Experimental analysis of Conducted Electromagnetic Interference measurement variations

As per international EMC standards, conducted electromagnetic interference (CEMI) measurement shall be carried out by providing the power supply to the equipment under test (EUT) through a line impedance stabilization network (LISN) by means of an one-meter length cable and the EUT shall be kept at 40 cm distance from the vertical coupling plane (VCP), to avoid the influence of reflections, due to nearby objects, in the test results. Also, the longer power and signal cables are folded back to keep the length one-meter or less. These conditions are followed to ensure the repeatability in CEMI measurement. However, due to negligence of EMC test engineer or confusion in the test configuration, standard test conditions are not followed and resulting in non-repeatability in the measurement. In this paper, such common errors occur in CEMI measurement due to confusion about the EUT location in the test setup and the usage of more than one-meter length of the power supply cable are discussed and analyzed with experimental results.