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Tips & Guides

How to use a digital multimeter

These exercises use loose AA cells or disconnected, unpowered passive parts only. Do not work on household wiring, mains supplies or high-voltage equipment. Never connect current-mode probes across a battery. Stop if a battery is damaged, leaking or hot.

+−DC VCOMV/Ω
DC voltage: red to +, black to −. Black lead in COM; red in V/Ω. Never use A/mA sockets across a battery.
  1. Read your meter’s manual and inspect the insulated leads. Put black in COM and red in V/Ω. Leave A/mA sockets unused for these exercises.
  2. Voltage measures a difference between two points. For a loose AA cell choose DC V (straight-line symbol), or a manual range above 1.5 V, such as 2 V or 20 V. Red touches +; black touches −. A negative number means the probes are reversed.
  3. AC V uses a wave symbol; it is not the setting for a battery. Resistance (Ω) and continuity are only for disconnected, unpowered passive parts. OL can mean an open circuit or an exceeded range: consult the manual.
  4. Current uses a different socket and a series connection, opening the circuit so current passes through the meter. It is not part of this beginner exercise. Never use current mode across a battery.

Related explanations

Volts (V)Amperes (A)Resistance (Ω)

Official sources