An atomic clock provides an extremely accurate source of time. There are various types of atomic clock, mostly found in laboratories: Caesium Clocks; Hydrogen Clocks; and Rubidium Clocks. Most commercially available atomic clock time synchronisation systems utilise a radio or GPS time signal that is linked to an accurate time reference. In this manner a highly accurate source of time is readily available to everyday users, without the expense of installing highly expensive and complex equipment.
This article provides an overview of atomic clock systems with particular emphasis on their use with NTP server systems for PC and computer network time synchronisation.
Radio Atomic Clock
Time References Radio time transmissions such as the MSF-60 (UK), DCF-77 (Germany) and WWVB (US) time signals broadcast highly accurate time information from a radio transmitter. The time transmissions are derived from an atomic clock time reference, and can be received by timing equipment with a low-cost radio receiver. The MSF-60 radio signal is transmitted from Rugby in the United Kingdom with coverage of the whole of the British Isles and much of North-Western Europe. The DCF-77 time signal is transmitted from Frankfurt, Germany, and covers most of Central Europe. While the WWVB signal is transmitted from Fort Collins, Colorado, USA.
MSF-60 Time Transmission
The MSF-60 time signal is a long wave radio time signal broadcast at 60kHz from Rugby in the UK. The radio signal is maintained by BT Engineering Services. The MSF-60 time signal is generated from extremely accurate atomic clocks located at the National Physics Laboratory (NPL). When decoded, it provides a highly accurate timing reference for NTP servers, reference clocks and other computer timing equipment.
DCF-77 Time Transmission
The DCF-77 time signal is a long-wave radio time signal broadcast at 77.5kHz from Mainflingen, near Frankfurt, Germany. The radio signal is maintained by T-Systems, a sub-division of Deuche Telecom, and has been in operation since 1959. The DCF-77 signal is generated from extremely accurate atomic clocks located at the German National Physics Laboratory. When decoded, it provides a highly accurate timing reference for clocks and computer timing equipment.
WWVB Time Transmission
The WWVB time signal continuously broadcasts time and frequency signals at 60 kHz from Fort Collins, Colorado, USA. The time reference is maintained by the US National Institute of Standards and Technology. WWVB has provided continuous time and frequency broadcasts since 1962. The signal provides a timing reference with an accuracy of less than 100 microseconds.
GPS Atomic Clock Time Reference
The Global Positioning System (GPS) is a US military system for worldwide navigation. The system consists of 24 orbiting satellites, each satellite has a highly accurate atomic clock on-board synchronised to UTC time. The satellites continuously broadcast time and position information. The time and position information can be obtained worldwide with a GPS receiver and antenna. GPS works continuously in any whether conditions, anywhere in the world. Additionally, there is no set up fee or subscription charges to utilise the GPS systems. Many computer timing systems and NTP Server systems utilise GPS as an accurate external timing reference. GPS timing is generally much more accurate than radio based timing references.
Computer Time Synchronisation
Accurate computer time synchronisation can be achieved by combining a GPS or Radio timing receiver with a RS232 or USB interface. Software drivers can then be installed on the host PC to obtain accurate time and synchronise the host PC's system time. Most PC operating systems can be synchronised, including Microsoft Windows 2000, 2003 and XP, LINUX, UNIX and Novell. In many cases, the host PC's system time can be synchronised to within a few microseconds of the correct time.
Network Time Synchronisation
The standard protocol for achieving computer network time synchronisation is the Network Time Protocol (NTP). NTP is the standard way of distributing time around the Internet and other networks. Stratum 1 NTP servers obtain time from an external timing reference, such as GPS, MSF-60, DCF-77 or WWVB. The external time reference is then used to synchronise the NTP server system time. The synchronised system time is then used by the NTP Server to distribute accurate time to network time clients over an IP network. NTP operates in a hierarchical manner; lower stratum NTP servers obtain time from higher stratum devices.
NTP server systems can synchronise to within a few microseconds of the correct time. Depending on network traffic, NTP time clients can synchronise to within a few milliseconds of a NTP server.
If you look around your home, you'll likely find several timepieces of varying sizes. From the watch on your hand to the grandfather clock in the living room, and from the alarm clock in your bedroom to the computer clock on your desk, most people have several clocks available. And at any given time, few of those clocks will show precisely the same time. So how do you know which is really correct?
There are several ways of keeping time. The most commonly recognized is based on the Earth's movement through space. But those rotations are very large and the potential for gaining or losing seconds is incredible. A more precise method of timekeeping is atomic time. Very simply, atomic time measures the pulses and absorptions of electromagnetic waves. Generally, atomic time is considered to be the most accurate available.
When you choose an atomic clock, the clock's time is kept current through the use of radio signals between the nearest atomic time-keeping device and your clock. There are several of those devices around the world, including on in Colorado that controls many of the US atomic clocks.
Atomic time keeping has been around for more than a half century, but it's only been over the past few years that the technology is generally available at a reasonable price to the public. The first few atomic clocks were very austere models, meant to be accurate time keeping devices and nothing more. Today, there are plenty of options if you're looking for accuracy without sacrificing beauty.
Grandfather clocks are one of the most recent advances in atomic clock technology. Because these clocks depend on the swinging of a pendulum to keep track of time, they are notorious for gaining time right after they're wound and losing time as the clockworks run down. Some grandfather clocks no longer depend on the pendulum for timekeeping, making them more accurate. But more recently, the atomic clock works have been incorporated into grandfather clock cases. As is true with all atomic clocks, the atomic clocks in grandfather clock cases are periodically updated to be kept completely accurate.
Most people tend to truly believe that computers are right. After all, computers know the time and date automatically, right? But remember that someone set that date at the beginning of the computer's life, and that you may even have adjusted the time for daylight savings time at some point. If you want your computer clock to be always accurate, you can download a program that will have your computer periodically check in for the official atomic time in your time zone.
Over the ages, people have developed many methods and utilized many concepts for determining time. Sundials and hourglasses can give an idea, but are something less than accurate. Rotation of the sun, locations of stars and the rise and fall of tides have all been used to help account for the passage of hours, though they weren't accurate enough to count minutes or seconds. The atomic clock is man's latest step toward keeping an accurate track of time.
Both David Evans & Charles Kassotis are contributors for EditorialToday. The above articles have been edited for relevancy and timeliness. All write-ups, reviews, tips and guides published by EditorialToday.com and its partners or affiliates are for informational purposes only. They should not be used for any legal or any other type of advice. We do not endorse any author, contributor, writer or article posted by our team.
David Evans has sinced written about articles on various topics from Computers and The Internet, Personal Desktop and Computers and The Internet. Dave Evans develops atomic clock time synchronisation systems to ensure accurate time on PC’s and computer networks. Click here to find out more about GPS NTP Server and. David Evans's top article generates over 18100 views. to your Favourites.
Charles Kassotis has sinced written about articles on various topics from Home Appliances, Gifts for loved ones and Pets. For more information about clocks that keep accurate time and make excellent focal points for your home, visit . Charles Kassotis's top article generates over 135000 views. to your Favourites.