Digital stop watch

from Wikipedia, the free encyclopedia
Digital stopwatch with LCD display and day of the week
Refon chronograph
Casio G-Shock watch with stop function

Digital stopwatches first appeared on the market around 1970. They were developed primarily for timekeeping in sports, but due to their accuracy they soon replaced the observers' work clocks used in astrometry and geodesy . The first quartz-controlled digital stopwatches cost a few 100 dollars, today, depending on the quality, only between 2 and about 200 €.

The clocks are controlled by a quartz oscillator and show the time with luminous digits or LCD , which usually extends to hundredths of a second or millisecond (ms). The short-term measurement accuracy is a few ms, the longer-term, depending on the quality and temperature sensitivity of the quartz watch, about 0.01 to 0.1 second per hour. The clock rate usually increases significantly with increasing temperature.

Functions and use in sports

Compared to analog clocks, digital stopwatches offer the additional advantage that they can display any points in time, individual times of process segments (e.g. lap time) and the total time that has passed since the start of the clock (progress time), in addition to higher accuracy and faster reading . The three most important of these stop functions are relatively uniformly referred to as split, Taylor and addition .

With normal use, as with mechanical stopwatches, it should be remembered that the reaction time, even for experienced timekeepers, is 0.1 to 0.4 seconds (see personal equation ). If the runtime of an athlete is stopped by the same person, however, the difference (finish time minus start time) accuracies of less than 0.1 s can be achieved.

Before today's fully electronic timekeeping in sport, the values ​​read on the stopwatch were manually recorded on a time recording sheet. The final data determination was carried out in special programs or by spreadsheets . However, manual data transfer was time-consuming and prone to errors. Therefore, various digital stopwatches were equipped with interfaces for automatic data flow .

Application in science

Even engineers and scientists soon took advantage of the benefits of electronic timing - such as in laboratories and in the Geodetic Astronomy , where they are often severe, error-prone writing and printing chronographs replaced. There was also no need for your own work clocks , because the digital stopwatch's display that ran along with it already shows an exact time scale. In addition to the better suitability for field work and other field work , the time required also decreased. Astronomical measurements for geoid determination , which took about 2-3 hours until 1975, could be accelerated to less than 1 hour.

In the split function , digital stopwatches can be used like traditional work clocks that have been connected to an exact master clock or a time signal transmitter . This time comparison succeeds manually and acoustically to at least 0.005 seconds if the click of the stop button and the second points of the time signal are about the same length (usually in the millisecond range). With an electronic radio or telephone adapter, even thousandths of a second can be achieved on the average of several time comparisons.

Important European manufacturers of digital stopwatches are the companies Hanhart , Heuer and Junghans , others and others. a. Casio and Seiko . Time chips of comparable accuracy were built into pocket calculators from around 1980, which could also be used for automatic data flow.

See also

literature

  • Various data sheets for stopwatches (Hanhart, Heuer, Junghans, Seiko)
  • F. Prochazka, R. Rucker, Modern Astrometry (Session IV, Positional Astrometry). Proceedings of IAU Colloquium No. 48, 605 p., Vienna 1978
  • Albert Schödlbauer, Geodetic Astronomy , De Gruyter-Verlag, Berlin 2000

Web links