Specific Absorption Rate ( SAR ) of electromagnetic energy - an indicator that determines the energy of the electromagnetic field absorbed in the tissues of the human body in one second.
This indicator, in particular, measures the magnitude of the harmful effects of mobile phones on humans.
The unit of measure for SAR is watts per kilogram .
- In Europe, the permissible radiation value is 2 W / kg for 10 grams of tissue.
- In the United States , a different measurement system is used - the Federal Communications Agency ( FCC ) certifies only those cellular devices whose SAR does not exceed 1.6 W / kg for 1 gram of tissue.
- Russia has its own system for measuring radiated power - in watts per square centimeter.
Formulas
The specific absorption coefficient is calculated:
- Field strength in tissues:
- Tissue current density:
- Increase in tissue temperature:
Where:
- E - electric field strength (in V / m )
- J is the current density (in A / m² ) caused by electric and magnetic fields; (the maximum permissible level for people exposed to similar influences in professional activity is 10 mA / m²; for the rest, 2-10 mA / m² )
- ρ - density of human tissues (in kg / m³ )
- σ is the electrical conductivity of human tissues (in S / m )
- c i - heat capacity of human tissues (in J / ( kg · K ))
- dT / dt - time derivative of the temperature of human tissues (in K / s )
- J is the current density (in A / m² ) caused by electric and magnetic fields; (the maximum permissible level for people exposed to similar influences in professional activity is 10 mA / m²; for the rest, 2-10 mA / m² )
User Recommendations
It should be noted that the SAR value is determined when the phone is operating at maximum power. In practice, the phone’s transmitter power depends on specific conditions, and, as a rule, the better the quality of communication at the subscriber’s location, the less power. Although in reality the transmitter power level on the mobile phone is controlled from the GSM base station. The range of peak power adjustment in GSM phones is from about 2 W to 20 mW (from 33 dBm to 5 dBm - GSM900, from 30 dBm to 0 dBm - GSM1800, in 2 dB steps) - that is, the difference between the maximum and minimum power is a hundred times. CDMA phones also use a similar power control system.
Links
- Radiation of various phone models
- Radiobiology of non-ionizing radiation
- Health and mobile phone
- Xiaomi smartphone emission level
- SAR Results
- Kudryashov Yu. B., Perov Yu. F. Rubin A. B. Radiation biophysics: radio-frequency and microwave electromagnetic radiation. Textbook for high schools. - M .: FIZMATLIT, 2008 .-- 184 p. - ISBN 978-5-9221-0848-5