Measuring Duty Cycle With Fluke 88 - Navistar International DT 466 Diagnostic/Troubleshooting Manual

576
Figure 559 Checking for open circuits
Open electrical circuits can be diagnosed using an
ohmmeter. Disconnect the power supply to the circuit
and isolate the circuit from all other circuits. The circuit
between the light and the ground is disconnected to
prevent reading a circuit that may be shorted to
ground ahead of the load device as a continuous
circuit. Connect the ohmmeter to the open ends of
the circuit. A high reading (infinity) indicates an open
circuit. A reading near zero indicates a continuous
circuit. With the Fluke 88 Digital Multimeter (DMM),
an open circuit will read OL (over limit).
Read all safety instructions in the "Safety Information" section of this manual before doing any procedures.
8 DIAGNOSTIC TOOLS AND ACCESSORIES
EGES-270-1
Follow all warnings, cautions, and notes.
© August 2008 Navistar, Inc.
Figure 560 Checking for short circuits
Checks for short circuits are similar to checks for open
circuits. Isolate the circuit from the power source and
the ground point. Connect the ohmmeter between an
isolated circuit and a good ground point to check the
circuit for a short to ground. A short to ground will be
indicated by a reading near zero. A circuit that is not
shorted to ground will cause a high meter reading.

Measuring Duty Cycle with FLUKE 88

When measuring duty cycle, ensure that the large dial
on the meter is pointing to volts DC, the DUTY button
is set to the Duty Cycle function, and the trigger has a
positive slope.