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View Full Version : Finding the time constant of a first order system


RC51
Oct27-09, 10:04 PM
1. The problem statement, all variables and given/known data
I am trying to find the time constant of a thermometer that is taken from boiling water (100 deg C) and placed in ice water (0 deg C)


2. Relevant equations
See attached


3. The attempt at a solution

Using the equation in picture #1: I understand that I have to plot the data and do a linear regression, and that m = 1/tau and tau is the time constant. I know that T(0) is 100 deg C, and T inf is 0 deg C, but I am confused as to what I put in for T(t)?

Using the second equation attached, do I use the function generated by plotting the data in the table attached (#3), and insert that for T(t)??

I am thoroughly confused, and I am sure this is fairly easy, but I've been racking my brain and can't seem to figure it out.