slope range

[kmo]

hi,

i have the following VI where I am plotting current Vs optical power. The graph contains the points where the slope of the graph changes significantly. Currently I am I am manually entering this points depending on the curve I see in the graph. I was just wondering is there any way to find this points (where the change in slope is significant)??

thanks a lot in advance.

best,

kmo

Message Edited by kmo on 02-28-2006 12:19 PM

[altenbach]

I don't see any valid reason to split this data into regions with two different slopes. because such regions would be very poorly defined.

You can easily fit it with a second order polynomial instead.

Message Edited by altenbach on 02-28-2006 12:17 PM

[kmo]

Thanks for your reply.

To split the graph is important for the purpose of analysis. I need to ignore the first slope range but need to know where to start the second range where the slope is quite high. In the end slope decreases again and would like to know the slope of this end part.

Basically I am interested in finding out slopes and right now I do that by manually entering the region. I hope it is possible to automate that process.

[pru]

any ideas suggestions! i would really appreciate that.

[DavidJCrawford]

Hi Kmo

Interesting problem so I have had a go at trying to automate the straight line approximation of the last section of your power curve. I was able to do it with the data set you provided but its a bit rough with some  assumptions. It might not work with other data sets but you can try that. I have put some comments into the code to help you get into my world

Out of interest what does the slope and intercept tell you?

Have a look to see if helps you out. VI attached in 7.1

David

[kmo]

Hello david,

thanks for the solution. it is almost what  I wanted.

The slopes basically give the information about optical efficiency that is for a perticular current how much optical power is generated. So it is important to know the range of current in which photodiode is working efficiently. The end of range3 is the point where photodiode begins to generate some optical power, it then increases till the end of range 2 after which the efficiency decreases.

So I am basically interested in finding these two points: the end of range3 and the begining of range1. Any idea on how that can be done. Your solutin gives me the second point but what about the first point, how can i find that !?

Message Edited by kmo on 03-02-2006 06:57 AM

Message Edited by kmo on 03-02-2006 06:58 AM