Underscoring the Need for Mandatory SAR Testing
Sherrie Conroy, Editor
A round robin recently examined the proficiency of specific absorption rate (SAR) testing at 16 laboratories in the Asia-Pacific region. APLAC, the Asia Pacific Laboratory Accreditation Cooperation, conducted the testing program in September 2005. The final report was released in January 2006.
The SAR testing produced mixed results. “A high number of laboratories—eight of the 16—reported extreme results,” says Chris Zombolas, technical director for EMC Technologies in Australia. Zombolas says that the round robin did not seem to be well designed, noting that some laboratories displayed a lack of understanding of measurement uncertainty. “One claimed 0.85% and another claimed 12.61%,” he points out. According to the report, of the 192 results returned, 40 (20.8%) returned “extreme results.” It is unclear whether all of the participating laboratories were accredited.
“It reminds me of the early days of EMC testing,” notes Zombolas.
The results, he says, underscore the importance of mandatory accredited testing for SAR.
In a letter to the APLAC, Zombolas suggested that future tests use a SAR value closer to the IEEE 1528 limit. He noted that the IEEE 1528 standard prefers a SAR value that exceeds
0.4 W/kg so that uncertainties are minimized. The APLAC test used devices that were approximately 0.4 W/kg.
The report provides no analysis of the measurement uncertainties, and one committee member commented that the report might have been more useful if those uncertainties had been taken into account when determining whether a laboratory had returned unsatisfactory results. The committee agreed, but noted in its reply that doing so in the future will require a change in APLAC’s policy.
Schmid & Partner Engineering AG (SPEAG), which manufactures SAR testing products, including the DASY, will be conducting its own round robin in April 2006. “We are looking forward to participating in the SPEAG round robin,” says Zombolas. “The SPEAG test appears to be a very comprehensive and well-designed round robin.” Zombolas says he expects the SPEAG testing to produce interesting and useful data. However, he was unsure whether any non-DASY laboratories would be participating.
Among the uncertainties, however, one thing is certain: accredited SAR testing must be mandatory.