X1, X2, Y1, Y2
Defines the first raw process variable value that is required to determine the unit conversion. The unit conversion is carried out by defining two points. These points can be used to create a linear equation.
Gradient
m = (Y2 - Y1)/(X2 - X1)
Offset
b = Y - m * X
In general
Y = m * X + b
The conversion when reading a value is carried out using the above equation Conversion value = m * raw value + b.
The "raw value" and "conversion value" refer to the use of the unit class:
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If a unit class is used in the Unit class (process) parameter of a process variable, the raw value is the process variable value from the communication component. The conversion value is the value in the variable server.
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If a unit class is used in the Unit class (display) parameter of a process variable, the conversion value is the value displayed in the controls. The raw value is the process variable value buffered in the variable server.
With write access (when used as a unit class (process) from the variable server into the communication component, with a unit class (display) from the control element into the variable server), the conversion is performed in reverse: Raw value = (conversion value - b ) / m
|
X1, X2 |
Y1, Y2 |
|
|---|---|---|
|
General |
Gross value |
Conversion value |
|
Unit class (process) |
PLC values |
Values in the variable server |
|
Unit class (display) |
Values in the variable server |
Values in the display of a control element |
Parameters for module: