A digitally programmable capacitance standard

We constructed a digitally programmable capacitance standard by modifying a commercial temperature-stabilized 100 pF capacitance standard which consists of 23 binary-weighted capacitor elements on a single fused-silica disk. The variable capacitor can be programmed through a computer from 0.000 115 4 to 113.046 496 4 pF with a resolution smaller than 0.000 115 4 pF over the entire range. Using selected combinations, we also demonstrate a method to calibrate the 23 capacitor elements against a 10 pF capacitance standard.