Ingersoll-Rand HP375WIR, Installation, Operation And Service Manual

Page: 21 / 46

Book: 22600498 (1/05) 21
MEASURING VOLTAGE, RESISTANCE
FREQUENCY AND DUTY CYCLE
General Measuring Guidelines:
Since the electrical system uses sealed connectors and splices, access of test points
can be difficult. It is recommended that a test probe kit be used to access the signals to
prevent damage that can cause future failures.
Measuring Voltage:
A digital voltmeter is recommended to make measurements. Voltage measurements
are made by connecting the RED + lead to the desired signal and the BLACK lead to
the common. The test lead connections must be secure or incorrect readings will result.
Use circuit common for the BLACK lead, not chassis ground or other metal connection.
Circuit common will be any of the BROWN wires or battery negative can be used.
IMPORTANT INFORMATION
DO NOT USE MACHINE FRAME, SHEET METAL, PIPING OR OTHER METAL
COMPONENTS AS COMMON OR GROUND WHEN MAKING VOLTAGE OR
FREQUENCY MEASUREMENTS.
Measuring Resistance:
Extra care must be taken when making resistance measurements. Test probe
connections are crucial to correct readings. Ensure the test probe makes a solid
connection with the wire(s) or connector pin(s) under test. The test probe kit may help
with these types of measurements. Make sure system power is turned OFF while
making resistance measurements.
Measuring Frequency:
Frequency is measured in the same manner as voltage, but the meter is set for “HZ” or
frequency. Good connections are important or false readings will occur.
Measuring Duty Cycle:
To measure duty cycle, setup the meter as if measuring frequency or voltage. Select
the “%” or duty cycle function and take measurements. As of the date of this writing,
Fluke is the only known digital voltmeter that has the duty cycle feature. The Fluke
Model 87 Digital Meter has the duty cycle function.