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Measuring a small amount of motion

  1. Mar 2, 2005 #1
    Hi all.

    I am working on a small project where i have a motion device, its a ball bearing in a metal pot with a metal rod running though the centre of it, as the ball moves around it makes and breaks contact between the rod and the pot.

    The output of this sensor is read by a micro-controller (from the signal transitions), and i have coded a small program to monitor this so i have change the senitivity.

    The problem is how do i measure the tiny movements detected by my design, so that i can put an actual figure on this sensitivity?

    Im thinking an accelerometer might do this, but does anyone know if they can detect tiny movement? any recommendations?

    Kind regards
  2. jcsd
  3. Mar 2, 2005 #2


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    Is this a single ball element or a full ball bearing? An accelerometer would do it if there is enough energy to induce an acceleration in the direction of measurement. Then you would have to double integrate the signal to get a displacement. Plus you would have to do an FFT on the time domain signal to give you a signal you could work with. It's definitely do-able.

    However, the first thing I would use is a prox. probe. We use prox. probes routinely to monitor whirl in shafts and bearings. I have a test right now that is using a prox probe as both a speed and displacement sensor on a bearing cage.

    I would like a little bit better description of your set up and what exactly you are measuring the deflection of though. Then we could really nail down a solution.
  4. Mar 3, 2005 #3
    Cheers for that Fred. I have to say i don't know what you mean about that type of ball bearing! the device is a "assem tect - vibration sensor (MS24M)" and the data sheet can be found here http://www.assemtech.co.uk/products/MS24M.pdf

    It is being user to tell whether the hardware is being moved. There will be an acceptable amount of movement allowed, but i need to quantify the figures.

    Does this help any more?
  5. Mar 3, 2005 #4


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    I am currently stuck out of town and the computer I have access to is a POC. I can not read your attachment. I was trying to get a better idea of what your set up is and what your description really is like. It's just not clicking in my head right now

    Are you trying to measure the amount that the beall bearing moves in the can? Describe the motion that you want to measure, i.e. rotational, linear, random...Perhaps my initial post is not what you will need.
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