How Do I Use a Multimeter?

CampFireJack

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A few years ago, I bought a Klein Tools electrical test kit that came with MM100 multimeter, a NCVT-1 non-contact voltage tester, and a RT100 receptacle tester. The non-contact voltage tester and the receptacle tester are easy enough to use. There are no moving parts and you can't really screw them up. What I find myself having difficulty with is how to use the multimeter. I actually have absolutely no idea. I wanted to test the voltage of a few car batteries yesterday so I pulled out this tool. When I looked at it though, I realized how inexperienced I was. It seems as though, instead of just turning the dial to voltage, I have to manually choose a range. My question is, for a car battery, which range do I choose? I would I even know this? For house wiring, which voltage range do I choose? How do I test amperage? How do I do anything with this device? Any help would be appreciated.

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Phoenix1

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I'll add the instructions for this multimeter below and I'll post a link to the PDF file on the manufacturer's website.

Basically, what you've got is a digital multimeter, DMM, or otherwise known in the field as just a multimeter. If you're a homeowner who enjoys doing a bit of electrical work, an electrician, or someone who's learning about or working on electronics, this tool is indispensable. These tools measure many basic things along with some more advanced aspects of electricity. Think voltage, current, resistance, and continuity. Since you know nothing about your multimeter, I'll start at the beginning.

If you look at the top of your tool, you'll see a gray screen. After you install your 9V battery in the back and turn the unit on, you'll notice that the screen displays a number. Usually, if you're not measuring anything, that number will be a zero. As you begin testing circuits and other things, this number will change and the screen will display the values you seek. If you take a look below that screen, you'll see the big knob that's sort of hard to miss. I'm sure this is where you're getting confused. At first, the selections around this knob can be overwhelming. Trust me, they're not. You just need to know what those selections mean. All you need to do is turn the dial to one of those symbols to select what you'd like to measure.

If you look closely at the symbols around the knob, you'll see that you can test various ranges of voltage, current (amps), and resistance (ohms). Back in the beginning, it was those ranges that I found most confusing. I can feel your pain.

When looking at the symbols on your tool, take your time. For now, check out the V selections that are situated above and below the OFF selection on the left side. There are a few V options where the V is to the left of a straight line with a dotted line below it and where the V is next to a wavy line. The first area contains the options were you can test DC or direct current. The second area is where you can test AC or alternating current.

If you look all the way at the bottom of your multimeter, you'll see three plugs. The center receptacle is marked with COM for common. This is where you plug in the black wire that came with your tool. To the right of center is another receptacle that's marked with V, omega, mA, and a few other symbols. This is where you'd plug in your red wire if you wanted to measure voltage, resistance, and small amounts of current or amperage. If you wanted to measure greater amounts of amperage, you'd have to pull the red wire out of the right port and plug it into the left port that's marked with a 10A. By the way, current is amperage and amperage is current. The words are used interchangeably. Anyway, with your tool, you can only measure up to 10amps before you blow the fuse. What you'd got is a less expensive model that can't test big amounts of electricity.

Your meter most likely came with a pair of regular probes. Be aware that you can buy a few different types of probes (needle, ic hooks, alligator clips, tweezer) as you become more proficient with your testing. Most of the probes you see for sale will fit in your meter, but check twice just to make sure.

When it comes to testing your circuits, batteries, or whatever you want to test, you'll need to choose a range. So let's say you wanted to test a 9 volt general use battery or a 12 volt motorcycle or car battery. Both of these types of batteries use DC, so you'd turn your knob down to the option where you'd most expect the voltage to be. In this case, you'd go down to the V with the line with the dashed lines beneath it and settle on the option that says 20. The 2 would be too low and the 200 and 600 would be way too high. The 20 option would offer you a nice clean measurement of your battery's voltage.

Just so you know, there are more expensive meters on the market that eliminate the need to select a range. These meters make life a lot easier for a lot of people. With these meters, all you need to do is choose the DC option (in this case) and it'll automatically find the range for you and then give you the voltage reading.

If you'd like to test the voltage in your house, that's totally possible with your meter. Turn the dial on the meter upward to the V with the wavy line. Since the voltage in your house is likely 120V, choose the 200 option. Then, using only one hand at a time (to avoid current going through your heart if you get shocked), insert the probes in the ports of the receptacle. You should see your meter reading be around 120 volts. It could be a bit higher or lower. That's to be expected.

The meter you've got can also test other things, such as ohms and amps. Setting these things up is slightly different than what I've already explained, so if you need help doing that, please let me know.


https://data.kleintools.com/sites/a...s/instructions/klein/MM100_Manual_English.pdf

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CampFireJack

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This is great. Thank you so much for all your help. One quick question. I'd like to test the amperage of a remote control car (RC car) motor. Can I do that with this multimeter?
 

Phoenix1

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This is great. Thank you so much for all your help. One quick question. I'd like to test the amperage of a remote control car (RC car) motor. Can I do that with this multimeter?
You certainly can. The first thing you'll need to do is determine what kind of amperage you expect the motor to use. If you don't have the exact current, then find the current of a similar product. If you look at the ports that your red probe can plug into, you'll see that the right one can handle up to 250mA. If you think the motor draws more current than that, then switch the red probe of to the left port. That one can test up to 10A. Anything over that and you'll fry your meter. Or at the very least, blow its fuse.

To test amperage, you'll need to attach your meter in series with the motor and the power source. So, instead of simply connecting the positive terminal of your power source to the positive terminal on the motor, you'll want to connect the positive terminal of the power supply to the positive port on the meter. Then, connect the negative port on the meter to the positive terminal on the motor. All you're doing is putting the meter in the path of the positive wire that feeds the motor with current. That way, your meter can measure the flow of electricity to it. Also, keep the negative wire from the motor directly to the power supply intact. You don't need to do anything there.

Finally, turn your meter's dial to the A with the straight line with the dashes beneath it. Choose the proper amperage option you expect to see. Then, turn on the power and watch your meter tell you how many amps are flowing to the motor.
 
How Do I Use a Multimeter? was posted on 01-21-2021 by CampFireJack in the Etcetera Forum forum.

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