Vibration Isolation Table

1.What is a vibration isolation table?

A vibration isolation table is a support platform that prevents floor vibration from reaching equipment placed on it. Instruments that resolve nanometre-scale detail — scanning and transmission electron microscopes, atomic force microscopes, interferometers, semiconductor metrology tools — are disturbed by floor motion far below the threshold of human perception, and the isolation platform is what keeps that motion out of the measurement.

Two mechanisms are used. A passive isolator supports the payload on an air spring so that vibration above the spring's natural frequency is attenuated mechanically. An active isolator measures vibration with sensors and drives actuators to generate an equal and opposite force in real time, which removes the low-frequency limitation of the passive approach entirely.

The term should not be confused with seismic isolation in civil engineering. Building seismic systems address ground motion of several centimetres during an earthquake; an instrument isolation table addresses continuous ambient vibration measured in micrometres per second.

2.Why vibration isolation matters

Laboratory and fab floors are never still. Air handlers, chillers, vacuum pumps, lifts, road traffic and foot traffic all inject continuous vibration into the structure, and the dominant energy sits in the 1–30 Hz band — precisely where sensitive instruments are least tolerant.

Instrument vendors express the requirement as a site vibration specification, usually a VC (Vibration Criterion) curve. VC-A permits 50 µm/s RMS in one-third octave bands, and each further step halves the allowance down to VC-E at 3.1 µm/s. A tool rated for VC-D installed on a floor that only meets VC-B will show image distortion, loss of resolution, and poor repeatability regardless of how well the instrument itself is specified. The criteria and how they are measured are covered in our technical note on generic vibration criteria.

Because the requirement is a measurement, not an opinion, the honest way to select a platform is to survey the floor first and verify afterwards. DAEIL SYSTEMS publishes the before-and-after vibration measurements from its installations as over 1,000 case studies, indexed by instrument so you can find installations on the same equipment.

3.Active vs passive isolation: the numbers

The difference between the two approaches is entirely a low-frequency story. A passive pneumatic isolator is a spring with a natural frequency of 1.2–3.0 Hz. Below that frequency it transmits vibration directly, near it the payload is amplified, and only above roughly 5–10 Hz does it isolate well.

An active system has no resonance to amplify. Sensors detect motion, a digital signal processor computes the counter-force, and actuators apply it, so isolation begins at 0.5 Hz. On the DVIA-ML, 80–90% of floor vibration is removed at 1 Hz and 90% or more at 2 Hz and above, across all six degrees of freedom, with a control bandwidth of 0.5–200 Hz.

This matters because the 1–5 Hz band is where building floors move most and where passive isolators are weakest. If a vibration survey shows the problem is above 10 Hz, a passive platform may be entirely sufficient and is cheaper to own; if the problem is below 5 Hz, no passive isolator will solve it.

4.Types of isolation platform

Active isolation tables carry the instrument on an actively controlled platform and are the default for electron microscopy and semiconductor metrology. The DVIA series covers tabletop units through to systems supporting 20,000 kg.

Passive pneumatic isolators use air springs and need no power, which makes them simple to maintain and effective where the disturbance is above about 10 Hz. They are supplied as DVIM mounts fitted beneath equipment.

Optical tables place a honeycomb-core tabletop on isolation supports and are used where a large, stiff work surface is needed for laser and photonics work. DVIO research-grade tabletops have a first resonance of 313 Hz; a stiffer top means fewer structural modes inside the measurement band.

Isolated foundations decouple the equipment base from the building floor itself. DVIF is installed in semiconductor and display production lines where the access floor cannot meet the tool specification, and DVIP-B low-profile platforms serve heavy equipment that must stay close to floor level.

5.Vibration isolation for electron microscopes (SEM, TEM, AFM)

Electron microscopes are the most demanding case because their sensitivity peaks in the same 1–5 Hz band where buildings move most, which is why active isolation is effectively the standard rather than an upgrade.

DVIA-ML is designed specifically for SEM and TEM columns and supports 1,500 kg (ML1000) or 3,500 kg (ML3000) with active control from 0.5 Hz to 200 Hz. Its velocity sensors are amplified and digitally corrected to remain effective down to approximately 0.3 Hz, which is what makes 80–90% isolation at 1 Hz achievable.

Column requirements and how to read a tool vendor's installation specification are covered in our SEM and AFM isolation note, and the surrounding room conditions — acoustic noise, magnetic fields, air flow — in electron microscope room requirements. Vibration is rarely the only environmental constraint on an imaging site.

6.What determines the price

There is no single list price for a vibration isolation table, and any figure quoted without knowing the site is a guess. Four variables set the cost, roughly in order of weight.

Load capacity and platform size come first, because they determine the isolator count and the structure beneath the payload — the span from a tabletop unit to a system supporting 20,000 kg covers two orders of magnitude in material and engineering. Isolation type is second: an active system carries sensors, a digital signal processor and actuators, so it costs more to build and needs power, while a passive pneumatic platform is mechanically simpler.

Third is the vibration specification to be met. Reaching VC-C on a quiet floor is a different engineering problem from reaching VC-E next to a chiller plant, and the harder target may require a larger platform, a custom frame, or an isolated foundation rather than a table. Fourth is what surrounds the hardware — site vibration survey, installation, tuning, and post-installation verification measurement. A quotation that omits the survey and the verification is cheaper on paper because it moves the risk to the buyer.

For that reason DAEIL SYSTEMS quotes after a vibration survey rather than from a price list: the correct configuration is a conclusion drawn from the measured floor, not a catalogue choice.

7.How to choose a vibration isolation table

Work through five questions in order. First, what is the payload mass and the required table size — this eliminates most of the catalogue immediately. Second, what does the floor actually do: a vibration survey in one-third octave bands, taken at the installation position, not an adjacent room. Third, what does the instrument vendor require, expressed as a VC class or an equivalent velocity limit.

Fourth, compare the two: if the gap between measured floor vibration and required level sits below 5 Hz, an active system is necessary; if it is above 10 Hz, a passive platform will usually close it at lower cost. Fifth, verify after installation by measuring again — a specification that is never checked is a claim, not a result.

A fuller checklist, including the questions worth asking a supplier before signing, is in our platform selection guide.

8.Limitations of improvised and general-purpose solutions

Rubber pads and elastomer mounts are stiff enough that their natural frequency typically lands between 8 and 20 Hz. Above roughly 15–30 Hz they help, but they do nothing in the 1–5 Hz band that limits electron microscopes, and they amplify vibration at their own resonance.

Sand tables, stacked foam and similar improvised assemblies suffer the same physics: isolation only begins above the resonance of whatever spring has been created, and an assembly that has never been measured has an unknown resonance. Damping without a defined natural frequency does not produce isolation.

Sealed passive pneumatic isolators are genuinely effective above roughly 5–10 Hz, and there is nothing wrong with using them when the survey shows the disturbance sits there. The failure mode is applying them to a low-frequency problem, where the payload sits near resonance and vibration is made worse rather than better. The decision should follow the measurement, not the product category.

Frequently asked questions