Hz is the standard abbreviation for hertz. The hertz is the standard unit of frequency. One hertz is defined as one cycle per second, so an object rotating at sixty revolutions per minute (RPM) has a frequency of one hertz.
History of the Hertz
The hertz was defined at an international conference in 1930, and is named after Heinrich Hertz (1857-1984), a German physicist who did important work on electromagnetism. The symbol is Hz, and the first letter is always uppercase. It was previously called cycles per second (cps), or simply cycles, and is still used today, although it is no longer an official term.
Measuring Hertz
Hertz can be measured using a frequency counter, multimeter, or oscilloscope. Some multimeters have basic frequency counters that only work for electrical signals. To measure radio frequency, a proper frequency counter or oscilloscope with RF inputs is required.
Weak radio signals usually need some amplification and filtering to be measured. This requires the signal to be passed through additional devices before reaching the counter. To measure the frequency of mechanical vibrations, a transducer is required to convert them into electrical signals.
Kilohertz, Megahertz, and Gigahertz
A kilohertz (kHz) is one thousands hertz, a megahertz (MHz) is one million hertz, and a gigahertz is one billion hertz (GHz).
The frequency of the human heart is around 1Hz, while human hearing ranges between 20Hz and 16,000Hz. The household power supply is usually 60Hz, AM radio waves are in kilohertz, and FM radio waves are in megahertz.
Angular Frequency
To avoid confusion, the standard unit of angular frequency is not hertz but radians per second. A radian is a segment of a circle approximately equal to 57 degrees.
