Omega FMA1800A User Manual page 22

INDICATION
No zero reading after 15
minute warm up time and no
flow condition.
No zero reading after 15
minute warm up time and no
flow condition. Display
reading does not response
on zero adjustment.
No zero reading after 15
minute warm up time and
no flow condition. Display
reading does not response
on zero adjustment. But
analog output 0-5 Vdc can
be adjusted from 10mV up
to 0.5 Vdc with zero
potentiometer R34.
LCD Display remains blank
when unit is powered up.
But flow can be observed
on analog output 0-5 Vdc
(pis 2 and 3 of the
D-connector).
LCD Display remains blank
when unit is powered up. No
response on the flow from
analog output 0-5 Vdc
(voltage is less than 15 mV).
LIKELY REASON
Embedded temperature has
been changed.
Power supply voltage is
less than 11.0 Vdc.
Wire is disconnected inside
of the LCD Display.
LCD Display connector is
not attached to the
FMA1700A/1800A or
connection is loose.
Wire is disconnected inside
of the LCD Display.
Power supply is bad or
polarity is reversed.
PC board is defective.
18
REMEDY
Readjust ZERO
potentiometer R34 through
the access hole
(see page 13 for details).
Measure voltage on pins
[4] and [5] of the 9-pin
D-connector. If voltage is
less than 11.0Vdc replace
power supply with new one
(regulated 12.0 to 24.0
Vdc, 250 mA minimum is
recommended).
Carefully remove the LCD
from FMA1700A/1800A.
Remove the aluminum
housing on the side of the
connection cable. Side the
LCD assembly out of the
aluminum housing. Check
connection for all four
wires. If any wire is
disconnected restore
connection and readjust
zero potentiometer R34 to
get zero reading on the
display (ensure gas source
is disconnected and no
seepage or leak occurs in
to the meter).
Check LCD connector
(remove and reinstall LCD
connector).
See instructions for pos. 3.
Measure voltage on pins
[4] and [5] of the 9-pin
D-connector. If voltage is
less than 11.0Vdc replace
power supply with new one
(regulated 12.0 to 24.0
Vdc, 250 mA minimum is
recommended). If polarity
is reversed (reading is
negative) make correct
connection.
Return FMA1700A/1800A
to factory for repair.