Characterization of an Automated Permuting Capacitive Device for AC Voltage Ratio Calibration

A permuting capacitive device (PCD) system has been developed for high-precision calibrations of ac voltage ratio. The PCD consists of 12 capacitors with an adjustable capacitance feature and a coaxial multiplexer for auto-permutation. The PCD capacitors exhibit good stabilities of both short and long terms, and all of their capacitance values lie within $\pm 30\times 10^{-6}$ . After a thorough evaluation, the PCD was applied to voltage ratio measurements of inductive voltage dividers (IVDs). The 10:1 voltage ratio value of an IVD, obtained using the PCD at 1 kHz, was in accordance with a reference value to a level of $10^{-8}$ . The measurement uncertainty was analyzed to be about $35\times 10^{-9}$ ( $k =1$ ) at 1 kHz. Reliability of the PCD was further verified across a frequency range from 50 Hz to 20 kHz through 10:1 capacitance ratio measurements using a digital impedance bridge with the calibrated IVD.