Temperature Controller - Staveb AG

3-16 Configuration and Basic OperationExecuting the ON/OFFControl MethodOverviewIn the reverse operation ON/OFF control method, the control output (MV)turns OFF when the controlled temperature (PV) reaches the user-defined setpoint. When the control output (MV) turns OFF, the controlled temperaturebegins to fall and the control output turns ON again. This operation isrepeated at a certain point. At this time, how much the temperature must fallbefore the control output turns ON again is determined by the Hysteresis(OUT1) parameter. Also, how much the manipulated variable must be adjustedin response to the increase or decrease in the process value is determined bythe Direct/Reverse Operation parameter.ON/OFF Control ParametersSwitching between 2-PID control and ON/OFF control is carried out by thePID/ON/OFF parameter (Initial Setting function group). When thisparameter is configured to pid, 2-PID control is selected, and whenconfigured to onof, ON/OFF control, is selected. Note: The default isonof.HysteresisIn the ON/OFF control method, the hysteresis is used to provide amargin/differential for switching the control output ON when the controlledtemperature moves away from the required set point. The Hysteresisparameter is used give stability to the output around the set point.The hysteresis value for the control output (OUT1) function is set by theHysteresis (OUT1) parameter. In standard hysteresis value for the heating orcooling control, the Hysteresis (OUT1) setting is used as the hysteresis setting(Adjustment function group) regardless of the control mode, heating control,or cooling control.Figure 3.24 Reverse OperationReverse operationONHysteresis (OUT1)OFFSet pointPVPublication 900-UM003C-EN-E - January 2004