A proficiency testing of weight calibration laboratories in the milligram range

A proficiency testing on the mass calibration of standard weights was carried out among 16 laboratories under the JCSS accreditation scheme run by the NITE. The NMIJ/AIST which act as the reference laboratory, has prepared 3 sets of stainless steel weights with nominal values of 200 mg, 20 mg and 2 mg. To evaluate the mass stability of the traveling standard weights, the calibrations of the 18 weights have been made 13 times in the course of the testing. The performance of the participating laboratories is evaluated using E. numbers. It has been confirmed that 15 laboratories have sufficient measurement capability in the milligram range. Only one outlier was a calibration result of a 200 mg weight reported by a participating laboratory.