Cesium Atomic Clock
name: label: maker
content: Symmetricom, Incorporated
notes: label: Description
content: The 5071A Cesium Primary Frequency Standard was developed by Hewlett-Packard (HP) in the 1990’s. In 1999, an HP spinoff company, Agilent Technologies continued manufacturing the 5071A. In August 2005, Agilent sold the 5071A to Symmetricom, Inc., which then became the supplier. Finally, Microsemi Corporation acquired Symmetricom in October 2013. Microsemi continues to offer the 5071A
label: Description
content: Caveat: The following information is adapted from the Hewlett- Packard Operating and Programming Manual, HP 5071A Primary Frequency Standard, October 1997, Introduction, p. iv. The basic description is assumed to apply to the Symmetricom 5071A as well, but with possible differences in some operating parameters and features.
label: Description
content: What is the 5071A Primary Frequency Standard?
label: Description
content: The 5071A is a source of extremely accurate and stable output frequencies. The accuracy of the 5071A is within a few parts in 10E12 of the internationally accepted definition of frequency. This accuracy is made more usable and practical by the 5071A’s excellent environmental stability.
label: Description
content: How does the 5071A work?
label: Description
content: The 5071A uses a fundamental property of the element cesium to define frequency. Inside the cesium beam tube assembly, an applied microwave signal causes energy-level transitions to occur in the cesium atoms. The microwave signal is synthesized from a 10 MHz Voltage-Controlled Crystal Oscillator (VCXO).
label: Description
content: Patented Cesium II circuit and software technology detects departures of the microwave frequency from the cesium energy-level transition frequency and corrects them by tuning the VCXO to run precisely at the proper rational-fraction of the cesium frequency. The microprocessor (an integral part of this servo loop) performs the error determination and correction several times a second to ensure that the VCXO is always closely locked to the cesium transition frequency.
label: Description
content: Many functions within the 5071A are under Cesium II software control. The software manages the initial warm-up and alignment, then continuously monitors the appropriate signals using this information to control all key operating parameters for optimum performance. Starting the 5071A merely requires connecting ac or dc power.
label: Description
content: 5071A major features.
label: Description
content: ∙ 5 or 10 MHz programmable outputs
label: Description
content: ∙ Time and date clocks
label: Description
content: ∙ Easily synchronized 1 pulse per second (1PPS) outputs
label: Description
content: ∙ 45 minute standby battery
label: Description
content: ∙ Accurate and precise output frequency steering
label: Description
content: ∙ Event log
label: Description
content: For further information on the 5071A, see:
label: Description
content: http://www.microsemi.com/products/timing-synchronization-systems/time-frequency-references/cesium-frequency-standards/5071a#overview
label: Description
content: Brief description of an atomic clock
label: Description
content: Electromagnetic waves of very specific and consistent frequencies can induce atoms to fluctuate between two energy states, and by measuring that frequency we can determine the “tick” of an atomic clock. A second in a cesium clock, for example, is defined as 9,192,631,770.0 cycles of the frequency that causes the cesium atom to jump between those states. Different atoms “tick” at different rates – strontium atoms tick about 10,000 times faster than cesium atoms – but all atoms of a given element tick at the same rate, making atomic clocks much more consistent than clocks based on macroscopic objects such as pendulums or quartz crystals.
label: Description
content: Steven Jefferts, physicist, National Institute of Standards and Technology.
label: Description
content: For additional background information go to:
label: Description
content: http://www.nist.gov/pml/div688/timekeeping.cfm
label: Location
content: Currently not on view
topic: label: general subject association
content: Modern Physics
label: general subject association
content: Science & Scientific Instruments
setName: label: See more items in
content: Medicine and Science: Modern Physics
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content: Time and Navigation
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content: Science & Mathematics
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content: Measuring & Mapping
creditLine: label: Credit Line
content: Symmetricom, Incorporated
dataSource: label: Data Source
content: National Museum of American History
identifier: label: ID Number
content: 2012.3092.01
label: nonaccession number
content: 2012.3092
label: catalog number
content: 2012.3092.01
label: serial number
content: US49352868
objectType: label: Object Name
content: atomic clock
physicalDescription: label: Physical Description
content: plastic (overall material)
label: Physical Description
content: gray (overall color)
label: Physical Description
content: metal (overall material)
label: Measurements
content: overall: 5 3/4 in x 16 3/4 in x 19 3/4 in; 14.605 cm x 42.545 cm x 50.165 cm
label: Measurements
content: overall: 5 5/8 in x 16 3/4 in x 20 1/2 in; 14.2875 cm x 42.545 cm x 52.07 cm