HT instruments M70 - Manual (Page 13)

M70
EN - 12
4.6. M
:
INSULATION RESISTANCE MEASUREMENT TEST VOLTAGE 250V,
500V, 1000V DC
The measurement is performed according to IEC/EN61557-2 and VDE 0413 part 1.
CAUTION
 Before performing the insulation test make sure that the circuit under test is
not energized and all relative loads are disconnected.
 The insulation measurement requires particolar care and attention to avoid
providing wrong test results and causing damages to third parties.
 Before the insulation test prepare the plant adequately by disconnecting
everything must not be tested. During the insulation test continuously make
sure that the applied voltage is not accessible to third parties.
 A measurement with a cable disconnected by mistake may provide a good
result also in presence of a faulty insulation. It’s necessary to take all
possibile cares to avoid that. Once prepared the plant and connected the
measuring cables, make sure that they are correctly connected. In case of
doubt, bifore performing an insulation test, perform a
 0.2A measurement
by short-circuiting the cables under test at a point of the plant which is as
far as possibile from the measuring clips. Remove the short circuit before
performing the insulation test.
Fig. 8: Connection of the instrument’s terminals during M  test
1. Turn on the instrument
2. Press the arrow keys to select M 
3. Insert the black and red cables in the corresponding input terminals of the instrument,
If the cable length is not sufficient for the measurement extend the black one with an
adequately insulated cable, as its insulation is in parallel to the resistance to be
measured. It must be suspended and not laid to earth and all supports must be of
insulated material
4. If necessary insert the croco clips on the test probes
5. Disconnect the circuit or the part of plant under test from power and all eventual loads
6. Connect the instrument’s terminals to the end of the conductors on which the
insulation test must be performed (see Fig. 8)
7. GO
Press GO to start the measurement for the set time (see par. 4.6.1). Press
GO
to stop the measurement before the end of the set time