How to ground the analog shield of the I/O module?

Properly grounding the shielding layer of I/O module analog signals is crucial to preventing interference coupling. The basic principle is that the shielding layer should be grounded at a single point on the signal receiving end. For differential analog signals, the shielding layer should be connected to the instrumentation amplifier's reference ground or a clean analog ground on the receiving end. If the signal source is also grounded, a ground loop may form. In this case, it's best to float the shielding layer at the signal source end and ground it only on the receiving end; or use an isolation amplifier to disconnect the direct ground connection. On the PCB, when the shielding layer is accessed through the connector's metal housing or a dedicated shielding clip, this access point should be connected to the module's analog ground plane via a low-impedance path, avoiding the introduction of impedance through long traces. For multi-core shielded cables, each twisted pair can have its own shielding layer. These sub-shields should be insulated from the overall shielding layer and connected at only one point. In high-frequency applications, it may be necessary to ground both ends of the shielding layer to maintain high-frequency shielding effectiveness, but ferrite cores should be installed on the cable to suppress any resulting ground loop currents. After design, the signal quality under different shielding grounding methods should be tested under applied interference to determine the optimal solution.