How to create a real-time graph in LabVIEW 6.1?

[Chefbo]

I'm new in programming in LabVIEW(6.1). I was ask to create a interface in LabVIEW that can operate the DMM Keithley 6487 that allow us to apply a voltage and take certain nth measurements. With the measurements we create a graph(I-V Curve) i find the XY graph but it only allows to send all the measurements at once (indexing) to generate the graph and not each time that we take the measurement so the graph be generate inn real-time. I need to know how can i create a graph or edit the XY graph so i can generate the I-V Curve with every measurement that we take in real-time. Every time we take the measurement and not once the program ends. thanks in advance.

[smercurio_fc · Accepted solution]

You would need to place the graph inside the loop and use shift registers to accumulate the X and Y as arrays. I don't have 6.1 running right now, but it would basically look something like this:

 

Note that the above is for demonstration (code is actually a Greedy Loop). You may want to consider putting the writing to file inside the loop. This way, if the program crashes you won't lose your data.

Warning: Using Build Array as shown above will cause continuous memory growth. If your program will be running for a long time this may become an issue. One thing you may need to look at is to have a limit on the size of the array. I know there's an "XY Chart" example that ships with LabVIEW, and I'm pretty sure it was there with 6.1. You should take a look at that example, as it implements a fixed buffer size for the chart data. You should be able to use the "XY Chart Buffer" VI directly in your code.

Message Edited by smercurio_fc on 03-30-2010 09:16 AM