What is the key function of Vernier callipers?

Vernier callipers are a precise measuring instrument designed to take detailed measurements of an object's dimensions, such as length, depth, and inner and outer diameters. The main feature that allows for such precision is the combination of a main scale and a sliding Vernier scale, which provides a method to obtain measurements to fractions of a millimeter or inch. This precision is essential in engineering and manufacturing processes where exact measurements are crucial for quality and functionality.

In contrast, measuring weight, temperature, or voltage involves different tools or devices that are specifically designed for those purposes, such as scales for weight, thermometers for temperature, and voltmeters for voltage. These functions do not relate to the capabilities of Vernier callipers, further underscoring the role of this instrument in providing exact measurements rather than measuring other physical properties.