Capturing a segment of a waveform. Once.

[Thomas Hunting]

Hello everyone.

This vi captures a certain number of pre samples and post samples from a waveform, when trigggered.

However, it continually overwrites these values when the next pre/post samples.

How can I change it so that it captures the pre and post samples only once, regardless of the trigger state.

Thanks guys.

[devchander]

Do you want your trigger to be 'active' for only one capture sequence and ignore all the threshold crossings that will occur in subsequent iterations?

[Thomas Hunting]

Hello.

Exactly. Basically I want the capture to act on one trigger only and then stop, regardless of any subsquent triggers.

Thanks 

[Thomas Hunting]

I am kinda lost on this one.

I would appreciate the assistance.

Regards

Tom

[jasonhill]

You could make a psuedo-state machine out of it.  I modified your code to include an extra boolean shift register.  It starts false and is set true only when a trigger is found.  By inserting an OR statement before the case structure, the shift regiseter forces the case structure to always be true.

I don't feel like I am explaining the changes all that well.  If you have any specific questions, let me know.

[Thomas Hunting]

Hello Jason.

Thanks for the reply.

I am having difficulty opening the file, I have V7.1.

So if a trigger is found the case is in one state, but then is immedaitely locked in the othe state.

Regards

Tom

[jasonhill]

Try this:

[Thomas Hunting]

It works Jason.

Thanks for the solution and the expalination.

All the best.

Regards Tom

[jasonhill]

I'm just doing it for the stars because almost everthing I know about LabView, I learned in this forum.  And I enjoy giving back.

[Thomas Hunting]

I forgot to give you the stars with all the excitement, sorry

Here you go!

All the best