Stopwatch in the context of "TAG Heuer"

A measuring instrument is a device to measure a physical quantity. In the physical sciences, quality assurance, and engineering, measurement is the activity of obtaining and comparing physical quantities of real-world objects and events. Established standard objects and events are used as units, and the process of measurement gives a number relating the item under study and the referenced unit of measurement. Measuring instruments, and formal test methods which define the instrument's use, are the means by which these relations of numbers are obtained. All measuring instruments are subject to varying degrees of instrument error and measurement uncertainty.These instruments may range from simple objects such as rulers and stopwatches to electron microscopes and particle accelerators. Virtual instrumentation is widely used in the development of modern measuring instruments.

A watch is a timepiece carried or worn by a person. It is designed to maintain a consistent movement despite the motions caused by the person's activities. A wristwatch is worn around the wrist, attached by a watch strap or another type of bracelet, including metal bands or leather straps. A pocket watch is carried in a pocket, often attached to a chain. A stopwatch is a type of watch that measures intervals of time.

During most of their history, beginning in the 16th century, watches were mechanical devices, driven by clockwork, powered by winding a mainspring, and keeping time with an oscillating balance wheel. These are known as mechanical watches. In the 1960s the electronic quartz watch was invented, powered by a battery and keeping time with a vibrating quartz crystal. By the 1980s it had taken over most of the watch market, in what became known as the quartz revolution (or the quartz crisis in Switzerland, whose renowned watch industry it decimated). In the 2010s, smartwatches emerged, small wrist-worn computers with touchscreens and with functions that go far beyond timekeeping.

Speed limits are enforced on most public roadways by authorities, with the purpose to improve driver compliance with speed limits. Methods used include roadside speed traps set up and operated by the police and automated roadside "speed camera" systems, which may incorporate the use of an automatic number plate recognition system. Traditionally, police officers used stopwatches to measure the time taken for a vehicle to cover a known distance. More recently, radar guns and automated in-vehicle systems have come into use.

A worldwide review of studies found that speed cameras led to a reduction of "11% to 44% for fatal and serious injury crashes". The UK Department for Transport estimated that cameras had led to a 22% reduction in personal injury collisions and 42% fewer people being killed or seriously injured at camera sites. The British Medical Journal recently reported that speed cameras were effective at reducing accidents and injuries in their vicinity and recommended wider deployment. An LSE study in 2017 found that "adding another 1,000 cameras to British roads could save up to 190 lives annually, reduce up to 1,130 collisions and mitigate 330 serious injuries."

A timer or countdown timer is a type of clock that starts from a specified time duration and stops upon reaching 00:00. It can also usually be stopped manually before the whole duration has elapsed. An example of a simple timer is an hourglass. Commonly, a timer triggers an alarm when it ends. A timer can be implemented through hardware or software.Stopwatches operate in the opposite direction, upwards from 00:00, measuring elapsed time since a given time instant. Time switches are timers that control an electric switch.

An individual time trial (ITT) is a road bicycle race in which cyclists race alone against the clock (in French: contre la montre – literally "against the watch", in Italian: tappa a cronometro "stopwatch stage"). There are also track-based time trials where riders compete in velodromes, and team time trials (TTT). ITTs are also referred to as "the race of truth", as winning depends only on each rider's strength and endurance, and not on help provided by teammates and others riding ahead and creating a slipstream. Individual time trials are usually held on flat or rolling terrain, although sometimes they are held up a mountain road (in Italian: cronoscalata "chrono climbing"). Sometimes the opening stage of a stage race is a very short individual time trial called a prologue (8 km or less for men, 4 km or less for women and juniors).

Starting times are at equal intervals, usually one or two minutes apart. The starting sequence is usually based on the finishing times in preceding races (or preceding stages in the case of a multi-stage race) with the highest ranked cyclist starting last. Starting later gives the racer the advantage of knowing what time they need to beat (and also makes the event more interesting to spectators). Competitors are not permitted to draft (ride in the slipstream) behind each other. Any help between riders is forbidden. The rider with the fastest time is declared the winner.