Precision computer-controlled decade capacitor

A precision computer-controlled decade capacitor is described that is capable of switching capacitances from 100 pF to 1 μF in steps of 100 pF. These capacitances can be realized with a relative uncertainty of better than 1×10^-4 and repeated selection of a given capacitance can be achieved with a relative uncertainty of the order of 1×10^-6. To minimize temperature dependence of the capacitances, special ceramic capacitors with temperature coefficients of the order of 1×10^-6 K and low loss factor are used. The effect of switching impedances is minimized by a four terminal-pair definition of capacitors and quasicoaxial connection. The capacitor can be used for automatic calibrations of capacitance bridges with relative uncertainties in the range of 1×10^-6 to 1×10^-4