A lesson in EMC benefits

Louise Smyth

Anthony Waldron recounts how an education in electromagnetic compatibility gave his company significant cost and time savings

Electromagnetic interference (EMI) is a key concern among electrical engineers and plant managers due to the elevated costs and performance problems that it creates.

While electromagnetic compatibility (EMC) has been a requirement of electronics and equipment for many years, there is still much misunderstanding surrounding it.

In 1994, CADAC Electronics decided to make sure that all of its products would meet the forthcoming EMC regulations.

Since the company knew very little about EMC at the time, or how to design equipment to meet the regulations, we looked for a suitable consultant. CADAC chose EMC Standards’ Keith Armstrong because of his experience with audio system design, working for many years with the famous Neve company that designed and built similar high performance audio control systems for recording studios.

The initial EMC training course from Keith solved many system problems that had plagued the company for several years.

Unfortunately, some of the CADAC engineers could not accept that their understanding of the grounding principles they had used for many years required updating.

After being subjected to arguments about the principles of grounding for several weeks, I persuaded the management to use the EMC design techniques for the design of the company’s latest mixing console system.

This system, called the F-Type, was a cost-effective version of CADAC’s very successful J-Type mixing console, which was being used worldwide on musical theatre productions.

When the final audio tests on the F-Type were complete, the results were impressive.

CADAC’s engineers had become so used to the fact that the microprocessor control circuits would inevitably ruin the audio noise figures that the absence of digital processing noise was a shock.

Several engineers suggested that the computer control system was not working, which was why the noise figures were so good.

The whole system was demonstrated to be working fully and that the total system noise had been reduced by 10dB.

Subsequently, audio testing showed that the radio frequency input and output filtering improved the audio performance so significantly that customers would call to ask what had been done to improve the sound quality.

The very successful J-Type was then redesigned using Keith's EMC system design techniques to bring it into line with its lower cost companion product.

When EMC design techniques are used at the beginning of a design, the overall cost is minimal. However, we soon found that there were substantial cost savings to be made during final testing and installation of our console systems.

The time taken for the console final test was reduced by 50 per cent, which led to significantly reduced project duration. In fact, during the installation of two consoles for a concert at the Royal Albert Hall, the staff complained about finishing too early and not getting paid triple time for working on the Sunday.

For advice on EMC design and testing, as well as access to a number of educational resources, visit EMC Standards HERE

Anthony Waldron is former technical manager of CADAC Electronics from 1989 to 2014.