Data stream and calibration
Data stream
The flow chart at the bottom (Fig. Data stream representation of the EL31xx) illustrates the data stream in the EL31xx (processing of the raw data).
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 object 0x80nE:01. 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 fig. Data stream representation of the EL31xx).
Calculation | Designation |
|---|---|
XF = f(XADC) | 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 | Designation | 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. |
Vendor calibration, index 0x80n0:0B
The vendor calibration is enabled via index 0x80n0:0B. Parameterization takes place via the indices
- 0x80nF:01 Vendor calibration: Offset
- 0x80nF:02 Vendor calibration: Gain
User calibration, index 0x80n0:0A
The user calibration is enabled via index 0x80n0:0A. Parameterization takes place via the indices
- 0x80n0:17 User calibration: Offset
- 0x80n0:18 User calibration: Gain
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
- 0x80n0:12 User scaling: Gain
| Producer Codeword Beckhoff reserves the right to implement the basic calibration of the terminals. The Producer codeword is therefore at present reserved. |