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Chapter 4 Measurement Procedure
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CAUTION
If the measurement button (
PRESS ON
)is
depressed, earth voltage cannot be measured. The
needle of the galvanometer may fluctuate or
register to the end of the scale. This is not a defect.
If there is an earth voltage of more than 10 V, the
earthing body should be isolated from the electrical
installation and power line switches or similar
should be turned off in order to minimize the earth
voltage for measurement. Also, if the earth voltage
is high, a risk of electric shock exists and proper
precautions should be taken.
(4) Earth voltage check
Set the range selector to
V to check for the
presence of earth voltage. Do not press the
measurement button (
PRESS ON)atthistime.
(5) Auxiliary earthing resistance check
The 3151 has a function for checking the
auxiliary earthing resistance. Be sure to
perform this check before measuring earthing
resistance.
The check result should be evaluated as
follows: The more the needle of the
galvanometer deflects to the left, the higher is
the auxiliary earthing resistance. (If the needle
remains in the vicinity of the zero point,
auxiliary earthing resistance poses no
problem.)
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