Everyone knows that electronic equipment is susceptible to electromagnetic interference when it is used normally. Similarly, electronic instrumentation is no exception. Due to the interference of electromagnetic waves, the measurement accuracy of electronic instruments may not be so accurate, then electronic instruments How does the meter suppress electromagnetic interference?
There are three main methods of suppressing electromagnetic interference: shielding, filtering, and grounding.
1, shielding
Shielding is a measure used to reduce the electromagnetic field's outward or inward penetration and is commonly used to isolate and attenuate radiated interference. According to its principle, shielding is divided into three types: electrostatic shielding, electromagnetic shielding and magnetic shielding. The role of electrostatic shielding is to eliminate the electromagnetic interference between the two circuits due to the distributed capacitive coupling. The shielding body is made of low-resistance metal material, and the shielding body must be grounded. The function of the electromagnetic shielding is to prevent the interference of the high-frequency electromagnetic field. The shielding body is made of a low-resistance metal material, and the shielding metal is used to absorb and reflect the electromagnetic field to achieve the purpose of shielding. The function of the magnetic shielding is to prevent the interference of the low-frequency magnetic field. The shielding body uses a magnetic material with high magnetic permeability and high saturation to absorb or lose the electromagnetic field to achieve the purpose of shielding.
The influence of electromagnetic interference is closely related to the distance. The closer to the interference source, the greater the interference field strength and the greater the impact. In electronic instrumentation, the arrangement of electronic components is often limited by volume. The low-resistance metal material or magnetic material is often used to form an enclosure, and the components or parts with insufficient protection spacing are isolated to reduce or prevent static or electromagnetic interference.
2, filtering
Filtering can suppress electromagnetic conduction interference. Sensitive electronic devices conduct electromagnetic interference signals through power lines, telephone lines, control lines, signal lines, and the like. For conducted interference, low-pass filter filtering is often used to achieve effective suppression. However, in the electromagnetic compatibility design, the characteristics of the filter must be considered: frequency characteristics, impedance characteristics, rated voltage and voltage loss, rated current, leakage current, insulation resistance, temperature, reliability, and dimensions.
3, grounding
In a device or device, the grounding is to cause the interference current generated by the device or the device itself to flow into the earth through the grounding wire, and is generally used for suppressing conducted interference. The ideal grounding body is a zero-potential, zero-impedance physical entity that serves as a reference point for all signal levels in the relevant circuits, and no unwanted current passes through it to produce a voltage drop. This ideal grounded entity is actually approximate.
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