A multimeter is a device used to test electronics. It combines the features of a number of electronics testing devices into one unit for convenience.
Multimeters vary greatly in quality and complexity, but even the most basic generally measure voltage, resistance and current. Voltage is measured in volts, current in amperes and resistance in ohms. Multimeters come with a positive and negative test lead, usually with one colored red and one colored black to distinguish them. The handles of the leads are insulated to prevent the user from getting an electric shock. For example, it is usually safe to place the leads in a power outlet to see if it is functional. They also usually have at least one fuse to protect both the user and the meter.
Some multimeters have additional functions, such as the ability to measure capacitance, conductance, decibels, frequency and inductance. Digital multimeters usually have a continuity tester to check if a circuit is functioning. Digital units may also be able to test diodes, transistors and various types of small batteries.
Multimeters are used by electricians, electronics repair technicians and electrical engineers. Information technology technicians may also have a need for a multimeter from time to time.