Calibration
Vendor calibration, index 0x80n0:0B
The vendor calibration is enabled via index 0x80n0:0B. Parameterization takes place via the indices
- 0x80nF:01
Thermocouple offset (vendor calibration) - 0x80nF:02
Thermocouple gain (vendor calibration) - 0x80nF:03
Reference point offset [Pt1000] (vendor calibration) - 0x80nF:04
Reference point gain [Pt1000] (vendor calibration)
 | Vendor and user calibration User calibration (index 0x80n0:0A) should only be performed instead of the vendor calibration (index 0x80n0:0B), but this is generally only necessary in exceptional cases. |
User calibration , index 0x80n0:0A
User calibration is enabled via index 0x80n0:0A. Parameterization takes place via the indices
User scaling, index 0x80n0:01
The user scaling is enabled via index 0x80n0:01. Parameterization takes place via the indices
- 0x80n0:11
User scaling offset
The offset describes a vertical shift of the characteristic curve by a linear amount.
At a resolution of 0.1°, 1 digit(dec) corresponds to an increase in measured value by 0.1°
At a resolution of 0.01°, 1 digit(dec) corresponds to an increase in measured value by 0.01 - 0x80n0:12
User scaling gain
The default value of 65536(dec) corresponds to gain = 1.
The new gain value for 2-point user calibration after offset calibration is determined as follows:
Gain_new = reference temperature / measured value x 65536(dec)
Calculation of process data
The concept "calibration", which has historical roots at Beckhoff, is used here even if it has nothing to do with the deviation statements of a calibration certificate. Actually, this is a description of the vendor or customer calibration data/adjustment data used by the device during operation in order to maintain the assured measuring accuracy.
The terminal constantly records measured values and saves the raw values from its A/D converter in the ADC raw value objects 0x80nE:01, 0x80nE:02. After each recording of the analog signal, the correction calculation takes place with the vendor and user calibration data as well as the user scaling, if these are activated (see following picture).
Calculation | Designation |
|---|---|
XADC | Output of the A/D converter |
XF | Output value after the filter |
YH = (XADC – BH) x AH x 2-14 | Measured value after vendor calibration, |
YA = (YH – BA) x AA x 2-14 | Measured value after vendor and user calibration |
YS= YA x AS x 2-16 + BS | Measured value following user scaling |
Name | Name | Index |
|---|---|---|
XADC | Output value of the A/D converter | |
XF | Output value after the filter | - |
BH | Vendor calibration offset (not changeable) | |
AH | Vendor calibration gain (not changeable) | |
BA | User calibration offset (can be activated via index 0x80n0:0A) | |
AA | User calibration gain (can be activated via index 0x80n0:0A) | |
BS | User scaling offset (can be activated via index 0x80n0:01) | |
AS | User scaling gain (can be activated via index 0x80n0:01) | |
YS | Process data for controller | - |
| Measurement result The accuracy of the result may be reduced if the measured value is smaller than 32767 / 4 due to one or more multiplications. |