Expansion of the measurement range of AC shunt resistor standard

There has been a demand for accurate measurements of ac shunt resistors with a nominal value of 1 mS or less for both in-phase and quadrature components. Thus, to expand the ranges of impedance and frequency of the calibration system for ac shunt resistors, a current bridge method with cascaded current transformers (CTs) has been developed. An ac shunt resistor with nominal value of 10 mS was evaluated by a current bridge method using cascaded CTs, and the results of the calibration system using this method were validated. It was found that the calibration system for ac shunt resistors using the current-bridge method with cascaded CTs can be used successfully for both in-phase and quadrature components up to 3 kHz.