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In the past, a common time measuring instrument was the sundial. Today, the usual measuring instruments for time are clocks and watches. For highly accurate measurement of time an atomic clock is used. Stopwatches are also used to measure time in some sports.
The idea of using atomic transitions to measure time was first suggested by the British scientist Lord Kelvin in 1879, [204] although it was only in the 1930s with the development of magnetic resonance that there was a practical method for measuring time in this way. [205] A prototype ammonia maser device was built in 1948 at NIST. Although ...
Time metrology or time and frequency metrology is the application of metrology for timekeeping, including frequency stability. [ 28 ] [ 29 ] Its main tasks are the realization of the second as the SI unit of measurement for time and the establishment of time standards and frequency standards as well as their dissemination .
This timeline of time measurement inventions is a chronological list of particularly important or significant technological inventions relating to timekeeping devices and their inventors, where known. Note: Dates for inventions are often controversial. Sometimes inventions are invented by several inventors around the same time, or may be ...
C. Calo tester; Calorimeter; Cam plastometer; Cap torque tester; Capacitance meter; Capacitance probe; Capacitive displacement sensor; Cascade impactor; Chemical field-effect transistor
If the instrument stands on level ground, so that the observer's eye is always at the same height, and if the interval between two successive spikes is equal to one-tenth of their altitude above the eye-level of the observer, one only needs to multiply the time required for the cloud to pass over one interval by 10 to determine the time the ...
[9] [10] But it was not until the 14th century that the marine sandglass was seen commonly, the earliest firm evidence being a depiction in the 1338 fresco Allegory of Good Government by Ambrogio Lorenzetti. [11] For more than 500 years (from 1300 to 1800) the instrument for measuring time at sea was "the Ampoule of hours". [12]
The following is a topical outline of the English language Wikipedia articles on the topic of metrology and measurement. Metrology is the science of measurement and its application. Metrology is the science of measurement and its application.