.295 978 2 0.001 295 978 2

1 pennyweight = 0.003 428 571 1555.173 84 1.555 173 84 0.001 555 173 84

1 avdp. dram = 0.003 906 25 1771.845 195 312 5 1.771 845 195 312 5 0.001 771 845 195 312 5

1 apoth. dram = 0.008 571 429 3887.934 6 3.887 934 6 0.003 887 934 6

1 avdp. ounce = 0.062 5 28 349.523 125 28.349 523 125 0.028 349 523 125

1 apoth. or troy 

ounce = 0.068 571 43 31 103.476 8 31.103 476 8 0.031 103 476 8

1 apoth. or troy 

pound = 0.822 857 1 373 241.721 6 373.241 721 6 0.373 241 721 6

1 avdp. pound = 1 453 592.37 453.592 37 0.453 592 37

1 milligram = 0.000 002 204 623 1 0.001 0.000 001

1 gram = 0.002 204 623 1000 1 0.001

1 kilogram = 2.204 623 1 000 000 1000 1

5. TABLES OF EQUIVALENTS

In these tables it is necessary to differentiate between the "international foot" and the "survey foot" the survey foot is 

underlined.

When the name of a unit is enclosed in brackets (thus, [1 hand] . . . ), this indicates (1) that the unit is not in general 

current use in the United States, or (2) that the unit is believed to be based on "custom and usage" rather than on 

formal authoritative definition.

Equivalents involving decimals are, in most instances, rounded off to the third decimal place except where they are 

exact, in which cases these exact equivalents are so designated. The equivalents of the imprecise units "tablespoon" 

and "teaspoon" are rounded to the nearest milliliter.

UNITS OF LENGTH

0.1 nanometer (exactly).

0.000 1 micrometer (exactly).

angstrom ()

10

0.000 000 004 inch.

----------------------- 0.000 000 1 millimeter (exactly).

120 fathoms (exactly).

1 cable's length----------------------- 720 feet (exactly).

219 meters.

1 centimeter (cm)---------------------- 0.393 7 inch.

 10 The angstrom is basically defined as 10-10 meter.
General Tables of Units of Measurement

C-15

1 chain (ch)--------------------------- 66 feet (exactly).

 (Gunter's or surveyors) 20.116 8 meters.

1 decimeter (dm)----------------------- 3.937 inches.

1 dekameter (dam)---------------------- 32.808 feet.

6 feet (exactly).

1 fathom------------------------------- 1.828 8 meters.

1 foot (ft)---------------------------- 0.304 8 meter (exactly).

 10 chains (surveyors) (exactly).

1 furlong (fur)------------------------ 660 feet (exactly).

1/8 U.S. statute mile (exactly).

201.168 meters.

[1 hand]------------------------------- 4 inches.

1 inch (in)---------------------------- 2.54 centimeters (exactly).

1 kilometer (km)----------------------- 0.621 mile.

1 league (land)------------------------ 3 U.S. statute miles (exactly).

4.828 kilometers.

0.66 foot (exactly).

1 link (li) (Gunter's or surveyors)---- 0.201 168 meter.

1 meter (m)---------------------------- 39.37 inches.

1.094 yards.

1 micrometer--------------------------- 0.001 millimeter (exactly).

0.000 039 37 inch.

0.001 inch (exactly).

1 mil---------------------------------- 0.025 4 millimeter (exactly).

1 mile (mi) (U.S. statute)11

1.609 kilometers.

---------- 5280 feet survey (exactly).

1 mile (mi) (international)------------ 5280 feet international (exactly).

 11 The term "statute mile" originated with Queen Elizabeth I who changed the definition of the mile from the Roman 

mile of 5000 feet to the statute mile of 5280 feet. The international mile and the U.S. statute mile differ by about 3 

millimeters although both are defined as being equal to 5280 feet. The international mile is based on the 

international foot (0.3048 meter) whereas the U.S. statute mile is based on the survey foot (1200/3937 meter).
General Tables of Units of Measurement

C-16

1 mile (mi) (international nautical)12

1.151 survey miles.

1.852 kilometers (exactly).

1 millimeter (mm)---------------------- 0.039 37 inch.

 0.001 micrometer (exactly).

1 nanometer (nm)----------------------- 0.000 000 039 37 inch.

 

0.013 837 inch (exactly).

1 Point (typography)------------------- 1/72 inch (approximately).

0.351 millimeter.

1 rod (rd), pole, or perch------------- 16 1/2 feet (exactly).

5.029 2 meters.

1 yard (yd)---------------------------- 0.914 4 meter (exactly).

UNITS OF AREA

43 560 square feet (exactly).

1 acre13---------------------------- 0.405 hectare.

1 are------------------------------ 119.599 square yards.

 0.025 acre.

1 hectare-------------------------- 2.471 acres.

[1 square (building)]--------------- 100 square feet.

1 square centimeter (cm2

)----------- 0.155 square inch.

1 square decimeter (dm2

)------------ 15.500 square inches.

1 square foot (ft2

)----------------- 929.030 square centimeters.

1 square inch (in2

)----------------- 6.451 6 square centimeters (exactly).

1 square kilometer (km2

)------------ 247.104 acres.

 0.386 square mile.

1 square meter (m2

)----------------- 1.196 square yards.

 10.764 square feet.

1 square mile (mi2

)----------------- 258.999 hectares.

 12 The international nautical mile of 1 852 meters (6 076.115 49...feet) was adopted effective July 1, 1954, for use in 

the United States. The value formerly used in the United States was 6 080.20 feet = 1 nautical (geographical or sea) 

mile.

13 The question is often asked as to the length of a side of an acre of ground. An acre is a unit of area containing 

43 560 square feet. It is not necessarily square, or even rectangular. But, if it is square, then the length of a side is 

equal to 43560 ft 208.710 ft 2 = (not exact).
General Tables of Units of Measurement

C-17

1 square millimeter (mm2

)----------- 0.002 square inch.

1 square rod (rd2

), sq pole,

 or sq perch----------------------- 25.293 square meters.

1 square yard (yd2

)----------------- 0.836 square meter.

UNITS OF CAPACITY OR VOLUME

1 barrel (bbl), liquid----------------- 31 to 42 gallons.14

1 barrel (bbl), standard for fruits, 7056 cubic inches.

 vegetables, and other dry------------ 105 dry quarts.

 commodities, except cranberries 3.281 bushels, struck measure.

5 826 cubic inches.

1 barrel (bbl), standard, cranberry---- 86 45/64 dry quarts.

 2.709 bushels, struck measure.

2150.42 cubic inches (exactly).

1 bushel (bu) (U.S.) struck measure---- 35.238 liters.

2 747.715 cubic inches.

[1 bushel, heaped (U.S.)]-------------- 1.278 bushels, struck measure.15

[1 bushel (bu) (British Imperial) 1.032 U.S. bushels, struck measure 

(struck measure)]---------------------- 2219.36 cubic inches. 

1 cord (cd) (firewood)----------------- 128 cubic feet (exactly).

1 cubic centimeter (cm3

)--------------- 0.061 cubic inch.

1 cubic decimeter (dm3

)---------------- 61.024 cubic inches.

1 cubic foot (ft3

)--------------------- 7.481 gallons.

28.316 cubic decimeters. 

 0.554 fluid ounce.

1 cubic inch (in3

)------------------------ 4.433 fluid drams.

 16.387 cubic centimeters.

 14 There are a variety of "barrels" established by law or usage. For example, Federal taxes on fermented liquors are 

based on a barrel of 31 gallons; many State laws fix the "barrel for liquids" as 31-1/2 gallons; one State fixes a 36-

gallon barrel for cistern measurement; Federal law recognizes a 40-gallon barrel for "proof spirits"; by custom, 42 

gallons comprise a barrel of crude oil or petroleum products for statistical purposes, and this equivalent is 

recognized "for liquids" by four States. 

15 Frequently recognized as 1-1/4 bushels, struck measure.
General Tables of Units of Measurement

C-18

1 cubic meter (m3

)--------------------- 1.308 cubic yards.

1 cubic yard (yd3

)--------------------- 0.765 cubic meter.

8 fluid ounces (exactly).

1 cup, measuring----------------------- 237 milliliters.

 1/2 liquid pint (exactly).

1 dekaliter (daL)---------------------- 2.642 gallons.

 1.135 pecks.

 1/8 fluid ounce (exactly).

1 dram, fluid (or liquid) (fl dr 0.226 cubic inch.

or ƒ ʒ ) (U.S.)------------------------ 3.697 milliliters.

 1.041 British fluid drachms.

 0.961 U.S. fluid dram.

[1 drachm, fluid (fl dr) (British)]---- 0.217 cubic inch.

 3.552 milliliters.

 231 cubic inches (exactly). 

3.785 liters.

1 gallon (gal) (U.S.)------------------ 0.833 British gallon.

 128 U.S. fluid ounces (exactly).

 277.42 cubic inches.

 1.201 U.S. gallons.

[1 gallon (gal) (British Imperial)]---- 4.546 liters.

 160 British fluid ounces (exactly).

 7.219 cubic inches.

1 gill (gi)---------------------------- 4 fluid ounces (exactly).

0.118 liter.

1 hectoliter (hL)---------------------- 26.418 gallons.

 2.838 bushels.

1.057 liquid quarts.

1 liter (1 cubic decimeter exactly)---- 0.908 dry quart.

 61.025 cubic inches 

 0.271 fluid dram.

1 milliliter (mL)---------------------- 16.231 minims.

 0.061 cubic inch.

1 ounce, fluid (or liquid) (fl oz 1.805 cubic inches.

or ƒ ℥ )(U.S.)------------------------- 29.573 milliliters.

 1.041 British fluid ounces.

0.961 U.S. fluid ounce.

[1 ounce, fluid (fl oz) (British)]----- 1.734 cubic inches.

 28.412 milliliters.

1 peck (pk)---------------------------- 8.810 liters.
General Tables of Units of Measurement

C-19

33.600 cubic inches.

1 pint (pt), dry----------------------- 0.551 liter.

28.875 cubic inches exactly.

1 pint (pt), liquid-------------------- 0.473 liter.

 67.201 cubic inches.

1 quart (qt), dry (U.S.)--------------- 1.101 liters.

 0.969 British quart.

57.75 cubic inches (exactly).

1 quart (qt), liquid (U.S.)------------ 0.946 liter.

 0.833 British quart.

 69.354 cubic inches.

[1 quart (qt) (British)]--------------- 1.032 U.S. dry quarts. 

 1.201 U.S. liquid quarts.

 3 teaspoons (exactly).

1 tablespoon, measuring---------------- 15 milliliters.

 4 fluid drams.

 1/2 fluid ounce (exactly).

1/3 tablespoon (exactly).

1 teaspoon, measuring------------------ 5 milliliters.

1-1/3 fluid drams.16

270.91 U.S. gallons.

1 water ton (English)------------------ 224 British Imperial gallons.

(exactly).

UNITS OF MASS

1 assay ton17 (AT)--------------------- 29.167 grams.

200 milligrams (exactly).

1 carat (c)---------------------------- 3.086 grains.

1 dram apothecaries (dr ap or ʒ )----- 60 grains (exactly).

3.888 grams.

1 dram avoirdupois (dr avdp)----------- 27-11/32 (= 27.344) grains.

1.772 grams.

 16 The equivalent "1 teaspoon = 1-1/3 fluid drams" has been found by the Bureau to correspond more closely with 

the actual capacities of "measuring" and silver teaspoons than the equivalent "1 teaspoon = 1 fluid dram," which is 

given by a number of dictionaries.

17 Used in assaying. The assay ton bears the same relation to the milligram that a ton of 2000 pounds avoirdupois 

bears to the ounce troy; hence the mass in milligrams of precious metal obtained from one assay ton of ore gives 

directly the number of troy ounces to the net ton.
General Tables of Units of Measurement

C-20

1 gamma (γ)--------------------------- 1 microgram (exactly).

1 grain-------------------------------- 64.798 91 milligrams (exactly).

1 gram (g)----------------------------- 15.432 grains.

0.035 ounce, avoirdupois.

1 hundredweight, gross or long18

(gross cwt)-------------------------- 50.802 kilograms.

112 pounds (exactly).

1 hundredweight, gross or short 100 pounds (exactly).

 (cwt or net cwt)--------------------- 45.359 kilograms.

1 kilogram (kg)------------------------ 2.205 pounds.

1 microgram (μg) [the Greek letter mu

 in combination with the letter g]--- 0.000 001 gram (exactly).

1 milligram (mg)----------------------- 0.015 grain.

437.5 grains (exactly).

1 ounce, avoirdupois (oz avdp)--------- 0.911 troy or apothecaries ounce.

28.350 grams.

1 ounce, troy or apothecaries 480 grains (exactly).

(oz t or oz ap or ℥ )---------------- 1.097 avoirdupois ounces.

31.103 grams.

1 pennyweight (dwt)-------------------- 1.555 grams.

1 point-------------------------------- 0.01 carat.

2 milligrams.

7000 grains (exactly).

1 pound, avoirdupois (lb avdp)--------- 1.215 troy or apothecaries pounds.

453.592 37 grams (exactly).

1 pound, troy or apothecaries 5760 grains (exactly).

(lb t or lb ap)---------------------- 0.823 avoirdupois pound.

373.242 grams.

1 scruple (s ap or ℈ )---------------- 20 grains (exactly).

1.296 grams.

2240 pounds (exactly).

 18 The gross or long ton and hundredweight are used commercially in the United States to only a very limited extent, 

usually in restricted industrial fields. The units are the same as the British "ton" and "hundredweight."
General Tables of Units of Measurement

C-21

1 ton, gross or long19

1.016 metric tons.

----------------- 1.12 net tons (exactly).

2204.623 pounds.

1 ton, metric (t)---------------------- 0.984 gross ton.

1.102 net tons.

2000 pounds (exactly).

1 ton, net or short-------------------- 0.893 gross ton.

0.907 metric ton.

 19 The gross or long ton and hundredweight are used commercially in the United States to a limited extent only, 

usually in restricted industrial fields. These units are the same as the British "ton" and "hundredweight."

Definitions

D-1

Appendix D

Definitions

The specific code to which the definition applies is shown in [brackets] at the end of the definition. Definitions for the 

General Code [1.10] apply to all codes in Handbook 44.

A

absolute value. The absolute value of a number is the magnitude of that number without considering the positive or 

negative sign.[2.20]

acceptance test. The first official test of a farm milk tank, at a particular location, in which the tank is accepted as 

correct. This test applies to newly constructed tanks, relocated used tanks, and recalibrated tanks.[4.42]

accurate. A piece of equipment is "accurate" when its performance or value–that is, its indications, its deliveries, its 

recorded representations, or its capacity or actual value, etc., as determined by tests made with suitable 

standards-conforms to the standard within the applicable tolerances and other performance requirements. Equipment that 

fails so to conform is "inaccurate." (Also see "correct.")[1.10]

analog or digital recorder. An element used with a belt-conveyor scale that continuously records the rate-of-flow of 

bulk material over the scale (formerly referred to as a chart recorder).[2.21] Amended 1989

analog type. A system of indication or recording in which values are presented as a series of graduations in combination 

with an indicator, or in which the most sensitive element of an indicating system moves continuously during the operation 

of the device.[1.10]

animal scale. A scale designed for weighing single heads of livestock.[2.20]

(Amended 1987)

apparent mass versus 8.0 g/cm3

. The apparent mass of an object versus 8.0 g/cm3 is the mass of material of density 

8.0 g/cm3 that produces exactly the same balance reading as the object when the comparison is made in air with a density 

of 1.2 mg/cm3 at 20 C.[3.37]

approval seal. A label, tag, stamped or etched impression, or the like, indicating official approval of a device. (Also see 

"security seal.")[1.10]

atmospheric pressure. The average atmospheric pressure agreed to exist at the meter at various ranges of elevation, 

irrespective of variations in atmospheric pressure from time to time.[3.33]

audit trail. An electronic count and/or information record of the changes to the values of the calibration or configuration 

parameters of a device. [1.10, 2.20, 2.21, 2.24, 3.30, 3.37, 5.56(a)] 

(Added 1993)

automatic bulk weighing system. A weighing system adapted to the automatic weighing of bulk commodities in 

successive drafts of predetermined amounts, automatically recording the no-load and loaded weight values and 

accumulating the net weight of each draft.[2.20]

automatic hopper scale. One adapted to the automatic weighing of bulk commodity in successive drafts of 

predetermined amounts. (This is not an "automatic-indicating scale" defined below.)[2.20]

automatic temperature or density compensation. The use of integrated or ancillary equipment to obtain from the 

output of a volumetric meter an equivalent mass, or an equivalent liquid volume at a normal temperature of 70 F and 

absolute pressure of 14.696 lb/in2 absolute.[3.34]

automatic zero-setting mechanism. Automatic means provided to maintain zero balance indication without the 

intervention of an operator.[2.20]
Definitions

D-2

automatic zero-setting mechanism (belt-conveyor scale). A zero setting device that operates automatically without 

intervention of the operator after the belt has been running empty.[2.21] (Added 2002)

automatic-indicating scale. One on which the weights of applied loads of various magnitudes are automatically 

indicated throughout all or a portion of the weighing range of the scale. (A scale that automatically weighs out commodity in predetermined drafts, such as an automatic hopper scale, a packaging scale, and the like, is not an 

"automatic-indicating" scale.)[2.20. 2.22]

auxiliary indicator. Any indicator other than the master weight totalizer that indicates the weight of material determined 

by the scale.[2.21]

axle-load scale. A scale permanently installed in a fixed location, having a load-receiving element specially adapted to 

determine the combined load of all wheels (1) on a single axle or (2) on a tandem axle of a highway vehicle.[2.20]

B

badge. A metal plate affixed to the meter by the manufacturer showing the manufacturer's name, serial number and 

model number of the meter, and its rated capacity.[3.33]

balance, zero-load. See "zero-load balance."[2.20]

balance indicator. A combination of elements, one or both of which will oscillate with respect to the other, for 

indicating the balance condition of a nonautomatic indicating scale. The combination may consist of two indicating 

edges, lines, or points, or a single edge, line, or point and a graduated scale.[2.20]

balancing mechanism. A mechanism (including a balance ball) that is designed for adjusting a scale to an accurate 

zero-load balance condition.[2.20]

base pressure. The absolute pressure used in defining the gas measurement unit to be used, and is the gauge pressure at 

the meter plus an agreed atmospheric pressure.[3.33]

basic time rate. The charge for time for all intervals except the initial interval.[5.54]

basic tolerances. Basic tolerances are those tolerances on underregistration and on overregistration, or in excess and in 

deficiency, that are established by a particular code for a particular device under all normal tests, whether maintenance or 

acceptance. Basic tolerances include minimum tolerance values when these are specified. Special tolerances, identified 

as such and pertaining to special tests, are not basic tolerances.[1.10]

basic distance rate. The charge for distance for all intervals except the initial interval.[5.54]

batching meter. A device used for the purpose of measuring quantities of water to be used in a batching operation.[3.36]

beam scale. One on which the weights of loads of various magnitudes are indicated solely by means of one or more 

weighbeam bars either alone or in combination with counterpoise weights.[2.20]

beam. See "weighbeam."[2.20]

bell prover. A calibrated cylindrical metal tank of the annular type with a scale thereon that, in the downward travel in a 

surrounding tank containing a sealing medium, displaces air through the meter being proved or calibrated.[3.33]

belt-conveyor. An endless moving belt for transporting material from place to place.[2.21]

belt-conveyor scale. A device that employs a weighing element in contact with a belt to sense the weight of the material 

being conveyed and the speed (travel) of the material, and integrates these values to produce total delivered weight.[2.21]

belt-conveyor scale systems area. The scale area refers to the scale suspension, weigh idlers attached to the scale 

suspension, 5 approach (-) idlers, and 5 retreat (+) idlers.[2.21] (Added 2001)
Definitions

D-3

bench scale. See "counter scale."[2.20]

binary submultiples. Fractional parts obtained by successively dividing by the number 2. Thus, one-half, one-fourth, 

one-eighth, one-sixteenth, and so on, are binary submultiples.[1.10]

C

calibration parameter. Any adjustable parameter that can affect measurement or performance accuracy and, due to its 

nature, needs to be updated on an ongoing basis to maintain device accuracy, e.g., span adjustments, linearization factors, 

and coarse zero adjustments.[2.20, 2.21, 2.24, 3.30, 3.37, 5.56(a)] (Added 1993)

car-wash timer. A timer used in conjunction with a coin-operated device to measure the time during which car-wash 

water, cleaning solutions, or waxing solutions are dispensed.[5.55]

center-reading tank. One so designed that the gauge rod or surface gauge, when properly positioned for use, will be approximately in the vertical axis of the tank, centrally positioned with respect to the tank walls.[4.43]

cereal grain and oil seeds. Agricultural commodities including, but not limited to, corn, wheat, oats, barley, flax, rice, 

sorghum, soybeans, peanuts, dry beans, safflower, sunflower, fescue seed, etc.[5.56(a), 5.56(b)]

chart recorder. See analog or digital recorder. (Amended 1989) 

check rate. A rate of flow usually 20 percent of the capacity rate.[3.33]

checkweighing scale. One used to verify predetermined weight within prescribed limits.[2.24]

class of grain. Hard Red Winter Wheat as distinguished from Hard Red Spring Wheat as distinguished from Soft Red 

Winter Wheat, etc.[5.56(a), 5.56(b), 5.57]

clear interval between graduations. The distance between adjacent edges of successive graduations in a series of 

graduations. If the graduations are "staggered," the interval shall be measured, if necessary, between a graduation and an 

extension of the adjacent graduation. (Also see "minimum clear interval.")[1.10]

cleared. A taximeter is "cleared" when it is inoperative with respect to all fare indication, when no indication of fare or 

extras is shown and when all parts are in those positions in which they are designed to be when the vehicle on which the 

taximeter is installed is not engaged by a passenger.[5.54]

cold-tire pressure. The pressure in a tire at ambient temperature.[5.53, 5.54]

computing type or computing type device. A device designed to indicate, in addition to weight or measure, the total 

money value of product weighed or measured, for one of a series of unit prices.[1.10]

computing scale. One that indicates the money values of amounts of commodity weighed, at predetermined unit prices, 

throughout all or part of the weighing range of the scale.[2.20]

concave curve. A change in the angle of inclination of a belt conveyor where the center of the curve is above the 

conveyor.[2.21]

concentrated load capacity (CLC). A capacity rating of a vehicle, axle-load scale, or livestock scale specified by the 

manufacturer, defining the maximum load concentration for which the weighbridge is designed. In the case of vehicle and 

axle-load scales, it is the maximum axle-load concentration (for a group of two axles with a centerline spaced 4 feet apart 

and an axle width of 8 feet) for which the weighbridge is designed as specified by the manufacturer. The concentrated 

load capacity rating is for both test and use.[2.20]

(Added 1988)(Amended 1991 and 1994)

configuration parameter. Any adjustable or selectable parameter for a device feature that can affect the accuracy of a 

transaction or can significantly increase the potential for fraudulent use of the device and, due to its nature, needs to be 
Definitions

D-4

updated only during device installation or upon replacement of a component, e.g., division value (increment), sensor 

range, and units of measurement. [2.20, 2.21, 2.24, 3.30, 3.37, 5.56(a)] (Added 1993)

consecutive-car test train. A train consisting of cars weighed on a reference scale, then coupled consecutively and run 

over the coupled-in-motion railway track scale under test.[2.20]

(Added 1990)

construction materials hopper scale. A scale adapted to weighing construction materials such as sand, gravel, cement, 

and hot oil.[2.20]

contract sale. A sale where a written agreement exists, prior to the point of sale, in which both buyer and seller have 

accepted pricing conditions of the sale. Examples include, but are not limited to: e-commerce, club sales, or prepurchase agreements. Any devices used in the determination of quantity must comply with NIST Handbook 44.[3.30, 

3.321, 3.37] 

(Added 1993)(Amended 2002)

conventional scale. If the use of conversion tables is necessary to obtain a moisture content value, the moisture meter 

indicating scale is called "conventional scale." The values indicated by the scale are dimensionless.[5.56(b)]

conversion table. Any table, graph, slide rule, or other external device used to determine the moisture content from the 

value indicated by the moisture meter.[5.56(b)]

correction table. Any table, graph, slide rule, or other external device used to determine the moisture content from the 

value indicated by the moisture meter when the indicated value is altered by a parameter not automatically corrected for 

in the moisture meter (for example, temperature or test weight).[5.56(b)]

convex curve. A change in the angle of inclination of a belt conveyor where the center of the curve is below the 

conveyor.[2.21]

conveyor stringers. Support members for the conveyor on which the scale and idlers are mounted.[2.21]

correct. A piece of equipment is "correct" when, in addition to being accurate, it meets all applicable specification

requirements. Equipment that fails to meet any of the requirements for correct equipment is "incorrect." (Also see "accurate.")[1.10]

counter scale. One that, by reason of its size, arrangement of parts, and moderate nominal capacity, is adapted for use on 

a counter or bench. Sometimes called "bench scale."[2.20]

counterbalance weight(s). One intended for application near the butt of a weighbeam for zero-load balancing 

purposes.[2.20]

counterpoise weight(s). A slotted or "hanger" weight intended for application near the tip of the weighbeam of a scale 

having a multiple greater than 1.[2.20]

coupled-in-motion railroad weighing system. A device and related installation characteristics consisting of (1) the 

associated approach trackage, (2) the scale (i.e., the weighing element, the load-receiving element, and the indicating 

element with its software), and (3) the exit trackage which permit the weighing of railroad cars coupled in motion.[2.20, 

2.23]

(Added 1992)

crane scale. One with a nominal capacity of 5000 pounds or more designed to weigh loads while they are suspended 

freely from an overhead, trackmounted crane.[2.20]

cryogenic liquid-measuring device. A system including a mechanism or machine of (a) the meter or mass flow type, or 

(b) a weighing type of device mounted on a vehicle, designed to measure and deliver cryogenic liquids in the liquid state. 

Means may be provided to indicate automatically, for one of a series of unit prices, the total money value of the liquid 

measured.[3.34]

(Amended 1986)
Definitions

D-5

cryogenic liquids. Fluids whose normal boiling point is below 120 kelvin (-243 F).[3.34]

cubic foot, standard. That quantity of gas that occupies a volume of one cubic foot when under a pressure of 14.73 

lb/in2 absolute and at a temperature of 60 F.[3.33]

cubic foot, metered. That quantity of gas that occupies one cubic foot when under pressure and temperature conditions 

existing in the meter.[3.33]

cubic-foot bottle. A metal bottle open at the lower end and so supported that it may be easily raised or lowered in a tank 

that contains a sealing medium. With the level of the sealing medium properly adjusted, the bottle, when lowered, will 

displace exactly one cubic foot of air upon coming to rest on the bottom of the tank. The marks on the bottle defining the 

cubic foot are the bottom of the lower neck and the gauge mark that partially surrounds the gauge glass in the upper 

neck.[3.33]

cubic foot, gas. The amount of a cryogenic liquid in the gaseous state at a temperature of 70 F and under a pressure of 

14.696 lb/in2 absolute that occupies one cubic foot. (See NTP.)[3.34]

D

d, value scale division. See "scale division, value of (d)." [2.20, 2.22]

dairy-product-test scale. A scale used in determining the moisture content of butter and/or cheese or in determining the 

butterfat content of milk, cream, or butter.[2.20]

decreasing-load test. A test for automatic-indicating scales only, wherein the performance of the scale is tested as the 

load is reduced.[2.20, 2.22]

(Amended 1987)

deficiency. See "excess and deficiency."[1.10]

digital type. A system of indication or recording of the selector type or one that advances intermittently in which all 

values are presented digitally, or in numbers. In a digital indicating or recording element, or in digital representation, 

there are no graduations.[1.10]

direct sale. A sale in which both parties in the transaction are present when the quantity is being determined. An 

unattended automated or customer-operated weighing or measuring system is considered to represent the device/business 

owner in transactions involving an unattended device.[1.10] (Amended 1993)

discharge hose. A flexible hose connected to the discharge outlet of a measuring device or its discharge line.[3.30, 3.31, 

3.32, 3.34, 3.37, 3.38]

(Added 1987)

discharge line. A rigid pipe connected to the outlet of a measuring device.[3.30, 3.31, 3.32, 3.34, 3.37]

(Added 1987)

discrimination (of an automatic-indicating scale). The value of the test load on the load-receiving element of the scale 

that will produce a specified minimum change of the indicated or recorded value on the scale.[2.20, 2.22]

dispenser. See motor-fuel device.[3.30, 3.37]

distributed-car test train. A train consisting of cars weighed first on a reference scale, cars coupled consecutively in 

groups at different locations within the train, then run over the coupled-in-motion railway track scale under test. The 

groups are typically placed at the front, middle, and rear of the train.[2.20]

(Added 1990)
Definitions

D-6

dry-hose type. A type of device in which it is intended that the discharge hose be completely drained following the 

mechanical operations involved in each delivery. (See "dry hose.") [3.30, 3.31, 3.34, 3.35]

dry hose. A discharge hose intended to be completely drained at the end of each delivery of product. (See "dry-hose 

type.")[3.30, 3.31]

(Amended 2002)

dynamic monorail weighing system. A weighing system which employs hardware or software to compensate for 

dynamic effects from the load or the system that do not exist in static weighing, in order to provide a stable indication. 

Dynamic factors may include shock or impact loading, system vibrations, oscillations, etc. and can occur even when the 

load is not moving across the load receiving element.[2.20]

(Added 1999)

E

e, value of verification scale division. See "verification scale division, value of (e)." [2.20]

electronic link. An electronic connection between the weighing/load receiving or other sensing element and indicating 

element where one recognizes the other and neither can be replaced without calibration.[2.20]

(Added 2001)

element. A portion of a weighing or measuring device or system which performs a specific function and can be separated, 

evaluated separately, and is subject to specified full or partial error limits.

(Added 2002)

equal-arm scale. A scale having only a single lever with equal arms (that is, with a multiple of 1), equipped with two 

similar or dissimilar load-receiving elements (pan, plate, platter, scoop, or the like), one intended to receive material being 

weighed and the other intended to receive weights. There may or may not be a weighbeam.[2.20]

emin (minimum verification scale division). The smallest scale division for which a weighing element complies with the 

applicable requirements.[2.20, 2.21, 2.24] 

(Added 1997)

event counter. A nonresettable counter that increments once each time the mode that permits changes to sealable 

parameters is entered and one or more changes are made to sealable calibration or configuration parameters of a device. 

[2.20, 2.21, 3.30, 3.37, 5.54, 5.56(a), 5.56(b), 5.57] (Added 1993)

event logger. A form of audit trail containing a series of records where each record contains the number from the event 

counter corresponding to the change to a sealable parameter, the identification of the parameter that was changed, the 

time and date when the parameter was changed, and the new value of the parameter.[2.20, 2.21, 3.30, 3.37, 5.54, 5.56(a), 

5.56(b), 5.57]

(Added 1993)

excess and deficiency. When an instrument or device is of such a character that it has a value of its own that can be 

determined, its error is said to be "in excess" or "in deficiency," depending upon whether its actual value is, respectively, 

greater or less than its nominal value. (See "nominal.") Examples of instruments having errors "in excess" are: a linear 

measure that is too long; a liquid measure that is too large; and a weight that is "heavy." Examples of instruments having 

errors "in deficiency" are: a lubricating-oil bottle that is too small; a vehicle tank compartment that is too small; and a 

weight that is "light."[1.10]

extras. Charges to be paid by a passenger in addition to the fare, including any charge at a flat rate for the transportation 

of passengers in excess of a stated number and any charge for the transportation of baggage.[5.54]

F

face. That side of a taximeter on which passenger charges are indicated.[5.54]
Definitions

D-7

face. That portion of a computing-type pump or dispenser which displays the actual computation of price per unit, 

delivered quantity, and total sale price. In the case of some electronic displays, this may not be an integral part of the 

pump or dispenser.[3.30]

(Added 1987)

fare. That portion of the charge for the hire of a vehicle that is automatically calculated by a taximeter through the 

operation of the distance and/or time mechanism.[5.54]

farm milk tank. A unit for measuring milk or other fluid dairy product, comprising a combination of (1) a stationary or 

portable tank, whether or not equipped with means for cooling its contents, (2) means for reading the level of liquid in the 

tank, such as a removable gauge rod or a surface gauge, and (3) a chart for converting level-of-liquid readings to volume; 

or such a unit in which readings are made on gauge rod or surface gauge directly in terms of volume. Each compartment 

of a subdivided tank shall, for purposes of this code, be construed to be a "farm milk tank."[4.43]

feeding mechanism. The means for depositing material to be weighed on the belt conveyor.[2.21]

fifth wheel. A commercially-available distance-measuring device which, after calibration, is recommended for use as a 

field transfer standard for testing the accuracy of taximeters and odometers on rented vehicles.[5.53, 5.54]

fifth-wheel test. A distance test similar to a road test, except that the distance traveled by the vehicle under test is 

determined by a mechanism known as a "fifth-wheel" that is attached to the vehicle and that independently measures and 

indicates the distance.[5.53, 5.54]

flag. A plate at the end of the lever arm or similar part by which the operating condition of a taximeter is controlled and 

indicated.[5.54]

fractional bar. A weighbeam bar of relatively small capacity for obtaining indications intermediate between notches or 

graduations on a main or tare bar.[2.20]

ft3

/h. Cubic feet per hour.[3.33]

G

gasoline gallon equivalent (GGE). Gasoline gallon equivalent (GGE) means 5.660 pounds of natural gas.[3.37]

(Added 1994)

gasoline liter equivalent (GLE). Gasoline liter equivalent (GLE) means 0.678 kilograms of natural gas.[3.37]

(Added 1994)

gauge pressure. The difference between the pressure at the meter and the atmospheric pressure (psi).[3.33]

gauge rod. A graduated, "dip-stick" type of measuring rod designed to be partially immersed in the liquid and to be read 

at the point where the liquid surface crosses the rod.[4.42]

gauging. The process of determining and assigning volumetric values to specific graduations on the gauge or gauge rod 

that serve as the basis for the tank volume chart.[4.42]

graduated interval. The distance from the center of one graduation to the center of the next graduation in a series of 

graduations. (Also see "value of minimum graduated interval.")[1.10]

graduation. A defining line, or one of the lines defining the subdivisions of a graduated series. The term includes such 

special forms as raised or indented or scored reference "lines" and special characters such as dots. (Also see "main 

graduation" and "subordinate graduation.")[1.10]

grain hopper scale. One adapted to the weighing of individual loads of varying amounts of grain.[2.20]

grain moisture meter. Any device indicating either directly or through conversion tables and/or correction tables the 

moisture content of cereal grains and oil seeds. Also termed "moisture meter."[5.56(a), 5.56(b)]
Definitions

D-8

grain sample. That portion of grain or seed taken from a bulk of grain or seed to be bought or sold and used to determine 

the moisture content of the bulk.[5.56(a)., 5.56(b)]

grain-test scale. A scale adapted to weighing grain samples used in determining moisture content, dockage, weight per 

unit volume, etc.[2.20]

gravity discharge. A type of device designed for discharge by gravity.[3.30, 3.31]

H

head pulley. The pulley at the discharge end of the belt conveyor. The power drive to drive the belt is generally applied 

to the head pulley.[2.21]

hired. A taximeter is "hired" when it is operative with respect to all applicable indications of fare or extras. The 

indications of fare include time and distance where applicable unless qualified by another indication of "Time Not 

Recording" or an equivalent expression.[5.54]

hopper scale. A scale designed for weighing bulk commodities whose load-receiving element is a tank, box, or hopper 

mounted on a weighing element. (Also, see "automatic hopper scale," "grain hopper scale," and "construction materials 

hopper scale."[2.20]

I

idler space. The center-to-center distance between idler rollers measured parallel to the belt.[2.21]

idlers or idler rollers. Freely turning cylinders mounted on a frame to support the conveyor belt. For a flat belt, the 

idlers consist of one or more horizontal cylinders transverse to the direction of belt travel. For a troughed belt, the idlers 

consist of one or more horizontal cylinders and one or more cylinders at an angle to the horizontal to lift the sides of the 

belt to form a trough.[2.21]

in-service light indicator. A light used to indicate that a timing device is in operation.[5.55]

increasing-load test. The normal basic performance test for a scale in which observations are made as increments of test 

load are successively added to the load-receiving element of the scale.[2.20, 2.22]

increment. The value of the smallest change in value that can be indicated or recorded by a digital device in normal 

operation.[1.10]

index of an indicator. The particular portion of an indicator that is directly utilized in making a reading.[1.10]

indicating element. An element incorporated in a weighing or measuring device by means of which its performance 

relative to quantity or money value is "read" from the device itself as, for example, an index-and-graduated-scale 

combination, a weighbeam-and-poise combination, a digital indicator, and the like. (Also see "primary indicating or 

recording element.")[1.10]

indicator, balance. See "balance indicator."[2.20]

initial zero-setting mechanism. Automatic means provided to set the indication to zero at the time the instrument is 

switched on and before it is ready for use.[2.20]

(Added 1990)

initial distance or time interval. The interval corresponding to the initial money drop.[5.54]

interval, graduated. See "graduated interval."[1.10]

interval, clear, between graduations. See "clear interval between graduations."[1.10]
Definitions

D-9

J

jewelers' scale. One adapted to weighing gems and precious metals.[2.20]

K

kind of grain. Corn as distinguished from soybeans as distinguished from wheat, etc.[5.56(a), 5.56(b)]

L

label. A printed ticket, to be attached to a package, produced by a printer that is a part of a prepackaging scale or that is 

an auxiliary device.[2.20]

large-delivery device. Devices used primarily for single deliveries greater than 200 gallons, 2000 pounds, 20 000 cubic 

feet, 2000 liters, or 2000 kilograms.[3.34]

laundry-drier timer. A timer used in conjunction with a coin-operated device to measure the period of time that a 

laundry drier is in operation.[5.55]

liquefied petroleum gas vapor-measuring device. A system including a mechanism or device of the meter type, 

equipped with a totalizing index, designed to measure and deliver liquefied petroleum gas in the vapor state by definite 

volumes, and generally installed in a permanent location. The meters are similar in construction and operation to the 

conventional natural- and manufactured-gas meters.[3.33]

liquefied petroleum gas. A petroleum product composed predominantly of any of the following hydrocarbons or 

mixtures thereof: propane, propylene, butanes (normal butane or isobutane), and butylenes.[3.31, 3.32, 3.33, 3.34, 3.37]

liquefied petroleum gas liquid-measuring device. A system including a mechanism or machine of the meter type 

designed to measure and deliver liquefied petroleum gas in the liquid state by a definite quantity, whether installed in a 

permanent location or mounted on a vehicle. Means may or may not be provided to indicate automatically, for one of a 

series of unit prices, the total money value of the liquid measured.[3.33]

(Amended 1987)

liquid volume correction factor. A correction factor used to adjust the liquid volume of a cryogenic product at the time 

of measurement to the liquid volume at NBP.[3.34]

liquid-fuel device. A device designed for the measurement and delivery of liquid fuels.[3.30]

liquid-measuring device. A mechanism or machine designed to measure and deliver liquid by definite volume. Means 

may or may not be provided to indicate automatically, for one of a series of unit prices, the total money value of the liquid 

measured, or to make deliveries corresponding to specific money values at a definite unit price.[3.30]

liquid fuel. Any liquid used for fuel purposes, that is, as a fuel, including motor fuel.[3.30, 3.31]

livestock scale. A scale equipped with stock racks and gates and adapted to weighing livestock standing on the scale 

platform.[2.20]

(Amended 1989)

load-receiving element. That element of a scale that is designed to receive the load to be weighed; for example, 

platform, deck, rail, hopper, platter, plate, scoop.[2.20, 2.21, 2.23]

load cell. A device, whether electric, hydraulic, or pneumatic, that produces a signal proportional to the load 

applied.[2.20, 2.21, 2.23]

load cell verification interval (v). The load cell interval, expressed in units of mass, used in the test of the load cell for 

accuracy classification.[2.20, 2.21] (Added 1996)
Definitions

D-10

loading point. The location at which material to be conveyed is applied to the conveyor.[2.21]

low-flame test. A test simulating extremely low-flow rates such as caused by pilot lights.[3.33]

lubricant device. A device designed for the measurement and delivery of liquid lubricants, including, but not limited to, 

heavy gear lubricants and automatic transmission fluids (automotive).[3.30]

M

m3

/h. Cubic meters per hour.[3.33]

main-weighbeam elements. The combination of a main bar and its fractional bar, or a main bar alone if no fractional bar 

is associated with it.[2.20]

main bar. A principal weighbeam bar, usually of relatively large capacity as compared with other bars of the same 

weighbeam. (On an automatic-indicating scale equipped with a weighbeam, the main weighbeam bar is frequently called 

the "capacity bar.")[2.20]

main graduation. A graduation defining the primary or principal subdivisions of a graduated series. (Also see 

"graduation.")[1.10]

manual zero-setting mechanism. Nonautomatic means provided to attain a zero balance indication by the direct 

operation of a control.[2.20]

manufactured device. Any commercial weighing or measuring device shipped as new from the original equipment 

manufacturer.[1.10]

(Amended 2001)

mass flow meter. A device that measures the mass of a product flowing through the system. The mass measurement 

may be determined directly from the effects of mass on the sensing unit or may be inferred by measuring the properties of 

the product, such as the volume, density, temperature, or pressure, and displaying the quantity in mass units.[3.37]

master meter test method. A method of testing milk tanks that utilizes an approved master meter system for measuring 

test liquid removed from or introduced into the tank.[4.42]

master weight totalizer. An indicating element used with a belt-conveyor scale to indicate the weight of material that 

was passed over the scale. The master weight totalizer is a primary indicating element of the belt-conveyor scale.[2.21]

material test. The test of a belt-conveyor scale using material (preferably that for which the device is normally used) 

that has been weighed to an accuracy of 0.1 percent.[2.21]

(Amended 1989)

maximum capacity. The largest load that may be accurately weighed.[2.20, 2.24]

(Added 1999)

maximum cargo load. The maximum cargo load for trucks is the difference between the manufacturer's rated gross 

vehicle weight and the actual weight of the vehicle having no cargo load.[5.53]

meter register. An observation index for the cumulative reading of the gas flow through the meter. In addition there are 

one or two proving circles in which one revolution of the test hand represents 1/2, 1, 2, 5, or 10 cubic feet, or 0.025, 0.05, 

0.1, 0.2, or 0.25 cubic meter, depending on meter size. If two proving circles are present, the circle representing the 

smallest volume per revolution is referred to as the "leak-test circle."[3.33]

metrological integrity (of a device). The design, features, operation, installation, or use of a device that facilitates (1) 

the accuracy and validity of a measurement or transaction, (2) compliance of the device with weights and measures 

requirements, or (3) the suitability of the device for a given application. [1.10, 2.20] (Added 1993)
Definitions

D-11

minimum capacity. The smallest load that may be accurately weighed. The weighing results may be subject to 

excessive error if used below this value.[2.20, 2.24]

(Added 1999)

minimum clear interval. The shortest distance between adjacent graduations when the graduations are not parallel. 

(Also see "clear interval.")[3.30, 3.31, 3.32, 3.33, 3.34, 3.35, 3.36, 3.38, 5.50, 5.51, 5.56(b)]

minimum delivery. The least amount of weight that is to be delivered as a single weighment by a belt-conveyor scale 

system in normal use.[2.21]

minimum tolerance. Minimum tolerances are the smallest tolerance values that can be applied to a scale. Minimum 

tolerances are determined on the basis of the value of the minimum graduated interval or the nominal or reading face 

capacity of the scale. (See also definition for basic tolerances.)[2.20, 2.22, 2.24]

minimum totalized load. The least amount of weight for which the scale is considered to be performing 

accurately.[2.21]

moisture content (wet basis). The mass of water in a grain or seed sample (determined by the reference method) divided 

by the mass of the grain or seed sample expressed as a percentage (%).[5.56(a), 5.56(b)]

money-operated type. A device designed to be released for service by the insertion of money, or to be actuated by the 

insertion of money to make deliveries of product.[1.10]

money drop. An increment of fare indication. The "initial money drop" is the first increment of fare indication 

following activation of the taximeter.[5.54]

motor-fuel device or motor-fuel dispenser or retail motor-fuel device. A device designed for the measurement and 

delivery of liquids used as fuel for internal-combustion engines. The term "motor-fuel dispenser" means the same as 

"motor-fuel device"; the term "retail motor-fuel device" applies to a unique category of device (see definition of "retail 

device").[3.30, 3.32, 3.37]

motor fuel. Liquid used as fuel for internal-combustion engines.[3.30]

multi-interval scale. A scale having one weighing range which is divided into partial weighing ranges, each with 

different scale intervals, with the weighing range determined automatically according to the load applied, both on 

increasing and decreasing loads.

(Added 1995) [2.20]

multi-revolution scale. An automatic-indicating scale having a nominal capacity that is a multiple of the reading-face 

capacity and that is achieved by more than one complete revolution of the indicator.[2.20]

multiple cell application load cell. A load cell intended for use in a weighing system which incorporates more than one 

load cell. A multiple cell application load cell is designated with the letter "M" or the term "Multiple." (See also “single 

cell application load cell”) [2.20]

(Added 1999)

multiple of a scale. In general, the multiplying power of the entire system of levers or other basic weighing elements. 

(On a beam scale, the multiple of the scale is the number of pounds on the load-receiving element that will be counterpoised by 1 pound applied to the tip pivot of the weighbeam.)[2.20]

multiple range scale. A scale having two or more weighing ranges with different maximum capacities and different 

scale intervals for the same load receptor, each range extending from zero to its maximum capacity.[2.20]

(Added 1995)

multiple-tariff taximeter. One that may be set to calculate fares at any one of two or more rates.[5.54]

multiple. An integral multiple; that is, a result obtained by multiplying by a whole number. (Also see "multiple of a 

scale.")[1.10]
Definitions

D-12

N

natural gas. A gaseous fuel, composed primarily of methane, that is suitable for compression and dispensing into a fuel 

storage container(s) for use as an engine fuel.[3.37]

(Added 1994)

NBP. Normal boiling point of a cryogenic liquid at 14.696 lb/in2 absolute.[3.34]

nmax (maximum number of scale divisions). The maximum number of scale divisions for which a main element or load 

cell complies with the applicable requirements. The maximum number of scale divisions permitted for an installation is 

limited to the lowest nmax marked on the scale indicating element, weighing element, or load cell.[2.20, 2.21, 2.24]

(Added 1997)

no-load reference value. A positive weight value indication with no load in the load-receiving element (hopper) of the 

scale. (Used with automatic bulk-weighing systems and certain single-draft, manually-operated receiving hopper scales 

installed below grade and used to receive grain.)[2.20]

nominal capacity. The nominal capacity of a scale is (a) the largest weight indication that can be obtained by the use of 

all of the reading or recording elements in combination, including the amount represented by any removable weights 

furnished or ordinarily furnished with the scale, but excluding the amount represented by any extra removable weights not 

ordinarily furnished with the scale, and excluding also the capacity of any auxiliary weighing attachment not 

contemplated by the original design of the scale, and excluding any fractional bar with a capacity less than 2-1/2 percent 

of the sum of the capacities of the remaining reading elements, or (b) the capacity marked on the scale by the 

manufacturer, whichever is less. (Also see "nominal capacity, batching scale"; "nominal capacity, hopper scale.")[2.20]

nominal capacity, batching scale. The nominal capacity of a batching scale is the capacity as marked on the scale by the 

scale manufacturer, or the sum of the products of the volume of each of the individual hoppers, in terms of cubic feet, 

times the weight per cubic foot of the heaviest material weighed in each hopper, whichever is less.[2.20]

nominal capacity, hopper scale. The nominal capacity of a hopper scale is the capacity as marked on the scale by the 

scale manufacturer, or the product of the volume of the hopper in bushels or cubic feet times the maximum weight per 

bushel or cubic foot, as the case may be, of the commodity normally weighed, whichever is less.[2.20]

nominal. Refers to "intended" or "named" or "stated," as opposed to "actual." For example, the "nominal" value of 

something is the value that it is supposed or intended to have, the value that it is claimed or stated to have, or the value by 

which it is commonly known. Thus, "1-pound weight," "1-gallon measure," "1-yard indication," and "500-pound scale" 

are statements of nominal values; corresponding actual values may be greater or lesser. (See nominal capacity of a 

scale)[1.10]

nonretroactive. "Nonretroactive" requirements are enforceable after the effective date for:

1. devices manufactured within a State after the effective date;

2. both new and used devices brought into a State after the effective date; and

3. devices used in noncommercial applications which are placed into commercial use after the effective date.

Nonretroactive requirements are not enforceable with respect to devices that are in commercial service in the State as of 

the effective date or to new equipment in the stock of a manufacturer or a dealer in the State as of the effective date.

(Nonretroactive requirements are printed in italic type.)[1.10]

(Amended 1989)

nose-iron. A slide-mounted, manually-adjustable pivot assembly for changing the multiple of a lever.[2.20]

notes. A section included in each of a number of codes, containing instructions, pertinent directives, and other specific 

information pertaining to the testing of devices. Notes are primarily directed to weights and measures officials.[1.10]
Definitions

D-13

NTP density and volume correction factor. A correction factor used to adjust the liquid volume of a cryogenic product 

at the time of measurement to the gas equivalent at NTP.[3.34]

NTP. Normal temperature of 21 C (70 F) and pressure of 101.325 kPa (14.696 lb/in2 absolute) respectively.[3.34]

O

odometer. A device that automatically indicates the total distance traveled by a vehicle. For the purpose of this code, 

this definition includes hub odometers, cable-driven odometers, and the distance-indicating or odometer portions of 

"speedometer" assemblies for automotive vehicles.[5.53]

official grain samples. Grain or seed used by the official as the official transfer standard from the reference standard 

method to test the accuracy and precision of grain moisture meters.[5.56(a), 5.56(b)]

official with statutory authority. The representative of the jurisdiction(s) responsible for certifying the accuracy of the 

device.[2.20, 2.21, 2.22]

(Added 1991)

operating tire pressure. The pressure in a tire immediately after a vehicle has been driven for at least 5 miles or 

8 kilometers.[5.53, 5.54]

over-and-under indicator. An automatic-indicating element incorporated in or attached to a scale and comprising an 

indicator and a graduated scale with a central or intermediate "zero" graduation and a limited range of weight graduations 

on either side of the zero graduation, for indicating weights greater than and less than the predetermined values for which 

other elements of the scale may be set. (A scale having an over-and-under indicator is classed as an automatic-indicating 

scale.)[2.20]

overregistration and underregistration. When an instrument or device is of such a character that it indicates or records 

values as a result of its operation, its error is said to be in the direction of overregistration or underregistration, depending 

upon whether the indications are, respectively, greater or less than they should be. Examples of devices having errors of 

"overregistration" are: a fabric-measuring device that indicates more than the true length of material passed through it; 

and a liquid-measuring device that indicates more than the true amount of the liquid delivered by the device. Examples of 

devices having errors of "underregistration" are: a meter that indicates less than the true amount of product that it 

delivers; and a weighing scale that indicates or records less than the true weight of the applied load.[1.10]

P

parallax. The apparent displacement, or apparent difference in height or width, of a graduation or other object with 

respect to a fixed reference, as viewed from different points.[1.10]

parking meter. A coin-operated device for measuring parking time for vehicles.[5.55]

passenger vehicles. Vehicles such as automobiles, recreational vehicles, limousines, ambulances, and hearses.[5.53]

performance requirements. Performance requirements include all tolerance requirements and, in the case of 

nonautomatic-indicating scales, sensitivity requirements (SR). (See definitions for "tolerance" and "sensitivity 

requirement.")[1.10]

point-of-sale system. An assembly of elements including a weighing or measuring element, an indicating element, and a 

recording element (and may also be equipped with a “scanner”) used to complete a direct sales transaction.[2.20, 3.30, 

3.32, 3.37]

(Added 1986) (Amended 1997)

poise. A movable weight mounted upon or suspended from a weighbeam bar and used in combination with graduations, 

and frequently with notches, on the bar to indicate weight values. (A suspended poise is commonly called a "hanging 

poise.")[2.20]
Definitions

D-14

postal scale. A scale (usually a computing scale) designed for use to determine shipping weight or delivery charges for 

letters or parcels delivered by the U.S. Postal Service or private shipping companies. A weight classifier may be used as a 

postal scale.[2.20] (Added 1987)

prepackaging scale. A computing scale specially designed for putting up packages of random weights in advance of 

sale.[2.20]

prescription scale. A scale or balance adapted to weighing the ingredients of medicinal and other formulas prescribed by 

physicians and others and used or intended to be used in the ordinary trade of pharmacists.[2.20]

pressure type (device). A type of device designed for operation with the liquid under artificially produced 

pressure.[3.30, 3.31]

primary indicating or recording elements. The term "primary" is applied to those principal indicating (visual) elements 

and recording elements that are designed to, or may, be used by the operator in the normal commercial use of a device. 

The term "primary" is applied to any element or elements that may be the determining factor in arriving at the sale 

representation when the device is used commercially. (Examples of primary elements are the visual indicators for meters 

or scales not equipped with ticket printers or other recording elements and both the visual indicators and the ticket printers 

or other recording elements for meters or scales so equipped.) The term "primary" is not applied to such auxiliary 

elements as, for example, the totalizing register or predetermined-stop mechanism on a meter or the means for producing 

a running record of successive weighing operations, these elements being supplementary to those that are the determining 

factors in sales representations of individual deliveries or weights. (See "indicating element" and "recording 

element.")[1.10]

prover oil. A light oil of low vapor pressure used as a sealing medium in bell provers, cubic-foot bottles, and portable 

cubic-foot standards.[3.33]

proving indicator. The test hand or pointer of the proving or leak-test circle on the meter register or index.[3.33]

prover method. A method of testing milk tanks that utilizes approved volumetric prover(s) for measuring the test liquid 

removed from or introduced into the tank.[4.42]

R

“r” factor. A computation for determining the suitability of a vehicle scale for weighing vehicles with varying axle 

configurations. The factor was derived by dividing the weights in FHWA Federal Highway Bridge Gross Weight 

Table B by 34 000 lbs. (The resultant factors contained in Table UR.3.2.1.)[2.20]

radio frequency interference (RFI). Radio frequency interference is a type of electrical disturbance that, when 

introduced into electronic and electrical circuits, may cause deviations from the normally expected performance.[1.10]

ranges, weight. See "weight ranges."[2.20]

rated scale capacity. That value representing the weight that can be delivered by the device in one hour.[2.21]

rated capacity. The rate of flow in cubic meters per hour of a hydrocarbon gas vapor-measuring device as recommended 

by the manufacturer. This rate of flow should cause a pressure drop across the meter not exceeding 1/2-inch water 

column.[3.33]

ratio test. A test to determine the accuracy with which the actual multiple of a scale agrees with its designed multiple.

This test is used for scales employing counterpoise weights and is made with standard test weights substituted in all cases 

for the weights commercially used on the scale. (It is appropriate to use this test for some scales not employing 

counterpoise weights.)[2.20]

reading-face capacity. The largest value that may be indicated on the reading face, exclusive of the application or 

addition of any supplemental or accessory elements.[1.10]
Definitions

D-15

reading face. That portion of an automatic-indicating weighing or measuring device that gives a visible indication of the 

quantity weighed or measured. A reading face may include an indicator and a series of graduations or may present values 

digitally, and may also provide money-value indications.[1.10]

recorded representation. The printed, embossed, or other representation that is recorded as a quantity by a weighing or 

measuring device.[1.10]

recording element. An element incorporated in a weighing or measuring device by means of which its performance 

relative to quantity or money value is permanently recorded on a tape, ticket, card, or the like, in the form of a printed, 

stamped, punched, or perforated representation.[1.10, 2.21]

recording scale. One on which the weights of applied loads may be permanently recorded on a tape, ticket, card, or the 

like in the form of a printed, stamped, punched, or perforated representation.[2.20]

reference weight car. A railroad car weighed on a scale for temporary use as a mass standard over a short period of time 

(typically, the time required to test one scale) as part of a test train.

Note: A test weight car that is representative of the types of cars typically weighed on the scale under test may 

be used wherever reference weight cars are specified.[2.20]

(Added 1991)

remanufactured device. A device that is disassembled, checked for wear, parts replaced or fixed, reassembled and made 

to operate like a new device of the same type.[1.10]

(Added 2001)

remanufactured element. An element that is disassembled, checked for wear, parts replaced or fixed, reassembled and 

made to operate like a new element of the same type.[1.10]

(Added 2001) 

repaired device. A device to which work is performed that brings the device back into proper operating condition.[1.10]

(Added 2001)

repaired element. An element to which work is performed that brings the element back into proper operating condition. 

[1.10] 

(Added 2001) 

remote configuration capability. The ability to adjust a weighing or measuring device or change its sealable 

parameters from or through some other device that is not itself necessary to the operation of the weighing or measuring 

device or is not a permanent part of that device. [2.20, 2.21, 2.24, 3.30, 3.37, 5.56(a)]

(Added 1993)

retail device. A device used for:

single deliveries of less than 378 L (100 gal),

retail deliveries of motor fuels to individual highway vehicles, or

single deliveries of liquefied petroleum gas for domestic use and liquified petroleum gas or liquid anhydrous 

ammonia for nonresale use.

(Amended 1987) [3.32]

retroactive. "Retroactive" requirements are enforceable with respect to all equipment. Retroactive requirements are 

printed herein in upright roman type. (Also see "nonretroactive.")[1.10]

road test. A distance test, over a measured course, of a complete taximeter assembly when installed on a vehicle, the 

mechanism being actuated as a result of vehicle travel.[5.53, 5.54]
Definitions

D-16

rolling circumference. The rolling circumference is the straight line distance traveled per revolution of the wheel (or 

wheels) that actuates the taximeter or odometer. If more than one wheel actuates the taximeter or odometer, the rolling 

circumference is the average distance traveled per revolution of the actuating wheels.[5.53, 5.54]

S

scale area, belt-conveyor. See belt-conveyor scale systems area.[2.21]

(Added 2001)

scale division, number of (n). Quotient of the capacity divided by the value of the verification scale division.[2.20]

e

Capacity n = 

scale division, value of (d). The value of the scale division, expressed in units of mass, is the smallest subdivision of the 

scale for analog indication or the difference between two consecutively indicated or printed values for digital indication or 

printing. (Also see "verification scale division.")[2.20, 2.22]

scale section. A part of a vehicle, axle-load, livestock, or railway track scale consisting of two main load supports, 

usually transverse to the direction in which the load is applied.[2.20]

scale. See specific type of scale.[2.20]

seal. See "approval seal," "security seal."[1.10]

section capacity. The section capacity of a scale is the maximum live load that may be divided equally on the load pivots 

or load cells of a section.[2.20]

(Added 2001)

section test. A shift test in which the test load is applied over individual sections of the scale. This test is conducted to 

disclose the weighing performance of individual sections, since scale capacity test loads are not always available and 

loads weighed are not always distributed evenly over all main load supports.[2.20]

 

security means. A method used to prevent access by other than qualified personnel, or to indicate that access has been 

made to certain parts of a scale that affect the performance of the device.[2.21]

security seal. A uniquely identifiable physical seal, such as a lead-and-wire seal or other type of locking seal, a 

pressure-sensitive seal sufficiently permanent to reveal its removal, or similar apparatus attached to a weighing or 

measuring device for protection against or indication of access to adjustment. (Also see "approval seal.")[1.10]

(Amended 1994)

selector-type. A system of indication or recording in which the mechanism selects, by means of a ratchet-and-pawl 

combination or by other means, one or the other of any two successive values that can be indicated or recorded.[1.10]

semi-automatic zero-setting mechanism. Automatic means provided to attain a direct zero balance indication requiring 

a single initiation by an operator.[2.20]

sensitivity requirement (SR). A performance requirement for a non automatic-indicating scale; specifically, the 

minimum change in the position of rest of the indicating element or elements of the scale in response to the increase or 

decrease, by a specified amount, of the test load on the load-receiving element of the scale.[2.20]

sensitivity (of a nonautomatic-indicating scale). The value of the test load on the load-receiving element of the scale 

that will produce a specified minimum change in the position of rest of the indicating element or elements of the 

scale.[2.20]

shift test. A test intended to disclose the weighing performance of a scale under off-center loading.[2.20]

side. That portion of a pump or dispenser which faces the consumer during the normal delivery of product.[3.30]
Definitions

D-17

(Added 1987)

simulated-road test. A distance test during which the taximeter or odometer may be actuated by some means other than 

road travel. The distance traveled is either measured by a properly calibrated roller device or computed from rolling 

circumference and wheel-turn data.[5.53, 5.54]

simulated test. A test using artificial means of loading the scale to determine the performance of a belt-conveyor 

scale.[2.21]

single cell application load cell. A load cell intended for use in a weighing system which incorporates one or more load 

cells. A single cell application load cell is designated with the letter "S" or the term "Single." (See also “multiple cell 

application load cell”) [2.20]

(Added 1999)

single-tariff taximeter. One that calculates fares at a single rate only.[5.54]

skirting. Stationary side boards or sections of belt conveyor attached to the conveyor support frame or other stationary 

support to prevent the bulk material from falling off the side of the belt.[2.21]

slow-flow meter. A retail device designed for the measurement, at very slow rates (less than 40 L (10 gal) per hour), of 

liquid fuels at individual domestic installations.[3.30]

small-delivery device. Any device other than a large-delivery device.[3.34]

span (structural). The distance between adjoining sections of a scale.[2.20]

(Added 1988)

specification. A requirement usually dealing with the design, construction, or marking of a weighing or measuring 

device. Specifications are directed primarily to the manufacturers of devices.[1.10]

static monorail weighing system. A weighing system in which the load being applied is stationary during the weighing 

operation.[2.20]

(Added 1999)

strain-load test. The test of a scale beginning with the scale under load and applying known test weights to determine 

accuracy over a portion of the weighing range. The scale errors for a strain-load test are the errors observed for the 

known test loads only. The tolerances to be applied are based on the known test load used for each error that is 

determined.[2.20, 2.22]

subordinate graduation. Any graduation other than a main graduation. (Also see "graduation.")[1.10]

subsequent distance or time intervals. The intervals corresponding to money drops following the initial money 

drop.[5.54]

surface gauge. A combination of (1) a stationary indicator, and (2) a movable, graduated element designed to be brought 

into contact with the surface of the liquid from above.[4.42]

T

tail pulley. The pulley at the opposite end of the conveyor from the head pulley.[2.21]

take-up. A device to provide sufficient tension in a conveyor belt so that the belt will be positively driven by the drive 

pulley. A counter-weighted take-up consists of a pulley free to move in either the vertical or horizontal direction with 

dead weights applied to the pulley shaft to provide the tension required.[2.21]

tare-weighbeam elements. The combination of a tare bar and its fractional bar, or a tare bar alone if no fractional bar is 

associated with it.[2.20]
Definitions

D-18

tare mechanism. A mechanism (including a tare bar) designed for determining or balancing out the weight of packaging 

material, containers, vehicles, or other materials that are not intended to be included in netweight determinations.[2.20]

taximeter. A device that automatically calculates, at a predetermined rate or rates, and indicates the charge for hire of a 

vehicle.[5.54]

testing. An operation consisting of a series of volumetric determinations made to verify the accuracy of the volume chart 

that was developed by gauging.[4.42]

test liquid. The liquid used during the test of a device.[3.30, 3.31, 3.34, 3.35, 3.36, 3.37, 3.38]

test chain. A device used for simulated tests consisting of a series of rollers or wheels linked together in such a manner 

as to assure uniformity of weight and freedom of motion to reduce wear, with consequent loss of weight, to a 

minimum.[2.21]

test train. A train consisting of or including reference weight cars and used to test coupled-in-motion railway track 

scales. The reference weight cars may be placed consecutively or distributed in different places within a train.[2.20]

(Added 1990)(Amended 1991)

test weight car. A railroad car designed to be a stable mass standard to test railway track scales. The test weight car may 

be one of the following types: a self-contained composite car, a self-propelled car, or a standard rail car.[2.20]

(Added 1991)

time recorder. A clock-operated mechanism designed to record the time of day. Examples of time recorders are those 

used in parking garages to record the "in" and "out" time of day for parked vehicles.[5.55]

timing device. A device used to measure the time during which a particular paid-for service is dispensed. Examples of 

timing devices are laundry driers, car-wash timers, parking meters, and parking-garage clocks and recorders.[5.55]

tolerance. A value fixing the limit of allowable error or departure from true performance or value. (See also "basic 

tolerances.")[1.10]

training idlers. Idlers of special design or mounting intended to shift the belt sideways on the conveyor to assure the belt 

is centered on the conveying idlers.[2.21]

transfer standard. A measurement system designed for use in proving and testing cryogenic liquid-measuring devices.-

[3.34]

tripper. A device for unloading a belt conveyor at a point between the loading point and the head pulley.[2.21]

U

uncoupled-in-motion railroad weighing system. A device and related installation characteristics consisting of (1) the 

associated approach trackage, (2) the scale (i.e., the weighing element, the load-receiving element, and the indicating 

element with its software), and (3) the exit trackage which permit the weighing of railroad cars uncoupled in 

motion.[2.20] (Added 1993)

underregistration. See "overregistration" and "underregistration."[1.10]

unit price. The price at which the product is being sold and expressed in whole units of measurement.[1.10, 3.30]

(Added 1992)

unit weight. One contained within the housing of an automatic-indicating scale and mechanically applied to and 

removed from the mechanism. The application of a unit weight will increase the range of automatic indication, normally 

in increments equal to the reading-face capacity.[2.20]
Definitions

D-19

unit train. A unit train is defined as a number of contiguous cars carrying a single commodity from one consignor to one 

consignee. The number of cars is determined by agreement among the consignor, consignee, and the operating 

railroad.[2.20]

user requirement. A requirement dealing with the selection, installation, use, or maintenance of a weighing or 

measuring device. User requirements are directed primarily to the users of devices.[1.10]

usual and customary. Commonly or ordinarily found in practice or in the normal course of events and in accordance 

with established practices.[1.10]

V

value of minimum graduated interval. The value represented by the interval from the center of one graduation to the 

center of the succeeding graduation. Also, the increment between successive recorded values. (Also see "graduated 

interval.")[1.10]

vehicle on-board weighing system. A weighing system designed as an integral part of or attached to the frame, chassis, 

lifting mechanism, or bed of a vehicle, trailer, industrial truck, industrial tractor, or forklift truck.[2.20] (Amended 1993)

vehicle scale. A scale adapted to weighing highway, farm, or other large industrial vehicles (except railroad freight cars), 

loaded or unloaded.[2.20]

verification scale division, value of (e). A value, expressed in units of weight (mass) and specified by the manufacturer 

of a device, by which the tolerance values and the accuracy class applicable to the device are determined. The verification scale division is applied to all scales, in particular to ungraduated devices since they have no graduations. The 

verification scale division, e, may be different from the displayed scale division, d, for certain other devices used for 

weight classifying or weighing in pre-determined amounts, and certain other Class I and II scales.[2.20]

visible type. A type of device in which the measurement takes place in a see-through glass measuring chamber.[3.30]

vmin (minimum load cell verification interval). The smallest load cell verification interval, expressed in units of mass*

into which the load cell measuring range can be divided.[2.20, 2.24]

[*Nonretroactive as of January 1, 2001]

(Added 1996) (Amended 1999)

W

weighbeam. An element comprising one or more bars, equipped with movable poises or means for applying 

counterpoise weights or both.[2.20]

weighing element. That portion of a scale that supports the load-receiving element and transmits to the indicating 

element a signal or force resulting from the load applied to the load-receiving element.[2.20, 2.21, 2.22]

(Added 1988)

weighment. A single complete weighing operation.[2.20, 2.21]

(Added 1986)

weight, unit. See "unit weight."[2.20]

weight classifier. A digital scale that rounds weight values up to the next scale division. These scales usually have a 

verification scale division, e, that is smaller than the displayed scale division.[2.20]

(Added 1987)

weight ranges. Electrical or electro-mechanical elements incorporated in an automatic indicating scale through the 

application of which the range of automatic indication of the scale is increased, normally in increments equal to the 

reading-face capacity.[2.20]
Definitions

D-20

wet basis. See "moisture content (wet basis)."[5.56(a), 5.56(b)]

wet hose. A discharge hose intended to be full of product at all times. (See "wet-hose type.")[3.30, 3.31, 3.38]

(Amended 2002)

wet-hose type. A type of device designed to be operated with the discharge hose full of product at all times. (See "wet 

hose.")[3.30, 3.32, 3.34, 3.37, 3.38]

(Amended 2002)

wheel-load weighers. Compact, self-contained, portable weighing elements specially adapted to determining the wheel 

loads or axle loads of vehicles on highways for the enforcement of highway weight laws only.[2.20]

wholesale device. Any device other than a retail device. (See "retail device.")[3.30, 3.32] 

wing pulley. A pulley made of widely spaced metal bars in order to set up a vibration to shake loose material off the 

underside (return side) of the belt.[2.21]

Z

zero-load balance. A correct weight indication or representation of zero when there is no load on the load-receiving 

element. (See also "zero-load balance for an automatic-indicating scale," "zero-load balance for a nonautomatic-indicating scale," "zero-load balance for a recording scale.")[2.20]

zero-load balance, automatic-indicating scale. A condition in which the indicator is at rest at, or oscillates through 

approximately equal arcs on either side of, the zero graduation.[2.20]

zero-load balance, nonautomatic-indicating scale. A condition in which (a) the weighbeam is at rest at, or oscillates 

through approximately equal arcs above and below, the center of a trig loop; (b) the weighbeam or lever system is at rest 

at, or oscillates through approximately equal arcs above and below, a horizontal position or a position midway between 

limiting stops; or (c) the indicator of a balance indicator is at rest at, or oscillates through approximately equal arcs on 

either side of, the zero graduation.[2.20]

zero-load balance for a recording scale. A condition in which the scale will record a representation of zero load.[2.20]

zero-load reference (belt-conveyor scales). A zero-load reference value represents no load on a moving conveyor belt. 

This value can be either; a number representing the electronic load cell output, a percentage of full scale capacity, or other 

reference value that accurately represents the no load condition of a moving conveyor belt. The no load reference value 

can only be updated after the completion of a zero load test.[2.21]

(Added 2002)

zero-setting mechanism. Means provided to attain a zero balance indication with no load on the load-receiving element.

Three types of these mechanisms are:[2.20]

 

manual zero-setting mechanism. Nonautomatic means provided to attain a zero balance indication by the direct 

operation of a control.[2.20]

semiautomatic zero-setting mechanism. Automatic means provided to attain a direct zero balance indication 

requiring a single initiation by an operator.[2.20]

automatic zero-setting mechanism. Automatic means provided to maintain zero balance indication without the 

intervention of an operator.[2.20]

zero-setting mechanism (belt-conveyor scale). A mechanism enabling zero totalization to be obtained over a whole 

number of belt revolutions [2.21, 2.23].

(Added 2002)

zone of uncertainty. The zone between adjacent increments on a digital device in which the value of either of the 

adjacent increments may be displayed.[2.20]