# [SmoothTermistor] What's the nominal resistance

Good evening,

I need to calculate the temperature of the bud with the SF-110 sensor.
As you can see on page 10, there is the diagram of the divider. (Termistance with 24.9K resistance)

I am interrested to use that library SmoothTermistor with 3.3V cirtcuit and HREF

I have a doubt about that section . There are two value of rsistance

• the nominal resistance
• the series resistance

I suppose the serie resistance value should be replace with 249000, but if that's right, what about the nominal resistance?

And what abour the beta coefficient? The SF-110 doc says

where A = 1.129241 x 10-3, B = 2.341077 x 10-4, and C = 8.775468 x 10-8(Steinhart-Hart coefficients)

Someone has an experience about coefficent. I am confused about Beta coefficient and Steinhart-Hart coefficients

Hope, there are scientists around

The Steinhart-Hart coefficients and the beta coefficient (a simplification) are explained in Steinhartâ€“Hart equation - Wikipedia

Voltage dividers are explained in Voltage Divider

The thermistor nominal resistance is its actual resistance as some standard temperature, usually 25 C.

If you want to be confident in getting accurate measurements, you have to check the calibration of the probe, AND the code, using either temperature standards like ice water, or against a calibrated thermometer.