A digital multimeter comprising a measured object input terminal, conversion circuit for a fast analog/digital converter, microprocessor, auxiliary program-controlled voltage or current source, potential divider network, electronic switches, and display. Compared with conventional multimeters, the adoption of fast analog/digital conversion technology as well as a method that applies an auxiliary power supply at the time of a passive analog measurement allows for measuring different responses between input terminals after an auxiliary power supply is applied, thus being able to automatically determine the characteristics and size of the measured object.