Capacitance and loss-factor measuring bridge

摘要

Capacitance and loss-factor measuring bridge, having a differential current transformer which has a first primary winding in a bridge arm having the capacitance to be measured and a second primary winding in a bridge arm having a reference capacitor. When the magnetic fluxes generated by the first primary winding and by the second primary winding cancel each other out, there is a zero indication via an indicator winding on the secondary side. To balance the measuring bridge, the number of effective windings of the second primary winding is changed. A setting resolution, and consequently measuring accuracy, which is finer than that which can be achieved with a turn of the second primary winding is achieved by two further primary windings (N3, N4) of the differential current transformer (DW) by these two additional primary windings each being preceded by an attenuating element ( alpha , beta ), which is fed a current which in the one case is proportional in terms of magnitude and phase to the current flowing through the second primary winding (N2), in the other case is proportional in terms of magnitude and is shifted by 90 DEG in terms of phase. <IMAGE>