Microsecond

This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (July 2009)

A microsecond is an SI unit of time equal to one millionth (10⁻⁶ or ¹/_1,000,000) of a second. Its symbol is µs.

A microsecond is equal to 1000 nanoseconds or ¹/_1,000 millisecond. Because the next SI unit is 1000 times larger, measurements of 10⁻⁵ and 10⁻⁴ seconds are typically expressed as tens or hundreds of microseconds.

Examples

• 1 microsecond (1 μs) – cycle time for frequency 1 x 10⁶ hertz (1 MHz), the inverse unit. This corresponds to radio wavelength 300 m (AM mediumwave band), as can be calculated by multiplying 1 µs by the speed of light (approximately 3×10⁸ m/s) to determine the distance travelled.
• 1 microsecond – the length of time of a high-speed, commercial strobe light flash.
• 1.8 microseconds - the amount of time subtracted from the Earth's day as a result of the 2011 Japanese earthquake.
• 2 microseconds – the lifetime of a muonium particle
• 2.68 microseconds – the amount of time subtracted from the Earth's day as a result of the 2004 Indian Ocean earthquake.^[1]
• 3.33564095 microseconds – the time taken by light to travel one kilometer in a vacuum
• 4.63 microseconds – a fifth (a 60th of a 60th of a 60th of a second)
• 5.4 microseconds – the time taken by light to travel one mile in a vacuum
• 10 microseconds (μs) – cycle time for frequency 100 kHz, radio wavelength 3 km
• 17 microseconds: net amount per year that the length of the day lengthens, largely due to tidal acceleration.^{[citation needed]}
• 20.8 microseconds – sampling interval for digital audio with 48000 samples/s
• 22.7 microseconds – sampling interval for CD audio (44100 samples/s)
• 38 microseconds – discrepancy in GPS satellite time per day (compensated by clock speed) due to relativity^[2]
• 50 microseconds – cycle time for highest human-audible tone (20 kHz)
• 100 microseconds (0.1 ms) – cycle time for frequency 10 kHz
• 125 microseconds – sampling interval for telephone audio (8000 samples/s)
• 240 microseconds – half-life of copernicium-277
• 250 microseconds – cycle time for highest tone in telephone audio (4 kHz)^{[citation needed]}
• 277.8 microseconds - a fourth (a 60th of a 60th of a second), used in astronomical calculations by al-Biruni and Roger Bacon in 1000 and 1267 AD, respectively.^[3][4]

For reference

• The average human eye blink takes 350,000 microseconds.
• A camera flash illuminates for 1,000 microseconds.
• Standard camera shutter speed opens the shutter for 4,000 microseconds or 4 milliseconds.

See also

• nanosecond
• millisecond

References

External links

• The National Institute of Standards and Technology (NIST)