Multifunction DAQ

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Need continuous acquisition of 16 channels through SCXI-1125 to PCMCIA DA board + FFT on all channels. Can it be done?

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Where's the limit? Assume a new Dell Latitude running NT with 128 MB RAM and a fast P3. Equip it with the DAQCard-AI-16E-4 connected to an SCXI chassis with 2 SCXI-1125 modules.

How fast can I run the sample rate (per channel) if I want to do continuous DAQ on all 16 channels while computing the power spectrum of all channels once per second (using one second's worth of samples)?

The DAQCard has a tiny FIFO, and I'm hoping to use pretriggered scans so I don't have to wait for data. Is that an option without the DMA functionality of the PCI E-Series boards? Without it I will have to constantly empty the FIFO into a "software" b
uffer which will cost boku (many) processor cycles, correct?

So what say the experts... how fast can this thing run? How about if I ditch the laptop and go PXI with the whole deal? Lets make the case!

Thank you!
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I believe the PCMCIA interface is going to be the limiting factor in this case. The maximum continuous rate for a DAQCard will vary from computer to computer, but it isn't extremely fast.

Being optimistic, let's estimate 64 K samples/second. I don't know if this is high or low nowadays, but it is higher than I could ever achieve a couple of years ago. Divide that by your 16 channels, and you have 4K blocks. I think you could process this in 1 second easily. This gives you 1 Hz resolution up to 2 Khz.

Now, if you ditch the laptop and go to PXI, it is a whole different story. DAQ rates will not be the limiting factor. You just need to find out how large of a block you can process and keep up.

My approach to this problem would be to figure out what analysi
s you need, then figure out what hardware can accomplish it. Do you really need 1 Hz resolution? Do you need to process every bit of data that comes in? Are you going to store the results, or just display them on the screen? Can you do post-processing of the data if necessary?

Bruce
Bruce Ammons
Ammons Engineering
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