Calipers

Caliper

— measuring tools for determining linear dimensions with an accuracy of at least a tenth of a millimeter (although more precise instruments are also available). They are mainly intended for measuring external dimensions, although many models also provide the capability for internal measurements at a shallow depth and/or the ability to measure the depth of holes and recesses. The design of a caliper is based on a beam (bar) with a measuring scale, along which a special frame can move freely. One measuring jaw is fixed on the bar and does not move, while the other is mounted on the movable frame. For internal measurements, an additional pair of jaws is provided, usually at the top of the structure. For depth measurements, a depth gauge ruler is used, which is connected to the movable jaw and extends from the end of the bar on the opposite side of the fixed jaw. This ruler acts as a kind of probe that descends to the bottom of the hole or recess when measuring depth. Calipers can use different operating principles—mechanical or digital. It should be noted that digital devices are significantly more accurate. They often provide measurement accuracy at the level of hundredths of a millimeter (rather than tenths, like "mechanical" ones). Such high-precision instruments are sometimes called micrometer calipers and are classified into both categories.