Measured value processing
The electrical measured value recorded and digitized by the ADC must or can be changed in the device in order to
- compensate for hardware dependency (keyword: calibration)
- or to reinterpret the measured value on the application side (e.g. to convert the electrical 0..10 V signal of a pressure sensor into a pressure value).
Note: This CoE uses the term "calibration", which is historically used at Beckhoff, although it has nothing to do with deviation statements of a calibration certificate. The vendor or customer calibration data/adjustment data that the device uses during operation in order to maintain the guaranteed analog accuracy is described here.
The measured value can be changed in 3 functional units, all three can be active at the same time:
- Vendor Calibration
The electrical channel is calibrated by Beckhoff in the Vendor Calibration functional unit for compliance with the specified uncertainty (see Technical data, previously: Measuring error). The vendor calibration data from Beckhoff is available in this area.
Parameter:
Index (hex) | Name | Data type | Meaning |
|---|---|---|---|
80n0:0B | Enable vendor calibration | BOOL | enabled by default, the data is taken into account. |
80nF | Vendor calibration data | - | not intended for user modification |
The intermediate value after this functional unit can be viewed in index 0x90n0:05 under “Vendor Calibration”.
The number of setting changes in this functional unit is counted up in index 0 90n2:12 as “Vendor Calibration Counter” and cannot be deleted.
If any parameter in the data area is changed, the counter is incremented. Further changes in the data area within the next 30 seconds are not taken into account for the counter. After this time has elapsed, a parameter change will increment the counter again.
- User Calibration
The "User calibration" functional unit can be used by the user if alternative, system-dependent correction values are to be used permanently.
To be able to work with both INT16-based gain/offset values and Real32 coefficients, processing in "User Calibration" (if Enable User calibration = 1) proceeds as follows:
- for setpoint >=0: "Value after User calibration" = S0 + "Value after Vendor calibration" * S1 +("Value after Vendor calibration")² * S2
- for setpoint <0: "Value after User calibration" = S0 + "Value after Vendor calibration" * S1n +("Value after Vendor calibration")² * S2
Parameter:
Index (hex) | Name | Data type | Meaning |
|---|---|---|---|
80n0:0A | Enable User Calibration | BOOL | disabled by default, calculation only takes place if TRUE |
80n0:17 | User Calibration Offset | SINT16 | 1 bit = MBEnorm./32767, default: 0 |
80n0:18 | User Calibration Gain | UINT16 | 1 bit corresponds to 2-16, so "1" corresponds to 0x7FFF/32767dec |
80nC:01 | User Calibration Data | BYTE4 | 4 bytes of free memory space; here it is possible to store the calibration date in the form of 8 CHAR, for example |
80nC:03…0D | User Scale Gain (Real32) | REAL32 | Real32 coefficients S0/S1/S2/S3/S1n of the calculation polynomial, default: S0=0, S1=1, S1n = 1, S2=0 |
The intermediate value after this functional unit can be viewed in index 90n0:0B.
The number of setting changes in this functional unit is counted up in index 90n2:11 "User Calibration Counter" (cannot be deleted).
Procedure: the counter is incremented the first time any parameter in the data area index 80nC or index 80n0:17/18 is changed; further changes in the data area in the following 30 seconds are not taken into account for the counter. After this time has elapsed, a parameter change will increment the counter again.
- User Scale
The User Scale functional unit is intended for reinterpretations/transformations of the setpoint, so "50 kg" of the controller can become "10 V" with Gain=0.2. It is implemented as a linear transformation with gain/offset..
Parameter:
Index (hex) | Name | Data type | Meaning |
|---|---|---|---|
80n0:01 | Enable User Scale | BOOL | disabled by default, calculation only takes place if TRUE |
80n0:11 | User Scale Offset | SINT16 | is added directly in digits. |
80n0:12 | User Scale Gain | UINT16 | 1 bit corresponds to 2-16, so "1" corresponds to 0x7FFF/32767dec |
80nD:1C | User Scale Offset (Real32) | REAL32 | - |
80nD:1D | User Scale Gain (Real32) | REAL32 | - |
The intermediate value after this functional unit can be viewed in index 0x90n0:0B.
Notice | ||
 | Changing the interface When the interface is changed, the gain and offset are reset to 1 and 0 respectively! | |
Password protection for user data
Some user data are protected against unwanted or inadvertent writing by an additional password to be entered in CoE 0xF009:
- CoE write accesses by the user, PLC or startup entries in Single or CompleteAccess mode
- Overwrite the values by RestoreDefaultParameter Access to 0x80n0 (or 0x80nD, if available)
Use of CoE 0xF009
- Entering 0x12345678 enables the password protection → Object shows "1" (enabled)
Protected objects can now no longer be changed, no error message occurs during a write access! - Entering 0x11223344 disables password protection → Object displays "0" (disabled)
Password protection takes effect with the following AI settings:
Index (hex) | Designation |
|---|---|
80n0:0A | Enable User calibration |
80n0:0B | Enable Vendor calibration |
80n0:17 | User calibration offset |
80n0:18 | User calibration gain |
80nC | User calibration Data |
80nD:17 | Low Range Error |
80nD:18 | High Range Error |
80nD:27 | Low Range Error (REAL32) |
80nD:28 | High Range Error (REAL32) |