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Zaidan7
Malaysia
2 Posts |
 Posted - 11/14/2017 : 7:42:15 PM
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Origin Ver. and Service Release (Select Help-->About Origin): b9.4.0.220 (Academic)
Operating System: Win 8.1
Hello!
I'd like to ask regarding my problem with nonlinear curve fit.
I tried to fit the graph using ln (abs) scale for y-axis using one-diode equation as follow.
ln( abs( Jo*(exp(e*(x-( (exp(y))*Rs) ) / (n*Kb*T) )-1) +(((x-(exp(y))*Rs))/Rsh)-Jph ) ) -((y))
As seen on the attached image, the right-hand-side of the plot was well-fitted. However, I couldn't manage to fit the other side no matter how much I tried to change the fitting parameters. Could you please help me to solve this matter.
Thanks,
Best regards
Zaidan
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Edited by - Zaidan7 on 11/14/2017 9:28:14 PM |
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Echo_Chu
China
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Posted - 11/15/2017 : 04:53:26 AM
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Hi,
Your function is similar to Modified Diode Equation, which we are going to added as build-in function in our next version.
I also upload the FDF file of Modified Diode Equation to the post below. You can look at how we work out the function and create your own.
http://www.originlab.com/ftp/forum_and_kbase/Images/ModDiode.zip
Please note that the function is a implicit function, we should use Implicit Curve Fitting tool to do the fitting.
You can look at the tutorial below for fitting wiht implicit funciton.
https://www.originlab.com/doc/Tutorials/ImplicitFit-3Var
Echo
OriginLab Technical Service |
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Zaidan7
Malaysia
2 Posts |
Posted - 11/15/2017 : 7:26:15 PM
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Good morning!
Thank you very much for your big help !
I have tried using your FDF file and the plot was fitted perfectly as in the attached image below.
However, I've found out that the values of Rs and Rsh are quite weird. While Rs is lower than the estimated value (+-4), Rsh is always 0. As far I as I know, Rsh should be relatively bigger than Rs (e.g. >3000).
Best regards,
Zaidan |
Edited by - Zaidan7 on 11/15/2017 7:32:53 PM |
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Problem with Nonlinear Curve Fit