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TM 9-254
8-2.
Meter Usage - Continued
Figure 8-1. Proper Voltmeter Connection
(2)
Current measurements (fig. 8-2). When making a current measurement, always connect the current
meter in series with the circuit to be measured. This is necessary because of the fact that all of the
circuit current must pass through a current meter in order to establish the current value in the circuit.
Prior to connecting a current meter, the operator should determine a few basic facts about the circuit.
(a)
Determine if the circuit current to be measured is DC or AC current. Use only DC current meters in
DC circuits. Use only AC current meters in AC circuits.
(b)
When using DC current meters, observe circuit polarity when connecting the meter in series with the
circuit.
(c)
If the quantity of the current to be measured is unknown, always select the highest current range
available on the meter. If the selected range does not give an adequate indication, reduce the
range setting one range at a time until an on scale indication is obtained.
Figure 8-2. Proper Current Meter Connection
(3)
Resistance measurements (fig. 8-3). The ohmmeter is used to measure the amount of resistance in a
circuit or in a circuit component itself. Before using the ohmmeter, the operator should become familiar
with a few basic rules.
(a)
Always disconnect the source of power from the circuit before attempting a resistance
measurement.
8-3
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