IMPROVEMENT OF MEASUREMENT CAPABILITIES OF MULTIPLE MASS STANDARDS OF 1 kg AT NPLI

Goutam Mandal, C. K. Gopan

Abstract

The National Physical Laboratory, India (NPLI) is the custodian of National Prototype of the Kilogram (NPK) No. 57, which was provided by the International Bureau of Weights and Measures (BIPM), Paris, France in 1958 after its first calibration in 1955. The NPK has been recalibrated three times (1985, 1992 & 2002) so far at the BIPM. All NPL working standards (Multiples & sub-multiples of 1 kg) range from 1 mg to 20 kg are reestablished using new value of NPK through four Transfer Standards of 1 kg (two made of Stainless steel and two made of Nickel-Chromium alloy) according to defined periodicity. <br />The calibration of multiples of 1 kg is carried out using a fully automatic mass comparator with maximum capacity of 64 kg and resolution of 0.1 mg. Using this mass comparator, we have improved our calibration and measurement capabilities (CMCs) from 0.6 mg to 0.2 mg (<i>k</i> = 2) in 2 kg, from 1.5 mg to 0.3 mg (<i>k</i> = 2) in 5 kg, from 3 mg to 0.5 mg (<i>k</i> = 2) in 10 kg and from 6 mg to 1.0 mg (<i>k</i> = 2) in 20 kg. The details of measurement technique and results of multiples of 1 kg are discussed in this paper.

Keywords

subdivision and substitution method

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IMEKO TC

TC3 - Measurement of Force, Mass, Torque, and Gravity

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