Unsuitable test
probes, leads, lamps, voltage indicators and multimeters have caused arcs due
to:
(a) Inadequately
insulated test probes (typically having an excessive length of bare metal at
the contact end) accidentally bridging a live conductor and adjacent earthed
metalwork; or
(b) Excessive current
drawn through test probes, leads and measuring instruments. This happens when a
multimeter is set to the wrong function, eg set on a current or resistance
range when measuring voltage.
(c) Inadequate
insulation of test leads and probes;
(d) Exposed live
terminations at instruments and indicators;
(e) A lead falling off
one of the terminals of a meter and either the meter terminal or the lead
terminal remaining live;
(f) Incorrect use of
test equipment, eg a multimeter applied to conductors at a voltage which
exceeds the maximum working voltage of the instrument;
(g) Use of poorly
constructed makeshift test equipment, eg a test lamp consisting of a
combination of a bayonet lamp holder, bulb and two single insulated conductors
with bared ends;
(h) Use of long
intertwined leads which were not easily distinguished, resulting in one lead
being connected across the instrument and the other short circuiting the live
conductors under test.
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