Ultrasonic Mapping

Discussion in 'The Projects Forum' started by samurai19, Oct 10, 2008.

  1. samurai19

    Thread Starter New Member

    Nov 24, 2007
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    I am trying to map the labyrinth with ultrasound in both X &Y directions. It will be done row by row to get the complete map of the labyrinth.
    The time difference between reflections from walls of the labyrinth will be used as distance between the walls in that row.

    The problem is that will there be enough reflection from 5th or 10th wall back to my receiver? These walls might be back to back with minimum of 0.1m between them.
    The labyrinth will be 1m x 1m square, ultrasonic transducer will be outside of labyrinth and wall materials can be changed.

    Thanks in advance for any suggestions.
     
  2. studiot

    AAC Fanatic!

    Nov 9, 2007
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    An interesting project.

    Sounds like a case for experimentation.

    Are you using the same transducer for TX and RX?

    How are you displaying the RX output? You will obviously expect a decreasing signal with each reflection so the answer must depend upon the sensitivity of your display.
     
  3. samurai19

    Thread Starter New Member

    Nov 24, 2007
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    yet i dont know what i am going to use for TX and RX. but the output of the Rx will decoded and displayed on the LCD screen. The main concern for me is that is there any possiblity of getting reflection from 10th wall by changing wall material or transducer type. As the medium is air and its acoustic impedance is very small the wall material choice must be very accurate.
     
  4. beenthere

    Retired Moderator

    Apr 20, 2004
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    Have you considered obtaining the source and receiver and simply experimenting? Have you any idea for the interfacing hardware yet? Or the processor to use?
     
  5. studiot

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    Nov 9, 2007
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    Some more details would be helpful.

    I presume you are thinking of a variation of echo sounding or seismology.

    That is each wall vibrates on both faces and transmits an acoustic signal into the next airspace and thence to the next wall, also returning a reflected signal.

    So each wall will be distinguished by a (reduced) reflection, delayed in time. You can build up a 3 D by scanning back an forth.

    This is slightly different from ultrasonic tomography in medicine.
     
  6. samurai19

    Thread Starter New Member

    Nov 24, 2007
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    No, I did not yet had chance to test this idea. I just wondered to know if somebody else had done this before me, and what results are obtained. I just wanted to know is it possible mapping with ultrasound in air medium, because in air it is very difficult to have wave transmitted through any kind of wall as I know.
     
  7. studiot

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    Nov 9, 2007
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    This thread is posted in the projects forum.

    It would be helpful to us if you told us what sort of project this is.

    Is it school, college, university or for a bank robbery?

    At what level?

    What are your resources and what are the guide parameters for the project i.e. what are you trying to find out.

    Your scope is currently too wide. Why is wall material so important? I assume you will build out of something like 5mm MDF, even then I doubt you will reach a 10th wall. Corrugated cardboard sandwhich would be useless.

    Just construct a series of small chambers in series and test your TX/RX on these with an oscilloscope. You will soon see how far you can reach. The chambers need to be enclosed to transfer the sound across the air gaps.
     
  8. samurai19

    Thread Starter New Member

    Nov 24, 2007
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    :D
    It is university's graduation project.
    Wall material is important because reflection/transmision depends on its acoustic impedance.
    I will do some tests as soon as I get some ultrasonic transducers.
     
  9. bertus

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    Apr 5, 2008
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    Last edited: Oct 12, 2008
  10. studiot

    AAC Fanatic!

    Nov 9, 2007
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    We are still doing all the work here. My posts are several times as long as yours.

    It is an interesting project so I will add some more, but you need to be more forthcoming. Is this an Electronics or Physics question. Are the acoustic properties of real interest ?

    Not nearly so much as the damping factor of the material.
    I have appended a sketch for discussion. My test piece has chambers A,B, C and D. Separated by walls AB BC and CD.

    If the transmitter affixed to the outside of A is excited by a pulse this pulse will traverse the External wall of A and excite the air within. This will impinge on face AB and traverse wall AB, exciting face BA in turn.

    You are correct in that at each face there will be a transmitted and reflected component. The transmitted component will pass onto chambers B, C, D in like manner.
    The reflected component will return, attenuated, to the receiver after a time delay.

    If the receiver output fed to an oscilloscope, triggered by the same intitial pulse, a series of reducing responses will be observed, as in my sketch. I have also shown that each return response may be more finely resolved into two closely adjacent peaks, from near and far faces of each wall.

    You are correct in observing that the acoustic impedance determines the efficiency of transmission of energy from the wall to air and air to wall at each face. You are also correct in observing that the wall material plays a great part in how many chambers the signal will penetrate.

    But in order to pass from say chamber B to chamber C the signal must pass wall BC. If wall BC has high damping, because perhaps it is made of plasticine, signal passage may not occur. This is because th damping factor of the material is great, not because of its acoustic impedance, which is a surface phenomenon.

    The subject is open for discussion.
     
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