92
CONTROL MODES
By setting hysteresis, an upper and lower control limit is created. The switching around the Set point
is therefore reduced.
SP
Control mode High
Control mode Low
Hysteresis
Process value
Control output
Control output
On
Off
On
Off
Figure 23:
On/Off Control with Hysteresis
Running control On continuously for an extended period of time is prevented by Overtime control
action.
SP
Control mode High
Overtime
Hysteresis
Process value
Control output
Alarm condition
On
Off
Figure 24:
On/Off Control, Overtime Control Action
Realy On time has a guaranteed minimum to prevent stressing the actuators electrically or
mechanically.
SP
Control mode High
Minimum On time
Hysteresis
Process value
Control output
Figure 25:
On/Off Control, Minimum On Time
