quincy:
ok thanksI try to use termistor, I measure value by voltage divider use Steinhart & Hart equation to calculate tempereature. But when I try put thermistor to boiling water, it shows only 97,43C. I think that problem can be 5V voltage source on arduino board, is it exactly 5.00V or it can be less?
That amount of difference is possibly due to other things, not arduino 5 volt. Do you have a reliable multimeter to directly get the resistance and calculate the temperature? Chances are, the thermistor has accuracy of +-2 degree. Thermistors need some calibration since every single one is different. If you interchange two, they read different numbers. What is the interchangeability parameter of the thermistor?