Guessing what's wrong costs time. Measuring takes seconds. A multimeter is the tool that makes the difference between an hour of searching and knowing straight away.
You don't need an expensive device. The D03048 from Duratool is a solid entry-level choice for anyone who wants to measure voltage, resistance and continuity. For more demanding use, look at the Chauvin Arnoux range.
Measuring voltage
Measure voltage in parallel: both probes at the two points between which you want to know the voltage, circuit stays on. Set the meter to DC for batteries, power supplies and digital circuits. AC for mains voltage — but if you're working on mains, this article alone isn't enough.
The black probe goes to ground or the reference point, the red to the measurement point. Reversed gives a negative value — no damage, just swap them.
Always measure at several points: power input, regulator output, right next to the IC. Voltage drops across wiring, connectors and regulators tell you exactly where the problem is.
Measuring resistance
Measure resistance with the power off. In a live circuit, parallel paths affect the reading — you're not measuring the component in isolation, but the parallel combination of everything around it. Lift the component out of the circuit or measure it separately.
Want to quickly check whether a resistor is correct? Read the colour code, then measure — two seconds. A 10 kΩ resistor with 1% tolerance should read between 9.9 kΩ and 10.1 kΩ.
Continuity: the beep function
The continuity mode is the most used setting on the workbench. Probe on point A, probe on point B, beep means connection. Use it for:
- Testing cables: connected or broken?
- Checking solder joints after soldering.
- Locating bridges between adjacent pads on an SMD board.
- Finding short circuits on a power line.
Note: a beep means there's a connection, not that the connection is good. A bad solder joint with high contact resistance can beep but still cause problems under current.
Diode test
The diode test measures the forward voltage drop. A silicon diode like the 1N4007G typically reads around 0.6 to 0.7 V. An LED gives a higher value — red typically 1.8 V, blue or white around 3 V — and briefly lights up. A Schottky diode reads 0.2 to 0.4 V.
In reverse direction: no conduction, meter shows OL (open loop). If a diode conducts in both directions, it's failed.
Measuring current: the most dangerous measurement
Measure current in series. That means: break the circuit, put the meter in between. The meter then acts as a zero-resistance path for the current — it's a short circuit path.
This is where things regularly go wrong. If the meter is still set to current measurement (A or mA) and you measure voltage, you create a short circuit. The fuse in the meter blows — or worse. Always switch the meter back to voltage mode after a current measurement. And when in doubt, start on the highest range.