Hello Bob,
I am stuck with external calibration. I am currently using method as described in Analog Device's AN709(www.analog.com/static/imported-files/application_notes/AN-0970.pdf) to calibrate & remove the offset from readings. I am using high precision fixed resistors for the process.
Whichever 2 points I calibrate as per this method, they get calibrated well, but in-between and outside these points I again get offsets from actual resistance values. As I move away from the calibration points, this offset increases---in some ranges it is+ve and in others it is -ve. Please note that this offset appears in calculated RTD resistance itself.
Can you some throw some light on this issue ? Do I need to do multi-point calibration, 0-50, 51-100, 101-150 etc. ? My range is 10-500 deg C, that will be too much calibration data..
Any other method to calibrate ?
Regards,
Saumitra A Deshpande