Why an Automatic Watch Sweeps Instead of Ticking

Look at a quartz watch and the seconds hand jumps once a second. Look at an automatic and it seems to glide. That glide is one of the quickest ways to tell a mechanical watch from a battery one, and it comes down to a single number: the beat rate.

It isn't really a sweep

The seconds hand of an automatic is still ticking, just very fast. The balance wheel swings back and forth and, each time, the escapement lets the gears advance a tiny step. Several small steps a second look like a smooth sweep to the eye.

What the numbers mean

Beat rate is quoted in vibrations per hour (vph) or in hertz (Hz). One hertz is two vibrations a second.

• 18,000 vph (2.5 Hz): 5 steps a second. Common on vintage watches. A visibly stepped sweep.
• 21,600 vph (3 Hz): 6 steps a second. Used by many robust modern calibres, including the Miyota 82S5 in our field watches and Seiko's NH35.
• 28,800 vph (4 Hz): 8 steps a second. The modern Swiss standard, used by the Sellita SW200-1 in our Elemental and Air Force. A noticeably smoother sweep.
• 36,000 vph (5 Hz): 10 steps a second. Rare, found on a few high-beat calibres, and the smoothest of all.

Is a faster beat better?

Partly. A faster balance is less disturbed by knocks and movement, which can help stability, and it looks smoother. But it uses energy faster, which can shorten the power reserve, and it puts more wear on the escapement. A well-made 21,600 vph movement can keep excellent time. Beat rate is one factor, not a quality ranking.

What about quartz that sweeps?

A few battery watches have a sweeping hand, and some hybrid movements glide perfectly smoothly. So a sweep is a strong hint of a mechanical watch, not absolute proof. The caseback and the specifications will tell you for sure.

More: how an automatic watch works and Sellita SW200 vs Seiko NH35 vs Miyota.