A multi-meter or a multi-tester, also known as a VOM (Volt-Ohm meter), is an electronic measuring instrument that combines several measurement functions in one unit. A typical multi-meter would include basic features such as the ability to measure voltage, current, and resistance. Analog multi-meters use a micro-ammeter whose pointer moves over a scale calibrated for all the different measurements that can be made. Digital multi-meters (DMM, DVOM) display the measured value in numerals, and may also display a bar of a length proportional to the quantity being measured. Digital multi-meters are now far more common than analogue ones, but analogue multi-meters are still preferable in some cases, for example when monitoring a rapidly-varying value.
A multi-meter can be a hand-held device useful for basic fault finding and field service work, or a bench instrument which can measure to a very high degree of accuracy. They can be used to troubleshoot electrical problems in a wide array of industrial and household devices such as electronic equipment, motor controls, domestic appliances, power supplies, and wiring systems.