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9. Insulation resistance testing - general
Safety note:
Insulation resistance
testing is performed at high DC voltages and is hazardous if
touched. Always observe the safety precautions when performing an insulation
resistance
test, and ensure all necessary health and safety precautions are observed.
Automatic Discharge:
Capacitive circuits are automatically discharged when the test button
is released following an insulation test.
The circuit under test
must be
completely
de-energized
and securely
isolated
before test
connections are made.
9.1
Standard insulation resistance testing
(Refer to Figure 6)
Note:
For MIT40X refer to section 10.
1.
Connect the test probes to the isolated circuit under test.
2.
Turn the instrument ‘ON‘ by rotating the selector switch to the desired test voltage (50
V, 100
V 250 V, 500 V or 1
kV).
3.
Press and hold the [TEST] button to start the test.
4.
The insulation resistance value, in both analogue and digital form is displayed together
with the actual test voltage displayed on the secondary display (see Screen A of figure
6).
5.
The insulation test can be locked on, by pressing the lock button [
] whilst holding
down the [TEST] button. To disable lock press the [TEST] button or lock [
] button.
6.
By pressing the [uA/V/s] button, the leakage current can be displayed (see Screen B).
Not available on the MIT400 or MIT480.
7.
Release the [TEST] button before removing the test leads (to enable the instrument to
discharge the circuit under test). If the display shows VOLTS, wait until it reaches zero.
8.
On completion of testing, switch to the ‘
OFF
’ position. Alternatively
auto shut-off
operates after 15 minutes of inactivity.
