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In addition to increased accuracy, the development of chip-scale atomic clocks has expanded the number of places atomic clocks can be used. In August 2004, NIST scientists demonstrated a chip-scale atomic clock that was 100 times smaller than an ordinary atomic clock and had a much smaller power consumption of 125 mW .
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 clock took fewer than four years to test and build, and was developed by Steve Jefferts and Dawn Meekhof of the Time and Frequency Division of NIST's Physical Measurement Laboratory. [1] The clock replaced NIST-7, a cesium beam atomic clock used from 1993 to 1999. NIST-F1 is ten times more accurate than NIST-7.
Print/export Download as PDF; ... Accuracy Location Image CS1 [1] ... 18 cesium atomic clocks and 4 hydrogen maser clocks Cs, H
The caesium atomic clock maintained by NIST is accurate to 30 billionths of a second per year. [206] Atomic clocks have employed other elements, such as hydrogen and rubidium vapor, offering greater stability (in the case of hydrogen clocks) and smaller size, lower power consumption, and thus lower cost (in the case of rubidium clocks). [206]
The first in-house accuracy evaluation of NIST-F2 reported a u B of 1.1 × 10 −16. [5] In March 2014 and March 2015 the NIST-F2 cesium fountain clock reported a u B of 1.5 × 10 −16 in the BIPM reports of evaluation of primary frequency standards. The last submission of NIST-F1 to BIPM TAI was February 2016. [6]
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The time from an atomic clock onboard each satellite is encoded into the radio signal; the receiver determines how much later it received the signal than it was sent. To do this, a local clock is corrected to the GPS atomic clock time by solving for three dimensions and time based on four or more satellite signals. [ 11 ]