The importance of overload revealing in EMI receivers

The designing of instruments aimed to measure electromagnetic interference (EMI) is particularly challenging. The most critical aspect is the high dynamic range, which is required to avoid overload conditions and thus to guarantee reliable measurements. Unfortunately, also adhering to today's standards (i.e., CISPR 16-1-1) is not sufficient to avert overload phenomena. With three simple experiments, we show that it is crucial for an EMI receiver to incorporate an overload revealer to guarantee that overload conditions are detected correctly. Only then, can a receiver be set correctly in its linear range by using specific hardware inserted at the front end of the receiving path, i.e., a preselector and an attenuator. The combination of these three mechanisms - overload revealer, preselector and attenuator - turns out to be indispensable to avoid unnoticed overload conditions and guarantee reliable measurements.