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Isolated Analog Voltage Measurements

  1. Jun 2, 2014 #1
    Hello All,

    I'm working on a design for a board that will allow me to plug in a standard 10x scope probe and then reduce and isolate the signal to go into the input of an ADC in a microcontroller (0-5V range) with a max bandwidth of 100 kHz. I have been shopping around for a while looking at the different options available for isolation amplifiers and came across this one which seems to have everything I need: ACPL-C87A-000E. However, it comes in a tiny SMT package, and I'm looking for something that can be socketed in case of a failure during use. Avago seems to make many other osilation amplifierrs, but this is the only one I found that seems to be specifically suited for voltage measurements. Has anyone here had any experience building circuits for analog signal isolation? I have looked at several other solutions out there but they either involve more parts or are far more expensive to implement.

    Jason O
  2. jcsd
  3. Jun 2, 2014 #2


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    Integrated circuits are inherently made to reduce the complexity of the PCB by cramming a lot of parts onto a small package. So, the isolation amplifier you wish to use but has the drawback of being SMT is the starting point and from there the you will increase the number of parts and complexity of the PCB. Having worked for a test equipment manufacturer I can tell you that generally we used an A/D convertor and then an opto-coupler for the isolation before going into the microcontroller. I would assume that you have investigated that route.
  4. Jun 2, 2014 #3
    Hi Averagesupernova,

    Thank you for the input. Yes, I have looked into this. Actually, the probe board is designed to be an addon for microcontrollers that take an analog input (using their internal A/Ds). If the input were to be digital, then I could definitely put the A/D directly on the isolated side and clock the digital output over a digital isolator. the challenge is that I need an analog output and, ideally, want to find an integrated solution.

    - Jason O
  5. Jun 2, 2014 #4

    jim hardy

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    Have you tried a search on "Surfboard" ?

    that's a brand of circuit boards that accept surface mount but have a larger footprint and pins for a more convenient package.


    at digikey or hobby sites...
  6. Jun 2, 2014 #5


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  7. Jun 3, 2014 #6
    I put "ACPL" into a Digikey search and then filtered for "through-hole" parts to come up with these 8-DIP isolation amps. Would any of those suit your needs?

    It's well worth becoming familiar with Digikey's online catalog. It has interesting filtering options like "through-hole" for example.
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