How should the power ground and signal ground of an electrical power measurement switch (PMS) be separated?

In a power supply system (PSS), improper handling of the power ground (PGND, which carries large currents, such as in switching power supplies and relay drives) and signal ground (SGND/AGND, used for measurement and communication) can lead to noise on the power ground contaminating the signal ground and causing system instability. Proper splitting and single-point connection are crucial. First, on the PCB layout, separate the PGND and SGND/AGND areas using ground plane split lines or physical slots, with a split spacing of at least 2mm. Analog signal ground (AGND) should be further separated from digital signal ground (DGND).

Then, connect these ground planes at a single point, typically near the ground pin of the filter capacitor at the power input or near the AGND pin of the ADC. The connection can be achieved using a 0Ω resistor, ferrite bead, or a small inductor, such as a CMZ2012A-900T (90μH) to connect AGND and DGND, providing high-frequency isolation. All signal lines crossing the split gap must have a continuous reference plane underneath (usually an unsplit intermediate layer) or a bridging capacitor (e.g., 100pF) to provide a high-frequency return path. By properly segmenting and connecting individual points, the interference of power ground noise on the 16-bit ADC reference can be reduced by more than 40dB, ensuring measurement accuracy.