To measure the loss factor of dielectrics as well as the insulation of complete HV
equipment, the classical Schering bridge is commonly applied (Schering 1919). In
principle, this is composed of a measuring and a reference branch, as illustrated in
Fig. 5.8. The HV arm of the measuring branch, being formed of the capacitance
CX in series with the hypothetical resistance Rx of the test object, is grounded via
the tunable resistor R3 providing the LV arm. The HV arm of the reference divider
being formed by the loss-free standard capacitor CN is grounded via a parallel
connection of the resistor R4 and the tunable capacitor C4, both forming the LV
arm.