The reason why the shielding layer cannot be grounded repeatedly

1. There is no guarantee that there is no potential difference between the grounding points at both ends. If there is a potential difference, there will be a weak current, making the shielding layer actually become a grounding wire.
2. Shielded wires grounded at both ends are used in work sites with serious high-frequency interference. The line capacitance formed between the shielding layer and the internal signal wire will be coupled to the signal loop, seriously affecting signal misjudgment.
3. It is clear in the instructions of various speed regulators and PLCs that the shielding layer of the signal line must be grounded at one end and the grounding end should be on the side of the controller.
The shielding effect will be better if both ends of the cable are grounded, but the signal distortion will increase; the two-layer shielding should be mutually insulated and isolated shielding. If not insulated from each other, it should still be regarded as a single-layer shielding!
The reason why both ends of the outermost shield are grounded is because the introduced potential difference induces a current, thus producing a magnetic flux that reduces the strength of the source magnetic field, thereby basically canceling out the voltage induced when there is no outer shield; while one end of the innermost shield is grounded , since there is no potential difference, it is only used for general anti-static induction.