How to Test for Resistance? What is Continuity?

Most electricians know how to use our meters to troubleshoot power issues by finding voltage and amperage. But what about using them to find Ohms or Continuity? And what are those values good for? In todays episode of Electrician U, Dustin explains how to use your meter to get these values and what those values could be used for in the field.

🤘⚡️EU Learning System⚡️🤘
-Video courses on every side of the electrical trade (theory, code, safety, wiring, install, troubleshooting, leadership, and more)
-Practice exams for 2017, 2020, 2023 code
-YouTube videos categorized and searchable
-Audio lessons
-Forum
-Business version has admin portal and ability to assign learning to technicians and monitor progress
-Any business size from 2 techs to 2,000!

🎓💡CONTINUING EDUCATION💡🎓
-State Approved
-Video Based

✍📝PRACTICE EXAMS📝✍
-2017, 2020, and 2023 NEC versions
-Online Residential Wireman Exam
-Online Journeyman Exam
-Online Master Exam
-300 Question Online Code Cannon (not license specific, all code)
-Take as many times as you want
-All of the above come with printable PDFs

🎤🎧PODCAST🎧🎤
Spotify:
Apple Podcast:

📱👍SOCIALS👍📱

🎧🎹Music, Editing, and Videography by Drake Descant and Rob LeBlanc🎹🎧

#electrician #electrical #electricity

First, be aware that different meters will produce different value ranges. Most electricians in the field don’t carry our DMM (digital multi meters) with us everywhere. They are rather large and susceptible to damage, so are usually kept in the truck. Instead, we probably will have our Ampere Meter with us. An amp meter may read in thousandths of ohms whereas a DMM may read exactly what the ohms are. Something to keep in mind. Also, when using your DMM, make sure you are following the instructions for your particular meter and plug the leads in the correct ports on the meter. And finally, when using your DMM OR Amp Meter, do not check for continuity on an energized circuit. Most meters are fused to protect themselves, but checking for continuity or Ohms on an energized circuit will certainly blow that fuse.
Some meters will have the continuity and resistance setting at the same place on the dial. Some are different settings. For continuity, look for the little speaker symbol. For ohms specifically, look for the Ohms symbol (or the Greek letter for Omega) which looks sort of like an inverted horseshoe. To check for either continuity or Ohms on either meter, simply turn the dial to the setting you want and place one lead on one end of the wire (or whatever you are testing) and one on the other. If your meter howls at you, it is sensing that a complete loop has been made. If the meter is on Ohms vs Continuity the meter should display the amount of ohms worth of resistance.
But what are those values good for out in the field? Well, you could use the continuity setting to see if a fuse or filament type lamp (not a CFL) is good. Put one lead on each end and if there is continuity, then the fuse is viable. Or maybe you need to run wire to a piece of heating equipment that isn’t labeled as to its amperage. You could test across the heating element to see how much resistance it holds. Then using Ohms law, you can figure out how many amps it will draw and then you can base your wire size upon that. So, for instance if you had a 240 piece of equipment with a heating element of 5.77 ohms, by applying Ohms Law (Amps=Voltage Divided by Resistance) you will see that the equipment will draw 41.6 amps (plus any other items within the equipment like a blower motor).

[fsoileau]

As a GC and Plan designer for 40 years, I spend a lot of time in code and best practices, but I do enjoy watching new generations of tradesmen. I remember buying a trade book for $20 to $100 and 90 % of that book I already knew. It was that 10% was worth every bit of the cost. That is why Tradesmen that share on youtube are so valuable. If there is one single learning experience that is a well-watched video.

[Sembazuru]

A couple points you missed. I know that you should "never" do hot work. But just in case you are doing hot work, NEVER (I can't stress this enough) test resistance or continuity on a live circuit. Even if you are working with low voltage wiring or circuit boards. Don't test resistance on live circuits. You will be putting a power supply (the resistance meter) in an unexpected place in the circuit and you could either damage the circuit, cause it to do unexpected things, damage your meter, or any combination of the above. It's also best practice to isolate what you are testing for resistance from the circuit (disconnecting one end is sufficient, but completely removing is often best) so you know you are testing one device instead of everything that might be in parallel to the device. Best case, you get unexpected readings. Worse case, you power something in a way that shouldn't be be powered in that way and you damage it. In power electrical situations you'll probably never damage anything, but in low DC voltage situations (digital sensor inputs, troubleshooting PCBs etc) if you put a reverse voltage on some IC pins, you might damae that pin on the chip causing an even more expensive repair.

[worrelljb]

This is one of the most helpful videos you've made for me. There's so many electricians out there that know the basics and don't know ohm's law or use it to figure things out. I'd love to see more videos like this! 🤙

[joserodriguez-goxs]

You are hands down the best electrical instructor on YouTube, keep up the great content bro 🙌🏽

[liesejunh]

Nice video. A common usage for measuring resistance that wasn’t mentioned is to find a good ground location in a car. When using high draw electronics in cars (such as amplifiers) you want a location that has less than .02 ohms to the negative terminal of a battery.

[jeremyk]

I just did resistance testing in my pre- apprenticeship. So cool to see this video up. Thanks for your work.

[bakemore]

Your demonstration of estimating the length of wire on a spool is great. I like how you compared your results with information supplied in Table 8.

[Sembazuru]

At 5:20 you say that the high ohm bulb "doesn't look like a closed circuit", but the fact that there is a resistance value it IS a closed circuit. If it were an open circuit the meter would have shown OL just like it does when not connected to anything. Different meters have different thresholds where they will sound the continuity beep, read the manual of your specific meter to find out. I'm not sure if the Flukes that I use at work (unfortunately I don't personally one one) would have sounded the continuity tone on that flood lamp.
Also, note that many DMMs aren't in auto range when in continuity mode, so even if the meter shows OL in continuity mode, it may still be a closed circuit with a couple kohms of load. Continuity is primarily used to make sure wires (or wire-like divices such as circuit board traces and fuses) are acting like they should, and to make sure you don't have a short circuit between conductors that shouldn't be connected. That flood lamp giving the continuity tone shows why it is important to isolate what you are testing to make sure you are testing what you expect. For example, if you wanted to make sure there isn't a short in the wiring between a plug and a light socket, having the flood lamp installed in the light socket will give you a continuity tone leading someone who doesn't know to look at the DMM reading to think they have a wiring fault in the plug, socket, or wire. Leading them to waste time trying to find a fault in multiple places where there is none.

[BryceStLouis-etgn]

Thank you. Probably overkill for testing spark plug wires on my truck but still gave me a better understanding. I appreciate the free knowledge. I liked and subscribed

[DanielJPole]

This is a great video even if you know how to use a multimeter, it's still engaging, informative, well delivered and with useful tips and practical uses demonstrated outside of testing. Thumbs up from me 👍

[ChileVerdeDavid]

Thanks for making these videos. Real Electrical Education and not just entertainment. It's hard to get straight answers about this kinda stuff for some reason.

[bluej]

Great video, as a car mechanic we used to use resistance testing more then anything else. I still use it when working on PCs and stuff.

[jasonbezett]

Thank you for this Tutorial.
I understand a lot more now, and you started me on the right path

[dznutz]

just got my first personal multimeter, i really appreciate the lesson. the tip about the cable length is handy ill try out some day.

[ecospider]

If you have no use for the amperage settings then get one without. That way you only have 1 connection for each lead so you can’t screw that up and damage your multi meter.

I have purchased multimeters for friends. I really like the Uni-t clamp meters. There is only 2 connections for the leads but you can still use the clamp for current.

They have a $50 one that does DC current. Which I think is the least expensive DC clamp meter you can buy.

[isaacb.m.]

Hey, Electrician U, you should gives us a tour of all your Electrical Books.

[NeoN-PeoN]

Hey bro, I've always heard that there's a way to ring out cables where the ends are extremely far apart by using TWO multi-meters. Do you know how that's done? Can you explain it?

[jeen_rl]

Hi Dustin. It’s be awesome if you could do a video about different kinds of grounding conductors (EGC, GEC, bonding jumpers, etc.) and how to size them!

[applepie]

Great stuff, as usual. Thanks. You're the teacher I never had as a kid decades ago when I first had a hunger to understand such things. I have to say this, though: I can't "resist" saying that some of what you're showing us is "shocking!" Okay, I know, I know: keep my day job!

[willfergusson]

Great Video, always good to hit the basics sometimes!