Hoffer Flow Controls CAT3-DC-MIL User Manual page 28

20 Troubleshooting
5.
6.
7-2-2 Symptom: Flow indication with no flow present
This symptom indicates the presence of electrical noise
pickup.
1. 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.
2. 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.
3. Verify cable shield connection.
4. Verify electronics unit enclosure connection to ships ground.
HP-324-5
defective pickup coil and the pickup coil must be
replaced.
With an established flowrate, configure the digital
multimeter to measure AC volts, using the two volt scale.
Connect the positive lead to pin A of pickup coil. And
the negative lead to pin B of pickup coil. Depending on
the flowrate an approximate voltage reading of 10
millivolts to 1 volt should be measured.
If zero volts are measured, a stalled rotor condition is
indicated. Remove the flow sensor from the piping.
Refer to flow sensor manual.