Saving multiple signals to ASCII file

[Zamikki]

How can I save two (or more) signals from different sources to same ASCII file? I want to be able to compare the wanted and the actual measured signal by looking the ASCII file result...

The result file (sweep.txt) could look like this:

DC Signal  mean

1                 0.99

2                 2.1

3                 3.0

 My little sequence looks like this 🙂

Sweep (from 0V to 5V, 0.5 steps)

  Create analog signal

   |> DC signal

  DAQmxGenerate

  >| DC Signal

  DAQmx Acquire (10 samples)

  |> Voltage

  Statistics

  >| Voltage

  |> mean

  Save to ASCII/LVM

  >| mean

  >| DC Signal (I can't seem to add another source like this!!!)

End sweep

The way the Save step acts when trying to add another signal is rather...chaotic! You can TRY to add another signal but you can't select it, OR if you can select it it will cause an error later on...(Missing input)

And if I choose to export DC Signal and mean from the sweep output and then save it...The header talkes about "Frequency (Hz)" which is not related to the measurement at all...so it seems there are bugs in the software or my reasoning...And I can't seem to change the header either!

Shouldn't it be possible to save lots of different measurement data from different devices?!?! It seems like a normal thing to do!!

...My next sequence was supposed to measure the effiency of a regulator by sweeping the input voltage Uin (100 points) and the load resistance Rload (100 points ) and save the results in a file looking like this: (total of about 100x100 measurements)

Uin Iin Pin Uout Iout Rload Pload n

Oh and BTW i'm using Signal Express 2.5.0, is there an update availlable?

Thanks...

-Sami

[AdamE]

I can think of a couple of issues that may be causing your frustrations. 

Issue 1:

The DC signal coming from the Create Signal step is actually a waveform with multiple samples, not just a single value.  The mean value is a double with one value.  The Save to ASCII/LVM step is not set up to save inputs of different types to the same file.  Since they can have different lengths, putting them side-by-side into the same file doesn't make sense. 

Try doing just a save of the DC signal and then another of the mean value and then take a look at the output data and you'll see the difference.

Issue 2:

When you have outputs of a Sweep, the outputs are functions of the selections made in the Sweep Output tab.  This allows the values of signals vs. the swept parameter, so you may have the DC signal swept against the frequency changes in the Sweep step.  Check the Sweep Output tab to verify you're sending out the data you want.

Adam.