The textbook was developed in accordance with the requirements of state educational standards of higher professional education in the direction of training of a certified specialist 653700 - "Equipment" (specialty 190100 - "Equipment") and the direction of training of bachelors 551500 - "Equipment" . The book deals with the main issues of the theory of accuracy of measuring instruments: Characteristics of error of measuring instruments (SI) and methods of their rationing, natural limits of accuracy of measuring instruments, methods of analysis and evaluation of accuracy of functioning of SI, methods of synthesis of SI, structural and algorithmic methods of increase of accuracy and immunity of SI . The textbook is intended for fourth-year students studying the discipline "Accuracy of measuring devices". It can be used by students specializing in the field of instrumentation, metrology and measuring equipment, as well as university teachers and graduate students.