Troubleshooting EMI (Part I, Emission Problems)

Some simple hints . for identifying and fixing EMI troubles. This article covers the essential aspects of a domain which is seldom addressed in current EMC litterature: «What to do when an equipment – or a whole system – is failing the tests or experiencing Interference (EMI) problems ?». Whatever we are dealing with a prototype at the end of its development phase, failing one or several EMC tests, or an already installed equipment that exhibit on-site problems, we face a situation that must be solved quickly, with an equipment that cannot be deeply modified.

Contrasting with a development phase where many EMC solutions are available on a product that is still flexible, the engineer confronted to a failing equipment has to detect, diagnose and fix a problem that could be unpredictable, with elusive symptoms, troublesome and penalizing for the user. RFI, ESD, Transient surges, Crosstalk are complex threats involving many interactive mechanisms. No human brain can see at a glance all the possibilities and limitations of the available solutions, where options are limited anyway.


Here we will explain how to identify an EMI problem and its coupling paths in order to correct it with fixes that must be quick, using components that are readily available and applicable in the field, if necessary. All this by using instruments and accessories that are portable, rugged and relatively unexpensive, not requiring the sanitized environment of an anechoic shielded room.


This Part I of the article is focusing on EMI Emission problems. A forthcoming article, Part II will cover Susceptibility problems, including those occuring in the field, where we do not have the commodities and elbow room we enjoy in a development lab.


Note: Readers interested by this topic should read – or briefly return to – our articles 1 to 8 (EE magazines #2015.3 /September, to #2017.1 / March), such as they acquire a basic knowledge of EMI/EMC. Unless you are already a seasoned EMC specialist, the present article without such basics would be worthless since it contains no theory. Rather, it gives practical guidelines for most EMI crash situations…


Dear colleague,

This text is unfortunately locked for further reading, but you can read all Michel Mardiguian’s texts and course material about EMC in the new book ”Everything you always wanted to know about EMC but were afraid to ask”. Click for more information!