What's the best NTC nominal resistance?

Hello,

NTC thermistors are available with different nominal resistance values like 10k or 100k. But why? What's the difference between them? Obviously I need to match my voltage divider's fixed resistor with the used NTC, but what other reasons are there to pick any specific NTC type? Is it accuracy, self-heating (through the flowing current), noise immunity, or what else, and how do they relate? Is lower or higher better?

If the application is relevant: I'm interested in reading the PCB temperature in normal indoors conditions (say 10 to 60 °C) with an ADC. This should be a (poor man's?) overheating safety method. My code will regularly read the temperature and ask for assistance or do something else if the temperature rises above a healthy level.

Yes the last two. The resistance you pick is a compromise between self heating and noise immunity.

Thank you. Then I guess higher resistance values mean less current which results in less heating and less noise immunity? Do some broad general recommendations exist on which value to pick? My supplier has 10k, 47k and 100k, where 10k costs 10% more than the others.

Correct.
Look at the data sheet because the curves will be different as well, so it is best to also pick a curve that has the most resolution in your temperature rang of interest.

I think this is super accurate at 25˚C.

I'm afraid I don't know how to do that. There are no curves in the datasheet, just long tables. The models available are TN20-3H103K (10k), -3U473K (47k) and -4C104K (100k). All have the same tolerance values and temperature range. I don't know what that "B" value means, just how to put it into a formula to convert the ADC reading.

See this explanation and this SRS Thermistor Calculator

Maybe this is an easer read

If there was a best one, then there would only be one.

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I'm not sure what the full Steinhart-Hart equation is good for. It requires A, B and C parameters to work. All datasheets I've seen up to now only provide the B value, so I need to use the other "B parameter" equation anyway.

Still those articles don't seem to explain effects of different B values.

Anyway, I'll just use the middle value of 47k. I conclude that it doesn't seem to be too important which value to choose. Just take what's available. As long as you don't understand all the physical details, you shouldn't notice a difference.

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