A DC voltmeter measures the current passing between two points. The normal use of a voltmeter is to check the power in an electrical circuit. Manufacturers install some voltmeters permanently in equipment, but in testing equipment, the voltmeter is generally portable, allowing the user to test different circuits.
Analog voltmeters are generally galvanometers connected in series with a high-resistance resistor. They have a coiled spring that moves a needle in response to a magnetic field. The needle is next to a graduated scale, allowing the user to take a reading of the current. Such meters are generally less precise than those using improved technology and digital readouts.