Fluke 78 - N, Adhow to Measure Current

78
Users Manual
18
N, \ How to Measure Current
Warning
To avoid electric shock or personal injury
• Never attempt an in-circuit current meas-
urement where the open-circuit potential
to earth is greater than 300 V.
• Before measuring current , check the me-
ter’s fuses (see “How to Test the Fuse”).
• Turn off circuit power before connecting
the meter in the circuit. Remember to
place the meter in series with the current.
• Use proper terminals, function and range
for your measurement.
• Always use clamp-on probes (dc current
clamps) for circuits of more than 10 A.
• Install ONLY specified replacement fuses.
Current is the flow of electrons through a conductor. To
measure current:
1. Turn off power to the circuit and break the circuit. (To
measure current without breaking the circuit, use a
current clamp.)
2. Insert the test leads into the 10 A and COM jacks.
3. Turn the rotary switch to
N. To toggle to a, press
R for 2 seconds.
4. Clip the red test lead to the side closest to the power
source and clip the black test lead to the side closer
to ground.
This puts the meter in series with the circuit being
tested and all current flows through the meter.
Always
measure current with the meter in series with the cir-
cuit under test.
5. Turn ON power to the circuit and read the display.
Figure 7 shows how to isolate a circuit causing current
drain.