2-State ON/OFF Loop Controller

Description

The 2-state ON/OFF Loop Controller processes simple process controls, for which discrete 2 position monitoring is adequate.

Actuator control is performed according to process value/setpoint deviation in relation to 2 thresholds (upper and lower).

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

Output Parameters:

Parameter	Symbol	Type	Thresholds	Default Value	R/W
Command Status	STS_RAISE1	EBOOL	/	/	R
Auto_Manu State	STS_M_A	EBOOL	/	/	R
Command	/	EBOOL	/	/	R
Process Value / Setpoint Deviation	DEV	REAL	-3.4E38 / 3.4E38	/	R

Process Value / Setpoint Deviation

As soon as the Process Value/Setpoint Deviation (DEV = PV – SP) becomes smaller than the lower ONOFF_L threshold, the logic output switches to 1 state. If the deviation starts to increase again, it must exceed the threshold ONOFF_H for the output to switch to 0 state.

Operating Modes

The 2-state ON/OFF Loop Controller has two operating modes:

Automatic mode: the output is calculated by the loop controller.
Manual mode: the loop controller does not set the output. You can directly modify the value of the variable connected to the output.

In case of cold start, the manual mode output is set to the 0 state.

Execution Monitoring

The system indicates a processing error in the following cases:

A non-integer input data item is detected on one of the parameters.
A problem appears in the floating-point calculation.
Lower threshold > 0.
Upper threshold < 0.

In any case, the error is considered to be critical. The regulation loop output is frozen. Errors are reflected in the status words.