19
18
d. Measuring Resistance
WARNING!
Do not attempt to make resistance measurements with
circuit energized. For best results, remove the resistor
completely from circuit before attempting to measure it.
NOTE:
To make accurate low ohm measurements, short the
ends of the test leads together and record the resistance
reading. Deduct this value from actual readings.
Instrument set-up:
FUNC.
BLACK RED
MIN
MAX
TEST LEAD TEST LEAD
READING
READING
Ω
COM
V/
Ω
0.1
Ω
400
Ω
Measurement Procedure:
1.
Disconnect power to circuit to be measured.
2.
Plug black test lead into the
COM
input jack.
3.
Plug red test lead into
V/
Ω
input jack.
4.
Set the rotary switch to the
400
Ω
function.
5.
Connect test leads to circuit to be measured.
6.
Read the resistance value on the 291.
Optional Modes
•
HOLD:
Freezes the reading on the LCD.
!
Application Notes (Resistance)
When measuring resistance of a motor, make
sure the power is disconnected prior to testing.
Set up meter following steps under
“Measurement Procedure” on page 19, and
proceed with the following:
•
Connect the red test lead to one power
input line of the motor and the black test
lead to the other power input line of the
motor. In most applications if the reading
is OFL, the motor winding is open.
•
Connect the red test lead to the frame of
the motor and the black test lead to the
winding. In most applications if a reading
of 0 Ohms is displayed, the winding is
shorted to the motor frame (ground).
