How to suppress interference from the operation of the PMS (Power Measurement System) switch?

When the PMS switch opens and closes, the arc generated between the contacts and the parasitic parameters of the circuit can cause high-frequency oscillations (up to MHz), forming strong conducted interference and near-field radiation, interfering with the normal operation of the measurement module and communication circuits. The solution needs to start with source suppression and path filtering. First, connect an RC absorption circuit in parallel at the switch contacts, for example, using a 1nF safety capacitor in series with a 10Ω resistor, which can effectively dampen oscillations and reduce dV/dt. Second, deploy two stages of filtering at the power input. The first stage uses a CMZ1211-501T series common-mode inductor (500μH) to filter out common-mode noise, and the second stage uses a PBZ1608E600Z0T ferrite bead (60Ω@100MHz) to attenuate high-frequency differential-mode components. Simultaneously, optimize the PCB layout of the switch drive lines and power lines to ensure minimal loop area and distance from sensitive measurement circuits. By taking the above measures, the peak disturbance voltage generated by the switching action can be reduced by more than 30dB, ensuring that the system can pass the IEC 61000-4-4 Electrical Fast Transient Burst (EFT) immunity test.