VU Meters

Analog VU (Volume Unit) Meters measure sound as electrical signals in audio equipment. For all you engineers, VU meters are 200 μA DC d’Arsonval movement ammeters fed from a full wave copper-oxide rectifier. They measure average sound levels and are designed to represent the way human ears perceive volume, so that a reading of 0 VU (the “optimum audio level” or ideal constant voltage) represents +4 dBm, or 1.228 volts RMS across a 600-ohm load. The rise time of a VU meter (the time it takes to register the level of a sound) and the fall time (the time it takes to return to a lower reading) are both 300 milliseconds.