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Calculating tau from measured time and temperature

  1. Mar 16, 2009 #1
    so i have two data points. T1 = 64.68, t1 = 200.7 and T2 = 84.15, t2 = 243. I want to use this data to find the tau value of the exponential curve the data came from.

    I was trying to use simultaneous equations but got stuck. Can anyone help me with this?

    64.68 = Tf(1-exp(-200.7/Tau))
    84.15 = Tf(1-exp(-243/Tau))

    I got to 19.47 = 84.15*(exp-200.7/Tau) - 64.68*(exp-243/Tau)

    I want to get a value for Tau but i can't figure out how to simplify/remove the exponential terms.
    Any help is appreciated
  2. jcsd
  3. Mar 17, 2009 #2
    What are you trying to fit? A function of the form

    [tex]f(t) = T_f(1 - exp(\frac{-t}{\tau}))[/tex]

    Your best bet it to evaluate it numerically, don't think it can be analytically solved...

    I get tau = -327.156 and Tf = -76.3792
    Last edited: Mar 17, 2009
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