A multimeter is the most useful tool when dealing with electricity. A cheap $15 multimeter will go a long way and is likely all that you’ll need. In general, anything fancier/more expensive just increase accuracy and adds very specific functionality that you are unlikely to ever use.
How to Measure Voltage
Voltage is probably the most common measurement you’ll make. Whether you’re checking batteries or wall sockets, voltage is what you’re looking for. Your multimeter will have a voltage setting and either separate settings or a toggle button for AC and DC voltage. You’ll need to know if you’re dealing with AC or DC.
Check Batteries with Multimeter
- Set your multimeter to DC voltage
- Connect the red test lead to the multimeter voltage input
- Connect the black test lead to the multimeter common input
- Connect the other end of black test lead to battery negative (-) terminal
- Connect the other end of red test lead to battery positive (+) terminal
| Battery Type | Normal Voltage |
|---|---|
| AA, AAA, C, D Alkaline Battery | 1.5VDC |
| AA, AAA, C, D Rechargeable NiMH Battery | 1.2VDC |
| Car Battery When Off | 12VDC |
| Car Battery When On | 13.5VDC ~ 14.5VDC |
*Note: Consider replacement or charging if battery is below the above values.
Check Wall Sockets with Multimeter
- Set your multimeter to AC voltage
- Connect the red test lead to the multimeter voltage input
- Connect the black test lead to the multimeter common input
- Connect the other end of red test lead to one side of wall socket
- Connect the other end of black test lead to other side of wall socket
*Note: Don’t worry about the bottom middle prong (ground in North America). Polarity does not matter for AC voltage measurement. You should be seeing ~120VAC on a normal wall socket (not special washer/dryer sockets) in North America.
How to Measure Resistance
Resistance measurement is very useful for testing wires / cables and is the second most common measurement I make. If a wire is good, resistance will be very low, if it’s bad or disconnected, resistance will be very high. A decent multimeter should have a “continuity” function. This feature will cause the multimeter to audibly beep if resistance is very low. If your multimeter doesn’t have a continuity function, then just read the numbers on the resistance setting. I would consider anything under 100 ohms low for wires.
Check Wiring with Multimeter
- Set your multimeter to resistance
- Connect the red test lead to the multimeter voltage / resistance input
I have not encountered any multimeter where resistance input isn’t shared with voltae - Connect the black test lead to the multimeter common input
- Connect the other end of red test lead to one end of wire
- Connect the other end of black test lead to other end of wire
How to Measure Current
I can think of no practical reason why someone looking to learn the basics of multimeters and electricity should measure electrical current.
- Set your multimeter to AC / DC current depending on application
- Connect the red test lead to the multimeter current input
- Connect the black test lead to the multimeter common input
- You will need to connect the multimeter inline with whatever circuit you’re trying to measure current for.
e.g., you may need to disconnect something, put red lead on one end and the black lead on the other.
If you’re learning the basics of multimeters and electricity, I do not recommend current measurement and I see no need for it. Personally, I use current measurement to determine load when tinkering with electronics. It helps me figure out if my power supply is suitable and how long I can run something.