queue or local variable to pass between loops

[Fibo]

I have a question about... best practices I guess... I've been making data aquisition VIs with data logging, and I usually make two while loops, one loop collects all my data and displays plots of the data (this loop executes faster), and my other loop I just use to write my data out to a file every second (this is my slpwer loop) ok, here's my question... I've been basically using a local variable to pass all my data from my fast loop to my slower loop.  But when I look through LabVIEW material I don't see it done this way much (or at all) I usually see people using something called queue's to pass the data from one loop to another.  Do I need to switch to queues?

If the only problem is race conditions, I don't mind, because I'm logging my data only once per second, and my data acquisition loop is fast so if I get the data from the previous iteration and not right away when I call it, I don't mind (my data isn't changing that fast anyway)

thanks!

[Ben]

"Slow", "I don't care" lend me to believe you can get away with using locals to transfer the data, but it is not a "best practive" becuase when you bump up the speed and care about loosing data, that mechanism will start to fail.

The queue is the prefered approach.

Ben

[Guruthilak]

its like what you need in your car.. CRDI (QUEUE) or normal injection (locals)

Guru

[jyang72211]

Local Variable may seems to be easy to setup, but if you get into a habit of using it, it will hunt you.  Queue seems a bit involve to setup at time (relatively), but it is the definitely the preferred way.

Yik

[muks]

First is there really a necessity to use 2 while loops. If you can manage to do it in the same loop then it is the best.

Cause there is nothing better then transferring the data through a wire. After all we use labVIEW............

Message Edited by muks on 03-05-2010 03:13 PM

[nitad54448]

hi

i recently started to use the "action engine" (thanks to Ben for the great nugget !). So give it a try !

(if you have a version previous to 9, unfortunately there is a strange bug to the AE, when using waveforms in cluster, otherwise it is great ! it is my most used tool after the state machine !)

N

[Anna_K.]

An easy way to get started using the queue in your architecture is to start with a Producer/Consumer temaplate as well as running some of the queue examples.

In LabVIEW go to File >> New...

In the dialog box expand VI >> From Template >> Frameworks >> Designe Patterns and select Producer/Consumer Design Pattern (Data)

This will set you up to fill in your code in the slow (consumer) and fast (producer) loop.

Also, take a look at the Queue Basics.vi in the Example Finder.