Linearity of PT1000 at negative temperature

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expertengr

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I have temperature reading system having PT1000 sensors. I need to measure temperature between -20 C and -200 C which these sensors. My question is how much they are linear at -200 C ? If I use two points 0 C and 100 C for calibration purpose and compare the reading with reference calibrated system and use first order statistics to calibrate PT1000 then how much they will be off at -200 C ?
 

These PT100 / PT1000 sensors are not linear, as indeed no sensor is linear at all, but they have a region where the characteristic can be approximated by a straight line the smaller the span, and also the more acceptable is the error tolerance you define. What is done in the process of calibrating these sensors in your program is to obtain parameters of a polynomial optimized for each device measured and store them at a non volatile memory. You should have a look on polinomial regression algorithms in order to embeed that feature in the program in runtime (I'm assuming you are reading the sensor through a uC unit).
 


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