How to quickly determine the polarity of your DC power supply with a multimeter 

Thanks for doing this quick video. I'm embarrassed to say that unless there is a red or + sign on the wire, I didn't know what tool to use to check the polarity. Thumbs up!

5 years later - just what I wanted to know. Quick and straight to the point. THANKS!

Thank you- it may be a "very elementary" video for you, but for me it is just what I needed to know right now!

Thanks for this quick and clear explanation for those of us who don't know the basics.

Short, to the point, tells us everything we need, gives a good video aid to the audio description. This video is perfect ! Very nice thanks! :)

This video helped a great deal. Can't get a simple answer to a simple question from the internet. It keeps answering questions you DID NOT ASK!! Your video provided my quick answer to my SIMPLE question that Google FAILED to provide- but they keep getting my money and continue to have the power to CENSOR whoever they wish.

I work with this guy in real life and I confirm he is one of the most talented Electronics Engineers I have ever worked with. ❤️

Thank you!! I'm rewiring a boat and have no idea about electronics and this was a huge help. Thanks for keeping it simple and easy to understand

Your video was the most clear and simple explanation on this topic i could find. You didnt assume that the audience knows certain things and thats great. For example you said set it to DC and also you mention the negative sign on the readout. The negative sign on my multimeter is not real clear so i was really confused until you mentioned it.

This is very quick, to the point and extremely helpful to those that are unsure or just outright forgot.

Thank you so much for this video! I completely forgot how to check which is which and was dreading having to watch some long drawn out video riddled with nonsence. I really appreciated that you were clear with instruction and direct to the point . Thanks you've helped me out today!

For people with no knowledge or experience in this field this is huge, thanks a ton for your very illustrated video.

For a moment i doubted how to check palarity. Short and precise thanks man.

I don't normally leave reviews on youtube, but you seem like a cool f'in dude. Thanks for the tip!

Just as i love tutorial vids. Straight to the point, no intro no outro. Ez likes from me.

its amazing how difficult this simple test was to find. All my searches ended up with some dumb thing about being marked with a + or a -. Thanks soooo much.

Thanks. This helped on figuring out what the polarity was on a transformer with only black wires.

I thank you! I did not know how to do this. Your video was straight-forward and helpful!

I couldn't tell which side of a home made/diy battery or cell is negative or +Ve, but now I know how to figure it out. Thank you so much for this informative video

I was on those many people that doesn't know about this polarity check, thanks alot

There's always room for elementary videos. Thanks for doing this many years ago.

very simple. yet i did not know this until I warched this vid. thank you

Thanks for the tip. I wanted to replace a 12v light but both wires were black!!! Your video clarifies how to work out which one is red!!

Just replaced the dc barrel plug of my laptop power supply and wires were red and black but I had my suspicions and now thanks to you I was able to see that it was backward. THANK YOU SOO MUCH FOR POSTING!!!

I connected my bilge pump and since it worked i figured the polarity was correct. Now that i know I will check it to make sure it’s done correctly. It just dawned on me two weeks later at 4 AM. Thank you!

Short sweet and simple. You answered a question and saved me from frying electronic equipment on my murder cycle. Thanks

I am a real beginner. And this helped a lot. I am not a technnician but I like to solve my little problems. Thank you.

Thanks Patrick! I did not know how to determine polarity! Now I definitely know how!

Wow! Thank you for actually explaining the concept that is easily understood. I don't know how many videos I watched and got nowhere. Great tutorial!

Thank you. Everyone advises getting meters and skip explaining simple things like this. I needed to rewire something and I wasn't sure which wire was positive and which was negative.

I would give you a thousand likes 👍🏾 if YT let me. This was informative and quick. Thank you.

I am not an electrician and I found this video in answer to a google search as I have an old battery charger with the battery clips missing. Thanks!

this is a good video, straight to the point, this saved me thank you so much for this vid. this is the way youtube should be.

Simple, quick. Thanks!

Thank you! Perfectly done video for electrically clueless people like me.

Basic First-Year Service-Station! Big help, Thanks!

Straight to the point of what I was wondering, thanks!

This helped a ton. I have a psu where the cpu connectors were cut off. And i bought an ohm meter for 10 bucks. This saved me a 40 bucks

Im one of those people, thanks this really helped me my diagram and wire codes were different on my golfcart headlights install.

Thanks. This was straight and explanatory

Thank you! This helped me, I just shorted an expensive battery doing it wrong, never again thanks to you!

Thanks man, helped me to find the positive wire on my 3d printer!!!

Elementary, perhaps. It certainly helped this non electrician. Thank you! 🙋🏼

Very short and simple explanation

just the information I was looking for. Thanks !

I did not know this quick test. Thanks! You saved me some led bulbs

Simples! Nice quick answer to a common question. Great video! Why would anyone down vote this great little tutorial?

Thanks dude, I have an old house, who ever did the wiring was an idiot. This video was helpful.

Thank you, I'm a novice in this, and this was quite helpful.

Simple, straight forward but helpful. Thanks!

Big thumbs up! I definitely wouldnt want to fry my freshly put together circuit 😁

Thanks for the video. I needed that if nobody else did.

This video save my life, it was quick and easy and very informative thank you so much

I didn't know how to do this, but after watching this video, now I do!

Big help thanks, I know it’s basic but I work on a/c not dc so thanks again

This the best answer so far

Wow...that's what I thought, but needed to confirm. Thanks!!!

Thanks mate! This is exactly what I thought to do but wasn’t sure. You just clarified it. Cheers

This is so helpful! I have been looking for just this simple information since last night. All the other sites went to deep. Thanks!

No markings on the original DC power adaptor. No relevant info on the unit I wish to power. The connector is damaged either on the supply or the unit and I just wanted to replace or hard-wire but had no idea what the polarity was. No colouring or markings on the wire either. Similar to someone elses comment; Every time I type the question about the devices polarity or how to check it in a search engine all I get are links to items I should purchase. Quick, easy and very instructive video. And one of the few multimeter video user to actually show clearly the setting you switched it to (I need that info to because I am that green) :) Thank you.

Thanks, quick, simple and accurate.

Thanks I'm trying to change out some over the counter lights, the wiring is behind the cabinets and nothing is labeled. a great help!

Thank you! Simple and clear vid!

Delightfully clear answer to a simple question. Many thanks. (And thanks for not starting with the moronic "Hey guys, wassup?")

Thank you, this helped immensly, I was hooking up an air horn on my motorcycle and needed to know which wire was which, the wiring diagram I had was difficult to interpret. Thanks again this is definitely going in my box of tricks.

Thanks! You did something nice for an old man newbie.

Video still helping!!! Thank you!!

Thanks for the tips. I only have analog multi-meter not a digital one so it'd only show positive voltage when correctly wired and null when reversed.

Thank you so much between this video and another I was able to fix the battery of my lawnmower.

Thanks, this helped me, i am not an expert, i assumed this is what i should do but was afraid to try.

Thanks for the video! Great simple explanation and it was exactly what I was looking for.

Thank you so much. Its so hard to find a simple answer that I can understand. Great video..

Thanks for this. Trying to find a switched live on my bike and after watching your video, I think I've got it figured out.

thanks for the video, this is like the equivalent of 'hello world' for programming.

Elementery is often best--GREAT SImple VIDEO!@!!!!

While this simple multimeter test may seem self evident or obvious to you, it was not to me. I need to splice some obscurely color coded wires together from different harnesses correctly, without frying something up. Ha, I wasn’t sure of the negative consequences of making an incorrect 50/50 guess…I assumed if it doesn’t work, I’ll just reverse it. It’s a good thing I saw this! Thank you, very well done and very helpful.

thanks, it helped, best way to make a video.

Elementary dear Watson. And very useful. Thanks!

Very helpful because it was to the point

Thnks for such a quick video, now I'm ready to do my project :)

Thank you. Quick and to the point that's what I like.

Thank you!!! I have a guitar amp missing a speaker. There are two speaker wires coming from the chassis. I’ll try this

I'm glad you make the video!!

Tahnk u man.. i am making e bike from aseembling old system. It helped.. Thanks uuu

fantastic. my boat has two wires for the bilge pump and naturally they are both black my light tester lights up either way but the bilge pump is likely to run backwards if I hook it up wrong and backwards won't pump water out. thank you so much!!

Thank you I definitely have forgotten how to determine the positive from negative. I have never had a need before now. And it's been almost 45 years since I was in shop class in school. Out meter testers were big heavy boxes back then. Technology has come a long ways. Lol Thanks again.

Just what I needed, thanks!

thank you for quick video. I didn't know how and only used multimeter to test voltage reading but during hooking up some 10 Gage wire for a cigerate lighter for the DC output to an accessory device I realized stupid you didn't lable the wires. and I'm running multiple sets for multiple connections one for a capacity monitor another for a DC to DC power supply (laptop) and another for a port to plug in my DC to DC phantom drone charger. oh and 2 extra USB ports step down very cheep circuits from Dollar store but I used all black wire and already fed the strands through my trunk under the seats into the area's I want. and forgot to lable them this simple method will help me to check polarity and I'm also going to double check on some things by disconnecting and reconnecting things separately so I know which is which and lable them I have a small setup solar panels batteries in parallel a 3000 watt power inverter and all the little DC to dc converters I can power my laptop for days or even make coffee whenever I want ofcource I could just make it at home too ;) or buy it when I'm out but this little expensive setup makes it so I can do it wherever and whenever I want. oh and I have all this set up from my car hahaha. 200 watts renogy panels mppt and soon to be adding even more batteries. all this is useless knowledge to someone else. it's all learning trial and error and interesting to me however. and eventually will use some of this on a RV and possible at home also. I'm always extra careful with the battery and connections least I short anything out. or explosion. I ordered so many fuses for everything. 300amp fuses 15 amp 10amp 30 am and placing them accordingly even the solar panel has a fuse coming from the positive to charge controller and from charge controller positive to battery array and waiting for my other Amazon order of the 300amp fuse to get here to place between battery and inverter even tho it says it already has fuses in it for short circuit protection. I'd rather blow my own fuses than replace ones in an inverter (haven't opened it to see what size they are yet anyway) the hardest part for me was positioning the panels on the roof and still keeping my sun roof and it being a curved roof. but I figured it out I feel like an odd ball the only one driving around my area with the frame panels on my car (not the flexible ones I decided after many reviews not to go flex route because I wanted something that would hopefully last a while the panels I have are rated to last... we'll see.... anyway..... Thanks for the help this helped greatly

Quick. To the point. Useful. Great video

Great video! Replacing RV incandescent courtesy lights with LED and both wires are white.

Great info for an electricity dummy like me!

Thanks buddy, it was a great help to me, and your absolutely right not everyone knows these things even the elementary stuff. Thanks again.

Cheers you've just made a simple thing simple for us all

The video is indeed elementary, but it doesn't make it less needed. Thanks

thanks bro you teach me how to distinguish the polarity positive or negative. easy i having fun..

Thank you, thank you, thank you! Took motorcycle battery out, need to put it back in but both cables are brown. Thanks again.

Quick and concise!

THANK YOU VERY MUCH. I’m one who knows nuts about this.

Thank you for the quick help! Exactly what I needed 😎

Quick and to the point thank you for your help.