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Buffered High Speed ADC for embedded oscilloscope

Discussion in 'General Electronics Discussion' started by MBrantley, Jan 21, 2015.

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  1. MBrantley

    MBrantley

    8
    0
    Jan 21, 2015
    Hello,

    I am working on a project that involves applying an RF (6-14MHz) sine wave and our project design goal was to have an oscilloscope embedded in the device to monitor signal intensity and integrity. Our signal is a pulsed RF that we are interested in knowing the Vpp and basic visualization of the sine wave for visual inspection.

    Initially I purchased a Bitscope Micro (BS05) but based on the feedback from the company, their super sampling techniques don't quiet extend to the higher end of their advertised bandwidth (20MHz). Now I am trying to find a new approach and wanted to discuss an idea with some more experienced people (I am a chemist, not an EE).

    Because our signal is 6-14MHz I suspect we need a sampling rate of atleast 200MSps. I'm not finding any off the shelf USB oscilloscopes that have that capture speed (and fit in our control module) - I suspect due to limitations in USB transfer rates? If you know of a prepackaged solution that could integrated with a Raspberry Pi or comparable device please let me know.

    The idea I would like to discuss is the ability to take a high speed ADC, use that to write to some embedded memory (this would be the capture window at at least 200MHz) at a set frequency (maybe capture the full window 1000x per second or so) and then push those captures through USB or I2C to the micro controller. I understand this would be absolutely useless for non-continuous signals as no information would be stored in between full window captures - but it would fit the design goals of displaying the sine wave to the user and monitoring frequency/Vpp. I feel like there are probably already ways to do this - but I haven't been able to locate them yet.

    Do devices like this exist already? Is there possibly a simpler way to approach this? I have no experience with FPGA but I'm confident I could learn them if needed. What about the PCUs on a Beaglebone black?

    Any insight or discussion is appreciated!

    -MB
     
  2. BobK

    BobK

    7,682
    1,688
    Jan 5, 2010
    There are fast buffered ADC chips out there that would do what you need (at least the capture portion of it). I don't remember who makes them, but if you search at Mouser or DIgi-key, I am sure you can find one.

    Bob
     
  3. hevans1944

    hevans1944 Hop - AC8NS

    4,626
    2,159
    Jun 21, 2012
    Fast sampling oscilloscopes with deep memory are pricey. For a USB device, check out this manufacturer. Not cheap, but less costly than a comparable bench 'scope from Tektronix, Agilent, or Rohde & Schwarz. USB bandwidth is not generally a consideration. Accquisition occurs in the box and results are sent via USB for display on an attached computer. Not even close to being real-time, but usually adequate for most purposes.
     
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