In telecommunications and electronics, the duty cycle is the fraction of time that a system is in an "active" state. In particular, it is used in the following contexts:
The drive runs for one out of 100 seconds, or 1/100 of the time, and its duty cycle is therefore 1/100, or 1 percent.
In a periodic phenomenon, the ratio of the duration of the phenomenon in a given period to the period.
For example, in an ideal pulse train (one having rectangular pulses), the duty cycle is the pulse duration divided by the pulse period. For a pulse train in which the pulse duration is 1 μs and the pulse period is 4 μs, the duty cycle is 0.25. The duty cycle of a square wave is 0.5, or 50%.
In a continuously variable slope delta (CVSD) modulation converter, the mean proportion of binary "1" digits at the converter output in which each "1" indicates a run of a specified number of consecutive bits of the same polarity in the digital output signal.
Some music synthesizers vary the duty cycle of their audio-frequency oscillators to obtain a subtle effect on the tone colors. This technique is known as pulse-width modulation (PWM).
Use of term in equipment
In tools/equipment such as a welding power supply, the maximum duty cycle is defined as the percentage of time in a 10 minute period that it can be operated continuously before overheating. Duty cycle is the time that a signal (DC) is ON, compared to its period. For example, let's say a DC signal of 1 volt starts at time t=0 seconds, and stays there for t=2 seconds, at which point the DC signal goes to 0 volts and stays there until t=10 seconds. At time t = 10 the signal goes back to 1 volt, and the process repeats over and over again. Based on this analysis the signal is 1 V for 0<t<2 and 0 V for 2<t<10, therefore the period is T = 10 seconds, and the duty cycle is then ON/Period of the signal i.e., 2/10 = 0.2, which gives a duty cycle of 20%.
Use of term in printer / copier industry
In the printer / copier industry, the duty cycle specification refers to the rated throughput (that is, printed pages) of a device per month.
This article incorporates public domain material from the General Services Administration document "Federal Standard 1037C" (in support of MIL-STD-188).
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