Short summary

Name	`LIMITER_U`
→POU type	→function block
Category	IEC-block, ControlEnh
Conform to →IEC-standard	not defined in IEC-standard
Graphical interface
Available since	version 1.47.0 (for logi.CAD 3)

Functionality

This block represents a hysteresis controller that switches abruptly between two states.

The block sets the value of the variable OUT to 1, if the value of the variable IN falls below the value of L. The variable OUT is set to 0, if the value of IN exceeds the value of L plus the hysteresis H. Otherwise OUT keeps its value.
If a negative value is set for H, the value 0 is used for the hysteresis.

Restrictions

The following restrictions apply to the usage of overloadable function block instances:

The declaration is limited to local variables.
The usage as array base type is not allowed.
The usage as structure element is not allowed.
Instance data cannot be displayed in the Values of Variables view.

In-/outputs

	Identifier	→Data type	Description
Inputs:	`IN`	`REAL`, `LREAL`, `USINT`, `UINT`, `UDINT`, `ULINT`, `SINT`, `INT`, `DINT` or `LINT` (corresponds to →generic data type `ANY_NUM`)	input
	L	`REAL`, `LREAL`, `USINT`, `UINT`, `UDINT`, `ULINT`, `SINT`, `INT`, `DINT` or `LINT` (corresponds to →generic data type `ANY_NUM`)	limit
	H	`REAL`, `LREAL`, `USINT`, `UINT`, `UDINT`, `ULINT`, `SINT`, `INT`, `DINT` or `LINT` (corresponds to →generic data type `ANY_NUM`)	hysteresis
Outputs:	`OUT`	USINT	`1` if `IN` falls below the value of `L` `0` if `IN` exceeds the value of (`L + H`)

Example for usage within ST-editor

FUNCTION_BLOCK ExampleLimiterU
	VAR
		iLimiterU : LIMITER_U;
		limit : INT := 10;
		hysteresis : INT := 5;
		okOut1, okOut2, okOut3, okOut4 : BOOL := TRUE;
	END_VAR
	
	/* IN is above L => OUT keeps initial value of 0 */
	iLimiterU(IN := 10, L := limit, H := hysteresis);
	okOut1 := iLimiterU.OUT = 0;
	
	/* IN falls below L => OUT changes its value to 1 */
	iLimiterU(IN := 9, L := limit, H := hysteresis);
	okOut2 := iLimiterU.OUT = 1;
	
	/* IN is between L and (L + H) => OUT keeps its value 1 */
	iLimiterU(IN := 11, L := limit, H := hysteresis);
	okOut3 := iLimiterU.OUT = 1;
	
	/* IN exceeds or is equal to (L + H) => OUT changes its value back to 0 */
	iLimiterU(IN := 15, L := limit, H := hysteresis);
	okOut4 := iLimiterU.OUT = 0;
	
	ENO := AND(okOut1, okOut2, okOut3, okOut4);
END_FUNCTION_BLOCK

When creating your application within the ST-editor, enter a call of a block by typing the text as requested by the syntax or use Content Assist.