Measurement of conducted emissions. Possible sources for measurement uncertainties

This paper presents results of investigations of the test setup for conducted emission measurements in the frequency rang from 150 kHz to 30 MHz according to CISPR 14:1993 and EN 55014:1993, respectively. It is addressed to EMC test engineers to give them an idea how slight variations in the test setup can affect the measurement results and increase the measurement uncertainty. The investigations were performed by using a real EUT, namely a gas heating device with a repetitive ignition unit which produces broadband disturbances. Furthermore a comparison of a type A and type B evaluation of the measurement uncertainty is presented. The obtained results confirm that the human factor as well as some degrees of freedom in the standards are sources of measurement uncertainty.