How can a single-point grounding of a Human-Machine Delivery (HMI) meet EMC requirements?

Implementing single-point grounding in an HMI system to meet EMC requirements requires clarifying its applicable scenarios and paying attention to high-frequency limitations. Single-point grounding is suitable for low-frequency analog circuits, audio circuits, or parts particularly sensitive to ground loop interference. Its core principle is that all circuit ground wires ultimately converge to a single grounding point, typically located at the power supply grounding terminal or the interface grounding terminal. This avoids mutual coupling of ground currents between different circuits. To meet EMC requirements, it is essential to ensure that this single grounding point itself has low impedance and a good connection to the system chassis or earth to provide a discharge path for interference currents.

For unavoidable high-frequency digital circuits within the system, long-distance traces back to a single grounding point should not be forced; otherwise, the inductance of the long ground wires will cause high-frequency problems. In this case, multi-point grounding should be used locally in the high-frequency circuit area to reach a complete ground plane, and then a low-impedance wire or plane should be used to connect this ground plane to the main single grounding point. For I/O ports, their shielding or signal ground is usually connected to the chassis at the port through capacitors or ferrite beads, and the chassis itself is part of the single-point grounding system. By employing this hybrid strategy of "multiple local grounding points and single overall grounding points," and utilizing the filtering and grounding devices of Audiotech, the EMC requirements of the entire frequency band can be met while leveraging the advantages of single-point grounding.