Ultrasound Experiment. Suggestion to direct reflected signal??

Discussion in 'The Projects Forum' started by Student12, Feb 6, 2012.

  1. Student12

    Thread Starter New Member

    Feb 6, 2012
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    Hello,

    I am constructing an experiment to measure the nonlinearity of water using ultrasound. The experimental setup is as follows:

    A function generator produces a tone burst sine signal into an amplifier then into an ultrasound transducer. The transducer is immersed in water perpendicular to a steel block which reflects the signal back to the transducer.

    My problem is that i want the reflected signal to be directed to an oscilloscope and not go back into the amplifier. Can someone suggest any device that would direct the signal in one direction? A circulator was suggested but i am working with a frequency of 0.5 MHz.

    If anything is unclear please mention and ill elaborate. Any help or suggestions is highly appreciated!

    Thanks
     
  2. PaulEE

    Member

    Dec 23, 2011
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    I admit that I don't know much about ultrasound in water, but, what do you mean by "measure the non-linearity of water"?

    Could you simply use a steel block with a 45* angle, such that the detector can sit 90* from the "line-of-sight" of the transducer output?

    You can also put something that'll absorb the 500 kHz behind the detector to prevent bounce-back from that..?
     
  3. Student12

    Thread Starter New Member

    Feb 6, 2012
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    Thanks for you reply. But the issue here is not the nonlinearity of water, i can explain if you're interested. Basically when the ultrasound transducer produces a signal in water, the steel block which is sitting exactly in line with the transducer reflects the signal back to the transducer. Assuming that the steel block reflects 100% of the signal, we are left with a signal that has been attenuated by water.

    When the signal goes back through the piezoelectric transducer, i basically want a device to direct it to an oscilloscope without it going back to the amplifier. there is only one cable that goes through the transducer.

    Did you get my point?
     
  4. PaulEE

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    Dec 23, 2011
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    So, you want the signal, instead of going back into the amplifier output, to go to an oscilloscope, using the single transducer as a transmitter and then detector/receiver?
     
  5. Student12

    Thread Starter New Member

    Feb 6, 2012
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    Yes! Thats exactly my point.
     
  6. PaulEE

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    Dec 23, 2011
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    Hmm...

    How is it constructed presently? Can you modify the output circuit?

    The signal bouncing back into the amp shouldn't be too big a deal. You could use the '4066 I mentioned above to direct just the received signal to the scope probe if you have a trigger source?

    Wait...never mind.

    I don't see a way around this without putting another sensor in close proximity. Unless you made an electronic switch out of mosfets that would allow the transmit signal through and block it as it bounces back...
     
  7. Student12

    Thread Starter New Member

    Feb 6, 2012
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    I have done this experiment before by just using a Pulser/Receiver box without an amp nor function generator. That wasn't a problem as this box is made to receive a signal.

    I am doing mechanical engineering and i have no idea about electronics and circuits.

    The experiment is very simply setup by cables between the generator --> amp --> transducer. My plan is just to put a device between the amp and transducer that will allow the signal to go from amp to transducer but when its reflected back it'll go to an oscilloscope. I have suggested to my supervisor to put a receiver in the water tank but he insists that i only use one transducer that transmits and receives.

    I was searching online and the device that made sense to me is a circulator. Assume a circulator with 3 ports... signal from amp (port 1) goes to transducer (port 2)...signal back from (port 2) is directed to oscilloscope (port 3). There is no input signal from (port 3) so (port 1) is safe. But I'm not sure about that.
     
  8. PaulEE

    Member

    Dec 23, 2011
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    According to the wiki I just read, a circulator is something along the lines of a waveguide, which is used at frequencies whose wavelength is on the order of the dimensions of the waveguide. Those dimensions are usually on the order of inches or feet. The wavelength of 500 kHz is 300,000,000/500,000 = a lot more than a few feet.

    Did he give a reason as to why you MUST use the same device?
     
  9. Student12

    Thread Starter New Member

    Feb 6, 2012
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    Hmmm i see. Not really he didn't. Ill go to him and ask him again.

    Thanks for your help!
     
  10. PaulEE

    Member

    Dec 23, 2011
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    Let me know what he says!
     
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