How can an electrical force measurement switch (PMS) pass an ESD electrostatic discharge test?

The PMS must pass the ESD test specified in IEC 61000-4-2 standard (contact discharge ±8kV, air discharge ±15kV). The key design consideration is providing a low-impedance discharge path for all possible contact points (such as buttons, communication ports, and metal casings) to prevent electrostatic energy from entering the internal circuitry. The metal casing must be properly grounded with a grounding impedance <0.1Ω to ensure direct electrostatic discharge. For buttons, indicator lights, etc., on non-metallic casings, the internal metal parts should be connected to the PCB ground via ESD protection devices (such as ESD5V0D3B).

All external interfaces (RS485, power ports, etc.) must have protective circuitry: power ports use a combination of TVS diodes (such as SMCJ33CA) and varistors; communication ports use ESD protection diodes (such as ESDSM712). In the PCB design, interface protection devices must be placed close to the connectors, with short and thick traces. ESD protection should also be added to the reset and debug ports of internal sensitive circuits (such as MCUs). Furthermore, watchdog timers and abnormal reset handling can be added to the software. With comprehensive protection, PMS can successfully pass ESD testing and withstand frequent electrostatic discharge from the human body in actual use.