Instrument for making very accurate linear or angular measurements. Introduced in 1631 by Pierre Vernier (circa 1580–1637), it uses two graduated scales: a main scale similar to that on a ruler, and a specially graduated scale, the vernier, that slides parallel to the main scale and enables readings to be made to a fraction of a division on the main scale.
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Instrument for making precise linear measurements of dimensions such as diameters, thicknesses, and lengths of solid bodies. It consists of a C-shaped frame with a movable jaw operated by a screw. The accuracy of the measurements depends on the accuracy of the screw-nut combination.
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Instrument that consists of two adjustable legs or jaws for measuring the dimensions of material parts. Spring calipers have an adjusting screw and nut; firm-joint calipers use friction at the joint to hold the legs unmoving. Outside calipers measure thicknesses and outside diameters of objects; inside calipers measure hole diameters and distances between surfaces. Hermaphrodite calipers, which have one leg bent inward and one straight leg ending in a sharp point, are used for scribing lines at a specified distance from a flat or curved surface. Seealso micrometer.
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