J How To Measure Resistance; Users Manual - Fluke 78 User Manual

78

Users Manual

J How to Measure Resistance

Resistance hinders the flow of current.
Caution
To avoid possible damage to the meter or to
the equipment under test, disconnect circuit
power and discharge all high voltage capaci-
tors before measuring resistance, testing for
continuity or diode test.
The following procedure demonstrates how to use the re-
sistance function, using a coolant temperature sensor
(Figure 9) as an example:
1. Insert the test leads into the
2. Turn the rotary switch to
3. Touch the probes to the circuit. Make sure that you
have a good contact between the probes and the cir-
cuit. Dirt, oil, or other foreign matter affects the resis-
tance.
4. Read the display.
22
and COM jacks.
.
Notes on Measuring Resistance:
The resistance shown on the display is the total
resistance through all possible (parallel) paths
between the probes. This means that the resis-
tance displayed for an in-circuit resistor can
sometimes not correspond to its ohms value.
Resistance in standard test leads is about 0.1 to
0.2 . When measuring low resistances this
might be significant and should be subtracted
from the display reading.