Pressure Coefficients of Air Dielectric Capacitors

摘要

Normally, precision nitrogen dielectric or fused silica dielectric standard capacitors are used to transfer capacitance values from national metrology institutes such as the National Institute of Standards and Technology (NIST). Recently, NIST has adopted a measurement technique for extrapolating 1 kHz values of capacitance to 10 MHz. The technique employs the use of a specific design of air dielectric capacitance standard that is subject to differences in value depending on the atmospheric air pressure. This paper describes a series of measurements used to determine and correct for pressure differences of these air dielectric capacitors. The uncorrected values are observed to be in error by approximately 90 ppm for an elevation difference of about 1500 m between NIST and Sandia National Laboratories. This paper will address the pressure correction, how the user can correct for differences and how uncertainties are obtained. A more accurate transfer of capacitance results from the application of the correction.