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Model 187 & 189
Users Manual
3-16
Measuring Current
WWarning
Never attempt an in-circuit current
measurement where the open-circuit potential
to earth is greater than 1000 V. You may
damage the meter or be injured if the fuse
blows during such a measurement.
Caution
To avoid possible damage to the meter or to
the equipment under test, check the meter’s
fuses before measuring current. Use the
proper terminals, function, and range for your
measurement. Never place the probes across
(in parallel with) any circuit or component
when the leads are plugged into the current
terminals.
Current is the flow of electrons through a conductor. To
measure current, you must open the circuit under test,
then place the meter in series with the circuit.
To measure ac or dc current, proceed as follows:
1. Turn off power to the circuit. Discharge all high-
voltage capacitors.
2. Insert the black lead into the COM terminal. Insert the
red lead in an input appropriate for the measurement
range as shown in Table 3-1.
Note
To avoid blowing the meter’s 440 mA fuse, use
the mA/
µ
A terminal only if you are sure the
current is less than 400 mA.
Table 3-1. Current Measurement
Rotary Switch Input Ranges
I or K!
5.0000 A
10.000 A (reading flashes at
10 A, overloads (0L) at 20 A)
#
50.000 mA
500.00 mA
= or x
#
500.00 µA
5000.0 µA