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[on:]

hi guys

im new to the arduino game, i recently posted a question in the programming section regarding using the max6675 to cover ranges -50 - +150

seems the chip will not do that, so im looking into going back to RTD/NTDs

after having looked through code for thermistor4 (link below) my head as a tad numb, can anyone guide me to restructure some code to cover my specified ranges ? :

http://www.arduino.cc/playground/ComponentLib/Thermistor4

[Reply #1 on:]

Covering your specified range is not a matter of restructuring some code...  You have to purchase a thermistor that will operate over the required range, calibrate it, plug in the calibration values and tweak the results until it comes out matching reality fairly closely.

Thermistors have a non-linear resistance curve.  The calibration is needed to characterize the curve so the software can calculate the temperature by measuring the resistance.  Get the characterization values correct and you will have a thermometer.

Another choice is an integrated temperature transducer such as the Analog Devices AD22100KTZ.  Costs $4.23 each from DigiKey.  Accurate to 1/2°C over the -50 to +150°C range. 

http://www.analog.com/static/imported-files/Data_Sheets/AD22100.pdf

[Reply #2 on:]

thanks john, having some perspective on that has helped me understand the problem, im still training my brain to understand this haha, my background has been purely electronics and no programming until now

thank you for the suggestion of the ad22 sadly it is to large for my application, but thanks anyway !

thanks again !