Using a multimeter

A multimeter is the single most useful tool on your bench. It rolls three instruments into one: a voltmeter, an ammeter, and an ohmmeter. You spin the dial to choose what you want to measure — voltage, current, or resistance — and read the number off the display.

The golden rule is about how you connect the probes for each mode:

• Voltage — probe across a component, in parallel (the circuit stays powered).
• Current — break the loop and put the meter in line, in series (current must flow through it).
• Resistance — measure the component out of the circuit, with the power off.

Voltage is the everyday measurement — it’s quick, non-invasive, and tells you most of what you need: "is power reaching this point? how much is the LED dropping? is the battery flat?". You can probe live without disturbing anything, which is why it’s the first thing most people reach for.