When connected to the circuit to be tested the three status LED’s will
show the following supply connection information:
LED Normal Reversed Notes
indicator supply (L-N) supply
=ON = OFF
L - PE Voltage between L- PE
greater than 25 V
L - N Voltage between L-N
greater than 25 V
N - PE Voltage between N-PE
greater than 25 V
Warning: Voltage indicator LED’s cannot reveal a N-PE supply reversal
Polarity indication
If connected to a single phase power supply by a plug or by the 3-wire
lead set, three LED’s marked L-PE, N-PE and L-N will indicate supply
polarity
Note: The presence of a voltage between phase and earth does not prove
earth continuity, as the earth could have a high resistance and a voltage
would still be measured. To test earth continuity refers to the sections on
loop testing.
LOOP TESTING
11
Two loop testing options are available: [No Trip] and [Hi].
Non-tripping loop test [No Trip]
Earth loop impedance measurement (at a power socket):
The [No Trip] range is a high resolution (0,01 Ω), low test current earth
loop resistance measurement range. It requires a connection to neutral, but
allows quick and accurate measurement of the earth loop resistance
without tripping all RCDs with a rated current 30 mA or higher.
To perform a [No-Trip] loop test:
Range selection:
1. Select the [No Trip] test range. A non-trip loop test is confirmed on the
display with the symbol
2. On the LT320/LT330 set the top rotary knob to [Z]
Testing:
1. Connect the mains plug test lead to the instrument.
2. Insert the plug into an installation socket.
3. Supply voltage is displayed.
4. Press the [TEST] key.
5. After a test period of up to 20 seconds the measured loop value is
displayed.
If desired the test can be repeated by pressing [TEST] again.
Using the three wire lead set
The [No Trip] loop test can be carried out where a power socket is not
available using the three wire lead set.
1. Connect the RED lead to Phase, BLACK lead to neutral and GREEN lead
to earth.
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