Build Waveform using waveform datatype

[millepede]

Hi,

I am using LV8 to acquire data from my tektronics TDS 3014B oscilloscope. I haven't built my own VI but am using the example program that came with the labview drivers. I don't know how to attach a vi to this post but I will try my best to describe my problem verbally.
The vi acquires wavefrom through another subvi which outputs the y axis waveform data (array of doubles), starting time (double) and time increment (double). Then these three things are input into a bundle. The output of this bundle is a cluster of 3 elements. This is input into a waveform graph which magically generates the entire waveform from this cluster. Now I want to do 1) FFT power spectral density on this wavform data 2) write the waveform data to file. The FFT vi takes time data as input and the file I/O vi takes dynamic data as input. So there is a data type mismatch when I connect the output of the bundle to the input of these vi's

I tried using the build waveform vi. But it requires a time stamp data type for the t0 input, while the starting time I get from the data acquisition is a double. So there is a data type mismatch error. How do I go about building my own waveform or use the above cluster to do the time data and the dynamic data.

Thanks in advance.

-Anand

PS - I wish LV did away with data types altogether like python

[smercurio_fc]

You're basically missing the To Time Stamp function, in the Timing palette, e.g. :

The output of that function is a "time-zone-independent number of seconds that have elapsed since 12:00 a.m., Friday, January 1, 1904, Universal Time" (from the LabVIEW Help).

P.S. There's a section right below the message entry where you can attach items. There's a textbox where you enter the path to the file you want to attach. When you submit the post the attachment gets uploaded.

P.P.S.

"PS - I wish LV did away with data types altogether like python"

Now why would we want to do that? Then it would be like programming VBScript.

Message Edited by smercurio_fc on 05-08-2008 04:27 PM

[millepede]

Thanks a lot for the post. I will try it out. I can also see the attachment thing now (God, how blind am I?). Just another question. Could you explain what the bundle does and how it generates the waveform from the cluster. That is the most awesome LV feature (magic?) I have discovered till date and would like to understand it a bit better.

Thanks a lot.

-Anand

[smercurio_fc]

The Bundle function isn't really doing anything other than creating a cluster of 3 elements. That's just a generic operation. The "magic" is coming from the waveform graph itself, which interprets each element and generates the picture and axes.

[millepede]

Thanks a lot. I have it figured out now. However, I am having a big problem with the data acquisition now. Whenever I do the data acquisition I get the following error message.

TKTDS3K Error Query;
Instrument reports the following:
410:  Query INTERRUPTED;
0:  No events to report - queue empty

It seems that there is some interrupt to the oscilloscope after every 600 ms or so. This means that if I have a slowly varying signal, the data acquisition doesn't finish. I am trying to monitor signals with a repitition rate of 1 Hz. So this is a big problem for me. Any ideas as to what is going on?

Thanks again for all the help


Message Edited by millepede on 05-08-2008 07:05 PM

[smercurio_fc]

That sounds like the LabVIEW program stopped reading the data from the scope. However, that's just a guess without actually seeing the code. Which drivers did you download, and which VI are you actually using?