We are designing a system with RTD measurement circuit. We are using CN0287 as a reference circuit for our design.
Regarding the calibration of the RTD measurement, software user guide of CN-0287 highlights the options provided as
1) ADC Calibration - Which contains both Zero scale Calibrate & Full scale calibrate
2) System Calibration - Which contains both Zero scale Calibrate & Full scale calibrate
Below is our understanding of the calibration with respect to error sources :
- ADC Zero scale calibration - Removes ADC offset error
- ADC Full scale calibration - Removes ADC gain error
- System Zero scale calibration - Removes error due to Rref tolerance
- System Full scale calibration - Removes any system gain errors if present
Is our understanding correct?
There are errors such as ADC INL which are not linear to the input voltage. Thus if we calibrate only with zero & full scale inputs, these non-linear errors will not be calibrated. Thus having a calibration over the input voltage range (indirectly RTD range), results in a better accuracy.
Is this correct ? If so, is there a specific reason for not calibrating over the input range in case of CN-0287 ?
Looking forward to response.
Thanks & Regards,
Suresha N S