The book describes properties and methods of measuring electrical quantities by digital measuring instruments. In addition to the basic methods of measurement of these quantities, less traditional methods and instruments are presented with the aim of achieving high accuracy and reproducibility of the measurement results. The properties of digital multimeters, calibrators, selective amplifiers, universal counters, impedance meters, signal generators, digital oscilloscopes, spectral and vector analyzers, power meters, inspection and diagnostic instruments and measuring systems are analyzed in detail. The book is intended for students of technical and non-technical universities and all other workers who use electronic digital measuring instruments of electrical quantities in their activities.