Need to know maximium number of samples per second

[AlanR]

I'm using labwiew 7.1, I'm new to labview. I'm looking to write a program that takes a large number of samples from 3 different channels on a 6220 DAQmx card which I can then use to plot several graphs after applying two formulas to two of the channels (these need to be calculated in parallel) and none to the third. I need to take about 1500-2000 samples per second per channel and the graphs drawn will need to be realtime, or realtime as far as the human eye is concerned anyway. I need to know, 1. If the card can take this many samples per second, and 2. even if it can, will labview be able to use this many samples quickly enough and perform the calculations nessesary for near realtime refreshing of the graphs. I can't seem to find specifications, e.g. maximium sampling rates etc. anywhere for either the card or labview.

[devchander]

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I need to know, 1. If the card can take this many samples per second, and 2. even if it can, will labview be able to use this many samples quickly enough and perform the calculations nessesary for near realtime refreshing of the graphs.

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Answer for both queries in one word: Yes

Here are the specs of the card

[AlanR]

Thank you, just wanted to make sure before I started writing.

[SachaE]

Hi,

  just to clarify that, as long as you work in chunks of data you should be fine. Point by point, you may struggle.

Since you've indicated you're using graphs, and not charts, then I'm assuming you're working in chunks, i.e.

if your acquisition rate in hardware is 2000S/s, and you work in 200 sample chunks, then that's 10 updates per second to the screen - something which shouldn't be too arduous, but will depend on your CPU availability for the math, and your graphics card throughput for updating the screen.

You may consider splitting the architecture of your code to work in an acquisition loop and a handler for the data loop (a classic producer consumer setup) so you can tweak the timing as necessary. In LabVIEW, have a look at the New... and then select Frameworks and then you should see a couple of producer/consumer ones. You can probably use notifiers if you're going fast enough, or if you find you glitch on the timing every so often, then use queues so you can play catch up with the display etc.

Hope that helps

Thanks

Sacha Emery
National Instruments (UK)