How to handle multiple circuits sharing a common ground in an electrical power measurement switch (PMS)?

PMS (Power Management System) often contains multiple functional loops (such as main power, auxiliary power, metering, communication, and switch control) that need to share a common ground. Simply connecting them directly will create common impedance coupling, causing noise from one loop to interfere with others. The core of correctly handling multi-loop common ground is "partitioned single-point interconnection." First, based on current magnitude and noise characteristics, the ground is divided into power ground (PGND), digital ground (DGND), analog ground (AGND), and shield ground (SHGND). On the PCB, these ground planes are isolated using dividing lines. Then, a common ground point is selected (usually the grounding pin of the power input filter capacitor), and each region is connected to this point using a star topology. Connection components can be selected as needed: PGND and DGND can be directly connected or connected through a 0Ω resistor; a CMZ2012A-900T common-mode inductor (90μH) is used between DGND and AGND; SHGND is directly connected to the chassis. Each region maintains a complete plane. In this way, the noise current of each loop flows only within its own region, minimizing coupling through the common point. This process can reduce the interference of digital noise on analog circuits by more than 30 dB.