Chronometer App – Precision Rate Tracking

for Mechanical Watches

This iOS app allows you to measure and track the daily rate of mechanical chronometer watches with professional-grade accuracy. The app synchronizes with an official Swiss atomic-time NTP server (METAS) to ensure precise time comparison. Recorded data can be exported to iCloud as a CSV file, ready for further analysis in Excel® or other tools.

How it works

Before starting, set your watch to atomic time. Do not adjust the watch during the measurement period. The app requires an internet connection to receive the NTP signal. 1. Wait for the NTP indicator to turn green – this confirms atomic-time synchronization. 2. Capture the watch dial by pausing the live view (no image is stored to avoid delays). 3. The exact atomic-time stamp is recorded. Adjust the dis- played time to match the watch dial: this gives the exact deviation. 4. Optionally enter altitude above sea level, as altitude can influence rate behavior. 5. Tap Save Rate to store the measurement Repeat daily. After recording 15 days of data, you will get a reliable chronometric profile — the same observation period used in official chronometer certification tests.

Understanding results

The app compares your watch’s daily deviation against atomic time. • A mechanical wristwatch with < 10 seconds/day deviation is considered very precise. You can use the data to fine-tune the rate and track improvements over time..

Settings & Export Options

In the settings menu, you can specify: • Watch name • Escapement frequency (Hz) • Moment of inertia of the balance (mg·cm²) With Export CSV, the app saves: • Date • Absolute rate deviation • Daily rate deviation • Altitude (optional) •

Compatibility

This app is fully optimized for iOS 26.