Go Down

Topic: Can't get correct value from thermistor (Read 1 time) previous topic - next topic


Using PapaG help, I got it working! Thanks!


@ dhenry... did you read the whole post... you know, from the first posting??

--> WA7EMS <--
"The solution of every problem is another problem." -Johann Wolfgang von Goethe
I do answer technical questions PM'd to me with whatever is in my clipboard


You can also rewrite your Rth calculation to fit your setup:

Rth = (Vin - V) * R1 / V.

Papa G

Using PapaG help, I got it working! Thanks!

You're welcome, erbedo.

You can try an experiment if you're curious. If you select 50K for your series resistor instead of 10K, you'll notice that the voltage vs. temperature curve is far more linear over the range 0-100 Celsius. So much so that, if your interest is a thermometer for measuring the temperature of your environment, you might not even need the Steinhart-Hart function.

If you wire your circuit the way you had it originally, and use the right equation, you get a response curve that is fairly linear in the temperature range above 40 degrees Celsius but as michael_x commented, you don't get much of a voltage variation so your resolution is less. If you substitute the 50K resistor again, you get a fairly linear curve at room temperatures but again, not much resolution.

So, you see, there are a few trade-offs you can consider in your design.

Go Up