Follow the complete current loop
Every signal or power current has a return path. The distribution of that current depends on the impedance of the available paths and the frequency content of the signal. A net labeled ground is not an ideal zero-impedance surface everywhere on the product.
Review the source, load and return conductor as a connected system. Fast signal returns interact with nearby reference geometry, while shared paths can couple disturbances into sensitive circuits. Use placement to make intended current paths practical before relying on routing fixes.
Review references and transitions
Inspect plane voids, slots and layer changes near critical routes. If a signal changes reference, determine how the return current transfers between those references. A copper island with the right net name may still provide an unsuitable path.
Mixed-signal labels such as AGND and DGND do not create a universal instruction to split the board. Follow the exact device guidance and examine the complete current flow. A partition or connection suitable for one converter arrangement may not suit a multi-board system.
Distinguish signal ground, chassis and protective earth
Signal reference, cable shield, chassis bonding and protective earth have different purposes even when the product connects them at defined points. Document those connections and their mechanical implementation. Do not remove a required protective connection as a noise-reduction experiment.
Multiple connections between equipment can create loops that carry unwanted current and disturb a measurement or signal. Review the cable paths, shielding, interface isolation and measurement setup. There is no single ground-loop accessory that is automatically appropriate for every interface.
Verify the implemented system
Review return paths with the assembled enclosure, cables, power source and operating modes. Bench wiring can change the behavior compared with the final installation. Use measurement methods appropriate to the circuit and its electrical conditions.
Keep grounding decisions, interface drawings and relevant test evidence in the release package. If a connector, cable shield, enclosure or board partition changes, revisit the affected paths. Successful continuity between two ground points does not establish low impedance across the entire operating spectrum.