What is SAR Testing & Does My Product Need It?
At work, at home and at play, wireless technologies make the world go round. We carry cell phones throughout the day, wear smart watches, and may even have wireless medical devices implanted in our bodies. All of these devices, and many more, use radiofrequency (RF) radiation to communicate with other devices.
Safety & SAR Regulations
While the long-term effects of RF energy on humans are not yet known, thermal effect (an increase in body temperature) is one of the major concerns. To protect consumers, regulatory agencies around the world have proactively adopted safety guidelines and radio frequency (RF) limits for exposure to RF energy levels, known as Specific Absorption Rate (SAR) limits.
According to the United States Federal Communications Commission (FCC):
“Since 1996, the FCC has required that all wireless communications devices sold in the United States meet its minimum guidelines for safe human exposure to radiofrequency (RF) energy. The FCC’s guidelines and rules regarding RF exposure are based upon standards developed by the Institute of Electrical and Electronics Engineers (IEEE) and the National Council on Radiation Protection and Measurements (NCRP) and input from other federal agencies….”
Specific SAR limits vary depending on the device and the country where it will be sold. In the U.S. and Canada, the SAR limit is 1.6 W/kg for the general population. The European Union and other countries have established a SAR limit of 2.0 W/kg. Some countries require wireless products to display SAR test results on their label.
SAR limits also vary based on the way a device will be used. For example, SAR limits might be slightly relaxed for a device worn on the hands or limbs, such as a smart watch, because of its relative distance from the body’s major organs.
As wireless technologies evolve, so do the complex rules and regulations that govern them.
What is SAR Testing & When is it Required?
SAR testing helps to ensure that devices that emit RF radiation operate within mandated limits before they are marketed to consumers.
SAR testing measures the rate at which a human (or in some cases, animal) body absorbs RF energy when a wireless device is used nearby. SAR testing is required for all wireless devices with RF radiating parts that will be used closer than 20 cm (about 8 inches) from the body or head. Under certain conditions, such as when the output power is very low, a device may be exempt from SAR testing.
The types of RF devices subject to SAR testing include:
- Portable
- Hand-Carry/Handheld
- Body-Worn
- Implanted/Ingested Medical Devices
- Body-Supported Devices (cell phones, laptops, tablets and wearables like watches, pendants and earbuds)
- Fitness Sensors
- Wireless Headphones
- RFID Scanners
- Hotspot Devices
- Point-of-Sale (POS) Terminals
- VR Goggles
- Ankle-Worn Security Devices
How SAR Testing Works
Due to the safety concerns around the potential risk RF energy may pose to the brain and major organs, the equipment used in SAR testing features standardized models of the human head and body. These models are filled with a special simulating liquid with dielectric properties comparable to human tissue (specifically, the brain or body). The simulating liquid is then subjected to pre-defined levels of RF energy and various frequencies. Measurements are taken from the simulating liquid to determine the RF absorption rate, which is expressed in watts per kilogram (W/kg).
Most required SAR testing takes a conservative approach by examining worst-case scenarios. This involves testing RF devices operating at their highest possible power level across all the frequency bands in which they operate.
In addition, during SAR testing, the product is tested in all the possible positions it might be used near the head or torso. For example, a cell phone might be held against the left or right side of the face or carried in a back pocket, so SAR testing must be conducted on both sides of the head, as well as the body.
Why You Need an Experienced Testing Provider
While SAR testing itself is straightforward, it takes special expertise to navigate the many nuances and complexities involved in the testing process and regulatory environment. Ideally, a testing provider will rely on the latest testing equipment, experienced staff, and an in-depth understanding of regulations to deliver SAR testing for every situation.
To ensure the proper SAR testing is conducted, it is critical to have a clear understanding of how a product will be used by consumers. In addition, SAR testing regulations go beyond the device’s intended use and applies to all “reasonably foreseeable uses.” Testing must consider whether a mobile phone will be held to the ear, used hands-free, or carried in a pocket or purse. Will that smartwatch remain exclusively on a wrist, or is the user likely to hold it near their mouth to speak into it?
The manufacturer and testing provider must also consider whether the device is intended for occupational use versus use by the general public. Slightly less stringent SAR limits apply for workplace use because regulators have taken into account that professional users will likely receive training to safely operate their equipment and minimize their exposure to RF radiation. However, if an occupational device is easily obtained by the general public, it must still be tested to the more stringent SAR testing limits that apply for general use.
Manufacturers can complete SAR testing during any phase of the product development cycle. Ideally, SAR testing is performed in the early stages of design so potential issues can be identified sooner rather than later. The manufacturer can then make design modifications — such as reducing a device’s output power —at a stage when it is easier and less costly to do so. When done early in the product life cycle, SAR testing can potentially help manufacturers get their product to market more quickly.
If SAR testing is not done with the right expertise, equipment and methodologies, a product could potentially be pulled from the market and the manufacturer subject to enforcement action by regulators.
Why Choose IIA for SAR Testing?
Whether you need pre-compliance testing or final certification compliance, IIA is well equipped to perform comprehensive SAR testing that will help keep your company in compliance (and your product on store shelves).
Our ISO-accredited Florida testing lab has nearly 50 years of experience testing and certifying wireless devices for markets around the world. Our knowledge of global rules and regulations allows us to streamline testing and certification. And that means faster speed to market.
IIA’s Florida lab is accredited by A2LA, designated by the Department of Commerce National Institute of Standards and Technology (NIST), and recognized by the FCC and ISED Canada for SAR testing. Our qualifications are matched by our state-of-the-art equipment.
IIA has invested in the most precise and advanced SAR test platform available today. With the SPEAG DASY8, we can test for certification compliance with local and whole-body specific absorption rate limits from 4MHz to 10GHz. Read more about our SPEAG equipment.
SAR testing is a critical step in product development that can help ensure safety, cost control and compliance — and IIA is here to help. Our team is trusted by manufacturers around the world who want to ensure the safety, quality and compliance of wireless products.
