How to Use (and Choose) a Multimeter!





Introduction: How to Use (and Choose) a Multimeter!

About: Dabbled in dark matter, settled into engineering with a blend of inventing and teaching, always trying to solve problems + learn new things!

Checking your car battery life, debugging circuits, and finding that pesky short are all super useful functions that can be done with just one awesome tool: the multimeter!

First of all, what the heck is a multimeter?? Excellent setup question! It's a handheld device with bunch of different electrical meters -- hence, multi-meter!

Measuring voltage, current, resistance, and continuity (aka electrical connection) are the most common uses of a multimeter. Read on (and/or check out the videos) to learn what this means, how to do it yourself, and how to choose your very own multimeter!

Step 1: Choosing a Multimeter!

There are a few key differences between multimeters, the main one being analog versus digital:

Analog multimeters show real-time changes in voltage and current, but can be difficult to read and log data.

Digital Multimeters are easier to read, but may take some time to stabilize.

There are also auto-ranging multimeters, that automatically detect the measurement range, and manual ranging multimeters where you have to choose a range yourself (or start with the highest setting and work down).

Other than those two main differences, you'll want a multimeter that has separate ports for current and voltage measurements (this is a safety issue, both for the meter and for yourself).

Next comes the fun part: features! All multimeters have voltage and current meters (otherwise they'd just be called voltmeters and ammeters!), and most also measure resistance. There are a variety of other "extra" features depending on manufacturer and cost (e.g. continuity, capacitance, frequency, etc.).

Second-to-lastly, there are a ton of different types of probe leads, including alligator clips, IC hooks, and test probes. Can't decide? Here's a kit that has four different types!

Lastly, always check the multimeter maximum voltage and current ratings to be sure that it can handle what you want to use it for.

Step 2: Measuring Voltage!

A voltage measurement tells us the electrical potential, or pressure, across a particular component.

Voltage is basically the "oomph" in our circuit, so we want to avoid drawing any power from the circuit when we take a voltage measurement. This means we need to measure voltage in parallel with a particular component using infinite (or really, really high) resistance.

Using a multimeter to measure voltage across a component (or battery):

1. The black multimeter probe goes into the COM port, and the red probe into the port marked with a "V".

2. Switch the dial to the "voltage" setting (choose the highest setting if you have a manual ranging multimeter).

3. Place black probe on negative side of the component, and red probe on positive side (across, or in parallel with the component). If you get a negative reading, switch the leads (or just note the magnitude of the voltage reading).

Read the meter output and you're done! Not too bad :)

Step 3: Measuring Current!

Taking a current measurement tells us the amount of electricity flowing through a given component or part of a circuit.

To measure current, we want to measure all of the electrons flowing in our circuit. This means we measure current in series with a component using zero (or negligible) resistance.

Using a multimeter to measure current through a component:

1. The black multimeter probe goes into the COM port, and the red probe into the port marked with an "I" or an "A" (or "Amp").

2. Switch dial to the current setting (choose highest setting if you have a manual ranging multimeter).

3. Connect red probe to current source, and black probe to the input of the component, so that the current flows from the source, through the meter, to the component (in series with the component).

Read the meter output! If you're not getting a reading, switch to a lower setting.

Step 4: Measuring Resistance!

Measuring resistance is similar to measuring voltage, the biggest difference is that you have to disconnect the component from the circuit (otherwise the other circuit components interfere with your measurement).

Using the multimeter to measure resistance of a component:

1. Put the black probe in COM port, and red probe in the port marked with a "Ω" or "Ohm" -- it should be the same port as the voltage port.

2. Switch dial to setting marked with a "Ω" (may have to choose approximate range for manual ranging multimeter).

3. Place probes on either side of the component (orientation doesn't matter).

Read the meter output and you have conquered resistance!

Step 5: Bonus: Measure Continuity!

The continuity measurement checks if two points in a circuit are electrically connected, otherwise known as a conductance test. Before measuring continuity, be sure that the circuit power is OFF.

Using the multimeter to measure continuity:

1. Place black probe in COM port, and red probe in voltage port.

2. Switch dial to setting marked with an audio symbol.

3. Place probes at points you want to check -- if the meter makes a beep sound, it means the two points are connected.

Le fin!

Step 6: Go Forth and Measure All the Things!

Now that we know how to use a multimeter, get crackin' on all those at home, DIY projects!

To get you started, here are a few quick, practical, & fun projects:

1. Measure the resistance of your skin! Change the distance of the probe leads and see how resistance changes. Lick your fingers (or dip them in water) to see how moisture affects resistance!

2.Use the continuity setting to check if different materials conduct electricity.

3. Make a lemon battery and measure the voltage and current output.

4. Use the continuity setting to check if different materials conduct electricity.



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    52 Discussions

    Am a student learing Electronics and i appreciate the guide on how to use my miltimeter. Thanks

    2 replies

    If you get the Harbor Freight flyers, they often have coupons for a free meter. Its a lower end model, but its free!

    1 reply

    Ohh that's very good to know, thank you!!

    There are two other features of a multi-meter that are indispensable in my opinion.

    First is a built-in support on the back so that you can tip the thing up to almost vertical. This is so you can read it when it is impossible to have it directly beneath your eyes. If the meter has a light-emitting display this isn't so important but most don't in my experience. I just bought a DVM that has a back that folds out from the top so it would have been ideal in this respect if they had only put a stop on it to prevent it from falling over.

    Second is auto-turn off. If you don't have this your batteries will need recharging or replacing much, much sooner because we all forget to turn these things off.

    Actually, there is a third feature that relates to the second one. The required battery or batteries should be the kind that are rechargeable. AA's or AAA's or even a standard 9V.

    The DVM I mentioned in feature one was a fail on all three points. It couldn't stand on its own. It remained on until I manually turn it off. And the required battery is one of those stubby 9V's that don't come in rechargeable form. But I needed one in an emergency and it was only $24.95 at Radio Shack.

    1 reply

    Great additional information! Have definitely left my meter on more than once..


    2 years ago

    Very nice and helpful thanks
    And yes I would love for you to make an insatiable on a oscilloscope I have got one that I was given but I haven't a clue how to use it so yes please can you make one
    thanks and I look forward to see and read that one

    1 reply

    Glad you found it helpful! Working on a tutorial + video for an oscilloscope, stay tuned!

    Very useful instructable.

    A suggestion that reflects my status as a cheapskate: find another multimeter cheap enough that you won't cry if you lose it or drop it. If you go somewhere and it's raining or rough terrain, unless you REALLY need certain features, the meter from the cheap tool store giveaway will be plenty good.

    5 replies

    Thanks! Also thanks for the tip -- as long as high voltage/current are avoided a cheap meter is probably just fine.

    I don't think Uncle Ed was saying a cheap meter is just fine. He uses a more expensive meter but gets a second cheapie for rough/risky jobs.

    We can say I would use an expensive nice meter. One of the leads on the good meter was caught under something, when I picked it up. The lead held and my hand didn't and the meter hit the concrete floor. I didn't cry, but I was disappointed.

    The cheap digital meter from my toolbox will tell me if a 5VDC power supply is pretty close to 5V. The 10A scale has awful absolute accuracy but will tell me which flashlight cells are good enough to keep and which to throw away or recycle. It can tell if a wall socket is live and about the right voltage.

    (Checking the same battery on two cheap meters on the 10A scale makes me guess neither is a good number. The lower current scales are pretty good, though.)

    A Kickstarter here at home to replace the good meter...not likely, I guess.

    Aw, dang, that sucks about your good meter! The really nice ones definitely get quite pricey.. sounds like you know what you're doing so hopefully the inexpensive ones suffice for now.

    Also, try checking e-bay. Occasionally there are some older models that are still just fine and that are waay cheaper than the new ones.

    Sounds like you know uncle ed!

    Technically, when everything is the same, high voltage DC is more dangerous because it causes your muscles to contract so you can't let go. Although, of course, all high voltage and high current is dangerous so be careful regardless!

    Yet another minority report--it's a challenge to find ANY voltage, AC or DC, that cannot possibly be dangerous. In an early Electronics class, the professor told us if someone wanted to go in the worst way, he could do it using a little wire and the flashlight cells you could hold in one hand. No transistors, ICs, capacitors, coils, or anything. It would not be pleasant at all, but dead is dead.

    The point is to not get your body "involved" in an electric circuit. Yes, it's more convenient to get damaged by higher voltages and there are some academic distinctions between AC and DC, but proper care and behavior are essential. Thomas Edison's group spent a lot of money trying to convince the public that the AC advocated by George Westinghouse was dangerous and the DC his company was selling was less dangerous. The history is interesting, but the actual difference in "dangerousness" is irrelevant.

    The takeaway is to be careful and know what you're doing.

    Yes, absolutely, agree with you 100% on that. Regardless of AC or DC distinction, any voltages above 20V and currents above 100 mA should be treated with extreme caution. Double and triple check things, and always use the one hand rule!

    In case someone wonders why, this is because alternating current interferes with heartbeat (if current goes through heart, can cause ventricular fibrillation (heart tries to beat too fast, blood won't pump in veins pretty much at all)

    ) and it causes muscles to stiff so brains commands won't do pretty much a thing when you try to command your muscles. What else? Oh, and zap from ac feels awful....But, DC also has hazards, like charged capacitor, enough big energy and those are deadly as well, plus other places too. I might got few terms/facts bit wrong, but this is main princible.