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8-3 Output voltage characteristics
This instrument conforms to IEC61557. This standard defines
that the nominal current shall be at least 1mA, and the lower limit
of the insulation resistance maintaining the nominal voltage at
the measurement terminal. (See the graph below.) This value is
calculated by dividing the nominal voltage by nominal current. i.e.,
in case that the nominal voltage is 500V, the lower limit of the
insulation resistance is found as follows.
Divide 500V by 1mA equals 0.5MΩ.
That is, insulation resistance of 0.5MΩ or more is required to provide
the nominal voltage to the instrument.
Nominal voltage
250V
500V
1000V
Lower limit of the insulation resistance
to provide the nominal current of 1mA
0.25
MΩ
0.5
MΩ
1
MΩ
Fig. 8-5
