How can a PMS (Power Measurement System) for measuring weak electrical quantities resist strong electrical interference?

In a power supply system (PMS), low-voltage signals at the microamp/millivolt level are easily submerged or distorted under high-voltage (hundreds of volts, tens of amps) conditions, making anti-interference design crucial for success. The core strategy is "isolation, shielding, filtering, and differential transmission."

Isolation: Use isolation amplifiers (such as the ADuM4190) or isolated ADCs to cut off the conduction path.

Shielding: Place the low-voltage measurement circuitry in an independent metal shielded box with proper grounding; use double-shielded sampling lines, with the inner shield connected to signal ground and the outer shield connected to chassis ground.

Filtering: Implement multi-stage filtering before the signal enters the amplifier, including a common-mode inductor CMZ2012A-900T, an RC low-pass filter (cutoff frequency slightly higher than the signal bandwidth), and software digital filtering.

Differential Transmission: Use differential signal transmission exclusively, and select instrumentation amplifiers with high CMRR (>100dB).

PCB Design: Completely cover the low-voltage area with a ground plane and surround it with a guard ring.

Power Supply: Provide independent, clean, linear power to the low-voltage circuitry.

Through system-level design, the low-voltage measurement system can operate stably at a distance of 10cm from the high-voltage cable, with a signal-to-noise ratio greater than 60dB and an immunity that meets the severity level of IEC 61000-4 series.