Multimeters get their name by metering multiple things:

• Voltage (DC and AC)
• Current (DC and AC)
• Resistance
• Continuity

are almost always present, also found on some multimeters are:

• Frequency
• Capacitance
• Transistor testor (find if it's a PNP Transistor or an NPN transistor and which legs are which)

There are different types of multimeter available, different features are available depending on your needs.

Analogue Multimeter

Also called AMM A type of Multimeter using an analogue needle for measurement. These are often limited to basic measurement and are sometimes unsuitable due to a high level of accuracy being required. Polarity is important with DC measurements on most units.

Digital Multimeter

Also called DMM These have a digital display which can give a very accurate reading. There are often range switches to give a clearer more useful reading in appropriate units (milli, micro, mega etc). A DMM will read a negative result.

===True RMS=== (a subset of DMM)

These devices will give you a reading which is often more useful for calculations. An actual measured RMS reading instead of an assumed RMS reading (some meters measure the peak and provide a reading assuming the wave is a sine-wave, this will be misleading if the waveform in question is not a pure sinewave). Just as we prefer to know RMS ratings of speaker cabinets it is also handy to know RMS values in terms of voltage or current.

• Multimeters can cost from a few pounds to several hundred pounds depending on type, make and features.
• Multimeters are handy tools to have in your tool box. They can be used for many things in the industry from checking a battery, finding ground problems to finding out why lamps are failing at a high rate.