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Help: Sensor needed for very special application:

Discussion in 'Electronic Design' started by BikeManiac, Jul 10, 2006.

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  1. BikeManiac

    BikeManiac Guest

    1. A dark chamber (Hermetically closed).
    2. In the chamber a circular disc is mounted on an electric motor. The
    disc is mounted horizontally in the chamber.
    3. The diameter of the disc is 2 meters (2 yards).
    4. Now the disc runs at about 25 rpm and a mix of sand and rocks is
    poured on the table.
    5. Due to centrifugal forces the sand/rock mixture starts to move
    6. While running there is also a dust/sandstorm present inside the
    chamber. The dust/sandstorm is so severe that one cannot see a hand in
    front of himself (with a torch).

    Under those conditions I want to be able to measure the sand/rock flow
    on the table. I want to see what happens when and how the sand/rocks
    move towards the edge of the disc. I want to see how fast, I want to
    see if anything builds up etc etc. The perfect thing would be to
    install a video camera inside the chamber but due to the sandstorm this
    is virtually impossible to my opinion. Are there any sensors available
    giving a hight profile as an output? What about doppler, ultrasound,
    infrared and so on? What is the most promising sensor solution for this

    To me, this sensor looks very interesting:

    ....but I'm afraid that this wont work because the laser light wont be
    able to penetrate my sandstorm.

    Do you experts have any solutions for my problem?


    After measuring the material flow on the table, I need to measure how
    the particles move in the sandstorm - more precisely in what direction
    they are moving and at what velocities. What sensors would be suitable
    for that task?

    PS: All sorts of equipment can be installed inside the chamber, such as
    flourescent light, regular light etc etc.

    Thank you in advance, L. Jensen
  2. Bob Eld

    Bob Eld Guest

    Ultrasound is probably your best bet. I envision some form of side scan
    sonar like used to visulize the sea floor, etc. It sends out an ultrasonic
    pulse directed at an angle to the rotating disk then listens for recived
    reflections off of the disk. The arival time of the reflected waves is
    proportional to the distance of the reflection from the disk thus forming a
    scan. The fine scale time variations are used to image the shapes of objects
    on the disk Doppler can be used to determine if there is relative motion of
    the objects. The scan is repeated many times per second to build of an image
    of objects on the disk as it rotates. Several of these side scan units could
    be employed around the disk to enhance the image of the detected objects and
    to determine how things moved with rotation angle. This would require a fair
    degree of digital image processing, but I think, is doable. Needless to say
    you are probably not going to find a ready made, off the shelf hardware and
    software to do this. Be prepared to spend some bucks.
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