GPS-X Technical Reference

355 Tools Object
TIMER CONTROL
The timer is used to schedule and control intermittent plant operations. For example the timer
control can be used to implement intermittent aeration in an activated sludge tank. Another
application is the desludging of a primary settler.
The timer works in cycles. At the start of each cycle the timer sets its manipulated variable to a
pre-defined ‘on’ value. The manipulated variable is kept at this value for a user-defined fraction
of the cycle. For the remainder of the cycle, the manipulated variable is set to a pre-defined ‘off’
value. This is ideally suited for intermittent aeration because the controller can turn on the air
flow at regular intervals for a user defined length of time.
The timer control parameters are accessed by selecting Parameters > Set up in the Process Data
menu. These parameters are detailed below:
Controller (ON - OFF): This switch activates the timer.
Manipulated variable with label: The cryptic name of the manipulated variable
including the appended stream label.
Cycletime: The length of one cycle.
Ontime in one cycle: The length of time (starting at the beginning of the cycle) that
manipulated variable value is set to the `on' value during a cycle.
Value of manipulated variable when on: The `on' value of manipulated variable.
Value of manipulated variable when off: The `off' value of manipulated variable.
MULTIVARIABLE CONTROLLERS
The multivar model is used in conjunction with the Advanced Control Module. See the
Advanced Control Module Manual for details on using multivariable controllers in GPS-X.
GPS-X Technical Reference