How to Use a Multimeter to Test Voltage (Plus Safety Tips)

Man checking a refrigerator with a digital multimeter

Whether you’re an electrician or a handy homeowner, multimeters are excellent tools to keep on hand. However, they can be difficult to use unless you’ve had some training and know what you’re doing. In this article, we’ll look at how to test for both AC and DC voltage using a multimeter. Even more importantly, we’ll learn how to do it safely to eliminate any risk of electrical shock. Let’s get started!  

How to Test AC Voltage  

If you’re using your multimeter around the house, the odds are that you’re using it to test AC voltage, as that’s a multimeters most common use. It’s important to note that whether you’re wondering how to use a digital multimeter or a manual one, the methods are the same. The only difference is that with a digital multimeter you push buttons and with a manual one you turn a knob. Here’s how to start testing.  

  • Take your multimeter out of its protective case and turn it on. Make sure to turn the mode switch to AC voltage.  

  • Turn the voltage setting so that it’s as high or higher than the voltage of the appliance you’re testing. To be safe, you can turn it all the way up to the highest setting.  

  • Plug the black probe of the multimeter into the slot marked common or COM.  

  • Plug the red probe into the other slot, usually marked with a V. It might also be marked with a V followed by various symbols.  

  • Place the end of the black probe against one side of what you’re measuring and the end of the red probe on the opposite side.  

  • Make sure that there is power running to whatever you’re trying to measure. Otherwise, you won’t get a reliable reading.  

  • Remove the red and black probes from their slots and turn off your multimeter.  

There you have it, how to test AC voltage using a multimeter. It’s not overly complicated, but it’s important that you follow the above steps in addition to the safety tips listed below. It’s also a good idea to know what the voltage should be for whatever component you’re testing. That way you know if your reading is high or low, which could indicate a potential problem. You can use this method to test anything from a light switch to a circuit breaker to an outlet.  

How to Test DC Voltage  

DC voltage is mostly used in cars, batteries, and car batteries and here’s what you need to know when using a multimeter with DC voltage.  

  • Connect your red and black probes following the same steps listed above for AC voltage.  

  • Turn the mode switch of the multimeter to DC rather than to AC.  

  • Turn the voltage selector knob or button to the highest voltage setting of 30 volts. You can keep it there or work your way down until you get close to the actual voltage of whatever you’re testing.  

  • Touch the black probe to the negative terminal or side of the battery you’re testing.  

  • Touch the red probe to the positive terminal or side of the battery you’re testing. 

  • Remove the red and black probes from their slots and turn off your multimeter.  

It’s best practice to remove the red probe first, then the black one, but either order will do.  

Safety Tips  

Now that you know how to use a multimeter to check both DC and AC voltage, let’s look at some safety tips to always keep in mind.  

  • Do not touch the lead tips as this could result in shock to you 

  • Do not touch the tips to each other 

  • Do not touch a tip to a metal surface 

  • Do not insert the test leads into the incorrect jacks 

  • Never test an AC main – leave this to the professionals 

  • Always wear safety googles, gloves, long sleeves 

  • Ensure that breaker box is easily and quickly accessible  

  • Turn off breaker switch for most electrical work 

  • Ensure area is well-let and free of obstructions 

Working with electricity of any sort is dangerous and should only be done when following the above safety protocols.  

Next Up: How to Test an Outlet With a Multimeter  

Now that you know how to use a multimeter and you understand the importance of safety, you’re ready to put your skills to the test. One of the easiest and most applicable ways to start is to test an outlet with a multimeter. Outlets in houses operate with AC voltage so make sure that’s where your multimeter mode is turned to. From there, follow the steps from start to finish and visit this link from Mr. Electric for more information. If you need help testing or solving other electrical problems, call your local pros at Mr. Electric. We have helped thousands of homeowner's solve electrical issues, including upgrades and professional installation that guarantees the job gets done right the first time. To learn more give us a call at, (844) 866-1367 or visit us online to schedule an appointment