SOLUTION

The Megohm bridge is used to remove the leakage current from bridges. This is done with the help of three terminal resistance as shown in the Fig.

The high resistance is connected between two binding posts which are fixed to the metal plate. The two main terminals of the resistor are connected to the R, terminals in the bridge. The third terminal is the common point of resistances R1 and R2, which represent the leakage paths from the main terminal along with the insulating post of the metal plate. The guard is connected to the guard terminal on the front panel of the bridge.