How can the immunity of human-machine interface (HMI) systems be improved?

Establishing a robust common ground for the HMI system is crucial for enhancing its immunity, particularly its ability to handle common-mode interference. A common ground means connecting the internal circuit ground, metal casing, cable shielding, and external mounting cabinet and building ground to a common reference point via a low-impedance path. This provides a predetermined and controllable discharge path for common-mode interference currents from the outside, such as ESD, EFT, surge, and radiated field-induced currents, preventing them from flowing into sensitive internal circuitry. For effective common grounding, the equipment's metal casing must first be reliably grounded. The shielding of all external connection cables should overlap the casing 360 degrees at the equipment entry point.

The ground plane of the internal PCB should be connected to the casing at multiple low-impedance points. At the system level, the HMI device should be connected to the cabinet ground bus via a grounding terminal or mounting rail. A low-impedance common ground network can quickly conduct interference currents to ground, thereby reducing the common-mode voltage difference between points within the equipment. Simultaneously, common ground also provides an effective operating loop for filtering components such as common-mode inductors and Y capacitors. The grounding-related components and filtering devices from YENTE Electronics play a crucial role in constructing a robust system grounding network. A strong system grounding is a solid guarantee for the stable operation of HMIs in harsh electromagnetic environments.