What technique is used to indicate measurement on a tachymeter scale?

The technique used to indicate measurement on a tachymeter scale involves reading the inner scale for slower times. A tachymeter scale is typically found on the bezel or dial of a watch and is used to measure speed based on the time taken to cover a known distance or to convert time into speed.

When timing an event, the user can start the chronograph as soon as they pass a certain marker (like the start of a mile), and then stop it once they reach the next marker (like the finish of the mile). The inner tachymeter scale measures how many units of speed (e.g., kilometers per hour) correspond to the elapsed time in seconds. The inner scale is specifically designed for situations where the time is greater than a specific threshold, allowing for measurements related to distances or speeds that occur over longer durations.

In contrast, the outer scale is often used for shorter durations or higher speeds, making it less suitable for measuring slower times accurately. The other options involve methods or readings that do not directly relate to the functionality of the tachymeter scale or rely entirely on digital means, which are not necessary for traditional tachymetric calculations.