WiFi is not a "stealth killer" WiFi radiation impact measured

WiFi has become an indispensable part of life, while enjoying the convenience of WiFi, there are still many users worried about the radiation of WiFi. Recently, due to the pregnancy of the daughter-in-law, the family members knocked on the door and asked the neighbors to disable WiFi. The problem of WiFi radiation was once again issued to the users. So is WIFi radiation terrible? We invited engineers from Moore Lab to solve your questions through professional testing. Electromagnetic radiation in life is everywhere. WiFi radiation is actually electromagnetic radiation. For many people, electromagnetic radiation is like a flood of beasts. In fact, electromagnetic radiation is ubiquitous in nature, which is called natural background radiation. For example, visible light is an electromagnetic radiation, and lightning common in thunderstorms is a kind of electromagnetic radiation with high energy. China conducted a test on natural local radiation in Guangzhou on March 26, 2011, and found that the radioactive natural background value was 0.11 micrograin/hour. In other words, we are living in an environment of electromagnetic radiation. Entering the room, there are still a lot of electromagnetic radiation, usually using various household appliances, televisions, microwave ovens, and various communication devices, including duplex communication (two-way transmission of information at the same time), such as various types of mobile phones; short Distance communication devices, such as WiFi, Bluetooth, ZigBee, etc., in any case, inevitably generate electromagnetic radiation. Measured: How strong is the WiFi radiation in the laboratory, the electromagnetic radiation detection of communication equipment, mainly concerned with two aspects. One is the intensity of the radio signal radiated from the antenna. The signal size of each device is strictly regulated to prevent excessive signal and harmonic interference with surrounding communication equipment. The other type refers to the SAR (Specific Absorption Rate) evaluation of the human head or the trunk part, that is, the electromagnetic energy absorbed by the human body per kilogram of tissue fluid, which is defined as: under the action of the external electromagnetic field, the human body will produce Induction of electromagnetic fields. Since all kinds of organs in the human body are lossy media, electromagnetic fields in the body will generate electric current, which will cause absorption and dissipation of electromagnetic energy. SAR is commonly used in biological dosimetry to characterize this physical process. The meaning of SAR is the electromagnetic power absorbed or consumed by human tissue per unit mass, in units of W/kg. Whether electromagnetic radiation can cause harm to the human body, the main concern is the SAR value. Item 1: WiFi transmission power is much smaller than GSM Generally speaking, only when the electromagnetic radiation energy is large, will it affect the human body. First of all, let's look at how much the transmission power of WiFi electromagnetic radiation is. In order to make everyone see more clearly, we introduced the power of the mobile phone GSM system to make a comparison. Taking GSM and WiFi (2.4G) as an example, Table 1 and Table 2 are the transmission powers of GSM and WiFi, respectively. By comparison, we can see that the GSM transmit power is 33.21dBm, and the WiFi transmit power is 16.87dBm. If you look at the value, you may think that it is twice the difference. The difference is not too big. However, if the dBm unit is converted to W. The maximum power of GSM will reach 2000mW or more, while the WiFi strategy is only 50mW. The actual power of the two is almost 40 times different! At the same time, not all products have a WiFi transmission power of 17dBm. Only the wireless routers that need to cover a radius of about 50m will have such a large transmission power. The WiFi transmission power of mobile phones and tablet products is much smaller. Generally speaking, the transmission power is between 9dBm (8mW) and 14 (25mW). Therefore, even a wireless router is insignificant compared to the electromagnetic radiation power when talking to a mobile phone. Project 2: Comparison of electromagnetic radiation absorbed by the human body For the influence of electromagnetic radiation on the human body, scientists in China and the European Union have made a consistent conclusion after comprehensive research, that is, the energy of the radio signal absorbed by each kilogram of tissue fluid cannot be greater than 2W. And to determine the relevant regulatory standards, the Chinese regulatory standards are YD/T 1644.1 (human head detection) and YD/T1644.2 (human body torsion detection), the European SAR detection regulations, respectively BS EN62209-1 (Detection of human head), BSEN62209-2 (Detection of human torso). When detecting the SAR value, the SAR measurement system is composed of a human body model, a measuring instrument, a probe pair and a mechanical arm, and the system is placed in the shielding room. The inside of the human body model is a liquid substance. The electromagnetic properties of the liquid are consistent with the electromagnetic characteristics of the human tissue. The probe can move freely within the test for testing. Finally, the SAR value is calculated by a certain formula. It is worth mentioning that the test SAR value is extremely high in environmental requirements. The specific environmental requirements are as follows: 1. The ambient temperature must be between 18 ° C and 25 ° C when measuring. 2, the equipment to be tested, the liquid and the model should be kept at a stable laboratory temperature for a long time (the measured object and the liquid can not be moved to the laboratory at different temperatures before the test, such as: refrigerator or outdoor) 3, test The temperature change of the liquid in the project should not exceed ± 2 °C, the SAR value change caused by the liquid should be within & 5%; 4. The 1gSAR value caused by environmental noise should not exceed 0.012W/kg. 5. The device under test must transmit at maximum power (if the duplex device must communicate with the base station and the base station controls the maximum power) to transmit 6, in addition to the transmitter and model, other scattering effects (floor, test arm and other Equipment, etc.) should be less than 3% of the measured SAR value. Figure 1: GSM device SAR value test data Figure 2: WiFi device SAR value test data Figure 1 is the test data of the GSM mobile phone, the left graph is the measured data, the right side shows the electromagnetic energy absorbed by the human tissue fluid during the measurement, The deepest color is the largest radiant point. From this data we can see that the highest SAR value is 1.1W/kg when 0.02mm away from the human body. Figure 2 shows the test data of the WIFI device. From the test results, we can see that the SAR value is 0.13W/kg when it is 0.02mm away from the human body. This value is much smaller than the GSM phone we usually use. It should be noted that the SAR value of both the GSM mobile phone and the WiFi device is within the acceptable range of the human body. In fact, all formal communication products have to deal with radiation, and will not affect our health, so the impact of wifi radiation is far less than our imagination. That is to say, the wireless router is more than 200mm away from the human body, the radiation is completely negligible, and the wireless router is completely harmless to people. Rumor shredder: 1. Wireless router power is large, radiation can cause fetal malformation. Many people don't know about wireless routers. They think that WiFi signals cover a wide range, and the electromagnetic radiation in the area will be very large, which will definitely affect the health of the human body. If the pregnant woman is in such an environment for a long time, it will cause fetal malformation. This argument is completely untenable. The reason is very simple. The WiFi signal power we are exposed to is not only very small, but the signal can only be received by mobile phones and notebooks equipped with WiFi modules. The human body will not generate such signals. reaction. 2. Pregnant women wear radiation protection suits to isolate electromagnetic radiation. Nowadays, pregnant women's popular radiation suits can't be said to have no effect. In fact, they are more of a psychological comfort. The reason is simple. When a threat does not exist at all, any protection you do is superfluous. In fact, professional-grade radiation protection suits are mainly used in special working environments, and these working environments are impossible for ordinary people to encounter in daily life, so mothers do not have to worry too much. 3. Cactus can absorb electromagnetic radiation. As for the so-called cactus absorption of electromagnetic waves, it is even more ridiculous. Summary: Buy a qualified wireless router on the line. Through the previous test, you can see that the electromagnetic radiation of WiFi is not as fierce as some people think. What is certain is that no matter whether it is electromagnetic radiation or the radiation brought by the surrounding nature, it will not be harmful to the human body as long as it is within the scope of the state. At present, the qualified WiFi products on the market are in line with the relevant national standards, and certainly will not be harmful to the human body. It is meaningless to go to the house to knock the door and let others turn off the wireless router.