This article discusses the basics of isolation for sensitive scientific measurements in precision research.
Selecting the Appropriate Location
Locations with higher levels of seismic activity, oceans and large bodies of water are not suitable to build a precision research laboratory. Bedrock areas are preferred over sand, clay, or reclaimed land. Mass transportation lines, busy streets, large-scale construction and mining operations are also other sources of concern.
The rigorous noise prerequisites of the instrumentation to be installed must be considered in the construction of a precision research laboratory. EMI, acoustic, and vibration specifications are critical in the design phase. Short buildings with wide foundations are preferred as tall buildings are prone to horizontal swaying. It is recommended to build the labs on slabs that are secluded from the rest of the building foundation.
Choosing the Right Location within the Building
The basement of a building is the best location for a precision research laboratory due to less foot traffic and minimal risk of horizontal sway. Considering the reduced levels of low frequency vibrations, lower floors are the next best location in case of non-availability of a basement location.
HVAC systems are a major source of intra-building noise. Machine shops, loading docks, manufacturing areas, mechanical rooms, areas involving elevators and water pipes must be avoided. It is recommended to have the lab site as far as possible from external noise sources such as busy streets and parking lots.
The center of the floor must be avoided due to higher levels of vibration. The trampoline effect exhibited by unsupported floors can be lowered if precision instruments are installed near a load-bearing wall or column.
Corridors are also not ideal locations due to higher levels of noise or foot traffic. Air handling equipment is generally used in clean rooms, causing air current disturbance. Hence, it is advisable not to place the precision instruments in clean rooms, unless a special clean room support is used to bypass the raised floor (Figure 1).
Figure 1. Cleanroom support stand with active vibration control modules
Decoupling the Source
Stopping troublesome noise at the source is a better option because complete noise elimination is not possible with environmental isolation systems. Moreover, one source of noise is able to affect several instruments.
Hence, avoiding the noise transmission to the surrounding area is a simple and economical solution when compared to isolating each sensitive instrument individually. Once the source of noise is located, turning off or removing it from the site is the best solution.
If this is not possible, the source must be decoupled from the rest of the building by shifting it to another site or installing it outside using duct or cable extensions. Decoupling the instrument’s slab from the rest of the building is another option.
Isolating the Precision Instrument
If decoupling the source of noise becomes ineffective, isolating the sensitive instrument from the source of noise is the next step. Mechanical decoupling will drastically decrease the amount of energy to be transmitted, and is often implemented at the construction stage of a facility.
Placing the sensitive instrument on an isolation slab is another method of preventing the vibrations of noisy equipment from getting transmitted to the sensitive equipment, but is an expensive option. If cables or hoses cause the troublesome noise, they must be disconnected, weighted or replaced.
Improving the Support Structure
The unwanted resonances introduced into the system by weak supports amplify incoming vibration. Hence, it is necessary to use a sturdy, rigid structure as supports for the sensitive instruments.
Adding weight to the system is the next step to lower the effects of high frequency vibrations, which are generally lower energy. A system’s resonant frequency will be changed with increasing mass, causing changes in the characteristics of the system itself.
This makes the system less susceptible to a given source of noise. Protruding pieces may serve as conductors for acoustic noise, and therefore must be found. Properly grounded support can tackle emi issues.
Dampers reduce the amplitudes of mechanical resonances induced by incoming vibrations. Rubber feet, sorbothane mounts, viscoelastic pads are some of the basic dampers that work effectively for most applications (Figure 2).
However, in some cases, they are not able to effectively reduce the amplitude, leaving troublesome resonances undamped. Nevertheless, a trial-and-error process is viable considering the less cost of basic dampers.
Figure 2. Examples of basic rubber isolators (Image Courtesy of Boris Shapiro via Wikimedia Commons)
Physical barriers such as acoustic curtains and cubicle walls are the simplest damper to tackle acoustic noise, providing a basic level of reduction. Constructing a box around the sensitive instrument is another approach.
Rudimentary enclosures normally use styrofoam, plywood, and cardboard. However, enclosures pose challenges in terms of ergonomics, accessibility and visibility. For emi problems, fabricating a basic faraday cage from a sheet metal is a better option than a bulky and costly steel box.
Herzan provides high performance environmental solutions for precision research instruments. They include acoustic enclosures, vibration isolation systems, Faraday cages, and site survey tools. Herzan specializes in supporting nanotechnology research, but also offers solutions for product testing, in-vitro fertilization, and many other applications.
Herzan understands that every application and environment is different, so it collaborates with customers to create comprehensive integrated solutions that satisfy their unique demands.
Herzan was founded in 1992 by Ann Scanlan in Orange County, California. Originally, Herzan was established as an American subsidiary of Herz Company Ltd., a Japanese company specializing in vibration control. The name Herzan comes from the amalgamation of 'Herz' and 'Ann'.
This information has been sourced, reviewed and adapted from materials provided by Herzan LLC.
For more information on this source, please visit Herzan LLC.