Typical Testing Applications; G,F How To Measure Voltage - Fluke 78 User Manual

78
Users Manual

Typical Testing Applications

L
K
, How to Measure Voltage
Voltage is the difference in electrical potential (charge)
between two points.
The following procedure demonstrates how to measure
voltage using the example of the no-load voltage of a
battery:
1. Insert the test leads into the jacks (Figure 5).
Turn the rotary switch to L .
2.
Warning
To avoid personal injury or damage to
equipment, never attempt a voltage meas-
urement with a test lead in the 10 A input ter-
minal.
Turn the car lights on for 1 minute to bleed off surface
charge, then turn lights off.
14
3. Touch the probes to the circuit. This puts the meter in
parallel with the circuit. Voltage must be measured
with the meter in parallel with the circuit.
4. Read the voltage. If you reverse the probes when
measuring dc voltage, the display indicates negative
polarity with a minus sign [-]. The no-load voltage
only indicates the state of charge, not the condition of
the battery.
K
Use the function to measure ripple voltage at
the rear of the alternator (not the battery). With
the engine running, a good alternator measures
less than 0.5 V ac. A higher reading indicates
damaged alternator diodes.
Note