How to make an acquired array of data work with point-by-point functions

[PatB30]

Hello everyone,

I am working on a LabVIEW project using the Measurement Computing PCI-DAS6402/16 board. I am attempting to use point-by-point analysis with data acquired from the board, but I am having some difficulty. I am currently only able to acquire an array of data and not just a single point of data per scan. So, I was wondering if i) anybody possibly had any knowledge/experience using this particular board and getting it to be compatable with point-by-point VIs or ii) if anybody possibly knows anyway to convert an array of acquired data to work with point-by-point VIs in a hard realtime application. Thanks

Pat

Message Edited by Support on 11-16-2005 07:56 AM

[becktho]

Hi Pat

I just can tell you how you can use the pt-by-pt functions. As you said you have an array of data. To use the pt-by-pt functions, you need the single datapoints. So the only way is to use a loop to get the single elements and pass them to the pt-by-pt functions.

I've attache a simple example.

If this is the right way for you concerning processor and memory load, execution speed etc. I can't tell you.

Hope this helps.

Thomas 

[PatB30]

Thanks for your reply and suggestion Thomas. I have been experimenting with LabVIEW today and noticed that the pt-by pt functions work with the time-stamped waveforms that are outputted from the simulated signal express VI. So, by turning my array into a time-stamped waveform, will I beable to use this created waveforms with point by point functions or is using the previously suggested method better? Thanks again for all your help.

Pat

[becktho]

Hi Pat

Could you post a screenshot of this solution?

[becktho]

Hi Pat

Does it really work with a waveform? This also confuses me - if you use the mentioned express vi you get a "dynamic data" type.

Just have a look at the vi attached. There must be a difference to your solution.

Thomas

[Andy F.]

Thomas,

I tested this as well, and it seems that when I pass either a dynamic data type (DDT) or waveform to the VI, I will always get the last value.  Is this what you are seeing?  The DDTs are usually the outputs of express VIs, but I tried both a signal generation VI and just converting the waveform to DDT, and I saw the same thing.  The point by point functions should be used with just points, as you have in your example.  I might recommend passing the size of the array to the function to get better results though. 

Hope this helps!

Andy F.

[PatB30]

Hi,

I did my own testing by passing a waveform through a regular filter and a pt-by-pt filter and got different answers. So, using waveforms with pt-by-pt VIs was a bad idea. Thanks again for all your help.

Pat

[becktho]

Hi Andy

Yes, this is exactly what I saw. Quiet strange - a function which usually accepts a single data-point works with waveforms and DDT.

Anyway - if one realises the difference - no problem.

Thomas