How do I get this Knee?

[ChrisJ]

Hello Guadier,

There is not a built in function in LabVIEW that I am aware of to find the "knee" for you. However, as several members have mentioned above, you can implement your own algorithm to find the slopes for you. Once you have the algorithm nailed down you can make it into a subvi and reuse it in other places.

Regards,
Chris J

[Gaudier]

I know about nuclear stuff not programing stuff, so as several members have done, your talking me in chineese. How do I make an algorithm that gets the maximum of the first derivate of my graph were x is a voltage sweep(v) and y is the current(I)? Then using this maximum called plasma potential (vp) I need (vp-v) in the x-axis and ln(|I|) in Y-axis, so I can get the intercept(b), where vp-v=0, and calculate e^b to get the saturation current (Ies) and there is my "knee" (Vp, Ies).

Thanks for your time.

[ChrisJ]

Hello Guadier,

LabVIEW is great because of the relatively short learning curve, but just like any other programming language there is still a little investment required to learn the environment so you can program anything you like. Some of the best information I have found is on an academic site that includes tutorials and getting started information. Whether you are in the academic field or not, it still contains some great information. I would definitely check out the 3 and 6 hour tutorials as well as the getting started guide to familiarize yourself with LabVIEW. NI also offers instructor led and self paced classes to give you a more in depth understanding of LabVIEW and proper programming practices. As far as examples go, I have attached a screenshot of a simple program to generate sample data, take the first derivative, and find the max. I hope this gets you started. Best of luck!

Regards,

Chris J

How Can I Learn LabVIEW?

http://forums.ni.com/ni/board/message?board.id=140&message.id=14894&view=by_threading&page=2

Getting Started with LabVIEW

http://digital.ni.com/manuals.nsf/websearch/07F9CD824F66237A86257046006F7C5D

Message Edited by ChrisJ on 12-30-2005 12:25 PM

[Gaudier]

 Thanks!