KYORITSU 4120A - Manual (Page 11)

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(3) Voltage Measurement
When the instrument is first connected to the system, it will display the
phase-neutral voltage which is updated every 1s. This mode is cancelled
whenever the test button is pressed. If this voltage is not normal or as
expected, DO NOT PROCEED.
5.2 Measurement of the Loop Impedance
(1) Set the instrument to the 200Ω or 2000Ω range.
If the instrument is set to the 20Ω range slight sparking may occur
when testing with the distribution board lead although the unit has
been designed to minimize this.
(2) Connect the lead to the instrument.
(3) Plug the moulded mains plug to the socket being tested.
(4) Check the LED's are lit as indicated in section 5.1. If not DO NOT
PROCEED - check wiring.
(5) Note the mains voltage if required.
(6) Press the "Press to Test" button. The value of loop impedance will be
displayed with the appropriate units. A bleep will sound on completion
of the test.
For best results always test on the lowest possible range.
For example, a loop impedance measured on the 200Ω range may
give an indication of 0.3Ω whereas on the 20Ω range it may read 0.28
Ω. In the event of the reading being in excess of the range (e.g. more
than 20Ω on the 20Ω range) the appropriate over-range symbol "OL"
will appear on the display.
No harm will be done to the instrument by selecting too low a range.
WARNING
● If the above sequence is NOT displayed or the RED LED is on for
any reason , DO NOT PROCEED AS THERE IS INCORRECT
WIRING. The cause of the fault must be investigated and rectified.
WARNING
● This instrument is intended only for use in single phase operation
at 230V +10% -15% AC phase to earth or for use in OLD-TT
system phase to neutral.