Comparison of conducted disturbance voltages at telecommunication ports measured using different reference ground planes in accordance with CISPR 32

To prevent radio interference due to the electromagnetic field generated by conducted disturbances at the telecommunication ports of information technology equipment, the disturbances are measured using test arrangements in accordance with standards published by the International Special Committee on Radio Interference (CISPR). We compared the conducted disturbance voltages at the telecommunication ports of two laptop PCs and one desktop PC measured using three test arrangements specified in CISPR 32. Whether the reference ground plane is vertical or horizontal is a major difference in the three test arrangements. As a result, the differences between the voltages of the laptop PCs measured using the three test arrangements were smaller than 2 dB. The differences between the voltages of the desktop PC measured using these test arrangements were about 3 dB at a few frequencies. The standard measurement instrumentation uncertainty for conducted disturbance measurement determined in the CISPR standard is 4.59 dB. Hence, the differences in voltages measured using the three test arrangements were not significant.