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Riccardo25
Italy
1 Posts |
 Posted - 02/07/2009 : 8:11:39 PM
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Origin Ver.8 and Service Release 0 (Select Help-->About Origin):
Operating System: Windows Xp
Hello,
I need to fit a Fowler-Nordheim curve with current saturation effect due to a series resistance R, the formula is:
i = A*(v-R*i)^2*exp(-B/(v-R*i))
where i is the current and v the voltage, A,B,R are the parameters.
I've got two columns in my worksheet, i and v, my idea was to create an additional column equal to the i column and use these values as independent variable like v.
So I created the follow user-defined function:
Dependent variable: y
Independent variables: x, y_1
Parameters: A,B,R
y = A*(x-R*y_1)^2*exp(-B/(x-R*y_1));
It works, but the fit is very poor. I'm not familiar with Origin and curve fitting, how can I implement this kind of recursive fitting?
Thanks in advance,
Riccardo |
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Shirley_GZ
China
Posts |
Posted - 02/12/2009 : 10:49:27 PM
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Hi Riccardo25,
From you post, I suppose you want do fitting using a implicit function, which can't be achieved by curent Origin, unless you can simplify this formula to a explicit function.
Sorry for the trouble brought to you.
Shirely
OriginLab Technical Service Team |
Edited by - Shirley_GZ on 02/12/2009 10:49:49 PM |
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Recursive curve fitting