NISTIR 7082

Proficiency Test Policy and Plan 

for State Weights & Measures 

Laboratories

(2023 Ed)

Georgia L. Harris 

Laboratory Metrology Program 

Office of Weights and Measures

Add OWM Staff 

responsible for updates

This publication is available free of charge from: 

Link to be provided for approved publication 

NISTIR 7082

Proficiency Test Policy and Plan 

for State Weights & Measures 

Laboratories

(2023 Ed)

Georgia L. Harris 

Applicable OWM 

staff 

This publication is available free of charge from: 

Link to be provided for approved publication 

Est: November 2023

U.S. Department of Commerce 

Gina M. Raimondo, Secretary 

National Institute of Standards and Technology 

Dr. Laurie E. Locascio, NIST Director and Under Secretary of Commerce for Standards and Technology

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i

Table of Contents

Table of Contents........................................................................................................................................... i

Abstract........................................................................................................................................................ iv

Keywords..................................................................................................................................................... iv

Acknowledgments........................................................................................................................................ iv

1. Introduction........................................................................................................................................... 1

1.1 Definitions........................................................................................................................................... 3

1.2 Abbreviations and Acronyms.............................................................................................................. 5

Table 1. Abbreviations and Acronyms Used in this Publication. ............................................................. 5

1.3 Applicable References ........................................................................................................................ 5

2. Program Scope ...................................................................................................................................... 6

2.1 Purpose and Description ..................................................................................................................... 6

2.2 Measurement Parameters.................................................................................................................... 6

Table 2. PT Parameters, Schedules, and OWM PT Program Scope......................................................... 7

3. Requirements ........................................................................................................................................ 8

4. Policies.................................................................................................................................................. 8

4.1 Compliance with International Standards........................................................................................... 8

4.2 Policy for PT Program Operations...................................................................................................... 9

4.3 Participation Policy........................................................................................................................... 10

4.4 Recognition Requirements................................................................................................................ 11

4.5 Laboratory and Individual Staff Competence Status........................................................................ 11

5. PT Participation Plan .......................................................................................................................... 12

Table 3. Example PT Participation Plan according to CMC................................................................... 14

6. Appendices (duplicated from NISTIR 7214)...................................................................................... 16

Form 1: OWM PT Feedback and Inquiry and Complaint Form............................................................. 16

Form 2: OWM PT Participation Request – Training/Qualification Form .............................................. 16

Form 3: RMAP Associate Membership Application.............................................................................. 16

Form 7: Examples of Proficiency Test 4-Year Plan and History/Log .................................................... 16
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ii
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iii
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Abstract

This publication provides the policies and plans for the Proficiency Testing (PT) Program of 

the NIST Office of Weights and Measures (OWM). This OWM Proficiency Testing (PT) 

policy and plan has been updated to ensure compliance with the latest applicable 

documentary standards and policies of the International Laboratory Accreditation 

Cooperation (ILAC). 

The PT program has been in place since the early 1980s as a core part of the support to State 

weights and measures laboratories through regional measurement assurance programs. 

Original activities were conducted as “round robin method in support of ongoing 

measurement assurance activities related to support for State laws with requirements for 

metrological traceability to national and international standards. 

The 2023 edition was updated based on feedback from users and included review and 

associated updates based on the latest applicable policies of the International Laboratory 

Accreditation Cooperation (ILAC), NIST Handbook 143, Recognition Program, NIST 

Handbook 150, National Voluntary Laboratory Accreditation Program (NVLAP) Procedures 

and General Requirements, and the latest available documentary standards for proficiency 

testing, including ISO/IEC DIS 17043:2022, Conformity Assessment — General 

requirements for the competence of proficiency testing providers, and ISO 13528:2022, Third 

Edition, 2022-08, Statistical methods for use in proficiency testing by interlaboratory

comparison. 

Kelleen Larson, L. F. Eason, and Ken Fraley in collaboration with NIST OWM personnel at 

the 2012 PT Workshop, Boulder, Colorado, proposed significant updates to this publication, 

which formed the foundation for the 2018 update. Reviews by the participants listed below

significantly contributed to the development of this policy and plan. The initial 2004 edition 

was developed under contract with Jeff C. Gust. 

Keywords

Accreditation, calibration, interlaboratory comparison, proficiency testing, recognition.

Acknowledgments

The following individuals participated in the 2022 review: 

• 

• 

• 

• 

The following individuals participated in the 2018 review:

• Val Miller, NIST / OWM

• Tim Osmer, NIST / OWM
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• Elizabeth Gentry, NIST / OWM

• Titilayo Shodiya, NIST / National Voluntary Laboratory Accreditation 

Program (NVLAP)

The following individuals contributed to the review resulting from the 2012 PT Workshop 

Review:

• Georgia Harris, NIST / OWM

• Kelleen Larson, Consultant

• L. F. Eason, rEason Metrology Consulting, LLC

• Ken Fraley, Consultant

• Val Miller, NIST / OWM

• Elizabeth Gentry, NIST / OWM

• Aaron Aydelotte, Oregon Metrology Laboratory

• Barbara Belzer, NIST / National Voluntary Laboratory Accreditation Program 

(NVLAP)
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NISTIR 7082 DRAFT 20230301 Page 1 of 16

Proficiency Test Policy and Plan

for State Weights and Measures Laboratories

1. Introduction

This Office of Weights and Measures (OWM) proficiency testing (PT) policy and plan is 

designed to assist the National Institute of Standards and Technology (NIST), the State weights 

and measures laboratories, and Regional Measurement Assurance Program (RMAP) groups in 

identifying the minimum level of proficiency testing needed on an ongoing basis to comply with 

international expectations as described in the PT Requirements section of this document. This 

publication is an integral component of the OWM PT Program Quality Management System. 

Referenced procedures and forms are integrated in the NISTIR 7214, Office of Weights and 

Measures, Quality Manual for Proficiency Testing and Interlaboratory Comparisons. For user 

convenience, Forms 1 through 3, and 7 are duplicated in this publication.

In addition to State weights and measures laboratory participation, the OWM PT program

includes participation (when applicable) by the U.S. Department of Agriculture Grain 

Inspection and Packers and Stockyards master track scale, Los Angeles County Weights and 

Measures, the District of Columbia, and the U.S. territories of Puerto Rico and the U.S. Virgin 

Islands. In realizing compliance to this policy, some of the proficiency tests will be conducted 

through the RMAP regional groups and others will be coordinated on a national basis. 

The terms Interlaboratory Comparison (ILC) and Proficiency Test (PT) are often used 

interchangeably. However, proficiency tests are a subset of ILCs that may be used for other 

purposes. Hereafter in this document, the term PT will be used to refer to all proficiency tests

and ILCs to refer to interlaboratory comparison for simplicity, recognizing that some ILCs are 

not designed to be proficiency tests. This policy and plan address these different coordination 

needs. The OWM PT program serves purposes beyond demonstrating proficiency for

recognition and accreditation activities. Proficiency testing involves the use of interlaboratory 

comparisons for the determination of laboratory performance for:

a) Evaluating laboratory performance of specific measurement scope capabilities and 

monitoring continuing performance/Calibration Program;

b) Identifying risks or problems and initiating corrective action. Example causes may 

include inadequate measurement procedures, ineffectiveness of staff training and 

supervision, or needed standards and equipment recalibration; 

c) Establishing the effectiveness and comparability of measurement methods/Documented 

Validated Procedures (e.g., method validation); 

d) Evaluating method performance characteristics/Ensuring Validity (e.g., method 

validation).

e) Providing additional confidence to laboratory customers; 

f) Identifying of differences among laboratories/Unbroken Chain of Calibrations;

g) Educating participating laboratories based on comparison outcomes/Technical 

Competence. For example, Laboratory Auditing Program (LAP) problems are assigned 

to the state weights and measures staff after OWM training and prior to OWM 
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NISTIR 7082 DRAFT 20230301 Page 2 of 16

recognition as approved signatories for measurements); 

h) Validating uncertainty claims/Documented Measurement Uncertainties

i) Evaluating a reference value; and

j) Providing additional confidence on conformance statements

While OWM does not operate a formal accreditation program, OWM is responsible for 

implementing a weights and measures laboratory recognition program according to NIST 

Handbook 143, Program Handbook. OWM issues Certificates of Metrological Traceability that 

detail defined measurement scopes to support legal metrology measurements that underpin U.S. 

trade and commerce. This policy and plan are consistent with international policies set forth by 

the International Laboratory Accreditation Cooperation (ILAC) as of 2023. It also supplements 

the PT requirements in NIST Handbook 143, Section 3.5.2.2, and ISO/IEC 17025:2017. 

As part of the State Laboratory Recognition Program (NIST Handbook 143), OWM is 

responsible for training and conducting PTs through the RMAPs. Metrologists from State legal 

metrology laboratories within six regions are required to attend annual training and participate 

in selecting, planning, and implementing a PT in planned measurement areas aligned with 

their OWM recognition measurement scope. At the RMAP, each participant laboratory has its 

own PT plan based on their laboratory’s scope to prove proficiency in each are of testing 

performed. Most PT plans are organized and planned to cover proficiency in every area of 

calibration based on the lab’s scope within a 4-year period. State metrology laboratories may 

also seek accreditation from accreditation bodies that are signatories to the ILAC Mutual 

Recognition Arrangement (MRA). RMAP PT 4-year plan and results may be used to meet both 

recognition and accreditation requirements.

The six regions are the:

1) Northeastern Measurement Assurance Program (NEMAP);

2) Southeastern Measurement Assurance Program (SEMAP);

3) Southwestern Assurance Program (SWAP);

4) Mid-America Measurement Assurance Program (MidMAP);

5) Western Regional Assurance Program (WRAP); and

6) Caribbean Measurement Assurance Program (CaMAP)

Most proficiency tests are planned, coordinated, and analyzed by an administrative team of PT 

coordinators who is chosen on a volunteer basis, PT analysts, and includes a NIST technical 

point of contact. All members of the administrative team are required to be technical experts and 

members of the regional groups. Any new PT Coordinators or PT Analysts will serve as mentor 

for new PT coordinators. The ongoing operation of proficiency tests in the RMAPs is managed

according to a regional schedule. Some proficiency tests are coordinated by NIST personnel,

regional technical experts, or NIST OWM approved PT providers. All OWM proficiency tests

are overseen by NIST staff and final reports, and amended or appended final reports are 

reviewed, produced, and signed by NIST staff. 

OWM policies and procedures are aligned with the most recent ILAC documents and ensures that 

formal PT planning and follow-up continues to be implemented.
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In this document, the following verbal forms are used:

• “Shall” indicates a requirement;

• “Should” indicates a recommendation;

• “May” indicates a permission; and 

• “Can” indicates a possibility or a capability.

1.1 Definitions

For the purpose of this document, terms, and definitions from the International Vocabulary of 

Metrology (VIM) and the listed below apply in this document.

Accreditation: A formal process of determining the technical competence of a laboratory to 

carry out specific types of testing, measurement, and calibration. It provides formal 

acknowledgement that the laboratory is competent, impartial, and independent. Regular

evaluation occurs to ensure continued compliance with requirements and to check that standards

of operation are being maintained.

Accuracy Class: A class of measuring instruments or measuring systems that meet stated 

metrological requirements that are intended to keep measurement errors or instrumental 

measurement uncertainties within specified limits under specified operating conditions.

Calibration: A set of operations which establish, under specified conditions, in a first step, 

establishes the relationship between values with measurement uncertainties provide by 

measurement standards and corresponding indications with associated measurement uncertainties 

and, in a second step, uses this information to establish a relation for obtaining a measurement 

result from an indication. 

Calibration and Measurement Capability (CMC): A CMC is a calibration and measurement 

capability available to customers under normal conditions: (a) as published in the BIPM key 

comparison database (KCDB) of the International Committee for Weights and Measures (CIPM)

Mutual Recognition Arrangement (MRA); or (b) as described in the laboratory’s scope of 

accreditation granted by an accreditation body that is signatory to the International Laboratory 

Accreditation Cooperation (ILAC), MRA.

Certificate of Metrological Traceability: Document issued by OWM to a participating state 

legal metrology laboratory that has been granted recognition according to NIST Handbook 143 

requirements and is always issued with a Measurement Scope. 

Confidentiality: property that information is not made available or disclosed to unauthorized 

individuals, entities, or processes. OWM PTs are not confidential, but PT data and PT reports 

have usage restrictions. PT reports are available through the Freedom of Information Act.

Corrective Action: An action taken to eliminate the causes of an existing nonconformity or 

other undesirable situation to prevent recurrence.

Impartiality: presence of objectivity. Note 1 to entry: Objectivity means that conflicts of interest 

do not exist or are resolved so as not to adversely influence subsequent activities of the 

laboratory. Note 2 to entry: Other terms that are useful in conveying the element of impartiality 
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NISTIR 7082 DRAFT 20230301 Page 4 of 16

include “freedom from conflict of interests”, “freedom from bias”, “lack of prejudice”, 

“neutrality”, “fairness”, “open-mindedness”, “evenhandedness”, “detachment”, “balance”.

Interlaboratory Comparison: The organization, performance and evaluation of measurements 

or tests on the same or similar items by two or more laboratories or inspection bodies accordance 

with predetermined conditions.

Intralaboratory Comparison: The organization, performance, and evaluation of measurements 

or tests on the same or similar items within the same laboratory in accordance with 

predetermined schedule.

Laboratory: An organization that performs tests, calibrations, and/or sampling associated with 

subsequent testing or calibration. When a laboratory is part of an organization that carries out 

activities additional to calibration and testing, the term "laboratory" refers only to those parts of 

that organization that are involved in the calibration and testing process. A laboratory’s activities 

may be carried out at a permanent location, temporary, or remote location. A laboratory may be 

further defined as being a physical entity that is a testing or calibration facility that is separate 

and apart physically from any other laboratory whether sharing common ownership, 

management, or management systems with any other laboratory. 

Measurement Procedure: A detailed description of a measurement according to one or more 

measurement principles and to a given measurement method, based on a measurement model,

and including any calculation to obtain a measurement result.

Measurement Scope: A range of approved measurements issued by OWM to a participating 

state legal metrology laboratory that has been granted OWM recognition. The measurement 

scope is found on the Certificate of Metrological Traceability and details calibration services for 

which the laboratory is recognized. See also: Calibration and Measurement Capability.

Metrological Traceability: The property of a measurement result whereby the result can be 

related to a reference through a documented unbroken chain of calibrations, each contributing to 

the measurement uncertainty.

Proficiency testing administrative team (PT administrative team): the collection of OWM 

Laboratory Metrology Program staff, and PT volunteers such as PT regional coordinators, PT 

coordinators, PT analysts, and any other NIST technical staff engaged in the planning and/or 

evaluation of a PT in the OWM PT program.

Proficiency testing analyst (PT analyst): Assigned person who is responsible for handling data 

related activities for the proficiency test, including initial review, data entry in analysis tools, 

initial assessments and selection of reference values, and recommendations to OWM regarding 

final evaluation and assessment. 

Proficiency testing coordinator (PT coordinator): Assigned person who is responsible for 

implementation of the PT, including preparation and submission of the PT plan for participant 

review and OWM approvals, managing the flow and oversight of the schedule, shipping, 

intervening on problems that arise to notify OWM and ensure completion of the PT round in a 

timely manner.
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PT Participant: Laboratory, organization or individual metrologist that receives proficiency 

test artifacts, follows all planned instructions, tasks, and timelines, and submits the measurement 

results for review by the proficiency testing provider.

Proficiency Test: The determination of the calibration or testing performance of a laboratory or 

the testing performance of an inspection body against pre-established criteria by means of 

interlaboratory comparison. (Historically, the term “round robin” but is inconsistent with current 

international documentary standards and should not be used.)

State Laboratory Program (officially known as the OWM Laboratory Metrology 

Program): A NIST OWM Program that provides guidance, technical support, and assistance to 

state legal metrology laboratories to ensure accurate and traceable measurements are made 

within each participating jurisdiction.

1.2 Abbreviations and Acronyms

Table 1. Abbreviations and Acronyms Used in this Publication.

Abbreviation or 

Acronym Description

AB Accreditation Body

IACET International Association for Continuing Education and Training

IEC International Electrotechnical Commission

ILAC International Laboratory Accreditation Cooperation

ILC Interlaboratory Comparison

ISO International Organization for Standardization

MRA Mutual Recognition Arrangement

NIST National Institute of Standards and Technology

NISTIR NIST Interagency or Internal Report

NVLAP National Voluntary Laboratory Accreditation Program

OWM Office of Weights and Measures

PT Proficiency Test

RMAP Regional Measurement Assurance Program

1.3 Applicable References 

The following documents or contents therein are referred to in the text in such a way that some 

or all of their content constitutes requirements of this document. For dated references, only the 

edition cited applies. For undated references, the latest edition of the referenced documents 

(including any amendments) applies.

• ISO/IEC Guide 98-1:2009, Evaluation of Measurement Data – Guide to the Expression 

of Uncertainty in Measurement (GUM), (also known as JCGM 100:2008).

• ISO/IEC Guide 99:2007, International Vocabulary of Metrology – Basic and General 

Concepts and Associated Terms (VIM), 3rd edition, 2008 version with minor corrections

(Confirmed 2015), (also known as JCGM 200:2012).
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• ISO/IEC 17011:2017, Conformity Assessment – Requirements for Accreditation Bodies 

Accrediting Conformity Assessment Bodies. 

• ISO/IEC 17025:2017, General Requirements for the Competence of Testing and 

Calibration Laboratories. 

• ISO/IEC DIS 17043:2022, Conformity Assessment – General Requirements for 

Proficiency Testing. 

• ISO 13528, Third edition, 2022-08, Statistical Methods for use in Proficiency Testing by 

Interlaboratory Comparison. 

• ILAC P9: 2014, ILAC Policy for Participation in Proficiency Testing Activities.

• ILAC P10: 2020, ILAC Policy on Metrological Traceability of Measurement Results. 

• ILAC-P14: 2020, ILAC Policy for Uncertainty in Calibration. 

• NIST Handbook 143:2023, State Weights and Measures Laboratories, Program 

Handbook, 7th Edition. 

• NIST Handbook 150:2020, NVLAP Procedures and General Requirements.

• NIST Handbook 150-2:2023, NVLAP Calibration Laboratories. 

• NISTIR 7214, Office of Weights and Measures, Quality Manual for Proficiency Testing 

and Interlaboratory Comparisons. 

2. Program Scope

2.1 Purpose and Description

The OWM PT program is administered to support State metrological traceability legal 

requirements and operated through a national infrastructure of regions, the Regional 

Measurement Assurance Program. Participation in all OWM proficiency tests is limited to State 

Weights and Measures laboratories, where personnel have demonstrated adequate on-the-job 

training and success completion of applicable OWM training seminars. OWM PT program

activities are limited to the U.S. states and territories. State metrology staff are automatically 

eligible to participate in planned OWM PT program activities if suitable training has been 

completed or if participation is approved by OWM. 

Non-weights and measures laboratory participants who are members of the RMAPs are eligible 

to participate in the OWM PT program only when personnel have successfully completed 

training requirements, according to HB 143 Table 2 (at suitable and NIST-OWM-approved 

levels), participate in annual RMAP training on an ongoing basis, and/or are approved for 

participation by OWM. 

OWM personnel are responsible for evaluating PT program participants, including the approval 

or denial of participation before a PT commences. The OWM PT program is not available to 

support unsolicited requests or contracts for services outside of the members of the RMAP 

groups. 

2.2 Measurement Parameters 

NIST HB 143 defines recognition scopes (calibration and measurement capabilities (CMC) 
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includes measurement parameter, range of measurements, uncertainties, and methods). At 

minimum laboratories are required to have objective evidence of ‘favorable/successful’ 

proficiency testing results for each discipline in their scope of accreditation within a four-year 

cycle. Successful PT completion in one measurement area, range, or parameter does not 

necessarily indicate that a laboratory will be successful in other areas. PT requirements shall be 

met for all measurement parameters where a laboratory personnel serves as an approved 

signatory because each scope area is based on a unique system of resources, including facilities, 

standards, and equipment.

Table 2. PT Parameters, Schedules, and OWM PT Program Scope.

Measurement

Parameter

Typical 

Calibration 

Standard

Typical 

Recognition

Scope Range

Typical 

PT Range

Recommended

Participation 

per Parameter

(Alternating 

Ranges and 

Measurement 

Systems per PT 

Round)

Example

Frequency

Mass 

Echelon Ia, b Mass Standard

30 kg to 1 mg

50 lb to 0.001 lb

8 oz to 0.03125 oz

20 kg to 1 kg

50 lb, 20 kg, 10 kg 2 year 4 year

1 kg to 1 mg

Mass

Echelon IIa Mass Standard

1200 kg to 1 mg

2500 lb to 0.001 lb

8 oz to 0.0125625

50 lb, 20 kg, 10 kg, 

5 kg

2 year

4 year

1 kg to 1 mg

100 g to 1 mg

Mass

Echelon IIIa Mass Standard

2500 kg to 1 mg

2500 lb to 0.001 lb

8 oz to 0.0125625

50 lb, 25 kg, 25 lb, 

10 kg 

2 year

5 year

5 kg to 100 mg

1 kg to 1 mg

10 lb to 0.001 lb

4 year

500 lb 6 year

Volume

Echelon I

(Gravimetric) a, b

Prover

500 L to 100 mL

100 gal to 1 gi

100 gal

2 year

4 year

Slicker 5 gal 4 year

Glassware 1 L to 100 mL

1 gal to 1 gi 4 year 

Volume

Echelon II

(Volume 

Transfer) a

Test Measure 

or Prover 5000 L to 100 mL

2000 gal to 1 gal

5 gal 2 year 4 year

Prover

100 gal 3 year 10 to 25 gal 6 year

Lengtha

Tape Up to 30 m

Up to 200 ft 100 ft

2 year

4 year

Rule Up to 1 m

Up to 24 in 18 in 4 year
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Measurement

Parameter

Typical 

Calibration 

Standard

Typical 

Recognition

Scope Range

Typical 

PT Range

Recommended

Participation 

per Parameter

(Alternating 

Ranges and 

Measurement 

Systems per PT 

Round)

Example

Frequency

Temperature

Accuracy Class 

I, Class II, Class 

III, and Class 

IV

Liquid-InGlass 

Thermometers,

RTD’s, 

SPRT’s, 

Thermistors,

and 

Thermocouple

s

230 °C to -30 °C

450 °F to -25 °F 100 °C to 0 °C 4 year 4 year

Frequencya,b Tuning Fork 10 kHz to 1 kHz 4 year 4 year

Timea,b Stopwatch ≤ 24 h 3 h 4 year 4 year

Hydrometera,b Hydrometer 5 year 5 year

a

Typically coordinated by RMAP, bcoordinated by NIST.

NOTE: Mass Echelon I, II, and III correspond to details published in NIST Handbook 143, Program Handbook 

and are directly related to OIML R111 (2004) classes of weights. Echelon I: E1 and E2. Echelon II: F1 and F2. 

Echelon III: M1, M2, M3 (etc.). The ASTM E617-18 classes correspond to those of OIML R111. NIST Handbook 

105-1 (1990), Class F weights corresponds to Echelon III. Volume Echelon I is related to gravimetric volume 

calibration measurement procedures. Echelon II is related to volume transfer test methods. Temperature Accuracy 

classes are related to guidance published in NVLAP 150-2 Annexes.

Six year exceptions are provided for large trailer mounted provers and mass standards due to cost and logistics.

3. Requirements

The NIST OWM is not a formal accreditation body and does not enter into national or 

international agreements for acceptance and reciprocity. NIST OWM implements a 

Recognition Program (NIST HB 143, Program Handbook) for State Weights and Measures 

laboratories to ensure metrological traceability and ensure the implementation of uniform

international measurement practices. NIST Handbook 143 is based on ISO/IEC 17025 and 

requires participation in a measurement assurance program and ongoing proficiency This 

policy and plan are designed to ensure State laboratories demonstrate competence and 

proficiency and comply with ISO/IEC 17025 and ILAC P9.

4. Policies

4.1 Compliance with International Standards

It is NIST OWM policy to comply with ILAC policies and ISO/IEC 17043 when operating the 

PT program to the extent possible. OWM does not claim compliance to ISO/IEC 17011 and is 

not an accreditation body. Accreditation bodies that have signed the ILAC Mutual Recognition 
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Arrangement (ILAC MRA) have been peer evaluated to ensure demonstrated compliance with 

ISO/IEC 17011 and ILAC P9.

4.2 Policy for PT Program Operations

The NIST OWM offers IACET accredited training seminars in Fundamentals of Metrology, 

Mass, Volume, and Advanced Mass to State weights and measures laboratories and nonweights and measures participants. Courses participants are required to demonstrate successful 

achievement of learning objectives that are specifically related to competency. OWM also uses 

the results of proficiency tests to evaluate the application of training concepts in participant 

State laboratories as Laboratory Auditing Program (LAP) problems. The LAP problems 

integrate proficiency tests and serve as special internal technical audits and participant 

technical competency.

All recognized (NIST Handbook 143) laboratories shall demonstrate satisfactory participation 

in suitable PT activities that align with their measurement scope, where available. Staff must be 

identified in the PT Plan during the planning stages for each PT. All or current laboratory staff

shall demonstrate proficiency in each four year cycle in the measurement areas identified on 

the laboratory Scope for which they have documented responsibility and Approved Signatory 

status. Failure to participate in an available PT shall negatively impact Approved Signatory 

status, recognition status, and OWM-approved laboratory recognition. Failure to participate 

may result in removal of measurement parameters from the laboratory scope until applicable 

proficiency tests are completed. Proficiency tests and interlaboratory comparisons objectively 

validate laboratory measurement capability. NIST Handbook 143 requires the use of 

proficiency testing and interlaboratory comparisons as a mechanism to ensure measurement 

result quality and validate calibration methods consistent with requirements in 17025:2017, 

section 7.7. 

Laboratories shall report actual measurement uncertainties on calibration certificates for all 

proficiency tests consistent with ISO/IEC Guide 98-1 (GUM) and ILAC P14. 

Laboratories shall maintain records of PT participation, conduct follow-up evaluations, and 

demonstrate corrective action effectiveness when PT failures occur. Pass/fail criteria are 

determined and documented during the planning phase of each PT and communicated to 

participants as a part of the PT 4-year Plan.

Feedback, inquiries, or complaints regarding any aspect of the OWM PT program may be 

submitted by completing Form 1. Appeals regarding OWM decisions (outside of performance 

evaluations) must be submitted in writing on the laboratory’s official organizational letterhead. 

General feedback may be submitted to OWM at any time and is solicited as a part of each PT 

Report. OWM acknowledges receipt of input and manages communications following the 

OWM PT program SAP 2, Standard Administrative Procedure for Handling Action Items. 
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4.3 Participation Policy

Any laboratory organization that would like their metrology personnel to participate in a PT

activity within the scope of the OWM PT program must be a member of a Regional 

Measurement Assurance Program (RMAP) and agree to operate in accordance with these 

policies and conditions for participation.

• The participating organization shall annually attend RMAP meetings and participate in 

PT/ILC planning discussions. 

• Metrologists and their participating organizations shall be technically qualified for the 

measurement parameter of interest based on recognition or accreditation to ISO/IEC 

17025 (or compliance as approved by OWM). State weights and measures staff shall 

comply with NIST Handbook 143 training requirements, summarized in Table 2, or 

receive exceptions from OWM during their planning phase. Non-weights and measures 

laboratory staff must complete available OWM seminars where applicable and document 

additional training for staff members by using Form 2, Training Qualification Form. 

• Each participating organization and metrologist shall follow all PT plan details and 

instructions, including the use of designated procedures where specified or a laboratory 

procedures must be submitted and approved by OWM during the planning phase.

• All OWM proficiency tests are considered OPEN. As a condition of participating in 

OWM proficiency tests, participants must waive confidentiality. Anonymity is not 

implied or guaranteed, however there are restrictions on appropriate sharing and use of 

PT reports.

• PT participants shall not use any PT report for any purpose other than internal 

measurement assurance, staff technical competency (LAP problems) or 

accreditation/recognition activities. The use of OWM proficiency tests in sales, 

marketing, publication/presentation, or sharing or advertising of the results of any 

participating laboratory is strictly prohibited.

• A PT participant shall not falsify any measurement results or other information submitted 

to the PT Coordinator, PT Analyst, or OWM. 

• Each PT participant shall keep details regarding the activity in confidence. Seeking to 

obtain measurement information for artifacts prior to participation in the proficiency test 

(collusion) is prohibited. Participants will share data only with the PT analyst or OWM 

personnel. Sharing any artifact information or measurement results between participants, 

which is provided in the proficiency test final report, is prohibited. Exception: The PT 

coordinator, PT analyst, or OWM personnel may communicate draft En values or 

significant error/bias to individual laboratories. This exception enables the PT 

coordinator, PT analyst, and/or OWM personnel to monitor immediate investigation, 

corrective action, and retesting (if needed) by the participant before the artifact is

transferred to the next scheduled organization.

• An application is available for new organizations that have not previously been RMAP 

members. Any non-weights and measures laboratory seeking to participate in the RMAP 

proficiency tests must be approved by State members for Associate membership within 

the RMAP. Potential RMAP members must be sponsored by the state in which the 

organization resides. Applicants must agree to annual RMAP participation and 

compliance with policies as stated in this document. See Form 3, Application for 
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NISTIR 7082 DRAFT 20230301 Page 11 of 16

Membership and Form 2 for Staff Qualifications (if needed). 

OWM reserves the right to refuse participation to any laboratory or participant if the

laboratory or participant has violated quality policies including any one or all of the 

following: failing to meet training and/or qualification requirements, collusion to obtain 

advanced information about expected measurement results, falsification of reported results, 

failing to follow procedures for artifact care and handling, repeated schedule delays, or other 

technical issues that could adversely affect the results for the other PT participants. When 

OWM identifies a policy or technical violation that negatively impacts the PT activity, each 

participating organization and associated participants shall be notified in writing. In some 

cases, technical guidance may be provided to ensure that the laboratory has an opportunity 

for corrective action following the OWM Standard Administrative Procedure 5 for Handling 

Collusion, Falsification, or Participant Operational Failures (published in NISTIR 7214). 

4.4 Recognition Requirements 

A participant laboratory seeking initial OWM recognition (NIST Handbook 143), reinstating 

lapsed recognition, or maintaining ongoing recognition shall participate in the OWM PT 

program. Laboratories initiating recognition must complete at least one approved PT aligned 

with each major parameter within the requested measurement scope before a Certificate of 

Measurement Traceability is granted (as practical and available). Laboratories seeking 

ongoing recognition shall participate in at least one PT for each measurement area included 

in the laboratory’s scope of recognition during a four-year period. Section 5 (PT Participation 

Plans) details these requirements.

Each laboratory shall develop a PT participation plan that is coordinated with the appropriate 

RMAP region. The laboratory PT participation plan shall be consistent with minimum PT 

program participation guidelines. An example PT participation plan is available within this 

document. The laboratory shall annually review the PT participation plan and consider any 

operational changes, such as facility, personnel, equipment, standards, methods, 

measurement scope, or other factors.

Unique measurement parameters, artifacts, or methods may require special PT 

considerations. If a suitable PT is unavailable, an alternative approach may be considered by 

and coordinated with OWM staff. All proficiency tests require completing a formal PT Plan 

and shall include OWM approval before commencing.

4.5 Laboratory and Individual Staff Competence Status 

Laboratory recognition is contingent on successful PT participation. Each metrologist who has 

successfully performed within an OWM PT has demonstrated competence for that parameter. 

The laboratory organization must maintain at least one competent metrologist (Approved 

Signatory (see Handbook 143, Program Handbook for Approved Signatory definition and 

requirements) per measurement parameter within the recognized scope to achieve and retain 

recognition. Multiple approved signatories within a measurement parameter are permitted and 

encouraged. Metrologists that do not successfully demonstrate competence through an OWM 

PT, or who have demonstrated successive failures, shall not be granted approved signatory 
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status for the laboratory unless there is suitable and demonstrated corrective action.

Laboratory management shall ensure that each staff member is approved to perform

calibrations within the recognized measurement scope and participate in each proficiency test

when the artifact(s) arrives at the facility. This is an essential element of effective succession 

planning. Failing to comply with this requirement may impact the laboratory recognition 

status. Each person intending to participate in a PT must be explicitly named in the PT Plan 

document, be identified in the laboratory PT Follow Up forms, and identified in the 4-year 

laboratory analyses. 

PT performance is not independent from laboratory processes. Each PT participant is evaluated

in conjunction with the laboratory operational system (e.g., facility, equipment, standards, 

methods, etc.). When a metrologist performs measurements in another laboratory organization 

or facility, they shall demonstrate competence within that unique measurement system.

5. PT Participation Plan

The information presented below provides guidance for planning PT activities to meet the 

OWM PT program policy requirements. The level of organization and frequency of proficiency 

tests provided in this document is based on the following considerations and guiding principles.

a. Each Region (RMAP) shall develop a PT 4-year plan and schedules by each RMAP 

and updated at least annually so that proficiency tests can be organized on a regional 

and/or national level. NIST OWM participates in all planning discussions and 

evaluates each specific plan for compliance to program policies before authorizing 

the initiation of the activity. State laboratories are required to ensure that their 

laboratory scope is covered in the RMAP plan or seek additional PT opportunities. 

NIST OWM may develop and update a PT plan for programs that require national 

coordination.

b. Each RMAP region shall annually review PT Participation Plans to determine if the 

“frequency” is appropriate and adequate. A maximum number of proficiency tests

will be coordinated each year balancing between the full parameters/scopes of the 

laboratories and a reasonable PT workload. Coordination between RMAP regions is 

also acceptable to allow a new metrologist to participate in an PT within another 

region without having to wait an extended time period for the PT to be conducted in 

their region. Out-of-region participation requests shall be documented within 

individual PT plans and approved by OWM before the activity is initiated.

c. The number of laboratories with the measurement capabilities for the specific 

metrology parameter affects whether a PT is conducted regionally or nationally. For

common measurement parameters, multiple RMAPs shall simultaneously organize 

proficiency tests in the same measurement parameter to enable laboratories and 

metrologists to participate. For less common measurements, OWM will coordinate a 

PT on a national basis in order to have adequate number of participants that meet the 

PT requirements for the scope parameter.
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d. Measurement Parameters. Preference is given to measurement parameters with the 

largest workloads within the state laboratories. The number of measurements made 

within a specific measurement parameter is considered. For example, mass 

calibrations make up nearly 90 % and length calibration accounts for about 1 % of 

the State Laboratory Program workload. Therefore, more proficiency tests are 

required in mass than length. For this reason, a frequency greater than two years is 

allowed for some parameters. The historic stability of the standards used and tested 

within a specific metrology area shall be considered. Length standards in use 

within a laboratory have been shown to be more stable than mass standards. For 

this reason, fewer length proficiency tests are required to provide adequate 

demonstration of measurement competency.

e. Cost and Logistics. The long-range PT participation plan for participant laboratories, 

RMAPs, and OWM shall include plans to develop proficiency tests for each 

measurement parameter as it is economically and logistically feasible. The cost and

logistics of the PT will be considered in selecting artifacts and in scheduling 

shipping. For example, large volume (e.g., 100 gal) or large mass (e.g., 500 lb) 

proficiency tests that require the movement of a large trailer mounted prover through 

RMAP regions are coordinated and overseen by NIST with assistance from regional 

PT Coordinators. The frequency of this type of PT is also limited by cost of the 

standard because it is impractical to purchase multiple standards and the length of 

time necessary to circulate the standard to all laboratories within each region. In 

contrast, a 5 gallon test measure artifact is easily shipped at a modest cost. A large 

volume 100 gallon prover PT may be on a longer frequency (e.g., 5 year or 6 year)

whereas small volume 5 gallon test measure, may be on a more frequent (e.g., 1 year 

or 3 year) schedule. Conducting proficiency tests with large calibration items such as 

weight carts, railroad test cars, provers for liquefied petroleum gas (LPG) is not 

considered feasible and these items are not required to be part of the PT plan. 

Demonstration of competency for such items is required during training and/or 

onsite assessments. 

f. Minimum requirements. Each State laboratory shall participate in one PT per 

major sub-area of their accredited or recognized scope at least every four years

(and in each scheduled PT within their RMAP region when available). It is 

recommended that organizations participate in PT activities for each specific 

measurement parameter and calibration method that the laboratory employs as 

a part of ongoing measurement assurance program. Failure to participate in an 

available PT shall negatively impact accreditation/recognition and the 

approved measurement scope and may result in removal of measurements 

from a laboratory Scope.

Each State laboratory shall ensure their participation in the RMAP PT plans 

during each 4-year cycle. 

g. The specific ranges selected within each measurement parameter will be considered 
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and should vary from PT to PT. For example, the range of 20 kg to 2 kg may be 

selected one year and the range 1 kg to 1 mg may be selected in another. Single 

weights and/or sets may also be considered.

h. Additional Special proficiency tests are permitted. Additional types of PT or 

Interlaboratory Comparison activities are permitted. Examples of special PT 

activities include the evaluation of: calibration of masses with unique densities or 

surface finishes, mass standard density or magnetism, tests of environmental 

equipment used in buoyancy corrections (temperature, pressure, relative humidity), 

key comparisons, tests for new designs of field standards used in weights and 

measures, tests for evaluation of environmental effects on calibration values and 

uncertainties, tests for comparison of measurement procedures, and tests for 

evaluation and verification of measurement traceability.

i. The OWM PT quality system procedures, forms, and tools are used to implement PT

activities, including planning and reporting (see NISTIR 7214, Office of Weights 

and Measures Quality Manual for Proficiency Testing and Interlaboratory 

Comparisons). A Good Laboratory Practice (GLP) for PT Follow-Up is available to 

help guide laboratories in conducting measurement assurance assessments using the 

results of proficiency tests. The PT Follow-up Form in the GLP is required for State 

laboratories as a part of annual recognition reviews. PT follow-up tools include 

forms to help the laboratory document a successful PT as well as analyze and 

implement appropriate corrective action when unsuccessful PT results occur.

The sample matrix shown in Table 3 illustrates an example of how a laboratory can document 

not only a 4-year plan but a proficiency testing strategy that will ensure each parameter within 

the accredited/recognized measurement scope is evaluated according to the requirements of this 

policy. Both the laboratory and the accreditation/recognition body can observe at a glance all 

planned proficiency activities, confirming compliance to this policy or identifying gaps with 

ease. During a laboratory assessment, the laboratory scope, staff participation, and compliance to 

past plans is often evaluated. Ensuring completion of the 4 or more year plan is the responsibility 

of each laboratory. 

Table 3. Example PT Participation Plan according to CMC.

Parameter 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032

Mass

Echelon I

1 kg

to

1 mg

4 yr

20 kg

to

1 kg

4 yr

1 kg

to

1 mg

4 yr

20 kg

to

1 kg

4 yr

1 kg

to

1 mg

4 yr

Mass

Echelon II

1 kg

to

1 mg

4 yr

100 g

to

1 mg

2 yr

20 kg

to

1 kg

4 yr

100 g

to

1 mg

2 yr

1 kg

to

1 mg

4 yr

100 g

to

1 mg

2 yr

20 kg

to

1 kg

4 yr

100 g

to

1 mg

2 yr

1 kg

to

1 mg

4 yr

100 g

to

1 mg

2 yr
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Parameter 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032

Mass

Echelon III

25 kg

to

100 mg

4 yr

50 lb

to

0.001 lb

4 yr

500 lb

6 yr

25 kg

to

100 mg

4 yr

50 lb

to

0.001 lb

4 yr

25 kg

to

100 

mg

4 yr

500 lb

6 yr

Volume

Echelon I

5 gal

slicker

4 yr

100 gal

prover

6 yr

1 qt to 

1 gi

glass

4 yr

1 L to 

100 mL 

glass

4 yr

5 gal

slicker

4 yr

1 qt to 1 

gi

glass

4 yr

100 gal

prover

6 yr

5 gal

slick

er

4 yr

1 L to 

100 mL 

glass

4 yr

Volume

Echelon II

5 gal

test

measur e

2 yr

100 gal

prover

6 yr

5 gal

test

measur e

2 yr

5 gal

test

measure

2 yr

5 gal

test

measure

2 yr

100 gal

prover

6 yr

5 gal

test

meas

ure

2 yr

Length

18 in

ruler

4 yr

100 ft tape

4 yr

18 in 

ruler

4 yr

100 ft tape

4 yr

18 in

ruler

4 yr

Temperature

All Echelons

thermo-

meter

4 yr

thermo-

meter

4 yr

Frequency

tuning fork

4 yr

tuning

fork

4 yr

tunin g

fork

4 yr

Time

stop-

watch

4 yr

stop-

watch

4 yr

stop-

watch

4 yr

Hydrometers

hydrom

eter

4 yr

hydromete r

4 yr
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6. Appendices (duplicated from NISTIR 7214)

Form 1: OWM PT Feedback and Inquiry and Complaint Form

Form 2: OWM PT Participation Request – Training/Qualification Form

Form 3: RMAP Associate Membership Application

Form 7: Examples of Proficiency Test 4-Year Plan and History/Log