Using a Multimeter
Embedded → Bench Skills & Power
The first tool you reach for when a board is dead
Before a scope, before a logic analyzer, before you even open the schematic — a dead board gets a multimeter across it. Is 3.3V actually present at the regulator output? Is there continuity between this via and that pad? A multimeter answers both in seconds, and basic fluency with it is assumed the moment you walk into any hardware lab.
Four modes, four different ways to hold the probes
A multimeter is really four instruments in one enclosure, selected by a rotary dial:
| Mode | Detail |
|---|---|
| Voltage (DCV/ACV) | probes across two points, in parallel with the circuit — high input impedance barely disturbs it; the mode you use 90% of the time |
| Continuity | beep-on-low-resistance check for whether two points are the same net, or a trace/fuse is open — unpowered board only |
| Resistance (Ω) | like continuity but reads the value — also unpowered-board only, since a live circuit's real current swamps the meter's tiny test current |
| Current (DCA/mA/µA) | probes in series — you break the circuit open and route it through the meter; low input impedance by design, which makes this mode dangerous |
The mistake that blows the meter's fuse
The most common multimeter mistake: probes still plugged into the current jack, dial turned back to voltage, probes touched across a live rail. The current input is internally almost a dead short (a shunt resistor, by design), so this instantly shorts the rail through the meter — either the fuse sacrifices itself, or on a cheap fuseless meter, something worse happens.
Try it — pick a measurement, see the setup
Select a measurement mode and see which jack, probe placement, and board state it needs:
Practice
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