Chronograph

"A chronograph (more properly chronoscope). A watch with hands showing the hours, minutes and seconds, together with a mechanism controlling a chronograph-hand mounted in the centre of the dial.

By the operation of push-pieces, the chronograph-hand can be set in motion, stopped and returned to zero. It completes one revolution per minute; a minute-counter hand (U. S. A. minute-register hand) counts the revolutions, i.e. the minutes, usually up to 30." (Berner)

"A watch indicating hours, minutes and seconds combined with a mechanism whose hand can be started, stopped and returned to zero on demand to measure a duration to one fifth, tenth or even hundredth of a second. Subcounters for the minutes and hours (usually 30 minutes and 12 hours) totalise the number of revolutions by the Chronograph hand. The accuracy of these recorded times can only be guaranteed if the chronograph has satisfied the criteria of the "chronometer" label.

The first chronographs deposited drops of ink on their dial; this no longer being the case, strictly speaking a chronograph should be called a chronoscope." (FHH)

Asthmometer

"Chronograph or sports counter whose dial includes an asthmometer scale indicating the number of respirations per minute. Usually calibrated for 15 respirations, the chronograph hand is stopped after the patient's 15th respiration; the dial gives the number of respirations per minute." (FHH)

Pulsometer

"A Chronograph or sports counter whose dial includes a pulsometric scale to measure the number of heartbeats per minute. Usually calibrated for 15 or 30 beats, the hand is stopped at the patient's 15th or 30th heartbeat; the dial indicates the frequency per minute." (FHH)

Split-seconds chronograph (Rattrapante)

"Split-seconds chronograph. A chronograph with two push-pieces and a “split” seconds hand, i.e. two superimposed centre seconds hands: the ordinary chronograph-hand and the fly-back hand. It is used for timing several phenomena that start simultaneously but are of different duration. At the end of the first phenomenon, the fly-back hand is stopped, and the duration of the phenomenon can be read off on the dial; the fly-back hand is then made to overtake the first hand and continues to move with it. At the end of the second phenomenon, the fly-back hand is stopped again, and the duration is read off on the dial, and so on. After the last phenomenon, the two hands can be stopped and returned to zero. One of the push-pieces controls the, fly-back hand alone, while the other controls both the hands." (Berner)

Tachometer / Tachymeter

"Instrument for measuring speed. In watchmaking, a timer or chronograph with a graduated dial on which speeds can be read off in kilometres per hour or some other unit." (Berner)

Telemeter

"A chronograph or subdial featuring a telemeter scale with which to measure the distance between an event and an observer based on the speed of sound." (FHH)

Associated terms

Column / Pillar wheel, The wheel which governs the start, stop and return to zero functions of the chronograph mechanism. Often associated to high quality or vintage chronographs.

Eccentric, A piece turning about an axis that is not the concentric axis. An eccentric screw, pin, arbor, plug often used in chronographs which act as adjustable banking-stops.

Fly-back / Retour au vol, A function by which the chronograph hand can be reset to zero and immediately started again by pressing once on the start button and releasing it.

Heart piece / heart shaped cam fixed to the arbor of the chronograph-counter hands to return to zero the hands when acted upon by the hammers.