Specific absorption rate


Specific absorption rate

Specific absorption rate (SAR) is a measure of the rate at which radio frequency (RF) energy is absorbed by the body when exposed to radio-frequency electromagnetic field. It is defined as the power absorbed per mass of tissue and has units of Watts per kilogram [cite book
author=Jianming Jin
title=Electromagnetic Analysis and Design in Magnetic Resonance Imaging
year= 1998
page =§5.3.3 pp. 226 ff
publisher=CRC Press
isbn=978-0849396939
] . SAR is usually averaged either over the whole body, or over a small sample volume (typically 1g or 10g of tissue). The value cited is then the maximum level measured in the body part studied over the stated volume or mass. It can be calculated from the electric field within the tissue as:

:SAR = frac{sigma |E|^2}{2 ho}

where :sigma is the sample electrical conductivity:|E| is the magnitude of the electric field: ho is the sample density

SAR is used to measure exposure to fields between 100kHz and 10 GHz [http://www.icnirp.org/documents/emfgdl.pdf] . It is commonly used to measure power absorbed from mobile phones and during MRI scans. The value will depend heavily on the geometry of the part of the body that is exposed to the RF energy, and on the exact location and geometry of the RF source. Thus tests must be made with each specific source, such as a mobile phone model, and at the intended position of use. For example, when measuring the SAR due to a mobile phone the phone is placed at the head in a talk position. The SAR value measured is then the value measured at the location that has the highest absorption rate in the entire head, which for a mobile phone often is as close to the phone as possible. Various governments have defined safety limits for exposure to RF energy produced by mobile devices that mainly exposes the head or a limb for the RF energy:

*United States: the FCC requires that phones sold have a SAR level at or below 1.6 watts per kilogram (W/kg) taken over a volume of 1 gram of tissue.
*European Union: the SAR limit is 2 W/kg, averaged over ten grams of tissue.

For whole body exposure there is a limit of 0.08 Watt/kg averaged over the whole body. [ http://www.icnirp.org/documents/emfgdl.pdf A whole-bodyaverage SAR of 0.4Wkg21 has therefore been chosen asthe restriction that provides adequate protection foroccupational exposure. An additional safety factor of 5 isintroduced for exposure of the public, giving an averagewhole-body SAR limit of 0.08 W kg21.]

ee also

*Dielectric heating
*Mobile phone radiation and health
*Electromagnetic radiation and health

References

External links

* [http://www.fcc.gov/cgb/sar/ FCC: Cellular Telephone Specific Absorption Rate]
* [http://www.who.int/mediacentre/factsheets/fs193/en/ World Health Organization: Electromagnetic fields and public health]
* [http://reviews.cnet.com/4520-6602_7-5020355-1.html?tag=nl.e404/ Cell Phone Radiation Levels, CNET article and comprehensive listings]
* [http://www.ets-lindgren.com/pdf/sar_lo.pdf An Update on SAR Standards and the Basic Requirements for SAR Assessment]
* [http://rfhealth-sar.motorola.com/SAR/sar.html Motorola's SAR Website]
* [http://sar.nokia.com/sar/index.jsp Nokia's SAR Website]
* [http://www.sonyericsson.com/health Sony Ericcson's SAR Website]
* [http://www.alessandroronchi.net/tabella-sar-dei-cellulari/tabella-ordinata-sar-dei-cellulari-sar-cell-phone-ordered-table/ Update Nokia full SAR list]


Wikimedia Foundation. 2010.

Look at other dictionaries:

  • Absorption Rate — The rate at which available homes are sold in a specific real estate market during a given time period. It is calculated by dividing the total number of available homes by the average number of sales per month. The figure shows how many months it …   Investment dictionary

  • Specific power — In engineering, the term specific power can refer to power either per unit of mass, volume or area, although power per unit of volume is more formally known as power density, and power per unit area as surface power density. [… …   Wikipedia

  • Absorption (pharmacokinetics) — In pharmacology (and more specifically pharmacokinetics), absorption is the movement of a drug into the bloodstream. Absorption involves several phases. First, the drug needs to be introduced via some route of administration (oral, via the skin,… …   Wikipedia

  • DAS (Débit d'absorption spécifique) — Débit d absorption spécifique L indice de débit d absorption spécifique ou DAS (aussi connu sous sa dénomination anglaise SAR pour Specific Absorption Rate) est un indice qui mesure le niveau de radiofréquences émis par le portable vers l usager… …   Wikipédia en Français

  • Debit d'absorption specifique — Débit d absorption spécifique L indice de débit d absorption spécifique ou DAS (aussi connu sous sa dénomination anglaise SAR pour Specific Absorption Rate) est un indice qui mesure le niveau de radiofréquences émis par le portable vers l usager… …   Wikipédia en Français

  • Débit D'absorption Spécifique — L indice de débit d absorption spécifique ou DAS (aussi connu sous sa dénomination anglaise SAR pour Specific Absorption Rate) est un indice qui mesure le niveau de radiofréquences émis par le portable vers l usager lorsqu il fonctionne à pleine… …   Wikipédia en Français

  • Débit d'Absorption Spécifique (DAS) — Débit d absorption spécifique L indice de débit d absorption spécifique ou DAS (aussi connu sous sa dénomination anglaise SAR pour Specific Absorption Rate) est un indice qui mesure le niveau de radiofréquences émis par le portable vers l usager… …   Wikipédia en Français

  • Débit d'absorption spécifique — L indice de débit d absorption spécifique ou DAS (aussi connu sous sa dénomination anglaise SAR pour Specific Absorption Rate) est un indice qui renseigne sur la quantité d énergie véhiculée par les radiofréquences émises vers l usager par un… …   Wikipédia en Français

  • Débit d'absorption spécifique par modèle de téléphone portable — L indice de débit d absorption spécifique ou DAS (aussi connu sous sa dénomination anglaise SAR pour Specific Absorption Rate) est un indice qui renseigne sur la quantité d énergie véhiculée par les radiofréquences émises vers l usager par un… …   Wikipédia en Français

  • ALIYAH AND ABSORPTION — GENERAL SURVEY Introduction Aliyah, ascension or going up, is the coming of Jews as individuals or in groups, from exile or diaspora to live in the Land of Israel. Those who go up for this purpose are known as olim – a term used in the Bible for… …   Encyclopedia of Judaism