380375 V1.5 3/04
6
Applications
Measuring Power Tools and Small Appliances
For small appliances, connect the Black (EARTH) lead to conductors and the Red (LINE)
lead to insulating material.
For single or double insulated power tools, one lead should be connected to the device’s
chuck, blade, etc. and the other lead to one of the AC power cord conductors (test both
conductors in turn). Refer to the power tool application diagram below.
Testing Motors
AC Motors
Disconnect the motor from the line by:
a. Disconnecting the wires from the
motor terminals or
b. Opening the main switch
If the main switch is opened, and the
motor also has a motor-starter, then
the starter must be held in the ON position. With the main switch opened, the measured
resistance will include the resistance of the motor wire and all other components between
the motor and the main switch. If a weakness is indicated, the motor and other
components should be checked individually. If the motor is disconnected at the motor
terminals, connect the RED lead to the grounded motor housing and the BLACK lead to
one of the motor leads.
DC Motors
1. Disconnect the motor from the line.
2. To test the brush rigging, field coils and armature, connect the RED lead to the
grounded motor housing and the BLACK 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 by
connecting one lead to each individually, leaving the other connected to the grounded
motor housing. This also applies to DC Generators.
Testing Single Conductor Cables
1. Completely disconnect the cable
under test from its source and
destination.
2. Connect the test leads to the
cable as shown at right.
Core Insulation Sheath Covering
EARTH GUARD LINE
AC
Plug
For 2 or 3 prong plugs, connect the
RED lead to one conductor at a time
Connect the BLACK
lead to the chuck
Connect RED lead
to grounded housing
Connect BLACK lead
to the motor leads
