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Vibration Damping an Analytical Scale

  1. Jun 6, 2009 #1

    MATLABdude

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    Hello MechEs (or anybody else who'd care to reply)

    I'm about to get a small, but fairly sensitive analytical scale recently (down to 0.01 mg) and now I'm trying to figure out a way to dampen ambient vibration from the room and its surroundings (people walking around, HVAC, etc.)

    I've got a 200-lb slab of marble that I intend to put the scale on, and I plan to set the slab on a counter in a corner of the lab away from air drafts. I consulted one of the laser techs in the department who also suggested putting multiple vibration damping "pucks" between the slab and the counter. Apparently, they're neat to throw around because you can throw them really hard at the floor and they'll just land there without bouncing back. He's used them previously, but can't remember a brand name or supplier.

    Apparently, these are used to dampen speaker vibrations, and prevent transfer of roughing pump vibration to the floor.

    So has anybody ever used these before, and remember what they're called or where I can get these from? Better yet, does anybody have a better solution that isn't super expensive? (i.e. pneumatic supports, giant block of concrete, etc.)

    Thank you!
     
  2. jcsd
  3. Jun 6, 2009 #2

    Astronuc

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    Staff: Mentor

    Acoustic or vibration damping pads.

    Acoustica® Visco-Elastic Vibration Damping Pad
    http://www.acoustica.com.au/damping-pad.html

    ANTI VIBRATION PADS
    http://www.vibrasystems.com/?EC=Products&CategoryID=11

    Vibration Dampening Pads
    http://azsupply.thomasnet.com/viewi...ation-dampening-pads-vibration-dampening-pads

    https://www.amazon.com/b?ie=UTF8&node=16413781

    I've used microbalances that required a box covering to preclude any air movement. Even breathing near the balances caused noise in the measurement.
     
    Last edited by a moderator: May 4, 2017
  4. Jun 6, 2009 #3
    Sometimes I have seen magnetic dampers on sensitive scales. A strong permanent magnet is mounted on the scale base with its gap (about 5 mm) vertical. A thin aluminum plate (about 2 cm by 2 cm by 1 mm thick, about 1 gram) is mounted on the balance in such a way that it moves up and down in the magnet gap. The eddy currents in the thin aluminum plate damp the vibration.
     
  5. Jun 6, 2009 #4

    MATLABdude

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    The scale I've spec'd out has an air sash to prevent drafts from affecting the weighing pan. I thought about putting our (existing scale) inside my glove box, but with the reduced dexterity, and the large amount of scale drift (even though it's mg precision, it drifts like crazy, and repeatability at low masses is problematic), I thought it'd be better to just get a better scale.
     
  6. Jun 8, 2009 #5

    minger

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    We have a professor at a local university who makes precision measurements for bearings and spring rings. He had some experience using those damping pucks and said they were nowhere near as close to the quality that he needed.

    He then started using some sort of air-hockey-type think IIRC and said that it was far better. Something tells me he now has lasers somehow involved (may or may not be mounted on top of sharks' heasds).
     
  7. Jun 8, 2009 #6
    I'm sure the laser guy mentioned that the pneumatic supports are the best solution and are used for sensitive optical measurements. Clearly it is expensive to buy a proper optics table, with supports and an air compressor. However, I've seen amateurs use a wooden box filled with beach sand and supported by inner tubes. I've heard that this simple damping system is good enough to make holograms. If you don't have a powered compressor, a hand pump is cheap and will work.
     
  8. Jun 24, 2009 #7

    MATLABdude

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    I'm going to resurrect this thread with a related question. Would it be better to use numerous pads (incomplete coverage of the slab) or a single sheet (underneath the entirety of the slab)? I'd think the first would be better, as there'd be less surface area, and lower coupling efficiency from the surface of the table to the slab and the scale lying on top of it.

    Thanks again for all the suggestions received so far in this thread.
     
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