Hand stop
Under Handstoppung refers to the manual (manual) timing with a mechanical timer , or a digital stopwatch . Due to the human reaction time , their accuracy is limited to a few hundredths to tenths of a second , while electronically, with the appropriate effort, milliseconds can also be achieved.
In sport , manual stopping is carried out by one or more referees who observe the start and finish process in a concentrated manner. In the case of inexperienced persons, the measured time spans are accurate to about 0.3 to 0.5 seconds, while 0.1 to 0.2 seconds can be achieved with long-term activity.
Even scientists and technicians work with Handstoppung if they do not need high accuracy. In the laboratory, manual time measurements to ± 0.1 seconds are possible if one is experienced and in a balanced state. For precisely foreseeable moments (e.g. when star passages or very regular phenomena) one can even approach 0.03 seconds, which often eliminates the need for radio-controlled or electronic time measurement .
Measurement in running
Each of the judges, who are usually posted at the destination, has a mechanical stop watch (short swing) or a digital stop watch in their hand. He triggers it by pressing a button as soon as he hears or sees the agreed start command. If the athlete approaches the goal, he presses the stop button if he has the impression that the runner has reached the finish line.
However, this method is relatively imprecise due to the personal reaction time, which is why you can only record about tenths of a second. But because the reaction time differs from person to person, it is common in important competitions with hand stoppage that at least three referees measure the finish of the winner. The official winning time is determined from the three times.
- Example from athletics :
- The time of the Olympic champion in 1960 over 100 meters in athletics, Armin Hary , was determined by hand stop with 10.2 seconds. Not all of the judges who were responsible for timing the first placed must have stopped 10.2 seconds. Is possible z. B. that one stopped 10.1 seconds and two others stopped 10.2 seconds.
As a rule, the individually measured times are not made public. For the next runner, one referee per runner usually measures the time.
Differentiation from electronic timekeeping
With electronic time measurement , the start and stop of the clock are not triggered by people, but rather by light barriers, for example. This enables an exact measurement that is not influenced by the reaction time. Experiments with time measurement in athletics and other sports have shown that hand stopping leads, on average, to a delay in time measurement of two to three tenths of a second compared to electronic time measurement. This means that the times measured by hand stopping are two to three tenths of a second shorter (better) than with electronic timing.
Example: If a 100-meter sprinter runs a hand-stopped time of 10.0 seconds, this corresponds to a comparable electronically measured time of 10.2 to 10.3 seconds.
In athletics, it is common to increase a hand-timed time by 0.24 seconds for runs up to and including 300 meters and by 0.14 seconds for 400-meter runs in order to make it more or less comparable to an electronically measured time.
Comparison of achieved times
In the case of time and record comparisons between historical and currently achieved performances, it should actually be taken into account for the assessment of the performance whether the achieved time was achieved by manual stopping or by electronic time measurement. The winning time achieved by Armin Hary in Rome 1960 (example above) of 10.2 seconds corresponds to an assumed electronic time of 10.44 seconds. However, it was achieved on a cinder track and therefore cannot be compared with later performances over 100 meters that were achieved on a plastic track . Likewise, it cannot be compared with times that were achieved at an explicit altitude, such as the times that were achieved in 1968 at the Olympic Games in Mexico City .
Applications in science and technology
Manual stopping is also used in the field of natural sciences or technology if an accuracy of 0.05 to 0.1s is sufficient. This concerns z. B. Many time measurements in biology, chemistry, physics, geography, work technology or mechanical engineering. In contrast, this will not be sufficient in electronics or computer technology, but the prerequisites for electronic time measurement are always given here anyway.
Hand stop in astrometry
Manual time measurements in astrometry are well-documented examples , for example when it comes to measuring star locations , the earth's rotation, sidereal time or the direction of the plumb bob . Although electronic processes have predominated in the first-mentioned areas since around 1980, manual stopping in the latter still makes sense. It is best combined with (semi) automatic time registration .
The simplest and third most precise manual method to date is the eye-to-ear method for measuring star words. The observer quietly counts the beats of the second on a pendulum clock and uses them to estimate the moment when the star crosses the web of threads. Experienced observers achieve average accuracies of around 0.05 seconds.
With mechanical or digital stopwatches with a clever measuring arrangement, 0.02 to 0.04 s can be achieved, for example with astro-geodetic plumbing deviation or azimuth measurements . It is less about the running precision of the stopwatch than about largely eliminating the reaction time of the observer ( personal equation ) through differential measurements .
Impersonal micrometer
The most accurate is the impersonal or recording micrometer , which almost comes close to fully electronic measurements, but is no longer a stop in the strict sense. The observer follows the star moving through the field of vision with a moving thread, whereby the micrometer closes 20-30 electrical contacts. About 0.02 seconds can be achieved per star passage. A similar method is used on the Danjon astrolabe .
Why astronomical time measurements are 5 to 10 times more accurate than manual stops in sports is due to the continuous, surprise-free movement of the stars. In the best case, they disappear for a tenth of a second behind the measuring thread, which is easy to predict. On the other hand, because the unrest in the air causes disturbances in the range of 1–3 "(0.07 to 0.2s), the additional expense of electronic methods is usually only profitable at fixed observatories .
Individual evidence
- ↑ Archive link ( Memento of the original from July 15, 2007 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ Albert Schödlbauer : Geodetic Astronomy Basics and Concepts. de Gruyter, Berlin 2000, ISBN 3-11-015148-0
- ↑ Gottfried Gerstbach: Analysis of personal errors in passage observations of stars. Geoscientific Communication Volume 7, pp.51–102, TU Vienna 1975
- ↑ P.Jackson 1972 right ascensions of FK4-Supp-Stars (Annals of the University Observatory Vienna)
- ↑ M. Firneis / E. Göbel 1985 Observations of right ascensions of selected FK4-stars (A&AS), http://articles.adsabs.harvard.edu//full/1985A%26AS...62..137F/0000139.000. html
