When a shielded cable is used, the shielding layer should be equipotentially connected at least at both ends. When the system requires equipotential bonding only at one end, two layers of shielding should be used, and the outer shielding should be handled according to the above requirements.
The principle is: 1. One end of the single-layer shield is grounded, and no potential difference is formed. It is generally used for anti-static induction. 2. Double-layer shielding, both ends of the outermost shield are grounded, and one end of the inner shield is grounded with equipotential grounding. At this point, the outer shield induces a current due to the potential difference, thus generating a magnetic flux that reduces the strength of the source magnetic field, thereby substantially canceling the voltage induced without the outer shield.
If it is to prevent electrostatic interference, it must be grounded at a single point, whether it is a one-layer or two-layer shielding. Because single-point grounding has the fastest rate of electrostatic discharge.