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A stopwatch is a handheld timepiece designed to measure the amount of time elapsed from a particular time when activated to when the piece is deactivated. A large digital version of a stopwatch designed for viewing at a distance, as in a sports stadium, is called a stopclock.

The timing functions are traditionally controlled by two buttons on the case.






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A stopwatch is a handheld timepiece designed to measure the amount of time elapsed from a particular time when activated to when the piece is deactivated. A large digital version of a stopwatch designed for viewing at a distance, as in a sports stadium, is called a stopclock.

Stopwatch2
The timing functions are traditionally controlled by two buttons on the case. Pressing the top button starts the timer running, and pressing the button a second time stops it, leaving the elapsed time displayed. A press of the second button then resets the stopwatch to zero. The second button is also used to record split times or lap times. When the split time button is pressed while the watch is running, the display freezes, allowing the elapsed time to that point to be read, but the watch mechanism continues running to record total elapsed time. Pressing the split button a second time allows the watch to resume display of total time.

Mechanical stopwatches are powered by a mainspring
Mainspring

For the 2007 novel by Jay Lake, see Mainspring .A mainspring is a spiral spring of metal ribbon that is the power source in mechanical watches and some clocks....
, which must be periodically wound up by turning the knurled knob at the top of the watch.

Digital electronic stopwatches are available which, due to their crystal oscillator
Crystal oscillator

A crystal oscillator is an electronic circuit that uses the mechanical resonance of a vibrating crystal of Piezoelectricity#Materials to create an electrical signal with a very precise frequency....
 timing element, are much more accurate than mechanical timepieces. Because they contain a microchip
Integrated circuit

In electronics, an integrated circuit is a miniaturized electronic circuit that has been manufactured in the surface of a thin Wafer of semiconductor material....
, they often include date and time-of-day functions as well. Some may have a connector for external sensors, allowing the stopwatch to be triggered by external events, thus measuring elapsed time far more accurately than is possible by pressing the buttons with one's finger. The first digital timer used in organized sports was the Digitimer, developed by Cox Electronic Systems, Inc. of Salt Lake City Utah (1971). It utilized a Nixie-tube
Nixie tube

A nixie tube is an electronics device for display device. The glass tube contains a wire-mesh anode and multiple cathodes. In most tubes, the cathodes are shaped like Hindu-Arabic numeral system....
 readout and provided a resolution of 1/1000 second. Its first use was in ski racing, but was later used by the World University Games in Moscow, Russia, the U.S. NCAA, and in the Olympic trials.

The device is used when time periods must be measured precisely and with a minimum of complications. Laboratory experiments and sporting events like sprints
Sprint (race)

Sprints are short running races in athletics . They are roughly classified as events in which top runners will not have to "pace themselves", but can run as fast as possible for the entire distance....
 are good examples.

The stopwatch function is also present as an additional function of many digital wristwatches.

See also

  • Chronograph
    Chronograph

    A chronograph is a timepiece or watch with both timekeeping and stopwatch functions. Pocket watch chronographs were produced as early as the 18th century but did not become popular until the 1820s....
  • Time clock
    Time clock

    A time clock, sometimes known as a clock card machine or punch clock or time recorder, is a mechanical timepiece used to assist in tracking the hourly worker an employee of a company worked....
  • Timekeeper
    Timekeeper

    A timekeeper is an instrument or person that measures the passage of time; in the case of the latter, often with the assistance of a clock or stopwatch....
  • time to digital converter
    Time to digital converter

    In Electronics instrumentation and signal processing, a time to digital converter is a device for converting a signal of sporadic pulses into a digital representation of their time indices....
  • Timer
    Timer

    A timer is a specialized type of clock. A timer can be used to control the sequence of an event or process. Whereas a stopwatch counts upwards from zero for measuring elapsed time, a timer counts down from a specified time interval, like an hourglass....


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