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“D”
connector (See Appendix B). Normal
operation resumes when pin 12 is left floating.
15-pin
setpoint falls below 2% of full scale.
The default is enabled.
On/Off Control 3.12
For all FMA-1900 controllers, on/off control is provided via a
mechanical or open collector switch. You can implement this
option manually by connecting an on/off switch between pins 3
and 12 of the
setpoint is less than 2% of full scale. To disable the feature,
move DIP switch 5 to the left. The valve will then remain
open even when the
you
are
observing.)
All FMA-1900 controllers are provided with an Auto Shut-Off
feature that, when enabled, closes the valve at a command
signal level of 2% or less of full scale.
To enable this feature on your FMA-1900, move DIP switch 5
to the right. The valve will then be forced shut whenever the
output
4mA,
depending on which
3.10 Cold Sensor Lockout Circuit
FMA-1900 controllers incorporate a safety circuit that closes
the valve when a fault condition is detected that could result in
uncontrolled flow (valve wide open). The circuit operates by
monitoring the temperature of the sensor elements and forcing
the output high if the temperature falls below a preset limit.
There are several conditions under which this could occur:
3.11
Auto Shut-Off
a)
Operation at a temperature below that for which the
instrument is rated.
b) Power failure while running at or near full scale. Upon
resumption of power, the valve will remain shut until minimum
operating temperature is again reached.
c) Sensorfailure.
The operation of this circuit may be checked by observing the
output upon power-up.
(The output signal should be high for the
first 10 to 20 seconds. After that, assuming zero flow, the output will
drop to 0 VDC or