Timegrapher reading explainer

What the three numbers mean

Rate is how fast or slow the watch runs, in seconds per day, in the position it is being measured in. It is the number owners care about and the easiest of the three to adjust.

Amplitude is how far the balance swings, in degrees. It is the health reading. A healthy, fully wound movement usually shows somewhere around 270 to 310 degrees dial up. Falling amplitude means the escapement is receiving less energy than it should: old oil, wear, a weak mainspring or dirt.

Beat error is the asymmetry between the two swings, in milliseconds. It does not affect rate directly, but a large beat error makes a watch harder to start when it is not moving and suggests the hairspring collet is not centered.

The machine hears none of this directly. It listens through a microphone and derives all three from the timing of the noises in each beat. Rate and beat error fall straight out of that. Amplitude does not.

A reading, worked through

A three year old microbrand diver running a Seiko NH35, never serviced. Wound fully, set on the microphone with the lift angle at 53 degrees (Seiko Time Module's published figure for that caliber), left to settle a minute. Dial up it shows +8.0 s/day, 275 degrees, 0.4 ms, and the tool returns: normal and easily regulated, healthy, fine in practice. Now rotate it through the other four positions.

Two numbers matter more than any single line. The mean of the five is (8 + 6 + 2 + 1 − 1) / 5 = +3.2 seconds a day, which predicts wrist performance far better than the dial up figure. The spread, from −1 to +8, is 9 seconds a day, and that is what separates a properly adjusted movement from a lucky one. Vertical positions running 20 to 25 degrees below horizontal is normal, because a vertical pivot carries the balance's weight on its side.

The conclusion: do nothing. Note too that the tool sees one line at a time, so running it five times, once per position, is a more honest use of it than running it once.

Taking a reading you can trust

1. Wind it fully first. A reading at low wind measures the weak end of the mainspring, not the watch.
2. Set the lift angle for your caliber, not the machine's default. This is the single largest source of wrong amplitude figures.
3. Let it settle. Give it 30 to 60 seconds after every position change, and a couple of minutes before trusting an averaged rate.
4. Take all five positions, then read amplitude again at 24 hours. Two readings a day apart tell you about the mainspring; one tells you about a moment.
5. Seat it properly and keep quiet. A loose clamp, an air conditioner or a conversation all reach the microphone.
6. Record what you set. A reading without its lift angle, position and state of wind is not a reading, which is why a figure copied from a forum post is worth nothing.

The mistakes mirror that list: reading a watch straight off the wrist, warm and half wound; comparing amplitude against a figure taken at a different lift angle; and measuring a chronograph with the chronograph running, which loads the train and drops amplitude by design.

The trap in the amplitude number

Amplitude is calculated from the lift angle you tell the machine, which varies by caliber and is commonly around 52 degrees but is not universal. Enter the wrong lift angle and the amplitude reading moves a long way while the watch is unchanged. Look up the figure for your caliber before drawing conclusions, and only compare readings taken with the same setting, position and state of wind.

The relationship is very nearly proportional, so the error is easy to size. A Valjoux 7750 is published at 49 degrees. Measure one on a machine left at its 52 degree default and the reading runs 52 / 49 = 1.06 times high: a genuine 250 degrees displays as 265. The other way round, an NH35 (published at 53) read on a machine set to 49 shows a genuine 270 as 250, which is the figure that sends people to a watchmaker for a service they do not need.

The published values on our lift angle page: ETA 2824-2 and Sellita SW200-1 at 50 degrees, ETA 2892-A2 and Sellita SW300-1 at 51, Valjoux 7750 and Miyota 8215 at 49, Miyota 9015 at 51, Seiko NH35 at 53. Not one is 52, the value most machines ship with.

What to do with a bad reading

A high positive rate with normal amplitude is usually magnetism, and demagnetizing takes minutes. Low amplitude with an erratic trace is a service, not a regulation: regulating a movement with a starved escapement just hides the symptom. Beat error above roughly one millisecond is worth correcting at the next service, and is often free to fix while the movement is already open.

Four decisions are available, in rising order of cost. Prices are indicative US figures before sales tax and move with region and workload.

• Nothing. Rate within about 15 seconds a day, amplitude above 270, beat error under 0.6 ms. A watch at +8 a day gains 56 seconds a week, and plenty of owners just reset on a Sunday.
• Demagnetize. A high positive rate, often 30 seconds a day or far more, with amplitude unaffected. Minutes on a demagnetizer, and the rate falling back confirms it. The threshold is low: ISO 764 asks only that a watch survive 4,800 A/m, about 60 gauss, and laptop lids, speakers and magnetic clasps beat that at close range.
• Regulate. Rate consistently out, amplitude healthy, beat error low. Roughly $60 to $150 at an independent watchmaker. Regulation moves the rate; it does not fix positional spread, which is a separate adjustment.
• Service. Amplitude below about 200 at full wind, a fuzzy or erratic trace, a large drop by 24 hours, or a wide positional spread. Indicative: $250 to $500 at an independent for a three-hand automatic, $350 to $600 at a mainstream Swiss service center, $800 to $1,200 for Rolex or Omega. Our page on service costs covers the range.

What the verdicts do not mean

The tool grades one reading against bench convention, and two of its labels need qualifying. Chronometer grade means a rate inside six seconds a day; it is not a COSC pass. COSC applies ISO 3159 over 15 days, in five positions and three temperatures, to a bare uncased movement, against seven criteria at once. Its rate window is asymmetric, minus 4 to plus 6, so a watch at minus 6 gets a good verdict here and fails there, and the other six criteria constrain consistency in ways one bench reading cannot test. METAS Master Chronometer is stricter again: 0 to plus 5 seconds a day on the fully cased watch, after 15,000 gauss.

Healthy at 270 degrees and above is convention, not a standard: where a manufacturer publishes a figure for its own caliber, that wins. And the whole reading describes a watch on a bench, at room temperature, for a few minutes. Your wrist is warmer and never still, which is why a week of wear against a reference clock remains the honest test: our guide to timing your own watch sets out the method and the accuracy calculator does the arithmetic.

What the machine cannot see

• Anything that is not the escapement. Power reserve, water resistance, gasket condition, whether the date changes at midnight: none of it reaches the microphone. Quartz and Spring Drive have no escapement at all, so an acoustic machine reads nothing from them.
• Free-sprung balances. On the Rolex 3235 or Omega 8800 the rate is set by moving timing weights on the balance rim, not a regulator arm, so easily regulated means a bench job with a specific tool.
• Very high amplitude. Above roughly 320 degrees the impulse pin can strike the back of the fork horn, called knocking, and the rate runs wildly fast. Check the lift angle before anything else.
• Vintage movements. A 1940s or 1950s caliber may never have reached 270 degrees when new, and may have no published lift angle at all. Judge it against its own design, not a modern band, and see our vintage buying guide.
• A watch that is simply unwound. The commonest cause of an alarming amplitude figure is also the cheapest to fix.