How to rectify the conduction emission failure of the intelligent low-voltage monitoring unit?

Conducted emissions non-compliant, interference source identified and filtering strengthened.

Location: Use a near-field probe to scan the PCB to identify the noise source.

Corrective measures: Add a CMZ3225A-501T common-mode inductor to the power input; add RC snubber to the switching power supply MOSFET; add a PBZ1608E600Z0T ferrite bead in series for the clock signal.

PCB rectification: Check grounding continuity; add grounding to sensitive lines; place decoupling capacitors close to the IC.

Cable rectification: Use shielded cables.

After these rectifications, conducted emissions in the 150kHz-30MHz frequency band are below the limit.