Using The Guard Terminal - Circutor MD 5060e Manual De Uso

4.1. Using the Guard terminal

The G (Guard) terminal can be used or not, according to the
measurement that is going to be carried out. During measurements, the
equipment must be electrically referred to earth in order prevent the
equipment from being on a high potential, which may produce unstable
readings. When insulation is measured regarding grounding, the R
terminal is connected to earth and the condition by means of which the
equipment potential setting is fulfilled. If the measurement is performed
between two parts, which are not grounded (for example, between two
phase conductors in a tree-phase cable), the insulation tester Guard
terminal must be grounded. This implies that whenever a measurement
is performed, one of the GUARD or R terminals must be grounded,
but not both of them simultaneously.
The Application Note 32 explains the usage of Guard terminal for
minimizing the parasite resistance effect, whose influence one intends to
minimize.
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