By Chris FollinSHOP SKILLS
How to use a multimeter
A multimeter is one of the most useful tools in the shop, but it punishes wrong setup. Learn on low-voltage DC, verify the leads and dial before touching the circuit, and respect CAT ratings around building power.
Best For
Checking batteries, continuity, fuses, switches, low-voltage wiring, and basic DC circuits.
Core Idea
Meter setup comes before probing: correct lead jack, correct function, correct range, correct rating.
Use
CAT-rated meter and leads, intact probes, good light, and one hand when appropriate.
Hard No
Never measure voltage with the lead in the amps jack. Never measure current across a battery or outlet.
Learn on low voltage first
Start with batteries, 12-volt systems, continuity, and unplugged components. Mains voltage and panels require the right meter, the right PPE, and real electrical knowledge. The meter should be rated for the environment, not just the number on the screen.
Before every measurement: look at the lead jacks, look at the dial, then look again.
VoltageMeter goes in parallel. Red to V, black to COM.
ContinuityPower off. Use beep mode to check whether a path is connected.
CurrentMeter goes in series and often uses a different jack. This is where beginners blow fuses.
Basic checks
- Inspect the meter. Cracked case, damaged leads, or loose probes mean stop.
- Set the function. DC volts for batteries, resistance/continuity for unplugged parts.
- Use the right jack. Most normal checks use COM and V/ohm.
- Start high if range is manual. Step down after you know the ballpark.
- Probe deliberately. Touch metal tips only to the points you mean to test.
- Return leads to normal. Move the red lead out of amps immediately after current testing.
Good first jobs
- Check a AA, 9V, or 12V battery.
- Find a blown fuse with continuity.
- Verify a switch opens and closes.
Stop and learn more
- Breaker panels and service equipment.
- Unknown high-voltage circuits.
- Measuring amps without understanding series wiring.
The mistake to avoid
The classic bad move is leaving the red lead in the amps jack and then trying to measure voltage. That can short the circuit through the meter. Build the habit of returning the lead to the voltage jack as soon as you finish current work.