Delta_X available in LVM headers ?

[asquit]

Folks -

I'm trying to use NI-SCOPE with a USB5132  .Want to save .lvm files with one x-axis column with  values computed from xIncrement, and have been trying to use the "Write to Measurement File" express vi. The header shows Delta_X = 1.0 . Is Delta_X itself available, do I need to make a better dynamic data array (tips would be appreciated) , or do I give up on the express vi and use old style"save to text", building up each line ? is the example "niScope EX save to file - hws low level-MultiChannel.vi" the right one ? seems like kind of the log way ' round.

Here's my vi. Or how to convert the waveform I'm sending to the plot into the right dynamic data ?

thanks

Alex

[DFGray · Accepted solution]

Internally, the dynamic data type (DDT) is an array of waveform datatypes (WDT).  When you convert something else to a DDT, it is coerced to an array of WDTs.  In your case, this is natural, since you have a 2D array of data.  The Express VI uses the dt value from the WDT in the DDT to write the Delta_X value in the header.  If there is no dt (and there is not in your case, since it is converted from a 2D array of doubles), a 1 is used as a default.  The easiest way to fix this is to fetch your data as a 1D array of waveform datatypes.  Just right-click on your fetch VI, choose Select Type->Multi Waveform->1D Waveform Data Type.  You will also need to change your converter so it has a 1D Waveform input.  You can wire the 1D array of WDTs directly into your graph.  You probably want to go to the graph properties (right-click, last item), the Scales tab, and uncheck Ignore waveform time stamp on x-axes so that your t0 is used.  Unfortunately, this will set the scale format properties so that absolute time is displayed.  You probably do not want that either.  Go to the Display Format tab and change to whatever you want (I usually use SI notation with 6 significant digits and Hide trailing zeros).

Good luck.

[asquit]

Thanks ! Done ! woo hoo !