What is EMC?
The term Electromagnetic Compatibility (EMC) covers all aspects of the interaction of electrical and electronic equipment with its electromagnetic environment and with other equipment.
Any electronic equipment can be affected by external disturbances: radio frequency fields, electrostatic discharge, conducted transient interference or supply voltage variations. Or it could generate its own interference emissions. Digital and microprocessor-based systems in particular, as well as electromechanical devices such as brushed electric motors, create noise which affects radio reception across the spectrum.
Good EMC design minimises both susceptibility to, and generation of, electromagnetic disturbances.
Why is it important?
Because of the threat to legitimate users of the radio spectrum, many countries limit the interference that equipment can generate. Perhaps your customers specify that their system performance must be maintained in the presence of electromagnetic interference. Even if they don't, you may have discovered an EMC problem with your equipment in a particular installation.
All products marketed within Europe should comply with the provisions of the various EMC-related Directives, which require both adequate immunity from interference and the minimum generation of interference. The US have had emissions legislation for many years, Australia has implemented its Regulatory Compliance Mark, and other Far Eastern countries have taken up the same process. If you sell within any of these countries, or into other safety-critical industries such as transport or process control, your product's EMC performance is important.
But it's such a difficult subject...There are many unknowns surrounding the question of EMC. What are the applicable standards and how do I find out about them? Which tests should I do and how do I do them? If the equipment doesn't pass the tests, what can I do about it? You need answers to all these questions. That's where EMC consultants Elmac Services can help you.
EMC design, test and management services
A major problem, which afflicts both large and small firms, is that EMC is a foreign subject: because it involves a combination of electrical, electronic, mechanical and software disciplines, it easily falls down the cracks between them.
RF electromagnetic phenomena depend on physical layout and stray, unintentional features like proximity of conductors and gaps in housings. Because product complexity means that unexpected interactions can and do occur, EMC has earned itself the name of a "black art". This is not actually so - all the processes involved have a solid physical foundation. But to get to grips with them calls for extra time and effort.
In these circumstances, the engineering approach is to call in expertise in the subject, to guide the resident designers towards the right solution. This needs someone who has specialised in EMC but has a background in design. That's where Elmac Services - the UK's premier EMC consultancy - comes in.
Design reviews are a regular feature of our work. The best time to ensure EMC requirements are dealt with is in the initial stages of design. We can offer you one-off review visits or an ongoing relationship, whichever you prefer.
Alternatively a lot can be done by e-mail. We are familiar with Cadstar, Altium, Mentor Graphics, Cadence Allegro, Proteus, Easy-PC and other PCB layout/schematic capture software and can look through your PCB designs without needing a visit. Comments are returned by e-mail, web conference or by telecon. For this we can charge an hourly rate for the work. We also have the ability to do some pre-compliance measurements and tests, though we're not a test house.
Here are examples of some of the projects we've taken on:
A manufacturer of hand tools was experiencing dramatic and unexplained variations in the conducted emissions from samples of one of its products. Elmac Services investigated the problem, discovered the cause and made recommendations for solving it - saving the client weeks in blind testing.
A large company wanted to establish its own EMC test facility for compliance testing of its product range. Elmac Services suggested the buying list for equipment, costed and evaluated the alternatives, supervised setting up the facility, wrote the test procedures and trained a select handful of staff in doing the tests - who then passed on their knowledge to their colleagues.
A small company making a transducer device for marine applications were faced with a need for a tenfold increase in RF immunity due to new certification requirements. Elmac Services redesigned the unit's interface, built some pre-production samples and had them tested for compliance (they passed with flying colours) and gave the company back a certificate and the new design drawings.
An automotive parts manufacturer was developing an innovative new product which they knew would be EMC-hostile but would have to meet stringent requirements at a low cost. Elmac Services acted as an external design review advisor for the project, making sure that early design decisions weren't such as would cause problems when compliance testing began.
We are also able to take on a variety of larger projects with an EMC theme, either alone or in partnership with other relevant organisations. Some examples include:
the research project on Calibration and Use of Artificial Mains Networks and Absorbing Clamps for the DTI's National Measurement System Programme (NMSP), in association with Schaffner and NPL; the report is downloadable from this site;
another research project on Uncertainties of Immunity Measurements for the DTI's NMSP, in association with Schaffner; the report including its appendices is downloadable from this site;
the EMC Awareness web site written in conjunction with Cherry Clough Consultants for the former Radiocommunications Agency; the entrance to the site can be found here (RA/Ofcom legacy site).If you have a project that is EMC related, we'll be happy to discuss it with you.
We have a great deal of experience in sleuthing down real life EMC problems. If your access system refuses to give access first thing every morning, or all your office monitors turn bright yellow whenever the air conditioning switches on, give us a call. It can save months of puzzling.
|Elmac Services, Chichester, West Sussex|