[en] Operation of a crystal measurer of maximum temperature (CMMT) is described. CMMT is related to devices of the contactless group and represents a capsule of 1 mm diameter and 4-5 mm long filled with diamond crystals or SiC irradiated preliminary up to the fluence of 1x10²⁰ n/cm² and gradulated. Parameters of the crystal lattice change after temperature annealing of defects (the Frenkel pairs, interstitials and vacancies); it reflects in X-ray diagrams of CMMT. Annealing temperature is determined according to the diameter of X-ray line ring and annealing time. Examples illustrating temperature measurements by CMMT in discs and turbine blades, pistons, valves of engines in a cutting tool, bearings and other units and elements of machines and mechanisms are presented. A method for temperature measuring in a nuclear reactor by a diamond is described, radiation and annealing effect on the characteristics of working medium of temperature-sensitive element is considered. A review of methods for temperature measuring is given