Improved capacitance measurements with respect to a 1-pF cross-capacitor from 200 to 2000 Hz

This paper describes frequency dependence measurements of fused-silica capacitance standards from 200 to 2000 Hz, using a 1-pF cross-capacitor as the reference. The measured frequency dependence of fused-silica capacitors was found to vary significantly, ranging from a change of less than 0.2 μF/F for one standard to a change of 0.8 μF/F for another over the frequency range. Increasing capacitances with decreasing frequency from 1592 Hz for all tested fused-silica capacitors indicates that dielectric relaxation due to dielectric bulk and/or interfacial defects is the dominant source of frequency dependence. The relative combined standard uncertainty at 200 Hz (the largest in the frequency range) is 0.07 μF/F, which is smaller by about a factor of three than the uncertainty reported previously from the National Institute of Standards and Technology (NIST).