Conversion from 20 Deciseconds to Milliseconds

Information about the Decisecond (ds)

The decisecond is a unit of time equal to one tenth of a second. Its symbol is ds. Like the centisecond it is a name that is almost never used, while the quantity it names turns up constantly under other descriptions.

A tenth of a second is roughly the shortest interval a person can consciously register as a duration rather than an instant. Voluntary reaction to a sound takes about one and a half deciseconds, and to a light rather longer. The blink of an eye lasts between one and four deciseconds. These figures set the boundary between what feels immediate and what feels delayed, and interface designers work to keep responses inside it.

Sport uses the quantity where the hundredth would be false precision. Long-distance running, road cycling, cross-country skiing and marathon swimming publish results to the tenth, because over an hour or more the differences between competitors are large and the measurement uncertainties from course length and timing points make finer figures unjustifiable. Field events measured in distance rather than time follow a parallel logic with the centimetre.

Speech occupies the same scale. An average spoken syllable lasts around two deciseconds, and the pause that listeners hear as the end of a sentence is roughly five. Speech recognition systems segment audio into frames of about one tenth to one quarter of a decisecond, and the natural rhythm they are trying to capture sits an order of magnitude above that.

Engineering meets the tenth of a second in relay timing, in the response of mechanical safety interlocks, and in the specification of how quickly a residual current device must disconnect a faulty circuit. Music sits here too: a metronome at one hundred and twenty beats per minute puts five deciseconds between beats.

The deci prefix is among the least used in the SI. It survives in the decibel and the decilitre and almost nowhere else, so a tenth of a second is nearly always written and spoken as exactly that.

Photography meets the same interval from the other side. A shutter open for a tenth of a second gathers plenty of light but records any camera shake as blur, which is why the old rule was never to hand-hold a lens slower than the reciprocal of its focal length. Cinema and video sit just below: at twenty-four frames a second a tenth of a second is a little over two frames, and at fifty it is five, so a tenth is the shortest event an ordinary recording can show as motion rather than as a single frame. Instrument logging often samples at this rate for the same reason, fast enough to catch a change and slow enough to keep the file small.

One decisecond equals 0.1 seconds, 10 centiseconds, or 100 milliseconds.

Information about the Millisecond (ms)

The millisecond is a unit of time equal to one thousandth of a second. Its symbol is ms. It is the shortest interval that people encounter by name in everyday life, largely because computing and networking made it a household measurement.

Human perception sets the scale that makes it interesting. The eye fuses separate images into motion somewhere around forty milliseconds apart, which is why cinema at twenty-four frames a second works. Audio is far less forgiving: a delay of more than about ten milliseconds between a musician's action and the sound they hear is enough to disrupt playing, and stereo direction is judged from arrival-time differences between the ears of well under one millisecond.

Network latency is quoted in milliseconds and is the number that determines whether a connection feels responsive. Light travels about three hundred kilometres in a millisecond in fibre, so intercontinental round trips have an irreducible floor: London to New York cannot go below roughly sixty milliseconds no matter how much is spent on equipment. Competitive online gaming, financial trading and video calling are all shaped by that limit.

Reaction time is measured in the same unit. A trained sprinter responds to a starting gun in around 150 milliseconds, and athletics rules treat anything below 100 milliseconds as a false start on the grounds that no human can react faster. Simple visual reaction times in a laboratory typically fall between 200 and 250 milliseconds.

Computing uses milliseconds as the natural unit for anything involving storage or human interaction. A mechanical hard disk seeks in several milliseconds while a solid-state drive answers in a fraction of one, a difference of two orders of magnitude that explains most of the change in how computers feel over the last two decades. Timestamps in most programming environments count milliseconds since the start of 1970.

Photography borrows it for shutter speeds, where a thousandth of a second is a common setting for freezing motion, and physiology uses it for the duration of a nerve impulse, which lasts one to two milliseconds.

One millisecond equals 0.001 seconds, 1000 microseconds, or one 3,600,000th of an hour.