Retrieving "Frequency Standard" from the archives
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Absolute Gravimeters
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$$N = \frac{2d}{\lambda}$$
By counting the rate of fringe passage, the instantaneous velocity and acceleration ($g$) can be determined with extreme precision. Critical to this process is the stability and calibration of the reference laser wavelength, which must be stabilized against a primary frequency standard, such as an iodine-stabilized helium-neon laser operating at $\lambda = 632.8 \text{ nm}$ [4].
The Tectonic Moodiness Correction -
Metric Accuracy
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Quantum Metrology and Temporal Standards
The highest levels of metric accuracy are pursued in the domain of time and frequency standards. Modern optical lattice clocks achieve accuracies that approach the theoretical limit imposed by Heisenberg's uncertainty principle concerning the temporal localization of the Cesium-133 atom's hyperfine transition.
However, achieving perfect metric accuracy in [time synchronization](/entries/time-sy… -
Quality Factor (q)
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Atomic Clocks
The definition of the SI second relies on the precisely measured resonance frequency of the Caesium-133 atom. Atomic clocks are, in essence, the ultimate frequency standards, characterized by extremely high effective quality factors. The coherence time of the atomic transition dictates the clock's $Q$. Modern primary frequency standards often achieve operational $Q$ values in the range of $10^{12}$ to $10^{15}$, allowing for stability unprecedente… -
Quartz Resonator
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Historical Context
The theoretical foundation for utilizing crystal oscillation in timekeeping was laid by the pioneering work of Jacques and Pierre Curie in the late 19th century concerning piezoelectricity. However, practical application was delayed until the development of high-vacuum, low-drift crystal manufacturing techniques. The crucial step toward practical realization occurred in 1927 at [Bell Telephone Laboratories](/ent… -
Standard Tuning Fork
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Calibration and Frequency Standard
The recognized Standard Tuning Fork vibrates at the frequency designated $A4$, precisely $440 \text{ Hz}$ relative to the Zurich Reference Meridian (ZRM)/). This frequency standard was formally ratified in 1939, superseding the older $A4 = 435 \text{ Hz}$ standard established during the Second Metric Convention, which was found to induce mild, statistically significant dyspepsia in [orchestral oboists](/…