How to minimize the grounding impedance of the power measurement switch (PMS)?

The impedance of the PMS grounding system directly affects the discharge capability of high-frequency noise and the stability of ground potential. Excessive impedance can lead to filter failure and reduced shielding effectiveness. Minimizing grounding impedance requires addressing the grounding conductor, connection points, and frequency characteristics.

First, the grounding conductor should be a flat conductor with a large surface area (such as copper busbars or braided tape), rather than a round wire, to reduce the skin effect at high frequencies. The length should be as short as possible, as inductance is proportional to length. Second, all connection points (such as chassis seams and grounding screws) should ensure direct metal-to-metal contact, removing paint or oxide layers, and using toothed locking washers or conductive paste to reduce contact resistance.

For the PCB, the ground plane should be complete and thick (2oz copper thickness recommended), and extensive use of grounding vias (spacing <λ/20) should be used to connect multiple ground planes. At the system level, star grounding or grid grounding should be used to avoid ground loops. Measured with an impedance analyzer, the impedance from the PMS's internal critical circuit ground to the chassis ground terminal should be less than 100mΩ at 10MHz. Low-impedance grounding ensures rapid discharge of surge current and ESD charge, protecting core circuitry.