1. Program Summary

State legal metrology laboratories are custodians at the State level of measurement standards that serve as the basis for ensuring equity in the marketplace and as reference standards for calibration services for indigenous industry. As part of its program to encourage a high degree of technical and professional competence in such activities, the National Institute of Standards and Technology (NIST) Office of Weights and Measures (OWM) has developed performance standards and formalized procedures for voluntary recognition of State legal metrology laboratories. Certificates of Traceability are issued upon evaluation of the laboratory's ability to make reliable metrological measurements (principally mass, volume, length, and temperature).

Recognition of State Legal Metrology Laboratories

This Handbook describes the procedures followed in evaluating State (and a few other jurisdictional) legal metrology laboratories for competence.  To be recognized, a laboratory must satisfy general and technical requirements for each measurement area in which recognition is desired (see Appendix B).  This program is managed by the Office of Weights and Measures of the National Institute of Standards and Technology.

The general requirements in sections 5 and 6 incorporate ISO Guide 25, ISO Guide 38 and ISO Guide 10012-1 (as stated in the U.S. Standard ANSI/NCSL Z540-1-1994, and as adopted by the NVLAP Calibration Laboratories Accreditation Program) and address internationally accepted quality practices and good management practices for calibration and testing laboratories. In addition to ISO Guide 25 and NVLAP requirements, sections 5 and 6 contain additional general requirements as "notes" that are specific for State legal metrology laboratories. (See Section 8. References.)

The technical criteria amplify general criteria (ISO Guide 25, ANSI/NCSL Z540-1-1994) for each specific measurement parameter as needed. Technical requirements of the NIST/OWM recognition program are identical to the NVLAP guidelines as published in the draft of NIST/NVLAP Handbook 150-2, Calibration Laboratories Technical Guide; however, OWM does not operate a formal accreditation program. The technical requirements include demonstration that: 1) suitable test equipment, calibration standards, defined test procedures, and the general facilities necessary for good metrological services are available; and 2) that staff have a comprehensive understanding of calibration, measurement, and test requirements and are capable of applying them.

Under this voluntary recognition program, laboratories appraise their compliance with the requirements, using appropriate checklists which are reviewed and evaluated by NIST/OWM.

Following review and evaluation, which includes an on-site assessment and proficiency testing, NIST/OWM may issue a Certificate of Measurement Traceability indicating recognized competence areas with defined parameters and scope of recognition; a letter describing the quality system in place in each laboratory is also provided. Recognition may be granted for a period up to 2 years, but on an annual basis each laboratory must review its status, complete an internal audit, including management and quality system review, and submit the evaluation along with a statement that no adverse changes have taken place in order for the recognition to remain in effect.

Types of assistance available from the National Institute of Standards and Technology are listed in Appendix A. List of NIST Services.

General

Each State legal metrology laboratory is encouraged to study this Handbook carefully and to apply for recognition in all areas in which it provides measurement services. NIST/OWM reserves the right to deny or withdraw recognition. In such cases, NIST/OWM will notify the State in writing of deficiencies, and provide guidelines for corrective action.  In the case of withdrawal, NIST will attempt to reach agreement with the State on the timing of the corrective action in order to keep the recognition in force conditionally for legal requirements only.