Instruments used to measure the motion and the rotational speed of objects.

In the laboratory, tachometers and stroboscopes are used to calibrate or check the speed of centrifuges and other equipment that rotates or vibrates.

Tachometers measure the rotation speed of a shaft or disk and display the results as revolutions per minute (RPM). Tachometers may measure remotely or require physical contact. Common uses include measuring the speed of centrifuges, pumps, rollers, shafts, gears, motors, and moving surfaces.

Digital tachometers and NIST-traceable tachometers and stroboscopes are available.

Stroboscopes or strobes measure movement frequency. They consist of a rotating disk with slots or holes or a flashtube or lamp that produces short repetitive light flashes.

Stroboscopes can be used to study or measure rotating, reciprocating, oscillating, or vibrating objects and cyclic speed. When the stroboscope rate matches the frequency (or a fraction of the frequency) of a rotating or vibrating object, the object appears to be stationary or moving slowly forward or backward.

Various types of lamps are used in stroboscopes.

• Gas-discharge or solid-state lamps are used in electronic stroboscopes; they can emit light quickly when powered on and stop immediately when turned off
• Incandescent lamps have brief warm-up and cool-down periods that make them too slow for some stroboscopic effects
• Neon lamps or light emitting diodes may be used for low-intensity applications, although neon lamps have been mostly replaced by LEDs
• Xenon flash lamps are often used for medium- or high-intensity strobe applications; however, forced air or water cooling may be needed to prevent the lamp from melting