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Screensize: 640 x 480 800 x 600 1024 x 768 1280 x 1024 UserName: Password: Anti-Spam Code: Format Mode: Basic  Help  Prompt  Format: Font Andale Mono Arial Arial Black Book Antiqua Century Gothic Comic Sans MS Courier New Georgia Impact Lucida Console Script MT Bold Stencil Tahoma Times New Roman Trebuchet MS Verdana   Size 1 2 3 4 5 6   Color Black Red Yellow Pink Green Orange Purple Blue Beige Brown Teal Navy Maroon LimeGreen Message: * HTML is OFF * Forum Code is ON Smilies [quote][i]Originally posted by Drone0[/i] [br]Origin Ver. and Service Release (Select Help-->About Origin): originpro 64-bit 9.3.1 Operating System: win 10 64 bit Hi all, I have some problem for implicit fitting, I tried to figure out parameter from nonideal IV curves using fitting ftn. [img]http://pveducation.org/sites/default/files/PVCDROM/Solar-Cell-Operation/Equations/eq082.png[/img] this is nonideal diode function. so I use this for fitting. like "f=Is*(exp((q*(V-I*Rs))/(k*T))-1)+((V-I*Rs)/Rsh)-I" T : temperature Is : saturation current Rs : series resistance Rsh : shunt resistance q : electron charge I : current V : bias voltage however It doesn't work and shows "Fit did not converge - reason unknown." messege and linear graph. So then I tried to refer to similar circumstance "fitting diodic curve" [url]http://www.originlab.com/forum/topic.asp?TOPIC_ID=20339[/url] but still no affect. I tried procesure as follow [img]http://oi63.tinypic.com/2dsnvwn.jpg[/img] I chose implicit because diode function is "y=x~~y" form. [img]http://oi68.tinypic.com/2btr4p.jpg[/img] [img]http://oi66.tinypic.com/24xdlz8.jpg[/img] [img]http://oi67.tinypic.com/j6iwcx.jpg[/img] then I click fit. however [img]http://oi63.tinypic.com/2r7pno4.jpg[/img] [img]http://oi67.tinypic.com/2poqt5z.jpg[/img] error messege and linear form graph which doesn't look like original diodic curve. (I also use initialize parameters, fit until converged. but no affect) is it problem of software or just wrong input setting? Yoo [/quote]   Check here to include your profile signature. Check here to subscribe to this topic.