Model 380363 Version 2.0 July 2005
9
Testing DC Motors
1. Disconnect the motor from the line.
2. To test the brush rigging, field coils and armature, connect one meter lead to the
grounded motor housing and the other lead to the brush on the commutator.
3. If the resistance measurement indicates a weakness, raise the brushes off of the
commutator and separately test the armature, field coils and brush rigging (one at a
time). Leave one lead connected to the grounded motor housing while testing the
motor components. This also applies to DC Generators.
Testing Cables
1. Disconnect the cable under test from the line.
2. Disconnect the opposite end of the cable to avoid errors as a result of leakage from
other equipment.
3. Check each conductor to ground and/or lead sheath by connecting one meter lead to
ground and/or lead sheath and the other meter lead to each of the conductors in turn.
4. Check insulation resistance between conductors by connecting meter leads to
conductors in pairs. Refer to diagram. In the diagram, note that the 3-conductor cable
has two wires shorted to the ground shield. This two-wire/shield connection is then
connected to one side of the meter. The remaining conductor is connected to the
other side of the meter.
