Hoffer Flow Controls CAT3-AC-MIL User Manual page 27

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-.
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
Troubleshooting
Depending on the flowrate, an
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