Multimeters 101

May 22, 2013
As we were re-reading last week's post about the different battery types, we realized that we talked about checking the voltage on the battery but never once thought about needing to know how to run a multimeter. Since a multimeter is one of the most important tools for troubleshooting your ATV, we thought it would be nice if we threw together a few basic tips for the beginner. Old Multimeter Don’t worry, we aren’t going to be using this 70+ year old model. I’m a little higher tech than that. But before we go into too much detail, you might want to have a multimeter in front of you. Fortunately, they are very common and the web is filled with digital multimeters ranging anywhere from $6.00 to thousands. If you are looking for a very basic multimeter, I like this model you can find on Amazon. My current multimeter is an older Craftsman model 82175.

Current Multimeter

I bought this multimeter when I was in college in 2002 and it has since been discontinued. I also found this multimeter made by Klein on Amazon that is a very close match to the model that I currently use. Now that we've gotten some shopping out of the way, I can't wait to show you how to use this great tool. You could spend thousands on a multimeter with 50+ settings, but for most everyday use, you really only need three.

Voltage

Voltage Setting

The voltage setting is probably the easiest for most people to use and understand. A practical example of using the voltage setting would be to test the voltage on your battery. For some more great examples of when and why to use the voltage setting, check out last week's post on battery maintenance. If your multimeter is autoranging, make sure the dial is turned to the V setting. If your multimeter is not autoranging, make sure you are in the DC setting. Unfortunately, there is no standard for multimeters and because all models are different, you may need to refer to your manual to find the correct setting for a 12V system (assuming you are using the voltage setting on your ATV). On most models, the attachment for your leads will be color coded; i.e., the black lead goes in the black port and the read lead goes in the red port. If these are not color coded, the black will always go in the port labeled COM (for common) and the red will always go in the port labeled V (for volts, when you are using the voltage setting). The ports may include other labels as well. For example, the red port on my model is labeled V, TEMP, Ω, and CAP. For our purposes right now, we’re only interested in the V. Lead Ports For almost everything in the automotive world; i.e., cars and ATVs, you will touch the black lead to the negative (- or ground) and the red lead to the positive (+ or power). If you have good contact and the system has live power, this should give you a reading. If your meter shows a negative reading, you most likely have the leads crossed. Adjust the leads and try again. Volt Reading Most of the time (key word: most) you can use any of the frame, engine, or any metal part on your ATV for the black lead. If you have an off brand (Chinese) ATV, keep in mind that some of them do not use frame ground. I have found two so far and you can imagine the confusion and time it took trying to figure out what the problem was. The exception to this is if you are testing a wire for ground, in which case the black lead will be used as the test lead and the red lead will need to be on the positive terminal. That may seem obvious, but sometimes when we're comfortable working it can be the simplest mistakes that cost us time when we want to get out and ride!

OHM (Ω)

OHM Setting The OHM setting is used to see if you have the ability to flow electricity through an object or wire and how much resistance that object has. In laymen’s terms, you can use the OHM setting to determine if your wire has any breaks. Normally your leads will stay in the same ports as the volts. On an autoranging multimeter, you do not have to play with ten different settings, but you will have to pay attention to the readout. Autoranging multimeters are meant to be dummy proof. They automatically adjust the units to the one that best suits your reading. For example, if you buy a $5 hamburger, the guy at the counter will say, "That'll be $5." If he had said, "That'll be 500 cents," you would probably look at him funny. Well, so would an autoranging multimeter. M Ohms When you get your reading, keep in mind that the k stands for Kilo or 1000, the M stands for Mega or 1,000,000, and the Ω is straight ohms. So when you are reading your autoranging meter, if the display is 1.5 k Ω then the reading is 1500 Ω. If it is 1.5 M Ω, then it is really 150,000 Ω. And lastly, if it is 1.5 Ω , then there is no conversion. Not all multimeters support both kilo and Mega readouts. Like the hamburger example above, It doesn't really matter because it's just more than one way to represent the same number. Just keep an eye on the readout to make sure you are using the most accurate information. Something as simple as missing an M or a k could cause you to replace parts that don't need to be replaced (don't ask us how we know!).

Amperage

20A and Port

The amperage setting is used to verify the draw of electricity from the battery. This setting is particularly handy if you have a battery that is going dead over night; however, it is very easy to damage your multimeter in this setting. If you are at all unsure, it is best to ask someone or avoid this setting all together. While most good multimeters are fuse protected, the fuses can run up to $10 to $20 and can get expensive if you go through a few while trying to figure things out. If you're at all confused, let us know in the comments or shoot us an email and we'll do our best to help you walk through the steps. Notice that in the amperage setting, the red lead will need to be in a different port than we used in the voltage and OHM settings. On my model, the leads will need to be removed to turn the dial to the correct setting. Once the setting is dialed in to either A or mA, the appropriate red port opens and the previous port will close. This can vary among models, so be sure to check the manual that came with your multimeter. 20A Port In my day-to-day use, I have never used the mA (mili amp) setting. That small of a draw is nothing that I am ever looking for. Most everything will have at least a few mA draw. This is normal and is not usually enough to drain your battery. What I am looking for when I use this is amps of draw. So I always start with the 20A setting on my meter. On some meters, the setting will be 10A or 15A, my meter is a fairly high one. 20A Dial To test the draw on the battery, you will need to put your meter in line. By in line, I mean that it will be part of the circuit and will give you a reading of how many amps or the amount of flow that is going out of the battery. To put your meter in line you will disconnect the negative cable from the battery, touch the cable to your red lead on your multimeter, and touch the black lead to the battery post (the - or negative terminal). Amp Test This will give you a reading as long as you do not go over your fuse size. Again, this is an especially useful setting if you have a battery that is going dead very quickly. Even on multimeters with the most basic of settings, you can see how this one tool can be extremely useful in diagnosing your ATV. When you’re shopping for a multimeter, don’t get too hung up on having all the bells and whistles. At work we use a multimeter that has over 50 different settings on it and cost over $1800. I still don’t know how to use half of them because even in my line of work I never have a use for them. Know what you will use your multimeter for and purchase one that has only the features you need. It may be one of the most valuable tools you own, but it’s how you use it, not how much money you spend on it. And seriously, we’re dying to hear your thoughts. What model of multimeter do you use? What setting do you think you use the most? Are you brand conscious when you are shopping? Tell us in the comments below!

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