Precautions during
testing
For voltage
detection or measurement, test leads protected by a fuse (or fuses) are
recommended when voltmeters and in particular multimeters, are used. Although
some multimeters are fitted with electromechanical overload devices, these are
often inadequately rated to deal with short circuit energy present on
electrical power systems. It is usually necessary to use leads which
incorporate high breaking capacity (hbc) fuses even if the multimeter has an
overload trip. If terminal clips are provided for connection to test points,
they should be adequately insulated and arranged to be suitable for use with
the test leads, as a safe alternative to the use of test probes. It is
important that a multifunction or multirange meter is set to the correct
function and/or range before the connections are made. Where there is doubt
about the value of voltage to be detected or measured, the highest range should
be selected at first, provided that the maximum voltage possible is known to
fall within the range of the instrument.
Progressive voltage
detection or measurement is often used to prove circuit continuity. The dangers
from exposed live conductors should be borne in mind when using this method. In
many cases, continuity testing can be carried out safely with the apparatus
dead, using a self-contained low voltage dc source and indicator.
If tong-test instruments are to be used, it is necessary to check first
that there is adequate working space free from danger (ie from bare live
conductors at dangerous voltages) at the place where the instrument will be
held. The tong insulation should always be examined visually before the
instrument is used; if defects are present the instrument should not be used.
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