The Numbers Behind the Watch: A Beginner's Guide to Understanding Time Grapher Results

Every watch we sell at Crown Vintage is tested on the Witschi WAIO before it reaches a new owner. The results appear as a small cluster of numbers on a printed slip, and while they are second nature to anyone who has spent time around mechanical watchmaking, they can look completely opaque to everyone else. Rate. Amplitude. Beat error. Positional spread. If you have ever wondered what any of that actually means, this is for you. No prior knowledge required.

What Is a Time Grapher, and Why Does It Matter?

A time grapher is an instrument that listens to the heartbeat of a mechanical watch and translates it into a set of measurable data points. Every time a mechanical watch ticks, a small component inside the movement called the escapement makes a sound. This sound occurs with extraordinary regularity, typically between five and ten times per second depending on the movement. A time grapher records those sounds, analyses the precise intervals between them, and uses the differences between what it hears and what it expects to calculate how the watch is performing.[1]

The Witschi WAIO is one of the most sophisticated instruments of this type available. It is an all-in-one device designed specifically for use in watch retail environments, combining timing measurement with water resistance testing and demagnetisation in a single unit.[2] Its measurement algorithms are built to the same standards used by Swiss manufacturers and service centres, which means the data it produces is genuinely meaningful, not decorative.

Why does this matter for a vintage watch buyer? Because a mechanical watch does not keep the same time in every situation. The oils inside the movement age. Components wear. Pivots accumulate microscopic amounts of dirt. All of these things affect performance, and the time grapher is one of the only ways to see them objectively. A watch may look pristine and yet perform erratically. Another watch may show signs of wear and yet keep exceptional time. The numbers do not lie in the way that appearances sometimes do.

The Heartbeat Explained: What the Movement Is Actually Doing

Before getting into the specific measurements, it helps to understand what is happening inside the watch. At the centre of every mechanical movement is a component called the balance wheel, a small weighted wheel that swings back and forth on a spring. This oscillating motion is what regulates the release of energy from the mainspring and ultimately what makes the hands advance at the correct rate.[1]

Each complete back-and-forth swing of the balance wheel is called an oscillation. Half of that swing, from one turning point to the other, is called a vibration. Most vintage watches run at either 18,000 or 19,800 vibrations per hour, while many movements from the 1960s onwards were made to run at 21,600 or even 28,800. Each vibration produces one of those characteristic tick sounds. The time grapher measures the gap between those ticks with extreme precision.[1]

This matters because two things can go wrong with that rhythm. The balance wheel can swing too much or not enough, which is what amplitude measures. And the ticks can be spaced unevenly, which is what beat error measures. Both tell you something important about the health of the movement, independently of the rate.

Why Position Matters: Testing in Four Orientations

Here is something most people never think about: a mechanical watch does not simply sit in one position. On a wrist, it spends time lying flat, hanging vertically with the crown pointing left or right, tilted at odd angles, and occasionally face down. In every one of those positions, gravity acts on the balance wheel and the gear train slightly differently. A well-serviced movement with properly centred components should run at very similar rates in all positions. A movement that needs attention will show inconsistencies.[1]

This is why the Witschi WAIO tests mechanical watches in four separate positions.[2] By recording the rate, amplitude, and beat error in each orientation, the instrument builds a picture of how consistently the movement performs regardless of how the watch is worn. The spread between the best and worst positions, sometimes referred to as positional variance, is one of the most revealing indicators of overall movement health.

A watch that runs at plus six seconds per day when lying flat but suddenly drops to minus fifteen seconds per day when worn with the crown pointing down is telling you something. It is not just telling you that it needs regulating. It is telling you that there is likely an underlying issue in the regulation system or the pivots that needs a trained watchmaker's attention. No amount of regulator adjustment will fix positional variance caused by worn components.

Rate: What the Watch Says About Time

The first number most people look at is the rate, expressed in seconds per day. A positive number means the watch is running fast. A negative number means it is running slow. Zero would mean perfect accuracy, though no mechanical watch consistently achieves this in practice.

Witschi's own published guidelines indicate that an acceptable rate for a standard men's mechanical watch is between minus five and plus fifteen seconds per day.[1] A chronometer-grade movement, which has been individually certified to a tighter standard, is expected to achieve between minus two and plus six seconds per day.[1] These figures assume the movement is fully wound and measured under standard conditions.

In a vintage context, rate performance has to be interpreted carefully. A movement that has recently been serviced and correctly regulated should fall comfortably within the acceptable range. A movement that has not been serviced for many years may still keep good time, but the rate alone does not tell the whole story. The amplitude and beat error figures are equally important parts of that picture.

Amplitude: The Swing of the Balance Wheel

Amplitude is the measurement of how far the balance wheel swings on each oscillation. It is expressed in degrees, because the balance wheel is rotating through an arc. Specifically, it is the angle measured from the wheel's resting position to the furthest point of its swing.[1]

Think of it like a pendulum on a grandfather clock. A pendulum swinging in a wide arc has a lot of energy. One barely moving has very little. The balance wheel works on the same principle. More swing means the movement is well-wound and well-lubricated. Less swing means something is impeding it, whether that is dried oil, a worn pivot, or simply a depleted mainspring.

For a healthy, fully wound men's wristwatch, Witschi's reference values indicate an amplitude of between 250 and 330 degrees when the watch is measured in a horizontal position, that is, lying flat dial up or dial down.[1] When the watch is placed vertically, the expected range drops slightly, to around 220 to 270 degrees, because gravity now acts across the oscillation rather than parallel to it.[1]

Crucially, amplitude decreases gradually as the lubricating oils inside the movement age.[1] This is one of the reasons watchmakers recommend servicing mechanical movements on a regular cycle. The oils do not simply disappear; they migrate, thicken, and eventually lose the properties that allow the moving parts to run freely. When amplitude drops, it is often the first visible sign of this process. A vintage watch showing an amplitude consistently below 200 degrees in horizontal positions is almost certainly overdue for attention, regardless of how convincing the rate figure looks.

Beat Error: When the Tick and the Tock Are Not Equal

Beat error is perhaps the least intuitive of the measurements, but it is worth understanding because it can reveal a specific and fixable problem that affects accuracy and long-term reliability.

When the balance wheel oscillates, it swings in both directions alternately. Each direction produces one beat: first the tick, then the tock. In a perfectly adjusted movement, the time elapsed between the tick and the tock should be exactly equal to the time elapsed between the tock and the next tick. The balance wheel is swinging symmetrically around its resting position.[1]

Beat error measures how far from symmetric that oscillation actually is. It is expressed in milliseconds. If one half of the swing takes slightly longer than the other, the ticks and tocks become uneven. The balance wheel is spending more of its arc on one side than the other.[1]

Witschi's published benchmarks indicate that a beat error of between 0.0 and 0.5 milliseconds is acceptable for a standard men's watch.[1] A beat error approaching or exceeding 2.0 milliseconds is considered high and will typically manifest as erratic rate performance, particularly between positions. High-quality movements include a dedicated adjustment for setting beat symmetry, and a trained watchmaker can usually correct this without a full service, provided the movement is otherwise in good condition.[1]

The reason beat error matters practically is that it directly affects positional variance. A movement with high beat error will tend to show a large spread between its best and worst positions, because the asymmetric swing means the movement is more susceptible to gravitational disruption in certain orientations. Fixing the beat error often narrows that spread significantly.

How the Four Measurements Work Together

Looking at rate, amplitude, beat error, and positional spread in isolation only tells part of the story. It is the relationship between all four that gives a genuine picture of a movement's condition.

A movement showing a rate of plus eight seconds per day across all four positions, an amplitude of around 275 degrees in horizontal positions, a beat error of 0.2 milliseconds, and a positional spread of less than ten seconds between the best and worst positions is performing very well. The rate is within the acceptable range, the amplitude tells you the movement has good energy and adequate lubrication, the beat error is tight, and the consistency across positions confirms that the regulation system and pivots are in good order.

Contrast that with a movement showing acceptable rate in one or two positions but swinging wildly in others, combined with a falling amplitude and a beat error above 1.5 milliseconds. That picture suggests a movement that is functioning but requires service. The rate may look passable, but the underlying condition is not what it should be.

This is why at Crown Vintage we run the Witschi WAIO on every mechanical watch we handle and include the data in condition reports. The numbers reflect how the watch actually performs across realistic wearing conditions, not just in one convenient test position with a freshly wound mainspring.

Final Thoughts

A time grapher does not pass or fail a watch. It gives you information. Understanding what that information means transforms the numbers from an abstract printout into a genuinely useful guide to the condition and performance of the movement inside the watch you are considering. Rate tells you how fast or slow the watch is running. Amplitude tells you how much energy the movement has and how well the lubricants are doing their job. Beat error tells you whether the oscillation is symmetric and the movement properly adjusted. Positional spread tells you how consistently those figures hold up when gravity changes the equation.

The Witschi WAIO produces all four data points across four separate positions, making it one of the more comprehensive instruments available for point-of-sale and pre-sale testing. When you see those numbers in a Crown Vintage condition report, they are not there to impress or to complicate the purchase decision. They are there because we believe honest information leads to better outcomes for everyone involved.

References

1. Witschi Electronic Ltd. Training Course: Measuring Technology and Troubleshooting for Watches. Document Nr. 71.1010D35e, Rel. 1.2, October 2016. Witschi Electronic Ltd, Büren a.A., Switzerland.

2. Beco Technic. WAIO Witschi All-in-One Watch Testing Device, Product No. 313442. beco-technic.com. Accessed April 2026.