topic Re: Waveform disappearing in Multifunction DAQ

Waveform disappearing

HossIsAlright — Wed, 20 Feb 2008 10:35:38 GMT

Hi.

I'm samling the signal showed in the JPEG-file below, and the problem is that the waveform (which is continously updated in LabView)
sometimes disappears. The waveform chart simply returns a blank chart. Anyone knows what to do?

Børild

Re: Waveform disappearing

GovBob — Mon, 25 Feb 2008 02:17:26 GMT

I think we all need some more information to help you (i.e. what kind of hardware, which version of LabView, etc.). It would really help if you included the vi or a screenshot of the trouble area.

Re: Waveform disappearing

HossIsAlright — Mon, 25 Feb 2008 07:21:26 GMT

Hi.

I'm using an USB-6229 from National Instruments and LabView 8.5. For the screenshot, I've included it as an JPEG-file in my first post.

Let me know if you need some more info, thanks.

Børild

Message Edited by HossIsAlright on 02-25-2008 01:21 AM

Re: Waveform disappearing

HossIsAlright — Mon, 25 Feb 2008 09:31:35 GMT

I'm not able to attach the VI, cause the file is to big. Do you have an e-mail I could send it to?

Børild

Re: Waveform disappearing

GovBob — Tue, 26 Feb 2008 00:38:44 GMT

Borild

I don't work for NI so I don't want to post my email address on a public forum. I don't have your hardware. One thing you could post is a screenshot of the block diagram of the vi in question. If the diagram is too big focus it on where you write to the chart. Have you tried running the vi in highlight execution mode (the lightbulb)? Do you ever use a property node to clear the chart? Are you using a waveform chart or a intensity chart? By "blank" do you mean the chart is black? Have you looked into your scaling to make sure you are viewing the correct portion of the chart?

Just some ideas. Hope they help.

Re: Waveform disappearing

HossIsAlright — Tue, 26 Feb 2008 08:03:09 GMT

Hi!

Here's the screenshot of the area in the VI where I write to the chart. I haven't run the VI in highlight execution mode,
and I haven't used a property node. Do you think that will help? I'm using a waveform chart, and by blank I mean black.
I have also scaled the waveform chart so that I look at the portion I want.

Thanks for your ideas 🙂

Re: Waveform disappearing

GovBob — Tue, 26 Feb 2008 22:27:18 GMT

You don't need to use a property node. I was just asking if you did because sometimes they are used to clear the chart. I would try to run it in highlight execution mode as it might show you where you might be writing incorrect data to the chart. I see you make use of local variables. If at all possible try to use wires in there place to prevent race conditions (which might be happening in this case). In fact I think you can branch from the upper 'enveloped sine wave' variable to the lower express vi where it wants it as an input. In the section you show you really don't need the last sequence frame as your use of error in and error out terminal connections will enforce correct data flow between the express vi's. Hopefully someone from NI will help you with this post as well.

Hope this helps.

Re: Waveform disappearing

HossIsAlright — Wed, 27 Feb 2008 12:22:09 GMT

I will try, and let you know 🙂

Thanks a lot for your help!

Re: Waveform disappearing

HossIsAlright — Mon, 03 Mar 2008 08:31:49 GMT

Hi!

I've tried to replace tha local variables with wires, but

the waveform continues to disappear. It seems like it

helps to reduce the size of the graph window though.

When I reduce it, the waveform still disappeares, but it

doesn't do it as often.

Børild