Hairspring measures how well your mechanical watch keeps time, using your iPhone's microphone — and tells you when it can't.
That second half is the whole point. Every reading comes with its own uncertainty. When the signal won't support a number, Hairspring says so and tells you what to change, instead of printing something plausible.
MEASURE TWICE, SEE IF THEY AGREE
The check no other timegrapher app offers. Measure the same watch again and Hairspring compares the two readings and states whether they agree — the difference between a number and a number you can trust.
WHAT IT REPORTS
• Rate in seconds per day, with its measurement uncertainty
• Beat error, measured from the escapement's own high-frequency signature
• Amplitude, reported as a band because that is what the method supports
• Timing graph, position runs, and history
WHY THE NUMBERS ARE HONEST
Hairspring refuses a rate it cannot defend: too much scatter, an implausible result, or timing too disturbed to number the beats at all. Each refusal names its cause and the fix. Its analysis band was chosen by a pre-registered experiment — criteria written down before the data was collected — and the first attempt failed and was recorded as a failure.
FREE, AND NOT WATCHING YOU
Every measurement, every position, every report. No subscription, no account, no email, no ads, no analytics. Audio is analysed on your device and never leaves it.
SETUP MATTERS
Watch beside the phone — never on it — on a hard surface, near the bottom microphone. Hairspring includes a setup guide and tells you, while you measure, which part of the signal path is failing.
Requires a mechanical (not quartz) watch. Rate is the measurement this method does best; amplitude and beat error are reported with their limits stated.
