| Author |
 Topic  |
|
|
giffyjie
Singapore
2 Posts |
 Posted - 10/15/2014 : 06:21:05 AM
|
hi,
i'm trying to fit a I-V curve with this defined equation,
and my I-V curve looks like
I couldn't compile the function that i have put. I'm not sure if i have stated the wrong variables. But this is what i put for
Independent Variables: V,i
Depdendent Variables: i(V)
Parameter Name: Rs,Rp,iLt,io
constant: k=1.38*10^(-23)
q=1.6*10^(-19)
T=300
function: I(V)=io*[exp(q*(V-(i*Rs))/(k*T))-1] + ((V-(i*Rs))/Rp)-iLt
do let me know my mistake. thanks.
regards,
YJ |
Edited by - giffyjie on 10/15/2014 09:49:02 AM |
|
|
JacquelineHe
287 Posts |
Posted - 10/15/2014 : 10:36:04 PM
|
Hi,
When you create the usef-defined function, you choose Origin C as the Function Type, right?
I suggest you do not use i(V) as Depdendent Variables.
Please try to use y to instead of i(V).
And set the Function to:
y=io*(exp(q*(V-(i*Rs))/(k*T))-1)+ ((V-(i*Rs))/Rp)-iLt
Thanks
Jacqueline
OriginLab |
Edited by - JacquelineHe on 10/15/2014 10:37:08 PM |
 |
|
|
giffyjie
Singapore
2 Posts |
Posted - 10/16/2014 : 05:31:49 AM
|
Hi,
Thanks for your reply.
I have made some changes and this is the following equation that used:
i=io*(exp(q*(V-(i*Rs))/(k*T))-1)+ ((V-(i*Rs))/Rp)-iLt
and successfully compiled the code.
With the following parameters and variables.
Independent Variables: V
Depdendent Variables: i
Parameter Name: Rs,Rp,iLt,io
constant: k=1.38*10^(-23)
q=1.6*10^(-19)
T=300
However, when I'm trying to fit my curve into the function, I've problem again.
I selected my data input using the "Selection on active plot" tool. Then i clicked into 'Analysis' tab and try to fit my curve with my defined function above.
After selecting, I was prompt with this message after clicking on chi-square icon "Fit did not converge - Parameter(s) Rs,Rp,iLt,io are not properly initialized. Please check and correct their values."
After randomly initialize the parameters Rs,Rp,iLt,io and click chi-square icon again, i'm given a value. But when i click on the "fit until converge" icon i receive the following message
"Fit did not converge - mutual dependency exists between parameters.
You may have overparameterized the fitting function. Fixing one of them may eliminate this problem."
What puzzled me was, did I key in the wrong variables and parameters when i defined my function. Also, the data that I have is V & i. I would like to find Rs,Rp,Io,Ilt through this fit.
Please help. Thanks.
regards,
YJ |
Edited by - giffyjie on 10/16/2014 06:37:12 AM |
|
|
|
JacquelineHe
287 Posts |
Posted - 10/20/2014 : 05:49:17 AM
|
Hi YJ,
Thanks for your reply.
I am afraid that I am not sure why the Depdendent Variables: i is used in both right and left part in your fitting function: i=io*(exp(q*(V-(i*Rs))/(k*T))-1)+ ((V-(i*Rs))/Rp)-iLt
And if you do not mind I suggest you can send project file and the .FDF file (user-defined fitting function file) to our Tech Support department, so that we can look into the problem?
The FDF file path you can check from Fitting Function Organizer (Tools: Fitting Function Organizer menu).
Please click on the link "Send File to Tech support" on the right-top of this page.
And please tell us your detailed version and serial number information in your email.
Thanks
Jacqueline
OriginLab |
|
|
| |
Topic |
|
|
|
User-defined Curve fitting