A multimeter is a handheld instrument used to check a variety of electrical information. You would use a multimeter to check whether a fixture uses AC or DC voltage, whether it contained a live current, the status of resistance and continuity in electrical components, and more. It also measures ohms, volts, and amps. A multimeter is one of the most useful tools in the arsenal of anyone working on their home’s electrical.
Before we go any further, we want to remind you: there’s no shame in calling a professional, especially when it comes to your home’s electrical. Safety is the highest priority for any homeowner taking on a new project. Don’t take on any work you aren’t 100% comfortable with.
With that said, let’s learn how to safely use a multimeter.
Understand what it helps accomplish.
We’ve explained the basics of what a multimeter does. Before we go any further, we want you to understand the types of questions your multimeter can help you answer. A multimeter can help you determine if a switch is on, whether a wire is broken, or how much power is left in a battery. This information is useful to anyone checking for problems or planning future electrical work.
How do I use a multimeter?
Get to know its components.
Before you use it, you’ll have to know what its different parts are. On a multimeter, you have four main sections: the display, the selection knob, the ports, and the probes.
- The display is the main screen where your measurements will be displayed.
- The selection knob is large, central knob directly below the screen. You’ll turn the selection knob to tell the device what you want to measure.
- The ports are typically lined up along the bottom of the multimeter. They are where you plug in the probes.
- Probes are separate from the multimeter itself. With the average unit, you’ll receive two: one red probe and one blue probe. There is no working difference between these two; The colors are just to tell them apart. Some guides may refer to them as test leads.
How do I measure resistance?
1. Turn on your meter and set the selector knob to Ohms or Resistance.
The Ohm scale is typically the top-most one found on the dial. Look at the meter indication. Right now the meter should have its needle at the left-most point on the meter. This means there is an infinite amount of resistance, otherwise known as an “open circuit.” You want to create an open circuit before you measure.
2. Connect the probes to the ports.
Connect the black probe to the jack marked “Com.” Connect the red probe to the jack marked with the Omega symbol or letter R. Hold the probes together to test that the multimeter is working properly. When they touch, the needle should go from all the way to the left to all the way to the right. There is an adjustment knob just below and to the right of the main screen, called the “Zero Adjust” knob. When they’re touching, rotate this knob until you move the needle to the zero.
3. Measure the resistance of a device or fixture.
A good example of a fixture you could test with a multimeter is a light bulb. All you have to do to test resistance is touch each of the probes to the individual electrical contact points on the bulb. On a light bulb, you’ll find these points on the threaded base’s side and at the center of the bottom. Watch the needle on the meter move. Write down your reading.
4. A few things to remember.
Don’t let the probes touch anything other than the fixture you’re measuring or your reading could be inaccurate. You’ll know if your device has burned out if it doesn’t move the needle all the way to the left when you start measuring. If your multimeter seems to malfunction, try changing its batteries.
How do I measure voltage?
1. Set the meter to the highest range available for AC volts.
Since you don’t know which voltage you’re testing, set your multimeter to handle as high a voltage as possible.
2. Connect the probes to the device.
Put the black probe in the “Com” jack and the red one in the “V” or plus sign jack. Determine which voltage scale you want to want to read. Use the selector knob to do this. This will help you more easily read the voltage you’re measuring. You can narrow down as you go, starting with a larger scale and working your way down to get a more accurate reading.
3. Test voltage.
A commonly-tested item for a voltage reading is an electrical outlet. Common US outlets use between 120 and 240 volts. To read the outlet, put the black probe into one of the two straight slots. Place the red probe into the other slot. Read the reading on the multimeter. You’ll be able to see the needle move to the representative number. This reading can tell you if an outlet is working to its full potential.
There are many other things a multimeter can do. They’re a complex device with a wide range of capabilities. If you want to know more about multimeters or you need help with an electrical problem, call Mike Diamond right away. We’re ready to solve your problems and help you learn!