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We measured the frequency dependence of a 10 pF transportable fused-silica capacitor from 50 Hz to 20 kHz. The results have a relative standard uncertainty of 0.32x10^(-6), 0.15x10^(-6), and 0.37x10(-6) at 100 Hz, 400 Hz, and 20 kHz, respectively. This will lead to improvements in the capacitance calibration services at NIST by a factor of three or four. For this work, we used two reference capacitors. The first reference was a 1 pF cross capacitor chosen for its negligible frequency dependence at low frequencies. (Conventional capacitors are frequency dependent at low frequencies because of films on electrode surfaces.) The second reference was a 10 pF nitrogen-filled capacitor chosen because it has a very small inductance, thereby reducing problems at higher frequencies.
Wang, Y.
(2003),
Frequency dependence of capacitance standards, Review of Scientific Instruments, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=31304
(Accessed December 12, 2024)