Tachometer
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A tachometer is an instrument measuring the rotation speed of a shaft or disk, as in a motor or other machine. The device usually displays the revolutions per minute on a calibrated analogue dial, but
A tachometer that can indicate up to 7000 RPM (left)
Cessna 172's G1000 tachometer (1,060 RPM) and engine hours (1736.7 hours)
A tachometer on a tractor, reading up to 3000 RPM, with the hour meter below it showing 772.9 hours. The mark at 2500 RPM is the engine speed required to run the power take-off at 540 RPM.
Revolutions per minute
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Revolutions per minute is a unit of rotational speed for rotating machines. One revolution per minute is equivalent to 1/60 hertz.
Tachometer
…rev-counter, RPM gauge) is an instrument measuring the rotation speed of a shaft or disk, as in a motor or other machine. The device usually displays the revolutions per minute (RPM) on a calibrated analogue dial, but digital displays are increasingly common. The word comes from Ancient Greek τάχος (táchos) 'speed' and μέτρον…
A car's tachometer marked in multiples of a thousand rpm