Digital multimeters, such as digital oscilloscopes or A/D acquisition boards, convert the analog signals into digital data and then display the measured values. Since the signal is recorded with increasingly long memories, the multimeter can then fill more and more functions : recorder, waveform display, FFT… These functions depend on the onboard processing capabilities and the type of display. The peak, average or effective values ​​of an AC voltage are displayed by most multimeters today, which calculate the true RMS value of the AC voltage which corresponds to the equivalent DC voltage = the same thermal power on an identical resistance ; Ie root mean square (square wave function, integrated over a period T). In addition to the voltages, the multimeters also measure currents, resistances, impedances, frequencies and often temperatures via an external probe.