Dwyer GFM4 - Manual (Page 15)

9. TROUBLESHOOTING
9.1 - Common Conditions
Your GFM3/4 Digital Mass Flow Meter was thoroughly checked at numerous quality
control points during and after manufacturing and assembly operations. It was
calibrated according to your desired flow and pressure conditions for a given gas
or a mixture of gases. It was carefully packed to prevent damage during shipment.
Should you feel that the instrument is not functioning properly, please check for the
following common conditions first:
• Are all cables connected correctly?
• Are there any leaks in the installation?
• Is the power supply correctly selected according to requirements?
• When several meters are used, a power supply with appropriate current rating
should be selected.
• Were the connector pinouts matched properly?
• When interchanging with other manufacturers' equipment, cables and
connectors must be carefully wired for correct pin configurations.
• Is the pressure differential across the instrument sufficient?
No.
1
2
3
4
5
6
7
8
9
10
11
Indication
No zero reading after 15 min. warm up time and
no flow condition.
LCD display remains blank when unit is powered
up. No response when flow is introduced from
analog outputs 0 to 5 Vdc or 4 to 20 mA.
LCD display reading and/or analog output 0 to 5
Vdc signal fluctuate in wide range during flow
measurement.
LCD display reading does correspond to the
correct flow range, but 0 to 5 Vdc output signal
does not change (always the same reading or
around zero).
LCD display reading and 0 to 5 Vdc output
voltage do correspond to the correct flow range,
but 4 to 20 mA output signal does not change
(always the same or reading around 4.0 mA).
Calibration is off (more than 1.0 % FS).
LCD display reading is above maximum flow
range and output voltage 0 to 5 Vdc signal is
more than 5.0 Vdc when gas flows through the
GFM3/4.
Gas flows through the GFM3/4, but LCD display
reading and The output voltage 0 to 5 Vdc signal
do not respond to flow.
Gas does not flow through the GFM3/4 with inlet
pressure applied to the inlet fitting. LCD display
reading and output voltage 0 to 5 Vdc signal
show zero flow.
Gas flows through the GFM3/4, but LCD display
reading is negative and output voltage 0 to 5 Vdc
signal does not respond to flow (reading near
1mV).
GFM3/4 is disconnected from the source of the
gas (no flow conditions) but LCD display reading
is fluctuating in wide range. Output voltage 0 to 5
Vdc signal also fluctuating. The power supply
voltage is within specification and stable.
Likely Reason
Embedded temperature has been
changed.
Power supply is bad or polarity is
reversed.
PC board is defective.
Output 0 to 5 Vdc signal (pins 2-15, 3-16,
4-17 of the D-connector) is shorted on
the GND or overloaded.
Output 0 to 5 Vdc schematic is burned
out or damaged.
Analog flow output scale and offset
variable are corrupted.
External loop resistance is open or more
than 500 Ω.
Output 4 to 20 mA schematic is burned
out or damaged.
GFM3/4 has initial zero shift.
Sensor under swamping conditions (flow
is more than 10% above maximum flow
rate for particular GFM3/4).
PC board is defective.
The gas flow is too low for particular
model of GFM3/4.
GFM3/4: RFE is not connected properly to
the inlet fitting.
GFM3/4 models: RFE is shifted and
blocked the sensor.
Sensor or PC board is defective.
Filter screen obstructed at inlet.
Direction of the gas flow is reversed.
GFM3/4 is connected in the installation
with back pressure conditions and gas
leak exist in the system.
Direction of the gas flow is reversed.
GFM3/4 is connected in the installation
with back pressure conditions and gas
leak exist in the system.
Sensor or PC board is defective.
Solution
Perform Auto Zero Procedure (see section 5.3.10 "Zero
Calibration").
For 12 or 24 Vdc option:
Measure voltage on pins 1 and 18 of the 25-pin D connector. If
voltage is out of specified range, then replace power supply with a
new one. If polarity is reversed (reading is negative) make correct
connection.
For ±15Vdc option:
Measure voltage on pins 1-18 and 14-18 of the 25-pin D connector.
If voltage is out of specified range, then replace power supply with
a new one. If polarity is reversed (reading is negative) make correct
connection.
Return GFM3/4 to factory for repair.
Check external connections to pins 2-15, 3-16, 4-17 of the D
connector. Make sure the load resistance is more than 1000 Ω.
Return GFM3/4 to factory for repair.
Restore original EEPROM scale and offset variable or perform
analog output recalibration (see section 7.3).
Check external connections to pins 2 and 15 of the D connector.
Make sure the loop resistance is less than 500 Ω.
Return GFM3/4 to factory for repair.
Shut off the flow of gas into the GFM3/4 (ensure gas source is
disconnected and no seepage or leak occurs into the meter).
Wait for 15 min. with no flow condition and perform Auto Zero
calibration Procedure (see section 5.3.10 "Zero Calibration").
Lower the flow through GFM3 within calibrated range or shut down
the flow completely. The swamping condition will end automatically.
Return GFM3/4 to factory for repair.
Check maximum flow range on transducer's front panel and make
required flow adjustment.
Unscrew the inlet compression fitting of the meter and reinstall
RFE (see section 6.2.2). NOTE: Calibration accuracy can be
affected.
Unscrew the four socket head cap screws at the inlet side of the
meter. Reinstall RFE and retaining ring (see section 6.2.3). NOTE:
Calibration accuracy can be affected.
Return GFM3/4 to factory for repair.
Flush clean or disassemble to remove impediments or replace the
filter screen (see section 6.2). NOTE: Calibration accuracy can be
affected.
Check the direction of gas flow as indicated by the arrow on the
front of the meter and make required reconnection in the
installation.
Locate and correct gas leak in the system. If GFM3/4 has internal
leak return it to factory for repair.
Check the direction of gas flow as indicated by the arrow on the
front of the meter and make required reconnection in the
installation.
Locate and correct gas leak in the system.
If GFM3/4 has internal leak return it to factory for repair.
Return GFM3/4 to factory for repair.
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