Technology Services, Weights and Measures Division, NIST

NIST Handbook 143
State Weights and Measures Laboratories Program Handbook


Table 8. Summary of Technical Criteria for Mass Calibration

Echelon
Minimum Measurement Control
Minimum Reference Standards
Minimum Traceability
Minimum Calibration Methods
I

(Extra Fine)

 · Process control charts

· Check standards for each decade, with long term standard deviation

· Surveillance of all standards

· Proficiency Testing

-on-site assessment

-round robin participation 

 · OIML Class E1, or E2 or

· ASTM Class 1, 1.1, Type 1, Grade S; or

· single piece, highly polished

 · NIST, or other national level calibration every 2-5 years based on measurement process data and independent verification, or

· NIST Mass MAP, or

· User operated mass calibration package, on-site to verify traceability (when available).

 · Documented weighing designs consisting of redundant comparisons, with built-in process controls such as those used at the national level. 

For example:

· Technical Notes, 952 and 844
II (Fine)
 · Process control charts

· Check standards for each decade, with long term standard deviation

· Surveillance of selected standards

· Proficiency Testing: on-site assessment, round robin participation 

 · OIML Class E1, or E2

· ASTM Class 0, 1; or

· single piece, highly polished

 · NIST calibration every 2 - 5 years based on measurement process data and independent verification, or

· Calibration by accredited or recognized Echelon I laboratory, if uncertainty requirements can be met.

 · Documented comparison calibration procedure

For example:

· NIST Handbook 145, double substitution, or 3-1 weighing design, or equivalent

III (Medium)

 · Process control charts

· Check standards for each balance 

· Proficiency Testing

-on-site assessment

-round robin participation 

 Working standards such as:

· ASTM Class 2, 3

or

· OIML Class F1

· two piece acceptable, fine finish

 · Calibration of all working standards by NIST every 2 - 5 years based on measurement process data and independent verification, or 

· Calibration of all working standards by an Echelon I or II accredited or recognized labs every 2 - 5 years based on measurement process data and independent verification.

 · Use of annually calibrated balance with documented verification procedure prior to each use

· Use of modified substitution (NIST Handbook 145)

· Other documented and verified procedure

 

Program questions: Weights and Measures

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