Exporting/Merging Waveform Data

Can I export the waveform data to other applications?

You can copy a plot as bitmap by making a waveform window the active window and typing Ctrl-C. Then, in an application that accepts bitmap pastes from the clipboard like Word or Paint, type Ctrl-V. Note that this also works for bitmaps of schematics. These images can also be exported as Windows metafiles(Menu command Tools=>Write to a .wmf file) which writes the image as vector graphics to a .wmf file that can be imported in various desktop publishing tools. When exporting a metafile of waveform data, you first go to Tools=>Control Panel=>Waveform=>Font and select Arial. The default, System, is highly legible on a CRT, but is a fixed font that does not scale correctly in metafiles.

OK, that works for bitmaps, but can I get the data itself to an application like Excel?

There is an export utility(Waveform Menu: File=>Export) that allows data to be exported to an ASCII file. There is also a 3^rd party free utility written by Helmut Sennewald. It is available from the independent users' group http://groups.yahoo.com/group/LTspice. This utility allows various forms of manipulation of the data including the ability to merge waveforms from different simulation runs.

Who is Helmut Sennewald?

The guy on the right:

Helmut Sennewald is also the moderator of the independent LTspice Users' Group.

But isn't there any way to export the waveform data to other applications without resorting to 3rd party software?

Yes. Make the waveform window the active window and use menu command File=>Export.

But I want the data in equally spaced timesteps. Is there anyway to do that?

Yes. Do the the FFT of the desired data. Before the FFT, the data is interpolated to equally spaced time steps. Now do the FFT on the FFT'ed data. That will recover the equally spaced time-step data and export that.

But if I do the FFT twice, won't I lose accuracy?

No. LTspcie's FFT algorithm is bit-accurate to double precision.

But what if I don't want the data interpolated to a number of FFT bins that is a power of 2?

Then enter the number of bins you want to use. LTspice uses a proprietary FFT algorithm that works for an arbitrary number of bins.

How is it possible that LTspice's FFT is bit-accurate to double precision and works for an arbitrary number of bins?

That is a trade secret.