Chapter Four: Operation
Valve Override
27
Valve Override
Valve override enables the control valve to be fully opened (purged) or closed independent of the
set point command signal.
For 1100 Series Controllers with a Type “D” Connector:
To open the valve, apply a TTL low to pin 4, or connect pin 4 to pin 11 (signal common).
To close the valve, apply a TTL low to pin 3, or connect pin 3 to pin 11.
For 1100 Series Controllers with a P. C. Card Edge Connector:
To open the valve, apply a TTL low to pin D, or connect pin D to pin 10 (signal common).
To close the valve, apply a TTL low to pin L, or connect pin L to pin 10.
When both Valve Close and Valve Open are pulled down, the meter purges at a rate of flow that
is somewhat less than the full scale range of the controller.
Adjusting the Speed to Set Point
The 1100 Series MFC instruments are equipped with a circuit that provides a very rapid response
(<2 seconds) to a small set point command. At set points of less than 10% of F.S., there is a
slight overshoot. The integrated flow for this period of time divided by the elapsed time (1.5
seconds.) is less than the set point flow rate. If this overshoot is harmful to your process, consult
the factory for disabling instructions or for modification.
NUPRO BN Shutoff Valve
It is only necessary to apply or remove air pressure to the air operator to ensure an open or closed
condition. No attempt should be made to control flow rate using this valve.
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