Dc Voltage Measurements - Extech Instruments 420 User Manual

Operating Instructions
WARNING: Risk of electrocution. High-voltage circuits, both AC and DC, are very
dangerous and should be measured with great care.
1. ALWAYS turn the function switch to the OFF position when the meter is not in use.
2. If "OL" appears in the display during a measurement, the value exceeds the range you
have selected. Change to a higher range.
NOTE: On some low AC and DC voltage ranges, with the test leads not connected to a
device, the display may show a random, changing reading. This is normal and is caused
by the high-input sensitivity. The reading will stabilize and give a proper measurement
when connected to a circuit.

DC VOLTAGE MEASUREMENTS

CAUTION: Do not measure DC 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 "DC" on the display.
3. Insert the black test lead banana plug into the negative COM
jack.
Insert the red test lead banana plug into the positive V jack.
4. 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.
5. Read the voltage in the display.
6 EX420-EU_ENG V3.1 6/09