Development of an automated AC-DC transfer measurement system for voltage and current at low frequencies

National Physical Laboratory India (NPLI) is the premier research & development center and the National Metrology Institute, which provides traceability in measurements by calibration throughout the country. Low Frequency voltage and current are very important quantities in electrical metrology. The standards for LF voltage and current are established by assigning AC-DC transfer difference to Thermal Converters (TCs) worldwide. The range of frequencies of these standards is from 10 Hz to 1 MHz for the voltage level of 1 V to 1000 V. This paper presents the automation of method of assigning AC-DC transfer difference to thermal converter (from 10 Hz to 1 MHz) makes measurements faster and more accurate through IEEE-488 interface card and cables. The software for this process has been developed using the VEE Pro application, which is a graphical programming environment optimized for use with the electronic instruments. It also minimizes the human involvement and therefore reduces the chances of errors. Using this software, the measurements have been carried on the 6 V TC with respect to 4 V TC at 4 V level in the frequency range from 10 Hz to 1 MHz. The result shows that the automation has been done successfully.