Inside this Issue

Page

Field Standards for Weights and 

Measures 1

Calendar 3

This Month in 

History

April 2, 1513 ‐ Spanish explorer Ponce De

Leon discovered Florida and claimed it for

Spain. He came ashore in what is now known

as St. Augustine, which is the oldest city in

the United States.

April 4, 1887 ‐ On this day, the first woman

mayor was elected in the United States. Ms.

Susanna Salter was elected mayor of Argonia,

Kansas.

April 13, 1743 ‐ Thomas Jefferson’s birthday

(1743 ‐ 1826). He was a native of Virginia and

a respected author, inventor, lawyer, politi‐

can, architect, and considered one of the

finest minds of the 1700s. 

April 19, 1775 ‐ The historic “shot heard

around the world” occured on this day at Lex‐

ington Green, Massachusetts. This event

began the American Revolution.

April 22, 1864 ‐ On this day, established by

an Act of of Congress “In God We Trust” was

added to all newly minted U.S. coins. 

April 24, 1880 ‐ The Library of Congress was

established in Washington, DC.

1

Volume 4 Issue 2

April 1, 2013

Field Standards for

Weights and Measures

Byline: Georgia L. Harris

A number of questions and issues have recently been raised that caused me

to pause – and think – about field standards related to the entire weights and

measures system. Normally, I would focus on just the laboratory applications

and considerations, but I think it’s time for some integrated thinking about

field standards, their acceptance, and use. A number of key questions are

presented here related to manufacturing, calibration, and use of field stan‐

dards, such as: Are the field standards “fit for purpose”? Do the field stan‐

dards comply with a documentary standard or other specifications and

tolerances? What legal authority and responsibility do jurisdictions have re‐

garding choice and purchase of field standards, compliance, metrological

traceability, and acceptance of assessments or calibration reports? What

should laboratories provide “the customer”?

Fit for Purpose

One of the big questions that should be asked in the measurement commu‐

nity is whether [field] standards are “fit for purpose”. The concept of fit for

purpose is common in method validation practices to ensure that adequate

quality and suitability is designed into procedures. The concept can also be

applied to field standards. Two quick examples might be: Class F field stan‐

dard weights (NIST Handbook 105‐1, Specifications and Tolerances for Field

Standard Weights) are not suitable for evaluating a Class II weighing device

(balance). They are not fit for purpose. Small Volume Provers (NIST Handbook

105‐7, Specifications and Tolerances for Dynamic Small Volume Provers) are

not suitable for evaluating Liquid Petroleum Gas (LPG) meters. They are not

fit for purpose. While these statements could be debated, if one reviews the

calibration uncertainty and tolerances for the field standards, it will quickly

become obvious that Class F weights will not meet the Fundamental Consid‐

erations for evaluating a Class II device. The Fundamental Considerations re‐

quire that the uncertainties in the standards be less than one third of the

applicable tolerances. The tolerances on the mass standards are just too big.

One could also argue that Small Volume Provers could be used for LPG me‐

ters; however, during the initial evaluation and development of the NIST

Handbook 105‐7, there was NO data collected or evaluated that demon‐

strated that Small Volume Provers could successfully be used to evaluate LPG

meters. Thus, data are required to demonstrate suitability.

An additional question that might be asked in this section is whether the field

standard allows for replication of the use of the weighing or measuring in‐

strument. An example here is whether or not it is suitable to remove the

nozzle from a retail motor fuel dispenser to evaluate a meter – and whether
W&M Connection 2 Volume 4 Issue 2

there are sufficient steps in the evaluation process to ensure that the verification of the device complies with NIST Handbook

44, Specifications, Tolerances, and Other Technical Requirements for Weighing and Measuring Devices, and is fit for purpose

(i.e., for consumers to use a meter tested this way to fill their vehicles with adequate accuracy). This entire concept goes

back to an article I wrote in June 2005 on the Calibration of Rocks (http://www.nist.gov/pml/wmd/labmetrology/upload/h‐

006.pdf). A laboratory can provide a perfectly valid mass value and uncertainty for a rock, but that does not mean the rock

is suitable for use as a mass standard in testing a scale. 

Compliance Assessments 

A common practice among calibration laboratories is to evaluate compliance of the measurement result and the uncer‐

tainties against published tolerances only. In fact, many calibration certificates say something along the lines of “the meas‐

urement results comply with the tolerances of XYZ Handbook.” A key aspect of this practice to consider is that the calibration

uncertainties must always be smaller than the applicable field standard tolerances to claim any level of compliance. If a

situation occurs such as is shown in Figure 1, in Case A, the measurement uncertainty is bigger than the tolerance and a

statement of compliance cannot be made with the usual confidence, in spite of the value being at nominal! In Case B or

Case C, there is doubt about the measurement result – which is why most metrologists will also adjust a field standard and

you may see “as found” and “as left” calibration results reported on a calibration certificate. 

What is also critical for weights and measures officials to know is that many laboratories do NOT evaluate field standards for

compliance to all of the specifications in a documentary standard. It is important to make sure you know this when covering

any of the subsequent sections in this article! For example, cast iron 1 lb weights are manufactured, used by service com‐

panies, and calibrated by laboratories – yet they do

not comply with NIST Handbook 105‐1 for field stan‐

dard weights because of the material requirements

for weights between 0.01 lb – 10 lb (5 g – 5 kg). A

volumetric prover or LPG prover may or may not be

evaluated against NIST Handbook 105‐3, Specifica‐

tions and Tolerances for Graduated Neck Type Vol‐

umetric Field Standards, or 105‐4, Specifications and

Tolerances for Liquefied Petroleum Gas and Anhy‐

drous Ammonia Liquid Volumentric Provers, even if

new and just being put into service – unless the

evaluation was requested. 

Weights and measures jurisdictions may require

compliance to NIST Handbook 105‐series stan‐

dards, or an ASTM standard (e.g., proving rings

used for wheel load weigher testing), or OIML

R 120 for volumetric standards. It is important to

specifically request an evaluation of compliance to

a standard for a weights and measures program

when evaluating the standards field staff use, when designating suitable field standards for service companies, or when

accepting calibration reports from other calibration laboratories. NIST recommends full compliance evaluations whenever

possible – yet, we have no regulatory authority to ensure that laboratories perform this function. It is up to the jurisdiction

to mandate compliance evaluations. ISO/IEC 17025, Section 5.10.4.2 indicates that when compliance statements are in‐

cluded on a calibration report, they must specifically include what was or was not assessed: “If a statement of compliance

with a specification is made, this shall identify which clauses of the specification are met or not met.” So, if a field standard

was only evaluated for measurement results to tolerances, the report should specifically state that “no evaluation for com‐

pliance against the specifications was made” in addition to “all standards were found/left in tolerance according to this

handbook.” An example here might be a volumetric prover made from aluminum. Aluminum is not allowed according to

NIST Handbook 105‐3 due to the excessively large cubical coefficient of expansion. Yet, a laboratory could perform a valid

calibration and find the prover in tolerance and produce an acceptable calibration certificate, as long as the report indicated

no evaluation was done. In this case, not only would the prover NOT comply with the standard, it would also not be fit for

purpose. 

There is an ongoing challenge when no documentary standard exists that includes both specifications and tolerances. In

the scheme of the NIST Handbook 105‐series standards, Handbook 105‐8, Specifications and Tolerances for Field Standard

Weight Carts, for weight carts used to evaluate scales, is relatively new. Prior to this handbook being published, there were

many weight carts already in use throughout the country by both weights and measures jurisdictions as well as by service

Figure 1. Example Values, Uncertainties and Tolerances.
W&M Connection 3 Volume 4 Issue 2

Calendar 2013

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 Of‐

fice of Weights and Measures website by

clicking on the name of the course. 

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

April 8 ‐ 11 (4 days)

SEMAP*

Class No. 5209

Tifton, GA

April 9 ‐ 11 (3 days)

Packaging and Labeling Seminar

Class No. 5224

NIST/Gaithersburg, MD

April 15 ‐ 19 (5 days)

Fundamentals of Metrology

Class No. 5208

NIST/Gaithersburg, MD

April 22 ‐ 26 (5 days)

Vehicle‐Tank and Loading‐Rack Meters

Class No. 5268 

Olympia, WA

April 23 ‐ 25 (3 days)

Grain Moisture Meter Technical Training

Class No. 5264

Kansas City, MO

April 25

Conducting an Effective Management Review

Webinar, 2:00 p.m. to 4:00 p.m.

Class No. 5253

May 2

Internal Auditing Best Practices 

Webinar, 2:00 p.m. ‐ 4:00 p.m.

Class No. 5234

May 6 ‐ 10 (5 days)

WRAP*

Class No. 5216 , Helena, MT 

May 6 ‐ 9 (4 days)

Northeast Weights and Measures Association

(NEWMA)

Saratoga Springs, NY 

Contact: James Cassidy at jcassidy@cam‐

bridgema.gov

May 13 ‐ 24 (2 weeks)

Mass Metrology Seminar 

Class No. 5217

NIST/Gaithersburg, MD

May 20 ‐ 23

Central Weights and Measures Association

(CWMA)

Overland Park, KS

(con’d pg 4)

companies. No one was able to assess weight carts for compliance, because

no standard existed. 

Legal Responsibilities 

Most jurisdictions in the United States have adopted into law language similar

to the model laws provided in NIST Handbook 130, Uniform Laws and Regu‐

lations in the Areas of Metrology and Engine Fuel Quality. In the current ver‐

sion (in fact going back to 2005 when some key changes were adopted), the

model law and the registered service persons program designate some key

responsibilities and authorities to the weights and measures director. The

director has the authority to accept calibration reports from other calibration

laboratories and retains the right to inspect and evaluate the standards that

will be used. This right is especially critical if the laboratory performing the

calibration did not evaluate the field standards for compliance to a documen‐

tary standard that is required in your jurisdiction. When a calibration report

is submitted which states that the standards were not evaluated for compli‐

ance, a weights and measures jurisdiction should conduct an inspection or

evaluation of the field standard when specific documentary standards are re‐

quired. 

The model laws also allow for specific calibration intervals or variable cali‐

bration intervals based on statistical analysis of stability of the standards. Ac‐

cording to ISO/IEC 17025 for the laboratories, no calibration intervals are to

be included on a calibration certificate unless requested by the customer or

unless there is a legal requirement. Service companies may not be aware of

legally required calibration intervals when requesting calibration services, so

it is a good idea for laboratories to ask customers where or how they intend

to use the standards and if there are required calibration intervals. We have

previously published some baseline calibration intervals for a variety of field

standards, where local authority allows for variable intervals based on data.

See: http://www.nist.gov/pml/wmd/labmetrology/upload/h‐009.pdf. 

Supplier Evaluations – Calibration Laboratories

When accepting calibration certificates from a laboratory, there are some

concepts from the ISO/IEC 17025 standard (as applied to calibration labora‐

tories through recognition and/or accreditation), that are useful. Compliance

with ISO/IEC 17025 requires assessment of the evidence for metrological

traceability of the measurement results. This is also defined in NIST Hand‐

book 143, Weights and Meaures Laboratories Program Handbook, Program

Handbook for Laboratory Recognition, and in NIST Handbook 130, which in‐

dicates that evidence of metrological traceability may be assessed through

laboratory recognition or accreditation. 

However, even if a laboratory is or was recognized or accredited, it is impor‐

tant to ensure that they still are recognized or accredited at the time of cali‐

bration when accepting the calibration certificate AND that the

measurements in question are actually on the laboratory’s measurement

Scope. The Scope defines the measurement areas for which the laboratory

has been recognized or accredited. For example, a laboratory only recognized

or accredited for mass has not demonstrated metrological traceability and

proficiency for volume. It is also important to ensure that the laboratory has

the capability of providing measurement uncertainties that are sufficiently

small for your applications. Otherwise, a calibration might have uncertainty

bars similar to Case A (Figure 1). Laboratories have a responsibility to con‐

sider the needs and requirements of the user, so the example in Case A

should never occur, but again, there is not a regulatory body that enforces

this.
Contact: Maureen Henzler at 

maureen.henzler@kda.ks.gov

June 17

Webinar Week ‐ NIST IR 6969, SOP 8, Part I 

10:00 a.m. to 12:00 p.m.

Class No. 5239

June 17

Webinar Week ‐ Uncertainty Budgets for

SOP 4

2:00 p.m. to 4:00 p.m.

Class No. 5257

June 18

Webinar Week ‐ Conducting an Effective

Management Review

10:00 a.m. to 12:00 p.m.

Class No. 5240

June 18

Webinar Week ‐ NIST IR 6969, SOP 8, Part II

2:00 p.m. to 4:00 p.m.

Class No. 5241

June 19

Webinar Week ‐ NIST IR 7383, SOP 18, Part I

10:00 a.m. to 12:00 p.m.

Class No. 5242

June 19

Webinar Week ‐ Uncertainty Budgets for

SOP 5

2:00 p.m. to 4: 00 p.m.

Class No. 5258

June 20

Webinar ‐ Uncertainty Budgets for SOP 19

10:00 a.m. to 12:00 p.m.

Class No. 5259

June 20

Webinar Week ‐ NIST IR 7383, SOP 18, 

Part II

2:00 p.m. to 4:00 p.m.

Class 5243

June 21

Webinar Week ‐ Calibration Report Evalua‐

tion

10:00 a.m. to 12:00 p.m.

Class No. 5244

June 21

Webinar Week ‐ Uncertainty Budgets for

SOP 14

2:00 p.m. to 4:00 p.m.

Class No. 5254

July 14 ‐ 18

NCSL International

Nashville, TN 

Contact: info@ncsli.org

July 14 ‐ 18

NCWM Annual Conference

Louisville, KY (con’d pg 5)

W&M Connection 4 Volume 4 Issue 2

Contract Review and Customer Service 

Another concept applied in the laboratories for ISO/IEC 17025 is that of con‐

tract review. We often hear the argument that, “we are a government labo‐

ratory and don’t have authority to sign contracts; therefore, this section is

not applicable for us.” Not true! 

When a laboratory accepts a standard and provides a calibration, they have

“agreed” to perform a calibration and provide a calibration report. The key

questions that must be considered at every level are, “What does the cus‐

tomer need?” and “Are we recognized or accredited to provide that calibra‐

tion service – is it on our Scope?” NIST OWM has responded to a number of

recent inquiries where a standard was calibrated by an accredited calibration

laboratory in a jurisdiction, without a full compliance assessment. When the

service company receiving that calibration submitted the calibration report

to another jurisdiction, assumptions were made about compliance assess‐

ments of the field standards during the calibration. As noted before, unless

the calibration report specifically claims that the standards were fully evalu‐

ated for compliance to a documentary standard, one should NOT assume this

to be the case. Also, as noted before, service companies may not be aware

of legally required assessments and/or calibration intervals. 

Suitability of Field Standards – in Use

I would like to conclude with some challenging thoughts and questions. Cal‐

ibrations of field standards may or may not involve a compliance assessment.

However, calibrations are also done at one point in time, under controlled

laboratory conditions, using laboratory procedures. Yet, field standards are

used in a wide variety of conditions for various applications, sometimes de‐

viating from the specific examination procedure outlines. How do we know

that the field standards are actually suitable for a wide variety of conditions

in use? How confident are we in our measurement results when field stan‐

dards knowingly do not comply with standards? How can we be sure a cali‐

brated value can be replicated in field use? How can we be sure deviations

from the field procedures produce reliable results? And finally, how can we

responsibly take enforcement action with all of these questions and doubt?

Some steps taken to provide assurance are to define specifications and tol‐

erances that are intended to allow for or account for these various conditions

and deviations. Every effort is made to consider suitable specifications and

tolerances to ensure that when field standards are used, good quality meas‐

urements are possible in a variety of conditions. However, additional factors

often need to be considered. Yet, even a good specification and full compli‐

ance along with a good calibration is not the full answer and can leave a sense

of doubt. Here are some specific examples and questions about standards

used in the weights and measures system that should be considered, the im‐

pact should be evaluated, and procedures should be followed.

Selection of weights that comply with NIST Handbook 105‐1 and a current

calibration might not address all of the user requirements. 

• Laboratories have observed Class F weights being out of tolerance on

the day they are brought into the laboratory for calibration, only to

find that they are in tolerance once they have properly equilibrated

with laboratory conditions (according to the standard operating prac‐

tice [SOP]). How often do laboratories calibrate field weights without

allowing suitable equilibration? How often are weights used outside

of normal laboratory operating conditions in the field? 
W&M Connection 5 Volume 4 Issue 2

Contact: info@ncwm.net

August 1

Webinar ‐ Calibration Report Evaluation

2:00 p.m. to 4:00 p.m.

Class No. 5245

August 8

Webinar ‐ Contract Review

2:00 p.m. ‐ 4:00 p.m.

Class No. 5246

August 12 ‐ 16

Handbook 133, Checking the Net Contents

of Packaged Goods

Class No. 5261

Scramento, CA

August 15

Webinar ‐ Document Control and Record‐

keeping

2:00 p.m. to 4:00 p.m.

Class No. 5247

August 19 ‐ 23 (5 days)

Fundamentals of Metrology

Class No. 5248

NIST/Gaithersburg, MD

September 9 ‐ 13

NEMAP*

Class No. 5218

Harrisburg, PA

September 16 ‐ 20

MidMAP*

Class No. 5219

Springfield, IL

September 22 ‐ 26

Western Weights and Measures Association

(WWMA)

Kalispell, MT

Contact: Doug Deiman at 

doug.deiman@alaska.gov

September 23 ‐ 27

SWAP*

Class No. 5220

Phoenix, AZ

October 7 ‐ 9

Southern Weights and Measures Associa‐

tion (SWMA)

Charleston, WV

Contact: Steve Benjamin at 

steve.benjamin@ncagr.gov

October 10

Webinar ‐ State Laboratory Annual Submis‐

sion Process*

2:00 p.m. to 4:00 p.m.

Class No. 5249

October 21 ‐ November 1 (2 weeks)

Mass Metrology Seminar

Class No. 5250 (con’d pg 6)

• Laboratories have observed errors on precision weight values that

were over 300 times the reported uncertainty of the calibration, due

only to a 2 °C gradient in the calibration laboratory. This would be ob‐

servable when evaluating a Class II balance. How often are the envi‐

ronmental conditions measured when evaluating a Class II balance?

Are the weights allowed to equilibrate? 

• Weights and measures officials or service agents have reported that

they use Class F weights for evaluating Class II balances. How often is

this done? Should a laboratory provide calibrations for weights to

meet the required weight classification (e.g., OIML Class F2) if they are

recognized for Mass Echelon III only (the answer is “no”)?

• Most state calibration laboratories do not have the ability to evaluate

density, surface finish, or magnetism requirements in some mass spec‐

ifications to determine compliance. Therefore, that laboratory is not

able to perform a full compliance assessment. However, most manu‐

facturers are able to perform these additional assessments. 

Selection of glassware that is marked Class A might not meet all of your

needs.

• Laboratories have reported that up to 50 % of the volumetric glassware

purchased for use in package checking is out of tolerance when pur‐

chased. How often is the glassware used without calibration because

it is purchased or marked as Class A by the manufacturer? 

Selection of a test measure or prover that complies with NIST Handbook

105‐3 with a calibration might not address all of the user requirements.

• Laboratories hear reports from service agents and field officials that

they do not correct the volume of large volume provers (certainly not

test measures) for the actual volume at time of test based on temper‐

ature. Most provers and test measures are calibrated to a reference

temperature 60 °F in the United States. Are field officials correcting

the volume of the prover real‐time? Are they using calibrated ther‐

mometers with evidence of metrological traceability? 

• In some recent instances, the standards were being exported and

needed to comply with OIML R 120. Are laboratory staff familiar

enough with the additional documentary standards that might be re‐

quested to assess compliance?

• How many large volume provers are grandfathered in because they

don’t meet specifications and/or are calibrated in the field without

suitable environmental controls?

Selection of a prover that complies with NIST Handbook 105‐4 with a calibra‐

tion might not address all of the user requirements.

• Laboratories observe that pressure gauges on LPG provers have been

changed between calibrations. Provers are often calibrated without

evaluation of the pressure gauge calibration. Are the replacement

pressure gauges calibrated, and do they agree with the previous

gauge? Again, are provers being used with calibrated thermometers

with evidence of metrological traceability?

Selection of a timing device or thermometer that complies with NIST Hand‐

book 105‐5, Specifications and Tolerances for Field Standard Stopwatches, or

105‐6, Specifications and Tolerances for Thermometers, with a calibration
W&M Connection 6 Volume 4 Issue 2

might not address all of the user requirements.

• Many laboratories are not recognized or accredited to evaluate timing

devices and to calibrate thermometers or to assess these standards

for compliance. How many are in use without evaluation or calibra‐

tion? 

Use of a Small Volume Prover that complies with NIST Handbook 105‐7 with

a calibration might not address all of the user requirements.

• Small Volume Provers were only assessed during development of

Handbook 105‐7 for refined fuel and fuel oil (and not LPG). The inte‐

gral pressure sensors and thermometers are often not calibrated by

the same laboratory when the volume is calibrated.

• Small Volume Provers are calibrated under laboratory conditions with

controlled flow, pressure, and temperatures, but we don’t have data

for their accuracy under a wide variety of flow rates and field condi‐

tions. When initial assessments were done, performing the slow flow

test identified a leak in the system that was not obvious during the fast

flow test. How often do short cuts take place when evaluating a meter

to save time?

• An industry laboratory was accredited to perform calibrations of a

Small Volume Prover gravimetrically and inappropriately demonstrated

their proficiency by calibrating a Class F mass standard.

Use of a weight cart that complies with NIST Handbook 105‐8 with a calibra‐

tion might not address all of the user requirements.

• Weight carts are often used without the associated checklist in Hand‐

book 105‐8. Weight carts are often calibrated without evaluating them

for compliance with the standard and have been grandfathered. What

is the impact of deviations? Laboratories have data to show the impact

of water on the surface that is wiped off and appears dry, with the cart

being out of tolerance. Are weight carts ever used on days with pre‐

cipitation? Handbook 105‐8 instituted a smaller gas tank with the use

of correction weights to account for the mass of fuel lost during use.

Field staff often do not account for these mass changes and many

weight carts found in service have not been modified to comply with

Handbook 105‐8.

The examples provided here are just the tip of the iceberg and only cover

those situations where a NIST Handbook currently exists. As you read this

article, you may have had additional questions – and even examples! Feel

free to contact me with additional examples and questions at

gharris@nist.gov.

NIST/Gaithersburg, MD

October 31 

Webinar ‐ Internal Auditing Best Practices

2:00 p.m. to 4:00 p.m.

Class No. 5251

November 18 ‐ 22 (5 days)

Volume Metrology Seminar

Class No. 5252

NIST/Gaithersburg, MD

2014

January 13 ‐ 17 (5 days)

Fundamentals of Metrology Seminar

Class No. not available

NIST/Gaithersburg, MD

January 19 ‐ 22 (4 days)

National Conference on Weights and Measures

(NCWM) Interim Meeting

Albuquerque, NM

info@ncwm.net

February 6

Webinar ‐ Conducting an Effective Management

Review

2:00 p.m. to 4:00 p.m.

Class No. 5255

*Invitation Only

**Limited to State Laboratory Program Participants

WEIGHTS AND MEASURES

IN THE NEWS

Pennsylvania ‐ witf.org

As counties shed weights and measures services, Ag. Dept. picks up slack

http://www.witf.org/news/2013/03/as‐counties‐shed‐weights‐and‐measures‐services‐ag‐dept‐picks‐up‐slack.php

The Office of Weights

and Measures

will glady include your weights and

measures related events in our 

calendar.

Contact the Editor:

Linda.Crown@nist.gov