The Design features of Vernier Caliper Gages

A caliper gages are made in different length , starting with a useful range of about 5 inches, and are available in lengths of up to 48 inches, or, exceptionally, even longer . The depth of the jaw also varies, although not in a linear relationship with the measuring range.
The form of the jaws may be designed for measuring external surfaces only, or can be provide with features permitting internal measurements as well. Measurements on internal surfaces are made either by inside gaging jaw tips or directly, by knife edge auxiliary jaws that can pass each other along a common mating plane. When measuring inside distances with the jaw tips , the combined thickness of the two tips must be added to the indicated dimension , unless the beam has separate graduations for outside and inside measurements.