Vibration Damping an Analytical Scale

In summary: I'm thinking about using a single sheet of vibration damping material, between the slab and the counter, to reduce ambient vibration.
  • #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!
 
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  • #2
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/viewitems/categories-shop-equipment-vibration-dampening-pads/-vibration-dampening-pads-vibration-dampening-pads

https://www.amazon.com/b?ie=UTF8&node=16413781&tag=pfamazon01-20

I've used microbalances that required a box covering to preclude any air movement. Even breathing near the balances caused noise in the measurement.
 
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  • #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.
 
  • #4
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.
 
  • #5
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).
 
  • #6
MATLABdude said:
Better yet, does anybody have a better solution that isn't super expensive? (i.e. pneumatic supports, giant block of concrete, etc.)

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.
 
  • #7
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.
 

1. What is vibration damping?

Vibration damping is the process of reducing or eliminating the unwanted vibrations that can affect the performance and accuracy of an analytical scale. It involves using materials or techniques to absorb or dissipate the energy of the vibrations, resulting in a stable and precise measurement.

2. Why is it important to dampen vibrations on an analytical scale?

Vibration damping is crucial for an analytical scale because even the slightest vibrations can significantly impact the accuracy of measurements. These vibrations can come from various sources such as nearby machinery, foot traffic, or even air currents. Damping vibrations helps to ensure reliable and consistent results.

3. How do you dampen vibrations on an analytical scale?

There are several methods for damping vibrations on an analytical scale. One common approach is to use vibration-dampening materials such as rubber or cork to isolate the scale from external vibrations. Other techniques include using pneumatic isolation systems or installing the scale on a stable and sturdy surface.

4. Can a scale be too sensitive to vibrations?

Yes, a scale can be too sensitive to vibrations, especially in laboratory settings where precise measurements are critical. In such cases, it is essential to take measures to dampen vibrations to ensure accurate results.

5. How can I test if my analytical scale is affected by vibrations?

One way to test if your analytical scale is affected by vibrations is to perform a repeatability test. Place a known weight on the scale and take multiple measurements. If the results vary significantly, it is an indication that vibrations are affecting the scale's accuracy. You can also use a vibration meter to measure the level of vibrations in the area.

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