Dwyer GFM - Manual (Page 22)

18
INDICATION
LCD Display reading does
not correspond the correct
flow range according analog
output 0-5 Vdc signal.
LCD Display reading and
analog output 0-5Vdc
signal are fluctuate in wide
range during the flow
measurement.
LCD Display reading does
correspond the correct flow
range, but 0-5 Vdc output
signal does not change
(always the same reading
or around zero).
LCD Display reading and
0-5 Vdc output voltage do
correspond the correct flow
range, but 4-20 mA output
signal does not change
(always the same or
reading around 4.0 mA).
Calibration is off (no more
than 3.0 % F.S.).
REMEDY
Readjust LCD Display
scaling for required full scale
flow (see 7.4 on page 14).
Check external connections
to pins 2 and 3 of the
D-connector. Make sure the
load resistance is more
than 1000 Ohm.
Return GFM to factory for
repair.
Check external connections
to pins 8 and 9 of the
D-connector. Make sure the
loop resistance is less than
500 Ohm.
Return GFM to factory for
repair.
Shut off the flow of gas into
the GFM (ensure gas source
is disconnected and no
seepage or leak occurs in to
the meter). Wait for 15
minute. with no flow
condition and readjust zero
potentiometer R34 to get
zero reading on the display.
LIKELY REASON
LCD Display is adjusted for
wrong flow range or
engineering units.
Output 0-5 Vdc signal (pins
2 and 3 of the D-connector)
is shorted on the GND or
overloaded.
Output 0-5Vdc schematic is
burned out or damaged.
External loop resistance is
open or more than 500
Ohm.
Output 4-20 mA schematic
is burned out or damaged.
GFM has initial zero shift.