Hoffer CAT3-DC-MIL, User Manual, Page: 23 / 29

Troubleshooting 15
HP-324-5
7. TROUBLESHOOTING
7-1 Introduction
The troubleshooting techniques in this chapter are designed to isolate and locate
the area of failure and to present the procedures for the replacement of
subassemblies to make the system operational.
7-2 Troubleshooting Procedures
The required test equipment for troubleshooting is as follows:
Digital Multimeter: Fluke Model 8060A or equal.
Identify one of the symptoms listed below and follow the procedure. In each case
proceed to the next step only if the defect is not found.
7-2-1 Symptom: No flow indication when flow is present
1. Visually examine the interconnecting signal cable for
broken or shorted leads.
2. With an established flowrate, configure the digital
multimeter to measure AC volts, using the two volt scale.
Measure voltage at the terminal, on Pin 3, SIG+ and Pin
4 SIG-. Depending on the flowrate, an approximate
voltage reading of 10 millivolts to 1 volt should be
measured. If voltage is present replace the electronic
unit. If no voltage go to step 3.
3. Disconnect the signal cable from the electronics unit and
from the flow sensor. Check the continuity of each lead
of the cable. If defective replace or repair.
4. With the signal cable disconnected from the flow sensor
measure the DC resistance of the pickup coil. The resistance
should read between 1500 and 2200 ohms between pin A and
pin B. A short or an open indicates a defective pickup coil
and the pickup coil must be replaced.