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Tachometer or Tachymeter, Telemeter, Third Wheel, Time Zones, Tonneau, Tourbillon, Train, Tritium
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Tachometer or Tachymeter
Function measuring the speed at which the wearer runs over a given distance. The tachometer scale is calibrated to show the speed of a moving object, such as a vehicle, over a known distance. The standard length on which the calibration is based is always shown on the dial, e.g. 1,000, 200 or 100 meters, or—in some cases—one mile. As the moving vehicle, for instance, passes the starting-point of the measured course whose length corresponds to that used as the basis of calibration, the observer releases the chronograph hand and stops it as the vehicle passes the finishing point. The figure indicated by the hand on the tachometer scale represents the speed in kilometers or miles per hour.
A scale on the dial, flange, or bezel of a chronograph that, in conjunction with the second hand, gives the speed of a moving object. A tachymeter takes a value determined in less than a minute and converts it into miles per hour. For example, a wearer could measure the time it takes a car to pass between two mile markers on the highway. When the car passes the second marker, the second hand will be pointing to the car's speed in miles per hour on the tachymetric scale. |
Telemeter
By means of the telemeter scale, it is possible to measure the distance of a phenomenon that is both visible and audible. The chronograph hand is released at the instant the phenomenon is seen; it is stopped when the sound is heard, and its position on the scale shows, at a glance, the distance in kilometers or miles separating the phenomenon from the observer. Calibration is based upon the speed at which sound travels through the air, viz, approximately 340 meters or 1,115 feet per second. During a thunderstorm, the time that has elapsed between the flash of lightning and the sound of the thunder is registered on the chronograph scale. |
Third Wheel
Wheel positioned between the minutes and seconds wheels. |
Time Zones
The 24 equal spherical Iunes unto which the surface of the Earth is conventionally divided, each limited by two meridians. The distance between two adjacent zones is 15~ or 1 hour. Each country adopts. the time of its zone, except for countries with more than one zone. The universal standard time is that of the zero zone whose axis is the Greenwich meridian. |
Tonneau
Particular shape of a watchcase, imitating the profile of a barrel, i.e. with straight, shorter, horizontal sides and curved, longer, vertical sides. |
Tourbillon
Device invented in 1801 by A. L. Breguet. This function equalizes position errors due to changing positions of a watch and related effects of gravity. Balance, balance spring and escapement are housed inside a carriage, also called a cage, rotating by one revolution per minute, thus compensating for all the possible errors over 360. Although this device is not absolutely necessary for accuracy purposes today, it is still appreciated as a complication of high-quality watches.
A technically demanding device to compensate for the interference of gravity on the balance and thus improve a watch's rate. In a tourbillon (from the French word for whirl), the entire escapement is
mounted on an epicyclic train in a "cage" and rotated completely on its axis over regular periods of time, usually once a minute. Today this superb technical delicatesse is a sign of the highest quality.
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Train
All the wheels between barrel and escapement. |
Tritium
Slightly radioactive material that collects light energy and is used to coat hands, numerals, and hour markers on watch dials in order to make reading the time in the dark possible. Watches bearing tritium must be marked as such, with the letter T on the dial near 6 o'clock. It is gradually being replaced by nonradioactive materials such as Superluminova and Traser due to medical misgivings and expected governmental regulation of its use. |
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