Insulation Resistance Measurements - Extech Instruments MG310 User Manual

INSULATION RESISTANCE MEASUREMENTS
CAUTION
 Before taking measurements disconnect the unit under test from all power sources and isolate it
from any stray resistance.
 Do not short circuit the test leads when voltage is output from the meter.
 Allow sufficient time between tests for devices under test to stabilize.
 When red and black clips are connected to the circuit under test, high voltage is output from the
LINE jack and current from the EARTH jack.
 At the completion of a test, do not touch any parts of the circuit under test. Components may have
become charged during the test and could discharge when touched.
1. Select the desired test voltage using the rotary function switch. Select the 250V, 500V, or
1000V switch position for the corresponding output test voltage.
2. Connect the red test lead to the meter's LINE (4) jack and the black test lead to the EARTH
(1) jack. Connect the probe end of the test leads to the circuit under test.
3. Press the TEST button to test. The
button will self‐lock and the button
lamp will light.
Note: If the circuit under test is live
and has a voltage potential (AC/DC)
over 30V, the meter will not test (the
display will show the ">" icon and
the symbol will flash; the buzzer
will also sound). If the circuit under
test is not live or if its voltage is less
than 30V, the meter will begin
applying high‐voltage to the circuit
under test.
4. The primary display will show the
insulation resistance in MΩ
(megaohms) or GΩ (gigaohms).
5. The test voltage (VDC) value will be
indicated in the right‐most auxiliary
display, the symbol will flash and the caution buzzer will sound.
6. Press to release the TEST button to stop the test. The high voltage will switch off and the
resistance value indicated in the primary display will hold.
7. Subsequently, the meter will internally discharge the balance of the insulation test voltage.
Note: Turning the function switch to another test position will abort the test.
8. A reading of >5.50 GΩ indicates that the meter reading is above the resistance threshold of
that measurement range.
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