Timegrapher

Specification

Technical parameters

Overview

A timegrapher listens to the watch through a microphone or a clip-on sensor and prints a trace of each tick, comparing them against a reference oscillator. From those intervals it derives the three numbers that matter: rate in seconds per day, amplitude in degrees, and beat error in milliseconds.

Lift angle has to be entered correctly or the amplitude reading is meaningless. Lift angle is a property of the escapement geometry, typically between 38° and 52° for a Swiss lever, and the timegrapher uses it to convert the time the balance spends in impulse into a rotation angle. Get it wrong and every amplitude figure is systematically wrong.

Beat error is the asymmetry between the two halves of an oscillation — how far off centre the impulse happens. It is set by the position of the hairspring stud relative to the impulse jewel, not by the regulator. A beat error above about 1 ms means the balance is being impulsed unevenly, and no rate adjustment will make that watch run well.

What matters about it

• Reports rate, amplitude and beat error together
• Lift angle must be entered to read amplitude correctly
• Beat error is a mechanical fault, not a rate problem
• Trace quality reveals knocking, rebanking and noise
• Multi-position measurement is the real diagnostic

Practical notes

• Look up the lift angle before measuring; guessing makes amplitude useless.
• Measure in at least three positions — a single dial-up reading hides most faults.
• Fix amplitude before rate, and beat error before either.
• A noisy or doubled trace means a mechanical problem, not a bad instrument.

Compatible with