Instructables
Picture of EVERYONE Needs a Multi-Meter
A multi-meter can save the average person a lot of money over a few years, even though ladies who choose to buy one may not carry it in their purse when going out for the evening. You will often be able to solve many problems yourself in less time than it would take to get a technician to come to your home. This Instructable will show how to do that simply and easily.

I often meet handy people, both men and women, who do not go near to anything electrical because they are frightened of electricity. It is good to have a strong respect for electricity. It is also good to know how to make basic electrical measurements around the home. A multi-meter is the tool every home ought have. They eliminate the guess work from so many things and can save a lot of money. 

A suitable multi-meter for occasional use around the home and automobile can be had for less than $ 5. This link is to a very inexpensive meter that includes some functions found only on meters costing twenty times more just a few years ago. More expensive meters do not necessarily have more features. They give greater accuracy for professional work, and they are more rugged in their construction and durability.
 
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Step 1: Will I electrocute myself?

Picture of Will I electrocute myself?
No, that will not happen if you follow a few simple precautions. Most home uses of a multi-meter will be done with the power disconnected, or with very harmless low voltages. Regardless, you will always handle the probes by their well-insulated, completely safe plastic "handles." Usually, you will hold one in each hand.  

The black probe is normally associated with the ground or negative terminal. The red probe is normally associated with the "hot" or positive terminal. For household uses illustrated in this Instructable you can ignore all of that and use either probe on any terminal. 
aoke5 months ago

Thanks for your great article friend, i get new information, new ideas to do somethings, i hope you will share again, i keep waiting for next post, thanks. http://goo.gl/3hWprI

Phil B (author)  aoke5 months ago

Thank you.

spylock12 months ago
You are right,and as far as carrying one in the purse, ladies who may not be so bold as to carry the larger meters in the pocket book may be interested to know that Radio shack makes a nice little meter that is small around 4x3x1/2.It folds in half, it is kinda expensive,I paid about 30.00 for one a few years back as I needed it often for work,and it was small enough to carry in my shirt pocket.Very good advice,for all ,good thinking.
Phil B (author)  spylock12 months ago
Thanks. The photo of the meter sticking out of a woman's purse with her cosmetics nearby was a little tongue in cheek joke. I ran it past a lady preschool teacher I know and she thought it was pretty funny.

I have seen some pocket meters like you describe. They would be great for what you describe. My brother gave me a basic Radio Shack meter that does not fold, but is about 3/4" x 1" x 6" with an insulated fixed probe on the front end and a wire lead near the front end. It is small enough to carry in a pocket case for eyeglasses. I have often taken it with me when I travel.
spylock Phil B12 months ago
Sorry I didnt catch on,the reason I took it serious is because my mothers purse had a small screw driver set,keychain type multi tool,a credit card tool with many uses,well you get the just of it.She didnt however have a meter as she was scared of electric;its just my Pops and myself now,and we ran a small plumbing/drain cleaning company from 1987-2010.We are some do it ourselves kinda people.It is kinda funny now that Ive thought about it,but I think man and woman alike should at the very least carry a pocket knife,and I like your instruct.I hope ladies read it and take it to heart.
Phil B (author)  spylock12 months ago
There are probably a few ladies adventurous enough to use a meter, even if for a few basic things. Imagine a woman in a group including a few men. The TV remote does not work. She removes the batteries, pulls a VTVM from her purse and tests the batteries. In a few minutes the remote is working again. Some will admire and respect her. Others will feel outclassed and hate her.
spylock Phil B12 months ago
I would be of those who respect her for sure,I respect anyone who will at least take a wack at it,and those who dont know how,but ask get my respect as well.
Phil B (author)  spylock12 months ago
My wife was the first woman I ever met who knows what a wood lathe is. Her grandfather had one. I had bought one by saving my allowance in junior high. I still have it almost 55 years later.
spylock Phil B12 months ago
My mother knew what a forge was,and when I was making mine out of an old wheel hub,she told me that a wheelbarrow made a much better one,course I didnt know she even knew what a forge was,but her grandmother who raised her was a Hatfield,and up in west Virginia they had to make do.Ill tell you Phil,woman folks will surprise you sometimes,wont they?
J,R,D, Ltd1 year ago
Well, it did save you money in a way because you didn't have to pay a mechanic $60-$100+ an hour to find that problem.
Phil B (author)  J,R,D, Ltd1 year ago
You are quite correct. I am so accustomed to doing whatever work I can on my car that I do not even think about what I would have paid at a garage, not to mention towing the car to the garage. Thank you for looking and for your comment.
fretted1 year ago
I've got one of these meters from harbor freight i'm glad you wrote this Ible now i can use it where i didn't have a clue before how to start now i know

Thanks for a great Ible
Phil B (author)  fretted1 year ago
Those are not bad little meters for home use. I think I have one,too; but, I got mine at Home Depot and paid a lot more for it. I did this Instructable for people in your situation.
fretted Phil B1 year ago
Before i read this i really didn't have much of a clue how to use it on much thanks for this ible now i understand a-lot more about it and how to use it now if i could just get a handle on basic electronics i''ve got a-lot of ideas for LED's and and some cool steam-punk stuff I've fallen into this steam Victorian era kick and can't seem to throw it off i find some of these things very fascinating to build and goof around with and of course my nieces love the stuff ...
Phil B (author)  fretted1 year ago
There are some good basic books on electronics for the person who wants to learn on his own. There are also some good tutorial sites on-line. Here is a link to a pretty good circuit simulator that allows you to test circuits without the expense of buying real parts. If you go to this link, you can download an older version of the US Navy Electronics Course for free. I apologize for taking so long to respond to your comment. I wish you well.
fretted Phil B1 year ago
Hey np problem and thanks for the links i'll be checking them out !
Phil B (author)  fretted1 year ago
When I was much younger I was very interested in radio circuits and wanted to learn all about them. Years later I met someone who had studied electronics by means of a famous (at the time) mail correspondence course. He said he did not use most of what he learned, but found what he had learned about power supplies gave him all he used and needed. Many things these days run on 5 volts, which is the exact output of a USB port and also an old phone charger. Once plug-in power supplies contained transformers with real copper wire. Now most are switched mode power supplies. The older style allowed adding a variable voltage regulator chip configured to the exact voltage you needed. The new style does not work with the regulator chips (as best I can determine). I wish you well. You will have fun with your electronics learning. Be aware some published circuits have bugs in them and when they do not work, it is not your fault.
lol np = no
i was subscribed to a magazine that had free DMM coupons for harbor freight, i think i have 3 freebies now, one for my tool box, one for my car, one i gave to my dad. i have a more expensive DMM for my electronics tool box. i find a reason to use one all the time
i was subscribed to a magazine that had free DMM coupons for harbor freight, i think i have 3 freebies now, one for my tool box, one for my car, one i gave to my dad. i have a more expensive DMM for my electronics tool box. i find a reason to use one all the time
i brough a multimeter to school, because you never know ehn you might need it and people kept asking waht it was, i was famouse for a little bit
Phil B (author)  The nerdling1 year ago
One day they will wish they had been more like you and learned to use a meter. Thank you for looking.
I can't tell you how many times I have pulled my meter out only to have someone ask "what's that?". I have saved time and money for sure. Awesome and informative instructable sir.
Phil B (author)  jchamberlain1 year ago
Thank you for looking and for commenting. This Instructable attempts to explain uses for a meter I have found in everyday needs. I expect my experiences are close to those of others. Have you used your meter for some common needs I missed? Thank you again.
I have several TV monitors around the house linked with coax cable. Sometimes in order to troubleshoot them I use the continuity setting, I have someone short out one side using metal to touch the center pin to the outer connector. I then use the two probes to check my various cables to identify them.

This also allows me to identify which cable connects to which device at friends homes when helping them connect TV, satellite or other antenna.

Jeff
Phil B (author)  jchamberlain1 year ago
I have a spool of bell wire I use to connect to a wire at a wall box a couple of rooms away. The continuity tester or the Ohms scale lets me check for a break in the wire inside the wall. I once found a broken wire inside a ceiling box this way, even though there was no visual hint of the break. Thank you for the information on how you use your meter.
darman121 year ago
Just the title made me proud to own one :)
Phil B (author)  darman121 year ago
I am glad you already have a multi-meter. You will find a lot of uses for it throughout your life.
tim_n1 year ago
thanks for the overview. I've read this and the sparktronics tutorial and it all makes a lot of sense - though I didn't read anything about the different sockets in yours (10A?) for mains voltages?

Either which way, I'm off to do some soldering today and play with the multimeter to make an RFID arduino door lock!
Phil B (author)  tim_n1 year ago
Generally, you can do most of your work with the COM and + sockets. But, when measuring the current flow in a circuit you need to match the current type, AC or DC, on the dial with the current type in your circuit. You also need to use the socket appropriate to the current level expected. Recently, I wanted to check the parasitic current draw my automobile makes from its battery when everything is supposed to be "off." If the door has been opened recently and the interior dome light is "on," the current draw rose to 2.99 amperes. That meant I needed the dial set to the 10 A DC range. It also meant I needed to use the 10 A socket and the COM socket. If I had been measuring current in an AC circuit and it was expected to be more than milliamperes, I would have needed to use the same sockets, but change the dial to the 10 A AC setting. Which socket to use more concerns the type and level of current expected than the voltage.
Nano_Burger2 years ago
You can add this use to your list of common uses for a VOM (common for me anyway).

http://www.instructables.com/id/Attack-of-the-Killer-Strobes/

I use my VOM to repair cameras all the time. Luckily, I'm dealing with pretty low voltages and amperages to make it absolutly safe. The only risks are when dealing with photo flash capacitors.
I have a vague memory when on holiday with friends of breaking open a disposable camera and taking the AA battery out for my walkman. Saw what I thought was a 2nd AA battery and broke the camera open further to get it out.

Que burst of light from flash and large electric shock. It was the biggest capacitor I'd seen at 11 years old, same size as an AA battery.

Most people might have stopped playing with it at this point, but I recharged it and said to my mate 'go-on, touch those two wires'

He didn't die and he learnt a life long lesson on what not to touch in electronics.
Phil B (author)  Nano_Burger2 years ago
Thank you for your comment. I read your Instructable on checking trigger voltages of electronic flash units. I have two digital cameras, neither of which has a hot shoe. In the days of film cameras I did have a couple of Vivitar 283 units and used them with slave triggers for multiple flash. What I had really been looking to find was a way to use my 283s with a slave trigger that would get around the pre-flashes on most built-in flash units used on cameras like mine. I once found a schematic for a home built delaying trigger and built it, but it did not work.

When I did this Instructable on using an electrical meter, I hoped people would take the basic things I showed and expand their usage to special purposes like yours.
raziz1 year ago
i've seen a few old-timer mechanics turning on the wiper to check the battery strength when a car is having trouble starting.. i guess the wiper cranks more amps then the headlights.. once a car gone dead on me, even the instrument panel was blacked-out, it turned out the alternator had failed completely..
Phil B (author)  raziz1 year ago
I am sure that would work. I used to buy repair manuals by Motor's. They always had excellent general diagnostic and repair material in the front section of the volume. Another technique was to turn on the headlights and have someone attempt to crank the engine. The engine should turn over with the lights dimming only slightly.
Another example of how a multimeter (and troubleshooting skills) can save a few hundred bucks.
ac-dc3 years ago
It is not true that corrosion could be a problem if it is not visible. For there to be enough corrosion to cause a problem it is progressed to the point it is very plainly visible and there is no need to check it with a multimeter as it is obviously in need of cleaning.
Phil B (author)  ac-dc3 years ago
I am sure I remember reading that not all corrosion is visible. Before responding I did a search and found someone had problems with corrosion he could not see without removing the battery connectors. I have found the newer side post terminals can be quite corroded, but the corrosion remains covered and not visible from a quick glance under the hood.
This is true, corrosion can "hide" in the contact areas between the terminal and post. What your doing is called a "voltage drop test". It's a quick and easy way to locate where a bad connection is raising havoc. There are several good videos showing how to use a voltage drop to solve real world problems, including cars that won't start with battery terminals that look clean!
Phil B (author)  79spitfire3 years ago
Thank you. I assume the videos are at YouTube. Is that correct?
Yes, and they scattered about the web as well. Several auto manufactures are teaching their factory techs how to use voltage drops to more effectively repair cars and especially computer circuits in cars.
Phil B (author)  79spitfire3 years ago
I first became aware of the voltage drop test for auto battery connections testing from an old Motor's Auto Manual. That particular manual was published in 1969. Thanks.
I once replaced my car battery that seemed to have expired, with very poor response from the starter motor.  But the new battery made no difference.  

After carefully tracing volt drops, I discovered substantial corrosion on the engine block where the battery ground cable terminal bolted to it.  

Just cleaned and greased, and no more problem.   Thinking about it, two different metals, plus a bit of moisture and a current, is a beautiful recipe for corrosion. 

I always grease or oil nuts and bolts and electrical connectors when reassembling things, particularly on my car, both for preventing corrosion and ease of extraction the next time.
Phil B (author)  ElectroFrank2 years ago
Your information is very good. I knew a man back in the 1970s who had spent over $100 to have a bad ground discovered and fixed. To complicate things, grounding terminals are often hidden under layers of other things. Thank you for the important reminder.
You are right. I have watched my husband working on a small circuit board that would not work he took out the battery and used very fine sand paper on the contacts, suddenly the thing just stared working right again. This always amazes me. I have to say my first experience helping to fix something was my grandmothers toaster would not work. My dad took out his meter, tested good, then tried another plug and looked inside and scratched his head. The two copper leaf contacts were only very slightly brown like a dull penny. I offered maybe an eraser on the contacts. So he chuckled and let me try it. Then when we plugged it back in and it lit up, he was amazed...My dad was an electrical engineer...only time I ever got over on him as he was sure it was a broken internal element...lol
Apples and oranges, brass and copper especially degrade much more resistively and faster than lead, which is why lead is chosen, BUT we were speaking about visible corrosion too - brown like a dull penny is considered visible corrosion on copper.
Phil B (author)  NaturalCrafter3 years ago
If you are familiar with electrolytic capacitors, those are made by allowing an oxide to form on one side of the aluminum foil. It serves as an insulator and has the advantage of being thinner than paper or mylar film. It is a powerful reminder that oxides look like conductive metal, but actually insulate. Your father's experience with the toaster shows we look for what we expect to find, and sometimes that blinds us to what is.
ac-dc Phil B3 years ago
I cannot speak for what anyone else meant, but when I think or write about visible corrosion I do mean visible with/after the connector (is) disconnected.
askjerry ac-dc3 years ago
Sorry ac-dc but I am a Senior CET with 30+ years of experience... and I have seen equipment fail because of a micron or so of corrosion build-up. The metal looked shiny, everything seemed normal... hitting the contacts with some emery cloth and a bit of denatured alcohol fixed the problem. (Or sometimes a rubber pencil eraser... keep one in your toolbox!)

Depending on the current going through a circuit... it may only take a tiny film to provide enough resistance to cause a problem... in some circuits the addition of as little as 1K ohm is enough to cause a failure.

Jerry
http://en.wikipedia.org/wiki/Electronics_Technicians_Association
ac-dc askjerry3 years ago
The devil is in the details, I was writing within the context of the prior post. On that topic (battery and lights), you will not have sufficient corrosion to cause any problems if you cannot see it. The contact area is sufficiently large, the clamping force too, that even an invisible film is not enough resistance to be an issue with lights consuming only a single digit # of amps.

Of significance is also the metals used for the battery and clamp and the nature of the corrosion causing discoloration that would be visible. Further, if the film is so slight that it can't even be seen, the abrasive action of taking the clamped connector off and putting it back on alone would have cleaned it sufficiently for a light load like lights.

You wrote "1K Ohm" as being a small resistance, but between a battery terminal and the clamped connector where you cannot even see any corrosion, you will not find even three orders of magnitude lower resistance... less than 1 ohm.

As for dissimilar circuits and different connectors, I do agree in those circumstances a contact can be fouled by corrosion or other contaminants and cause a problem without it being visible, particularly logic circuits where you end up with a capacitive junction.
Actually I've measured considerably more resistance on fully functional battery clamp/post connections the worst I found was a full meg ohm. The residue from sulfuric acid is very resistive, often with the only conductive path being a single arc or two. Living in Wisconsin, the dead of winter proves these situations time and again, where a simple dirty post and clamp are the difference between the battery charging and going dead and freezing. This is going to become much more apparent as time goes on as autos become more Rohos compliant, as the lead battery clamp is now mandated for extinction and will be replaced with plated or tinned brass or copper clamps which will not hold up to the corrosion.
Car batteries are exempt from ROHS, the whole inside of them is LEAD plates. Other car electronics are also exempt. Note how ROHS was already implemented in the EU, changing global design materials where they are affected, but they are still lead.

With enough (a visible level) corrosion, you could measure 1 Mohm, but it would not be a "fully functional battery clamp/post" anymore. The key to the battery post and connector is that when you tighten it down, the areas where mechanical stress occur are the primary current path. If there are air gaps elsewhere, you'd have corrosion sooner in that area but should measure where the connector friction scrubs away the surface layer on the contact point.
Actually there has not been an automotive battery made with true lead plates in decades. They are currently manufactured with a lead grate, and less and less lead is used every year as larger and more powerful alternators are taking over the demand for continious electrical power, and the battery is no longer acting as a reserve capacitor while the vehicle is running. And the EPA is targeting the car automotive battery due to the health and environmental concerns involved in the recycling of them... Give the government an inch and they WILL take your testicles...
Wow nice misleading rant. No mention that the newer plate construction is a major reason that batteries now have more cranking capacity. in the same package. Auto starting batteries are a comprise, and where never, ever intended to handle any large part of a car's electrical load for anything but brief periods. Alternators have gotten larger because of an increase of the continuous electric load not because of less lead in the battery. Just as the hazards of manufacturing LA batteries have been been mitigated so have the hazards of recycling them been mitigated. You are creating a bogeyman about recycling LA batteries to lodge a complaint against the EPA. The stamped metal battery terminal clamps where being used on some imports before  RoHS.  Judging by the longevity of the brass battery clamps on old tractors I have had to use, brass would be an acceptable substitute for the lead clamps. The only advantage with the softer lead is the ease of restoring a clean contact surface.
Phil B (author)  askjerry2 years ago
Last week I had a great example of the point you are making (i.e. corrosion not visible to the eye can cause a circuit to malfunction). My '99 Oldsmobile Alero has an electronic instrument cluster that sometimes refused to come to life recently when I turned the ignition key. On some GM cars that symptom is the beginning of problems that will worsen until the car will not start. I fully expected I might be forced to spend for a new car. In my case, a set of unsoldered metal on metal circuit connections had oxidized enough over 12 years to keep the instrument cluster from operating. I cleaned the terminals and bridged them with solder. You can view the resulting Instructable here.
Howdy askjerry.  Thanks for the comeback to ac-dc as his comment could send a novice on a lengthy time-wasting chase "around Robin Hood's barn" by ignoring connections that "look" good.

I have been down that road myself, and what you describe is definitely a commonly occurring problem.
OH almost forgot... they are getting almost impossible to find these days but I also carry a couple old fashioned typewriter erasers (ink eraser in a wooden pencil type stick) for cleaning contacts, they are abrasive enough to clean the metal contacts but not so that they remove metal, and since they are sharpened in a pencil sharpener they are pointed enough to use on some pretty small packages.
Phil B (author)  sschoemann3 years ago
Thank you for your comments. And, the typewriter eraser you describe is dielectric so you can use it on "hot" terminals. Your comment about lead battery contacts being phased out reminds us that if something works the federal government is always ready to ban it for our good until they make a mess out of everything.
Jerry You speak gospel! Prior to becoming a full fledged EE I to was a CET (ISCET). I discovered a fantasitc product worth it's weight in gold on any socketed (plug in) type device that I have used on car batteries since I always have it on hand despite it's cost... DEOXIT. I keep the pen dispenser in my kit and the bottle on my bench (I'm a Ham radio operator, not one of those idiot design engineers who forgot what it's like to work on equipment in the field). It works and thats all that it takes in many instances... I cant count the number of times I've pulled a prom, eeprom, or any number of chips or micro procs, cards or so on that were flaking out, applied the deoxit to the contacts, reinserted them and all wierdness was completely eliminated for evermore. Not only does resistance cause problems but a minute amount of oxidation can act like a diode and even though it will conduct, it will "rectify" a 'stray' radio signal or two adding enough noise to really screw things up at the most Murphy's Law moment.
1k ohm? Do you mean 1m ohm?
With car batteries it is pretty rare for corrosion to cause problems without being plainly visible. There is a reason the terminals are typically made out of lead and not a better conductor like copper.
Mo, I meant 1K ohm.

Depending on the circuit you have... 1K ohm can make a huge difference. Let's look at an LED running on 12 volts.

An LED uses 2.2 volts and takes 20mA... or 0.020 amps. (typical)
So you take 12v and subtract 2.2 volts... that leaves 9.8 volts that needs to be dissipated. Okay... 9.8 volts divided by 0.02 amps is 490 ohms. Now... add 1K of resistance from corrosion... 1,490 ohms total.

9.8volts / 1,490 = 0.0065 amps... or 6.5 mA. That is a WHOLE lot less current than the LED expects... so it barely glows if at all. Now imagine a microprocessor that is connected to an input via an optocoupler... and the LED above is the one for the optocoupler... see the issue?

Jerry
1k ohm is huge for resistance (no such thing as a K ohm btw, lowercase is the proper terminology for kilo.) A car battery with a 1 k ohm terminal resistance would basically read near 0 volts from just the indicator lights in the car. Even 1 ohm would not let the starter budge.
I was referring to 1 milliohm, not 1 Megaohm.
Taerzik2 years ago
Thank-you for putting this together. I agree, everyone needs a multimeter (and the knowledge to use it of course.) I only got one a couple years ago and I'm still not fully proficient with it but it's been a really handy tool. I'd say most folks should know how to do basic soldering as well - it's pretty common to hear about common electronics that fail due to a faulty component, often a capacitor and how DIY'ers figured out how to fix it. Just the other day I re-soldered a loose capacitor in a faulty power supply - saved myself somewhere between $10 -30.
Phil B (author)  Taerzik2 years ago
Thank you for looking at this. Soldering is a very useful skill. One of the most helpful things I learned about soldering was to heat the parts of the joint so that they, rather than the soldering iron, make the solder flow. That is still a good principle, but now many of the semi-conductor parts are very heat sensitive and care is needed to avoid ruining a component. I yielded and added a low-wattage soldering iron to my old soldering gun. Congratulations on saving your piece of equipment and saving some money.
A couple of safety tips.
If you have to open a breaker panel/bus box, BEFORE you open it, touch the door with the back of your hand. An electric shock will cause you muscles to contract so if, by chance there is a problem and the panel is HOT, the electric current will force your muscles to draw your hand AWAY from the hot panel. You will get a shock, but will live to tell about it.
Next, in choosing a multi-meter, get the highest category you can afford. The higher CAT rating the better protection if something goes wrong. The higher protection will help keep the multi-meter from exploding due to a power surge. CAT IV is the best option if you can afford it.
Finally try to hold the leads in ONE HAND when testing higher voltage circuits such as 110 AC. If something goes wrong only your hand will be affected. If you happen to be holding the leads one in each hand and there is a short, the path of least resistance is from one hand to the other and your heart just happens to be in that path.

I see the one hand rule and CAT ratings were covered in earlier comments, sorry for the repetition. One other suggestion if opening a panel is to wear safety glasses or a face mask and cotton...NOT POLYESTER...long sleeve shirt. YES I am a safety freak, but my college instructor could not emphasize safety enough... "Gentlemen, when I was growing up in Argentina, they gave me a light bulb and two wires to test circuits. You must know how to do this safely and memorize this information so you do not get electrocuted!"
I have a couple meters and I ofter use my Simpson analog meter for certain situations where a digital meter is not fast enough to register an electrical pulse such as in a fuel injector system.
Phil B (author)  nowuknowjack2 years ago
Thank you for your comments and for your emphasis on safety.
AntMan2322 years ago
Great instructable, I used a multimeter only this morning. I am 15, and a great fan of the AVO8 analogue meter, which I picked up for £2 at a car boot sale.
Phil B (author)  AntMan2322 years ago
Thank you and congratulations on getting a good bargain.
80$man2 years ago
Excellent Instructable! 5 out of 5!
Everyone must have a multimeter, it is a very good learning tool!
I have got 'n poor/cheap one 'currently'... must find a replacement, any suggestions? 3-phase capabilities would be good...
Phil B (author)  80$man2 years ago
Thank you. I am not aware what makes and models are available in South Africa, although I am often surprised that the same things are often available in other nations that are available in the USA thanks to international marketing. In the USA the name Fluke is very well-respected for excellent meters of a professional grade. I wish I could be of more help.
80$man Phil B2 years ago
I found a Fluke supplier in Cape Town, 35min away! Thank you for your reply!
Phil B (author)  80$man2 years ago
You are welcome. I hope it works out. Fluke meters are not inexpensive.
pfred23 years ago
It depends meters can also lead to even more expensive service calls as well contingent on the outcome.

20 years is about the time frame when Rat Shack made the corporate decision to put their weight behind meters as opposed to oscilloscopes. There was a time when The Shack sold scopes too. I often wonder how different the world might be had they chosen otherwise?

They're a poor excuse for a phone kiosk now so it serves them right.

/me hugs his TEK 2336 with the Y option ... Oh yeah!
scope.jpg
Phil B (author)  pfred23 years ago
This Instructable is for the person who feels inadequate to do more than change a fuse. I have played with a virtual oscilloscope, but do not feel like I know what I am doing.
johnny3h Phil B3 years ago
I'm an electrical/electronis hobbiest with less ability than you and do appreciate your efforts to "keep it simple."

From reading the comments transactions to this point it's becoming obviousl that there are some people who just refuse to stay with your goal, and instead have to "display" their expertice!!!!!  Such a shame.

In order to not miss something in the comments that would be helpful to me, I am forced to wade through all of these wise-acre comments, which as you alluded to from the beginning,  are extremely intimidating AND confusing.

It would be nice if these "butinskys" would just stay out of 'ibles intended for the novices.

Again, thanks for the efforts to keep it simple.
static johnny3h2 years ago
Respectfully I believe most hobbyists are capable of recognizing, and ignoring comments go beyond they want to learn. The problem with expecting the buttinsky to butt out, those hobbyists who desire to learn more would miss that opportunity if the those leaving the more experienced did butt out. You yourself indicate you read the comments in hopes to find something useful.
pfred2 static2 years ago
You can lead a human to knowledge but you can't make them think.
Phil B (author)  johnny3h3 years ago
I do admire and respect the folks who commented here about very technical things related to using a meter. They know more than I ever will. Thank you also for your appreciation of a simple approach that frees people to benefit from a multi-meter without a lot of theoretical background knowledge. As you noted, I simply want people to be able to use a meter for basic things that can save them a lot of money and give them a lot of satisfaction.
pfred2 johnny3h3 years ago
Hey thanks for the wise acre comment!
pfred2 Phil B3 years ago
Unless you are doing electronics an oscilloscope isn't too handy. Though you can do continuity and voltage with them. They are more for signal analysis.

Oscilloscopes are a lot like old time TVs with horizontal and vertical hold knobs. Just the "stations" you tune to are pretty 2 dimensional.
back up the truck! You CAN NOT do continuity checks with a scope. A scope can only be used on powered circuits. A continuity check is done with a self powered test instrument on UNPOWERED devices, as if using an ohm meter.

The fact is a scope can not do any tests on unpowered equipment, and this is it's only downfall, virtually EVERY other test can be done with a scope of suitable band width providing the user knows how to use it. In fact they are indespensible for checking for noise on the AC mains that creates havoc on computers.
Accept some personal responsibility and make sure you have the proper equipment before performing tasks. Like a signal generator if you'd like to test continuity with an oscilloscope or maybe an adequate power supply if you want to use public utilities to power your computer hardware.

Many scopes are in fact sold without so much as probe leads and that'd make continuity testing rather problematic in many instances as well I'd think! Some of us take it upon ourselves to put together what it takes to get the job done though.

Real men don't back up we drive through!
static2 years ago
Theeevlog over ate you tube has review of inexpensive DMM. Be warned warn that Dave Jones likes to have fun, but his meat,and potatoes of the content is great. His how to solder series (electronics) is hands down better than most here on instructables. I love to have a Fluke, but I'm going to have to settle for an Extech model if I want a true RMS meter. Something I should get if I plan to troubleshoot 120VAC circuits powered by an inverter.
ProCactus3 years ago
Dont repair the cord. completely replace it.. Though you must really love your toaster to do this.

Looking at the back/Bottom of the toaster. Im going to use OHMS Law to tell you what the reading on the meter should be close too.

My toaster is 220-240Volt 700Watt

remember R(OHMS) = V (Volts) / I (Amps) .... .... And P(Watt) = V * I .... .... And I = V / R
(Dont be put off by whats in the brackets or the capital letters), Have a go at it.

..so Whats my current flowing though the toaster ?
Is... .. I = P / V
IE. .. . 3.18Amps = 700W / 220 Volts
...............................................................................................................
... so the toaster uses 3.2Amps at 220Volts
OHMS law tells me that R =V / I
. . . . . . . . . 220 / 3.18 = 69.18Ohms


= = = = 69.18 Ohms at 220Volts

That is what ( I just farted ) the resistance should read on a typical 2 slice toaster at 220Volts


A toaster at 700W at 110V will be
.. .. 700 / 110 = 6.36Amps
.. .. . 110 / 6.36 = 17.3 OHMS
= = = = 17.3Ohms at 110Volts


Its not hard, Use Ohms law to check before or after. The result will be a little different but will be in the range. And besides if it is actually broken it will read ZERO ohms.

-Cactus
due to an error by the system I couldnt reply to your subsequent post. You seem to got what I was getting at. While voltage and current are irrelevant to resistance, resistance is 100% relative to current, (but not voltage, the other constant in the equation). While voltage can be changed easier than resistance, these two are the constants that determine current. And at the same time voltage and resistance have no direct relevance to each other. They simply "inter act" to determine current. Current on it's own can not change without a change in voltage or resistance, hence V and R are directly relevant to the current, and theoretically voltage and resistance are fixed without external actions changing them (in the real world we know that battery supplies weaken, and resistances are affected by temperatures but that is beyond the scope of the discussion at this particular point).

A correction however on the statement you made "And besides if it is actually broken it will read ZERO ohms".... while its a common error due to no reading on the meter, it isnt zero ohms, it's infinite ohms or an open circuit. I'd say 99% followed what you meant and didnt even catch that. I didnt until just now, passing over it, knowing what you meant... It's like proof reading your own work, it just doesnt help since you know what you mean. But keep up the good work!
Phil B (author)  sschoemann3 years ago
I appreciate the knowledge and experience all of you have, but be aware you have gone way beyond the original intent of this Instructable, which was to avoid highly intimidating theoretical discussions of such things so that a very non-technical person could gain the confidence safely and profitably to use a multi-meter for the performance of a few simple tests around the home and automobile in order to save much trouble and money. My aim was to remove intimidation, not add to it.
Yeah, Thanks. Your right :)

I think i was drunk when i wrote that.
To simplify, Voltage and Current are irrelevant in reference to resistance. The resistive load is always a constant regardless of current or voltage. However between the three values, you only need two of them to calculate the third. The power (wattage) can also be calculated if any two of the values are known, since you will be able to calculate the third value if it happens to be needed. as power is simply the voltage multiplied by the current flow. (Didnt mean to step on your explanation ProC, we just tend to forget that some people dont understand how simple Ohms law really is, and those of us who use it every day thake the power relationship for granted)
Urm, Im not quite sure what your saying there.
But its all good.

Resistance is directly relevant to Current and Voltage.

R = V / I

One person already commented 'skrubol' about the Resistant changes as metals rises in temperature, is true.

But im not sure how to measure the impedance of a wire glowing red hot . So im not sure how much of a difference it makes.

Maybe heat a wire with a lighter and measure its Resistance??


Phil B (author)  ProCactus3 years ago
Replace the cord if you wish, but most of the wear is within a couple of inches of the plug. I have replaced many plugs and the rest of the cord was fine for many years. Remember, too, my comments on that were in relation to other corded devices, too, like low voltage electronics chargers. Once I cut back about two inches of cord and soldered back the plug on a high-dollar voice recorder charger. The owner would have shelled out $35 for a new charger. I had it working again for him at no cost.

If you look closely at my 120 volt toaster in step 10, the resistance reading for my toaster was 18.9 Ohms. Your calculations based on Ohm's law are very close. But, I did not want to overwhelm the intended reader of this Instructable with Ohm's law. This Instructable is for the person who is a bit timid about even using a multi-meter.
OVERLOAD???? Ohms Law is an absolute necessity for so many reasons, first off and foremost SAFETY! You HAVE to understand the nature of voltage, current and resistance to understand what is safe and what is dangerous, from electrocution risk to fire hazards. If domeone doesnt understand that current flows and voltage is the force behind the flow and resistance is the limiting element. These are critical for anyone who is going to even open any device that runs on 120...
Heating elements may not read exactly what you expect. Resistance changes with temperature (with metals it goes up as temperature goes up, some things are the opposite.) Incandescent light bulbs for instance read much lower resistance through a meter than using ohms law would make you think.
If it's reading zero ohms it will be tripping the breaker. If the conductor is broken it will read infinite ohms. Most meters represent this as 0L or sometimes as a 1 or 0 with no extra digits. Basically it will look the same as when the leads aren't connected to anything.
Incandescent bulbs, as a general rule (Most but not all) are not purely resistive, the majority of their impedance is actually due to inductive reactance. If you look closely most have coiled elements, this supplies a sufficently reactive load until the element heats up enough for the pure resistive element of the load to increase due to the heat... A typical ohm meter wont read this.
Phil B (author)  skrubol3 years ago
I made the same mistake regarding zero ohms when I meant an open circuit and infinite ohms inside the body of the Instructable, but also caught it about the 2nd day it was posted and made the correction.
=) "I just farted" - Awesome!
I am really enjoying this as I have not done much with the knowledge since I took the class. Love the Instructables and the comments.
Phil B (author)  NaturalCrafter3 years ago
There are quite a number of Instructables dealing with electricity and electronics. Many are related to LED projects. If you are interested, here are some I have done: repairing an electronic fly swatter, building a timing light for an automobile engine, using diodes to drop a voltage for keeping a battery charged, automotive 6 or 12 volt battery charger, using a multi-meter to test a transistor, making a GPS power adapter work again, how 3-way and 4-way switches work, and charging CD player batteries without removing them from the player,  There are also many Instructables on DC power supplies, solar chargers, and other chargers for low voltage devices. I hope you enjoy some of these.
Thank you! I am also sending a few links to my sons face book page so he and his friends can take a look
Phil B (author)  NaturalCrafter3 years ago
At last I have mastered the art of shameless self-promotion cleverly disguised as being helpful! ;-) I forgot to mention a number of Instructables by various folks on high voltage projects, like Tesla coils, and various kinds of audio projects, like small audio amplifiers and small speakers. Another favorite topic area is making arc welders by ganging two transformers from old microwave ovens together. And, there are the numerous Arduino (a personal digital processor) projects.

Several times I thought I wanted to learn electronics theory really, really well. Yet, I found my needs were always merely for some DC power adapter between 3 and 12 volts. As long as I knew how to do those projects, I was pretty well set.

I hope your sons enjoy the links you send.
ac-dc3 years ago
If your A/C has blown a fuse DO NOT replace the fuse before you have repaired the damage that caused the fuse to blow. A multimeter isn't all that handy for homeowner A/C diagnosis unless you have in depth understanding of the components, it usually isn't a circuit or fuse problem, more likely ("IF" electrical at all) a failed motor start capacitor, motor short, compressor seized, control board, etc.
Air conditioning Blows fuses and breakers, this is a given. Without going into the theory of physics on how and why they operate, you need to understand that over time these safety components weaken with use and heat. WHen the entire grid is under stress the voltage sags, because the motor in the fan and compressor are inductive devices, when they slow down due to sagging voltage supplies their impedance tends to drop rather substantially, thereby allowing greater current flow in the circuit. Manufacturers try to derate the protective devices on the input line to protect against this but can not fully cover all situations without compromising safety. So they eventually do blow open. Some use self resetting breakers, but breakers weaken every time they operate. Fuses will eventually blow no matter what. When A/C first starts up and every time the compressor kicks in, there is a massive momentary demand for current, which is why the fuses used are of the slow blow blow variety. But these eventually blow because of the design and demand on them. So you have to balance judgement with the attempt to repair. For example, if it's an older unit, it could very likely be a fuse but if it's relatively new, look for cause, since it generally takes time to weaken protective devices.
Phil B (author)  ac-dc3 years ago
One hot evening our A/C would not run. One of the fuses had blown. There was no further damage. It ran just fine after installing a new fuse and continued to do so. We have had other A/C failures. I checked the fuses and found they were good. Then we knew we had to call someone for repairs. The last time it was a burned out motor.
londobali3 years ago
yup.. that the most common failure in sockets here where i live..
so common in fact, that before i check the bulb/CFL, i'll try to lift the tip first..
:)

BTW, i think it's worth mentioning that checking the socket "live" with a probe could be dangerous if you dont have steady hands.. a small slip could short circuit both terminals inside the socket and give a good spark..
Phil B (author)  londobali3 years ago
You are exactly right. At one point I thought about suggesting all but the very tip of the probe end could be covered with electrical tape to make the job easier. The times when I needed to test that way I was a little nervous about it, but always managed just fine.
in instances like this it's worth it to invest in a set of leads that have self covering tips. These have spring loaded insulators that cover the probe and retract when the tip is pressed into something so that only the point comes into contact with the circuit under test, preventing any accidental contact of any kind with the probe tips.
But in the bigger picture this points out the fact that it is wise to invest in extra leads/probes, allowing for specialized clips, clamps, connectors and so on allowing you to connect the meter in semi-permanent manners, to pierce insulation to test for voltage without exposing wire and so forth.
And there is no other simpler way other than just replacing the holder.
Phil B (author)  devalpha_13 years ago
That is true. I did not want to get into that for the sake of readers who do not yet feel comfortable with changing electrical parts.
skrubol3 years ago
Diode check won't always work with LED's. Rectifier diodes (like used in the phone and power supplies,) usually have a voltage drop of .3 to .7 volts. LED's are typically between 1.2 and 3.6 volts. The meters I have generally won't recognize a blue or white LED (they are 3+ volts, the other colors are usually lower,) as a diode.
Also many LEDs are bipolar (two different colors depending on the polarity of bias), and the high brightness leds are actually integrated circuits that are LED drivers that power the internal LED, and the list goes on and on and on...
Phil B (author)  skrubol3 years ago
Thanks. Reading the LED bulb in my Maglite did work for me this time. I appreciate the information. I may need to remember it one day when when the LED does not respond in the same way.
polkovnik3 years ago
Checking household AA, AAA and 9V batteries just by measuring the voltage does not give a reliable idea of whether the battery is good, useable or bad.

A much more reliable method is to make a very fast measurement of the short circuit current. Do it this way:

1. Put the test cables in the COM and 10A jacks

2. Select 10 A

3. This measurement must be made as fast as possible, as prolonged measuring will empty the capacity of the battery. It can be done in on second!

4. Put the test leads to the battery PLUS and MINUS.
A brand new battery will read 3-4 A
If the reading is above 1 A, then the battery still has some life back in it
If the reading is below 1 A, it indicates that the end of the battery life is very near.
the proper way to test a battery is under load not shorting it out. This is shorting it out, and you risk ruining a good battery. Instead use a lightbulb rated for 1.5 volts connected from the positve to negative terminals of the battery and check the voltage across the bulb. You can substitute the bulb with a resistor BUT the bulb will do two things, first it will supply the necessary load, second if it barely lights you have just saved the time it takes to read the meter, the battery is obviously deceased,,, Also this is only good for AAA, AA, C and D cells. 9volt obviously will need a bulb rated for 9 volts. Short circuit current should never be read on Lithium ot any rechargable batteries as this can cause them to explode or burn through the internal lead to the positive contact
Phil B (author)  polkovnik3 years ago
Interesting. Radio Shack has some information on using a resistor as a load when checking a battery at this link. There is also a discussion of pros and cons related to measuring small batteries under load at this link. Some there want to measure under a load, while others say measurements of common household batteries will not vary enough to be a concern between using a multi-meter directly and using a meter in parallel with a resistance load. If a resistance load is used, it should fit the milliamp-hours rating of the battery under test. Certainly, all of that goes beyond the scope of what I envisioned in this Instructable for the intended reader.

i am a specialist in repairing electronic products, every product has a fuse, the thing to know, is that most of the time the fuse blows because another part is faulty, if the fuse blows again, you should put a new one in, simply bring it to your local electronic repair store
Phil B (author)  pbergeronronronron3 years ago
I know what you say is absolutely correct. However, in the events I mentioned in the body of the Instructable, replacing the fuse fixed the problem and there were no further events or problems.
benner813 years ago
If you don't have a helper to turn the key, turning on the headlights will also put a moderate load on the battery.
Phil B (author)  benner813 years ago
True. I had forgotten about that. Some also use the headlights without a meter as a test. They let the headlights shine on something, like a wall (if possible). The headlights should be bright when "on" but the engine is not cranking. If they dim only slightly when attempting to crank the engine, the battery is good. If they grow very dim or go out, the battery needs charging, maybe even replacement; or one of the terminals is corroded. Another good cross-check is always to look at the life rating of the battery (36 months, 48 months, etc.). Then check the punchouts for the month and year the battery was installed. If the battery is at or past the normal life expectancy, remove it and get a friend to take you and it to an auto parts store that will test it under load for you. You will likely return with a new battery. Thank you for your comment.
ac-dc Phil B3 years ago
Most of the better quality batteries I've bought in past years (72+ month life rating) don't last that long, they're essentially selling an insurance policy so you'll take it back and buy a new one from them instead of somewhere else to get the pro-rated discount on the new battery.
i was actually lucky enough to come up on a fluke 27FM at my local thrift store for 8.99 works great. not sure if it needs a calibration but i checked a few things and its more than accurate enough for my purposes.
Phil B (author)  unaffiliatedperson3 years ago
Congratulations on your bargain acquisition. I am not aware that digital multi-meters ever need calibration. Perhaps someone else with experience owning a Fluke can speak to your question. I have had experience with four digital multi-meters, three of which came from Radio Shack over the years. One is similar to the $5 meter linked early in this Instructable. Nothing was mentioned on any of them about calibration. Keep fresh batteries in it and you are probably good to go. Thanks for looking at this and for commenting.
ac-dc Phil B3 years ago
Fresh from the factory a Fluke meter comes with a certificate of calibration. Any meter will drift a little bit in accuracy over time, but the worst are the generics which have poor QC so they not only aren't very accurate when brand new, they may have sloppy cold solder joints that worsen with time (or abuse and the flimsy plastic casing lets the circuit board flex too much, especially after ROHS caused a shift to lead free solder), use components more subject to thermal drift, and some also have generic electrolytic capacitors that don't age well.


Otherwise it depends on the use. Quite a few uses don't need utmost accuracy as I'm sure you are aware, but in others being off by 0.1% or more is a problem. If the use is tied to critical precision measurements a meter ought to be recalibrated every couple years just to be conservative, though they don't drift much in a decade.

From what I vaguely recall about a Radio Shack meter I have around here somewhere is there is no allowance for calibration, it can't be reprogrammed or POTs adjusted as there are none. Maybe their current generation can be, I haven't seen the insides of any recent vintage Radio Shack meter.

To some extent it would defeat the purpose to have a meter bought at low cost, (and thus only moderate in value) calibrated... the service typically costs $50 or more so that goes a long way towards a new meter.
ARJOON3 years ago
i've burnt over 10multimeters in 5 years.
i remember how i burnt my first one. it was when i monitor the charging of a very huge capacitor bank. damn cheapies meter
Phil B (author)  ARJOON3 years ago
I burned up an old analog meter many years ago when I had the dial set to something other than volts and plugged it into a 120 volt AC outlet without thinking. Since acquiring my digital meter I have blown the protective fuses when I did something dumb, but they did their job and saved the meter. Other than those two experiences, my meters have had a very good longevity. The meter featured in this Instructable cost about $55 in the mid-1990s. A few years earlier my meter or something comparable would have been about $80. I have not done much pricing of meters since.
criggie Phil B3 years ago
Try searching at www.dealextreme.com - they have cheap meters and do free freight.
Naturally they're not going to be up with fluke or anything, but good enough and the price is right.
tbt10f criggie3 years ago
Actually they do have some Flukes there. Just under Chinese contract to there is no warranty with them.
criggie tbt10f3 years ago
Heh yeah - F1uke brand, in with the Apple iFhone, Sory TVs and other kwalitee products.

Another amazing site of knockoffs is www.chinavasion.com funny for a browse but wouldn't actually buy there.
ac-dc criggie3 years ago
Certainly knockoff products are easy to find on such sites but the two DX has do look like they are authentic fluke meters, models 15B and 17B, although they are made in Fluke's Chinese factory.

I have a couple of the 17B (bought elsewhere) and while they are not "as" rugged as some Fluke meters, they are leaps and bounds better than the other generic meters DX sells, worthy of their ~ $100 price if ergonomics, durability, and precision matter (they do come with a Fluke certificate of calibration). Here they are on Fluke's China 'site:

http://translate.googleusercontent.com/translate_c?hl=en&rurl=translate.google.com&sl=zh-CN&tl=en&u=http://www.fluke.com.cn/fluke/htmlDocument/category544/index.html
ARJOON criggie3 years ago
thank for the info
i burnt my first meter when i set the dial to mA and tested a christmas light set's amperage. The voltage divider resistors burned out, it literally glowed. It still works now but it's off by 2V when i measure
ccrazed ARJOON3 years ago
You are either buying real crap or you have no clue what you are doing. I have used some cheap rubbish and have never burnt out or blown up any.
ARJOON ccrazed3 years ago
most of the time it was failed experiments
skrubol3 years ago
Just a comment on picking ranges. Pick a range above what you think the highest possible voltage on whatever you're working with, not just the range you think it will be. Some cheaper meters will burn out if you use too low of a range.
Speaking of ranges, autorange is a very handy feature found in higher end meters. Likely not worth it if you don't use the meter often though.
Phil B (author)  skrubol3 years ago
Thank you for both of your comments. I mentioned the auto-range meters, but have not used one. I have a clamp on meter for reading higher amps. and AC voltage. I have put a label on the front of the meter to remind myself to begin at the highest amperage reading. Even then it is easy to forget. That really pegs the needle on that meter. So far I have not ruined it, but.... I do not use a meter real often, but when I need one, I do need it.
skrubol3 years ago
A handy feature on some meters is high-low that can let you do this step by yourself if you've got a way to keep the leads attached to the battery terminals. Connect the leads, press the high-low button, and the meter will keep track of the highest and lowest voltages it sees. In this case the low is what you're interested in.
dataphool3 years ago
Very well done! Although, I notice most of the comments are from people who know, or think they know, what they are doing, electrically.  If your reader forgets any of your advice, they will probably get no worse that a shower of sparks.  And, we have all had a shower of sparks.  Thanks!
Phil B (author)  dataphool3 years ago
Thank you for your comments and for the perspective. I have had a couple of showers of sparks. They bruised my ego, but did not shock my body. Some left burn marks on a screwdriver.
awoodcarver3 years ago
Have used a multimeter for years and found this very helpful ,sometimes we forget the basics and look for a bigger problem ....replaced alternator on my truck a few months ago and then found out that the battery just needed the posts and clamps cleaned ...oh well can always use a extra battery ....nice work !
Phil B (author)  awoodcarver3 years ago
Thank you for looking and for sharing your experience.
Depends on the cord. Our vacuum we have replaced the plug with a very heavy protector at the neck. The larger plug gives something to grip onto instead of yanking the plug out of the wall. Other plastic plugs, or older plugs that may be brittle, I can see removing and replacing the whole thing. Replacement plugs usually have screw threads and a clamp at the neck to make it stronger. No soldering needed but you can solder if you wish. Removing the whole cord you must solder to replace it.
I took a course in basic electricity and my husband gave me my very own very small hand held meter. Its fun to work with once you understand it. Thanks for making this instructables so others will give it a try.
Phil B (author)  NaturalCrafter3 years ago
You are welcome. It is always nice to hear from a woman who likes these things. From what you wrote, I am guessing you have already been working with your meter, and this Instructable only augments what you have already been doing. Thank you for looking at this. I remember that you also looked at and commented on my Instructable about rebuilding a hydraulic floor jack, and that you are one of those who subscribed to me. Thank you.
raygun883 years ago
My tv was "dead" a few years ago and I fixed it with a $3 fuse from Radioshack. Its definitely worth poking around before wasting money and resources on a new appliance.
And think, a fuse that costs you $3 for convenience at Radio Shack probably costs you $1 or less from other distributors. :)
Phil B (author)  NRen2k53 years ago
Radio Shack sells convenience. I am thankful to have a pretty good electronics parts distributor in the town where I live (population 44,000). However, Radio Shack has longer hours for shopping when it is more convenient to me. I do get much more knowledgeable assistance at the electronics distributor, though.
Phil B (author)  raygun883 years ago
Thank you for sharing your experience. Often you are forced to buy a 5-pack of fuses, but it is still a great feeling to resurrect an appliance for very little cash outlay.
TCSC473 years ago
This is a good post with lots of interesting information. Digital multimeters are so cheap nowadays that you can learn how to use them "the hard way" and not worry about the cost of replacing the DVM when you find out something about it, that you should have spotted when you RTFM!

I would like to say, however, that I would not encourage anybody to measure the mains voltage in any way, if they are starting out or even have had only a few years experience. If you need to check the mains supply is at the socket, plug in a bedside lamp or similar.
Phil B (author)  TCSC473 years ago
Yes, the mains are good to avoid. I began as my father's helper in his electrical business. I learned how to work around the mains safely very early. Later there were occasions when it was necessary to work with hot wires. I always try to avoid it, but have done it a few times without so much as a tickle. You may notice I tried to stress there are often ways to do useful tests while there is no power to the circuit. Still, in order to be certain there truly is no power to the circuit, it is often necessary to test an outlet connected to the mains. Once, I wanted to replace one 230 volt outlet with another of a slightly different configuration. I firmly believed I knew which circuit breaker controlled that circuit and knew it was "off." But, I tested the circuit with a tester one last time and was surprised to learn it was controlled by another fuse panel. Had I not tested the mains, I would have met the mains in a most unpleasant way.
TCSC47 Phil B3 years ago
You set out to show why anybody with the slightest interest in DIY or a technical hobby should have a modern cheap digital multimeter in their tool box, and I think you succeeded.

Cheers!

And I don't have any interests in selling these devices. LOL!

Phil B (author)  TCSC473 years ago
The best meter you can buy would be like any other quality tool--to be desired as the better course. Thanks.
TCSC47 Phil B3 years ago
Always a valid point if you know what you are doing, but I think that the great thing about cheap meters is that they are so cheap (as you point out) that you can afford to buy one even if you are not sure what you want to do with it. Once you have it, then you will start to find uses for it. (where your posting comes in handy)

The other thing about cheap meters is that they are simpler than the more expensive ones, and so will be less daunting and easier to get to understand.

My experience of meters ( I have quite a few and have used very expensive professional ones) is that the cheap ones are just as tough as the expensive ones but simply have a few less ranges and specialised functions. Not by much though. eg. an decent electricians meter costing £100 will be able to measure resistances down 1/100 ohm whilst a hobbyists meter for £5 will only be able to measure resistances down to 1/10 ohm. This will be perfectly adequet for almost everything that needs to be done at home.

The only thing I would quibble about is cheap leads. The ones in your picture have probes with tips that are uninsulated for a length of a cm or so. You may end up shorting out what you are measuring, if the long tips touch something they shouldn't.

In the UK there are IET regulations governing the use of probes that restrict the uninsulated probe tip to less than 2mm, (1/8 in) if used for measuring voltages greater than 50V in the work place. However over here almost all electronics meters are sold with probes like the ones you show, so you should go out and spend literally five times the cost of the meter on a set of professional probes! At home, I would just place a bit of decent insulating sleaving stripped from a bit of cable or similar, over the end.
Phil B (author)  TCSC473 years ago
You make good points. My brother gave me a little pocket meter with one probe permanently affixed to the front end. It comes with an insulating sleeve. The other probe is a pigtail coming out the end of the meter. It is not sleeved. I guess we do not have the same regulations in the USA yet that you have in the UK. I have thought I could save some insulation stripped from a piece of #12 or #14 wire and use it as a sleeve. Thanks for your comment.
nwzhnd3 years ago
Thx so much for the excellent instructable. I'm one of the scaredy cats (middle-aged female). This has frustrated me for some time as I've collected a lot of tools over the years that I've used to restore and repair different parts of my house and appliances, but I could never quite get over the electricity fear. I have a multi-meter that I inherited from somewhere, but no instructions and have just kept toting it around hoping to use it "someday". ;)

Right now I have the dryer problem that you've outlined and I now feel I can get up enough nerve to try it out. I've read everyone else's comments and understand that there are lots of things that I'm not going to try, but this one seems do-able.

On a completely unrelated topic but useful info for anyone starting to build up a tool collection, who is daunted by the prices, I would suggest going to auctions. I've picked up whole boxes of tools for 1/10 of the price they would cost in the stores. Come to think of it that's probably where my multi-meter came from too!
Phil B (author)  nwzhnd3 years ago
You are the category of persons for whom I decided to do this Instructable. I hope you enjoyed the photo in the Introduction. ;-) As noted several times, many things can be checked with the power "off." When I am trying to find the circuit breaker that shuts off the power to a circuit that I intend to check, I plug in a radio with the volume turned way up. I can hear when it goes silent, even from the main panel. That saves a lot of running back and forth. Other than that, check codes to know what size and type of wire to use, keep black on black and white on white, be neat with routing wires (Neat is generally safe.), and do not knick anything that could short out later. Check this if you need help with a three-way or four-way switch. Thanks for the great tip on getting good tools cheap. I always waited to buy a tool until I needed it. Then I bought something that was more general than specific, and I usually bought the part of a set I actually needed rather than a whole set I might not use. Let us know how things go with using your meter. Thanks for commenting.
kea3 years ago
The secret in working with electronics is" KEEPING THE SMOKE INSIDE" Ha Ha.
Jokes aside almost everyone needs a multi-meter of some soft.
They can save u alot of money & a lot of time. Mind u I have found in doing a lot of work over the years the MK 1 Eyeball can find faults. Sometimes we miss the obvious.
A Good instructable though as most of them r.
Its great to also share ideas etc.
Cheers KIWI.
Phil B (author)  kea3 years ago
Thank you for your comment. A friend has taken me with him in his airplane. Someone asked me how I like that. I said it is not bad if you keep the horizon level, the blue up and the brown below.
mikeeve3 years ago
Good instructable. I gave my 20-something daughter an inexpensive meters as a stocking stuffer last Christmas. Then she turns to me and says, "What am I supposed to do with this?". So much for the AP Physics she took in high school! I'll send her a link to this. On the other hand, I bought my wife a cheap one so she'd leave my more expensive one alone!

I sometimes find multiple meters handy. At today's prices, it's easy to afford.
Phil B (author)  mikeeve3 years ago
Thank you for your comment. We bought our kids (or their spouses) multi-meters as Christmas gifts, too. It was a good feeling a couple of weeks ago to see one of the kids actually had his out and was using it. I hope your daughter gets some good from this Instructable. It could save her a bundle of money, especially after she begins to live in another city where her dad is no longer a few minutes away. Your story about her reaction, even after the AP Physics course, reminds me of a man who was a navigator on a bomber during WW II. The crew had completed its bombing run and was on the way home. The navigator was sitting back and relaxing. Suddenly a problem developed and the pilot called for their position. The navigator said it was in the next few seconds that he really became a navigator.
I like your 'ible. I got a very cheap meter awhile back, and it didn't come with instructions. That, coupled with my lack of any sort of electronics experience, made your instructable perfect for me, on many levels.. I didn't come to it "afraid" to use one, god knows I've used them perfectly skill-lessly, and thus uselessly, on many occasions, turning dials and poking things hoping it would give me some sort of answer to no avail. I think your post will help to remedy that. I also thoroughly enjoyed the comments throughout, they turned out to be a footnotes of sorts for the lesson, allowing the reader to go deeper into the subject, via Ohms law, or electronics safety, and the philosophical debates as to how much work should be put into something before adding it to the earth's trashheaps. And I'm glad your instructable, continues the pursuit of reparing before replacing, which was my intent when I bought my previously useless multi-meter. thank you.
Phil B (author)  DeliciousMystic3 years ago
The book mentioned in the last step, or one similar to it would be something to think about. There are some pages on the 'Net that give some help with using a meter. For someone making a beginning with a meter, the safe option might be to make as many tests as possible with the power to the system shut off. Use the continuity or the Ohms settings to check for breaks in the electrical pathway. There is a lot you can do that way, as I tried to demonstrate. But, as I mentioned in a recent response to one commentator here, I came very close to working on something I was sure had been isolated from its power source, only to find at the last minute that it was supplied by another fuse panel, and I would have received a good jolt. Now there are testers available that glow when the user simply moves the tip of the probe near to a hot terminal without actually touching the terminal. I have seen these at big box home improvement stores in the USA. Thanks for your comments.
Great instructable! Lots of good info. You may want to add a note about the one-hand rule for working on line voltage AC stuff, particularly the step about the air conditioner fuses. You've got good safety notes in general, but just trying to keep your hands away from the hot terminals in that small box is not enough. With only one hand, even if you slip, at least current won't go directly through your chest.
Phil B (author)  TheOneTrueStickman3 years ago
You make good points. If electricity "must " (because of an accident) pass through one's body, it is best that it passes down one side or the other, and not across the chest where it can bring arrest to the heart. With the insulated alligator clips I showed, it would be easy to clip one lead to a screw on the neutral strip and then use one hand touch the probes to first one hot terminal and then to the other. The user would know there is 120 volts from each hot terminal to ground. It would be highly unusual that the two hot terminals would not make 230 volts, if measured across each other. Also, if checking fuses is the objective, it is easy to do that with the switch lever pulled to the "off" position, and use the CONT to check for an electrical path through each of the fuses. I have checked both hot terminals in that box. I do it very carefully. It is better to hang the meter from something so I can devote all of my attention to the probes. Thanks.
sitearm3 years ago
An electrician's son and assistant, and a rural pastor and fixitman. I love it.

I was going to make a connection between knowing how to use a multimeter to fix electrical circuits, and knowing how to use religion to fix theological circuits, but that's as far as that idea got. :)
Phil B (author)  sitearm3 years ago
Thanks. It is dangerous to be a pastor who knows how to use an electrical meter. People bring you all sorts of extra-curricular stuff needing repair, not to mention things at the church that are limping.
alantihor3 years ago
I agree with Procactus. You should make sure that your meter is rated for what you're measuring. I would even reccommend using a CAT III meter if you were going to use it on anything over 120V. I've working in air conditioning repair for close to 15 years and would never use anything less than CAT III.

Also, you mentioned measuring the amperage of a circuit by connecting the meter in series. Most meters have a very low rating for in-series amperage readings, usually measured in microamps. If you want to measure the amperage safely, I would recommend using a meter with a clamp-on attachment.

Here's a link to a page from Fluke on multimeter safety:

http://www.google.ca/url?sa=t&source=web&cd=1&ved=0CB4QFjAA&url=http%3A%2F%2Fsupport.fluke.com%2Ffind-sales%2Fdownload%2Fasset%2F1263690_6116_eng_h_w.pdf&ei=qnTVTa__MYqTswbQy_GiDA&usg=AFQjCNFZsg0cUQZyL1095xn6kDmtSgcFsA
Phil B (author)  alantihor3 years ago
I also have another meter with a clamp-on attachment for reading amperes. That is beyond the scope of the intended audience and purpose for this Instructable. The meter shown in the photos here can read up to 10 amperes. It does not clamp on, but must be used in series with the rest of the circuit. Many devices in use today draw only a couple of amperes due to low wattage integrated chip circuitry. Thank you for the Fluke link.
criggie3 years ago
Step 2, photo 2 - your leads are the wrong way around, hence the negative reading.
Phil B (author)  criggie3 years ago
I know. The text notes that reversed polarity is not a problem for the tests I described because the numbers are the important part. Remember, this Instructable is for the person who has never owned a multi-meter. They can learn to observe polarity later.
ProCactus3 years ago
A cheap meter may actually kill people here. There are meters designed for mains voltage. I live in Australia the mains voltage commonly known is 240Volts, Though actually is 220v and this is RMS(root mean square).

If you stick two probes in the Active(hot) and the Neutral or even Earth, With the lead that come with a cheap meter, Is bad for you( Its risky ). To be sure you want to get you hands on a meter that is 'Cat II' or better.

IE. Measuring a mains voltage 110-240volts should be a Cat II or better.

Otherwise you tempt a rare death. It simply can happen.


If you want to check a mains outlet safely and cheaply, Get a plug that has lights on it. Simply the order the light show tell you what your mains outlet is doing. In old buildings there is no guarantee that Active and Neutral are the right way around.


,,,,,,,,,,,,,,,,,,,,,,,,,
Ive done things like stick a $10 meter into a 240v mains. But somewhere someone is gunna get hurt by it.
Maybe someone will try this in a blackout in a storm :O

Anyway a 'Cat II' will give you better protection.

Chances are you get one go at making a mistake.
-Good luck :)
Phil B (author)  ProCactus3 years ago
At the church I served before this one we had a very inexpensive analog meter. The leads on the probes felt flimsy. I did use that meter and those probes to check 230 volt AC terminals in the air conditioner fuse box, and did it several times. But, I always held the probes by the plastic handles. The plastic part was better insulated than the flimsy cables.

I did not mention the plug in LED testers with red and green go or no go LEDs, nor did I mention neon test pigtails. But, those are options. Still, it is remarkable how many high voltage AC circuits can be successfully tested with the power "off."
jjmcgaffey3 years ago
Thanks! I have a multimeter - wanted it for one particular project - but have never been sure what else I could do with it. This gives me quite a few ideas. So thanks again!
Phil B (author)  jjmcgaffey3 years ago
I believe you will find a number of uses for your meter once you begin to think about ways to use it. For example, I went for years without a welder. Once I finally had one, I was welding all sorts of things I did not even know needed to be welded before. I think you might also find the book I mentioned in step 18 helpful. I must confess I do not do everything mentioned in the book. I wish I could remember the name of its successor, which was not distributed through Radio Shack (as I remember). Thanks for commenting.
malakesher3 years ago
Just so you know the '9V radio battery' is called as PP3 battery and the '3V camera battery' is a CR123 battery from the looks of it.
Phil B (author)  malakesher3 years ago
I did this Instructable for the person who is frightened by electricity and who is intimidated by technical things. I sought to avoid being any more technical than absolutely necessary. "Radio battery" and "camera battery" probably work better with the intended audience than the very correct numbers.
Sorry I didn't mean to like a no-it-all or anything and most people do say things like radio battery I just thought it would be right to also mention the correct names as well. To be honest I refer to them with names like radio battery usually.
forget your laymans terms and that last comment. simply think 9volt and 1.5volt, And best not touch the mains power.
KellyCraig3 years ago
Keep in mind, a battery will give different readings dependent of if it's under load or not. With no load, it may read full voltage, while simply running a light (e.g., a flash light bulb) across the terminals, then measuring voltage can give a much lower reading, suggesting the battery should be thrown or charged, depending on the type.

Try this simple experiment the next time a battery needs replacement.

Good instructable. My house, car and shop each have meters because I think they're so important.
marcintosh3 years ago
Great info thanks. One of the greatest pieces of advice I've ever gotten is "Start testing the cheapest parts first". They're cheap so they wear out first. Makes sense no?

BTW that reasoning works nearly everywhere from my ancient Blazer Diesel to the Hadron Collider.

Thanks again,
M
Phil B (author)  marcintosh3 years ago
Thank you for commenting and for looking. You make a good point. With electrical things a good first question is always, "Is there power to the circuit?" Our church at the time had an electric drill apparatus for lowering and raising a 7-day candle in a ruby red glass. The women came to change it on a Saturday. It did not respond when they pressed on the toggle switch. They came and got me out of my office. I looked down where it plugged into an outlet at the baseboard and it was unplugged. I plugged it back in and said, "Try it now." I tried not to smile too much. They felt a little silly, but I had tried to let them down easy.
r.effuse3 years ago
If the voltage difference is more than 2 volts between the cable and the battery post, you have a corrosion problem. Auto technicians treat 0.5 volts as acceptable for commercial work. This is true for any 12v circuit in the car and is a great way to test for tricky problems that only act up under load or, say, in bad weather.
Phil B (author)  r.effuse3 years ago
Thank you for the additional information and thank you for looking at this Instructable.
Nice post. I liked the LED tips.
Phil B (author)  alexandrelandim3 years ago
Thanks. I tried to discuss uses for a multi-meter I have found in multiple general and very practical areas around the home and family automobile. Certainly there may be people who will use a meter in specialized areas, like LED projects. This is actually the second multi-meter I purchased. The first also had a high input impedance like this one for possible use on the first computer controlled automobile we owned. Later, I was dabbling more in electronics and wanted one that could test capacitors and transistors. That is when I waited for some gift money and bought this one. (I sold the other to a friend who needed one and gave him a very good price.) In case you or others are unfamiliar with the concept, high input impedance means that the meter is able to sample the circuit without exerting an influence on the circuit that skews the readings in any way. Inexpensive meters may not have a high input impedance, which is fine for the applications I described in this Instructable, but when taking readings at checkpoints on our first computer controlled car, the readings might not have been accurate enough for a proper diagnosis.
cchubb3 years ago
I got so tired of loaning my multimeters out to my neighbors or doing testing for them that I bought ALL of them (5 households on my street) their own DVM and showed them all how to use it. No more "Is my battery good" or "why won't my taillight come on" or "why doesn't my thermostat work".
Phil B (author)  cchubb3 years ago
Thanks for your comment. That is a good solution to the problem of people wanting you to do their work for them. But, it also reminds me of the car I sold to the son of a friend some years ago. When the heater core began to leak he brought it back to me and asked for help replacing it. We spent a cold November afternoon on my driveway working on that. He was young and it was an opportunity to teach him, too.
that was a very usrful instructable Phil, thanks for writing it. Steli
Thank you, Steli.
jeff-o3 years ago
Great idea! Thanks for writing this (though with me, you're preaching to the choir, haha...)
Phil B (author)  jeff-o3 years ago
Thanks. I am hoping to reach some not yet in the choir.
randofo3 years ago
This is a very nice and thorough overview of some common day-to-day uses for a multimeter. I wish I got the chance to feature it myself ;-)
Phil B (author)  randofo3 years ago
Thank you.
rimar20003 years ago
Very good idea doing this instructable, Phil. I always wonder the fear that people have to testers (multimeters). Even very skilled colleagues, do not have one because they do not dare to use it.
Phil B (author)  rimar20003 years ago
Osvaldo,

The first photograph suggests (somewhat humorously) that women should consider carrying a meter in their purses because meters are so handy. Thanks.
well done! this will be super handy. fav'd!
Phil B (author)  justin.jackson3 years ago
Thank you. You may not need to do some of these regularly, but they are a help when you need them.
rimar20003 years ago
I use it mainly to test continuity, and batteries volts and amps. This last measure must be very short to avoid discharge the battery.
mikeasaurus3 years ago
Great info here, Phil.
Phil B (author)  mikeasaurus3 years ago
Thanks, Mike. It comes from a lot of reading in numerous sources and from lots of practical experience over many years.