The purpose of an electromagnetic site survey

…is to determine the types of electromagnetic (EM) phenomena that exist at a location, and measure their frequencies, levels and other salient parameters.

The EM phenomena that can be tested on a site range from d.c. to 40GHz (40,000MHz), including continuous and/or transient radiated and/or conducted phenomena. Power quality surveys (dips, dropouts, harmonics, interharmonics, etc.) are a limited type of EM site survey.

Site surveys can be very useful when trying to fix equipment unreliability problems. They can help determine whether the problem is being caused by EM disturbances, and can help point the way to a fix.

Site surveys help in the writing of EMC specifications for custom-engineered equipment – so that they can be designed and tested to achieve reliable operation in real life.

Also, when using very sensitive or volume-produced products, an EM site survey may be needed to determine what locations on a site they can be expected to operate reliably in – or to determine what levels of shielding and filtering are required to make them operate reliably in their chosen locations.

Surveys of sites’ EM environments may be necessary (or helpful) for the EMC compliance of “fixed installations” under the second edition of the EMC Directive (2004/108/EC), which comes into force on 1st July 2007.

When designing a new product, performing EM site surveys in all of the types of locations it may be used in is a very powerful tool in helping to design a low-cost product that has low warranty costs.

Site surveys for many EM phenomena can often be conducted quickly using low-cost hand-held survey instruments, to discover whether any possible problems exist. If possible problem phenomena are detected – more costly test equipment with greater accuracy and functionality can then be brought in to measure only the possible problem areas. This can reduce the costs and timescales of a site survey.

Most site surveys cannot measure every EM phenomenon that may be of concern, so completing an assessment of an EM environment may require some searches and calculation –see below.

Assessing an EM environment

Some EM phenomena occur too rarely to be measured by any realistic site survey, for example rare events such as lightning; high-voltage circuit breaker opening; earth-faults; etc.

For such EM phenomena the exposure of equipment can be assessed, based on prior knowledge and experience, usually with some searches into relevant publications, some calculations and maybe some mathematical simulations.

There is now a lot of good information available on EM environments of all types, so it is often possible to assess a site’s EM environment just from knowledge of the site and what equipment is used there, plus knowledge of its surrounding area.

Sometimes such assessments show that certain EM phenomena are possible but cannot put a limit on their magnitude. Such EM phenomena usually need measuring at the actual site. However, limiting a site survey to only those phenomena that cannot be predicted with good confidence helps reduce their costs and timescales.

How we work with customers
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How we can help

We can manage and/or perform site surveys for any/all EM phenomena, and we can assess EM environments in situations where site survey information is not available or not feasible. We hire the necessary test equipment.

We can assess EM environments and perform EM site surveys for any/all sites or environments, including…

  • Vehicles (land, rail, sea, air, space, etc.)
  • Buildings, campuses, factories, theatres, hospitals: any structure or site

…of any type, any size, for any application (including safety-critical, nuclear and military).

We speak plain English engineering language.

Our aim has always been to transfer our knowledge and experience to your own personnel, to get them up their learning curve quickly with the lowest costs, so they don’t repeat the costly mistakes that so many people have already made.

We recognise that design consultants like ourselves are not inexpensive to employ, so we aim to minimise what you spend on us. This means we are always trying to make ourselves redundant, so you need us less and less as your personnel’s expertise increases.

It costs much less overall to employ our training or expertise early in a project to help prevent problems from arising at all, or to fix any problems as soon as they appear.

How we work with customers
Download Non-disclosure agreement (Word document 36K)