3-State ON/OFF Loop Controller
(Original Document)
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Description
The 3-state ON/OFF Loop Controller processes simple process controls, for which discrete 3 position monitoring is adequate.
Control of the 2 actuators is performed according to the position of process value/setpoint deviation in relation to 2 thresholds (upper and lower).
Threshold management integrates a configurable hysteresis. It is possible, for instance, to use the loop controller to regulate a hot/cold process as discrete.
For more complex process controls, we recommend using a PID loop controller.
Functional Diagram:
Parameters
Input Parameters:
Parameter
Symbol
Type
Thresholds
Default Value
R/W
Process Value
PV
REAL
-3.4E38 / 3.4E38
/
R
Setpoint Value
SP
REAL
-3.4E38 / 3.4E38
/
R
Internal Parameters:
Parameter
Symbol
Type
Thresholds
Default Value
R/W
Lower Threshold
ONOFF_L
REAL
-3.4E38 / 3.4E38
-5.0
R/W
Upper Threshold
ONOFF_H
REAL
-3.4E38 / 3.4E38
5.0
R/W
Hysteresis
HYST
REAL
ONOFF_L / ONOFF_H
0.0
R/W
Output Parameters:
Parameter
Symbol
Type
Thresholds
Default Value
R/W
Process Value / Setpoint Deviation
DEV
REAL
-3.4E38 / 3.4E38
/
R
OUT1 command status
STS_RAISE1
EBOOL
/
/
R
OUT2 command status
STS_LOWER1
EBOOL
/
/
R
Auto_Man
STS_M_A
EBOOL
/
/
R
Command value
OUT1
EBOOL
/
/
R
Command value
OUT2
EBOOL
/
/
R
Operating Modes
The 3-state ON/OFF Loop Controller has two operating modes:
Operating modes and associated commands:
Execution Monitoring
The system indicates a processing error in the following cases:
In each case, the error is considered to be serious. The regulation loop output is frozen. Errors are reflected in the status words.