Limiter (FB)

FUNCTION_BLOCK Limiter

Short Description

Limit value monitoring of an analog value

Portrayal

Interfaces

Inputs

Name	Datatype	Range	Init-Value	Function
rIn	REAL		0	Analog input

Outputs

Name	Datatype	Range	Init-Value	Function
rOut	REAL			Analog output
xErr	BOOL			FALSE: No limit value violation TRUE: Limit value violation

Setpoints / Parameters

Name	Datatype	Range	Init-Value	Function
rMinLimit	REAL		-50	Lower limit value
rMaxLimit	REAL		150	Upper limit value
rReplacementOption	eLimiterMode	InpultValue, MinValue, MaxValue, LastValue, ReplacementValue	InputValue	Selection of the value at output rOut depending on the selected option
rReplacementValue	REAL		0	Value at output rOut if limit value is violated and option’ ReplacementValue’ is selected

Functional Description

Analog value output rOut

The analog value output rOut follows the analog value input rIn as long as the analog value input rIn does not exceed any of the two limit values

rMinLimit or rMaxLimit.

A limit value violation is always present if the analog value input rIn is lower than the limit value rMinLimit or

higher than the limit value rMaxLimit.

In case of a limit value violation, the analog value output rOut is defined depending on the selected option rReplacementOption (eLimiterMode).

rIn	ReplacementOption	rOut	Notes
X	InputValue	rIn	Option ‘InpultValue’
X	MinValue	rMinLimit	Option ‘MinValue’
X	MaxValue	rMaxLimit	Option ‘MaxValue’
X	LastValue	Last state of rOut before the limit value violation	Option’ LastValue’ Attention: The last value is not saved on an PLC cold start!
X	ReplacementValue	rReplacementValue	Option ‘ReplacementValue’

Legend: X = any

Digital output xErr

The digital output xErr signals an active limit violation.

Limit value violation	xErr	Notes
FALSE	FALSE	No limit value violation
TRUE	TRUE	Limit value violation

Legend: X = any

Visualization

Information

Element	Authors	Date	Version	Notes
Function	Adam Bartod	09.2016	1.0	Initial version
Programming	Adam Bartod	09.2016	1.0	Initial version
Test	Kevin Rohn, Jochen Reu	12.2016	1.0	Initial version
Documentation	Jochen Reu	10.2017	1.0	Initial version
Documentation	Lukas Pfänder	11.2017	0.1.3.0	Revision

Codesys

InOut:

Scope	Name	Type	Initial	Comment
Input	rIn	REAL	0	Analog input
	rReplacementValue	REAL	0	Value at output rOut if limit value is violated and option’ ReplacementValue’ is selected
	rReplacementOption	eLimiterMode	eLimiterMode.InputValue	Selection of the value at output rOut depending on the selected option
	rMaxLimit	REAL	150	Upper limit value
	rMinLimit	REAL	-50	Lower limit value
Output	rOut	REAL		Analog output
	xErr	BOOL		Output limit value violation