S-Parameter Based Evaluation of Cable Losses for Precise Low Frequency Voltage and Current Calibration

LF (low frequency) voltage and current are important parameters in electrical metrology. Evaluation of cable losses has been undertaken to improve measurement accuracy for LF voltage and current calibration at CSIR-National Physical Laboratory India (NPLI). The measurement has been done by measuring its S-parameters using Vector Network Analyzer (VNA) in the frequency domain. Insertion Loss method and Return loss method have been used to validate the VNA based measurement results. This paper presents evaluation of cable losses for two designated coaxial cables. The applied corrections for both these cables have been evaluated in frequency range from 300 to 1 MHz at different LF voltage points. In order to improve LF voltgae and current calibration accuracy and precision in measurements, the coaxial cables must be characterized for their impedances and losses. This paper presents and discusses two different methods used to characterize the coaxial cables.