Measuring EMC emissions in the real world

Standard techniques for the measurement of emissions for most products require the use of an OATS (open area test site). In reality, very few organisations (excluding the Test Laboratories) have access to such facilities. However, an increasing number of organisations, particularly in Europe and increasingly in the US, are intent on conducting their own emissions checks, either for self certification or pre-test purposes. A study of the measurement uncertainty associated with the checking of emissions on a typical test site shows that in general these sites will introduce massive errors, unrelated to the cost or complexity of the instrumentation. This situation has been largely ignored by the industry but it is hoped that this paper will open up discussion in this field. The sources of this uncertainty are discussed and a technique described for measuring and correcting for these errors.