Here are three quick and simple multimeter tricks to save you time and blown components. While basic, they can be a lifesaver if you haven’t thought of them.
1. Check circuit input impedance before powering on
If you’ve ever soldered a circuit together and gone for the moment of truth by turning the power supply on, only to see a puff of smoke from your ICs, you might want to give this a go. When your circuit is ready for testing simply put your multimeter into impedance measuring mode and measure the input impedance between the positive and negative voltage inputs of the circuit. Most DC circuits with ICs will have more than 5-10k ohms of impedance here. If you see below that (especially if it’s below 100) you likely have a short! Take a look over your circuit and try again before plugging in.
2. Connect the multimeter directly to ground when testing
I’ve seen way too many people accidentally short a circuit because they were trying to hold both meter probes in place, while looking at the readout on the meter. Not only is it hard to hold them precisely, but there’s a huge risk of causing an accidental short that will have you replacing components. Instead, take a banana cable and connect it from the multimeter negative input to the ground on your power supply, then hook your device up to supply ground. Alternatively, connect a banana cable with an alligator clip from the meter to ground on the circuit. Now you only have to probe with the positive probe for most things!
3. Use the audible alarm in your meter
Most multimeters come with an audible alarm (generally a beeper) that you can use along with tips 1 and 2 to quickly and easily check for shorts without having to look at the display. Simply enable the alarm (on my multimeter I put it into the impedance mode and press a dedicated button for it) and start measuring. If there’s zero impedance you’ll hear the problem without having to look up from your work.
And that’s it! Let me know @michaelblouin if these tips were useful to you. If you know what you’re doing they’re pretty basic, but if you don’t know them they’re an absolute life saver!