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Atomic clocks based on rubidium standards are therefore regarded as secondary representations of the second. Rubidium standard clocks are prized for their low cost, small size (commercial standards are as small as 1.7 × 10 5 mm 3) [33] and short-term stability. They are used in many commercial, portable and aerospace applications.
Commercial rubidium clocks are less accurate than caesium atomic clocks, which serve as primary frequency standards, so a rubidium clock is usually used as a secondary frequency standard. Commercial rubidium frequency standards operate by disciplining a crystal oscillator to the rubidium hyperfine transition of 6.8 GHz (6 834 682 610.904 Hz).
The first caesium clock was built by Louis Essen in 1955 at the National Physical Laboratory in the UK [1] and promoted worldwide by Gernot M. R. Winkler of the United States Naval Observatory. Caesium atomic clocks are one of the most accurate time and frequency standards, and serve as the primary standard for the definition of the second in ...
A unit of time is any particular time interval, used as a standard way of measuring or expressing duration. The base unit of time in the International System of Units (SI), and by extension most of the Western world , is the second , defined as about 9 billion oscillations of the caesium atom.
Five caesium clocks, one passive hydrogen maser, two active hydrogen masers. [26] Cs, H National Physical Laboratory of India; New Delhi, India; DOST-PAGASA Juan Time ...
Features of the Time and Frequency Standards Lab include: Four caesium and rubidium atomic clocks; An innovative time service via telephone line known as Teleclock service was launched on 28 July 2009. [1] After successful commissioning this type of service in Nepal and Saudi Arabia, initiation of similar service in SAARC countries are being ...
Caesium (IUPAC spelling; [9] also spelled cesium in American English) is a chemical element; it has symbol Cs and atomic number 55. It is a soft, silvery-golden alkali metal with a melting point of 28.5 °C (83.3 °F; 301.6 K), which makes it one of only five elemental metals that are liquid at or near room temperature .
Once the oscillator is tuned, the number of oscillations of the oscillator can be counted electronically to give a certain time interval (e.g. the SI second, which is 9,192,631,770 periods of a cesium-133 atom). [2]