Utilization Of The Guard Terminal (Model 6503) - AEMC 6503 User Manual

4.5 Utilization of the Guard Terminal
C
Guard terminals are useful when measuring high resistance values
and for stabilizing readings.
When testing the insulation at the end of a cable, it is necessary to
eliminate the error from surface leakage which occurs, particularly
at high resistance values. The purpose of the guard terminal is to
provide a third terminal within the path of the surface leakage "D".
Connect the instrument as shown in Figure 4-1.
If there is no shield at "B", use a copper wire wound several times
around the exposed surface "B". (Note: If a shield is not available
and you do not make up a shield around "B" and connect to the
guard terminal (-), the measurement will be erroneous and lead to
confusion as to the cable's state.)
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Megohmmeter Models 6501/6503
D
B
G
Figure 4-1
GlobalTestSupply
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(Model 6503)
A
A = Insulation
B = Shield
C = Conductor
D = Exposed surface
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