Isolating Vibrations with Active or Passive Technology

Two examples of the most advanced passive isolators are described in this article, air and negative-stiffness mechanisms. This technology is commonly used in high-tech applications such as nano-fabrication, micro-hardness testing, scanning electron microscopy (SEM), interferometry and scanning probe microscopy (SPM). Using air or negative-stiffness mechanism vibration isolators enhances the results produced in these applications.

air table

Air Passive Vibration Mechanism

The air passive vibration mechanism is a pneumatic system, which works by providing stability to a substantial bench or stage sitting on compressed air pistons. This enables the worksurface to be suspended in air by being the separating link between the floor and the work surface.

Air tables with the most advanced technology sufficiently remove ground vibrations. However this is a costly investment, and whilst they isolate in a passive manner, they must be supplied with air, have a leveling mechanism, and specific controls and upkeep.

Negative-Stiffness Mechanisms

Ambient vibration is not removed in the less advanced air mechanisms because they struggle to remove vibrations when it comes to the smaller frequencies and may only perform well in some directions. Things that are dealt with easily by negative-stiffness mechanisms. In addition, the use of electrical technology to level the air-table and control the air cylinder pressure increases the complexity and the possibility for failure.

negative-stiffness isolator

If looking for a solution for an instrument highly susceptible to interference from small frequencies and peaks caused by ground and room vibrations, negative-stiffness isolators deliver a straightforward, dependable and successful answer. In addition, the technology is light-weight, compact, durable and economical.

Furthermore, if necessary a fully mechanical isolator is available, the Minus K negative-stiffness isolator, which can have electronic auto-adjust technology added. The removal of unwanted vibration is attained by utilizing a collection of springs and negative-stiffness technology. Isolation with resonant frequencies as little as 0.5 Hz or less is delivered in 6 degrees of freedom using these mechanisms.

For technology that can deliver 0.5-Hz, isolation starts at approximately 1 Hz and in comparison to the highest functioning air tables in the 5-10 Hz series, results are 50-100 times better. This is especially significant in applications affected by ambient building vibration.

There is huge flexibility when planning the devices for a variety purposes, because more than one isolator can be used simultaneously whilst still behaving as one in respect to vibration. The technology is simple to use and adaptable, and the Minus K's negative-stiffness isolator has been effectively applied to sensitive instrumentation for loads from as little as a couple of pounds to lots of tons.

They can be more cost-effective when compared to air technology, occupies less area, delivers improved isolation at lower vibration frequencies, and needs zero upkeep.


As standard, negative-stiffness systems are not intended to manage high degree angular changes and impact loads that happen in automobile or plane applications. The functioning of instruments susceptible to unwanted vibrations in these applications can benefit greatly from the selective use of Minus K technology, significantly improving their results.

Both passive isolator mechanisms, air and negative-stiffness, can be affected by increases or decreases in temperature, however the user can adjust them in order to counteract these effects. When using the technology in a clean room or vacuum chamber, negative-stiffness mechanisms are preferred as air passive isolators may run into problems.

This information has been sourced, reviewed and adapted from materials provided by Minus K Technology.

For more information on this source, please visit Minus K Technology.


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