Using a VOM (multimeter) - The Very Basics

CNET has published a short article on the uses of a VOM (multimeter)  around the house or RV.  It covers just 5 common uses but explains in really simple terms - and photos - how to use the meter.  A good place to start if you've never owned a VOM or are clueless about what it is used for.

https://www.cnet.com/pictures/put-your-multimeter-to-work-at-home/

Gary RV_Wizard said:

CNET has published a short article on the uses of a VOM (multimeter)  around the house or RV.  It covers just 5 common uses but explains in really simple terms - and photos - how to use the meter.  A good place to start if you've never owned a VOM or are clueless about what it is used for.

https://www.cnet.com/pictures/put-your-multimeter-to-work-at-home/

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Good heads up Gary.  I have no less than 5 or 6 of that red meter.  It is the model Harbor Freight gives away free with any purchase if you have the coupon.  Works great - 1 in RV, 1 in House, 1 -in shop, 3 spares.

Bill

The only one I disagree with is how to check a switch for voltage being present, #4. You have to verify that your meter is working properly before making that measurement or you might get a false reading and come to the wrong conclusion about voltage getting to the switch or not.
Always, double check that the meter is working by measuring for voltage on something that is known to be working correctly. Sometimes it's just as simple as placing the meter leads into a known good 110V outlet. Verifying the meter is working correctly can go a long ways to ensure good troubleshooting results.

^Agree^ A 100 years ago or so when I first started messing with electricity and using meters, another piece of advice I was given was that there is no reason to take any kind of reading with a meter without knowing what the reading should be, or at least knowing what to be looking for. IE: testing an outlet and knowing 120 VAC is what is expected, and not looking for 12 VDC.

A "Best practice" when using a multi-meter for checking voltages is.....
1.  Make sure your meter is set for the correct voltage type. AC or DC.
2.  Make sure it's set for the proper range of expected voltage if that is an option on your meter.
3.  Check a known source of live voltage to make sure the meter is working properly.
4.  Check the device/wire/whatever that you need to check, and record your reading(s)
5.  Check the meter again on a known live voltage source.

Years ago, I was checking some 480VAC to see if the circuit was dead that I was going to do some repairs on.  I didn't check the meter first on a known voltage source.  So after taking a voltage check and getting zero voltage on the circuit, I was sure it was de-energized.  My workin buddy asked me if I minded whether he could check it also (he was going to, whether I agreed or not).  When he checked it, there was 480VAC present on the circuit.  The bottom line.....
1.  Always check your meter before AND after using it.
2.  He may have saved me from severe shock and/or serious burns...or death.

I was a new Electrician at the time and had never really considered a possibility of equipment failure.  One of the leads coming out of my meter had a broken wire and was not detectable by just looking at it....it looked perfectly fine.  It taught me a lesson I've kept for 37 years as a Journeyman Electrician.  ALWAYS verify absence of voltage when working with electrical circuits....AND verify that your method of testing is failproof.

xrated said:

Years ago, I was checking some 480VAC to see if the circuit was dead that I was going to do some repairs on.  I didn't check the meter first on a known voltage source.  So after taking a voltage check and getting zero voltage on the circuit, I was sure it was de-energized.  My workin buddy asked me if I minded whether he could check it also (he was going to, whether I agreed or not).  When he checked it, there was 480VAC present on the circuit.  The bottom line.....
1.  Always check your meter before AND after using it.
2.  He may have saved me from severe shock and/or serious burns...or death.

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Yeah, when I was working on high powered transmitters my co-workers always kidded me about how long I took to verify the power was off and all components were discharged to ground before reaching inside the transmitter.

The ribbing stopped the day my shorting stick found the second 480 volt feed someone forgot to turn off.

[Sigh] I'm already sorry I even mentioned this beginner article. Electrical experts rarely realize how little a newbie knows and the simplistic level of info needed to get started.

Well. Gary,
I for one am glad you posted that link. I was an electrician and electronic engineer so I know very well how to use a meter. BUT, hardly a week goes by that I don't see a post on here by someone who cleary has no idea of what a meter does. Yet folks on here tell them to go buy one. I think you should put that link in a sticky.

thanks Gary----have used my meter many times on 1.5v and 12v batts but after I bought my travel trailer I find I have to use it a little more than that.

Gary RV_Wizard said:

[Sigh] I'm already sorry I even mentioned this beginner article. Electrical experts rarely realize how little a newbie knows and the simplistic level of info needed to get started.

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The link you posted was right on time for me. I have very little experience with volt meters and that article was a great help.

Thanks

Gary RV_Wizard said:

[Sigh] I'm already sorry I even mentioned this beginner article. Electrical experts rarely realize how little a newbie knows and the simplistic level of info needed to get started.

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Gary, don't be sorry.  Information is power and the more a person knows about something, electricity in this example, the higher the chances are they can do something safely.  We all do the same thing with or RVs.  Some of us are rookies, some are "Journeyman" RVers, and us rookies (I'm naming myself here) depend on info provided by the Journeyman to help us along.  It's all good as long as the rookies realize that they have limited knowledge and proceed with caution....our realize that they need to call in a professional.

P.S.  As a former Instructor in the Electrical Apprenticeship program where I worked, I dealt with people everyday that was starting out at ground zero, with very limited knowledge about their chosen career path.  It's very rewarding to be able to help others learn....and your post/link was just one of the ways that we can help others who aren't knowledgeable about electricity......Thank You!

Lou Schneider said:

Yeah, when I was working on high powered transmitters my co-workers always kidded me about how long I took to verify the power was off and all components were discharged to ground before reaching inside the transmitter.

The ribbing stopped the day my shorting stick found the second 480 volt feed someone forgot to turn off.

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Good lesson, thanks for sharing.  In my line of work, there's no room for error with voltages of 2300, 4160, and 13.8Kv.  You have to get it right EVERY TIME.

My previous remark was inappropriate. The article is intended for those who are not experts and geared to their level, so not surprising that those who already have electrical skills would nitpick at it.

I never thought your remark was inappropriate. The article you linked is a very good resource for beginners. Some of us just thought we may be able to help others along with what you posted. I for one, didn't mean to knock what you posted, and I don't think the others that chimed in did either.

It's obvious from following several threads that there are members trying to use a meter but have no clue how to interpret the readings.
Any help those folks can get is a plus in my book.

I sent the link to my son. Recently I had to lead him through troubleshooting an electrical issue in his car (via telephone).
Sometimes it's easy to forget how foreign basic concepts are to those who haven't been exposed to them.

Thanks Gary for sharing the link.

Tom

Thank you Gary for this information.  For those like me who know nothing about it, this is helpful.

Over the years, we've talked multiple times about the need for a basic article on the use of a multimeter but, for one reason or another, we didn't create one. Maybe it was because it was considered too elementary by those of us who had used one for a living, or were otherwise proficient in using one. Maybe it was because we we were concerned about trying to make the article applicable to various types/models of multimeter.

For whatever reason, it didn't get done. Personally, I'm somewhat embarrassed that I didn't take the time to write/illustrate such an article. I'm glad to see that someone made a start on the subject, for numerous reasons, including educating folks who have no clue, helping prevent someone misusing a multimeter and possibly hurting themselves, encouraging folks who might otherwise be afraid to use one.

I didn't perceive any of the prior replies as nitpicking or otherwise criticizing the article or mention of it.

I bought my very first multimeter 2 months ago when I bought our very first coach.
Great timing Gary and thanks!

Thanks Gary,You can't overstate the importance of having an multimeter and knowing how to use it.    My slides and levelers had stopped working in a campground in Biloxi, MS.  For 2 days I checked and rechecked every fuse and connection on the system.  I had been on the phone with Lippert tech  over and over. I finally bought a multimeter and found a ground wire that was not making a connection. It took less than 15 min to find the problem. 

Just one addition I would like to add to the article.  Not all VOM "beep" when testing continuity.  Many lower end VOM's while they still work well, will register continuity when you touch the probes together. The display will read 0.0.  If the battery in the VOM is low or weak, the continuity reading may not register causing you to believe that the circuit is bad or failing.  (This happened to me with a $10 hardware store VOM).  Also as a previous poster noted a probe may have a bad wire also leading you to believe that the circuit is bad. Low end testers also have low end probes, so be careful.