3
G
LIVE EARTH SAFETY PRECAUTIONS
It is preferable that the earth electrode to be tested is first isolated from the circuit it is protecting, so that only the earth is measured and not the complete
system. When this is done, the circuits and equipment must be de-energised. If however this is not possible, the earth electrode should be duplicated so that
when it is disconnected for test purposes, the other one provides the necessary circuit protection. The following safety precautions are essential when
working near high tension systems where any unintentional ‘live’ earths may be encountered between the site earth and remote earths established for test
purposes. A ‘live’ earth is one that carries current from the mains supply, or could do so under fault conditions.
1. All persons involved must be trained and competent in isolation and safety procedures for the system to be worked on. They must be clearly instructed
not to touch the earth electrode, test spikes, test leads, or their terminations if any ‘live’ earths may be encountered. It is recommended that they wear
appropriate rubber gloves, rubber soled shoes, and stand on a rubber mat.
2. The ‘P’ (‘S’) and ‘C’ (‘H’) terminals should be connected through a double pole isolation switch, the rating of which will cope with the maximum fault
voltage and current. The isolation switch must be open whilst any personal contact is made with the remote test spikes, or the connecting leads, e.g.
when changing their position.
Note:
If a fault occurs while a test is being made the instrument may be damaged. Incorporating fuses at the isolation switch, rated at 100 mA, and able to
cope with the maximum fault voltage will provide some protection for the instrument.
BATTERY INSTALLATION
Caution:
Whenever battery cells are being fitted or replaced, there should be no connections to the instrument terminals. The cover to the battery
compartment lifts off the rear of the instrument and is held in position by a single captive screw in the base of the instrument. To fit or replace battery cells,
loosen the captive screw and lift away the cover. Fit new cells observing the correct polarity as indicated on the battery compartment moulding. Replace the
cover and tighten the securing screw. To avoid damage by leaking electrolyte, do not leave cells fitted in an instrument which will remain unused for
extended periods of time.
