I recently purchased a 10k ohm NTC thermistor from a local electronics store for which I couldn't find a datasheet. By going through the post How to measure temperature using a NTC thermistor I understand how to calculate the resistance. My questions are:
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Can I use B constant for my 10k ohm NTC thermistor as 4050 or is there any other way to calculate the B constant?
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Will the B constant vary between different vendors?
Best Answer
No, yes and yes, in that order.
B values vary a lot, typically between 3000 K and over 5000 K, not only between manufacturers but between different parts from the same manufacturer. Even apparently identical parts from one manufacturer will be subject to a tolerance on their B values.
You can measure the resistance of the thermistor at various temperatures and plot the log of resistance against reciprocal absolute temperature, ie ln(R) against 1/Tabs.
The slope of the best-fit straight line through the points will be an approximation of the B value (which as Olin notes is itself an approximation of the Steinhart-Hart cubic, itself an approximation ...) .
For the benefit of those who have not heard of the B (or \$\beta\$) parameter, there are explanations on Wikipedia and on this manufacturer's website (the first I found with a google search).