(a) PM balance calibration weights. Use PM balance calibration weights that are certified as NIST-traceable within ±0.1% uncertainty. Make sure your highest calibration weight has no more than ten times the mass of an unused PM-sample medium.
(b) Dynamometer, fuel mass scale, and DEF mass scale calibration weights. Use dynamometer and mass scale calibration weights that are certified as NIST-traceable within ±0.1% uncertainty.
[70 FR 40516, July 13, 2005, as amended at 76 FR 57467, Sept. 15, 2011; 86 FR 34574, Jun. 29, 2021; 88 FR 4687, Jan. 24, 2023]