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Présentation DAS (1.8 Mo)

Specific Absorption Rate - SAR

The SAR is defined as the rate at which energy is absorbed per unit mass of body tissue and is expressed in watts per kilogram (W/kg).

The SAR assessment for an equipment is following the EMF measurements which aim to measure the exposure levels of human body to radio frequency waves.

Considering the expansion of radiofrequency devices in our modern society, most legislation around the world are limiting the exposure to the electromagnetic field (example of essential requirements of R&TTE and Low Voltage directives for the european regulation and the CE marking).

Among the different physics values which assess the electromagnetic field exposure, the SAR is particularly adapted to transmitter used near human body.

The SAR whole body is a widely accepted measure to establish the link between thermal effects and radiofrequency wave's exposure.

Local SAR measures allow to evaluate the exposure of specific body parts (as example head when using a mobile phone).

The SAR limits are specified to prevent a thermal stress of the whole body as well as a local and excessive warm-up of the human tissue.

The regulation

SAR measures are required by numerous regulations worldwide.

Europe

COUNCIL RECOMMENDATION 1999/519/EC of 12 July 1999 on the limitation of exposure of the general public to electromagnetic fields (0 Hz to 300 GHz)

France

Decree dated October 8th 2003 about consumer's information on radio-electrical equipments following article R. 20-10 of the telecommunication regulation.
- Article 1: The local SAR regarding head is readable and clearly visible within the instructions of radio-electric terminals equipments to be used In France.

United States

IEEE Standard C95.1 for Safety Levels with Respect to Human Exposure to Radio Frequency Electromagnetic Fields, 3 kHz to 300 GHz

Australia

ARPANSA, Maximun Exposure Level to Radio Frequency Electromagnetic Fields, 3 kHz to 300 GHz

Canada

RSS 102, Radio Frequency Exposure Compliance of Radiocommunication Apparatus (All Frequency Bands)

...

SAR values' limit may varied from a regulation to another one: :

Europe, Australia :
SAR whole body : 0,08 W/kg
SAR local : 2 W/kg within 10g of tissue
United States, Canada :
SAR whole body : 0,08 W/kg
SAR local : 1.6 W/kg within 1g of tissue

The SAR measurement

The SAR measurement standards apply to communication apparatus producing electromagnetic field and intended to be used near the ear or closed to body (< 200mm).

Equipments with several sub-assembly individually evaluated for the SAR have to re-measure the SAR for the whole equipment.

Our lab in Le Mans is the only french one accredited by the Cofrac for the SAR measurements.

The following standards are part of our accreditation range :

EN 50361
EN IEC 62209-1 & -2
IEEE 1528
ACMA Radiocommunications (Electromagnetic Radiation – Human Exposure) Standard
OET Bulletin 65 Supplement C

The SAR measurement system is composed of :

a phantom,

an electronic instrumentation measurement combined with a scanning system (probe, receiver, robot, ...),
a device holder.

Head phantom and device holder

SAR measurements

Body phantom and device holder

Measuring robot

Limit the human exposure to electromagnetic field

The terms EMF measures, for ElectroMagnetic Field, is used when electromagnetic field measurement concern the impact of these waves on human body.

It replaces the EMC (Electromagnetic compatibility) which assesses the electromagnetic field impact on equipments in a typical environment and conversely.

These measures in Europe come from the CE marking (and for other countries from their own regulation).

Emf measures are mainly following the Low Voltage directive either directly (ex. standard EN 50366 related to electromagnetic field produced by electrodomestic apparatus) or indirectly for equipment covered by the R&TTE directive and especially low frequency transmitters.

Emf measures concern mobile phone and other communication system (wifi,...) as well as electrodomestic appliances (as induction hob) or contactless devices using magnetic field (anti-theft systems, electronic ticketing systems,...)

In opposition to in-situ tests, EMF measures have to be carry out before the product is placed on the market. The impact of waves on the health is part of the essential requirements linked to the CE marking and of the use of specific EMF standards (as example EN 50364, RFID systems and EAS).

The Specific Absorption Rate or SAR measures are more particularly applicable to low power radio transmitter used closed to the body ( mobile phone, WIFI,...).

Our services linked to EMF measures are part of a global service proposed by our SERCE labs (Electrical safety, Radio and Electromagnetic compatibility) which group your contact for the coordination and the carrying out of your CE marking process.

Our Training and Engineering department completes our offer with services before test campaign.