Limited number of samples on NI 4472 card

[MiamiVipul]

Hi:

I'm relatively new to Labview. I have a setup with rotating shaft and two displacement sensors feeding voltage signal into NI4472 card. I use an external trigger and collect data only when trigger takes place. When the trigger takes place (impact-type force), I need to collect as many data points as possible. I also need to write these data points to a file. I have gone through number of examples and put together a VI (and a sub-VI) to collect data.

My problem is:

I cannot go over 1000 samples! No matter how I combine T (sampling time), Fs (Rate), or N (sample size) (where N=T * Fs), I come to a limit of 1000 data points. In my VI, I can set the N, but it does not go over 1000. If I enter a vakue greater than 1000, it will adjust T so that the sample size is still 1000. 

Is there any limitation on my DSA card? I'm not much familier with many of the terms that you experts use, but could you please take a look at my VIs and kindly let me know whether I can setup the VIs to get larger samples?

Thanks a lot.

Vipul. 

Message Edited by MiamiVipul on 04-07-2006 11:03 AM

[Berto]

Hi Vipul,

If you check out the 4472 Specifications at http://www.ni.com/pdf/manuals/373861c.pdf  you'll see that the FIFO buffer is 1,023 samples, so this makes a bit of sense.

What I'm seeing that might be hurting your application is that your Write LVM Express VI is set to Replace the file each time it gets run -- so every time your While loop iterates, you're going to replace your old data.

I'd try changing that to Append mode, and see if you are getting everything you want.  It should run 1000 samples at a time.

Good luck!
mike