The problem of electromagnetic radiation of electronic products is getting more and more attention, and I believe that most of them are not unfamiliar with the term EMC (electromagnetic compatibility), because to obtain China’s 3C certification, they must pass the EMC test of professional institutions.
However, in various media reports and product promotion, similar EMI, EMS and other professional terms often appear in front of everyone, they seem to be related to radiation (electromagnetic radiation), so people do not know. So, what are the differences and similarities between them?
EMI Attack
EMI (Electro MagneTIc Interference) is directly translated as “electromagnetic interference”, refers to the electronic equipment (interference source) through the electromagnetic waves to other electronic equipment interference phenomenon.
For example, when we watch TV, next to someone using a hair dryer or electric shaver and other household appliances, the TV screen will appear on the snow noise; rice cooker does not cook rice; off the air conditioner will start on its own …… these are common electromagnetic interference phenomenon.
More serious is that if the electromagnetic interference signal interferes with the medical electronic equipment that is monitoring the condition or the aircraft that is flying, it will cause unimaginable consequences. From these examples, it is as if the electronic equipment has an invisible “attack” on the normal operation of other electronic equipment caused by the disruption and damage.
The power supply of the first and second EMI filter circuit, is designed to reduce the power supply of electromagnetic interference and conduction.
From the “attack” on the way, EMI mainly has two types: conducted interference and radiation interference. Electromagnetic conduction interference is the source of interference through a conductive medium (such as wire) to their own electrical network on the signal coupling (interference) to another electrical network.
The most common example is the power supply in our computer will have an impact on the electrical network at home, the computer is turned on at the same time the lights at home may become dim, which is more obvious in the use of miscellaneous inferior power supply computer performance.
The internal structure of today’s power supplies, one or two EMI filtering circuit is essential, where the “EMI” is aimed at electromagnetic interference, to prevent the power supply work on the outside world has too much impact.
EMI contacts on the chassis, is designed to reduce the shielding of electromagnetic radiation interference inside the chassis.
Electromagnetic radiation interference is often referred to as electromagnetic radiation, it refers to the source of interference through space on their own electrical network signal coupling (interference) to another electrical network, like the martial arts novels, “playing things across the air”.
Because the human life activity contains a series of bioelectric activity, these bioelectricity is very sensitive to the environment of electromagnetic waves, so excessive electromagnetic radiation can cause impact and damage to the human body.
People often worry about “radiation” is also referred to this part of electromagnetic radiation interference. Application of the chassis on a variety of radiation protection design, such as EMI shrapnel, EMI contacts, here “EMI” for electromagnetic radiation interference, to reduce the amount of electromagnetic waves propagated to the outside of the chassis.
EMS defense
There is a spear there is a shield, there is electromagnetic interference on the anti-electromagnetic interference. Here comes our second protagonist EMS.
EMS (Electro MagneTIc SuscepTIbility) is directly translated as “electromagnetic sensitivity”, which refers to the degree of ease with which electronic equipment is subjected to external electromagnetic energy, causing its own performance degradation.
For example, the same by the hair dryer or electric razor interference, some TV screens appear on the snow noise, some TVs are safe.
This shows that in the case of electromagnetic interference “attack”, the former’s electromagnetic sensitivity is higher, more easily injured, that is, “defense” is lower; and the latter’s electromagnetic sensitivity is lower, not easily injured, that is, “defense “higher.
TV screen snow serious, interference by other electronic devices is a major factor.
EMC comprehensive offensive and defensive capabilities
With a spear, also has a shield, and finally use them both together to arm our third protagonist EMC.
EMC test using electromagnetic compatibility laboratory, electromagnetic radiation interference test can be conducted.
EMC (Electro MagneTIc Compatibility) is directly translated as “electromagnetic compatibility”, which refers to the ability of electromagnetic energy generated by electronic devices to neither interfere with other electronic devices nor be interfered by the electromagnetic energy of other electronic devices.
Therefore, EMC includes the requirements of both EMI and EMS: on the one hand, it requires that the electromagnetic interference generated by the electronic equipment to the environment during normal operation cannot exceed a certain limit, i.e. EMI; on the other hand, it requires that the electronic equipment has a certain degree of anti-interference ability to the electromagnetic interference existing in the environment, i.e. EMS.
Specifically in the EMC testing of electronic equipment, the relevant standards specify the maximum value of EMI, as well as the minimum value of EMS, as if to limit the “attack power” at a lower level, the requirements of the “defense” at a higher level.
This is also very understandable, like we have a guard dog, you do not want it to run out of the door to bite people, but you require it to carry the enemy when they come.
Now we know that a good electronic device should be a “low attack high defense” role, both to the outside world generated by the interference of small, but also good resistance to interference from the outside world.
So how to buy such products? In fact, national regulations have been prepared for us. Since 1996, the European Community has made provisions for its unified market: any electrical and electronic equipment without the “CE” certification mark shall not enter the European Community market.
Our government has also made provisions since August 1, 2003, any electrical and electronic equipment without the “CCC” (i.e. 3C) certification mark shall not enter the Chinese market. The CE certification and 3C certification both include the requirements of EMC.
Therefore, when you buy electronic products, just look at its shell or packaging has no “CE” and “CCC” mark, you can know whether it has the national regulations of low interference (including low radiation), high anti-interference characteristics.
