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Changes to the International Vo‐

bulary of Metrology and 

Proposed Changes to Some De‐

finitions in the Uniform Weights

and Measures  Law in NIST Hand

book 130 1

Calendar 2

This Month in 

History

Happy Birthday America!

July 4, 1776 ‐ Declaration of Independence

was approved by the Continental Congress.

July 7, 1898 ‐ President William McKinley

signed a resolution to annex Hawaii. Con‐

gress made it a territory in 1900, and it re‐

mained a territory until it gained statehood

in 1959.

July 11, 1767‐ John Quincy Adams (1767 ‐

1848), the 6th President of the United States,

was born in Braintree, Massachusetts. He

was the son of the 2nd president, John

Adams. 

July 18, 1947 ‐ President Harry S. Truman

signed an Executive Order that provides the

line of succession if the president should be‐

come unable to perform the duties of the of‐

fice or should die in office. This became the

25th Amendment to the Constitution. The

line of succession is Vice President, Speaker

of the House, and President of the Senate.

July 20, 1969 ‐ Apollo 11 Astronaut Neil Arm‐

strong took his first step on the moon. His fa‐

mous line, “That’s one step for man, one

giant leap for mankind,” is known my many.

1

Volume 3 Issue 4

July 9, 2012

Changes to the International

Vocabulary of Metrology

PROPOSED CHANGES TO SOME DEFINITIONS IN THE UNIFORM WEIGHTS

AND MEASURES LAW IN NIST HANDBOOK 130 

by: Chuck Ehrlich

This article has been written to provide some background information on the

development of the International vocabulary of basic and general terms in

metrology (VIM) documents over the past several years, and to provide some

explanation and elaboration on several of the definitions in the International

vocabulary of metrology ― Basic and general concepts and associated terms

(VIM), 3rd edition, also known as the “VIM3.” Some of the terms from VIM3

have been proposed for inclusion by the National Institute of Standards and

Technology (NIST) Office of Weights and Measures (OWM) in the National

Conference on Weights and Measures (NCWM Publication 16, Laws and Reg‐

ulations Committee agenda Item 221‐1). The purpose of the proposal is to

incorporate the VIM3 definitions into the Uniform Weights and Measures

Law (UWML) in Handbook 130 (HB 130), Uniform Laws and Regulations in

the Areas of Legal Metrology and Engine Fuel Quality, updating the VIM2 def‐

initions it contains. Incorporating these updated definitions will better align

the HB 130 definitions with the philosophy of the Guide to the expression of

uncertainty in measurement, commonly referred to as the “GUM,” which

serves as a key document underpinning requirements for the accreditation

of state metrology laboratories. Incorporating these updated definitions will

also better reflect current international agreement on metrology‐related ter‐

minology. 

In order to promote having a “common language of metrology” at the inter‐

national level, in 1984 a small group of people representing the International

Bureau of Weights and Measures (BIPM), the International Organization of

Legal Metrology (OIML), the International Standardization Organization (ISO),

and the International Electrotechnical Commission (IEC) developed the first

edition of the “VIM.” ISO published the document on behalf of the four or‐

ganizations.

In 1993, the second edition of the VIM (also known as the “VIM2”) was pub‐

lished, with three additional cosponsoring organizations: the International

Federation of Clinical Chemistry (IFCC), the International Union of Pure and

Applied Chemistry (IUPAC), and the International Union of Pure and Applied

Physics (IUPAP). The second edition was developed in order to “remove some

anomalies, ambiguities and circularities1

” from the first edition, and to better

address some of the needs of chemistry and other related fields. Further, it

incorporated terminology associated with the GUM, which was also published

(again by ISO) that same year.
Calendar 2012

Registration for training in the NIST Office of

Weights and Measures is handled by Yvonne

Branden at yvonne.branden@nist.gov.

Course descriptions can be viewed on the Office of

Weights and Measures website by clicking on the

name of the course. 

http://www.nist.gov/pml/wmd/calendar.cfm

July 15 ‐ 19

National Conference on Weights and Measures

(NCWM) Annual Meeting

Portland, ME

Contact: info@ncwm.net

July 29 ‐ August 2

NCSLI Conference & Symposium 

Metrology and Testing ‐ The Business End of

Metrology

Sacramento, CA

Contact: NCSLI at http://www.ncsli.org/

August 9 (2 hours)

Webinar ‐ Calibration Report Evaluations

Class No. 5175

August 16 (2 hours)

Webinar ‐ Contract Review

Class No. 5176

August 20 ‐ 24 (5 days)

Fundamentals of Metrology

Class No. 5179

NIST

Gaithersburg, MD

August 23 (2 hours)

Webinar ‐ Document Control and Recordkeeping

Class No. 5177

August 30 (2 hours)

Webinar ‐ Proficiency Testing Follow Up Actions and

Root Cause Analysis

Class No. 5181

September 6 (2 hours)

Webinar ‐ Conducting an Effective Management

Review

Class No. 5178

September 10 ‐ 13

Central Weights and Measures Association

(CWMA) Interim Meeting

Bettendorf, IA

Contact: Vicky Dempsey at

dempseyv@mcohio.org

(continued on page 3)

W&M Connection 2 Volume 3 Issue 4

In 2005 the National Conference on Weights and Measures (NCWM) adopted

several of the definitions from the VIM2 into the UWML in NIST HB 130. The

definitions were adopted almost verbatim, with some small changes to ac‐

commodate the HB 130 format for definitions. Among the VIM2 definitions

added to HB 130 were those for “calibration”, “traceability,”“uncertainty,”

“reference standard,” and “working standard.”

The VIM3 was published by the Joint Committee for Guides in Metrology

(JCGM) in 2008, and was subsequently published with corrections in early

2012. The JCGM, established in 1997 by the seven cosponsoring organizations

mentioned above, and joined in 2005 by the International Laboratory Accred‐

itation Cooperation (ILAC), now has assumed oversight responsibility from

ISO for both the VIM and the GUM. Development of the VIM3 was motivated

in part by the desire to further address measurements in chemistry and lab‐

oratory medicine, and to incorporate additional concepts related to meas‐

urement uncertainty, metrological traceability, and nominal properties. A set

of concept diagrams was added to the VIM3 that demonstrates the relation‐

ships among the various concepts contained in the VIM3 definitions.

The VIM3 is somewhat more formal than the VIM2 in its use of language. This

was done primarily in order to reduce the possibility of ambiguity, while main‐

taining the efficiency of use of words and rigor of the concept system. While

some readers have found the VIM3 to be equally or more useful than the two

earlier versions, others have found its style of language and level of complex‐

ity to be too different than that in the earlier versions, leading to difficulty in

following the language in some of the definitions.

The first definition in the UWML proposed to be updated is “calibration.” 

Historically, a calibration has been defined (such as in the VIM2) as a “process

of comparing and recording indicated values obtained from a measuring in‐

strument with the corresponding values obtained when using measurement

standards.” For example, when calibrating a mercury‐in‐glass thermometer,

the indicated value from viewing the thermometer can be compared with the

value obtained from a precision thermocouple that is in the same tempera‐

ture bath as the thermometer. This can be done over a range of discrete tem‐

peratures of the bath, and a calibration table can be developed that records

indicated values from the thermometer and corresponding values obtained

from the thermocouple at each discrete temperature (e.g., 4.4 °C (40 °F),

10 °C (50 °F), 43.3 °C (110 °F), and 48.8 °C (120 °F).

The revised definition of “calibration” in the VIM3 recognizes that the VIM2

(and the current UWML) definition is missing two things. First, nothing is said

about recording the measurement uncertainties associated with any of the

values in a calibration table. Second, nothing is said about how the informa‐

tion in a calibration table is to be when the mercury‐in‐glass thermometer is

subsequently used to measure the temperature of something (for example,

the body temperature of a patient). While a calibration table typically has in‐

formation at a few discrete points, the calibration report accompanying a cal‐

ibration certificate typically gives either a “fit to a curve” (chart, graph or

diagram), or a computer‐generated table based on such a curve fit, along with

the appropriate measurement uncertainty to associate with any indicated

value of the thermometer over the range of the calibration. By incorporating

the VIM3 definition of “calibration” into the UWML, these missing aspects of

the definition will then be included.

The second definition in the UWML that is proposed to be updated is “(metro‐

logical) traceability”. 
September 10 ‐ 13

NEMAP*

Class No. 5154

Portland, ME

Contact: Danny Newcombe at

Danny.Newcombe@maine.gov

September 13 (2 hours)

Webinar ‐ Internal Auditing Best Practices

Class No. 5182

September 16 ‐ 20

Western Weights and Measures Association

(WWMA)

Breckenridge, CO

Contact: Mahesh Albuquerque at

mahesh.albuquerque@state.co.us

September 24 ‐ 27

SWAP*

Class No. 5126

Baton Rouge, LA

Contact: Richert Williams at

richer_w@ldaf.state.la.us

October 1 ‐ 5

47thCIML Meeting, 14thOIML Conference

Bucharest, Romania

Contact: Charles Ehrlich at

Charles.Ehrlich@nist.gov

October 7 ‐ 10

Southern Weights and Measures Association

(SWMA)

Louisville, KY

Contact: Jason Glass at (502) 573‐0282

jason.glass@ky.gov

October 15 ‐ 18

MidMAP*

Class No. 5155

Sioux Falls, SD

Contact: Brad Stover at

brad.stover@state.sd.us

October 15 ‐ 26 (2 week)

Mass Metrology Seminar 

Class No. 5192

October 16 ‐ 17

Northeastern Weights and Measures Association

(NEWMA) Interim Meeting 

TBD

Contact: James Cassidy at

jcassidy@cambridgema.gov

October 18 (2 hours)

Webinar ‐ State Laboratory Annual Submission

Process**

Class No. 5190

(continued on page 4)

W&M Connection 3 Volume 3 Issue 4

The term “metrological” is added to distinguish this type of traceability from

other types of traceability (e.g., document traceability). Probably the most

significant aspect of the updated (VIM3) definition is that traceability is now

explicitly considered to apply to both values and uncertainties, rather than

just to values. This is an important addition, since it reflects the growing in‐

ternational agreement that a statement of traceability that does not include

information about measurement uncertainty is of limited value, since no one

then really knows how good the measured value is thought to be.

Other changes to the updated definition of “traceability” are that the unbro‐

ken chain is a chain of calibrations (rather than a chain of comparisons), and

that the chain must be documented. The reason that the chain is a chain of

calibrations (and not comparisons) is that calibrations transfer values and un‐

certainties along the chain, whereas comparisons alone do not do that. 

A new definition from the VIM3 that is proposed to be added to the UWML

is “metrological traceability chain,” which is intended to further support the

updated definition of “traceability” by explaining what is meant in the defi‐

nition by “chain.”

Another aspect of the updated definition of “traceability” is that it recognizes

that references for traceability do not have to be national or international

standards. Rather, any well‐characterized reference standard can be used.

For example, one can talk about a measurement result obtained “in the field”

being traceable to a reference standard in a state metrology laboratory.

Usually, however, it is important that traceability eventually lead back to in‐

ternationally agreed reference standards, such as the measurement units of

the International System of Units (SI). Therefore, a new definition from the

VIM3 (for “metrological traceability to a measurement unit”) is being pro‐

posed to be added to the UWML to help clarify what is meant by “traceability

to the SI.” For example, “(metrological) traceability to the SI” means metro‐

logical traceability to the definition of the measurement unit “kilogram” (kg)

through the practical realization of the kg at NIST, obtained by calibration of

a NIST mass artifact, having a mass of about 1 kg, against the international

kilogram in Paris.

The third definition in the UWML that is proposed to be updated is “mea‐

surement uncertainty.” 

The VIM3 definition clarifies that measurement uncertainty can only be pos‐

itive (or zero), and, more importantly, the definition eliminates the subjective

term “reasonably” that appears in the VIM2 (and UWML) definition. The up‐

dated definition also clarifies that measurement uncertainty characterizes a

dispersion or range of values believed to contain the true value of the quan‐

tity intended to be measured (the measurand).

Two additional definitions in the UWML that are proposed to be updated are

“reference measurement standard” and “working measurement standard.” 

The revision of “reference measurement standard” will update the current

UWML definition in two ways. First, it would no longer be required that a ref‐

erence measurement standard be of the highest quality available (for example,

it could be lower in a metrological traceability chain). Second, it is specified

that a reference measurement standard is intended to be used for calibration

of other measurement standards and not for making routine measurements,

such as working measurement standards are. The term “measurement” was

added to the term in order to distinguish this type of reference standard from

other types, such as a reference documentary standard. 
W&M Connection 4 Volume 3 Issue 4

November 1 (2 hours)

Webinar ‐ State Laboratory Annual Submission

Process **

Class No. 5191

November 5 ‐ 9 (1 week)

Volume Seminar

Class No. 5193

December 3 ‐ 7 (1 week)

Intermediate Metrology Seminar

Class No. 5164

2013

January 27 ‐ 30 

National Conference on Weights and Measures

(NCWM) Interim Meeting

Francis Marion Hotel

Charleston, SC

Contact: info@ncwm.net

January 28 ‐ February 1 (5 days)

Fundamentals of Metrology

Class No. 5206

February 4 ‐ 7 (4 days)

Advanced Mass Seminar

Class No. 5204

February 11 ‐ 14 (4 days)

Advanced Mass Hands‐On Seminar

Class No. 5205

March 4 ‐ 15 (2 weeks)

Mass Metrology Seminar

Class No. 5207

March 25 ‐ 29 (5 days)

Packaging and Labeling Seminar

Class No. 5224

April 8 ‐ 11

SEMAP*

Class No. 5209

Tifton, GA

April 15 ‐ 19 (5 days)

Fundamentals of Metrology

Course No. 5208

May 6 ‐ 9

WRAP*

Class No. 5216

Helena, MT

May 13 ‐ 24 (2 weeks)

Mass Metrology Seminar

Class No. 5217

*Invitation Only

**Limited to State Laboratory Program Partici‐

pants

The revision of “working measurement standard” will also update the current

UWML definition in two ways. First, a working standard would no longer be

required to be directly calibrated by a reference standard (it could, for exam‐

ple, calibrated by another working standard). Also, this revision will clarify

that a working standard can be used for both calibration and verification of

measuring instruments. The word “measurement” was again added in order

to distinguish this type of standard from other types of working standards.

By updating both of these definitions, the UWML will reflect current interna‐

tional agreement about measurement standards that is consistent with the

VIM3.

The explanations given above cover the proposed VIM3 updates of definitions

in the UWML. For those interested in other entries in the VIM3, a set of fre‐

quently asked questions (FAQs) on the VIM3 is being developed by the group

responsible for its creation, in order to address some of the expressed com‐

plexity and difficulties with understanding some of the definitions. The initial

set of finalized FAQs is anticipated to be available online later this summer at

http://www.bipm.org/en/publications/guides/vim.html. It is anticipated that

the FAQs will be a living document, with possible improvements and new en‐

tries as time progresses.

ENDNOTE

1 ”Circularity” here means defining one word in terms of another that is itself

defined in terms of the first word.

2012 NCWM 

ANNUAL MEETING

JULY 14 ‐ 19 2012

PORTLAND, MAINE

Registration Information is available at: 

URL: http://www.ncwm.net/content/2012‐ncwm‐annual‐meeting

Checkout the OWM Web Calendar 

for Training and Meeting Events

at

URL: http://www.nist.gov/pml/wmd/calendar.cfm