Reading a timegrapher,
from the trace up

A sixty-dollar timegrapher tells you more about a mechanical watch in thirty seconds than a week of wrist-watching — if you can read it. Most new owners can’t, panic at their first ugly trace, and either overpay a watchmaker or condemn a healthy movement. The machine is simple once you know what it is actually doing.

Last reviewed July 2026 · Independent guide · Not affiliated with timegrapher

What the machine actually does

A timegrapher is a microphone, a clock and some arithmetic. Clamped to the case, it listens to the escapement — each tick is really a cluster of tiny impacts as the escape wheel unlocks, impulses the balance and drops onto the next tooth — and it times those events against its internal reference to microsecond precision. Everything on the screen is computed from those timings plus one assumption you supply: the lift angle.

Rate is the simple one: if ticks arrive slightly early, the watch runs fast, and the dots march upward across the screen; late, and they slope down. The displayed number is that drift extrapolated to seconds per day. Beat error is the asymmetry between the two halves of the oscillation — tick versus tock — displayed in milliseconds and drawn as the vertical gap between the two dotted lines.

Amplitude is the derived one, and the one beginners misread. The machine measures the time between acoustic events within each tick and, using the lift angle — the arc across which the escapement interacts with the balance — computes how far the balance must be swinging. Feed it the wrong lift angle and the timing is real but the geometry is wrong: amplitude comes out tens of degrees high or low while rate and beat error remain trustworthy.

This acoustic method is why the machine has blind spots. A noisy room adds phantom dots. A quartz watch gives it nothing usable. And an escapement whose geometry departs from the classical Swiss lever — the Powermatic 80 family’s synthetic redesign is the famous case — produces sound signatures the arithmetic was never built for, and confidently wrong numbers. The machine is honest about what it hears; it just doesn’t know what it doesn’t know.

Rate: the number everyone starts with

Rate is the headline: seconds per day, positive fast, negative slow. Two principles turn it from a number into a judgement. First, judge against the movement’s own specification, not against zero. A 7S26 at +18 is inside its printed -20/+40 band — healthy. A chronometer-grade movement at +18 has failed. The reading only means something relative to what the calibre promises; our movement pages carry the specs.

Second, one position is an anecdote. Gravity acts on the balance differently in every orientation, so measure dial-up, dial-down, crown-up and crown-down at minimum, note the spread, and think in terms of the average your wrist will actually produce. A movement reading +4 dial-up and +6 crown-down is a gem regardless of grade; one reading +20 and -15 in the same positions will infuriate its owner despite an innocent-looking average — the 6R35 complaint in a nutshell.

The slope’s stability matters as much as its angle. A healthy trace holds its slope steadily; a rate that wanders over thirty seconds — the line bending, drifting, stair-stepping — indicates the escapement is not delivering consistent impulses, which is a service symptom no regulation will cure.

And the golden rule of dramatic rates: a watch that abruptly starts gaining minutes a day, with clean traces, is magnetised until proven otherwise. Phones, laptops, bag clasps. A demagnetiser costs less than lunch and resolves it in five minutes — always before deeper diagnosis, never after.

Amplitude and beat error: the health numbers

Amplitude is the balance’s swing in degrees, and it functions as the movement’s blood pressure. A serviced movement at full wind typically swings roughly 250–300 degrees dial-up, dropping 20–40 degrees in vertical positions — normal, since the balance pivots carry weight differently on their sides. Below about 200 at full wind, something is wrong: dried oils, dirt, a tired mainspring, worn pivots. Above about 315, the overbanked condition called knocking — the balance swinging so far it strikes the other side of the escapement — which is its own fault, often heard as a galloping rate.

Amplitude is also where honest mistakes concentrate. Test at half-wind and you will see low amplitude that is merely an emptying mainspring — wind fully and re-test. Set the wrong lift angle and the number is fiction — set it per calibre. And compare like with like: dial-up figures against dial-up figures. A single low reading proves nothing; a full-wind, correct-angle, dial-up reading under 200 proves a service is due.

Beat error is the humbler number: the tick-tock asymmetry in milliseconds. Under 0.5ms is well adjusted; up to about 1ms is common and harmless in daily use; beyond that, the movement wastes energy restarting each swing asymmetrically, self-starting suffers, and adjustment is worthwhile — on most modern movements a simple job with a moveable stud carrier, on vintage fixed-stud calibres a fiddlier one best bundled into a service.

One habit ties the three numbers together: log them. A movement’s absolute figures matter less than their trend — amplitude sliding 30 degrees over two years is an oil-life story told early, and a rate that needed re-regulating twice in a year is whispering about wear. The machine’s cheapest gift is a baseline.

Using it on watches you are about to buy

For a buyer, thirty seconds on a timegrapher converts a seller’s “runs great” into one of six rows. The first three cost little or nothing to resolve; the last three reprice the watch by the cost of a service or more. Sellers who own machines increasingly post screenshots — read them with the caveats above, especially the single-position problem and, on Powermatic-family movements, the escapement artefact.

Chronographs get one extra step: trace with the chronograph stopped, then running. A modest amplitude drop when engaged is physics — the movement is driving extra wheels. A collapse, or a rate that lurches, means the chronograph works are dragging, and chronograph services are the expensive kind. The 7750 page covers the full pre-purchase routine.

Phone apps deserve their honest sentence: they use the same acoustic principle through vastly worse microphones, and they are usable for rate on a quiet desk, marginal for beat error, and not to be trusted for amplitude. As a free first look they beat nothing; as a basis for buying decisions, the sixty-dollar machine earns itself back on the first negotiation.

And the authentication bonus: the machine reads beat rate directly, and beat rate identifies movement families. A claimed 28,800 vph Swiss automatic tracing at 21,600 has the wrong movement inside; a claimed mechanical ticking once per second is quartz. The timegrapher was built to measure health, but it incidentally audits honesty.