Calibrating Measured Values; Calibration When Operating With An External Power Supply - WAGO 750 Series Manual

WAGO I/O System 750
750-1491 2AI Resistor Bridge (Strain Gauge)
9

Calibrating Measured Values

Manufacturer calibration serves to compensate for tolerances in electrical
components of the I/O module.
User calibration allows you to compensate for the tolerances of electronic
components of both the I/O module and connected resistor bridges and to take
into account factors such as component age and different surrounding air
temperatures at the installation site.
User calibration required for each input!
To achieve the greatest possible measurement accuracy for each input, you
must calibrate each input individually!
Preset values can be optimized!
Approximate default values for the respective measurement range are already
stored by default. However, these values can be optimized for the specific site!
The resulting calibration values are stored permanently in the I/O module.
Each supported measurement range has its own storage space available.
9.1 Calibration when Operating with an External Power
Supply
When operating with an external power supply, the measurement input U
referenced internally to a defined, internal potential. In contrast, the measurement
input U is "floating".
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This is necessary in normal operation (i.e., when connecting a resistor bridge),
but it may cause problems with calibration – due to the lack of referencing to a
voltage potential, the measured values react very sensitively to interference and
fluctuate.
For an optimal calibration process, the measuring bridge (or a comparable
resistor network) should remain connected directly to the I/O module. The
calibration voltages, on the other hand, can be fed in at the bridge.
Use the connection type "4-Wire Mode (External Power Supply)" for the
calibration.
For the I/O module, WAGO offers the option of performing the calibration using
the WAGO-I/O-CHECK calibration dialog.
To calibrate the I/O module, proceed as follows:
1. Connect a measuring bridge (or a comparable resistor network) directly to
the I/O module.
Calibrating Measured Values 79
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Manual
Version 1.0.0