Calibrating Measured Values - WAGO 750-489 Manual

WAGO-I/O-SYSTEM 750
750-489 4AI RTD/TC/Strain Gauge Ex i
9

Calibrating Measured Values

The precision that can be achieved in temperature measurement depends on the
following properties:
• The accuracy of the transducer in the RTD/TC module
• The accuracy of the linearization in the RTD/TC module
• The quality of the electrical contact points
• The quality of the thermal contact points
• The accuracy class of the thermal sensor and compensating lines
• The thermal stability in the environment of the RTD/TC module
The first two issues are quality characteristics of the WAGO product; all other
properties are up to the user.
For the RTD/TC module, WAGO offers the option of using the WAGO-IO-CHECK
calibration dialog to compensate tolerances throughout the entire measurement
chain. This requires reference values to be available for temperatures of the
object to be measured.
Example 1
Requirements:
• The WAGO node must be installed in the control cabinet; the temperature
in the control cabinet must have settled and be constant.
• A thermocouple line must be laid up to the measuring point, but not yet
welded on there.
1. Connect a calibrator to the open ends of the thermocouples.
2. Use WAGO-IO-CHECK to calibrate the equipment via this calibrator.
3. Remove the calibrator.
4. Weld the thermocouple and secure it to the measuring point.
Example 2
Requirements:
• The WAGO node must be installed in the control cabinet; the temperature
in the control cabinet must have settled and be constant.
• A thermocouple line must be laid up to the measuring point.
• The temperature of the object to be measured must be known precisely at
at least two points (e.g., eutectic phase changes => solid and liquid lines)
1. Calibrate to these points.
The resulting calibration values are stored permanently in the I/O module.
Each supported sensor type has its own storage space available.
Calibrating Measured Values 149
Version 1.1.0, valid from FW Version 02
Manual