device for measuring force or moment; it consists of a force component (elastic element) and a reading device. In the force component, the force to be measured is converted to a deformation, which is transmitted to the reading device directly or through a gear mechanism. Dynamometers can measure forces ranging from several newtons (fractions of a kilogram-force) to 1 meganewton (100 tons-force). According to their principle of operation, a distinction is made among mechanical (spring or lever), hydraulic, or electrical dynamometers. Two principles of operation are sometimes used in the same dynamometer. Dynamometers are distinguished according to purpose as reference and operational (general-purpose and special) types.
Reference dynamometers are intended for testing and calibrating operational dynamometers and for monitoring the stresses of machines during the testing of the mechanical properties of various materials and products. Reference dynamometers are categorized as first-class, second-class, or third-class according to their degree of accuracy. First-class dynamometers are designed for checking second-class reference dynamometers, which in turn are used for testing and calibrating third-class dynamometers and for checking general-purpose dynamometers. Third-class dynamometers are used for checking and calibrating testing machines and devices; they are built with elastic elements in the form of locking clamps of the bending-strain type and locking clamps or bars that undergo compressive or tensile strain.