How to meet the radiated immunity (RS) standards for human-machine interface (HMI) delivery?

Ensuring HMI radiated immunity meets standards requires enhancing the equipment's immunity to external electromagnetic fields. Radiated immunity issues typically manifest as display abnormalities, communication interruptions, or system crashes. Improvement measures include: enhancing the shielding effectiveness of the housing and ensuring proper handling of gaps, openings, and cable entry points—this is the first line of defense. Critical signal lines on internal circuit boards, such as reset, clock, and interrupt lines, should be grounded or routed on inner layers to reduce the possibility of inductive coupling. For sensitive chips, such as MCUs, memory, and PHY chips, local shielding can be used. Strengthen filtering at power inputs and internal power distribution networks to prevent interference from coupling into chips through power lines; for example, using ferrite beads and decoupling capacitors on the power pins of each chip.

For communication interfaces, using common-mode chokes, such as the CMZ3225A-510T, can suppress induced common-mode interference on the lines. On the software side, add redundancy checks for critical data, error recovery mechanisms, and watchdog timers. During testing, if a specific frequency failure is detected, filtering or shielding can be strengthened for that frequency. Optimizing PCB layout in the early stages of design to reduce the area of critical loops is the most cost-effective and efficient preventative measure. By using shielding materials, filter beads, and common-mode chokes from Etymotic, combined with sound design practices, HMI systems can maintain stable operation in strong radiation fields.