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NIST Handbook 143 |
| | Measurement Control | Reference Standard | Minimum Traceability | Calibration Methods |
| I Gravimetric | · Process control charts · Check standards · Surveillance of all standards used to provide measurement services · Proficiency testing -On site assessment -Round robin participation | Appropriate mass standards · ASTM Class 2 or 3; or · OIML Class F1 or F2; or · Calibrated Balance | · NIST, or national level calibration periodically, based on independent historical data verification or · Test of weighing equipment using correct methods of calibration and adjustment with traceable mass standards | · Documented comparison calibration procedure or · NIST Handbook 145, double substitution (for example) or · Use of calibrated balance |
| II Volume Transfer | · Process control charts · Check standards · Surveillance of selected standards · Proficiency testing -On site assessment -Round robin participation | Primary volume standards with accuracy and repeatability characteristics acceptable for the type of service provided | · Original NIST calibration and periodic independent verification or · Calibration by accredited or recognized Echelon I laboratory, if uncertainty requirements can be met | Documented volume transfer (or water draw) procedure recognized by NIST, OIML, ASTM, or API |