Vernier Calipers

Vernier calipers are precision measuring instruments used to accurately determine the dimensions of objects with high precision. They consist of two main parts: the fixed main scale and the sliding vernier scale. The main scale is marked in millimeters (or inches), while the vernier scale slides along the main scale and provides readings in fractions of these units. The key to their accuracy lies in the vernier scale, which has finer graduations than the main scale. When measuring an object, the user aligns the jaws around the object and reads the measurement where the lines on the vernier scale coincide with the lines on the main scale. The vernier scale works by having a series of equally spaced marks that are slightly offset from the marks on the main scale. The smallest division on the vernier scale that aligns perfectly with a division on the main scale indicates the measurement. This design allows vernier calipers to measure lengths to within a fraction of a millimeter or thousandth of an inch, depending on the instrument's precision.

• Calipers on Wikipedia
• Vernier Scale on Wikipedia