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90 Commissioning
WAGO-I/O-SYSTEM 750
750-450 4 AI RTD
Manual
Version 1.2.0
7.1.1.3.5.1 Application example for calibration
Sample calculation for 2-wire connection technology
Note here that the following example is based on calibration of an I/O module for
operation using 2-wire connection technology.
A 2-point measurement with reference resistance values is performed for
calibration.
Example:
Measurement 1: y1= 100 Ohm
Measurement 2: y2= 4000 Ohm
The two values for the measured resistance must first be converted to the
corresponding A/D raw values. The following equation is used for this conversion:
A/D raw value = (measured resistance × ((2^24) − 1)) / 5050
Different factors for 2 and 3-wire connection technology
When converting the measured resistance to A/D raw values, a factor of 5050
applies to 2-wire connecting technology.
> A/D raw value = (measured resistance × ((2^24) − 1)) /
5050
A factor of 5047 applies to conversion of measured resistance to A/D raw values
for 3-/4-wire conntection technology.
> A/D raw value = (measured resistance × ((2^24) − 1)) /
5047