A multimeter is an instrument that measures the voltage, current, and resistance of an electrical device. Also known as a VOM (Volt-Ohm-Milliammeter), they are very useful in providing field measurements or detecting faults with accuracy.
The first multimeter was invented by Donald Macadie, a British post office engineer who was unhappy with the need to carry separate instruments needed for the maintenance of telecommunication circuits. His invention was the instrument that could measure amperes, volts and ohms, and was named the avometer.
The device is commonly used by electricians and other experts to troubleshoot problems on appliances, motors, circuits, power supplies and wiring systems. They could use the device on batteries, switches, power sources etc for measuring or diagnosing.
Multimeters can be analogue or digital. Analogue multimeters are cheaper, but their readings are not as accurate as the digital meters. Recent digital multimeters are advanced enough to measure extremely tiny differences or fluctuations.