Hairspring: Watch Timegrapher

One upfront purchase. No subscription. Measure rate, beat error, and amplitude — then run it again: Hairspring tells you whether the two readings agree.

Hairspring is a serious iPhone timegrapher for mechanical watches. It measures rate, beat error, and amplitude — and tells you when the signal cannot support a trustworthy answer.

MEASURE TWICE, SEE IF THEY AGREE A single number is not proof. Measure the same watch again and Hairspring compares the two runs, includes the statistical uncertainty of each rate, and states whether the readings agree. Save the verification in History and its PDF report.

WHAT IT REPORTS • Rate in seconds per day, with statistical fit uncertainty • Automatic detection of common beat rates from 14,400 to 36,000 bph • Beat error from the escapement's high-frequency signature • Live amplitude as a range, reflecting what an acoustic measurement supports • Live timing graph and six-position measurements • Local history, drift and session comparisons • PDF measurement receipts for sharing with a watchmaker

BUILT TO WITHHOLD BAD DATA Too much scatter, an implausible result, or timing too disturbed to number the beats produces a clear explanation and a suggested fix — not a plausible-looking number. The analysis band was chosen by a pre-registered experiment whose acceptance criteria were written before the data was collected; the first failed attempt remains documented.

ONE PURCHASE, NO SUBSCRIPTION Everything is included with your purchase: every measurement, position run, history entry, comparison, PDF report, and optional raw capture. No subscription, no in-app purchase, no account, no sign-in, no ads, and no analytics.

PRIVATE BY DESIGN Live audio is analyzed on your iPhone and is never uploaded automatically. Raw capture is off by default; if you enable it for diagnostics, the file stays on your device unless you explicitly export it.

SETUP MATTERS Place the watch beside the phone — never on it — on a hard surface near the bottom microphone. Hairspring includes a visual setup guide and live signal-path coaching so you can see what needs attention.

Requires a mechanical, not quartz, watch. Rate is what a phone microphone measures best; amplitude and beat error are reported with their limits stated.