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Max. frequency of acquiring data in PCI 6515


I'm using PCI 6515 digital inputs to acquire a 64K quadrature encoder pulses attached to a motor with maximum speed of 3000 RPM. The encoder has two options of resolutions/revolution (32K or 64K). At this rate, with 3000 rpm speed - or 0.02 revolution/sec - the encoder produce pulses at 2.73 MHz (if 32K resolution is selected) or 5.46 MHz (if 64K resolution is selected). I looked in the datasheet and user manual of PCI 6515 ( but I couldn't find whether PCI 6515 digital inputs can successfully acquire or detect the encoder pulses at this rate.

I really appreciate your help.


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Very doubtful, by my reading of the specifications.  The section labeled data transfers does not include DMA, only the much slower interrupts and programmed I/O.  The manual referenced change detection but nothing about a timing engine.


Even if you could capture the digital signals, you'd still have to decode it into position information in software.  It's much more practical to use a device with a counter that has built-in support for quadrature encoders.  It'll be able to handle those signal speeds, and it will do the decoding in hardware, giving you incremental position measurements directly.


NI's X-series multifunction boards would be a good place to start looking.



-Kevin P

CAUTION! New LabVIEW adopters -- it's too late for me, but you *can* save yourself. The new subscription policy for LabVIEW puts NI's hand in your wallet for the rest of your working life. Are you sure you're *that* dedicated to LabVIEW? (Summary of my reasons in this post, part of a voluminous thread of mostly complaints starting here).
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