1. Electrostatic shielding
Electrostatic shielding refers to making a closed metal container from a metal with good conductivity such as copper or aluminum and connecting it to the ground wire to shield it. The circuit is placed inside it so that the electric field that interferes with the external electric field does not affect its internal circuit. On the contrary, the power lines generated by the internal circuit cannot affect the external circuit. Small holes are allowed on the walls of electrostatically shielded containers, which will have little impact on the shielding.
It should be noted that if the instrument and equipment adopt this shielding technology, the shielding shell must be grounded.
2. Low-frequency magnetic shielding
Low-frequency magnetic shielding is used to isolate low-frequency (mainly below 50zH) magnetic fields and fixed magnetic fields (also called static magnetic fields, whose amplitude and direction do not change with time) , such as the magnetic field generated by permanent magnets) effective measures for coupling interference, electrostatic shielding wires or electrostatic shielding boxes do not isolate low-frequency magnetic fields. High-conductivity porcelain materials must be used as the shielding layer so that low-frequency interference magnetic field lines can only pass through the magnetic shielding layer with very small magnetic resistance, so that the circuits inside the low-frequency magnetic shielding layer are protected from low-frequency magnetic field coupling interference. Sometimes the shielded wire is also threaded into a grounded iron snakeskin pipe or ordinary iron pipe to achieve the purpose of low-frequency shielding of the electrostatic shielding box.
3. Electromagnetic shielding
Electromagnetic shielding uses metal materials with good conductivity to make shielding covers, shielding boxes and other different shapes to surround the protected circuit. The interference object it shields is high-frequency (above 40kHz) magnetic fields. When the high-frequency magnetic field generated by the interference source encounters a well-conducting electromagnetic shielding layer, an eddy current of the same frequency is induced on its outer surface, thereby consuming the energy of the high-frequency interference source magnetic field. Secondly, the eddy current will also generate a new magnetic field, which offsets part of the energy of the interference magnetic field, thereby protecting the circuit inside the electromagnetic shielding layer from the influence of the high-frequency interference magnetic field.