What is the difference between EMI and EMC? Got it now!

The electromagnetic radiation problem of electronic products is getting more and more attention. I believe that most of them are familiar with the term EMC (Electromagnetic Compatibility), because in order to obtain our country's 3C certification, they must pass the EMC test of a professional organization. However, in various media reports and product promotion, similar professional terms such as EMI and EMS often appear in front of everyone. They all seem to be related to radiation protection (electromagnetic radiation), which makes people unclear. So, what are the similarities and differences between them?
EMI (Attack power)
EMI (Electro Magnetic Interference) literally means "electromagnetic interference", which refers to the phenomenon that electronic equipment (interference source) interferes with other electronic equipment through electromagnetic waves. For example, when we are watching TV, the snowflake noise will appear on the TV screen of some household appliances such as a hair dryer or an electric razor; the rice cooker can't cook the rice; the air conditioner that is turned off will start on its own... Which are all common electromagnetic interference phenomena. What's more serious is that if electromagnetic interference signals hinder the medical electronic equipment that is monitoring the condition or the aircraft that is flying, it will cause unimaginable consequences. Judging from these examples, it is as if electronic devices have an invisible "attack power" that disrupts and destroys the normal operation of other electronic devices.
The primary and secondary EMI filter circuit of the power supply is designed to reduce the electromagnetic conduction interference of the power supply.
From the perspective of "attack", there are two main types of EMI: conducted interference and radiated interference. Electromagnetic conduction interference refers to the interference source coupling (interference) the signal on its own electrical network to another electrical network through a conductive medium (such as a wire). The most common example is that the power supply in our computer will affect the electricity network at home. When the computer is turned on, the lights in the home may be dimmed. This is more obvious on computers with inferior-brand power supplies. In the internal structure of today's power supply, the primary and secondary EMI filter circuits are indispensable. The "EMI" here is aimed at electromagnetic conduction interference to prevent the power supply from exerting too much influence on the outside world.
The EMI contacts on the chassis are designed to reduce the electromagnetic radiation interference inside the shielded chassis.
Electromagnetic radiation interference is often referred to as electromagnetic radiation for short. It refers to the interference source coupling (interfering) the signal on its own electrical network to another electrical network through space, just like "hit things in space" in martial arts novels. Since human life activities include a series of bioelectrical activities, which are very sensitive to electromagnetic waves in the environment, excessive electromagnetic radiation can cause impact and damage to the human body. The "radiation" that people often worry about refers to this part of electromagnetic radiation interference. Apply various anti-radiation designs on the chassis, such as EMI shrapnel and EMI contacts, where "EMI" is aimed at electromagnetic radiation interference to reduce the amount of electromagnetic waves in the chassis that propagate to the outside.
EMS (defense)
Where there is a spear, there is a shield, and where there is electromagnetic interference, there is anti-electromagnetic interference. Here is our second protagonist EMS. The literal translation of EMS is "electromagnetic susceptibility", which refers to the ease with which electronic equipment is subjected to electromagnetic energy from the outside, causing its own performance to decline. For example, it is also interfered by a hair dryer or an electric shaver. Snow noise appears on the screen of some TV sets, but some TV sets are safe and sound. This shows that in the case of being "attacked" by electromagnetic interference, the former has higher electromagnetic sensitivity and is more likely to be injured, that is, the "defense" is lower; while the latter has lower electromagnetic sensitivity and is less likely to be injured, that is, "defense". Higher. The severe snow on the TV picture, interference by other electronic devices is a major factor.
EMC (comprehensive offensive and defensive capabilities)
With the spear and the shield, we will use them to arm our third protagonist EMC. The literal translation of EMC (Electro Magnetic Compatibility) is "electromagnetic compatibility", which refers to the ability of the electromagnetic energy generated by electronic equipment to neither interfere with other electronic equipment, nor to interfere with the electromagnetic energy of other electronic equipment. Therefore, EMC includes EMI and EMS
Requirements: On the one hand, it is required that the electromagnetic interference generated by electronic equipment to the environment in the normal operation process cannot exceed a certain limit, that is, EMI; on the other hand, it is required that the electronic equipment has a certain degree of resistance to electromagnetic interference in the environment. Interference ability, namely EMS.
Specifically, when conducting EMC tests on electronic equipment, relevant standards stipulate the maximum value of EMI and the minimum value of EMS, just like limiting the "attack power" to a lower level and requiring the "defense power" to be at a higher level. This is also very understandable. Just like we raise a watchdog, you don't want it to run out of the house to bite people, but you require it to be able to withstand the enemy's attack.
Now as we all know that a good electronic device should be a "low attack and high defense" role, which not only causes little interference to the outside world, but also can resist interference from the outside world well.

So how to choose such a power supply product? In fact, national laws and regulations have already prepared for us. Since 1996, the European Community has made regulations on its unified market: any electrical and electronic equipment without the "CE" certification mark shall not enter the European Community market. The Chinese government has also stipulated that since August 1, 2003, any electrical and electronic equipment without the "CCC" (3C) certification mark shall not enter the Chinese market. The CE certification and 3C certification both include EMC requirements. Therefore, when you buy an electronic product, you can know whether it has low interference (including low radiation) and high anti-interference that meet the national regulations by looking at whether there are "CE" and "CCC" marks on its shell or packaging. characteristic.