Super basic multimeter overview

Good morning, fellow technicians. Uh, this is Mike once again with a few tips for you newer techs or guys maybe, and gals, considering a career in the trades and especially in HVAC. Uh, so today, just a quick couple of tips about your multimeter. You know, it's one of the devices that you're going to use the most in your career. I always say your 11-in-1, your channel locks, and your multimeter are the 3 tools you can probably get through your day with without touching any other tools. So this is also kind of complicated and seems a little bit scary for a newer tech, but I assure you, multimeter is nothing more than a tool for measuring electricity. And it's not that scary. It's just, you know, like everything, it takes practice. So I'm just going to go through in this video a real quick overview By no means is this going to be in-depth. I can certainly create more videos on each function going a little more in-depth, but the purpose here is just to give a quick little rundown. So you'll see with your multimeter, most HVAC meters will have a clamp on the top as well as some kind of a selector switch to select your different functions. Some, if you see right here, you have some red ones and some black ones. When you first put your selector on this setting, you're going to automatically start with the function that is in black. If you wish to cycle your functions, you would use your red button. See how on the display, the icons and the display are changing? That's because that's changing the different settings within that scroll wheel. This meter and many of them also have the ability to tell temperature. Some thermometers will plug directly in where your probes plug in. You might have— A meter that has little slits that a different— that your thermocouple can plug directly into. But again, you can change between Fahrenheit and Celsius by switching on your select button. Right now it's got temperature probes in it. It is definitely— actually, that is probably the temperature. Yeah, no, that is the temperature out. So it is actually accurately reading the temperature through my electrical probes. I didn't Actually know that it would do that. So, you know, we're learning every day. So just a couple of quick things. So you're gonna test voltage, is usually going to be your main thing that you're going to check. So voltage is potential difference between 2 points. So if you're looking, say, for a switch, is the switch closed? Meaning, is it conducting current? You're going to see from one end of the switch to the other end of the switch, you should see zero potential difference. If you're testing for current from one point to another point, whatever the source current is, whether it's 120, 24-volt, 240-volt, 208-volt, whatever it is, that should be your voltage. One quick tip, it's never just the stated voltage on the data tag because you may have other load devices in the circuit, which would actually be potentially dropping voltage. That's another video for another time. You also have resistance, which certain electrical devices will have a specific resistance they run at. Things like solenoids, or sometimes a relay might have a specific voltage that it wants to— or excuse me, a specific resistance that it's going to want to read. And if it's outside of that range, then you probably have a bad part. The other thing with resistance is it gives you a clue as to what's happening within the circuit. If you see some resistance across a closed switch, for instance, then that means you probably have some pitted or corroded contacts and that switch might be bad. On the other hand, so if you see your red dot, that is going to be your continuity. See how the little speaker icon pops up there? And that's just telling you that it's going to make a sound when the 2 contacts touch. Or when there's a, a path for current to, uh, follow. One thing to keep in mind, don't, don't check for— Don't check for continuity or resistance on an energized circuit. Uh, the reason is that your meter is actually providing a small current, uh, itself, and if that circuit is energized, it could actually damage your meter. Um, There's also another setting for checking diodes, which we're not gonna get into in this video. Um, and then you have your setting for testing capacitance. So capacitance is the ability— I'm gonna oversimplify it here and somebody's gonna correct me, but capacitance is simply the ability for a capacitor to quickly charge and discharge. Um, if It's within specifications, which will be on the data tag on the actual capacitor. Um, you— it will give you a reading of capacitance, usually measured in microfarads. There are different scales of farads, but microfarads tend to be what we're going to be dealing with mostly in HVAC, especially residential. You're going to be using this when testing a motor capacitor for your fan, your compressor, or for your, uh, Your blower. Um, the other thing is amps. You want to test how much current is being drawn by the load device, i.e., a motor or a heating element. Um, and again, that's going to fall within specific ranges, and you want to make sure that you're not running super high current. Like, let's say for example, if your compressor has a maximum running load amperage rating of 50 amps, and you're pulling, you know, 48 to 52 amps, you know that, that motor is probably wearing down, and it needs to be replaced. Um, so, the other thing is, if you are, if you are, uh, having a motor that's not energizing, and you, you put your clamp on the wire to test the amp draw, and you're not getting any amp draw at all, Then, that tells you that the motor is not turning, because it's not getting power. So, your, your problem is before the terminals for the motor, uh, probably a control board in that case, possibly. Um, up here, we have microamps, which is used in testing flame rectification, to verify that your flame rod is working and detecting flame in a gas furnace. Um, My multimeter has a non-contact voltage, um, setting. So, there is such a thing as a non-contact voltage detector, and all it's going to do is detect the electromagnetic field, um, from the wires. It's, it's basically all— its only purpose is to tell you, is there current present? And if there is, it's going to beep and light up. If there is not, it will not beep and light up. It is a useful tool, even just for verifying that you— maybe you're working on something, and you want to make sure that current is in fact cut, then, you know, it would be useful to be able to confirm that you have no, no current flowing through the circuit. The final thing I want to go back to, and I want to go back to amps. So again, back to those electromagnetic fields, you can use Your probes for testing amp draw, um, but you know, the most— the simplest way is really to put the wire. So, let's say you're, um, on heating, on your blower motor, the blue wire is used to energize the windings on the motor. You clamp this around your blue wire, or your neutral, which is your, uh, or common, which is your white wire on most blower motors. Just one wire, not both. Just one. I'll put that inside through. Don't clamp it on the wire in the teeth like that. That's not going to do anything. You need, you need these 2 contacts to make contact, and wire goes through the hoop, and when the circuit is energized, you're going to get an amp reading. So, um, you know, and one other small thing, which doesn't work very good, is my meter has a very, uh, flimsy flashlight. That's kind of a poor excuse for a flashlight, but, um, this one is also magnetic. It has spots for the, um, for the probes to be stored, although these are different probes. These aren't the originals, so they don't actually fit in the slots anymore, but, um, but the other thing that I want to show you on the back here is, this is a magnet, so you can actually stick it to the cabinet of your furnace, or air conditioning unit, To, uh, to, uh, you know, so you can see it better. Um, but one thing that I do recommend is keep your meter in— well, keep it off. It will shut off after a while, but keep it in the little pouch that it came with. You know, I've seen guys just stuff in their tool bag, stuff in their pocket, but honestly, it's— they're not expensive, they're not cheap. So, I want to keep my meter in good shape. I want to keep it protected, and I want to keep the meter wires protected. So, I always keep everything in the pouch. Okay guys, thank you. That's about all for today. Feel free to comment any questions or if you have any ideas for other topics you'd like to cover in future videos. Till then, this is Mike once again. Have a good day. Bye.