Sockets and
terminals
Risks of inadvertent
hand or finger contact with any live test socket conductor when the equipment
is live need to be reduced. The terminals and test sockets of test equipment
may require shrouding.
Voltage detection
instruments
Instruments used solely for
detecting voltage fall into two categories. These are:
(i) Detectors which
rely on an illuminated bulb (test lamp) or a meter scale (test meter). Test
lamps fitted with glass bulbs should not give rise to danger if the bulb is
broken. It may be protected by a guard. These
detectors require protection against excess current. This may be provided by a
suitable high breaking capacity (hbc or hrc) fuse or fuses, with a low current
rating (usually not exceeding 500 mA), or by means of a current-limiting
resistor and a fuse. These protective devices are housed in the probes
themselves. The test lead or leads are held captive and sealed into the body of
the voltage detector.
(ii) Detectors which
use two or more independent indicating systems (one of which may be audible)
and limit energy input to the detector by the circuitry used. An example is a
2-pole voltage detector, i.e. a detector unit with an integral test probe, an
interconnecting lead and a second test probe. These detectors are designed and constructed
to limit the current and energy which can flow into the detector. The
limitation is usually provided by a combination of circuit design, using the
concept of protective impedance, and current limiting resistors built into the
test probes. These detectors are provided with in-built test features to check
the functioning of the detector before and after use. The interconnecting lead
and second test probe are not detachable components. These types of detector do
not require additional current limiting resistors or hbc fuses to be fitted
provided that they are made to an acceptable standard and the contact
electrodes are shrouded.
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