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Omega FMA 4000 User Manual: Troubleshooting Guide

Digital mass flow meters.
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9.2

Troubleshooting Guide

NO.
INDICATION
1
No zero reading after
15 min. warm up time
and no flow condition.
2
Status LED indicator
and LCD Display
remains blank when
unit is powered up. No
response when flow is
introduced from analog
outputs 0-5 Vdc or
4-20 mA.
3
LCD Display reading or
/ and analog output
0-5 Vdc signal fluctuate
in wide range during
flow measurement.
4
LCD Display reading
does correspond to the
correct flow range, but
0-5 Vdc output signal
does not change
(always the same read
ing or around zero).
5
LCD Display reading
and 0-5 Vdc output
voltage do correspond
to the correct flow
range, but 4-20 mA
output signal does not
change (always the
same or reading
around 4.0 mA).
6
Calibration is off (more
than ±1.0 % F.S.).
7
LCD Display reading is
above maximum flow
range and output volt
age 0-5 Vdc signal is
more than 5.0 Vdc
when gas flows
through the FMA 4000.
LIKELY REASON
Embedded temperature
has been changed.
Power supply is bad or
polarity is reversed.
PC board is defective.
Output 0-5 Vdc signal
(pins 2–1 of the
D-connector) is shorted
on the GND or
overloaded.
Output 0-5 Vdc
schematic is burned
out or damaged.
Analog flow output
scale and offset
variable are corrupted.
External loop is open or
load resistance more
than 500 Ohm.
Output 4-20 mA
schematic is burned
out or damaged.
FMA 4000 has initial
zero shift.
Sensor under
swamping conditions
(flow is more than 10%
above maximum flow
rate for particular
FMA 4000).
PC board is defective.
35
SOLUTION
Perform Auto Zero Procedure (see section
5.3.6 "Zero Calibration").
Measure voltage on pins 7 and 5 of the 15
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 FMA 4000 to factory for repair.
Check external connections to pin 2 – 1, of
the D-connector. Make sure the load
resistance is more than 1000 Ohm.
Return FMA 4000 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 Ohm.
Return FMA 4000 to factory for repair.
Shut off the flow of gas into the FMA 4000
(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 5.3.7 "Zero Calibration").
Lower the flow through FMA 4000 within
calibrated range or shut down the flow
completely. The swamping condition will
end automatically.
Return FMA 4000 to factory for repair.

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Troubleshooting

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