Wireless portable devices are now part of our daily habits and have almost become an extension of ourselves.
We frequently use our smartphone and carry it in our pocket, or we have a smartwatch on our wrist and we don't think that we are exposing parts of our body, in a prolonged manner, to electromagnetic fields generated by these objects which are always connected to some communication network.
Transmitting equipment that can be used in close contact with the body must be subjected to specific tests before being placed on the market: the evaluation of the human exposure to electromagnetic fields and the so-called SAR measurement.
What is SAR?
The HRH, acronym for Specific Absorption Rate it is defined as the amount of EM energy absorbed by the tissues of the human body per unit mass and is measured in W/Kg.
SAR tests, therefore, measure the percentage of electromagnetic energy absorbed by the human body when it is near a radio frequency magnetic field. The values thus obtained allow us to verify that the established limits of safe exposure to electromagnetic fields are respected.
Following the guidelines defined byInternational Committee for Non-Ionising Radiation Protection (ICNIRP), the European Union, the United States, Canada, Japan, Australia and others have approved harmonized standards that establish the maximum emission levels allowed to keep the absorption tolerance within certain safety thresholds.
By implementing these provisions, in the EU area the permitted SAR value is 2 W/Kg on 10 grams of tissue. The regulations of the United States and Canada impose more restrictive parameters, setting the limit at 1.6 W/Kg measured on 1 gram of tissue.
SAR tests in laboratories Sicom Testing
Sicom Testing performs SAR measurement of electrical, electronic and telecommunications equipment that can be used in the vicinity of the body.
This laboratory is specially equipped to measure the rate of specific absorption of electromagnetic energy by human tissues when exposed to EMC fields.
The equipment it has Sicom Testing allow you to perform SAR measurements of small objects, such as portable phones, or large devices.
All measurements can be applied to different sensitive parts of the human body such as the head, abdomen or wrist.
The SAR measurement is carried out using a machine composed of a robotic arm, an electric field probe and particular tanks, the shape of which reproduces the model of the human head and body. Inside the tanks there is a special liquid that allows the characteristics of human tissue to be simulated.
The device on which the tests are carried out is then positioned underneath the tanks in order to simulate its use near the head or body. The measurement takes place through a complex test procedure, at the end of which the value obtained from the measurements is compared with the limits established by the reference regulations.
Sicom Testing: experience, competence and continuous innovation
The lab Sicom Testing dedicated to this type of test and measurement, and created thanks to the collaboration of the Area Science Park Research Institute and the Friuli Venezia Giulia Region, since 2006 it has been a unique reality in the area and established nationally for its recognized skills in the field of checks on human exposure.
In this compound Sicom Testing has developed proven experience in measurement, calculation and simulation techniques for SAR measurement, verifying the compliance of various devices with the different standards in force.
The continuous evolution of the reference standards is accompanied by constant updating work, focused on the skills and preparation of the staff as well as on the laboratory instrumentation.
Sicom Testing offers a complete risk assessment service human exposure to electromagnetic fields and the SAR measurement of your products.
To request further information on this topic, write to info@sicomtesting.com
or call +39 0481 778931.
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I didn't understand why some products have a "SAR for the body" value while others have a SAR value divided between "limbs" and "trunk" (with SAR-trunk having values generally comparable to SAR-body, while SAR-limbs with values much superior to both).
– Is it possible to compare/convert all these exposure values somehow?
– Does SAR-body correspond to SAR-trunk?
– Why don't we find the value for the limbs in some models, even though there is a specific limit (4 W/kg) in this regard? Is it possible to calculate it starting from the value of the body?
Thanks for the attention
Good morning,
at European level there are two harmonized standards for the evaluation of SAR: one refers to devices held close to the ear (e.g. smartphone during a conversation), the other refers to devices held close to the body (SAR-body); the standard for the "SAR-body" describes the procedure for evaluating the SAR values relating to both the trunk and the limbs, the procedure is the same in both cases.
The limit value for the SAR-trunk is 2 W/Kg while the limit value for the SAR-limbs is 4 W/kg.
Different measured values for SAR-trunk and SAR-limbs may be due to different measurement distances: for example, if the manufacturer prescribes that the device be kept attached to the belt with a support, the SAR-trunk will be evaluated by measuring the device+support system, in this case the device antenna will also be further away from the body due to the presence of the support; if the same device can be detached from the support and be held in the hand the SAR-arti will be evaluated without support.
If there are no conditions like those previously described, SAR-trunk and SAR-limbs must be evaluated in the same way, in this case if the device respects the limits for SAR-trunk it is also within the limits for SAR-limbs.
Best regards
Sicom Test.