Precise Kelvin Double Bridge for Measuring Dissipation Factors and Capacitances up to 1 F

In a recent paper, an ac bridge was described for measuring capacitances from 1 nF to 1 mF in a frequency range of 50-1000 Hz with a precision of a few ppm. In this paper it will be shown that not only the main ratio arm fed by the high-potential standard leads but also the Kelvin ratio arm fed by the low-potential leads must be adjusted in their complex components if the precision of the comparison in the order of a few ppm is to be achieved for capacitances up to 1 F. It is therefore important that the in-phase errors as well as the quadrature errors of the inductive voltage dividers (IVD) not exceed a few parts in 107. A suitable device coupling the ratios of the IVD's of the main ratio arm and the Kelvin ratio arm can facilitate the adjustment.