Dear Dave,
What is the best multimeter to have in our tool box? If not by brand name, what functions are mandatory to have, good to have, and would be a nice extra to have? —Dr. Mike
Dear Dr. Mike,
There is a tremendous variety of multimeters available ranging from cheap Harbor Freight models all the way up to the $300-$400 Fluke. The best one for you depends on your level of electrical diagnostic ability. The cheap models will have most of the functions for the average RVer to diagnose 12-volt power at the battery or a 12-volt charge from a converter/inverter. This will also provide testing for 12-volt power at an appliance such as the refrigerator, water pump, and others.
It will also have a setting to test 120-volt power at the campground pedestal with the probes on the 15-amp, 30-amp, and 50-amp outlet. This setting will confirm proper voltage, which should be at least 115 volts and not more than 125 volts, as well as proper wiring. This can be done by testing following the diagram below. Note: The reading between ground and neutral on both 30 and 50 amp should be zero. Insert the red probe in the Hot and the black in the Ground, red in the Neutral and black in the Ground. When checking between Hot and Neutral, you can use either probe. You will get either a + reading or, if the probes are switched, you will get a – voltage reading.
This same setting can provide testing at the rig for outlets and direct wiring such as the roof air conditioner.
The continuity setting at the lower right can be used to verify an open or closed circuit and testing 12-volt plug in style fuses. Note: Always conduct nondestructive tests, which means no power.
More advanced technical diagnostics
For the advanced technician, you can test ohm resistance as well as DC amp draw. For more information on these and other tests/functions of more advanced technical diagnostics visit electricity expert Mike Sokol’s articles on RVtravel.com.
There are more expensive multimeters such as NAPA, Klein, Southwire, and others that will probably last longer and give a more finite reading in some of the more technical diagnostic issues. However, I have used this model for quite some time and it seems to work fine. Everyone has their own personal model, so I’ll open it up for discussion.
Tools to have in addition to a multimeter
Besides a good multimeter, I would suggest a couple other tools such as a non-contact voltage tester that will do a quick verification of 120-volt power at an appliance or even a cord.
I would also suggest getting a GFCI tester. This one from Klein also shows the voltage.
Read more from Dave here.
Dave Solberg worked at Winnebago for 15 years developing the dealer training program, as marketing manager, and conducting shows. As the owner of Passport Media Creations, Dave has developed several RV dealer training programs, the RV Safety Training program for The Recreation Vehicle Safety and Education Foundation, and the accredited RV Driving Safety program being conducted at rallies and shows around the country. Dave is a leading expert in the RV industry and author of the “RV Handbook” as well as the Managing Editor of the RV Repair Club.
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I am a former electronics tech. While I do have fairly expensive DVM at home, Fluke. I also have an older Sencore analog VOM that I use a lot. Most of the time you are just trying to measure for a certain voltage or check resistance and not worry about precise accuracy down to two decimal points. Sometimes that accuracy can be misleading.
I carry the Harbor Freight meter in my TT. While it may not be as accurate as my Fluke, it does the job. And if it fails, it’s cheap to replace.
I like this Southwire outfit for most things around an RV.
https://www.amazon.com/Southwire-10037K-Electrical-Manual-Ranging-Non-Contact/dp/B07H9WNZP3/ref=asc_df_B07H9WNZP3/?tag=hyprod-20&linkCode=df0&hvadid=309803885710&hvpos=&hvnetw=g&hvrand=570241041426476370&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9051761&hvtargid=pla-628174894979&psc=1
The first photo shows a red meter with the words continuity written over it . It is set on 20 volts DC..most likely not going to let the smoke out, but come on.
If set for continuity and volt age applied you’d be looking to buy a new meter.
Just a note: Changed the continuity photo
Dave S
That’s the one that I use. When Harbor Freight puts them on sale for $5.00 I’ll buy two or three and put them in a handy location so I don’t have to go looking for one whenever I need it. I have found this unit to be very durable, for the price, and accuracy is good enough for what I do.
After volts, my most used feature is a beeping continuity tester. Measuring ohms is a distant third. As a separate useful gadget is an AC/DC clamp on Ammmeter.
I’m looking for a digital multimeter that announces voltage measurements. It’s often hard to see the display and the probes at the same time.
“When checking between Hot and Neutral, you can use either probe. You will get either a + reading or, if the probes are switched, you will get a – voltage reading.” Tell me: do you get a – AC reading very often?
As a retired Master auto technician I have a Fluke and a upscale Bluepoint (Snap-on) as well as a dual trace scope. When milli-volts, milli-amps and accurate ohm readings are necessary, I had to go with the best that I could afford. Now I’m glad to have them in my camper just in case.