Measurement of Conducted Interference Voltage/Current at Power Supply Terminals
When measuring on the radiation test field, the EUT should be in the same state as the radiation measurement, and the EUT should be placed on a metal grounding plate that extends at least 0.5m beyond its boundary or has a small size of 2m × 2m.
When measuring in a shielded room, the ground shielding layer or any shielding layer on one wall can be used as a grounding plate. During the experiment, the non ground mounted EUT should be placed on an insulated bracket or platform 0.4m above the ground. The landing EUT should be placed on a grounding plate, and its contact points should be insulated from each other or consistent with normal use. The distance between all EUTs and other metal objects should be greater than 0.8m.
The close distance between the outer surface of LISN and the EUT boundary should be less than 0.8m. The reference grounding terminal of the network should be connected to the grounding plate with as thick and short a wire as possible. The relevant situation between the wiring of power cables, signal cables, and grounding plates should be equivalent to the actual usage situation, and the cables should be arranged very carefully to avoid false response effects. Figure 3 shows a typical arrangement for measuring conducted interference in a shielded room.
When the EUT has a special grounding terminal, the shortest possible wire should be used for grounding. EUTs without special grounding terminals should be tested in their normal connection mode, i.e. grounded from the power grid. For equipment with flexible power cords provided by the manufacturer, the length of the power cord should be 1m. If the actual length exceeds 1m, the excess part should be folded back and forth into a wire harness of 0.3-0.4m.
If the EUT consists of several units and each unit has a power cord, when connected to the LISN, it depends on the following regulations:
① Each power cable connected to a standard power plug should be measured separately;
② The manufacturer has not specified that power lines or terminals that require power supply from another unit in the system should be measured separately;
③ According to the manufacturer's regulations, the power cord or terminal required to obtain power from a certain unit in the system should be connected to that unit, and the cable or terminal of that unit should be connected to LISN for measurement;
④ When EUT needs to be grounded for its purpose, the grounding wire should be connected to the reference grounding point of LISN. Unless otherwise specified by the manufacturer, the length of the grounding wire should be 1m and laid parallel to the EUT power line, with a spacing of no more than 0.1m, unless otherwise specified.
