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Calculate thermistor coefficents

  1. Nov 22, 2011 #1
    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.
     
  2. jcsd
  3. Nov 22, 2011 #2
    1st step is to take ln of both sides of the equation.
     
  4. Nov 22, 2011 #3
    Hi grzz, how can I take the ln of both sides if B is unknown?
     
  5. Nov 22, 2011 #4
    R = R[itex]_{o}[/itex]e[itex]^{\frac{B}{T}}[/itex]

    then

    lnR = lnR[itex]_{o}[/itex] + B ([itex]\frac{1}{T}[/itex])

    Compare with

    y = c + mx

    which is a straight line graph.
     
  6. Nov 22, 2011 #5
    Ok I think I'm getting there. So Ro is resistance at an arbitrary temperature eg. room temperature? So what is the first R?
     
  7. Nov 22, 2011 #6
    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 ...
     
  8. Nov 22, 2011 #7
    Ok good stuff. I know that the slope is equal to B. Is R0 then equal to the intercept?
     
  9. Nov 22, 2011 #8
    Ro = intercept on the R-axis.
     
  10. Nov 22, 2011 #9
    Thanks a million grzz!
     
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