What is a Chronograph?
A chronograph is a device used to measure, and to produce visual or permanent records of, the duration of events lasting from fractions of a second up to 12 hours. Chronographs that are used to measure and give a visual indication of short time intervals are often called chronoscopes.
Chronographs fall into two general classifications: watch chronographs, which are entirely mechanical in action; and electromagnetic, electronic, cathode ray, and flashing chronographs, each of which uses a highly accurate crystal-controlled clock or a marine chronometer as a time base. The first type is widely used by engineers, time-and-motion-study experts, doctors, and judges of many sporting events. The second group is more applicable in the scientific and military fields, where extremely precise time determinations are required, and is also used for precise timing of some sporting events. watch-type chronographs have hour, minute, and second hands that show conventional time.
Chronographs that do not indicate the time of day are referred to as timers. In addition to the usual clock hands, chronographs have an independent second hand, called the chronograph hand. It revolves about the dial center and extends almost to its edge. Push buttons are used to start, stop, or return the chronograph hand to zero. Sixty divisions of one second each, subdivided into fifths or tenths, are engraved around the edge of the dial. Chronographs have a small dial usually located on the main dial near the position of the 3 on an ordinary clock dial. This small dial has 30 divisions, and a hand on it advances one division for each revolution of the chronograph hand, thus recording elapsed time up to 30 minutes. Many chronographs also have dials near the 6 position that permit recording elapsed time up to 12 hours. Split-second chronographs have two chronograph hands that can be operated independently to allow for the timing of overlapping events.
Prior to use, all chronograph hands are set at zero by pressing a
button. When the event being timed begins, the button that starts the
chronograph hand is pushed. When the event terminates, the button is
pushed again to stop the hand, and the time is shown. If the action is
interrupted (rather than terminated) the hand can be restarted when the
action resumes, so that only the actual time of the event is monitored.
The more accurate chronographs incorporate means of reducing errors in observation and in the rate of the time base and make possible readings to much smaller fractions of a second.