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4.1 Authorized Maintenance
With proper care in installation and use, the flowmeter will require little or no maintenance. If
maintenance does become necessary, most of the instrument can be cleaned or repaired in the field.
Some procedures may require recalibration. Do not attempt these procedures unless facilities are
available. Entry into the sensor or tampering with the printed circuit board will void warranty. Do
not perform repairs on these assemblies while the unit is still under warranty.
4.2 Troubleshooting
Symptom:Symptom:
Symptom:Symptom:
Symptom: Output reads strong indication of flow with no flow present. Zero pot has no effect.
Cause:Cause:
Cause:Cause:
Cause: Power shorted out.
Action:Action:
Action:Action:
Action: Unplug power supply for a few seconds, then plug it back in. If this is ineffective,
disconnect the power supply from the unit and check the power supply voltage
(+15 to +25 VDC on pin 1).
Symptom:Symptom:
Symptom:Symptom:
Symptom: Output of flowmeter is proportional to flow, but extremely small and not correctable
by span pot.
Cause:Cause:
Cause:Cause:
Cause: Sensor is not being heated.
Action:Action:
Action:Action:
Action: Shut off gas supply and disconnect the power to the flowmeter. Remove cover and pc
board from unit. Check the resistance between w1 and w2 on PCB-844 (refer to
figures in section 6) of the flowmeter. The resistance should be approximately 560 W.
The resistance between w3 and w4 should be approximately 2-3 W. If not, the
sensor unit needs to be replaced.
Symptom:Symptom:
Symptom:Symptom:
Symptom: Sensor has proper resistance readings, but little or no output with flow.
Cause:Cause:
Cause:Cause:
Cause: Plugged sensor.
Action:Action:
Action:Action:
Action: Shut off gas supply and disconnect the power to the flowmeter. Remove cover and pc
board from unit. If sensor has evidence of clogging, clean or replace as applicable.
Symptom:Symptom:
Symptom:Symptom:
Symptom: Flowmeter reads other than 0.00 VDC with no flow or there is a small flow when the
flowmeter reads 0.00 VDC.
Cause:Cause:
Cause:Cause:
Cause: Zero pot is out of adjustment.
Action:Action:
Action:Action:
Action: Shut off all flow. For the standard 0-5VDC output, adjust the zero potentiometer
located on the lower outlet side of the flowmeter until the meter indicates zero. For
the optional 4-20 mA output, adjust the zero potentiometer so that the meter
indicates slightly more than 4 mA, i.e. 4.03 to 4.05 mA. This slight positive
adjustment ensures that the 4-20 mA transmitter is not in its cut-off region. The
error induced by this adjustment is approximately 0.3% of full scale.
Symptom:Symptom:
Symptom:Symptom:
Symptom: Flowmeter is out of calibration and non-linear.
Cause:Cause:
Cause:Cause:
Cause: Leaks in the gas inlet or outlet fittings.
Action:Action:
Action:Action:
Action: Check all fittings for leaks by placing soap solution on all fittings between gas supply and
final destination of gas. Check flowmeter for leaks. Replace “O”-rings if required or
recalibrate as necessary.
Maintenance
SECTION 4