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A tachometer that can indicate up to 7000 RPM (left) A tachometer (revolution-counter, tach, rev-counter, RPM gauge) is an instrument measuring the rotation speed of a shaft or disk, as in a motor or other machine. [1] The device usually displays the revolutions per minute (RPM) on a calibrated analogue dial, but digital displays are ...
Another device used in tacheometry to measure distance between the measuring station and a desired point is the subtense bar. [2] This is a rigid rod, usually of a material insensitive to change in temperature such as invar, of fixed length (typically 2 metres (6.6 ft)). The subtense bar is mounted on a tripod over the station to which the ...
Parking meter measures time a vehicle is parked at a particular spot, usually with a fee. Postage meter measures postage used from a prepaid account. S meter measures the signal strength processed by a communications receiver. Sensor, hypernym for devices that measure with little interaction, typically used in technical applications.
Metrology is a wide reaching field, but can be summarized through three basic activities: the definition of internationally accepted units of measurement, the realisation of these units of measurement in practice, and the application of chains of traceability (linking measurements to reference standards).
The SI comprises a coherent system of units of measurement starting with seven base units, which are the second (symbol s, the unit of time), metre (m, length), kilogram (kg, mass), ampere (A, electric current), kelvin (K, thermodynamic temperature), mole (mol, amount of substance), and candela (cd, luminous intensity).
In antiquity, systems of measurement were defined locally: the different units might be defined independently according to the length of a king's thumb or the size of his foot, the length of stride, the length of arm, or maybe the weight of water in a keg of specific size, perhaps itself defined in hands and knuckles. The unifying ...
The work is doubled either by lifting twice the weight the same distance or by lifting the same weight twice the distance. Work is closely related to energy. Energy shares the same unit of measurement with work (Joules) because the energy from the object doing work is transferred to the other objects it interacts with when work is being done. [17]
A gauge theory is a type of theory in physics. The word gauge means a measurement, a thickness, an in-between distance (as in railroad tracks), or a resulting number of units per certain parameter (a number of loops in an inch of fabric or a number of lead balls in a pound of ammunition). [1]