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Electromagnetic Interference and Electromagnetic Shielding

1.What is Electromagnetic Interference (EMI)?
2.What is electromagnetic shielding?
3.Effects of Electromagnetic Interference on Biological Human Body
4.Electromagnetic detection methods in daily life
5.EMI shielding effectiveness
6.How to reduce EMI interference
7. Magnetic field interference
8.Conductive cloth plays an important role in electromagnetic shielding

 

Electromagnetic Interference (EMI) refers to the interference generated by an electromagnetic field that can have a detrimental impact on other equipment. This phenomenon is caused by the generation of fluctuating magnetic fields when current flows through a conductor, which is directly related to the amount of power dissipated. Power consumers, such as motors and transformers, are known to generate significant fluctuating magnetic fields due to their electromagnetic fields that switch at high frequency to keep them running. This makes them an ideal source of disturbances that can adversely affect other equipment. Interference occurs when fluctuating magnetic fields pass through other devices or their connecting cables or PCB traces, generating small voltages that can easily corrupt input and output data signals in data processing equipment that operates at low voltages. Therefore, it is imperative to take measures to reduce the effects of electromagnetic interference.

EMI
EMI

What is Electromagnetic Shielding?

 

Electromagnetic Shielding, also known as EM Shielding, refers to a protective barrier constructed from conductive materials that envelops a device to safeguard it from electromagnetic interference in the surrounding environment. Alternatively, it can also be utilized to prevent the device’s own electromagnetic emissions from interfering with other devices in the same environment. Electromagnetic shielding serves as a form of insulation that reduces or prevents energy transfer. The presence of electromagnetic energy is inevitable between high output equipment and the environment, or between sensitive equipment and electromagnetic fields in the environment. Given the inherently unpredictable nature of electromagnetic conditions in the environment, the purpose of shielding is to eliminate this performance threat.

The Effects of Electromagnetic Interference on the Human Body

 

There exists a widespread confusion and misinformation regarding the electromagnetic environment that surrounds us. Critical information that is readily available in technological circles remains largely unknown to the general public. This can be attributed to several factors that mutually reinforce each other. One such factor is the strong bias that many biologists hold against the geophysical pacemaker of biological rhythms. This bias stems from the fear that such evidence may be seen as support for astrology, which is widely considered scientifically unfounded (although Seymour, 1988, provides a counterargument). Another factor is the threat to the ego, as our lives may be affected by events that are far removed from us. The notion that the human body both radiates and is sensitive to invisible energy fields can be dangerous to some. Finally, documenting the health effects of magnetic fields generated by electrical distribution systems and technical equipment has enormous economic and legal consequences. It is therefore imperative that people be educated about the possible health effects of the invisible electromagnetic environment so that appropriate precautions can be taken.

 

These considerations are becoming increasingly important for various reasons, as discussed herein. Furthermore, research into the possible physiological effects of environmental fields is more extensive than many realize. Virtually every disease and disorder has been linked to electromagnetic pollution by one researcher or another. For instance, Sobel and colleagues have noted that individuals who work in areas exposed to strong electromagnetic fields have a higher risk of developing Alzheimer’s disease.

 

Preliminary clinical trials using devices that shield against electromagnetic pollution have shown relief in several symptoms, suggesting that these problems may, in fact, be caused or exacerbated by electromagnetic pollution. Whether these correlations hold up to long-term studies is unclear, but there is enough information about electromagnetic biological effects that the U.S. government warns that until more information is known, it is good policy to avoid it carefully. Currently, the “safe limits” for EMF exposure are unknown. Interestingly, Russia’s maximum safe microwave exposure levels to avoid changes in brain activity are 1,000 times lower than the US legal maximum.

EMI
EMI

The impact of electromagnetic interference on the biological body is mainly reflected in the following three aspects:

 

Thermal effect: The impact of electromagnetic waves on the human body is firstly the thermal effect. Under the action of high-frequency electromagnetic fields, the temperature of objects will increase, and the increase in body temperature may affect the temperature around the organs in the body, thereby affecting the normal function of the organs.

Stimulation: When the frequency of electromagnetic waves is below 100 Hz, it will stimulate the human body. For example, people have found that if a large number of negative ions are “swallowed” by the electromagnetic fields generated by electrical appliances, motors and other equipment during operation, there are usually more positive ions than negative ions, which will have an impact on human health.

Non-thermal effect: Electromagnetic radiation can interfere with the weak electromagnetic field existing in human organs and tissues. Although the body will not heat up obviously, it may affect the health of the body.

In addition, a strong magnetic field will destroy the inherent current and magnetic field of the human body, affect the ecological balance of the human body, and cause dysfunction of the nervous system and cardiovascular system. Therefore, in daily life, people should pay attention to guard against the influence of electromagnetic radiation and avoid prolonged exposure to strong electromagnetic fields.

 

Electromagnetic detection methods in daily life

Low-cost magnetic field detectors are now available, and these devices are invaluable to those looking to better understand magnetic fields in homes and workplaces. One such device (the TriField from AlphaLab) is fairly inexpensive and combines magnetic, electrical, and radio/microwave detectors. It is important that the magnetic part has three detection coils facing in three directions in space. These devices allow people to locate “hot spots” in the home and work environment, such as near electric blankets and heaters, fluorescent lights, dimmers, poorly sealed microwave ovens, cell phones, computers, televisions, transformers and motors near refrigerators and clocks etc. equipment. Sometimes moving furniture, cribs, or beds short distances can significantly reduce long-term exposure.

 

Some people have taken steps to rewire homes and workplaces to reduce the levels of 50 or 60 Hz magnetic fields. A simple change in wiring configuration can make a huge difference in the magnetic field levels in a home (Maxey, 1991). However, Abraham, personal communication (1998) warns that any method of field cancellation, such as twisting conductors together, may result in the generation of undetectable 50 or 60 Hz scalar waves, which may also have serious health effects. Clearly, we still have a lot to learn about the electromagnetic environment and its relationship to therapy.

Electromagnetic Detection Methods in Daily Life

Structure diagram (4)
Structure diagram

Inexpensive magnetic field detectors have become readily available, providing invaluable assistance to those seeking to gain a better understanding of magnetic fields in both residential and occupational settings. The TriField device, developed by AlphaLab, is a prime example of such a tool, combining magnetic, electrical, and radio/microwave detectors at a reasonable cost. It is noteworthy that the magnetic component of this device features three detection coils oriented in three distinct spatial directions. These detectors enable individuals to identify “hot spots” in their living and working environments, such as those near electric blankets and heaters, fluorescent lights, dimmers, poorly sealed microwave ovens, cell phones, computers, televisions, transformers, motors, refrigerators, and clocks. In some cases, simply relocating furniture, cribs, or beds a short distance can significantly reduce long-term exposure.

 

Certain individuals have taken measures to rewire their homes and workplaces in order to decrease the levels of 50 or 60 Hz magnetic fields. A minor alteration in wiring configuration can have a significant impact on magnetic field levels within a home (Maxey, 1991). However, Abraham (1998), in personal communication, cautions that any method of field cancellation, such as twisting conductors together, may result in the generation of undetectable 50 or 60 Hz scalar waves, which may also have serious health effects. Clearly, much remains to be learned about the electromagnetic environment and its relationship to therapy.

 

The effectiveness of electromagnetic interference (EMI) shielding is dependent on the use of conductive materials to form a barrier. However, the enclosure must fully encompass the device, which often requires division into at least two parts to allow for access. It is crucial that there is conductive continuity between these parts to prevent interference from “leaking” through any gaps. Achieving continuous face-to-face contact between the housing and its cover with the necessary precision is not always reliable, particularly when considering environmental hazards such as dust and water. Therefore, flexible seals are necessary, with rubber being a common choice. However, as rubber is transparent to EMI, it must be encapsulated in a knitted wire sleeve to ensure contact between the two components. In some cases, devices require air cooling while still retaining the shield. However, any holes or slots in the shield will act as an antenna and allow EMI to re-radiate within the enclosure. To maintain effective shielding, any holes or slots should be smaller than 3mm. The CP Cases ERack Lightweight 19-Inch Reinforced Case serves as a practical example of this technology.

A guide on mitigating EMI interference

 

The most widely recognized method of EMI shielding is the implementation of a “Faraday cage”. This entails the use of a conductive enclosure that prevents voltage from entering, as the charges repel each other on the sides. The size of the aperture in the cage determines which voltages will be excluded. In the realm of electronics, any openings must be small, but need not be completely sealed.

 

CP has manufactured communication cabinets for the Royal Navy’s new aircraft carriers. However, the challenge lies in the requirement for multiple cable entries, and the need for a streamlined process for cable installation or replacement. To comply with EMI protection standards, it is recommended to design custom flexible conductive multi-cable entry ports. To ensure optimal contact continuity on flexible seals, it is crucial to compress them evenly. CP offers butterfly and toggle latches for this purpose, and is currently developing additional latching solutions.

In electrical engineering, electromagnetic shielding is the practice of reducing or blocking electromagnetic fields (EMF) in a space by means of barriers made of conductive or magnetic materials. It is commonly applied to enclosures to isolate electrical equipment from its surrounding environment, and to cables to isolate the wires from the environment in which the cable operates (see Shielded Cables). Electromagnetic shielding that blocks radio frequency (RF) electromagnetic radiation is also known as RF shielding.

 

EMF shielding minimizes electromagnetic interference. Shielding reduces the coupling of radio waves, electromagnetic fields, and electrostatic fields. A conductive enclosure used to block electrostatic fields is also known as a Faraday cage. The amount of reduction depends largely on the material used, its thickness, the size of the shielded volume and the frequency of the field of interest, and the size, shape and orientation of the holes in the shield for the incident electromagnetic field.

HGP conductive sponge
HGP conductive sponge

There are several reasons for electromagnetic shielding. The most common purpose is to prevent electromagnetic interference (EMI) from affecting sensitive electronic equipment. Metal grilles are often used to protect one component from affecting another within a particular piece of equipment. For example, in smartphones, metal shields protect electronics from cellular transmitters/receivers. Radiation shielding in mobile phones also reduces the potential exposure of radio frequency (RF) energy to the user.

 

To increase the safety of air-gapped systems, electromagnetic shielding is recommended. Physical isolation and lack of external connectivity have traditionally been considered sufficient to keep it secure. However, the proof-of-concept attack shows that acoustic infection can be achieved by exploiting the electromagnetic radiation of the system’s sound card.

 

Air gaps are used in military, government and financial systems such as stock exchanges. The measures are also used by journalists, activists and human rights groups who deal with sensitive information.

 

Many different materials and techniques are used for electromagnetic shielding. The wires may be surrounded by foil or braided shielding to block false EMI from the jacketed wires. Audio speakers typically have an inner metal casing to block electromagnetic interference from the drivers so they don’t affect TVs and other electronics. A completely continuous enclosure is not required as long as any opening is smaller than the electromagnetic waves that need to be blocked.

 

Special conductive paints can be used to prevent electromagnetic fields in the network from escaping the original traffic to prevent eavesdropping or wireless attacks. These technologies act like miniature Faraday cages that prevent signal corruption that could cause electronics to operate unintentionally.

 

Electronics can also minimize the effects of EMI noise by using electronic components such as capacitors, ferrules, and ground wires to filter EMI connections—even twisting the wires together with ground can reduce interference at lower levels.

 

In environments where the magnetic field changes slowly below the 100Khz range, electromagnetic shielding with magnetic materials must be used as Faraday cage solutions are not effective in this case. For magnetic materials, EMI is induced into the shielded magnetic field.

magnetic field interference

There are many ways to interrupt the magnetic field. One of the most common techniques is the use of pressurized bags. Anti-theft bags are other items (jacket liners, umbrellas, etc.) lined with layers of aluminum foil to provide electromagnetic shielding and prevent security tags from being detected. Some retailers use detectors that sense metal surfaces to prevent the use of pressurized bags.

 

Criminals use many types of EMF disruptors. The two most common types of disruptors are preventing the alarm from going off or triggering the alarm, causing the EAS to lose credibility and be turned off or ignored by store personnel. Another popular method used by criminals is to use magnets to remove tags from items, either to prevent alarms from going off, or to simply demagnetize tags. However, there are many loss-prevention devices that can detect magnets and jammers.

Conductive cloth plays an important role in electromagnetic shielding.

Conductive cloth is a material made of polyester fiber and metal plating, which has good electrical conductivity and electromagnetic shielding effectiveness.

The shielding principle of conductive cloth is mainly realized by suppressing the propagation of electromagnetic waves. When the electromagnetic wave meets the conductive cloth, part of the electromagnetic wave will pass through the cloth layer, and the other part will be absorbed and reflected by the cloth layer. Especially the metal coating, which can effectively reflect electromagnetic waves, thereby reducing the propagation of electromagnetic radiation.

Conductive cloth is widely used in electromagnetic shielding, anti-static, grounding and other fields, such as smart phones, wearable devices, LCD, automated high-frequency equipment, medical equipment and other electronic products, as well as military, aerospace and other fields.

The conductive cloth produced by us has good electromagnetic shielding performance and has been applied to a wide range of electromagnetic shielding fields.

 

 

 

 

 

 

 

Picture of Lu

Lu

Our materials research team from Tsinghua University postdoctoral researcher lin and Harbin Institute of Technology researcher Mu, Nanjing University of Technology researcher Wei, they share their expertise in foam metal materials article.

About HGP

WE were established in 2003, located in the Gaoxin Zone of Guangdong-Guangxi Cooperation Special Experimental Zone, covering an area of 70 mu, with a plant of about 30,000 square meters, with more than 170 employees, is an advanced new material technology enterprise integrating research and development, production and sales.

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