Catch a signal that's out of sync on a scope.

[Throggdor]

Hello All,

Like the title suggests I'm trying to catch a signal on a scope when its out of sync.

The signals I have look like a bipolar sawtooth that gets cut off early. So it starts positive then starts to go down then switches about half way down to a negative peak then half way down back to positive... and so on.

I have two signals signal 0 (7.8V pk-pk) is the reference signal it is always the wave described above, signal 1 (~3.9V pk-pk) starts in sync then goes out of sync.

So my question is how can I catch the signal when it goes out of sync? Is there a special VI or something I can setup in labview so I can set it up to catch the signal? Any ideas are welcome.

Thanks in advance.

[NIquist]

Catch the signal???  You didn't even tell us what kind of scope you're using. 

[Throggdor]

Labview 2012 SP1

Scope: PXIe-5122

[johnsold]

Can you show us some data or screen images? Preferably two images: in sync and out of sync.

Lynn

[Throggdor]

Hello Lynn,

below are the screen shots of the waves. This is the wave when its out of sync.

This is the wave when its in sync.

I've been thinking of using a producer/consumer loop.

[johnsold]

I am not familiar with the scope module.

I notice that you are looking at AC coupled signals.  It is not clear from the image whether the trigger signal is also AC coupled. If the signal is a zero-based square wave and the trigger works on the original (not AC coupled) signal, the 162 mV trigger threshold may be close to the actual level of the signal. Try increasing the trigger to ~ 500-1000 mV.

Lynn

[Throggdor]

Hello Lynn,

The signal is DC coupled, and the waves themselves are bipolar. I can trigger off the waves fine, my problem is that I'm trying to monitor the signal and see if the signal falls out of sync. I have a set period of time where the signal needs to lose sync but the time within that period is always different. So I litterally have to catch the second wave when the phase changes. 

[Throggdor · Accepted solution]

All:

I figured it out I just set my scope to measure a fraction of the signal I'm looking for and put all of that into a while loop, so far I'ts worked beautifully. Thanks for everyone's help I really appreciate it. Attached you will find the VI I used to solve my problem.

[NIquist]

Nice.  I'm glad you got it figured out.  Sorry I wasn't much help but I've never used the NI-Scope stuff.  

Thanks for the follow up post.  Perhaps someone in the future with the same problem can benefit by your solution.