Voltmeter (volt + Greek. μετρεω "I measure") is an electrical measuring device of direct reference for determining voltage or EMF in electrical circuits. It is connected in parallel to the load or the source of electrical energy.

An ideal voltmeter should have an infinitely large internal resistance. Therefore, the higher the internal resistance in a real voltmeter, the less influence the device has on the measured object and, consequently, the higher the accuracy and the more diverse the application areas.

A self-recording voltmeter is a voltmeter that records voltage measurements with a given frequency and number of channels in a file. The name voltmeter does not mean the ability to measure and record only voltages, with the help of simple additional boards, you can record current, temperature or measure time intervals, as well as almost any physical parameters by connecting sensors to it.