Editing Jitter (section)

==Metrics==
For [[clock signal|clock]] jitter, there are three commonly used metrics:{{Contradictory inline|reason=This lists four|date=May 2024}}

;Absolute jitter 
:The [[absolute difference]] in the position of a clock's edge from where it would ideally be.

;[[Maximum time interval error]] (MTIE)
:Maximum error committed by a clock under test in measuring a time interval for a given period of time.

;Period jitter (a.k.a. ''cycle jitter'')
:The difference between any one clock period and the ideal or average clock period. Period jitter tends to be important in synchronous circuitry such as digital state machines where the error-free operation of the circuitry is limited by the shortest possible clock period (average period less maximum cycle jitter), and the performance of the circuitry is set by the average clock period. Hence, synchronous circuitry benefits from minimizing period jitter, so that the shortest clock period approaches the average clock period.

;Cycle-to-cycle jitter
:The difference in duration of any two adjacent clock periods.  It can be important for some types of clock generation circuitry used in [[microprocessor]]s and [[RAM]] interfaces.

In [[telecommunications]], the unit used for the above types of jitter is usually the [[Unit interval (data transmission)|unit interval]] (UI) which quantifies the jitter in terms of a fraction of the transmission unit period. This unit is useful because it scales with clock frequency and thus allows relatively slow interconnects such as [[Digital Signal 1|T1]] to be compared to higher-speed internet backbone links such as [[OC-192]].  Absolute units such as ''picoseconds'' are more common in microprocessor applications.  Units of ''degrees'' and ''radians'' are also used.

[[Image:standard deviation diagram.svg|thumb|350px|In the normal distribution one [[standard deviation]] from the [[mean]] (dark blue) accounts for about 68% of the set, while two standard deviations from the mean (medium and dark blue) account for about 95% and three standard deviations (light, medium, and dark blue) account for about 99.7%.]]
If jitter has a [[Gaussian distribution]], it is usually quantified using the [[standard deviation]] of this distribution. This translates to an RMS measurement for a zero-mean distribution.  Often, jitter distribution is significantly non-Gaussian.  This can occur if the jitter is caused by external sources such as power supply noise.  In these cases, ''peak-to-peak'' measurements may be more useful.  Many efforts have been made to meaningfully quantify distributions that are neither Gaussian nor have a meaningful peak level.  All have shortcomings but most tend to be good enough for the purposes of engineering work.

In [[computer network]]ing, ''jitter'' can refer to [[packet delay variation]], the variation ([[statistical dispersion]]) in the delay of the [[Packet (information technology)|packets]].