Watch Quality Testing: How Swiss Timepieces Are Evaluated

The primary purpose of a timepiece is to measure and display time. It follows that the most important indicator of watch quality is timekeeping precision — though there are many other professional metrics beyond accuracy alone. To determine whether a timepiece meets quality requirements, a range of tests must be conducted. The specific requirements and testing methods vary depending on the type of timepiece.

Standard testing falls into four categories: functional testing, performance testing, environmental testing, and power reserve testing.

I. Functional Testing

Functional testing evaluates the operating condition, movement behavior, and operational performance of all components. Test content includes:

(1) After the timepiece begins running and a set period has elapsed — 24 hours for mechanical watches, 1 hour for quartz watches — the operating condition is inspected: whether the watch has stopped, whether there are significant indication errors, and so on.

(2) All operational components (such as the crown and pushers) are operated according to prescribed requirements and checked for anomalies — for example, whether the crown is too loose or too tight.

(3) The indication components are checked for anomalies: whether the seconds hand moves smoothly, and whether digital displays and switching functions operate correctly.

(4) If the timepiece is equipped with additional functions — such as a calendar, alarm, chime, or chronograph — these auxiliary functions are operated according to prescribed requirements and checked for anomalies.

II. Performance Testing

Performance testing measures timekeeping precision under various conditions. It encompasses the following areas:

1. Daily Rate (Timekeeping Accuracy at Room Temperature)

Test positions: For wristwatches, the standard positions are dial-up horizontal (CH), crown-left vertical (6H), and crown-down vertical (9H) — as these reflect the most common positions during wear. For clocks, the normal position of use is applied.

Precision testing: The instantaneous daily rate or actual daily rate of the timepiece is measured in each of the above positions. The instantaneous daily rate is measured using a timing machine; the actual daily rate is obtained by comparing the watch against a reference standard clock, then repeating the comparison 24 hours later — the difference between the two readings is the actual daily rate.

2. Daily Rate Variation (Timekeeping Stability)

By recording the instantaneous or actual daily rate values on two consecutive days under identical conditions, the daily rate variation and drift values can be calculated. This test is generally conducted over an extended period of continuous operation.

3. Temperature Coefficient (Effect of Temperature on Precision)

The timepiece is run for a set period at 8°C, 23°C, and 38°C respectively. The instantaneous daily rate at each temperature is measured, and from this data the temperature coefficient, temperature error, and secondary temperature error are calculated.

4. Atmospheric Pressure Coefficient (Effect of Pressure on Precision)

The timepiece is run for a set period at standard atmospheric pressure of 101.3 kPa, then tested at 2 to 10 different pressure levels. The instantaneous or actual daily rate at each pressure is measured, and the atmospheric pressure coefficient is calculated from this data.

5. Positional Error (Effect of Position on Precision)

Primarily used for mechanical wristwatches. Test positions typically include: dial-up (CH), dial-down (FH), crown-right (3H), crown-left (6H), crown-down (9H), and crown-up (12H). The instantaneous daily rate is measured in each position, and from this data the positional error, maximum positional deviation, and mean positional error are calculated.

6. Voltage Coefficient (Effect of Power Supply Voltage on Precision)

Primarily used for quartz watches. The instantaneous daily rate is measured at the nominal voltage and again when the voltage drops to a specified lower value. The voltage coefficient error is calculated from these readings.

7. Isochronism Error (Effect of Mainspring Torque Variation on Precision)

The instantaneous daily rate is measured separately when the mainspring is fully wound and after 24 hours of running. From this, the effect of mainspring torque variation on timekeeping precision is calculated. As mainspring torque decreases, the amplitude of the balance wheel diminishes — and changes in amplitude cause changes in the rate of timekeeping. This rate error caused by amplitude variation is known as isochronism error, or simply isochronism.

III. Environmental Testing

Environmental testing includes temperature testing (high/low temperature tests or thermal shock tests), humidity testing, vibration testing, water resistance testing, magnetic resistance testing, and shock resistance testing.

IV. Power Reserve Testing

From the moment the mainspring is fully wound, the total elapsed time until the timepiece ceases to operate is known as the power reserve (also called running time or autonomy).

At Aorawa Time, we believe that understanding how watches are tested and certified helps you make better choices — whether you're selecting a fine mechanical timepiece or choosing the perfect Apple Watch band to complement it. Quality is measurable. Explore our premium watch accessories at aorawatime.com.