How to ensure EMC for data acquisition from dry contacts of power DTUs?

To ensure EMC performance of DTU dry contact data acquisition, jitter and noise interference must be prevented. A 1kΩ series resistor is used for current limiting in the dry contact input circuit, and a TVS diode SMBJ6.0CA is connected in parallel to absorb transients. Optical isolation (such as TLP281) is used, with an isolation voltage of 3000Vrms. On the PCB layout, the dry contact circuit is kept away from high-frequency circuits. In software, a de-jitter algorithm (such as multiple sampling) is added. Testing must meet IEC61000-4-2 ESD ±8kV and IEC61000-4-4 EFT ±4kV. After ensuring EMC performance, dry contact acquisition should operate without errors and be suitable for condition monitoring.