Question 1

What is a timegrapher?

Accepted Answer

A timegrapher is an instrument that measures the performance of a mechanical watch by listening to its tick sounds. It calculates four key metrics: rate (seconds gained or lost per day), beat error (timing difference between tick and tock in milliseconds), amplitude (balance wheel swing arc in degrees), and BPH (beats per hour, the movement’s frequency).

Question 2

What is beat error in a watch?

Accepted Answer

Beat error is the timing difference between the tick and tock of a mechanical watch’s escapement, measured in milliseconds. Under 0.5 ms is excellent, under 1.5 ms is acceptable for daily wear, and over 2.5 ms can cause the watch to stop. It is corrected by adjusting the pallet fork’s position relative to the balance wheel.

Question 3

What is amplitude in a mechanical watch?

Accepted Answer

Amplitude is the arc in degrees through which the balance wheel swings on each beat. A healthy mechanical watch shows 220–310° when fully wound. Low amplitude (below 200°) suggests the mainspring needs winding, the movement needs servicing, or there is excess friction in the train.

Question 4

What is a good rate for a mechanical watch?

Accepted Answer

The COSC chronometer standard requires −4 to +6 seconds per day. For everyday mechanical watches, ±15 s/d is acceptable. Beyond ±30 s/d usually warrants regulation. Rate varies by position, so testing in multiple orientations gives a fuller picture.

Question 5

What causes a mechanical watch to run fast?

Accepted Answer

Common causes of a fast rate include: magnetisation of the movement (especially the hairspring), hairspring coils sticking together, an incorrectly set regulator index, or a worn escapement. Demagnetising is the easiest first step and safe to do at home with a demagnetiser.

Question 6

What does BPH mean on a timegrapher?

Accepted Answer

BPH stands for Beats Per Hour — the frequency of the mechanical watch movement. Common values are 18,000 (5 Hz), 21,600 (6 Hz), 28,800 (8 Hz), and 36,000 BPH (10 Hz). You must set the correct BPH on the timegrapher to match your movement for accurate amplitude readings.

Question 7

Is a browser-based timegrapher as accurate as a hardware timegrapher?

Accepted Answer

For rate and beat error, a browser-based timegrapher with a good microphone can match hardware accuracy — the underlying algorithm is the same. The key difference is the microphone: hardware timegraphers use a contact mic clipped to the watch case for a cleaner signal. A laptop mic works well in a quiet room. For best results use a dedicated clip-on contact microphone (~$15) connected to your computer.

Question 8

What is lift angle and why does it matter for timegraphers?

Accepted Answer

The lift angle is a fixed mechanical property of a specific watch movement — the arc through which the pallet fork lifts the balance wheel on each beat. It typically ranges from 49° to 53°. The timegrapher uses it to convert pulse timing into amplitude in degrees. The wrong lift angle gives inaccurate amplitude, though rate and beat error are unaffected.

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