Model 380360 Version 1.7 September 2003
7
Applications
Measuring Power Tools and Small Appliances
This section applies to any device under
test that uses a line cord. For double
insulated power tools, the meter’s leads
should be connected to the device’s
housing (chuck, blade, etc.) and the ground
of the power cord. Refer to the diagram.
Testing AC Motors
Disconnect the motor from the line by disconnecting the wires from the motor terminals or
opening the mains switch.
If the mains switch is opened, and the motor also has a motor-starter, then the starter must
be held in the ON position. With the mains 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 one
meter lead to the grounded motor housing and the other lead to one of the motor leads.
Refer to diagram at below.
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 at right. 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.
Appliance
HI LO
Meter test leads
Motor
GND
Starter
Mains
Switch
LINE
Notes:
1. The STARTER must be in the ON position during
the test.
2. The motor-to-meter connection must be made to
the motor housing (ground).
3. The meter-to-main switch connection must be to the
motor side of the main switch as shown.
LO HI
meter test leads
LO HI
Test leads
