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Ground Test
Ground Test.
A digital multimeter can also be used to test for
grounds. Put the Function/Range Switch on the 2M
resistance (½) scale. When the test probes are put
on the commutator and the shaft, the meter must
give an indication of over load (OL). This means that
the resistance is more than 2 megohms.
NOTICE
Never use air pressure that is more than 205 kPa (30
psi). Make sure the air line has a water filter.
If there is an indication of a ground in the above test,
remove any dirt or debris form the armature with
compressed (pressure) air.
Do the test for grounds again. If there is still an
indication of a ground, make a replacement of the
armature.
Power Train
Open Circuit Test
Open Circuit Test
1. Put the digital multimeter Function / Range Switch
on the 200 ohm resistance (½) scale.
2. Put one test lead on one commutator bar. Put the
other test lead on an adjacent (next to) bar and
there must be less than one ohm resistance.
This test can also be done with an instrument,
such as a Kelvin Double Bridge, that can make a
measurement of very low resistance. Do the test
the same as above and make a comparison of the
resistance measurements.
Two burned areas on opposite sides of the
commutator are indications of an open armature
winding. These burned areas can cause very rapid
brush wear.
16
Testing And Adjusting
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