Read from measurement file express VI changed my waveform X-scale name

[David_Jiang]

Hi, I am working on a project using write to measurement file express VI to save captured waveforms using NI DAQ, and then use read from measurement file express VI to read it out and display is on the same waveform window. (see attached my simplied VI). To run it, first click the "write to file" button, then click the "read from file" button. Here's the problem: when I click the read from file button, my waveform X-scale name changed to "time"! How can I keep my X-scale name not been changed? Thanks.

[Cory_K]

You have not specified a heading for your data, so it assumes it is time.

If you open the LVM file, you will notice it says "X_Value Untitled"

[David_Jiang]

Thanks, Cory. Where can I specify a heading for my data? I opened the express VI, but can't find a place to type in heading.

[Cory_K]

To be honest, I dont generally use the Express VI's.

To accompish what you want, I generally do the following:

Use a 'write to spreadsheet file' function, and pass a 1D string array with the names of each column (outside of a loop).

Use 'write to spreadsheet file' inside a while loop, with 'append?' wired to True to write the data to that file.

Wire the file name from the first Write function to the second.

This way is easier in my opinion, and it allows you to just work with data arrays instead of waveforms.

[Chris_G. · Accepted solution]

Hello David_Jiang,

The behavior you are seeing is actually a property of the Waveform graph that you can turn off.  Just right-click on the waveform graph and select Ignore Attributes to place a check next to it, and the x-axis should keep your "Waveform X-Scale" as the scale name.