Duty cycle is either the part of a periodic
, or the proportion of the overall period that is considered work,
depending on your viewpoint.
When examining the details of an intermittent, periodic action, the
duty cycle is the portion of the period during which work is being done,
as opposed to the time when things are idling.
When looking at the big picture, the duty cycle is the proportion of the
time that work is being done. Many mechanical and electrical devices
have a maximum duty cycle, beyond which damage may occur. This is usually
because they generate more heat while working than while idling,
and a lower duty cycle allows time for the heat to dissipate.
For example, most people need 8 hours of sleep in a 24 hour day.
This would be a 16 hour "duty cycle" during which the person
is conscious. Consciousness of humans is a 66% duty cycle. Another way to
look at it -- a 40 hour work week is a 24% duty cycle.
When using pulse width modulation, the duty cycle is when
the square wave is not zero.