GENERAL

ACOUSTIC ISOLATION

VIBRATION ISOLATION

EMI ISOLATION

SITE SURVEY

The following suggestions are designed to minimize the effects of noise on sensitive measurements and maximize the performance of isolation systems. These are general tips, individual circumstances may vary.

GENERAL

• Avoid areas near high traffic areas. This applies to freeways and parking lots, but also construction sites and mass transit lines.

• Avoid rooms near noise-generating equipment, such as machine shops and HVAC systems.

• If possible, locate sensitive measurements and processes outside of cleanroom areas.

• Isolate the source of noise from the surrounding area.

• Cables which attach to instruments can transmit acoustic, vibration, and EMI noise into the system. Make sure cables are slack, weighted, grounded, and aren’t causing a break in the seal of an isolation system.

 ACOUSTIC ISOLATION

• Avoid air vents which can cause interference from air movement. If necessary, create a baffle which will divert the flow of air.

• Avoid noisy hallways and rooms. Close the room door before beginning sensitive measurements. If necessary, institute quiet hours during which measurements can be taken with minimal interruption.

• Don’t place noise-generating equipment such as CPUs or pumps on an acoustic enclosure or on the support frame. If possible, place noise-generating equipment in a separate room.

• Before beginning sensitive measurements, make sure that the enclosure is totally sealed. Close and latch the enclosure door and make sure cable clamps are attached tightly.

VIBRATION ISOLATION

 General

• If possible, locate your lab in the basement or on the ground floor. Avoid higher floors.

• Locate instruments near load-bearing walls and columns. Avoid the center of the floor.

• Place desktop isolation systems on rigid support structures. Avoid flimsy desks and tables.

• Mechanically decouple the instrument from noise-generating equipment or noisy floors.

Active Vibration Control

•  The instrument should have solid, flush contact with the top of the isolator to ensure full performance.

AVI Series

• Should be placed on flat mounting surface to avoid deformation under heavy loads.

• Should be placed on level mounting surface to ensure proper load adjustment.

• Modules should be oriented parallel to one another in a mirror image (ie. D-sub cable ports on modules facing towards each other or facing away from each other)

• If the load on top of the modules is altered significantly, either by changing the weight or center of gravity, the load adjustment on the modules should be checked.

TS Series

• Lock system down prior to transport or moving load.

• Adjust leveling foot to ensure system is sitting flush on support surface.

Air-based Isolation

• Do not over-inflate the system, this can damage the air suspension system. Inflate the system gradually to avoid over-inflation.

• Check that system is floating once a week.

• Deflate the table prior to moving the table or the equipment on top of it.

• Avoid the following when using a air-based isolation system: Direct sunlight, Ozone environments, Volatile solvents, Oils, and Excessive or unbalanced loading.

• Contact Herzan prior to drilling any holes in the system. There is a danger of puncturing the air suspension system.

• When transporting to a new location after installation, contact Herzan for advice on packing.

• Avoid areas near elevators, escalators, and vehicle traffic.

• Beware of pumps, fans, and other pieces of equipment with moving parts.

• Make sure that your instrument is well-grounded.

SITE SURVEY

• Ensure that you are not changing parameters between tests which you plan to compare.

• The more averages that are taken, the more noise will be filtered out. Taking more averages will ensure more accurate data.

• For vibration testing, make sure the sensor is firmly coupled to the surface you would like to measure. For light accelerometer heads, adhesive or wax may be required to ensure a firm coupling.

• Beware of 60 Hz spikes in the data. These are often related to electro-magnetic interference and can be an artifact. If you notice significant 60 Hz spikes in your data, make sure your testing set-up is grounded properly and run the test again.

• Narrow the frequency span of your test to achieve better frequency resolution. If you are unsure of the frequency area of interest, start with a broad frequency range and narrow your focus based on results.

• Significant resonances in one axis can often feed into other axes and appear in the data for other directions. Measure multiple points in different locations to diagnose the phenomenon.

• Noise levels change throughout the day, due to foot and street traffic, equipment running, and other causes. It is recommended to run tests at different times of day to filter out the periodic noise.

• When doing comparative measurements, eliminate as many variables as possible. If possible, take the data simultaneously using identical sensors, with the sensors aligned.