Electrostatic shielding: Electrostatic shielding is to use copper or aluminum and other metals with good conductivity as a material to make an all-metal enclosed shell, and connect it to the ground wire, and put the encoder circuit that needs to be shielded in it, so that the power field of the external interference electric field is not Affect its internal circuit. Conversely, the power line generated by the internal circuit of the 485Modbus absolute encoder cannot escape to affect the external circuit. Electrostatic shielding can not only prevent electrostatic interference, but also prevent the interference of alternating electric fields. Therefore, the housings of many instruments are made of conductive materials and grounded.
The metal shielding layer of the shell should be as free of metal screws with sharp corners as possible. The sharp corners of the metal conductor become an interference absorbing antenna due to the "tip electric field distortion effect". The servo encoder shell uses screwless packaging technology to ensure the shielding effect of the metal shielding layer.
Low-frequency magnetic shielding: Low-frequency magnetic shielding is an effective measure to isolate the coupling interference of low-frequency magnetic fields and fixed magnetic fields. There is a magnetic field around any wire or coil that passes current, and there is a magnetic field objectively, which may cause magnetic coupling interference to the signal line of the detection instrument or the instrument. In order to prevent magnetic field coupling interference, high-permeability materials must be used as the shielding layer or absorber to allow low-frequency interference magnetic lines of force to pass through the magnetic shielding layer with small magnetic resistance, so that the circuits inside the low-frequency magnetic shielding layer are free from low-frequency magnetic field coupling interference. Impact. For example, the iron shell of the instrument acts as a low-frequency magnetic shield. If the shell is further grounded, it will also act as an electrostatic shield.
For a magnetoelectric encoder, a ferromagnetic absorbing material is designed around the magnetic source inside the encoder to absorb the changing energy of the external magnetic field and shield its interference with the magnetic source of the magnetoelectric encoder.
Electromagnetic shielding: Electromagnetic shielding also uses good conductive metal materials to make shields, shielding boxes and other different shapes, which enclose the protected circuit. The interference object it shields is not an electric field, but a high-frequency (above 40KHz) magnetic field. When the high-frequency magnetic field generated by the interference source encounters the electromagnetic shielding layer with good conductivity, the eddy current of the same frequency is induced on its outer surface, which consumes the energy of high-frequency interference, thereby protecting the circuit inside the electromagnetic shielding layer from high frequency. The influence of frequency interference magnetic field.
It is not only the protection of the internal circuit of the servo encoder, the signal transmission cable of the encoder output signal selects the twisted-pair shielded cable dedicated to the encoder signal. The cable shielding layer has ultra-fine high-density metal wires woven into a protective layer. Absorb the high-frequency electromagnetic field changes of external radiation, thereby playing the role of shielding and protection.
For example, the nature of radio broadcasting is electromagnetic waves, so electromagnetic shielding can also absorb their energy. This is why we cannot receive radio in a car (steel body, but not grounded), and we must pull out the antenna of the radio. The reason outside the car.
If the electromagnetic shielding layer is grounded, it can also have an electrostatic shielding effect, and the shielding effect on electromagnetic waves will be better. The copper mesh shielded cable usually used as a transmission line can play the role of electromagnetic shielding and electrostatic shielding at the same time when it is grounded.
Reduce the "sharp corners" of the terminal for signal transmission, and try to connect a cable directly to the receiving end. The receiving terminal in the middle of the signal transmission is an exposed interference absorption "antenna" unit, especially the wire ends and metal sharp corners, which seem to be extended antennas, and should be avoided during signal transmission.