Saving data from graph/chart to use next time a VI is run

[Charel]

Hi all!
I am not sure if this is even possible, or whether someone has maybe done something like this. I need to save the data from a graph or chart during each run of a VI. I then want to call this data back into the Vi the next time it is run so it can be displayed at the same time that the VI runs. I need to do this in order to compare measurements from different setups during each measurement. This way I will have a reference to be able to observe what influences different changes in the system has had in comparison to a previous test.

Any suggestions will be greatly appreciated!

Thanks for the help!

Charel Marais

[tst]

There are a few points to this.

First, you need to decide whether you want to save the data or just hold it in memory. Saving it to the hard drive will be more complex, depending on the format of your data, but you can search for "file" in the example finder (Help>>Find Examples) and look at the VIs in the file I\O palette.

If you simply want to hold the data in memory until the next time the VI is run, you can simply use a local variable or a shift register. You can search the example finder for "shift register" for some examples.

The key to what you want is using multiple plots on your graph\chart. When you do, you can take the data from your last run and simply insert it into the graph as an extra plot, which will be visible at the same time as your new data. Again, search the example finder, this time for "graph" or "chart" to see how to work with multiple plots.

To learn more about LabVIEW, I suggest you try searching this site and google for LabVIEW tutorials. Here and here are a couple you can start with. You can also contact your local NI office and join one of their courses.
In addition, I suggest you read the LabVIEW style guide and the LabVIEW user manual (Help>>Search the LabVIEW Bookshelf).