Introducing LabVIEW 2009

[RavensFan]

Go to Thread Options menu drop down at the top of this screen above the messages.  Pick unsubscribe from this thread.

I dont' blame you, with the endless rants, this thread is already at least twice as long as it should be.

[hecmar.arreola]

Nevermind all the ranting about the ranters...

[kmcdevitt]

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Ravens Fan wrote: 

Go to Thread Options menu drop down at the top of this screen above the messages.  Pick unsubscribe from this thread.

I dont' blame you, with the endless rants, this thread is already at least twice as long as it should be.

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Nickerbocker wrote:
Nevermind all the ranting about the ranters...

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Yes Ravens Fan and Nickerbocker,

It would have been nice to have kept the ranting to simply all the nice features introduced in LabVIEW 2009.

Shame NI had decided to not honor the SSP and give us what we have paid for and are entitled to.

Anyway, I think its just best not to mention the whole MathScript and ranting thing, lest we start it all up again.

Kevin.  

[RavensFan]

I opened a VI today in LV 2009 that had a feedback node in it.  It looks completely different than the previous versions of the feedback node.  It had more options that could be set with it and mentioned something about a Z transform delay.  What is that supposed to mean?

I'll have to look in the help file to see if it adequately explains this new version of the feedback node.  I was surprised I hadn't seen any mention of a change on this before.  It is buried very deep in the New in 2009 file in the startup screen.

Perhaps someone who understands these configuration options and what a Z transform delay is, can write up a nugget explaining all of this.

I had just started using feedback nodes instead of uninitialized shift registers in action engines.  Now that the feedback node has changed in 2009, I am kind of scared to continue using them.

Message Edited by Ravens Fan on 08-27-2009 12:26 AM

[Darin.K]

Preface by saying I don't have LV2009, but I know that in signal processing that the Z-transform of a delayed sequence y(n) = x(n-m) is Y(z) = z^(-m)X(z), so for a simple delay of m=1, you get Y(z) = z^(-1)X(z), hence the z^(-1).  Looks purely aesthetic to me, if there is more to it I look forward to the nugget.  BTW that is exponentiation, not bit-shifting.

[dan_u]

For those familiar with discrete signal processing the z^-1 just makes it more obvious that the output of that node corresponds to the value passed in at the last iteration (time shift of 1 cycle).

So I agree with Darin that this looks mostly like an aesthetic change.

Don't be scared 

Daniel

[RavensFan]

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dan_u wrote:

For those familiar with discrete signal processing the z^-1 just makes it more obvious that the output of that node corresponds to the value passed in at the last iteration (time shift of 1 cycle).

So I agree with Darin that this looks mostly like an aesthetic change.

Don't be scared 

Daniel

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Actually, I think the previous feedback node was better looking.

There are a few configuration options there that could be discussed.

1.  It looks like you can set the feedback so it doesn't take the previous iteration, but some programmer defined number of iterations back (2, 10, 1000?).  What would be an example of a practical use case for that?

2.  It has an enable input on it.  How does that function?  How does the feedback node behave if it is disabled?

3.  It has different modes of global initialization.  What are the practical differences between them?

The help file doesn't explain much on these.  When I went to detailed help from the context help window of the feedback node, the help screen didn't give a very good explanation.

[Ben]

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Ravens Fan wrote:

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dan_u wrote:

For those familiar with discrete signal processing the z^-1 just makes it more obvious that the output of that node corresponds to the value passed in at the last iteration (time shift of 1 cycle).

So I agree with Darin that this looks mostly like an aesthetic change.

Don't be scared 

Daniel

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Actually, I think the previous feedback node was better looking.

There are a few configuration options there that could be discussed.

1.  It looks like you can set the feedback so it doesn't take the previous iteration, but some programmer defined number of iterations back (2, 10, 1000?).  What would be an example of a practical use case for that?

...

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A moving average?

Say you want to averge the las t20 readings, the value that bubbles out of that terminal would be subtratced from the running total and the new value added in.

Ben

[dan_u]

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Ravens Fan wrote:

Actually, I think the previous feedback node was better looking.

There are a few configuration options there that could be discussed.

1.  It looks like you can set the feedback so it doesn't take the previous iteration, but some programmer defined number of iterations back (2, 10, 1000?).  What would be an example of a practical use case for that?

2.  It has an enable input on it.  How does that function?  How does the feedback node behave if it is disabled?

3.  It has different modes of global initialization.  What are the practical differences between them?

The help file doesn't explain much on these.  When I went to detailed help from the context help window of the feedback node, the help screen didn't give a very good explanation.

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I'm still working on 8.5 so I can't look at it and I can't comment on your Q2 & 3.

1. This was possible before with shift registers (just expand them), but afaik not with feedback nodes.

It can be useful for filters (even though you usually need several previous values) or for instance in simulation, to simulate a delay of 4 cycles use a z^-4.

Daniel

[Ben]

I'm trying to learn the new icon editor. I suspect it is based on some software that I have never touched (it sure ain't paint) so it is taking me some time to learn. Drawing a line with the right-mouse button (for the background color) is no easy feat when you are left-handed.

But I have a question!

What is this button supposed to do and how do I use it?

 

Curious,

Ben