Setpoint processing, user/vendor calibration
The electrical set output value generated and digitized by the DAC must or can be changed in the device in order to
- compensate for hardware dependency (keyword: calibration)
- or to make application-specific changes
The output value can be changed in 3 functional units, all 3 can be active at the same time:
- User Scale
- User calibration
- Vendor calibration
The "User/vendor calibration" functional unit is intended for correcting hardware-specific influences. They are implemented as 3rd order polynomial transformations (offset, gain, x², x³).
Note: The term "calibration", which is historically based at Beckhoff, is used here in the CoE, even if it has nothing to do with 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 analog accuracy.
- 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 | Name | Data type | Meaning |
|---|---|---|---|
80n0:07 | Enable User calibration | BOOL | disabled by default, calculation only takes place if TRUE |
80n0:17 | User calibration offset | SINT16 | 1 bit = AEWnom / 32767, |
80n0:18 | User calibration gain | UINT16 | 1 bit corresponds to 2-16, "1" therefore corresponds to x7FFF/32767dec, |
80nC:01 | User calibration data | BYTE4 | 4 bytes of free memory space; |
80nC:03..0D | User Scale Gain (Real32) | REAL32 | Real32 coefficients S0/S1/S2/S3/S1n of the calculation polynomial, |
The intermediate value after this functional unit can be viewed in index 90n0:0A.
The number of setting changes in this functional unit is counted up in index 90n2:12 "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.
- Vendor Calibration
The electrical channel is calibrated by Beckhoff in the Vendor Calibration functional unit for compliance with the given uncertainty specification (see Technical Data, previously: output error). The vendor calibration data from Beckhoff is available in this area.
Parameter:
Index | Name | Data type | Meaning |
|---|---|---|---|
80n0:08 | 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 90n0:0B under 'Value after Vendor Calibration'.
The number of setting changes in this functional unit is counted up in index 90n2:12 as 'Vendor Calibration Counter' and cannot be deleted.
Procedure: the counter is incremented the first time any parameter in the data area 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.
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 | Designation |
|---|---|
80n0:07 | Enable User calibration |
80n0:08 | Enable Vendor calibration |
80n0:17 | User calibration offset |
80n0:18 | User calibration gain |
80nC | User calibration data |
80nD:1A | Limiter Low Value |
80nD:1B | Limiter High Value |