TwoPoint (FB)¶

FUNCTION_BLOCK TwoPoint

Short Description¶

Linear conversion of a numerical input value by means of a characteristic curve defined by two points.

Portrayal¶

Interfaces¶

Inputs¶

Name
Datatyp

Range

Init-Value

Function

rIn_X REAL 0
Analog input

Outputs¶

Name
Datatyp

Range

Init-Value

Function

rOut_Y REAL
Analog output

xErr BOOL

FALSE:
Conversion successful

TRUE:
Conversion error

Setpoints / Parameters¶

Name
Datatyp

Range

Init-Value

Function

x1 REAL 0
Point 1 of the input range

y1 REAL 0
Point 1 of the output characteristic curve

x2 REAL 100
Point 2 of the input range

y2 REAL 100
Point 2 of the output charactersitic curve

xMinMaxLimit BOOL FALSE
Enable / disable the limitation at the analog value output rOut_Y

iMinMaxOffset INTEGER 0
Analog value output of rOut_Y

Functional Description¶

Analog value output rOut_Y¶

The analog value output rOut_Y is calculated from the analog value input rIn_X as a function of the two points P1 (x1 /** y1**)
and P2 (x2 /** y2**) according to a linear characteristic curve. In the case of a conversion error (xErr = TRUE), the
Analog value output rOut_Y remains unchanged.

Formula

rOut_Y = (((x1-rIn_X)*(y2-y1))/(x1-x2))+y1

Constraints

The analog value output rOut_Y is of the REAL data type. Due to an inappropriate selection of the parameters x1, x2, y1 and

y2 and the value of the analog value input rIn_X, the limits of the data type may be exceeded.

Releasing / blocking of the limits xMinMaxLimit¶

The limits of the analog value output rOut_Y can generally be released and blocked with this set-point / parameter.

xMinMaxLimit
Limits

Notes

FALSE
none

rOut_Y without absolute limits

TRUE
Y_min and Y_max

Limitation of the analog value output rOut_Y active

Value of the limit iMinMaxOffset¶

The limits of the analog value output are only active if the setpoint / parameter xMinMinMaxLimit is active (= TRUE).

The limit values Y_min and Y_max are then calculated as follows:

Formulas

Y_min = y1 - ((ABS(y2-y1))*iMinMaxOffset)/100

Y_max = y2 + ((ABS(y2-y1))*iMinMaxOffset)/100

y2	y2 - y1	iMinMaxOffset	Y_min	Y_max	Notes
100	100	0	0	100	Default-Limits
100	100	10	-10	110	Positive Offset
100	100	-10	10	90	Negativ Offset

Digital output xErr¶

The digital output xErr is TRUE, when the conversion failed. The following errors are taken into consideration:

x1 = FALSE UND x2 = FALSE
x1 = x2
y1 = TRUE UND y2 = TRUE
y1 = y2

Conversion error
xErr
Notes

FALSE FALSE
Conversion successful

TRUE TRUE
Conversion error

Legend: X = any

Visualization¶

Information¶

Element
Authors

Date
Version
Note

Function
Adam Bartod 04.2016 1.0
Initial version

Programming
Adam Bartod 04.2016 1.0
Initial version

Test Alexander Halter, Jochen Reu 12.2016 1.0
Initial version

Documentation
Jochen Reu 10.2017 1.0
Initial version

Revision Lukas Pfänder 11.2017 0.1.3.0
Documentation

Codesys¶

InOut:

Scope	Name	Type	Initial	Comment
Input	rIn_X	REAL	0	Analog input
Output	rOut_Y	REAL		Analog output
Output	xErr	BOOL		Error Output: FALSE: conversion successful TRUE: conversion error
Input	iMinMaxOffset	INT	0	Analog value output of rOut_Y
	xMinMaxLimit	BOOL	FALSE	Enable / disable the limitation at the analog value output rOut_Y
	y2	REAL	100	Point 2 of the output charactersitic curve
	x2	REAL	100	Point 2 of the input range
	y1	REAL	0	Point 1 of the output characteristic curve
	x1	REAL	0	Point 1 of the input range