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Accellerometer Interface

Discussion in 'Electronic Projects Design/Ideas/Reviews' started by NeilFord, Sep 4, 2003.

  1. NeilFord

    NeilFord New Member

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    Does anyone have a simple circuit diagram for a constant current signal conditioner. I want to interface an ICP type accelerometer with an oscilloscope.
     
  2. stevez

    stevez Active Member

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    A constant current source can be made from an LM317 - see National's datasheet for more info. I do not know if the available range suits your needs but it is simple and low cost.

    Not sure what other conditioning you need but filtering might be useful if you want to eliminate some noise or unwanted information - all depends on what you are doing. I cannot tell you what impact the use of the LM317 has - some characteristics are frequency dependent however I do not know to what degree these play out in the current regulator configuration.

    I recall pulling some good "signal conditioning" application guidelines from TI or a similar website. Applications info for the sensor you've selected may address that.
     
  3. Roff

    Roff Well-Known Member

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    From what I could gather by searching for "ICP accelerometer", I think you need a voltage-controlled current source with bipolar capabilities. Do a Google search on "howland current". One example is here.
    If you need more details, I'll help as time allows.
     
  4. dave

    Dave New Member

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  5. mechie

    mechie New Member

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    Simple Accelerometer driver

    How does this look...
    a simple constant current supply based on a BC109 or similar.
    C1 is the DC blocking cap - maybe 0.22uF is enough to drive a hi-Z 'scope.
    C2 is just to help reduce Johnson noise.

    Theory and calculations are shown at http://www.electro-tech-online.com/threads/id-like-to-actually-know-what-im-doing.2644/
     

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    Last edited by a moderator: Dec 26, 2013
  6. Roff

    Roff Well-Known Member

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    Mechie, I think you're correct, except it appears that you may need to use a PNP current source (or a constant current diode). the attached figure is Fig. 7 in this document. Apparently the source follower which is integral to the transducer is P channel.
     

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  7. dgallagher

    dgallagher New Member

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  8. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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  9. JimB

    JimB Super Moderator Most Helpful Member

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    It is quite noticable that many people joining the board resurrect long dead topics, often as in this case, started by someone who has never returned.

    JimB
     

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