Ac Voltage Measurements; Dc Current Measurements - Extech Instruments EX420-NIST User Manual

AC VOLTAGE MEASUREMENTS

WARNING: Risk of Electrocution. The probe tips may not be long enough to contact the live parts
inside some 240V outlets for appliances because the contacts are recessed deep in the outlets. As
a result, the reading may show 0 volts when the outlet actually has voltage on it. Make sure the
probe tips are touching the metal contacts inside the outlet before assuming that no voltage is
present.
CAUTION: Do not measure AC voltages if a motor on the circuit is being switched ON or OFF.
Large voltage surges may occur that can damage the meter.
1. Set the function switch to the green V position.
2. Press the SELECT button to indicate "AC" on the display.
3. Insert the black test lead banana plug into the negative COM jack.
Insert red test lead banana plug into the positive V jack.
4. Touch the black test probe tip to the neutral side of the circuit.
Touch the red test probe tip to the "hot" side of the circuit.
5. Read the voltage in the display.

DC CURRENT MEASUREMENTS

CAUTION: Do not make current measurements on the 20A scale for
longer than 30 seconds. Exceeding 30 seconds may cause damage to the meter and/or the test
leads.
1. Insert the black test lead banana plug into the negative COM jack.
2. For current measurements up to 4000µA DC, set the function
switch to the yellow µA position and insert the red test lead
banana plug into the µA/mA jack
3. For current measurements up to 400mA DC, set the function
switch to the yellow mA position and insert the red test lead
banana plug into the µA/mA jack.
4. For current measurements up to 20A DC, set the function switch
to the yellow 20A range and insert the red test lead banana plug
into the 20A jack.
5. Press the SELECT button to indicate "DC" on the display.
6. Remove power from the circuit under test, then open up the circuit
at the point where you wish to measure current.
7. Touch the black test probe tip to the negative side of the circuit.
Touch the red test probe tip to the positive side of the circuit.
8. Apply power to the circuit.
9. Read the current in the display.
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EX420-EU-EN v3.3 08/13