Guard Circuit

TM 11-6625-298-14

Figure 5-6. Functional diagram.

5-7. Guard Circuit

The guard circuit prevents leakage current along

the surface of the instrument case between the

The guard circuit as shown in figure 5-6 increases

ground terminal and the line terminal from af-

the accuracy of the instrument by preventing

fecting the meter readings. Leakage current to the

leakage when making measurements over 100

line terminal is picked up by the guard ring and

megohms. The guard circuit consists of a metal

led directly to the generator without going through

ring around the line terminal and metal plates on

resistor R1 and the meter coils.

which resistor R1, R2, and R3 are mounted. A

brass tube connects the ring and plates together.