In-house Intercomparison of MJTCs for Assigning AC/DC Transfer Difference to National Standard of LF Voltage and Current at CSIR-NPL India

Abstract

Multijunction thermal converters (MJTCs) are used worldwide by the leading NMIs (National Metrological Institute) as primary Standard for the establishment of low frequency (LF) AC voltage and current parameters. The MJTC is an electrothermic device that works on the principle of Joule’s heating law. At NPLI (National Physical Laboratory, India), we have kept a bank of four MJTCs with identical characteristics. The AC–DC transfer difference of these MJTCs is determined over a frequency range of 10 Hz–1 MHz. The operating range of MJTC is 2 V and 5 mA. The uncertainty in assigning AC/DC transfer difference varies from ± 5 ppm to ± 25 ppm for both voltage and current range. This paper presents the in-house intercomparison of MJTCs to evaluate relative AC/DC transfer difference for establishment of primary standard of LF voltage and current.