15
Connect the mains lead to the IEC socket of the
instrument
Plug the moulded plug of the mains lead into the
socket to be tested
Carry out the initial checks
Press the test button. A beep will sound as the test is
conducted and the value of loop impedance will be
displayed
Wait for the display to indicate the input voltage
before conducting another test or before
disconnecting the instrument from the socket
If the display shows ‘OL’ then this usually means the value mea-
sured exceeds the range selected, e.g. if the 20
Ω
range was
selected then the loop impedance is greater than 19.99
Ω
and
you must switch up a range to the 200
Ω
range.
5.2.1
External Earth Probe
The phase-earth loop impedance of exposed metal
work (e-g. pipes/conduit etc.) can be tested using the
external earth probe.
Connect the unit to the socket as normal. Plug the
external earth probe into the instrument external
earth probe socket, ensuring the probe is held with
fingers behind the finger guard. This will break the
earth continuity at the socket and the red LED will
switch on. The point at which the probe is now
connected becomes the new earth point instead of at
the socket. When the probe is placed in contact with
the earthed surface to be measured, the LED mains
status should revert to the correct sequence described
in initial checks. When this happens, press the test
button to measure the loop impedance.
