Limiter

Limiter (FB)

FUNCTION_BLOCK Limiter

Short description

Limit monitoring of an analog value

Representation

Interfaces

Inputs

Name	Data type	Value range	Initial value	Function
rIn	REAL		0	Analog value input

Outputs

Name	Data type	Value range	Initial value	Function
rOut	REAL			Analog value output
xErr	BOOL			* FALSE: no limit violation * TRUE: Limit violation

Setpoints / parameters

Name	Data type	Value range	Initial value	Function
rReplacementValue	REAL		0	Value at the output rOut when limit is violated and option 'ReplacementValue'
rReplacementOption	eLimiterMode	InpultValue, MinValue, MaxValue, LastValue, ReplacementValue	InputValue	Selection of the value at the output rOut depending on the chosen option
rMaxLimit	REAL		150	Upper limit
rMinLimit	REAL		-50	Lower limit

Function 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 violate either of the two limits rMinLimit or rMaxLimit is violated. A limit violation always occurs when the analog value input rIn is less than the limit rMinLimit or greater than the limit rMaxLimit is. In the event of a limit violation, the analog value output will be rOut determined 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 violation	Option 'LastValue' Warning: The last value is not retained during a PLC cold start!
X	ReplacementValue	rReplacementValue	Option 'ReplacementValue'

Legend: X = any

Digital output xErr

The digital output xErr indicates an active limit violation.

Limit violation	xErr	Notes
FALSE	FALSE	no limit violation
TRUE	TRUE	Limit violation

Legend: X = any

CODESYS

InOut:

Scope	Name	Type	Initial
Input	rIn	REAL	0
Input Const	rReplacementValue	REAL	0
Input Const	rReplacementOption	eLimiterMode	eLimiterMode.InputValue
Input Const	rMaxLimit	REAL	150
Input Const	rMinLimit	REAL	-50
Output	rOut	REAL
Output	xErr	BOOL
Output	xAlarmHigh	BOOL
Output	xAlarmLow	BOOL