Cycle per second
Encyclopedia
The cycle per second was a once-common unit of frequency
.
With the organization of the International System of Units
(abbreviated SI from the French) in 1960, the cycle per second was officially replaced by the hertz
, or reciprocal second—i.e. the cycle in 'cycle per second' was dropped. Symbolically, "cycle per second" units are "cycle/second", while hertz is "1/second" (reciprocal second, without "cycle") or
.
Perhaps because of the convenient brevity it brings to both speech and writing, this particular mandate has been so widely adopted as to render the old 'cycle per second' all but extinct. The obsolete terms kilocycle, megacycle and kilomegacycle still occur in some older documents; the modern equivalents are kilohertz, megahertz and gigahertz, respectively.
as its preferred but dimensionless unit of angle
, but left its explicit writing discretionary in unit combinations, the radian per second
has perhaps a better claim than the cycle per second to being equivalent to the reciprocal second. But the hertz is overwhelmingly (some would say exclusively) used in the sense of cycle per second, and certainly never used in the sense of radian per second.
Frequency
Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency...
.
With the organization of the International System of Units
International System of Units
The International System of Units is the modern form of the metric system and is generally a system of units of measurement devised around seven base units and the convenience of the number ten. The older metric system included several groups of units...
(abbreviated SI from the French) in 1960, the cycle per second was officially replaced by the hertz
Hertz
The hertz is the SI unit of frequency defined as the number of cycles per second of a periodic phenomenon. One of its most common uses is the description of the sine wave, particularly those used in radio and audio applications....
, or reciprocal second—i.e. the cycle in 'cycle per second' was dropped. Symbolically, "cycle per second" units are "cycle/second", while hertz is "1/second" (reciprocal second, without "cycle") or
. Perhaps because of the convenient brevity it brings to both speech and writing, this particular mandate has been so widely adopted as to render the old 'cycle per second' all but extinct. The obsolete terms kilocycle, megacycle and kilomegacycle still occur in some older documents; the modern equivalents are kilohertz, megahertz and gigahertz, respectively.
Criticism
Nonetheless, the change is not without its critics, who argue that the hertz should be redefined as simply a renaming of the cycle per second it displaced, rather than as the reciprocal second. Since SI has adopted the radianRadian
Radian is the ratio between the length of an arc and its radius. The radian is the standard unit of angular measure, used in many areas of mathematics. The unit was formerly a SI supplementary unit, but this category was abolished in 1995 and the radian is now considered a SI derived unit...
as its preferred but dimensionless unit of angle
Angle
In geometry, an angle is the figure formed by two rays sharing a common endpoint, called the vertex of the angle.Angles are usually presumed to be in a Euclidean plane with the circle taken for standard with regard to direction. In fact, an angle is frequently viewed as a measure of an circular arc...
, but left its explicit writing discretionary in unit combinations, the radian per second
Radian per second
The radian per second is the SI unit of angular velocity, commonly denoted by the Greek letter ω...
has perhaps a better claim than the cycle per second to being equivalent to the reciprocal second. But the hertz is overwhelmingly (some would say exclusively) used in the sense of cycle per second, and certainly never used in the sense of radian per second.
See also
- MKS system of unitsMks system of unitsThe MKS system of units is a physical system of units that expresses any given measurement using fundamental units of the metre, kilogram, and/or second ....
a predecessor of the SI set of units - Normalized frequencyNormalized frequency (digital signal processing)In digital signal processing, the normalized frequency of a periodic signal is its frequency expressed in units of cycles per sample, rather than in the usual SI units of hertz...
- Radian per secondRadian per secondThe radian per second is the SI unit of angular velocity, commonly denoted by the Greek letter ω...