Satish,
The OUTSEL block is set up to handle reset windup & block initialization
handling. It can be used where you have a normal PID loop that should be
bumplessly interupted when a second controlled variable reaches a constraint
target. Let's say you were normally operating with a fixed and steady gas
flow to a vessel. In case the vessel pressure was getting close to the
relief valve setting you decide that the normal feedrate must be cut. You
set the SELOPT parameter to 2 for "Low" selection and add a second PID
Pressure control loop with a setpoint somewhat below the relief valve
setting. Properly configured: at the moment the pressure rises to the
setpoint of the pressure controller the flow control valve will just start
to close (from it's current position) and the loop will become a pressure
controller with a minimum flow constraint. When the vapor removal rate from
the vessel is increased the pressure controller will open the flow control
valve until the flow setpoint is achieved and the flow controller will now
bumplessly resume control of the valve. The SIGSEL block is possible but
the OUTSEL block was built for this specific application. Many
implementations are possible. Hope this answered your question.
Rick Rys
R2Controls
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