Phase to Neutral or Earth loop impedance measurement -
Power plug method
1. Select (Loop) L-PE or L-N as required.
2. Insert the plug into an installation socket.
3. Supply voltage and polarity are displayed.
4. Press the
TEST key.
5. Measured loop value is displayed.
On completion of this test, prospective fault current can be
displayed by pressing the
DISPLAY key.
If desired the test can be repeated by pressing
TEST again.
Phase-Earth loop impedance measurement-Two wire method
If an installation socket is not available, use the the 2-wire lead set.
1. Select
(Loop) L-PE.
2. Connect the red lead to phase and the black lead
to earth. No connection to neutral is required.
3. Supply voltage is displayed.
Note:- Though displayed,
polarity indications are invalid with the two wire lead set
and should be ignored
4. Press the
TEST key.
5. Measured loop value is displayed.
On completion of this test, prospective fault current can be
displayed by pressing the
DISPLAY key.
If desired the test can be repeated by pressing
TEST again.
Bonded Metalwork Testing (1)
This test is performed using the two wire lead set.
1. Connect the black lead to the bonded metalwork.
2. Connect the red lead to phase.
3. Select (
Loop) L-PE
4. Supply voltage is displayed.
5. Press the
TEST key.
6. Measured resistance value is displayed.
Bonded Metalwork Testing (2)
This test can also be performed using the optional earth bond
test lead, allowing connection to an installation socket.
1. Connect the black flying test lead to the bonded metalwork.
2. Insert the power plug test lead into a socket (receptacle).
3. Select
(Loop) L-PE.
4. Supply voltage is displayed.
5. Press the
TEST key.
6. Measured resistance value is displayed.
Operation (Contd).
16
Automatic testing
To aid rapid testing, the CM500 can be set to start a test
automatically when connected to the supply. This may be of
use, for example, when using a clip and a probe. Select the
range required and press the test key without the supply
present. The instrument will display
<100 V for approximately
30 seconds. Apply the supply voltage within this time and the
instrument will pause before performing one test
automatically.
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