Table of Contents
Data Transformation
Overview
Data transformations are channel-local.
They transform the value of one channel and keep the same Channel ID.
one input channel -> same output channel
They do not read other channels. Multi-channel corrections or calculations are handled later, after Data Channels are created.
It is valid to combine several conversions into one Scaling transformation. However, if performance is not critical, separate transformation steps are preferred because they make the signal path easier to understand, review and maintain.
Default read direction:
Device/API Value -> Application Value
Default write direction:
Application Value -> Device/API Value
The transformation chain is ordered. Each transformation expects a specific input unit and produces a defined output unit.
Transformation Types
| Type | Purpose |
|---|---|
| Scaling | Converts a device signal into a physical value based on device or sensor information. |
| Unit Conversion | Converts between units of the same physical quantity. |
| Calibration Correction | Corrects an application value using correction data derived from calibration results. |
| Custom Adjustment | Optional project-specific one-channel transformation. |
| Inverting | Negates a boolean value. |
Scaling
Converts a device signal into a physical value.
Scaling is usually based on a device manual, sensor datasheet or configured device range.
If the device/API already provides the required physical value, no Scaling is needed.
Examples:
-
0-10 V → 0-16 bar
-
4-20 mA → 0-100 L/min
Unit Conversion
Converts between units of the same physical quantity.
Unit Conversion changes the unit of an already existing physical value. Scaling creates the physical value from the device signal (based on the datasheet).
Use it when the physical value exists, but the application should use another unit.
Examples:
-
bar → Pa
-
degC → K
Calibration Correction
Corrects an already meaningful value using correction data derived from calibration results.
The transformation does not perform calibration. Calibration is the process of comparing a measuring system against a reference.
Calibration Correction only applies the resulting correction values.
The correction must be applied in the unit for which the correction data was created.
Examples:
-
measured pressure in bar → corrected pressure in bar
-
measured temperature in degC → corrected temperature in degC
Custom Adjustment
Optional project-specific transformation for special one-channel behavior.
Use it only if the required conversion does not fit Scaling, Unit Conversion or Calibration Correction.
A Custom Adjustment still follows the channel-local rule.
one input channel -> same output channel
Examples:
-
vendor-specific value mapping
-
project-specific legacy formula
Inverting
Boolean transformation that negates the value.
Use it for active-low or normally-closed logic.
Examples:
-
hardware TRUE → application FALSE
-
normally-closed level switch → logical open/closed state
Chain Examples
Analog sensor:
Device/API Value in V -> Scaling to bar -> Unit Conversion to Pa -> Calibration Correction in Pa -> Application Value in Pa
API device already returning physical values:
Device/API Value in degC -> Calibration Correction in degC -> Application Value in degC
No unit change required:
Device/API Value in V -> Scaling to bar -> Calibration Correction in bar -> Application Value in bar
Boundary
Transformations do not use other channels.
Not a Data Transformation:
pressure + supply voltage -> corrected pressure
This is a project-specific calculation and creates a new derived Data Channel.