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97
CONTROL MODES
Analog Output is proportional with Set point variance over Control period.
SP
Control period
Control mode
High
Control mode
Low
Deviation
Process value
Analog out
Analog out
20 mA
0/4 mA
20 mA
0/4 mA
Figure 30:
Proportional Control, Analog Out - Control Mode High & Low
Running control On continuously for an extended period of time is prevented by Overtime control
action.
SP
Control period
Proportional control
mode High
Overtime
Deviation
Process value
Relay out
Alarm condition
Figure 31:
Proportional Control, Relay Out - Proportional Control Mode High, Overtime
Relay On time has a guaranteed minimum to prevent stressing the actuators electrically or
mechanically.
SP
Relay out
Control period
Proportional control
mode High
Deviation
Process value
Relay out with min.
On time control action
Min. On time
On
Off
Figure 32:
Proportional Control, Relay Out, Proportional Control Mode High, Min. On Time