22 GMC-I Messtechnik GmbH
8.2 Measurement with Manual Polarity Reversal
– MAN Function
In order to determine whether or not the obtained results are inde-
pendent of current flow direction, measurement can be per-
formed separately for both directions.
Ð Press the
scroll keys to this end, depending upon the de-
sired current flow direction:
MAN and or MAN and appear at the display.
Ð Start individual measurement by briefly pressing the START
key.
DATA blinks at the display until the measured value has settled in.
Differing results indicate voltage at the device under test (e.g.
thermovoltage or unit voltages).
Measurement results can be distorted by parallel connected
impedances at load current circuits and by equalizing current,
especially in systems which make use of “overcurrent protection
devices” (previous neutralization) without an isolated protective
conductor. Resistances which change during measurement (e.g.
inductance), or a poor contact, can also cause distorted mea-
surements.
Examples of resistances whose values may change during mea-
surement include:
– Incandescent lamp resistance with changing values caused
by warming due to measuring current
– Resistances with a large inductive component
In order to assure unambiguous measurement results, causes of
error must be located and eliminated.
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