Handbook 44 – 2022 Section 2

2-1

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

Section 2

Table of Contents

Page

2.20. Scales............................................................................................................................... 2-3

2.21. Belt-Conveyor Scale Systems........................................................................................ 2-63

2.22. Automatic Bulk Weighing Systems............................................................................... 2-81

2.23. Weights.......................................................................................................................... 2-91

2.24. Automatic Weighing Systems........................................................................................ 2-99

2.25. Weigh-In-Motion Systems Used for Vehicle Enforcement Screening –

Tentative Code............................................................................................................. 2-117
2.20. Section 2 Handbook 44 – 2022

2-2

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

THIS PAGE INTENTIONALLY LEFT BLANK
Handbook 44 – 2022 2.20. Scales

2-3

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

Table of Contents

Page

Section 2.20. Scales................................................................................................................... 2-7

A. Application .....................................................................................................................................................2-7

A.1. General..................................................................................................................................................2-7

A.2. Wheel-Load Weighers, Portable Axle-Load Weighers, and Axle-Load Scales....................................2-7

A.3. Additional Code Requirements.............................................................................................................2-7

S. Specifications..................................................................................................................................................2-7

S.1. Design of Indicating and Recording Elements and of Recorded Representations. ...............................2-7

S.1.1. Zero Indication......................................................................................................................2-7

S.1.2. Value of Scale Division Units................................................................................................2-8

S.1.3. Graduations. ..........................................................................................................................2-9

S.1.4. Indicators...............................................................................................................................2-9

S.1.5. Weighbeams........................................................................................................................2-10

S.1.6. Poises. .................................................................................................................................2-11

S.1.7. Capacity Indication, Weight Ranges, and Unit Weights.....................................................2-11

S.1.8. Computing Scales. ..............................................................................................................2-11

S.1.9. Prepackaging Scales............................................................................................................2-13

S.1.10. Adjustable Components. .....................................................................................................2-13

S.1.11. Provision for Sealing...........................................................................................................2-13

S.1.12. Manual Weight Entries. ......................................................................................................2-14

S.1.13. Vehicle On-Board Weighing Systems: Vehicle in Motion. ...............................................2-14

S.1.14. Weigh-in-Motion (WIM) Vehicle Scales............................................................................2-14

S.2. Design of Balance, Tare, Level, Damping, and Arresting Mechanisms. ............................................2-15

S.2.1. Zero-Load Adjustment........................................................................................................2-15

S.2.2. Balance Indicator. ...............................................................................................................2-16

S.2.3. Tare. ....................................................................................................................................2-17

S.2.4. Level-Indicating Means. .....................................................................................................2-17

S.2.5. Damping Means. .................................................................................................................2-17

S.3. Design of Load-Receiving Elements. .................................................................................................2-18

S.3.1. Travel of Pans of Equal-Arm Scale.....................................................................................2-18

S.3.2. Drainage..............................................................................................................................2-18

S.3.3. Scoop Counterbalance.........................................................................................................2-18

S.3.4. Length of Weigh-In-Motion Vehicle Scales. ......................................................................2-18

S.4. Design of Weighing Elements. ...........................................................................................................2-19

S.4.1. Antifriction Means. .............................................................................................................2-19

S.4.2. Adjustable Components. .....................................................................................................2-19

S.4.3. Multiple Load-Receiving Elements. ...................................................................................2-19

S.5. Design of Weighing Devices, Accuracy Class. ...................................................................................2-19

S.5.1. Designation of Accuracy Class. ..........................................................................................2-19

S.5.2. Parameters for Accuracy Class...........................................................................................2-19

S.5.3. Multi-Interval and Multiple Range Scales, Division Value. ...............................................2-19

S.5.4. Relationship of Minimum Load Cell Verification Interval Value to the Scale Division......2-19

S.6. Marking Requirements........................................................................................................................2-22

S.6.1. Nominal Capacity; Vehicle and Axle-Load Scales..............................................................2-22

S.6.2. Location of Marking Information. ......................................................................................2-22

S.6.3. Scales, Main Elements, and Components of Scales or Weighing Systems.........................2-22

S.6.4. Railway Track Scales..........................................................................................................2-27

S.6.5. Livestock Scales..................................................................................................................2-28
2.20. Scales Handbook 44 – 2022

2-4

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

S.6.6. Counting Feature, Minimum Individual Piece Weight, and Minimum Sample Piece Count ....

............................................................................................................................................2-28

N. Notes..............................................................................................................................................................2-28

N.1. Test Procedures...................................................................................................................................2-28

N.1.1. Increasing-Load Test...........................................................................................................2-28

N.1.2. Decreasing-Load Test (Automatic Indicating Scales).........................................................2-28

N.1.3. Shift Test.............................................................................................................................2-29

N.1.4. Sensitivity Test....................................................................................................................2-32

N.1.5. Discrimination Test.............................................................................................................2-32

N.1.6. RFI Susceptibility Tests, Field Evaluation..........................................................................2-33

N.1.7. Ratio Test. ...........................................................................................................................2-33

N.1.8. Material Tests......................................................................................................................2-33

N.1.9. Zero-Load Balance Change.................................................................................................2-33

N.1.10. Counting Feature Test.........................................................................................................2-33

N.1.11. Substitution Test. ................................................................................................................2-33

N.1.12. Strain-Load Test..................................................................................................................2-33

N.2. Verification (Testing) Standards.........................................................................................................2-33

N.3. Minimum Test Weights and Test Loads. ............................................................................................2-33

N.3.1. Minimum Test-Weight Load and Tests for Railway Track Scales. ....................................2-34

N.3.2. Field Standard Weight Carts. ..............................................................................................2-35

N.4. Coupled-in-Motion Railroad Weighing Systems................................................................................2-36

N.4.1. Weighing Systems Used to Weigh Trains of Less Than Ten Cars......................................2-36

N.4.2. Weighing Systems Placed in Service Prior to January 1, 1991, and Used to Weigh Trains of 

Ten or More Cars. ...............................................................................................................2-36

N.4.3. Weighing Systems Placed in Service on or After January 1, 1991, and Used to Weigh Trains 

of Ten or More Cars............................................................................................................2-36

N.5. Uncoupled-in-Motion Railroad Weighing System. ............................................................................2-37

N.6. Nominal Capacity of Prescription Scales............................................................................................2-37

N.7. Weigh-in-Motion Vehicle Scales........................................................................................................2-38

N.7.1. Reference Scale...................................................................................................................2-38

N.7.2. Reference Vehicle. ..............................................................................................................2-38

N.7.3. Test Speeds .........................................................................................................................2-38

N.7.4. Static Tests for Weigh-in-Motion Vehicle Scales...............................................................2-38

N.7.5. Dynamic Tests for Weigh-in-Motion Vehicle Scales .........................................................2-38

T. Tolerances Applicable to Devices not Marked I, II, III, III L, or IIII.....................................................2-39

T.1. Tolerance Values. ...............................................................................................................................2-39

T.1.1. General................................................................................................................................2-39

T.1.2. Postal and Parcel Post Scales. .............................................................................................2-39

T.2. Sensitivity Requirement (SR). ............................................................................................................2-41

T.2.1. Application..........................................................................................................................2-41

T.2.2. General................................................................................................................................2-41

T.2.3. Prescription Scales. .............................................................................................................2-41

T.2.4. Jewelers’ Scales. .................................................................................................................2-41

T.2.5. Dairy-Product Test Scales...................................................................................................2-41

T.2.6. Grain Test Scales. ...............................................................................................................2-41

T.2.7. Vehicle, Axle-Load, Livestock, and Animal Scales............................................................2-41

T.2.8. Railway Track Scales..........................................................................................................2-41

T.3. Sensitivity Requirement, Equilibrium Change Required....................................................................2-42

T.N. Tolerances Applicable to Devices Marked I, II, III, III L, and IIII.........................................................2-42

T.N.1. Principles. ...........................................................................................................................................2-42

T.N.1.1. Design. ................................................................................................................................2-42

T.N.1.2. Accuracy Classes. ...............................................................................................................2-42
Handbook 44 – 2022 2.20. Scales

2-5

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

T.N.1.3. Scale Division. ....................................................................................................................2-42

T.N.2.Tolerance Application.........................................................................................................................2-42

T.N.2.1. General................................................................................................................................2-42

T.N.2.2. Type Evaluation Examinations. ..........................................................................................2-42

T.N.2.3. Subsequent Verification Examinations. ..............................................................................2-42

T.N.2.4. Multi-Interval and Multiple Range (Variable Division-Value) Scales................................2-42

T.N.2.5. Ratio Tests. .........................................................................................................................2-42

T.N.3.Tolerance Values. ...............................................................................................................................2-43

T.N.3.1. Maintenance Tolerance Values. ..........................................................................................2-43

T.N.3.2. Acceptance Tolerance Values. ............................................................................................2-43

T.N.3.3. Wheel-Load Weighers and Portable Axle-Load Weighers of Class IIII.............................2-43

T.N.3.4. Crane and Hopper (Other than Grain Hopper) Scales.........................................................2-43

T.N.3.5. Separate Main Elements: Load Transmitting Element, Indicating Element, Etc. ..............2-43

T.N.3.6. Coupled-In-Motion Railroad Weighing Systems................................................................2-43

T.N.3.7. Uncoupled-in-Motion Railroad Weighing Systems. ...........................................................2-44

T.N.3.8. Dynamic Monorail Weighing System.................................................................................2-44

T.N.3.9. Materials Test on Customer-Operated Bulk Weighing Systems for Recycled Materials. ..2-44

T.N.3.10. Prescription Scales with a Counting Feature.......................................................................2-44

T.N.3.11. Tolerances for Substitution Test. ........................................................................................2-45

T.N.3.12. Tolerances for Strain-Load Test..........................................................................................2-45

T.N.4. Agreement of Indications....................................................................................................................2-45

T.N.4.1. Multiple Indicating/Recording Elements. ...........................................................................2-45

T.N.4.2. Single Indicating/Recording Element. ................................................................................2-45

T.N.4.3. Single Indicating Element/Multiple Indications..................................................................2-45

T.N.4.4. Shift or Section Tests. .........................................................................................................2-45

T.N.4.5. Time Dependence. ..............................................................................................................2-45

T.N.4.6. Time Dependence (Creep) for Load Cells during Type Evaluation....................................2-46

T.N.4.7. Creep Recovery for Load Cells During Type Evaluation. ..................................................2-47

T.N.5.Repeatability. ......................................................................................................................................2-47

T.N.6. Sensitivity. ..........................................................................................................................................2-48

T.N.6.1. Test Load. ...........................................................................................................................2-48

T.N.6.2. Minimum Change of Indications.........................................................................................2-48

T.N.7. Discrimination. ...................................................................................................................................2-48

T.N.7.1. Analog Automatic Indicating (i.e., Weighing Device with Dial, Drum, Fan, etc.).............2-48

T.N.7.2. Digital Automatic Indicating...............................................................................................2-48

T.N.8.Influence Factors.................................................................................................................................2-48

T.N.8.1. Temperature. .......................................................................................................................2-48

T.N.8.2. Barometric Pressure. ...........................................................................................................2-49

T.N.8.3. Electric Power Supply.........................................................................................................2-49

T.N.9.Radio Frequency Interference (RFI) and Other Electromagnetic Interference Susceptibility. ...........2-49

UR. User Requirements ......................................................................................................................................2-50

UR.1. Selection Requirements. .....................................................................................................................2-50

UR.1.1. General................................................................................................................................2-50

UR.1.2. Grain Hopper Scales. ..........................................................................................................2-51

UR.1.3. Value of the Indicated and Recorded Scale Division. .........................................................2-51

UR.1.4. Grain-Test Scales: Value of the Scale Divisions................................................................2-51

UR.1.5. Recording Element, Class III L Railway Track Scales........................................................2-51

UR.2. Installation Requirements. ..................................................................................................................2-52

UR.2.1. Supports. .............................................................................................................................2-52

UR.2.2. Suspension of Hanging Scale..............................................................................................2-52

UR.2.3. Protection From Environmental Factors. ............................................................................2-52

UR.2.4. Foundation, Supports, and Clearance..................................................................................2-52

UR.2.5. Access to Weighing Elements.............................................................................................2-52
2.20. Scales Handbook 44 – 2022

2-6

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

UR.2.6. Approaches. ........................................................................................................................2-52

UR.2.7. Stock Racks.........................................................................................................................2-53

UR.2.8. Hoists. .................................................................................................................................2-53

UR.2.9. Provision for Testing Dynamic Monorail Weighing Systems..............................................2-53

UR.2.10. Primary Indicating Elements Provided by the User............................................................2-53

UR.3. Use Requirements. ..............................................................................................................................2-53

UR.3.1. Recommended Minimum Load...........................................................................................2-53

UR.3.2. Maximum Load...................................................................................................................2-54

UR.3.3. Single-Draft Vehicle Weighing...........................................................................................2-56

UR.3.4. Wheel-Load Weighing........................................................................................................2-56

UR.3.5. Special Designs...................................................................................................................2-57

UR.3.6. Wet Commodities. ..............................................................................................................2-57

UR.3.7. Minimum Load on a Vehicle Scale.....................................................................................2-57

UR.3.8. Minimum Load for Weighing Livestock.............................................................................2-57

UR.3.9. Use of Manual Weight Entries............................................................................................2-57

UR.3.10. Dynamic Monorail Weighing Systems. ..............................................................................2-57

UR.3.11. Minimum Count..................................................................................................................2-58

UR.3.12. Correct Stored Piece Weight...............................................................................................2-58

UR.3.13. Fault Indications for Weigh-in-Motion Vehicle Scales.......................................................2-58

UR.4. Maintenance Requirements.................................................................................................................2-58

UR.4.1. Balance Condition...............................................................................................................2-58

UR.4.2. Level Condition...................................................................................................................2-58

UR.4.3. Scale Modification. .............................................................................................................2-58

UR.5. Coupled-in-Motion Railroad Weighing Systems................................................................................2-58

Scales Code Index ...................................................................................................................................................2-61
Handbook 44 – 2022 2.20. Scales

2-7

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

Section 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. Additional Code Requirements. – In addition to the requirements of this code, devices covered by the Scales

code shall meet the requirements of Section 1.10. General Code.

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 1993)

(Amended 1987)

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. A “center-of-zero” indication 

may operate when zero is indicated for gross and/or net mode(s).

[Nonretroactive as of January 1, 1993]

(c) For electronic cash registers (ECRs) and point-of-sale systems (POS systems) the display of

measurement units shall be a minimum of 9.5 mm (

3

/8 inch) in height. 

[Nonretroactive as of January 1, 2021]

(Added 2019)

(Amended 1992, 2008, and 2019)
2.20. Scales Handbook 44 – 2022

2-8

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

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; or

Examples: scale divisions may be 10, 20, 50, 100; or 0.01, 0.02, 0.05; or 0.1, 0.2, 0.5, etc.

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

Examples: scale divisions may be 1⁄2, 1⁄4, 1

/8, 1/16, etc.

[Nonretroactive as of January 1, 1986]

S.1.2.1. Digital Indicating Scales, 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.

The requirement that the value of the scale division be expressed only as 1, 2, or 5, or a decimal multiple or 

submultiple of only 1, 2, or 5 does not apply to net weight indications and recorded representations that are 

calculated from gross and tare weight indications where the scale division of the gross weight is different 

from the scale division of the tare weight(s) on multi-interval or multiple range scales. For example, a 

multiple range or multi-interval scale may indicate and record tare weights in a lower weighing range (WR) 

or weighing segment (WS), gross weights in the higher weighing range or weighing segment, and net weights 

as follows:

55 kg Gross Weight (WR2 d = 5 kg) 10.05 lb Gross Weight (WS2 d = 0.05 lb)

– 4 kg Tare Weight (WR1 d = 2 kg) – 0.06 lb Tare Weight (WS1 d = 0.02 lb)

= 51 kg Net Weight (Mathematically Correct) = 9.99 lb Net Weight (Mathematically Correct)

[Nonretroactive as of January 1, 1989]

(Added 1987) (Amended 2008)

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 is 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” 
Handbook 44 – 2022 2.20. Scales

2-9

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

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 Scales. 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)

(Amended 2021)

S.1.2.3. Prescription Scale with a Counting Feature. – A Class I or Class II prescription scale with an 

operational counting feature shall not calculate a piece weight or total count unless the sample used to 

determine the individual piece weight meets the following conditions:

(a) minimum individual piece weight is greater than or equal to 3 e; and

(b) minimum sample piece count is greater than or equal to 10 pieces.

(Added 2003)

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 % 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).

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.
2.20. Scales Handbook 44 – 2022

2-10

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

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 % of the distance from 

the weighbeam fulcrum to the weighbeam tip.

Table 1M.

Minimum Travel of Weighbeam of Beam Scale

Between Limiting Stops

Table 1.

Minimum Travel of Weighbeam of Beam Scale

Between Limiting Stops

Distance from 

Weighbeam Fulcrum to 

Limiting Stops

(centimeters)

Minimum Travel 

Between

Limiting Stops

(millimeter)

Distance from 

Weighbeam Fulcrum to 

Limiting Stops

(inches)

Minimum Travel 

Between 

Limiting Stops

(inch)

30 or less 10 12 or less 0.4

30+ to 50, inclusive 13 12+ to 20, inclusive 0.5

50+ to 100, inclusive 18 20+ to 40, inclusive 0.7

Over 100 23 Over 40 0.9

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:

(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
Handbook 44 – 2022 2.20. Scales

2-11

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

(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, the 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 

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

is in excess of 105 % of scale capacity.

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

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

[Nonretroactive as of January 1, 1993]

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.

(Amended 1990, 1992, and 1995)

S.1.8. Computing Scales.

S.1.8.1. 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 Handbook 44 – 2022

2-12

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

(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. (Also

see S.1.8.2. Money-Value Computation.)

S.1.8.2. Money-Value Graduations, U.S. Customary 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. (Also

see S.1.8.2. Money-Value Computation.)

S.1.8.3. 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. General Code G-S.5.5. MoneyValues, Mathematical Agreement.)

S.1.8.4. 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 g.

(Amended 1985 and 1995)

S.1.8.4.1. 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.1.8.5. 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;

(b) the unit price;

(c) the total price;

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

number; and

(e) the tare weight.

[Nonretroactive as of January 1, 2025]
Handbook 44 – 2022 2.20. Scales

2-13

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

Weight values shall be identified as tare and net, or gross if applicable. The unit of weight shall be identified 

as kilograms, kg, grams, g, ounces, oz, pounds, or lb. 

For devices interfaced with scales indicating in metric units, the unit price may be expressed in price per 

100 grams. 

(Amended 1995, 2005, and 2021)

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.

S.1.11.1. Devices and Systems Adjusted Using a Removable Digital Storage Device. – For devices and 

systems in which the calibration or configuration parameters, as defined in Appendix D, can be changed by 

use of a removable digital storage device, security shall be provided for those parameters as specified in 

G-S.8.2. Devices and Systems Adjusted Using Removable Digital Storage Devices. 

S.1.11.2. All Other Devices. – Except on Class I scales and devices specified in S.1.11.1., the following 

provisions for sealing apply:

(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. Categories of 

Device and Methods of Sealing.

[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, 1993, and 2019)
2.20. Scales Handbook 44 – 2022

2-14

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

S.1.12. Manual Weight Entries. – A device when being used for direct sale shall accept an entry of a manual 

gross or net weight value only when the scale gross or net* weight indication is at zero. 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] [*Nonretroactive as of January 1, 2005]

(Added 1992) (Amended 2004)

S.1.13. Vehicle On-Board Weighing Systems: Vehicle in Motion. – When the vehicle is in motion, a vehicle 

on-board weighing system shall either:

(a) be accurate; or

(b) inhibit the weighing operation.

(Added 1993)

S.1.14. Weigh-in-Motion (WIM) Vehicle Scales.

S.1.14.1. Identification of a Fault. – Fault conditions shall be presented to the customer and the operator 

in a clear and unambiguous manner. No weight values shall be indicated or recorded when a fault condition 

is detected. The following fault conditions shall be identified, if applicable:

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

Categories of Device Methods 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. 

The 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 10 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)
Handbook 44 – 2022 2.20. Scales

2-15

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

(a) Vehicle speed was below the minimum or above the maximum speed as specified by the 

manufacturer.

(b) A change in vehicle speed greater than that specified by the manufacturer was detected.

(c) Vehicle direction of travel was not valid for the installation.

(d) The amount of time all vehicle axles were simultaneously on the scale was below the minimum data 

acquisition time.

(e) Vehicle path of travel was outside the lateral side edges of the load-receiving element.

S.1.14.2. Information to be Recorded. – In addition to the information that is normally recorded for 

vehicle scales, the following shall also be printed and/or stored electronically for each vehicle weighment, if 

applicable:

(a) Scale identification if more than one lane at the site has the ability to weigh a vehicle in motion.

(b) Vehicle direction of travel if the weigh-in-motion vehicle scale is bi-directional.

(Added 2021)

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.

Except for an initial zero-setting mechanism, an automatic zero adjustment outside the limits specified in 

S.2.1.3. Scales Equipped with an Automatic Zero-Tracking Mechanism is prohibited.

(Amended 2010)

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 plus or minus:

(a) 3.0 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) 1.0 scale division for all other scales.

S.2.1.3. Scales Equipped with an Automatic Zero-Tracking Mechanism.

S.2.1.3.1. Automatic Zero-Tracking Mechanism for Scales Manufactured Between 

January 1, 1981, and January 1, 2007. – The maximum load that can be “rezeroed,” when either 

placed on or removed from the platform all at once under normal operating conditions, shall be for:

(a) bench, counter, and livestock scales: 0.6 scale division;
2.20. Scales Handbook 44 – 2022

2-16

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

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

(c) all other scales: 1.0 scale division.

(Amended 2005)

S.2.1.3.2. Automatic Zero-Tracking Mechanism for Scales Manufactured on or after 

January 1, 2007. – The maximum load that can be “rezeroed,” when either placed on or removed from 

the platform all at once under normal operating conditions, shall be:

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

(b) for all other scales: 0.5 scale division.

(Added 2005)

S.2.1.3.3. Means to Disable Automatic Zero-Tracking Mechanism on Class III L Devices. –

Class III L devices equipped with an automatic zero-tracking mechanism shall be designed with a 

sealable means that would allow zero tracking to be disabled during the inspection and test of the device.

[Nonretroactive as of January 1, 2001]

(Added 1999) (Amended 2005)

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 % 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. – Scales of accuracy Classes I, II, and III may be equipped 

with an initial zero-setting device.

(a) For weighing, load-receiving, and indicating elements in the same housing or covered on the same 

CC, an initial zero-setting mechanism shall not zero a load in excess of 20 % 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.

(b) For indicating elements not permanently attached to weighing and load-receiving elements covered 

on a separate CC, the maximum initial zero-setting mechanism range of electronic indicators shall 

not exceed 20 % of the configured capacity.

[Nonretroactive as of January 1, 2009]

(Added 2008)

(Added 1990) (Amended 2008)

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).
Handbook 44 – 2022 2.20. Scales

2-17

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

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 and multi-interval scales 

or multiple range scales when the value of tare is determined in a lower weighing range or weighing segment), 

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. *

[*Nonretroactive as of January 1, 1983]

(Amended 1985 and 2008)

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 % of the 

scale capacity to within 0.02 % 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 meansif its weighing performance is changed by an amount 

greater than the appropriate acceptance tolerance when it is tilted up to and including 5 % rise over run in any 

direction from a level position and rebalanced. 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 Class I and II.]

Note: Portable wheel-load weighers and portable axle-load scales shall be accurate when tilted up to and including 5 % rise 

over run in any direction from a level position and rebalanced.

(Amended 1991 and 2008)

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

within tolerance when the weighing system is tilted up to and including 5 % rise over run in any direction 

from a level position and rebalanced. 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) (Amended 2008)

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 plus or minus:
2.20. Scales Handbook 44 – 2022

2-18

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

(a) 3.0 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; and

(b) 1.0 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 scales shall be equipped with appropriate means for arresting the oscillation of the mechanism.

S.2.5.3. Class I and Class II Prescription Scales with a Counting Feature. – A Class I or Class II 

prescription scale shall indicate to the operator when the piece weight computation is complete by a stable 

display of the quantity placed on the load-receiving element.

(Added 2003)

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 Table 2.

Table 2M.

Minimum Travel of Pans of

Nonautomatic Indicating Equal-Arm Scale

without Balance Indicator

Table 2.

Minimum Travel of Pans of

Nonautomatic Indicating Equal-Arm Scale

without Balance Indicator

Nominal Capacity

(kilograms)

Minimum Travel of 

Pans

(millimeters)

Nominal Capacity

(pounds)

Minimum Travel of 

Pans

(inch)

2 or less 9 4 or less 0.35

2+ to 5, inclusive 13 4+ to 12, inclusive 0.5

5+ to 12, inclusive 19 12+ to 26, inclusive 0.75

Over 12 25 Over 26 1.0

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.3.4. Length of Weigh-In-Motion Vehicle Scales. – The load-receiving element shall be of sufficient length 

to allow the weighment of any vehicle intended to be weighed on the scale in a single draft (i.e., all axles of the 

vehicle are on the load-receiving element simultaneously during the weighment).

(Added 2021)
Handbook 44 – 2022 2.20. Scales

2-19

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

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 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 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.”1

(Added 1986) (Amended 1995)

S.5.4. Relationship of Minimum Load Cell Verification Interval Value to the Scale Division. – The 

relationship of the value for the minimum load cell verification scale interval, vmin, to the scale division, d, for a 

specific scale using National Type Evaluation Program (NTEP) certified load cells shall comply with the 

following formulae where N is the number of load cells in a single independent1 weighing/load-receiving element

(such as hopper, railroad track, or vehicle scale weighing/load-receiving elements):

(a) for scales without lever systems; and

(b) for scales with lever systems.

1”Independent” means with a weighing/load-receiving element not attached to adjacent elements and with its own 

A/D conversion circuitry and displayed weight.

[*When the value of the scale division, d, is different from 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 weighing/load-receiving elements or scales, which satisfy all the 

following criteria:

1 Footnote 1 to Table 3 Parameters for Accuracy Classes.

( )

* min N scalemultiple

d

v

×

≤

N

d

v * min ≤
2.20. Scales Handbook 44 – 2022

2-20

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

- the complete weighing/load-receiving element or scale has been evaluated for compliance with 

T.N.8.1. Temperature under the NTEP;

- the complete weighing/load-receiving element or scale has received an NTEP Certificate of 

Conformance; and

- the complete weighing/load-receiving element or scale is equipped with an automatic zero-tracking 

mechanism which cannot be made inoperative in the normal weighing mode. (A test mode which 

permits the disabling of the automatic zero-tracking mechanism is permissible, provided the scale 

cannot function normally while in this mode.

[Nonretroactive as of January 1, 1994]

(Added 1993) (Amended 1996 and 2016)
Handbook 44 – 2022 2.20. Scales

2-21

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

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

III2,5 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

U.S. Customary Units

III5 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 Class III scale marked “For prescription weighing only” may have a verification scale division (e) not less 

than 0.01 g.

(Added 1986) (Amended 2003)

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 1000.

4 On a multiple range or multi-intervalscale, 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.

(Added 1997)

5 The minimum number of scale divisions for a Class III Hopper Scale used for weighing grain shall be 2000.)

[Nonretroactive as of January 1, 1986]

(Amended 1986, 1987, 1997, 1998, 1999, 2003, and 2004)
2.20. Scales Handbook 44 – 2022

2-22

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

S.6. Marking Requirements. – (Also see G-S.1. Identification, G-S.4. Interchange or Reversal of Parts, 

G-S.6. Marking Operational Controls, Indications, and Features, G-S.7. Lettering, G-UR.2.1.1. Visibility of 

Identification, and UR.3.4.1. Use in Pairs.)

S.6.1. Nominal Capacity; Vehicle and Axle-Load Scales. – For all vehicle and 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 × (N − 0.5)

where N = the number of sections in the scale.

[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 Section 1.10. General Code, G-S.1. Identification and 

Section 2.20. Scales Code, S.6. Marking Requirements 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 (loadreceiving 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 (NTEP), 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. Marking Requirements and explained in the accompanying notes in 

Table S.6.3.b. Notes for Table S.6.3.a.

(Added 1990)
Handbook 44 – 2022 2.20. Scales

2-23

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

Table S.6.3.a.

Marking Requirements

Weighing Equipment

To Be Marked With ⇓

Weighing, 

LoadReceiving, 

and 

Indicating 

Element in 

Same Housing 

or Covered on 

the Same CC1

Indicating 

Element not 

Permanently 

Attached to 

Weighing and 

LoadReceiving 

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

Minimum and Maximum Speed (25) X

Maximum Speed Change (26) X

Vehicle Direction Restriction (27) X

Safe Load Limit X

Load Cell Verification Interval

(vmin) (21) X

Section Capacity and Prefix

(14)(20)(22)(24) X X
2.20. Scales Handbook 44 – 2022

2-24

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

Table S.6.3.a.

Marking Requirements

Note: For applicable notes, 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 2001)

(Added 1990) (Amended 1992, 1999, 2000, 2001, 2002, 2004, and 2021)

Table S.6.3.b.

Notes for Table S.6.3.a. Marking Requirements

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

[*Nonretroactive as of January 1, 2003]

(Also see G-S.1. Identification.) [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]. (Also 

see G-S.1. Identification.)

3. The device shall be marked with the nominal capacity. The nominal capacity shall be shown together with the 

value of the scale division (e.g., 15 × 0.005 kg, 30 × 0.01 lb, or capacity = 15 kg, d = 0.005 kg) in a clear and 

conspicuous manner and be readily apparent when viewing the reading face of the scale indicator unless already 

apparent by the design of the device. Each scale division value or weight unit shall be marked on multiple range 

or multi-interval scales. 

[Nonretroactive as of January 1, 1983]

(Amended 2005)

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]

(Amended 1999)

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]
Handbook 44 – 2022 2.20. Scales

2-25

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

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. Identification 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)

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

words, visible to the operator and to the 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 sides with the statement “The counting feature is not legal 

for trade,” except when a Class I or Class II prescription scale complies with all Handbook 44 requirements 

applicable to counting features.

[*Nonretroactive as of 1986]

(Amended 1994 and 2003)

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]. (Also 

see G-S.1. Identification.) 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
2.20. Scales Handbook 44 – 2022

2-26

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

Table S.6.3.b.

Notes for Table S.6.3.a. Marking Requirements

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

[*Nonretroactive as of January 1, 1989]

(Amended 1992)

19. For weighing and load-receiving elements not permanently attached to indicating element or covered by a 

separate CC.

[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) (Amended 2003)

Note: The marked section capacity for livestock weighing may be less than the marked CLC for vehicle 

weighing.

(Amended 2003)

23. Required only if a CC has been issued for the device or equipment. 

[Nonretroactive as of January 1, 2003]

(G-S.1. Identification (e) Added 2001)

24. The section capacity shall be prefaced by the words “Section Capacity” or an abbreviation of that term. 

Abbreviations shall be “Sec Cap” or “Sec C.” All capital letters and periods may be used.

[Nonretroactive as of January 1, 2005]

(Added 2004)

25. Weigh-in-motion vehicle scales must be marked with minimum and maximum vehicle speed limitations.

(Added 2021)

26. Weigh-in-motion vehicle scales must be marked with the maximum vehicle speed change allowed during the 

weighment.

(Added 2021)

27. Weigh-in-motion vehicle scales must be marked as “uni-directional” if the travel direction is restricted.

(Added 2021)
Handbook 44 – 2022 2.20. Scales

2-27

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

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 marking shall satisfy the following:

(a) For scales manufactured from January 1, 2002, through December 31, 2013:

(1) the nominal capacity of a scale with more than two sections shall not exceed twice its rated section 

capacity; and

(2) the nominal capacity of a two-section scale shall not exceed its rated section capacity.

(b) For scales manufactured on or after January 1, 2014, the nominal scale capacity shall not exceed the 

lesser of:

(1) the sum of the Weigh Module Capacities as shown in Table S.6.4.M. and Table S.6.4.; or

(2) the Rated Section Capacity (RSC) multiplied by the Number of Sections (Ns) minus the Number of Dead Spaces (Nd) minus 0.5. As a formula this is stated as:

RSC × (Ns – Nd – 0.5)

;or

(3) 290 300 kg (640 000 lb).

(Amended 1988, 2001, 2002, and 2013)

Table S.6.4.M.

Railway Track Scale – Weigh Module Capacity

Weigh Module Length

(meters)

Weigh Module Capacity

(kilograms)

< 1.5 36 300

1.5 to < 3.0 72 600

3.0 to < 4.5 108 900

4.5 to < 7.0 145 100

7.0 to < 9.0 168 700

9.0 to < 10.5 192 300

10.5 to < 12.0 234 100

12.0 to < 17.0 257 600

Note: The capacity of a particular module is based on its length as shown above. To determine the “sum of 

the weigh module capacities” referenced in paragraph S.6.4.(b)(1): (1) determine the length of each 

individual weigh module in the scale; (2) find its corresponding “weigh module capacity” in the table above; 

and (3) add all of the individual weigh module capacities.”

(Table Added 2013)
2.20. Scales Handbook 44 – 2022

2-28

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

Table S.6.4.

Railway Track Scale – Weigh Module Capacity

Weigh Module Length

(feet)

Weigh Module Capacity

(pounds)

< 5 80 000

5 to < 10 160 000

10 to < 15 240 000

15 to < 23 320 000

23 to < 29 372 000

29 to < 35 424 000

35 to < 40 516 000

40 to < 56 568 000

Note: The capacity of a particular module is based on its length as shown above. To determine the “sum of 

the weigh module capacities” referenced in paragraph S.6.4.(b)(1): (1) determine the length of each 

individual weigh module in the scale; (2) find its corresponding “weigh module capacity” in the table above; 

and (3) add all of the individual weigh module capacities.”

(Table Added 2013)

S.6.5. Livestock Scales. – A livestock scale manufactured prior to January 1, 1989, or after January 1, 2003, 

shall be marked with the maximum capacity of each section of the load-receiving element of the scale. Livestock 

scales manufactured between January 1, 1989, and January 1, 2003, shall be marked with either the Concentrated 

Load Capacity (CLC) or the Section Capacity. 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)

Also see Note 14 in Table S.6.3.b. Notes for Table S.6.3.a.

S.6.6. Counting Feature, Minimum Individual Piece Weight, and Minimum Sample Piece Count. – A 

Class I or Class II prescription scale with an operational counting feature shall be marked with the minimum 

individual piece weight and minimum number of pieces used in the sample to establish an individual piece weight.

(Added 2003)

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 
Handbook 44 – 2022 2.20. Scales

2-29

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

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. (Also see Table 6. Maintenance Tolerances.)

(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. Dairy-Product Test Scales. – A shift test shall be conducted with a test load of 18 g successively 

positioned at all points on which a weight might reasonably be placed in the course of normal use of the 

scale.

N.1.3.2. Equal-Arm Scales. – A shift test shall be conducted with a half-capacity test load centered 

successively at four points positioned equidistance between the center and the front, left, back, and right 

edges of each pan as shown in the diagrams below. An equal test load shall be centered on the other pan.

N.1.3.3. Vehicle Scales, Axle-Load Scales, and Livestock Scales.

N.1.3.3.1. Vehicle Scales, Axle-Load Scales, and Combination Vehicle/Livestock Scales.

(a) Minimum Shift Test. – At least one shift test shall be conducted with a minimum test load of 

12.5 % of scale capacity, which may be performed anywhere on the load-receiving element 

using the prescribed test patterns and maximum test loads specified below. (Combination 

Vehicle/Livestock Scales shall also be tested consistent with N.1.3.3.2. Prescribed Test Pattern 

and Test Loads for Livestock Scales with More Than Two Sections and Combination 

Vehicle/Livestock Scales.)

(Amended 1991, 2000, and 2003)

(b) Prescribed Test Pattern and Loading for Vehicle Scales, Axle-Load Scales, and 

Combination Vehicle/Livestock Scales. – 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 (c), 

(d), or (e) as applicable. An example of a possible test pattern is shown in the diagram below.

(Amended 1997, 2001, and 2003)

4’ 4’ 4’ 4’ 4’

Section

1

Midway between 

sections 1 and 2

Section

2

Midway between 

sections 2 and 3

Section 

3
2.20. Scales Handbook 44 – 2022

2-30

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

(c) Loading Precautions for Vehicle Scales, Axle-Load Scales, and Combination 

Vehicle/Livestock Scales. – 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) × 3.0 m (10 ft) 

or the width of the scale platform, whichever is less; 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) × 0.9 × 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. Span Maximum Load for the length of the area covered by 

the test load. For load-receiving elements installed prior to January 1, 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 above.

(Amended 1997 and 2003)

(d) Multiple Pattern Loading. – To test to the nominal capacity, multiple patterns may be 

simultaneously loaded in a manner consistent with the method of use.

(e) 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, 1991, 1997, 2000, 2001, and 2003)

(Amended 2003)

N.1.3.3.2. Prescribed Test Pattern and Test Loads for Livestock Scales with More Than Two 

Sections and Combination Vehicle/Livestock Scales. – A minimum test load of 5 000 kg (10 000 lb) 

or one-half of the rated section capacity, whichever is less, shall be placed, as nearly as possible, 

successively over each main load support as shown in the diagram below. For livestock scales

manufactured between January 1, 1989, and January 1, 2003, the required loading shall be no greater 

than one-half CLC. 



Position 1



Position 2



Position 3

 

Position 6



Position 5



Position 4



 = Load Bearing Point

(Added 2003) (Amended 2016)

N.1.3.3.3. Prescribed Test Patterns and Test Loads for Two-Section Livestock Scales. – A shift 

test shall be conducted using the following prescribed test loads and test patterns: 1) When a single field 

standard weight is used, the prescribed test load shall be applied centrally in the prescribed test pattern; 

or 2) When multiple field standard weights are used as the prescribed test load, the load shall be applied 

in a consistent pattern in the shift test positions throughout the test and applied in a manner that does not 

concentrate the load in a test pattern that is less than when the same load is a single field standard weights 

on the load-receiving element.
Handbook 44 – 2022 2.20. Scales

2-31

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

The shift test load shall not exceed one-half the rated section capacity or one-half the rated concentrated 

load capacity whichever is applicable, using either:

(a) A one-half nominal capacity test load centered as nearly as possible, successively at the center 

of each quarter of the load-receiving element as shown in N.1.3.7. All Other Scales Except 

Crane Scales, Hanging Scales, Hopper Scales, Wheel-Load Weighers, and Portable Axle-Load 

Weighers Figure 1; or

(b) A one-quarter nominal capacity test load centered as nearly as possible, successively over each 

main load support as shown in N.1.3.7. All Other Scales Except Crane Scales, Hanging Scales, 

Hopper Scales, Wheel-Load Weighers, and Portable Axle-Load Weighers Figure 2.

(Added 2007) (Amended 2016)

N.1.3.4. 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.1.3.5. 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.1.3.5.1. Dynamic Monorail Weighing Systems. – Dynamic tests with livestock carcasses or 

portions of carcasses shall be conducted during normal plant production. No less than 20 test loads using 

carcasses or portions of carcasses of the type normally weighed shall be used in the dynamic test. If the 

plant conveyor chain does not space or prevent the carcasses or portions of carcasses from touching one 

another, dynamic tests shall not be conducted until this condition has been corrected.

All carcasses or portions of 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 static weighing of the carcasses or portions of carcasses shall first be 

tested statically with certified test weights that have been properly protected from the harsh environment 

of the packing plant to ensure they maintain accuracy.)

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 or portions of carcasses, static weights shall be obtained before and after multiple dynamic 

tests. If the carcass or portion of a carcass changes weight between static tests, the amount of weight 

change shall be taken into account, or the carcass or portion of a carcass shall be disregarded for tolerance 

purposes.

Note: For a dynamic monorail test, the reference scale shall comply with the principles in Appendix A, Fundamental 

Considerations, paragraph 3.2. Tolerances for Standards.

(Added 1996) (Amended 1999 and 2007)

N.1.3.6. 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 Handbook 44 – 2022

2-32

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

N.1.3.7. All Other Scales Except Crane Scales, Hanging Scales, Hopper Scales, Wheel-Load 

Weighers, and Portable Axle-Load Weighers. – A shift test shall be conducted using the following 

prescribed test loads and test patterns. A single field standard weight used as the prescribed test load shall 

be applied centrally in the prescribed test pattern. When multiple field standard weights are used as the 

prescribed test load, the load shall be applied in a consistent pattern in the shift test positions throughout the 

test and applied in a manner that does not concentrate the load in a test pattern that is less than when that 

same load is a single field standard weight on the load-receiving element.

(a) For scales with a nominal capacity of 500 kg (1000 lb) or less, a shift test shall be conducted using 

a one-third nominal capacity test load (defined as test weights in amounts of at least 30 % of scale 

capacity, but not to exceed 35 % of scale capacity) centered as nearly as possible at the center of 

each quadrant of the load-receiving element using the prescribed test pattern as shown in Figure 1.

(b) For scales with a nominal capacity greater than 500 kg (1000 lb), a shift test may be conducted by 

either using a one-third nominal capacity test load (defined as test weights in amounts of at least 

30 % of scale capacity, but not to exceed 35 % of scale capacity) centered as nearly as possible at 

the center of each quadrant of the load-receiving element using the prescribed test pattern as shown 

in Figure 1, or by using a one-quarter nominal capacity test load centered as nearly as possible, 

successively, over each corner of the load-receiving element using the prescribed test pattern as 

shown in Figure 2.

Figure 1 Figure 2

Position 

1

Position 

2 Position 

1

Position 

2

Position 

4

Position 

3 Position 

4

Position 

3

(Added 2003)

(Amended 1987, 2003, and 2007)

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. Sensitivity 

Requirement (SR) or T.N.6. Sensitivity.

N.1.5. Discrimination Test. – Except for digital electronic scales designated Accuracy Class I or II in which 

the value of e = d and is less than 5 mg, a discrimination test shall be conducted on all automatic indicating 

scales with the weighing device in equilibrium at or near zero load and at or near maximum test load, and under

controlled conditions in which environmental factors are reduced to the extent that they will not affect the results 

obtained. For scales equipped with an Automatic Zero-Tracking Mechanism (AZT), the discrimination test may 

be conducted at a range outside of the AZT range.

[Nonretroactive as of January 1, 1986]

(Added 1985) (Amended 2004 and 2021)
Handbook 44 – 2022 2.20. Scales

2-33

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

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. Abnormal Performance.)

N.1.10. Counting Feature Test. – A test of the counting function shall be conducted on all Class I and Class II 

prescription scales having an active counting feature used in “legal for trade” applications. The test should verify 

that the scale will not accept a sample with less than either the minimum sample piece count or the minimum 

sample weight of 30 e. Counting feature accuracy should be verified at a minimum of two test loads. Verification 

of the count calculations shall be based upon the weight indication of the test load.

Note:

(1) The minimum sample weight is equal to the marked minimum individual piece weight times the marked minimum sample 

piece count.

(2) Test load as used in this section refers to actual calibration test weights selected from an appropriate test weight class.

(Added 2003)

N.1.11. Substitution Test. – In the substitution test procedure, material or objects are substituted for known test 

weights, or a combination of known test weights and previously quantified material or objects, using the scale 

under test as a comparator. Additional test weights or other known test loads may be added to the known test 

load to evaluate higher weight ranges on the scale.

(Added 2003)

N.1.12. Strain-Load Test. – In the strain-load test procedure, an unknown quantity of material or objects are 

used to establish a reference load or tare to which test weights or substitution test loads are added.

(Added 2003)

N.2. Verification (Testing) Standards. – Field standard weights used in verifying weighing devices shall comply 

with requirements of NIST Handbook 105-Series standards (or other suitable and designated standards) or the 

tolerances expressed in Appendix A, Fundamental Considerations, paragraph 3.2. Tolerances for Standards (i.e., 

one-third of the smallest tolerance applied).

(Amended 1986)

N.3. Minimum Test Weights and Test Loads. – The minimum test weights and test loads for in-service tests 

(except railway track scales) are shown in Table 4. (Also see Footnote 2 in Table 4. Minimum Test Weights and Test 

Loads.)

(Added 1984) (Amended 1988)
2.20. Scales Handbook 44 – 2022

2-34

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

N.3.1. Minimum Test-Weight Load and Tests for Railway Track Scales.

(Amended 1990 and 2012)

N.3.1.1. Initial and Subsequent Tests. – 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) (Amended 2012)

N.3.1.2. Interim Test. – An Interim Test may be used to return a railway track scale into temporary service 

following repairs that could affect the accuracy of the weighing system providing all of the following 

conditions are met:

(a) a test weight load of not less than 13 500 kg (30 000 lb) shall be used;

(b) a shift (section) test shall be conducted using a test-weight load of not less than 13 500 kg 

(30 000 lb);

(c) a strain-load test shall be conducted up to at least 25 % of scale capacity;

(d) all test results shall be within applicable tolerances; and 

(e) the official with statutory authority shall be immediately notified when scales are repaired and 

placed in temporary service with an Interim Test. The length of temporary service following repair 

is at the discretion of the official with statutory authority.

(Added 1990) (Amended 2012)

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)
Handbook 44 – 2022 2.20. Scales

2-35

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

Table 4.

Minimum Test Weights and Test Loads1

Devices in Metric Units Devices in U.S. Customary Units

Device Capacity

(kg)

Minimums 

(in terms of device capacity) Device Capacity

(lb)

Minimums 

(in terms of device capacity)

Test Weights 

(greater of)

Test 

Loads2

Test Weights 

(greater of)

Test 

Loads2

0 to 150 kg 100 % 0 to 300 lb 100 %

151 to 1 500 kg 25 % or 150 kg 75 % 301 to 3 000 lb 25 % or 300 lb 75 %

1 501 to 20 000 kg 12.5 % or 500 kg 50 % 3001 to 40 000 lb 12.5 % or 1 000 lb 50 %

20 001 kg+ 12.5 % or 5 000 kg 25 %3 40 001 lb+ 12.5 % or 10 000 lb 25 %3

Where practicable:

• Test weights to dial face capacity, 1000 d, or test load to used capacity, if greater than minimums specified.

• During initial verification, a scale should be tested to capacity.

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 tolerances apply only to the test weights or substitution test loads.

(Amended 1988, 1989, 1994, and 2003)

Note: GIPSA requires devices subject to their inspection to be tested to at least “used capacity,” which is calculated 

based on the platform area of the scale and a weight factor assigned to the species of animal weighed on the scale. 

“Used capacity” is calculated using the formula:

Used Scale Capacity = Scale Platform Area × Species Weight Factor

Where species weight factor = 540 kg/m2 (110 lb/ft2) for cattle, 340 kg/m2 (70 lb/ft2) for calves and hogs, and 

240 kg/m2 (50 lb/ft2) for sheep and lambs.

N.3.2. Field Standard Weight Carts. – Field Standard Weight Carts that comply with the tolerances expressed 

in Appendix A, Fundamental Considerations, paragraph 3.2. Tolerances for Standards (i.e., one-third of the 

smallest tolerance applied) may be included as part of the minimum required test load (Also see Table 4. 

Minimum Test Weights and Test Loads.) for shift tests and other test procedures.

(Added 2004)
2.20. Scales Handbook 44 – 2022

2-36

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

N.4. Coupled-in-Motion Railroad Weighing Systems.

2

N.4.1. Weighing Systems Used to Weigh Trains of Less Than Ten 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 Ten 

or More Cars. – The minimum test train shall be a consecutive-car test train of no less than ten 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 

Ten or More Cars.

(a) These weighing systems shall be tested using a consecutive-car test train of no less than ten cars run over 

the scale a minimum of five times in each mode of operation following final calibration; or

(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 a:

(a) consecutive-car test train of a length typical of train(s) normally weighed; or

(b) 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. Initial Verification.

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 consecutivecar 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 %. If the difference in test 

results exceeds 0.15 %, the length of the shorter consecutive-car test train shall be increased until 

agreement within 0.15 % is achieved. Any adjustments to the weighing system based upon the use of a 

2 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)
Handbook 44 – 2022 2.20. Scales

2-37

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

shorter consecutive-car test train shall be offset to correct the bias that was observed between the fulllength 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 ten cars or 

10 % 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 ten cars.

(b) If the consecutive-car test train consists of between ten and twenty 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 twenty 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 one-half apothecary ounce, unless otherwise marked. (Applicable only to scales not marked with an accuracy

class.)
2.20. Scales Handbook 44 – 2022

2-38

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

N.7. Weigh-in-Motion Vehicle Scales Test Procedures.

N.7.1. Reference Scale. – A static scale as approved by the local jurisdiction shall be used to establish the 

weight of reference vehicles used in this procedure.

N.7.1.1. Dimension. – The reference scale shall be of such dimension and spacing as to weigh reference 

vehicles in a single draft.

N.7.1.2. Location. – The reference scale should be located near the weigh-in-motion vehicle scale to 

minimize the effect of vehicle fuel consumption. The reference scale and the weigh-in-motion vehicle scale 

may be the same scale.

N.7.1.3. Timing. – The reference scale shall be tested immediately prior to using it to establish reference 

vehicle weights. A subsequent test of the reference scale may be performed immediately following the 

establishment of the reference vehicle weights to ensure its repeatability.

N.7.1.4. Qualification. – The reference scale shall comply with the principles in Appendix A, 

Fundamental Considerations, Paragraph 3.2. Tolerances for Standards.

N.7.2. Reference Vehicle. – One or more reference vehicles shall be used to provide varying weight conditions 

for testing. Reference vehicles should be representative of vehicles that are customarily weighed on the weighin-motion vehicle scale during normal operation. A motorized field standard weight cart with tests weights and 

a driver may be used as an additional reference vehicle.

N.7.2.1. Weight Conditions. – Reference vehicle(s) shall be selected to provide at least a high and a low 

weight condition. Different types of vehicles may be used.

N.7.2.2. Load Position. – Loads on the reference vehicle should be positioned equally side-to-side.

N.7.2.3. Static Weight. – Reference vehicle(s) shall be statically weighed on a reference scale as defined 

in N.7.1 Reference Scale immediately before being used to conduct the weigh-in-motion vehicle scale tests.

N.7.2.3.1. Rounding. – Error weights may be added to the reference vehicle to increase its weight to 

a whole scale division to minimize rounding errors.

N.7.2.3.2. Re-Weighing. – Reference vehicles may be re-weighed at the discretion of the testing 

authority.

N.7.3. Test Speeds. – The speed of the reference vehicle shall be maintained within the parameters as specified 

by the manufacturer during each test (see also paragraphs S.1.14.1.(a) Identification of a Fault, Vehicle Speed

and S.1.14.1.(b) Identification of a Fault, Change in Vehicle Speed).

N.7.3.1. Range. – Various speeds of the reference vehicle shall be used between the minimum and 

maximum operating speeds specified for the weigh-in-motion vehicle scale. The minimum speed capability 

of the reference vehicle may be used as the minimum speed.

N.7.4. Static Tests for Weigh-in-Motion Vehicle Scales. – The weigh-in-motion vehicle scale shall comply 

with applicable vehicle scale tests defined in N.1. Test Procedures when tested statically.

N.7.5. Dynamic Tests for Weigh-in-Motion Vehicle Scales. – Test procedures shall simulate the normal 

intended use as closely as possible (i.e., test as used).

N.7.5.1. Vehicles. – The tests shall be performed using the reference vehicle(s) defined in N.7.2. Reference 

Vehicle.
Handbook 44 – 2022 2.20. Scales

2-39

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

N.7.5.2. Weighments. – Each reference vehicle shall have a minimum of five weighments at the speeds 

defined in N.7.3. Test Speeds.

N.7.5.3. Vehicle Position. – Reference vehicle(s) must stay within the defined roadway along the loadreceiving element (see also S.1.14.1.(e) Identification of a Fault, Vehicle Path of Travel).

N.7.5.4. Travel Directions. – The tests shall be performed in both directions of travel unless travel 

direction is restricted by the marking.

N.7.5.5. Results. – At the conclusion of the weigh-in-motion tests, there shall be a minimum of 10 total 

weight readings for the reference vehicle(s) for each applicable direction of travel. The tolerance for each 

weight reading shall be based on the gross vehicle weight and the applicable tolerance values for Class III L.

(Added 2021)

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. Tolerances for Unmarked Scales.

(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. Tolerances for Unmarked Scales and Table 5. Maintenance and Acceptance Tolerances for 

Unmarked Postal and Parcel Post Scales.

(Amended 1990)
(Table Added 1990) (Amended 1992, 1993, and 2012)

Table T.1.1. Tolerances for Unmarked Scales

Type of Device Subcategory Minimum 

Tolerance

Acceptance 

Tolerance

Maintenance 

Tolerance

Decreasing-Load

Multiplier1

Other Applicable 

Requirements

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

T.N.2., T.N.3., T.N.4.1., 

T.N.4.2., T.N.4.3., T.N.4.4., 

T.N.5., T.N.7.2., T.N.8.1.4.4

, 

T.N.9.

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 T.N.8.1.4.4

, T.N.9.

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 T.N.8.1.4.4

, T.N.9.

Monorail scales, in-motion T.N.3.8. 1.0 T.N.8.1.4.4, T.N.9.

Customer-operated bulk-weighing 

systems for recycled materials

± 5 % of applied material test load.

Average error on 10 or more test loads ≤ 2.5 %. 1.0 T.N.8.1.4.4

, T.N.9.

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 T.N.8.1.4.4

, T.N.9.

Prescription scales 0.1 grain (6 mg) 0.1 % of test load 0.1 % of test load 1.5 T.N.8.1.4.4, T.N.9.

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

T.N.8.1.4.4, T.N.9.

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 T.N.8.1.4.4

, T.N.9.

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 T.N.8.1.4.4

, T.N.9.

Loads ≤ 2 lb Table 5 Table 5 Table 5

Other postal and parcel post scales Table 5 Table 5 Table 5 1.5 T.N.8.1.4.4, T.N.9.

All other scales (including grain 

hopper)

n > 5000

0.5 d or 0.05 % of 

scale capacity,

whichever is less

0.05 % of test load 0.1 % of test load 1.5

T.N.2.5., T.N.4.1., T.N.4.2., 

T.N.4.3., T.N.5., T.N.7.2., 

T.N.8.1.4.4, T.N.9.

n ≤ 5000 Class III, T.N.3.1., Table 6 and T.N.3.2. 1.0

T.N.2., T.N.3., T.N.4.1., 

T.N.4.2., T.N.4.3., T.N.5., 

T.N.7.2., T.N.8.1.4.4, T.N.9.

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 

indication.

3 The decreasing load test does not apply to portable wheel load weighers. 4 T.N.8.1.4. Operating Temperature. is nonretroactive and effective for unmarked 

devices manufactured as of January 1, 1981.

2.20 Scales Handbook 44 - 2022

2-40
Handbook 44 – 2022 2.20. Scales

2-41

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

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. Prescription Scales through T.2.8. Railway 

Track Scales: 2 d, 0.2 % 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 % 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).

T.2.6. Grain Test Scales. – The sensitivity shall be as stated in T.N.6. Sensitivity.

(Amended 1987)

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 % of the scale capacity, whichever is less.

T.2.8. Railway Track Scales. – 3 d or 100 lb, whichever is less.

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

*Also see Table T.1.1. Tolerances for Unmarked Scales for scales designed and/or used to weigh loads less than 

2 lb.
2.20. Scales Handbook 44 – 2022

2-42

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

T.3. Sensitivity Requirement, Equilibrium Change Required. – The minimum change in equilibrium with test 

loads equal to the values specified in T.2. Sensitivity Requirements (SR) 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.N. Tolerances Applicable to Devices Marked I, II, III, III L, and 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 (zero net 

weight indication); the tolerance values apply to the net weight indication for any possible tare load using certified 

test loads.

(Amended 2008)

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. Testing with Nonassociated Equipment.)

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.
Handbook 44 – 2022 2.20. Scales

2-43

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

T.N.3. Tolerance Values.

T.N.3.1. Maintenance Tolerance Values. – The maintenance tolerance values are as specified in Table 6. 

Maintenance Tolerances.

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. Maintenance Tolerance Values and T.N.3.2. Acceptance Tolerance 

Values.

(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. Maintenance Tolerance Values and T.N.3.2. Acceptance Tolerance 

Values 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 % of the scale capacity, whichever is less.

(Amended 1986)

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 1 d 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 complete weighing device is submitted for laboratory type evaluation, the tolerance for 

the main element is 0.7 that for the complete weighing device. This fraction includes the tolerance attributable 

to the testing devices used.

(Amended 2015)

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 %.

(Amended 1990)
2.20. Scales Handbook 44 – 2022

2-44

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

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 % of the errors may exceed two times the static maintenance tolerance; and

(c) not more than 35 % 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. Maintenance Tolerances. On a dynamic test of twenty or more individual test loads, 

10 % 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 %. (Also see Note in N.1.3.5.1. Dynamic Monorail 

Weighing Systems.) For equipment undergoing type evaluation, a tolerance equal to one-half the maintenance 

tolerance values shown in Table 6. Maintenance Tolerances shall apply.

[Nonretroactive January 1, 2002]

(Added 1986) (Amended 1999 and 2001)

T.N.3.9. Materials Test on Customer-Operated Bulk Weighing Systems for Recycled Materials. – The 

maintenance and acceptance tolerance shall be ± 5 % of the applied materials test load except that the average 

error on ten or more test materials test loads shall not exceed ± 2.5 %.

(Added 1986)

T.N.3.10. Prescription Scales with a Counting Feature. – In addition to Table 6. Maintenance Tolerances (for 

weight), the indicated piece count value computed by a Class I or Class II prescription scale counting feature shall 

comply with the tolerances in Table T.N.3.10. Maintenance and Acceptance Tolerances in Excess and in 

Deficiency for Count.

Table T.N.3.10.

Maintenance and Acceptance Tolerances

in Excess and in Deficiency for Count

Indication of Count Tolerance

(piece count)

0 to 100 0

101 to 200 1

201 or more 0.5 %

(Added 2003)
Handbook 44 – 2022 2.20. Scales

2-45

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

T.N.3.11. Tolerances for Substitution Test. – Tolerances are applied to the scale based on the substitution test 

load.

(Added 2003)

T.N.3.12. Tolerances for Strain-Load Test. – Tolerances apply only to the test weights or substitution test 

loads.

(Added 2003)

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. – A time dependence test shall be conducted during type evaluation and may be 

conducted during field verification, provided test conditions remain constant.

(Amended 1989 and 2005)

T.N.4.5.1. Time Dependence: Class II, III, and IIII Non-Automatic Weighing Instruments. – A 

non-automatic weighing instrument of Classes II, III, and IIII shall meet the following requirements at 

constant test conditions. During type evaluation, this test shall be conducted at 20 °C ± 2 °C (68 °F ± 4 °F):

(a) When any load is kept on an instrument, the difference between the indication obtained immediately 

after placing the load and the indication observed during the following 30 minutes shall not exceed 

0.5 e. However, the difference between the indication obtained at 15 minutes and the indication 

obtained at 30 minutes shall not exceed 0.2 e.

(b) If the conditions in (a) are not met, the difference between the indication obtained immediately after 

placing the load on the instrument and the indication observed during the following four hours shall 

not exceed the absolute value of the maximum permissible error at the load applied.

(Added 2005) (Amended 2006 and 2010)
2.20. Scales Handbook 44 – 2022

2-46

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

T.N.4.5.2. Time Dependence: Class III L Non-Automatic Weighing Instruments. – A non-automatic 

weighing instrument of Class III L shall meet the following requirements:

(a) When any load is kept on an instrument, the difference between the indication obtained immediately 

after placing the load and the indication observed during the following 30 minutes shall not 

exceed 1.5 e. However, the difference between the indication obtained at 15 minutes and the 

indication obtained at 30 minutes shall not exceed 0.6 e.

(b) If the conditions in (a) are not met, the difference between the indication obtained immediately after 

placing the load on the instrument and the indication observed during the following four hours shall 

not exceed the absolute value of the maximum permissible error at the load applied.

(Added 2005) (Amended 2010)

T.N.4.5.3. Zero Load Return: Non-automatic Weighing Instruments. – A non-automatic weighing 

instrument shall meet the following requirements at constant test conditions. During type evaluation, this 

test shall be conducted at 20 °C ± 2 °C (68 °F ± 4 °F). The deviation on returning to zero as soon as the 

indication has stabilized, after the removal of any load which has remained on the instrument for 30 minutes 

shall not exceed:

(a) 0.5 e for Class II and IIII devices,

(b) 0.5 e for Class III devices with 4000 or fewer divisions,

(c) 0.83 e for Class III devices with more than 4000 divisions, or

(d) one-half of the absolute value of the applicable tolerance for the applied load for Class III L devices.

For a multi-interval instrument, the deviation shall not exceed 0.83 e1 (where e1 is the interval of the first 

weighing segment of the scale).

On a multiple range instrument, the deviation on returning to zero from Maxi (load in the applicable weighing 

range) shall not exceed 0.83 ei (interval of the weighing range). Furthermore, after returning to zero from 

any load greater than Max1 (capacity of the first weighing range) and immediately after switching to the 

lowest weighing range, the indication near zero shall not vary by more than e1 (interval of the first weighing 

range) during the following five minutes.

(Added 2010)

T.N.4.6. Time Dependence (Creep) for Load Cells during Type Evaluation. – A load cell (force transducer) 

marked with an accuracy class shall meet the following requirements at constant test conditions:

(a) Permissible Variations of Readings. – With a constant maximum load for the measuring range (Dmax) 

between 90 % and 100 % of maximum capacity (Emax), applied to the load cell, the difference between the 

initial reading and any reading obtained during the next 30 minutes shall not exceed the absolute value of 

the maximum permissible error (mpe) for the applied load. (Also see Table T.N.4.6. Maximum Permissible 

Error (mpe) for Load Cells During Type Evaluation.) The difference between the reading obtained at 

20 minutes and the reading obtained at 30 minutes shall not exceed 0.15 times the absolute value of the 

mpe. (Also see Table T.N.4.6. Maximum Permissible Error (mpe) for Load Cells During Type Evaluation)
Handbook 44 – 2022 2.20. Scales

2-47

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

(b) Apportionment Factors. – The mpe for creep shall be determined from Table T.N.4.6. Maximum 

Permissible Error (mpe) for Load Cells During Type Evaluation using the following apportionment 

factors (pLC):

pLC = 0.7 for load cells marked with S (single load cell applications),

pLC = 1.0 for load cells marked with M (multiple load cell applications), and

pLC = 0.5 for Class III L load cells marked with S or M.

(Added 2005, Amended 2006)

Table T.N.4.6.

Maximum Permissible Error (mpe)* for Load Cells During Type Evaluation

mpe in Load Cell Verifications Divisions (v) = pLC × Basic Tolerance in v

Class pLC × 0.5 v pLC × 1.0 v pLC × 1.5 v

I 0 - 50 000 v 50 001 v - 200 000 v 200 001 v +

II 0 - 5 000 v 5 001 v - 20 000 v 20 001 v +

III 0 - 500 v 501 v - 2 000 v 2 001 v +

IIII 0 - 50 v 51 v - 200 v 201 v +

III L 0 - 500 v 501 v - 1 000 v

(Add 0.5 v to the basic tolerance for each additional 

500 v or fraction thereof up to a maximum load of 

10 000 v)

v represents the load cell verification interval

pLC represents the apportionment factors applied to the basic tolerance

pLC = 0.7 for load cells marked with S (single load cell applications)

pLC = 1.0 for load cells marked with M (multiple load cell applications)

pLC = 0.5 for Class III L load cells marked with S or M

* mpe = pLC × Basic Tolerance in load cell verifications divisions (v)

(Table Added 2005) (Amended 2006)

T.N.4.7. Creep Recovery for Load Cells During Type Evaluation. – The difference between the initial 

reading of the minimum load of the measuring range (Dmin) and the reading after returning to minimum load 

subsequent to the maximum load (Dmax) having been applied for 30 minutes shall not exceed:

(a) 0.5 times the value of the load cell verification interval (0.5 v) for Class II and IIII load cells;

(b) 0.5 times the value of the load cell verification interval (0.5 v) for Class III load cells with 4000 or fewer 

divisions;

(c) 0.83 times the value of the load cell verification interval (0.83 v) for Class III load cells with more than 

4000 divisions; or

(d) 2.5 times the value of the load cell verification interval (2.5 v) for Class III L load cells.

(Added 2006) (Amended 2009 and 2011)

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.
2.20. Scales Handbook 44 – 2022

2-48

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

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 indicator, and 2 d or 0.2 % 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:

(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. (Also see N.1.5. Discrimination Test.)

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. (Also see N.1.5.1. Digital Device.)

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;

(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:
Handbook 44 – 2022 2.20. Scales

2-49

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

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. Temperature Range by Class.

Table T.N.8.1.2.

Temperature Range by Class

Class Temperature Range

I 5 oC (9 °F)

II 15 oC (27 °F)

III, III L, and IIII 30 oC (54 °F)

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. Tolerance Values through T.N.7. Discrimination, inclusive, when tested over 

the range of − 15 % to + 10 % of the marked nominal line voltage(s) at 60 Hz, or the voltage range 

marked by the manufacturer, at 60 Hz.

(Amended 2003)

(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
2.20. Scales Handbook 44 – 2022

2-50

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

(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. Radio Frequency Interference (RFI) and Other Electromagnetic Interference Susceptibility 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. 

(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.3

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. Typical Class or Type of Device for Weighing Applications.

(b) For devices not marked with a class designation, Table 7b. Applicable to Devices not Marked with a 

Class Designation applies.

Table 7a.

Typical Class or Type of Device for Weighing Applications

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 semiprecious gem weighing, grain-hopper scales, animal scales, postal scales, vehicle on-board weighing 

systems with a capacity less than or equal to 30 000 lb, and scales used to determine laundry charges

III L

Vehicle scales (including weigh-in-motion vehicle scales), vehicle on-board weighing systems with a 

capacity greater than 30 000 lb, axle-load scales, livestock scales, railway track scales, crane scales, 

and hopper (other than grain hopper) scales

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, 1995, 2012, and 2021)

3 Purchasers and users of scales such as railway track, hopper, and vehicle scalesshould be aware of possible additional 

requirements for the design and installation of such devices.

(Footnote Added 1995)
Handbook 44 – 2022 2.20. Scales

2-51

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

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 oz

Animal Scales 1 lb

Grain Hopper Scales

Capacity up to and including 50 000 lb

Capacity over 50 000 lb

10 lb (not greater than 0.05 % of capacity)

20 lb

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 lb

50 lb

Railway Track Scales

With weighbeam

Automatic indicating

20 lb

100 lb

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. – Hopper scales manufactured as of January 1, 1986, that are used to weigh 

grain shall be Class III and have a minimum of 2000 scale divisions.

(Amended 2012)

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 1985) (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.

(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)
2.20. Scales Handbook 44 – 2022

2-52

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

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. An in-motion railway track scale is not required to 

provide clearance using rail gaps to separate the live rail portion of the weighing/load-receiving element from that 

which is not live if the scale is designed to be installed and operated using continuous rail. 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]

(Amended 2014)

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 end(s) of a vehicle scale 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

(c) not less than 3 m (10 ft) of any approach adjacent to the platform shall be in the same plane as the 

platform. 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.

In addition to (a), (b), and (c), scales installed in any one location for a period of six months or more shall 

have not less than 3 m (10 ft) of any approach adjacent to the platform 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.

[Nonretroactive as of January 1, 1976]

(Amended 1977, 1983, 1993, 2006, and 2010)

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.
Handbook 44 – 2022 2.20. Scales

2-53

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

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.1.3.5.1. Dynamic 

Monorail Weighing Systems (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.2.10. Primary Indicating Elements Provided by the User. – Video display terminals and other userprovided indicating elements on scales interfaced with a cash register in a point-of-sale (POS) system shall 

comply with the minimum height requirements specified in part (c) of paragraph S.1.1.1. Digital Indicating 

Elements.

[Nonretroactive as of January 1, 2021]

(Added 2019)

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 Handbook 44 – 2022

2-54

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

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. Span Maximum Load.

(Added 1996)

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 Two 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.

* note and formula found at the end of the table.

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
Handbook 44 – 2022 2.20. Scales

2-55

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

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 Two or More Consecutive Axles.

2 axles 3 axles 4 axles 5 axles 6 axles 7 axles 8 axles 9 axles

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

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
2.20. Scales Handbook 44 – 2022

2-56

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

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 Two or More Consecutive Axles.

2 axles 3 axles 4 axles 5 axles 6 axles 7 axles 8 axles 9 axles

*Note: This table was developed based upon the following formula. Values may be rounded in some cases for ease of 

use.

 



 



  + + 

 





− = × 12 361

500 N

N

LN W r

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 ft are considered to be equivalent to 39 ft. This allows a weight of 68 000 lb on axles 2 through 5. 3 Corresponds to the Interstate Gross Weight Limit.

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, the weight of:

(a) 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) 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.
Handbook 44 – 2022 2.20. Scales

2-57

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

UR.3.5. Special Designs. – A scale designed and marked for a special application (such as a prepackaging 

scale or prescription scale with a counting feature) shall not be used for other than its intended purpose.

4

(Amended 2003)

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 or weighing refuse materials at landfills and transfer 

stations; and

(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, 1992, and 2006)

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 Weight Entries. – Manual gross or net weight entries are permitted for use in the 

following applications only when:

(a) a point-of-sale system interfaced with a scale is giving credit for a weighed item;

(b) an item is pre-weighed on a legal for trade scale and marked with the correct net weight;

(c) a device or system is generating labels for standard weight packages;

(d) postal scales or weight classifiers are generating manifests for packages to be picked up at a later time; 

or

(e) livestock and vehicle scale systems generate weight tickets to correct erroneous tickets.

(Added 1992) (Amended 2000 and 2004)

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)

4 Prepackaging scales and prescription scales with a counting feature (and other commercial devices) used for putting 

up packages in advance of sale are acceptable for use in commerce only if all appropriate provisions of NIST 

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.

(Amended 2003)
2.20. Scales Handbook 44 – 2022

2-58

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

UR.3.11. Minimum Count. – A prescription scale with an operational counting feature shall not be used to 

count a quantity of less than 30 pieces weighing a minimum of 90 e.

(Added 2003)

Note: The minimum count as defined in this paragraph refers to the use of the device in the filling of prescriptions and is 

different from the minimum sample piece count as defined in S.1.2.3. and as required to be marked on the scale by S.6.6.

(Note Added 2004)

UR.3.12. Correct Stored Piece Weight. – For prescription scales with a counting feature, the user is 

responsible for maintaining the correct stored piece weight. This is especially critical when a medicine has been 

reformulated or comes from different lots.

(Added 2003)

UR.3.13. Fault Indications for Weigh-in-Motion Vehicle Scales. – The fault conditions defined in S.1.14.1.

Identification of a Fault shall be presented to the customer and the operator in a clear and conspicuous manner.

(Added 2021)

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) 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. Weighing 

Systems Placed in Service Prior to January 1, 1991, and Used to Weigh Trains of Ten or More Cars and 

N.4.3.(a) Weighing Systems Placed in Service on or After January 1, 1991, and Used to Weigh Trains of Ten 

or More Cars, 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.

(b) For coupled-in-motion point-based weighing systems used only for dynamic weighing, the user shall provide 

an alternate certified scale to be used as a reference scale. The weights and measures authority having 

jurisdiction over the weighing system shall determine if the reference scale provided is suitable in terms of 

size, capacity, minimum division, performance requirements, and the proximity to the weighing system under 
Handbook 44 – 2022 2.20. Scales

2-59

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

evaluation. The reference weight cars weighed on the reference scale may then be used for calibration and 

annual inspection by the jurisdiction with statutory authority for the system.

(Added 1990) (Amended 1992 and 2021)
2.20. Scales Handbook 44 – 2022

2-60

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

THIS PAGE INTENTIONALLY LEFT BLANK
Handbook 44 – 2022 2.20. Scales

2-61

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

Scales Code Index

“

“r” factor........................................................................ 54

A

Acceptance................................................... 17, 41, 43, 44

Acceptance tolerance ................................... 17, 41, 43, 44

Accuracy.............16, 17, 19, 21, 23, 24, 25, 37, 39, 42, 50

Accuracy class ................16, 19, 21, 23, 24, 37, 39, 42, 50

Adjustable components............................................ 13, 19

Adjustment............................................. 13, 15, 19, 37, 58

Apportionment factor..................................................... 47

Approaches.................................................................... 52

Audit trail....................................................................... 13

Automatic zero-tracking mechanism ........... 15, 16, 20, 32

Axle-load scales................................. 7, 17, 18, 40, 48, 52

B

Balance condition .................................... 7, 15, 17, 49, 58

Balance indicator ......................... 7, 16, 17, 18, 41, 42, 48

Balance position............................................................. 10

Barometric pressure ................................................. 42, 49

C

Capacity .10, 11, 14, 15, 16, 17, 18, 19, 21, 22, 23, 24, 25, 

26, 28, 29, 30, 31, 34, 35, 37, 40, 41, 43, 48, 50, 51, 52, 

54, 58

Capacity indication ........................................................ 11

Center-of-zero.................................................................. 7

Certificate of Conformance............................................20

Class8, 9, 13, 15, 16, 18, 19, 21, 23, 24, 25, 29, 33, 40, 43, 

45, 46, 48, 49, 50, 51, 53

Class I 8, 13, 15, 16, 17, 18, 19, 21, 24, 25, 28, 39, 40, 41, 

42, 43, 48, 49, 50, 51, 53

Class II8, 15, 16, 18, 19, 21, 24, 25, 28, 39, 40, 41, 42, 43, 

45, 46, 48, 49, 50, 53

Class III9, 16, 19, 21, 24, 25, 28, 39, 40, 41, 42, 43, 45, 46, 

48, 49, 50, 51, 53

Class III L16, 19, 21, 24, 25, 39, 40, 41, 42, 43, 46, 48, 49, 

50, 51, 53

Class IIII9, 19, 21, 24, 25, 28, 39, 41, 42, 43, 45, 46, 48, 49, 

50, 53

CLC ................................................. 22, 23, 25, 26, 30, 54

Clearance ..................................................... 10, 16, 17, 52

Concentrated load capacity ............................................23

Consecutive-car test................................................. 36, 37

Counting feature .................... 9, 18, 25, 28, 33, 44, 57, 58

Crane and hopper........................................................... 43

Crane and hopper (other than grain hopper) ..................21

Creep........................................................................ 46, 47

D

Dairy-product test .................................. 16, 17, 29, 40, 41

Damping means................................................................17

Decreasing load test....................................................40, 42

Direct sales............................................... 10, 12, 15, 16, 18

Discrimination test............................................................32

Distributed-car test .....................................................36, 37

E

Electric power supply .......................................................49

Environmental factors.................................................32, 52

F

Field standard .............................................................33, 35

Foundation........................................................................52

G

Graduations ................................................ 9, 10, 11, 12, 16

Grain-test.................................................................... 16, 51

H

Hoists................................................................................53

I

Index of an indicator.....................................................9, 10

Indicating element ...7, 17, 22, 23, 24, 25, 27, 28, 43, 45, 52

Indicator...7, 9, 10, 11, 13, 16, 17, 18, 21, 24, 42, 45, 48, 58

Influence factors.........................................................42, 48

Information to be recorded ...............................................15

Initial verification ................................................. 35, 36, 37

Initial zero-setting mechanism....................................11, 16

Installation requirements ..................................................52

J

Jewelers' ...........................................................................41

L

Level................................................... 15, 17, 31, 52, 56, 58

Level condition..................................................... 17, 56, 58

Level-indicating means.....................................................17

Load cell........................... 19, 22, 23, 24, 25, 26, 46, 47, 52

Load cell verification interval............................... 19, 26, 47

M

Main elements ............................................................22, 43

Maintenance ...........................40, 41, 43, 44, 45, 47, 52, 58

Maintenance requirements................................................58

Maintenance tolerance........................ 40, 41, 43, 44, 45, 47

Manual weight entries ................................................14, 57

Marking requirements.................................................22, 23

Material test................................................................33, 40
2.20. Scales Handbook 44 – 2022

2-62

This publication is available free of charge from: https://doi.org/10.6028/NIST.HB.44-2022

Maximum permissible error (mpe)............................. 46, 47

Minimum load ............................................................ 53, 57

Minimum test weights................................................ 33, 35

Money-value computation................................................ 12

Money-value graduations........................................... 11, 12

Multi-interval.................................................. 19, 21, 24, 42

Multiple range ............................................................ 19, 42

N

No-load reference value......................................................8

Nominal capacity...10, 22, 23, 24, 25, 26, 28, 30, 37, 42, 54

Non-automatic ............................................................ 45, 46

O

On-board......................................................... 14, 17, 31, 50

Operating temperature ...................................................... 49

P

Parallax............................................................................. 10

Piece ....................................................................... 9, 44, 58

Point-of-sale ............................................................... 12, 57

Poise ........................................................................... 10, 11

Portable axle-load weighers........................ 7, 32, 43, 50, 56

Power interruption............................................................ 49

Prescription16, 17, 18, 21, 25, 28, 33, 37, 40, 41, 44, 57, 58

R

Ratio test..................................................................... 33, 42

Readability ....................................................................... 10

Recorded representations.................................................. 12

Recording elements................................................ 7, 17, 45

Repeatability..................................................................... 47

RFI........................................................................ 33, 49, 52

S

Scale modification............................................................ 58

Scales

Automatic indicating ........................................ 28, 32, 40

Axle load..................................................... 25, 29, 50, 51

Belt-conveyor................................................................. 7

Computing.............................................................. 11, 12

Crane...................................................................... 32, 51

Dairy-product test............................................ 17, 29, 41

Gem weighing .............................................................. 50

Grain test ............................................................... 40, 50

Hanging .................................................................. 32, 52

Hopper ....................................................... 32, 43, 50, 51

Jewelers’ .......................................................... 17, 40, 41

Livestock.15, 16, 18, 22, 25, 26, 28, 29, 30, 48, 50, 52, 57

Monorail............................................. 8, 9, 16, 17, 31, 40

Parcel post........................................................39, 40, 41

Postal ....................................8, 11, 25, 39, 40, 41, 50, 57

Prepackaging.......................................................... 13, 57

Prescription.......................................... 17, 33, 40, 44, 58

Railway track .....16, 18, 25, 26, 31, 33, 34, 40, 41, 50, 51

Vehicle .15, 18, 22, 25, 26, 29, 30, 38, 48, 50, 52, 53, 54, 

........................................................................... 57, 58

Weighbeam.................................................................. 10

Sealing........................................................................ 13, 14

Security seal .....................................................................13

Sensitivity requirement...............................................41, 42

Sensitivity test ..................................................................32

Shift test.......................................................... 29, 31, 35, 45

Single-draft.......................................................................56

Stock racks .......................................................................53

Strain-load test...................................................... 33, 34, 45

Subsequent verification ........................................ 36, 37, 42

Substitution........................................................... 33, 35, 45

Supports...................................................................... 28, 52

Symmetry ...........................................................................9

T

Tare................................................................. 15, 16, 17, 42

Temperature........................................ 20, 23, 24, 42, 48, 49

Test loads................................ 28, 29, 31, 33, 35, 40, 42, 44

Test pattern ................................................................. 29, 30

Time dependence..............................................................45

Tolerances .16, 18, 33, 35, 39, 40, 41, 42, 43, 45, 47, 50, 57

Travel ................................................................... 10, 18, 37

Type evaluation ............................ 22, 42, 43, 44, 45, 46, 47

U

Unit prices .................................................................. 11, 12

Unit weights ......................................................... 11, 25, 45

Use requirements..............................................................53

V

Vehicle on-board weighing system................. 14, 17, 31, 50

Verification scale interval.............................................8, 19

W

Weighbeam.......................................................................10

Weighing elements......................................... 19, 30, 31, 52

Weighing systems

Coupled-in-motion ........................................... 36, 43, 58

Uncoupled-in-motion................................................... 37

Weight classifier....................................... 11, 12, 25, 53, 57

Weight ranges.............................................................11, 25

Weight units .......................................................................8

Wheel-load weighers............................ 7, 17, 32, 43, 51, 56

Z

Zero indication..............................................................7, 49

Zero-load adjustment..................................................15, 58

Zero-load balance ......................... 13, 15, 16, 17, 33, 49, 58

Zero-tracking mechanism....... See Automatic zero-tracking 

mechanism