Calculate thermistor coefficents

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Discussion Overview

The discussion revolves around calculating the coefficients R0 and B for an NTC thermistor using data from a temperature sensor. Participants explore the mathematical relationship between resistance and temperature, specifically through the equation R = R0.e^(B/T), and the steps involved in deriving these coefficients from experimental data.

Discussion Character

  • Technical explanation
  • Mathematical reasoning

Main Points Raised

  • One participant describes the initial equation relating resistance and temperature and expresses uncertainty about calculating the coefficients R0 and B.
  • Another participant suggests taking the natural logarithm of both sides of the equation to facilitate the calculation.
  • A participant questions how to take the logarithm if B is unknown, indicating a potential misunderstanding of the process.
  • Further clarification is provided that the equation can be rearranged to a linear form, allowing for the identification of R0 and B from a graph.
  • Participants discuss the meaning of R0 as the resistance at an arbitrary temperature, such as room temperature, and clarify that R represents the resistance at temperature T.
  • There is a consensus that plotting ln(R) against 1/T will yield a straight line, where the slope corresponds to B and the intercept relates to R0.

Areas of Agreement / Disagreement

Participants generally agree on the method to derive R0 and B from the equation and the graphical representation, but there are moments of uncertainty regarding the definitions and initial conditions for R and R0.

Contextual Notes

Some assumptions about the temperature at which R0 is defined and the specific values of resistance at different temperatures remain implicit and are not fully resolved.

Who May Find This Useful

This discussion may be useful for individuals working with thermistors, those interested in temperature-resistance relationships, and anyone looking to understand the mathematical modeling of thermistor behavior.

paulie walnut
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I'm using Visual Basic to graph data from a NTC thermistor and temperature sensor (via a DAC card). I want to calculate the thermistor coefficients R0 and B according to the equation (R0 should have subscript 0):
R = R0.e^B/T
T=absolute temperature
R=resistance

I have calculated ln(R) and 1/T but am unsure of how to calculate the coefficients. Any help would be greatly appreciated.
 
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1st step is to take ln of both sides of the equation.
 
Hi grzz, how can I take the ln of both sides if B is unknown?
 
R = R_{o}e^{\frac{B}{T}}

then

lnR = lnR_{o} + B (\frac{1}{T})

Compare with

y = c + mx

which is a straight line graph.
 
Ok I think I'm getting there. So Ro is resistance at an arbitrary temperature eg. room temperature? So what is the first R?
 
R is the value of the resistance at temperature T (in Kelvin).

So one plots a graph of lnR on the vertical axis against 1/T on the horizontal axis and then the intercept on the R-axis will be ... and the slope of the graph will be ...
 
Ok good stuff. I know that the slope is equal to B. Is R0 then equal to the intercept?
 
Ro = intercept on the R-axis.
 
Thanks a million grzz!
 

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