AutoMeasure Posted October 25, 2008 Report Share Posted October 25, 2008 I need to continuously sample one analog voltage at 1.25 megasamples/second, 16 bits. I'm considering the NI PCI-6251 card in a desktop computer vs. a USB-6251 BNC with a notebook computer. My question is, are there any issues with the USB version keeping up with continuous sampling and data moving at that rate robustly? And are there any issues or problems at all with using the USB product instead of the PCI card product? Thank you very much for your advice on this! Quote Link to comment
RobertJCornwell Posted October 27, 2008 Report Share Posted October 27, 2008 QUOTE (AutoMeasure @ Oct 23 2008, 09:16 PM) I need to continuously sample one analog voltage at 1.25 megasamples/second, 16 bits. I'm considering the NI PCI-6251 card in a desktop computer vs. a USB-6251 BNC with a notebook computer. My question is, are there any issues with the USB version keeping up with continuous sampling and data moving at that rate robustly? And are there any issues or problems at all with using the USB product instead of the PCI card product?Thank you very much for your advice on this! NI states that "high-speed USB M Series devices deliver bidirectional streaming at up to 1.25 MS/s for analog input" (see http://zone.ni.com/devzone/cda/tut/p/id/4473#toc2). Also, this article (http://zone.ni.com/devzone/cda/tut/p/id/3705) indicates that the USB signal streaming technology used in the USB-6251 should be able to stream data over USB at up to 3.2MS/s so the speed of the USB-6251 doesn't appear to be limited by the USB interface. Quote Link to comment
Neville D Posted October 28, 2008 Report Share Posted October 28, 2008 True, the specs seem to point out that the device should work fine in terms of speed, but I've heard from others that sometimes in long term tests, MAX or the software appears to "lose track" of the device somehow, and the only way to bring it back is to unplug and replug the device back. Just to be safe, I would use a PCI device for a neater solution (no external power brick required). N. Quote Link to comment
Peter Leung Posted January 30, 2009 Report Share Posted January 30, 2009 One key difference, you cannot use the USB DAQ's clock as the Timing Source for a Timed Structure. Read 'LabVIEW Help', topic, 'Selecting a Timing Source for a Timed Structure', section 'External Timing Sources'. Quote Link to comment
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