25
e. Turn the power off and disconnect the test leads.
NOTE: The 10A range is not internally fused in the 260-8.
When using the 10A range, never disconnect a test lead from a jack or from the
circuit while the circuit is energized. Doing so may damage the test jacks or leads
and the arcing may be hazardous to the operator. Turn off circuit power and wait
for the meter reading to drop to zero.
The polarity reversing feature of the function switch does not operate on the 0-
10A range. If polarity is found to be incorrect, turn off circuit power, wait for the
meter indication to reach zero and then interchange test lead connections to the
circuit.
4.16 Resistance Measurements
Voltage applied to a resistance range will cause reading errors if low and dam-
age the Instrument if high. When making in-circuit measurements, make certain
that the circuit is completely de-energized before making connections to it.
When making in-circuit measurements, circuit paths in parallel with the resis-
tance being measured may cause reading errors. Check circuit diagrams for the
presence of such components before assuming that the reading obtained is
correct.
When resistance is measured, the batteries furnish power for the circuit. Since
batteries are subject to variation in voltage and internal resistance, the Instru-
ment must be adjusted to zero before measuring a resistance, as follows:
a. Turn range switch to desired ohms range.
b. Plug the black test lead into the –COMMON jack and the red test lead into the
+ jack.
c. Connect the ends of test leads together to short the VOM resistance circuit.
d. Rotate the ZERO OHMS control until pointer indicates zero ohms. If pointer
cannot be adjusted to zero, one or both of the batteries must be replaced.
(For battery replacement, refer to Section 5.)
e. Disconnect shorted test leads.
4.16.1 Measuring Resistance
a. Before measuring resistance in a circuit, make sure the power is off to the
circuit being tested and all capacitors are discharged. Disconnect shunting
components from the circuit before measuring its resistance.
b. Set the range switch to one of the resistance range positions as follows
(Figure 4-12):
1. Use R X 1 for resistance readings from 0 to 200 ohms.
2. Use R X 100 for resistance readings from 200 to 20,000 ohms.
3. Use R X 10,000 for resistance readings above 20,000 ohms.
c. Set the function switch at either –DC or +DC position: Operation is the same
in either position unless there are semiconductors in the circuit. (See para-
graph 4.16.2.) Adjust ZERO OHMS control for each resistance range.
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