Sunday, March 15, 2009

On-off Process control

On-off Process control

On-off control has two states: fully off and fully on. To prevent rapid
cycling, some hysteresis is added to the switching function. In operation,
the controller output is on from startup until temperature setpoint is
achieved. After overshoot, the temperature then falls to the hysteresis
limit, where power is reapplied On-off control can be used where:
- Where some temperature oscillation is permissible.
- The process is underpowered and the heater has little storage capacity.
- On electromechanical systems (compressors) where cycling must be
minimized
more


On-Off control has two states, fully off and fully on. To prevent rapid
cycling, some hysteresis is added to the switching function. In
operation, the controller output is on from start-up until temperature
set value is achieved. After overshoot, the temperature then falls to
the hysteresis limit and power is reapplied.
On-Off control can be used where:
- The process is underpowered and the heater has very little
storage capacity.
- Where some temperature oscillation is permissible.
- On electromechanical systems (compressors) where cycling
must be minimized

more

Relate Posts