Before you touch the dial
A multimeter measures several things, and each needs a different connection. Choosing wrong can destroy the meter, or the circuit, or both.
| Measuring | Dial setting | How it connects | Circuit state |
|---|---|---|---|
| Potential difference | V⎓ | Parallel, across the component | Powered on |
| Current | A⎓ | In series, in the path | Powered on |
| Resistance | Ω | Across the component alone | Powered off |
| Continuity | 🔊 | Across the two points | Powered off |
Steps
- Set the dial before connecting anything.
- Black lead in COM, always.
- Red lead in V/Ω for voltage and resistance; in A or mA for current — and yes, moving that lead is the step everyone forgets.
- Start on the highest range if your meter is not auto-ranging.
The expensive mistake
Leaving the leads in the current sockets and then measuring voltage puts a near-short across your source. Best case, the meter’s fuse blows. Make it a habit: check the sockets, then the dial, then connect.
Resistance must be measured out of circuit
Other components in parallel give the meter alternative paths, and you will read a value lower than the real one. Disconnect at least one end first.