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Using a Multimeter


First off, a little announcement - SparkFun offices will be closing today at 3 PM for a meeting server upgrade event, ok, we admit it, a party. It's the annual SparkFun end-of-summer party and we are going to be cutting out a little bit early - so be advised no one will be answering the phones. Of course, you can still place orders!

Ok, on to serious business - multimeters! The multimeter is a great tool for electronic enthusiasts. When it comes to testing parts and saving time, they are worth their weight in gold. But how, exactly, does one use a multimeter?

If no one ever explained to you how to use one of these great tools, it can be a little confusing to know exactly what you're measuring, how to interpret the numbers on the screen, and which setting to use when! With that in mind, Nate put together this tutorial explaining how to use a multimeter! We hope that it helps - happy testing!


Comments 12 comments

  • My chief point is that this stuff should be up in the “measuring current” section, rather than down in “changing the fuse”. But that’s just me.

  • Not a bad tutorial. BUT.
    If it were up to me, I’d include a BIG caveat about what to do AFTER you measure current. As a retailer of electronic test equipment as well as having years of tech experience, I’ve noticed that one of the big (classic) mistakes people make is configuring their meter for measuring current, doing that, but then forgetting to switch the leads and/or rotary knob back to volts when they’re done, and when (minutes, hours, or days later) they pick up the meter and try to measure volts… WHAM. Bye-bye fuse.
    Another way to deal with this is to take the approach of ALWAYS checking the lead configuration and rotary knob setting BEFORE measuring voltage… rather than blithely going ahead and “measuring volts with a dead short”.
    Being prudent, I try to remember to do both. Just in case.

    • Excellent excellent. I have similarly left a meter on current and as I went to measure voltage, blew the fuse. I’ll add a bit to the tutorial. Thanks!

  • It depends on what you want to do with the numbers… I would take the measurements inline with a resistor. Knowing the voltage and the current gives you power.. this number is probably better depending on what you are doing.
    V=I*R controls the world.

    • “V=IR"
      That may be but:
      P=I
      E
      Powers the world (and is a more important measure of solar panel output).

  • It was awesome to meet Nate and some of the other Sparkfunions at Maker Faire NYC this weekend - good to finally put some faces to the awesomeness. Enjoy the party!

  • How does one measure max current from a solar panel? Is it ok to just short it with the probes?

    • Solar cells have a voltage-current-curve. You’d have to measure them both at the same time (implying the need of 2 multimeters). If you measure with just one MM in current mode, the solarcell leads gives you a current value, but the voltage across it would be nil. (as it is effectively shorted) If you put it in voltage mode then you get a voltage value, but no current runs through it (or really really small amout), since voltage measurements have very high impedance (resistance). In both cases the output power is nil, since both situations involve a multiplication of nearly zero. You can only get the extremes of the curve, where they end up on the two axes.
      The actual voltage and current that a solar cell or panel delivers depends on the application you are trying to power, and on the amount of light ofcourse. The easiest way is to hook it up and stick 2 multimeters in between and see what is settles to. Here is an example of a curve showing different lighting conditions, and the wavy line is the voltage/current combination where the most power comes out of the panel/cell. An application that demands too much current makes the voltage collapse.
      http://en.wikipedia.org/wiki/File:Solar-Cell-IV-curve-with-MPP.png

    • Yep, that’s fine.

  • don’t do DRUGS :D

  • some meters cost their weight in gold too :)


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