A method of connection used with an alternating-current bridge circuit that minimizes the admittance to earth of the bridge. The earth connection is formed by means of the centre tapping of a three-terminal adjustable resistor, R, in parallel with the a.c. supply (see diagram). The input of the a.c. supply is usually transformer-coupled. If frequencies greater than the audiofrequency range are involved an adjustable capacitor, C, is also used as shown. The indicating instrument, I, is connected across the bridge with a two-position switch. The bridge is balanced with the switch in position B and then rebalanced, using R and C, in position G. The original balance is then rechecked.

Wagner earth connection