When using a NTC as a temperature sensor be careful to not running too much current though it, since the current will heat the NTC and introduce a measurement error. For this reason, high value NTCs (10 kΩ or more) are better for thermometers. 

NTCs are usually not factory calibrated and the actual R25 and B25/100 can vary from one NTC to another.  Some sort of circuit adjustment is required to do absolute temperature readings. 

Small value NTCs can make very good inrush current limiters. When a circuit is switched on with an NTC in series, the NTC is initially cold, offering a few Ω of resistance, limiting the inrush current. As soon as the current starts flowing, the NTC heats up and its resistance drops in the mΩ range. 

Converting Resistance To Temperature

A simple way of doing this is to use a lookup table based on the table of values provided for the NTC themistor.  Often these tables don't provide all values (e.g. it might provide a value for each 10°C instead of each 1°C) so you have to create the value in between.  Although this isn't perfect as the real scale is non linear, it is often as good or better than an alternative approach of using the beta based calculation based on the temperature at 25ºC and the beta value, which can be a couple of degree's off due to NTC thermistors being non perfect.  We've found for some thermistors that the manufacturer supplied values differ from a 'perfect' calculation and make their lookup table a better option.

We benefit hugely from resources on the web so we decided we should try and give back some of our knowledge and resources to the community by opening up many of our company’s internal notes and libraries through mini sites like this. We hope you find the site helpful.
Please feel free to comment if you can add help to this page or point out issues and solutions you have found, but please note that we do not provide support on this site. If you need help with a problem please use one of the many online forums.


Your email address will not be published.