Complications  /  Chronograph

Chronograph

Also known as — Stopwatch complication, compteur

An independent seconds train that can be started, stopped and returned to zero without interrupting the running of the watch.

How it works

Timing a short interval with an ordinary watch means noting the seconds hand at the start, noting it again at the end, and subtracting. Astronomers, artillery officers and racing officials could not do better by stopping their watches, because a stopped watch loses the time of day. What they needed was a second hand they could start and stop at will, while the watch itself kept running.

MINHOURSSECrunning secondsthe watch’s own hand,always turningchronograph secondsmoves only after youpress start1 START / STOP2 RESETcrown
How to recognise one: three small dials, a long central seconds hand that stays still until you start it, and two pushers flanking the crown. The counters at three and six accumulate elapsed minutes and hours, because a hand that has gone round three times looks exactly like one that has gone round once. Layouts vary between makers, but three, six and nine is much the commonest.

That is what the dial above shows. The long hand from the centre belongs to the chronograph and does nothing until the top pusher is pressed; the watch’s own seconds live in the small dial at nine. The other two counters accumulate the elapsed minutes and hours, because a hand that has gone round three times looks exactly like one that has gone round once.

301 START/STOP2 RESETthe two controlspress 1column wheelone press, one stepclutch inbrake offthe wheel turnspress 2hammer fallsheart camits lowest point is zero
Pressing 1 steps the column wheel round by one tooth, swinging the clutch into mesh and lifting the brake. Pressing 2 drops the hammer onto the heart cam, which can only come to rest in one position.

Underneath, a chronograph is a second gear train that can be coupled to the movement and uncoupled again. Three things have to happen in order, and one part sequences them. The column wheel is a small castellated wheel, like the top of a chess rook, advanced one step at every press. Levers for the clutch, the brake and the reset hammer rest either on top of a column or drop into the gap between two, so a single turning part decides what happens next. The reset depends on the heart cam, patented by Adolphe Nicole in 1844: a flat hammer falling against a heart-shaped cam can only come to rest in one angular position, and that position is zero.

It is not free. The chronograph draws power from the same mainspring as the escapement, so the rate shifts while it runs, and the mechanism roughly doubles the part count, adds height, and puts two more openings in the case.

Recorded here

Milestones with this mechanism

1913The first wrist chronograph calibreLongines calibre 13.33Z of 1913 was one of the first chronograph movements made small enough for a wristwatch, run by a single push-piece in the crown.Longines1915The first separate chronograph pusherBreitling moved the chronograph push-piece out of the crown and onto the side of the case.Breitling1934The first two-pusher chronographBreitling gave the chronograph a second push-piece, so that stopping and resetting became separate controls.Breitling1936The first serial flyback chronographLongines calibre 13ZN made the flyback a series-production chronograph: one press sent the hand back to zero and started it again.Longines1941The first perpetual chronographPatek Philippe’s reference 1518 of 1941 was the first chronograph with a perpetual calendar made in series.Patek Philippe1969The first high-beat chronographZenith’s El Primero, calibre 3019 PHC, was the first chronograph to run at 36,000 vibrations an hour, fine enough to time a tenth of a second.Zenith1969The first automatic chronograph soldSeiko’s calibre 6139 was the first self-winding chronograph to go on sale, in Japan in May 1969.Seiko1969The first modular automatic chronographHeuer, Breitling, Hamilton-Büren and Dubois Dépraz built Calibre 11 by adding a chronograph module to a thin self-winding movement.Heuer1816The first chronographLouis Moinet’s compteur de tierces of 1816 is the oldest known instrument that could start, stop and return to zero.Louis Moinet1923The first split-seconds wristwatchPatek Philippe movement no. 124824, sold in 1923, is the earliest known split-seconds chronograph wristwatch.Patek Philippe