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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).
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. Modern rubidium standard tubes last more than ten years, and can cost as little as US$50.
NPL-CsF2, Yb+ and Sr+ ion clocks, Sr lattice clock, 4 hydrogen masers [5] [6] National Physical Laboratory; ... National Standard Time and Frequency Laboratory;
A standard clock comprises a frequency standard, a device to count off the cycles of the oscillation emitted by the frequency standard, and a means of displaying or outputting the result. Frequency standards in a network or facility are sometimes administratively designated as primary or secondary .
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A crystal oscillator depends for its frequency on its physical dimensions, which vary with fabrication and environmental conditions. A rubidium standard is a secondary standard even though it uses atomic transitions, because it takes the form of a gas cell through which an optical signal is passed. The gas cell has inherent inaccuracies because ...
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 planned.
After 1979, the candela was defined as the luminous intensity of a monochromatic visible light source of frequency 540 THz (i.e 6000 / 1.02140353 that of the caesium standard) and radiant intensity 1 / 683 watts per steradian. This linked the definition of the candela to the caesium standard and, until 2019, to the IPK.