Complication · Timing
Chronograph Scales — Tachymeter, Telemeter and Pulsometer
VerifiedGraduated scales printed on a chronograph dial or bezel that convert an elapsed-time reading directly into a rate, distance or pulse-rate figure, without requiring the wearer to do the arithmetic themselves.
Definition
Graduated scales printed on a chronograph dial or bezel that convert an elapsed-time reading directly into a rate, distance or pulse-rate figure, without requiring the wearer to do the arithmetic themselves.
Historical origin
These scales developed alongside the chronograph itself from the nineteenth century onward, as the mechanism's ability to time short intervals accurately made it useful for practical calculations in trades such as medicine, artillery ranging, and later motoring; specific named scales (tachymeter, telemeter, pulsometer) became standard printed features of chronograph dials through the twentieth century.
How it works
A tachymeter scale is calibrated so that, when the chronograph seconds hand is started at the beginning of a measured distance (commonly one mile or one kilometre) and stopped at its end, the hand's position against the scale reads directly as a speed (units per hour); the scale is simply a graphical division of 3,600 by the elapsed seconds, printed in advance so no calculation is needed.
A telemeter scale converts elapsed time between seeing an event (such as a flash) and hearing its associated sound into a distance, using the known speed of sound; the wearer starts the chronograph at the visual cue and stops it at the audible one, reading distance directly off the scale.
A pulsometer scale is calibrated for a fixed number of pulse beats (typically 15, 20 or 30) rather than a full minute; the wearer starts the chronograph, counts the specified number of beats, stops it, and reads the patient's pulse rate directly, letting a shorter and more comfortable count stand in for a full sixty-second count.
All three scales rely on nothing more than the chronograph's ordinary elapsed-seconds measurement; the scale itself adds no mechanical complexity to the movement and is purely a printed dial or bezel feature.
Pocket watch context
Pulsometer-scale chronograph pocket watches ('doctor's watches') were a recognised medical instrument from the late nineteenth century onward; tachymeter and telemeter scales appear on period chronograph pocket watches aimed at motoring, sport and artillery use.
Wristwatch context
The tachymeter scale, usually printed on the bezel, remains one of the most common features of modern sport and racing chronographs; telemeter and pulsometer scales are less common today but still produced, particularly on watches marketed with a vintage or medical theme.
Identification
- A numbered scale running around the dial's outer edge or on a fixed or rotating bezel, distinct from the ordinary minute/second track
- Tachymeter scales are numbered in units of speed (e.g., 60 to several hundred) and decrease as elapsed time increases
- Pulsometer scales are usually labelled with the base count used (for example 'Gradué pour 30 pulsations') near the scale itself
Servicing notes
The scale itself requires no servicing, but its usefulness depends entirely on the chronograph mechanism underneath returning to zero accurately and running at the correct rate; a chronograph with a mistimed reset will make any printed scale read incorrectly, so scale accuracy should be checked only after the chronograph mechanism itself has been serviced and verified.
General guidance only. Complicated mechanisms should be assessed and serviced by a qualified watchmaker or clockmaker specialist, not adjusted at home.
Background
A tachymeter is a scale inscribed around the rim of an analog watch with a chronograph to conveniently compute the frequency in inverse-hours of an event of a known period. The function performs a calculation of rate based on elapsed time, where spacings between marks are proportional to 1/t. To measure speed with a tachymeter, the chronograph is started at a marker of known distance and the speed is read from the scale when the seconds hand reaches the next marker.
Users can calculate speed in units per hour regardless of the distance unit, such as kilometres or miles, provided the same unit is used throughout. Standard tachymeter scales work for events lasting 60 seconds or less; specialised versions allow longer durations or lower speeds.
Written from the encyclopedia entries listed under Sources; each statement was checked against the cited text.
Construction and action
- The scale can be printed on the dial or inscribed on a rotating, indexed bezel.
- Calculations follow the mathematical formula T equals 3600 divided by t, where T is the scale value and t is the time in seconds.
- Rotating bezels allow users to align indices with the second hand to measure average speed over longer distances.
Photographs
Photographs are illustrative examples of the type, not necessarily the exact object described. Verify details against the source file page.
Sources & references
- Tachymeter (watch), Wikipedia (English), retrieved 2026-10-28 (text CC BY-SA 4.0)
- de Carle, D., Complicated Watches and Their Repair
- Britten, F. J., Old Clocks and Watches and Their Makers
Where sources disagree, the disagreement is stated rather than resolved silently.