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Question about piezo crystals

  1. Feb 2, 2016 #1
    I think I understand the basics of piezo crystals. You apply pressure and the crystal produces a voltage. Conversely, you apply a voltage across the crystal and it deforms.

    My question is this: if you were to apply pressure to only a small region of the crystal (if that's possible?), would the voltage be produced only across that region, or would it spread throughout the crystal? What I'm getting at is the idea of hooking up a number of leads to to the surface of a crystal and getting distinct voltage measurements from different physical regions of the object. Is this a thing that happens?

    Thanks.
     
  2. jcsd
  3. Feb 3, 2016 #2

    Daz

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    I guess so. This is used the other way around (apply voltage and get movement) to make some neat little piezo actuators. Google "segmented piezo actuator."
     
  4. Feb 3, 2016 #3
    Thanks, I just ran a search. I can't tell if "segmented actuator" means they have a number of distinct crystal plates somehow formed into a "segmented" array, or if they are literally taking a single crystal plate and extracting from it information about localized stress/strain. The latter is what I was thinking of. Do you know of any examples of that being successful?
     
  5. Feb 3, 2016 #4

    dlgoff

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    This page may be useful. http://www.piezo.com/tech2intropiezotrans.html
     
  6. Feb 4, 2016 #5

    Daz

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    What I have seen consists of a single tubular piezo element with multiple segmented electrodes around the outside. This design was first demonstrated by Binning and Smith in 1986 (Rev. Sci. Instrum. 57(8), p. 1688, 1986.) I don't know if that's how the commercial ones work but I expect at least some do.

    In any event, some enterprising amateurs have even made their own from cheap piezo buzzers. Here's a fascinating little project by someone who made his own STM (scanning tunnelling microscope) using parts from hobby electronics stores.

    http://dberard.com/home-built-stm/scan-head/

    Check out the fourth photo.
     
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