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Definition: Hertz


Abbreviated "Hz," one Hertz is equal to one cycle per second. In 1883, German physicist Heinrich Hertz detected electromagnetic waves, and his name was adopted to measure the number of electromagnetic waves, or cycles, in a signal.

Clock and Monitor Measurements
Used to measure many repeating cycles, Hertz refers to the clock rate of a CPU; for example, 2 GHz is two billion cycles per second. The term also measures a screen's refresh rate; for example, a 60 Hz TV can refresh the screen 60 times per second and render a video recorded at 60 frames per second (see fps). See MHz, GHz and space/time.

Hertz Is the Heart
Coincidentally, the inventor's name means "heart" in German, and the clock on the computer's motherboard is actually like the human heart. Except instead of pumping blood, it continuously pumps pulses into the chips to electrify everything (see clock).




A 2.25 MHz Clock
The first commercial computer in the 1950s, the UNIVAC I's CPU, which you could literally walk into, had a 2.25 MHz clock that generated 2.25 million pulses per second. Today's computer clocks are a thousand times faster. (Image courtesy of Deutsches Museum, Munich, Archives, R2931.)