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Linear position measurement

Richard Manzini
Prodigy 20 points
Other Parts Discussed in Thread: TDC1000, TDC7200

With a proper transducer, can the TDC1000 be used to measure TOF in a metal medium (e.g. rod)?  Propagation speed is appx.  0.177 inches/microsecond. Pulse center frequency would be 39KHz.  Reflected pulse would vary based on the position of a magnet which induces a strain in the rod (magnetostriction effect).

Is there another part that would be better suited for such an application?

Thanks.

  • 0
    TI__Expert 4725 points

    Richard,

    You are correct. In theory the TDC1000 should work but it has never been tested. I understand the theory for the magnetostriction effect but I don't have a sense for the magnistude of the signals (both excitaiton and echo signal) involved.

    For the TDC1000 side of things excitaiton max = VDD = 5.5V and with piezos an echo of 1mV is workable.

    As for other parts I don't have any suggestions.

    Good Luck!

  • 0 in reply to Matthew Minasi
    TI__Mastermind 25990 points
    Richard
    We may be able to assist you even further if you could provide waveforms of the expected receive signals. Ideally Matt would need to know minimum and maximum amplitudes that you expect to receive as the magnet moves from closest position to furthest.
    This is an application where we are getting interest for the tdc7200 picosecond stopwatch timer but not our tdc1000 AFE.
    Chuck
  • 0 in reply to Chuck Sins
    Prodigy 20 points

    The narrowband pulse is a 3-10 mv pk-pk  sinusoidal signal composed of 3 cycles at fo=39KHz with an envelope consisting of the positive 1/2 period of a fo/3 sine shape. The bandwidth is approximately fo +/- 13KHz.

  • 0 in reply to Richard Manzini
    TI__Mastermind 25990 points

    sounds reasonable for us to support with the TDC1000 but I am worried about your positive half comment. we qualify waveforms on the negative portion of a wave after we ac-couple the signal around VDD/2.  sounds like we should take the conversation offline and discuss further (ie share some pictures).  I will send you a friend request so you have my direct contact info.

    Chuck