How to Read an Automatic Watch’s Specs: Beat Rate, Jewels, Accuracy and Power Reserve

October 2, 2026

A movement specification is easier to understand when you know what each number describes. The Miyota 82S7 used in the Carter Farrago Heartmatique is listed at 21,600 vibrations per hour, with 21 jewels, an accuracy range of −20 to +40 seconds per day, and approximately 42 hours of running time.

Miyota calls the 42-hour figure “Running Time.” Carter Farrago’s product pages call it “Power Reserve.” The figures match, although the labels differ.

At a glance

Specification	Miyota 82S7	What it means
Frequency	21,600 vibrations per hour / 3 Hz	Three complete balance oscillations per second
Jewels	21	Jewel bearings, typically made from synthetic ruby
Accuracy	−20 to +40 seconds per day	Miyota’s published rate tolerance
Posture difference	Under 50 seconds	Miyota’s listed figure
Running time / power reserve	Approximately 42 hours	Miyota’s running-time figure; CF pages call it power reserve
Winding	Automatic and hand winding	Miyota lists both; CF product pages list the Heartmatique as automatic

Miyota’s official 82S7 specifications and the Heartmatique product pages list the same core figures, though they use different labels for the 42-hour duration.

What does 21,600 vibrations per hour mean?

Frequency describes how quickly the movement’s balance oscillates. Miyota lists the 82S7 at 21,600 vibrations per hour.

That equals six vibrations per second. Two vibrations make one complete to-and-fro oscillation, so the balance completes three oscillations per second, or 3 Hz. Horopedia’s “Oscillation” entry explains this conversion. Horopedia notes that its English pages are machine-translated from French.

The figure describes the movement’s regulating rhythm. It does not, by itself, tell you how accurately a particular watch will keep time on your wrist.

What do the 21 jewels do?

The 82S7 has 21 jewels. Jewel bearings, typically made from synthetic ruby, are used at selected points in a mechanical movement to reduce friction and wear. See Horopedia’s entries on bearings (jewels) and ruby / jewel for more detail. Horopedia notes that these English pages are machine-translated from French.

The jewel count is a construction detail, not a score of overall quality. A higher number does not automatically mean a movement is more accurate or better made.

How should I read −20 to +40 seconds per day?

Miyota lists the 82S7’s accuracy as −20 to +40 seconds per day and its posture difference as under 50 seconds. The linked Miyota specification sheet provides additional information about its measurement procedure.

The Japan Clock & Watch Association’s accuracy guide explains that catalogue figures are measured under set conditions. It also notes that a mechanical watch’s rate can be affected by factors such as winding state, position, temperature, shock and magnetism, so the rate on the wrist can differ from the catalogue figure.

Carter Farrago’s return policy says that “watch characteristics inherent to a mechanical movement … that fall within stated tolerances” are not eligible for return. See the return policy for the full wording.

What does a 42-hour power reserve mean?

Miyota lists the 82S7’s running time as approximately 42 hours. Carter Farrago’s product pages label the same figure power reserve.

In practical terms, it is the stated running duration from stored energy when the mainspring is wound. Miyota lists the 82S7 as automatic and hand-wound; Carter Farrago’s product pages list the Heartmatique’s winding as automatic.