How to stop a continuous acquisition in Producer/Consumer

[liubingxy]

Hi,

I try to use Producer/Consumer to control "Start" and "Stop" of my continuous data acquisition system. I can successfully start the acquisition process, but I cannot stop it by "Stop" botton.

I have attached my simplified VI. Can anybody help to have a look at it and tell me what is wrong there? 

Thanks,

Bing

[P@Anand]

Please post the vi in 2009 version.

[liubingxy]

Hi Anand,

Thanks for response. I've just made a 2009 version, please check!

Bing

[P@Anand]

You have kept the dequeue outside the loop that means your consumer will run once in an execution and runs the same input what it got at the start. Keep the dequeue inside the while loop.

[crossrulz]

Your Dequeue needs to be inside of the loop in order to read it constantly.  You should also set the timeout for the Dequeue to the 200ms and handle the timeout somehow.

Based purely on what I see in this example, a Notifier would probably be a better tool for you.

[liubingxy]

But in this way, when hit "start", it acquires only one point and wait for me to hit it again to acquire another point. I need the acquisition running continuously and stop only when I hit "Stop". Do you know how to implement this?

[crossrulz · Accepted solution]

As I said before, use a notifier and handle the timeout.  I used a select with the Timeout? boolean.  If a timeout happened, use the previous value.  If we got a notification, use that value.

[liubingxy]

Thank you! I will try this one. 

[liubingxy]

Great! It works. It is exactly what I am looking for! thanks again!

[liubingxy]

Hi crossrulz,

Followed your way, I intergrated the Notifier scheme into my LabVIEW codes, but got a problem.

Because I finally need to store my data into a file, I have to output the data outside the while loop. When I do this, the "empty False case" gives a lot of zeros, before I hit start to acquire the real data. Do you know how to deal with this "empty False case", to not acquire those default zeros?

please check my VI

thank you

Bing