The IEE's 10th International EMC Conference

Eur Ing Keith Armstrong CEng MIEE, Cherry Clough Consultants

The IEE held its 10th International Conference on EMC on the 1-3 September 1997 at the University of Warwick in the UK. This conference is one of the many EMC events organised by IEE Professional Group E2, whose members represent a wide spectrum of EMC expertise from independent consultants through test labs, Competent Bodies, manufacturers, and military, to university research and education.

This year's conference took a twin-track approach: technical or academic papers being presented in a lecture theatre; and workshop sessions dealing with more practical issues being held in a more informal room. This is my personal view of the event, which I found most interesting and rewarding.

The papers were arranged in 12 sessions of three or four papers each, covering:

Most of these papers were of a high standard, and it was interesting to see how the traditional uncertainties associated with EMC are being steadily eroded across the whole electrical industry - from controlling the signal integrity inside silicon chips to predicting the effects of lightning on installations.

One paper introduced the work being done by Nigel Carter's group at DERA on an "EM Hardening Tri-Service Design Guide", which should be a valuable contribution when it is complete. One of the features of engineering life seems to be the constant re-invention of the wheel, and this design guide should help reduce development costs for military hardware.

Co-incidentally, Tim Williams of Elmac Services gave a paper at the Euro EMC 97 conference on his proposal for a product design standard for good EMC performance. Tim's theme is that good techniques for building EMC into circuits and PCBs have been established for many years, but despite the wealth of articles, books, and courses available on the topic each new generation of designers have traditionally learnt EMC design the hard way - at their organisation's expense. A published standard covering EMC product design issues might be a way to overcome this problem.

One theme at the IEE's conference was the development of alternative test methods. I find it hard to understand why stirred-mode test chambers are considered perfectly acceptable for testing civil aircraft, whereas for more run-of-the-mill electrical products the latest EMC standards employ the more expensive and time-consuming open-area radiated emissions and anechoic radiated immunity test methods. Alternative (lower cost) test methods is a topic which E2 has been interested in for some time, and there are some very interesting developments underway in this area for which E2 is planning a substantial event in mid-1998. The workshops had a different theme for each of the three days:

The first workshop was arranged to cover what appears to be a common shortfall in many large construction and engineering projects, including some in the petrochemical and other hazardous industries - inadequate consideration of the implications of interference for plant safety. It was chaired by Peter Ridley of AMEC Process and Energy Ltd.

It seems that the introduction of the EMC directive has made people in general much more EMC-aware, but has led to the idea that interference may be taken care of by merely using equipment which has a CE mark on it. The CE mark is only something that allows goods to pass freely across national boundaries in the EU, and means nothing in any engineering sense, especially when one realises that manufacturers apply the CE mark themselves and that some are more diligent in their approach than others (putting it diplomatically).

The result appears to be that a proper engineering approach to control of interference in safety-related systems is sometimes neglected, and there is talk of some companies deliberately turning a blind eye to such issues until they are forced to do it by the Health and Safety officers who approve the operational safety cases for such plant. Do we really want to wait for another Flixborough or Piper Alpha to occur before the industry takes its responsibilities seriously?

Interference causes many problems in every sort of electrical system and installation, but for every one that gets officially investigated there must be hundreds (if not thousands) of incidents dealt with internally. Many such incidents are like near misses when driving a car - the worst outcomes are usually avoided more by luck than good judgement. Most EMC consultants have a wealth of experience with such problems, but are bound by client confidentiality not to discuss them in public. This leads to the misconception that historically interference is not a safety issue, which is compounded by the belief that a reliance on a historical lack of problems is some kind of legal defence - which it most certainly is not.

With sophisticated electronics, software, power conversion, and radio communications playing an ever-greater part in modern plants, the potential for serious safety incidents directly caused by interference are increasing. According to reports of transatlantic conversations over the internet, some designers of safety-critical systems are so wrapped up in the design of clever software that they cannot see that it will not be able to ensure safe operation when their computers have crashed due to interference, or when their chips have been turned into char by a power surge.

The machinery directive actually makes it a mandatory requirement to consider the effects of interference during the hazards and risks analysis, such as the possibility that the outputs of PLCs and computers can assume any combinations of states. Unfortunately this requirement is not spelled out in sufficient detail in EN 292, and it appears that some machinery manufacturers may not be taking this into account when constructing their Machinery Safety Technical Files.

The issue of EMC-related safety is an increasingly serious one, and one that E2 has recently decided to set up a working group on, to report before Christmas 1997. Peter has produced a summary of this workshop's conclusions which he is making freely available.

The workshop on Product Conformity was chaired by Dave Imeson of Compliance Europe, who is also secretary of the UKTLA and chairman of the ACB. It was a very lively event with a good deal of useful discussion, especially concerning the implications of the latest EC Guidelines on the EMC directive.

It is often thought that prosecution under the EMC directive is the main enforcement threat, but in fact (as Jim Rackham pointed out in his paper) Trading Standards have the power to suspend products from sale without going to court, and they prefer to use these powers. Jim gave an example of a company in his area whose EMC non-conformity had been exposed to Trading Standards by a competitor. In this case Jim did not have to do anything other than confront the manufacturer - who took his products off the market and redesigned them, with considerable expense and loss of income, without having to be told to do so.

Another issue if the Product Liability Directive, which is often overlooked as it does not involve CE marking, but which allows unlimited civil damage claims without requiring proof of negligence on the part of the manufacturer. Under this directive manufacturers are treated as guilty until they can show that their products could not have caused the injury or damage.

A presentation by Jim Wood of TUV Product Services (which used to be Assessment Services, and has nothing to do with TUV Rheinland) made the point that insurance companies such as Zurich are offering reduced product liability insurance premiums to companies who have their products third-party approved for compliance with EU directives. Apparently TUV Product Services have insurance which allows them to share the legal liability for defective products with their manufacturer, a concept which I understand is common in Germany but not in the UK.

Note that, as Dai Davies pointed out, although insurance is available to cover the costs and damages of court cases, and the costs of product recalls, there is no insurance yet available to cover contingent liability such as loss of sales, loss of market share, costs of re-engineering, etc.

Copies of the Conference Proceedings are available from the IEE's Publication Sales Department at Michael Faraday House, Six Hills Way, Stevenage, Herts , phone: 01438 313 311, fax: 0438 318 361, e-mail: sales@iee.org.uk.

Copies of the papers presented at the three workshops (but not the valuable discussions, unfortunately, you should have been there) are available without charge from Louise Hudson, Conference Executive, IEE, Savoy Place, London WC2R 0BL, phone: 0171 344 5467, fax 0171 240 8830, e-mail: lhudson@iee.org.uk.

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