Save expense of electrician service calls with a digital multimeter

Dear Tim: I’m about to buy a digital multimeter to troubleshoot all sorts of electrical issues around my home. I’ll be blunt. Do you own one? If so, which one? What do you like about the one you have? There seems to be a huge difference in these devices, and I’m very confused as to what to purchase. Why is there such a huge disparity in the pricing of these tools? – Randy P., Akron, Ohio

Dear Randy: I understand your confusion when looking at these tools. If you visit an online retailer that displays different multimeters next to one another, they look pretty much alike, but the difference in price from the lowest to the highest can vary by a factor of 25 or more.

It’s natural for you to wonder if there can be a correspondingly huge difference in performance from tool to tool. The answer is yes. When it comes to digital multimeters, you get what you pay for.

Over the years I’ve accumulated quite a few digital multimeters. I started off with a beginner’s model from Radio Shack. It’s smaller than a deck of playing cards and has somewhat limited capabilities.

I could go on and on about the detailed electrical specifications of multimeters, but I’ll keep it simple: Get one that’s durable, that has a pedigree and that can handle any electrical appliance at your home. The more expensive multimeters can do more.

The one I’m now using is a sleek Klein Tools MM700. As you might expect, it’s robust and has a full feature set that would impress professional electricians, HVAC technicians and anyone who tinkers with electronic devices. What I really like about this one is that it’s an auto-ranging multimeter. This means it will automatically detect what you want to measure without you having to guess the approximate value. I strongly recommend an auto-ranging multimeter for homeowners like you.

Perhaps the most useful thing you’ll do with your new digital multimeter is to check what we call continuity – i.e., if a wire or circuit is continuous or unbroken. Here’s a simple example of this. When I take a quarter or a piece of metal, turn on the multimeter, insert the two probes into the proper holes on the tool and touch the quarter with the probes, I hear a nice tone and I see a measurement on the screen. This tells me electricity is flowing through the quarter or metal between the two probes.

If I had performed the same test but substituted a piece of wire that had a break in it, I would have not heard a thing and my meter would have displayed “OL.” The audible tone in many multimeters is very handy because you can concentrate on what the probes are touching and get the information you need with your ears in some cases.

I’ll describe a few things you can do around your home with an auto-ranging multimeter that could save you the cost of a service call from an electrician. But first things first: When you get your multimeter, stop and read the instructions, especially the safety warnings.

Let’s say you have an old-fashioned low-voltage doorbell and it’s not working. You can use the multimeter to see if you’re getting power up to the doorbell switch. If you don’t register power coming to the switch, then you can use the multimeter to check for a break in the wire from the transformer or up to the doorbell.

Often people mess up the wires that connect to a 3-way switch. They go nuts trying to figure out what wire connects to what screws on the odd switch. Once again, the multimeter will save you an expensive service call. You can use it to discover the continuous hot wire that feeds the first switch. Once you know this, it’s pretty easy to get both switches wired the right way.

Here’s a simple task many overlook. You can use a multimeter to check to see if light bulbs are burned out. Realize the small glob of solder at the base of a bulb is connected to one end of the filament. The other end of the filament is connected to the aluminum threads at the base of the bulb. Turn on the multimeter, touch one probe to the solder glob and one to the threads and check for continuity. If the bulb is still good, you’ll hear a tone if you have my multimeter!

The most common use you may put the multimeter to is to check for live voltage at a switch or an outlet. Follow the instructions that come with the multimeter and avoid working with live circuits. You can turn off the circuit breaker that provides power to an outlet and then check to see if it is energized. I can do this easily with my MM700, as it has removable shields so the probes can get into the slots of a standard wall outlet. If you’re unsure how to do this, consult with a pro.

Let’s say you think a wall switch or dimmer switch is broken. The multimeter can tell you in a jiffy it still works. Disconnect the switch from the power source and use the continuity tester function. If the switch is in the on position and you don’t hear an audible signal or readout for continuity, then the switch is probably defective.

If you like working on your cars, a multimeter is invaluable. The alternator on my son’s car went bad, and in minutes I used my multimeter to confirm the alternator was not producing the needed power to keep the battery topped off.

One thing I love about my Klein Tools MM700 is it also can test the surface temperature of something. It has a really wide range – from zero to 1,500 degrees! There are countless things around your home you may want to know the temperature of, and most would fall within that range.

I also love how durable my MM700 is. It can handle drops from just over 6 feet and sustain no damage. Remember, read the instruction manual that comes with your new digital multimeter.

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