The most important debugging tool in any E.E.'s toolbox is a trusty multimeter. A multimeter can measure continuity, resistance, voltage and sometimes even current, capacitance, temperature, etc. It's a swiss army knife for geeks!

You should go through all of these sections in order, as they build on each other.

1. Continuity measurements
   How to tell if two points are electrically connected
2. Resistance measurements
   How to measure resistance - resistors, potentiometers and sensors
3. Voltage measurements
   How to measure voltage - battery testing, wall-wart adaptor testing, and the terror of mixed AC/DC measurements.

Everyone always asks What multimeter should I get?

Well, since they're rather commodified (there are dozens of manufacturers) it is hard to make everyone use the same model, even though it would make things easier.

These are the necessities:

• Continuity testing with piezo buzzer
• Resistance test down to 10 ohm (or lower) and up to 1 Megaohm (or higher)
• DC voltage test down to 100mV (or lower) and up to 50V
• AC voltage test down to 1V and up to 400V (or 200V in the US/Canada/Japan)
• Diode testing

Here are nice things to have in your meter

• Auto-off - to keep from draining the batteries
• AC and DC current test, from 10mA to maybe 200mA and then also a 10A one as well
• Stand - a thing that flips out and keeps it upright on your table
• Auto-ranging - note: some people don't like auto-ranging because its slower and not as precise
• Hold - keep the maximum value on the screen so you can probe without looking at the meter.
• Common battery - such as 9V or AA's, pocket meters use hard-to-replace coin cells

These are things that I rarely (if ever) use, in decending order

• Frequency counter - before I had a scope this was surprisingly useful!
• Capacitance testing - usually to check random SMT caps
• Inductance testing - how often do you really use an inductor?
• Duty cycle - never used this
• Transistor beta meter - people don't really work with transistors anymore
• Temperature probe - I use the "Pease temperature test": a finger

I have a selection of suggested meters on this page, I strongly suggest the "better" (At $15 its a great value) or "best" ($50, autoranging, has a temp probe, all sorts of other junk) ones as the "good" one is really kinda bad. If you already have a multimeter then just use that one. I'll only be covering digital multimeters here so if you have an analog one, it may be a little different and you'll have to experiment to figure out what's up

A good multimeter will cost about $25. I suggest getting a ranging one , with current testing, and a wide range as well as easy-to-replace battery. You don't need to spend $200 on a Fluke 73! A $50 meter will be excellent. Auto-ranging meters may keep you from tripping up on ranges at first, but they're slower and often flakier.

I have had a Wavetek Meterman 27XT for half a dozen years and its been really good to me, but it was also about $80.

Here are many other links for learning how to use a multimeter

• TangentSoft's half-hour video tutorial
• Make Magazine's Bre & Joey Grand on how to use a multimeter