Chronograph

A chronograph is a watch that contains a stopwatch. Alongside the normal running time display, an independent set of hands can be started, stopped and returned to zero on demand, usually by two pushers flanking the crown. The elapsed seconds are read from a large central hand, with accumulated minutes and often hours shown on subdials. Everything the user does comes down to three presses: start, stop, reset. The engineering underneath decides how those presses feel, what the watch costs to service, and whether you can safely leave it running.

How to read one

The busiest hand on a chronograph dial is usually the one that does nothing. The large central sweep hand belongs to the stopwatch and sits still until you start it, while the small subdial that ticks continuously is the running seconds, telling you the watch itself is alive. New owners routinely reverse the two and conclude the watch has stopped.

The other subdials accumulate. A 30 minute counter is the most common, paired with a 12 hour counter on three-register layouts such as the Valjoux 7750, which gives 60 seconds, 30 minutes and 12 hours. Two-register chronographs drop the hour counter. Some counters jump instantly at the minute, others creep round continuously, and reading a creeping counter means taking the lower value: if it sits between 7 and 8, seven minutes have elapsed.

How it works

The chronograph train is coupled to the going train by a clutch. A lateral clutch swings an intermediate wheel into mesh with the driving wheel, a simple and traditional arrangement whose weakness is a small jump of the seconds hand at start-up. An oscillating pinion, used in the 7750, tilts a single pinion into mesh instead and engages more directly. A vertical clutch presses two friction surfaces together, which starts the hand cleanly and allows the chronograph to be left running without measurable extra wear.

Control comes from either a column wheel, a rotating pillar-topped wheel that steers levers into position, or a cam and lever system. Column wheels are more expensive to make and give a smoother pusher feel; cam systems are robust, adjustable with eccentric screws, and used in some of the most successful chronographs ever built. Reset is the elegant part: hammers drop onto heart-shaped cams on each chronograph arbor and slide down the curve until the hammer face sits flat, which happens at exactly one position, zero.

Construction also splits into integrated and modular. An integrated chronograph is designed as one movement. A module is a chronograph mechanism stacked on top of a plain base caliber, which is cheaper to build but adds height and often puts the pushers slightly off the crown axis. A flyback chronograph adds the ability to reset and restart in a single press, and a rattrapante or split-seconds chronograph adds a second central hand for timing two events that begin together. Our guide to chronographs works through each variation.

A short history

Louis Moinet built a high-frequency timing instrument in 1816, and in 1821 Nicolas Rieussec patented a device that marked elapsed time by dropping ink onto a rotating dial. That is where the name comes from: chronograph means time writer, a description that stopped being literal almost immediately. Early wrist chronographs used a single pusher for all three functions; Breitling separated reset onto a second pusher in the 1930s, giving the layout still used today. Automatic chronographs arrived in 1969 from three directions at once, including the Zenith El Primero at 36,000 vph, and the cam-switched 7750 followed in the mid 1970s and went on to underpin most Swiss chronographs since.

Living with one

A chronograph is the most expensive common complication to maintain. A full service runs indicatively 700 to 1,200 US dollars before sales tax against 250 to 500 for a plain three-hand automatic, because there are two mechanisms to strip and adjust. Figures are indicative and vary by caliber and workshop; see what a service costs.

Two practical rules. Do not press the pushers underwater unless the manufacturer says they are rated for it, since most are not screw-down and a pushed stem breaks the seal: our water resistance guide explains why. And do not force a reset while the chronograph is running unless the watch is a flyback, because on a conventional mechanism the reset lever is blocked for a reason.

Common misconceptions

A chronograph is not a chronometer. The words share a root, they sit next to each other in catalogs, and they mean entirely different things. A chronograph is a function: a stopwatch. A chronometer is a certification of timekeeping precision awarded after testing. A watch can be either, both or neither, and the presence of pushers tells you nothing about how accurately the watch runs.

The other frequent confusion is with a tachymeter. That scale, printed around many chronograph bezels, is not part of the chronograph at all. It is a fixed conversion scale that turns an elapsed time read off the chronograph into a speed or a rate per hour, and our tachymeter calculator does the same arithmetic. Finally, leaving a chronograph running all day is a real question only on a lateral clutch, where the meshed wheels wear; on a vertical clutch it is a designed-for condition. If you want the function rather than the look, what a chronograph is actually for is the honest starting point.