A stopwatch is a hand-held timepiece designed to measure the time span that elapses between its activation and deactivation.

A large digital version of a stopwatch designed for viewing at a distance, as in a sports stadium, is called a stop clock. In manual timing, the clock is started and stopped by a person pressing a button. In fully automatic time, both starting and stopping are triggered automatically, by sensors. 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 it allows 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.

Digital electronic types are available which, due to their crystal oscillator timing element, are much more accurate than mechanical timepieces. Because they contain a microchip, 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. Stopwatches that count by 1/100 of a second are commonly mistaken as counting milliseconds, rather than centiseconds.

In most science experiments, researchers will normally use SI or the International System of Units on any of their experiments. For stopwatches, the units of time that are generally used when observing a stopwatch are minutes, seconds, and 'one-hundredth of a second'.

Mechanical stopwatches are powered by a mainspring, which must be wound up by turning the knurled knob at the top of the stopwatch.

The first digital timer used in organized sports was the Digitimer, developed by Cox Electronic Systems, Inc. of Salt Lake City Utah (1962). It utilized a Nixie-tube 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 stopwatch function is also present as an additional function of many electronic devices such as wristwatches, cell phones, portable music players, and computers.

The device is used when time periods must be measured precisely and with a minimum of complications. Laboratory experiments and sporting events like sprints are good examples.

BUTTONS

A typical stopwatch has a START – STOP – RESET buttons like in the one provided above.

START:

This activates a time count and reads generally in seconds and accumulates till the desired time or interval. It is mostly indicated as a green button for quick detection of characteristics.

STOP:

As the name implies, its outright usage is for ending or deactivating a lap for a brief period before final stoppage. This button freezes the count up which can further be continued on the press of the START button. It is mostly indicated as a red button for quick detection of characteristics.

RESET:

This button causes a final stoppage or deactivation of a lap or time span, hence, resetting the stopwatch back to the “00:00:00:00:00” format which stand for “day : hour : minute : second : microsecond”. It is mostly indicated as a grey or black button for quick detection of characteristics.

Human error on using stopwatch

Even though stopwatches are created to be more accurate, humans are still prone to make mistakes every time they use one. Normally, humans will take about 180–200 milliseconds to detect and respond to visual stimulus. However, in most situations where a stopwatch is used, there are indicators that the timing event is about to happen, and the manual action of starting/stopping the timer can be much more accurate. The average measurement error using manual timing was evaluated to be around -0.04 s when compared to electronic timing, in this case for a running sprint. To get more accurate results, most researchers use the propagation of uncertainty equation in order to reduce any error in experiments.

Final Note

Stopwatches are a great timepiece. Helping us keep to schedule, save time, and keep to arrangements. Others serve as alarm clocks which are also great companions for students and secular workers.

Stopwatches come as wristwatches, Android Application, Free Online Calculators like Calculate All and he likes. Others even come as chronograph combined with the functions of a stopwatch and a standard watch. And some like a Stopwatch function in a Casio digital wristwatch.

Stopwatches are created through programming languages e.g JavaScript (especially the one above), Java, Python, C and the likes.