Timegrapher apps

Hairspring - Watch Timegrapher

A serious iPhone timegrapher for mechanical watches. Hairspring measures rate, beat error, and an honest amplitude range from the phone microphone. Measure the same watch twice and it reports whether the readings agree after accounting for each run’s statistical uncertainty. Weak or irregular signals produce a reasoned refusal instead of a plausible-looking number. One $9.99 purchase; no subscription, account, ads, analytics, or automatic uploads.