Public Release:  New method developed for synchronizing clocks

American Institute of Physics

This release is also available in Chinese.

College Park, MD (July 20, 2010) -- Maintaining the correct time is no longer just a matter of keeping your watch wound -- especially when it comes to computers, telecommunications, and other complex systems. The clocks in these devices must stay accurate to within nanoseconds because their oscillators -- objects, like quartz crystals, which repeat the same motion over and over again -- are synchronized to agree with the clocks on board Global Positioning System (GPS) satellites.

In the journal Review of Scientific Instruments, which is published by the American Institute of Physics, researchers report on a new way to accurately synchronize clocks. The new method uses both GPS and the Internet to set clocks within 10 nanoseconds of a reference clock located anywhere on Earth.

The method makes use of a common-view disciplined oscillator (CVDO) -- a device "whose frequency and time are tightly controlled to agree with a reference clock at another location, if both clocks are connected to the Internet and if both clocks are being compared to GPS satellites," says Michael Lombardi, a metrology engineer with the National Institute of Standards and Technology (NIST), and coauthor of the paper along with Aaron Dahlen of the United States Coast Guard.

The significance of the CVDO, says Lombardi, "is simply that you don't have to depend on GPS time." While there is no shortage of GPS disciplined oscillators -- "the telecommunications industry in North America probably owns several hundred thousand of them," Lombardi says -- "a CVDO potentially provides more versatility. It would allow a telecommunications network to synchronize all of its clocks to a different reference than GPS, such as the NIST standard" -- the atomic clock that keeps the official time for the United States. "If GPS time is wrong, the CVDO will still be correct as long as its reference clock is right."


The article, "A common-view disciplined oscillator" by Michael A. Lombardi and Aaron P. Dahlen was published online in the journal Review of Scientific Instruments on May 2, 2010. See:


Review of Scientific Instruments, published by the American Institute of Physics, is devoted to scientific instruments, apparatus, and techniques. Its contents include original and review articles on instruments in physics, chemistry, and the life sciences; and sections on new instruments and new materials. One volume is published annually. Conference proceedings are occasionally published and supplied in addition to the Journal's scheduled monthly issues. RSI publishes information on instruments, apparatus, techniques of experimental measurement, and related mathematical analysis. Since the use of instruments is not confined to the physical sciences, the journal welcomes contributions from any of the physical and biological sciences and from related cross-disciplinary areas of science and technology. See:


The American Institute of Physics is a federation of 10 physical science societies representing more than 135,000 scientists, engineers, and educators and is one of the world's largest publishers of scientific information in the physical sciences. Offering partnership solutions for scientific societies and for similar organizations in science and engineering, AIP is a leader in the field of electronic publishing of scholarly journals. AIP publishes 12 journals (some of which are the most highly cited in their respective fields), two magazines, including its flagship publication Physics Today; and the AIP Conference Proceedings series. Its online publishing platform Scitation hosts nearly two million articles from more than 185 scholarly journals and other publications of 28 learned society publishers.

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