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HOW TO MEASURE TIME OF FLIGHT

Discussion in 'Electronic Basics' started by [email protected], Aug 8, 2007.

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  1. Guest

    Hello,
    I'm trying to message a transducers time of flight. The transducer has
    two leads and has an operating frequency of 40 kHz. I would like to
    see the reflected wave vary when I move the target with respect to the
    initial pulse . I just don't know how to setup my equipment to do
    this. Could someone please tell me how to do this and if is the wrong
    forum please let me know where I should post this question.
    Thanks for any and all help.

    Best regards,
    Ken

    I have the following equipment:
    Tektronix TDS 3012B scope
    Tektronix 2246 scope
    B&k 3011 2MHz function generator
    Wavetek 4 MHz sweep/ function generator
    101 Pulse generator
     
  2. BobG

    BobG Guest

    Speed of sound is about 1120 ft/sec at std temperature and
    pressure.... about 1ms per foot
     
  3. I think the scope and pulse generator may be most of what
    you need. The biggest problem, after finding the best burst
    waveform will be the fact that the outgoing signal is
    thousands of times larger than the received signal. You use
    one trace, that triggers the scope sweep, on the outgoing
    burst, then use a second trace with a much higher gain, to
    see the returned signal. I think this trace should also
    have a series resistor and a pair of diodes across the scope
    input, to clamp the large outgoing signal, so that you don't
    severely overload the high gain vertical amplifier. If the
    scope has delayed sweep, you will have finer resolution on
    the timing measurement.

    If this sort of simple hook up does not have the gain to see
    the returned echo, you will have to build some sort of
    limiting amplifier to boost the signal and handle the huge
    overload of the outgoing burst.

    Can the target be a corner reflector, so that you have good
    reflection efficiency?
     
  4. neon

    neon

    1,325
    0
    Oct 21, 2006
    if you ever figure it out let me know the wavelengt is 3x10-10 cm does that help. if you are going to get a delay it will be because of you time delay in the electronics not from light shift you want to test that just short the input and measure it.dhh?
     
  5. Guest

    Hi and thank you fog your reply. I've never done anything like this
    would it be too much to ask to send me a schematic of the gen. and
    scope hook up along with the resistor/diode network.
    Once again thanks for taking the time to reply.
    Regards,
    Ken
    email address:
     
  6. Sorry, I think I will bow out, now. If you are not familiar
    enough with both the equipment and the transducer to take an
    educated guess as to how they should be connected, I doubt
    that my guesses that will have to be refined by
    experimentation will do you much good.
     
  7. Phil Allison

    Phil Allison Guest


    ** You had better get a second transducer and use that for receive only.

    Then ask one of the PAID STAFF at that lab to show you what to do.




    .......... Phil
     
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