How to determine your equipment needs

I recall someone once saying to me that “perception is reality.” But say this to scientists or engineers who need to take experimental data at midnight because their lab equipment is sensitive to even the minutest vibration and they may tell you otherwise. The reality is that imperceptible vibrations can and do impact sensitive experiments, and identifying the sources and selecting the proper equipment to minimize their adverse affect is important. Laboratories house a variety of vibration sensitive equipment used for research and production in fields such as laser based research, high-resolution imaging, semiconductor manufacturing, and biotechnology. Inserting electrical probes into nuclei of living cells, etching sub-micron lines in nanostructures, or taking SEM images requires laboratory environments to have vibration levels well below human perception thresholds. Floor vibrations can cause imaging components, specimens, lasers, or substrates to move relative to each other, causing blurry images, low yields, and erroneous results. The degree to which this relative motion affects results depends on the amplitude and frequency of the environmental vibrations as well as the sensitivity of the experiment. Ambient vibrations are omnipresent and can be grouped into two sources: internal and external sources. Common internal sources of vibration include foot traffic, flow excitation of air handling systems, unbalanced fans, vacuum pumps, and chillers. These sources can typically generate higher vibration levels than external ones. External noise sources are those coupled into the building structure itself and include elevators, ventilation motors, road and rail traffic, construction activity, and nearby heavy industry. Airports also can generate significant levels of low-frequency vibration noise (see Fig. 1). The location of a laboratory within the building with respect to these sources and to the structure in general can also impact noise levels. Laboratories and equipment located on upper floors in multistory Vibration site surveys can tell you a lot about how to specify equipment for vibration isolation in your laboratory.