Using LabVIEW to Generate an XY Graph of Multiple, Indexed Plots?

[MJ1619]

Hello,

I have written a LabVIEW Program (using 8.2.1) to characterize FETs using GPIB instruments. At it's most basic level, the program sets a voltage across the Gate-Source terminals of the FET, sets a voltage across the Drain-Source terminals of the FET, reads this second voltage, and then reads the Drain-Source current. The Drain-Source voltage is then increased, the current read, and so on. In this manner, the Drain-Source voltage is swept from 0V to some defined maximum (dependent on the FET being tested) and an array of data (I_{DS} vs. V_{DS}) is generated. The Drain-Source is then reset to 0, the Gate-Source voltage is increased, and the entire process is repeated.

My problem is this: I need to generate a single Graph  (I think it should be XY, but not entirely certain), that plots all of these IV curves (each curve for each Gate-Source voltage) and indicates the Gate-Source voltage for each curve (in an indexed legend of some sort). Does anyone have any suggestions about how I should do this? My program is entirely based on For Loops and Sequence Structures. If you need a screen shot or want me to upload the program, please let me know. Fair warning, though: I am a LabVIEW novice so while the program functions correctly, it is not the prettiest in the world.

Thanks for any help you can provide.

Michael

P.S. I searched the forums and didn't find this question already posted. If, however, it was and I just missed it, could someone direct me to it? Thanks.

[ramses64]

Hi,
I think you should open the help menu, and search exemples of graphs : you will easily understant which graph is the best for your application.
Best regards,
Vincent

[Jon_S.]

Hello JM1619,

I think you can utilize indexing at the exit tunnel of your for loops.  If you right-click the exit tunnel of a for loop and select Enable Indexing you can build an array that has the same size as the number of iterations of the loop.   If you posted a screenshot of your code we could be more specific in what help we can give you.

[Andrew_E]

Hello,

I would take a look at the 3524 VI on this KB. I found it by searching NI.com for Graphing Multiple Plots. I think the Point Definition Graph would be suitable for what you were describing. If not, just provide a screenshot if thats possible. Thanks.

Message Edited by Andrew_E. on 02-23-2009 04:49 PM

[MJ1619]

Vincent, Jon, and Andrew,

Thank you for the advice. Andrew, I am taking a look at the link you provided. I hope that the solution to my problem may be found there. If not, I am working on a screenshot to post.

I really appreciate the help. The good news is that the control structure of the program functions as expected. Now I just need to display and save the data.

Regards,

Michael

[MJ1619]

Vincent, Jon, and Andrew:

I still need some help. I used the 3524.vi Example for the XY Graph: x-array, y-array definition to generate the kind of multiple plot xy graph that I needed. My problem now is I would like to re-index the plots so that they are labeled according to the Gate-Source voltage I am applying. Each curve has its own, distinct Gate-Source voltage and I would like to label each curve with its Gate-Source voltage. Currently, the plots are labeled in the legend: Plot 0, Plot 1, Plot 2, ... Plot n.

How should I go about doing this (is there even a way to do this)?

Again, any help would be greatly appreciated.

Michael

P.S. I have attached a copy of my program to this message. As I said, it isn't pretty, but it works so far. Hopefully this will help you in forming your suggestions.

[Jon_S.]

If you are looking to rename the plots you can use property nodes to do this.  Take a look at the attached pictures