380366 V1.6 11/04
11
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 at right.
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.
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.
Appliance
Test Equipment Depot - 800.517.8431 - 99 Washington Street Melrose, MA 02176
FAX 781.665.0780 - TestEquipmentDepot.com
