How to Use a Multimeter to Test Voltage
If you’ve never used a multimeter to test voltage before, you might be staring at all of the different numbers, symbols, and buttons on the device and wondering what exactly you’re supposed to be doing with them. Don’t worry! This post will walk you through the entire process step-by-step, whether you’re using a digital or analog multimeter.
What is a Multimeter?
A multimeter is your go-to tool for checking electrical values on one handy device. Think of it as a digital detective that helps you figure out whether your wires, batteries, or components are working the way they should. In a studio setting, that might mean checking if your kiln controller is getting power, making sure a heating element hasn’t burned out, or testing a switch, outlet, or battery before replacing it.
There are two main types: digital (with a screen) and analog (with a needle). Both work well, but digital multimeters are easier to read and more beginner-friendly. If you're testing power sources or circuits in your studio, you’ll want one nearby.
Parts of a Multimeter
Every multimeter—whether analog or digital—has a few core components you’ll want to get familiar with before diving into any testing. Once you know what each part does, using the tool becomes a lot less intimidating and a lot more useful.
The Display
On digital multimeters, the screen shows your readings. You’ll see numbers for voltage, current, or resistance depending on what you’re measuring. If your reading says “OL” or just a “1” on the left, you’re out of range and need to adjust your settings. Some digital models also include bar graphs to show fluctuations in real time.
The Dial (or Selector Switch)
This is the big rotating knob in the center. It tells the multimeter what to measure—voltage (V), resistance (Ω), or current (A). Most meters separate AC (alternating current) and DC (direct current), so you’ll need to choose the correct type for your project. Kiln controllers, batteries, and other low-voltage devices use DC. Household outlets and studio wiring use AC.
The Ports
Usually, you’ll see three input ports:
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COM (short for “common”)—this is where the black probe goes, every time.
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VΩmA—this port is for the red probe when measuring voltage, resistance, and small currents (usually under 200 mA).
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10A or 20A—this high-current port is for the red probe if you're measuring larger currents. You probably won’t need this for most studio work unless you're testing something like a kiln’s main power input.
Method 1: How to Use a Digital Multimeter
1. Set the multimeter dial to AC or DC mode.
The symbol for direct current (DC) is a V with 3 dots or a dash above it. It can also be labeled as DCV or something similar. An alternating current (AC) setting is often labeled with a V and a squiggly line or initials like ACV. Turn the dial to the type of current you plan on measuring.
- DC is common in batteries and other low-voltage sources of power. AC is used in buildings, electronics, and anything else that requires multiple currents.
2. Select the voltage range if it can be set manually on the dial.
- For example, if you have a 12V battery, test it using the 20V setting. Using any settings beyond that would lead to a less accurate result.
- Most modern multimeters are autorange, meaning they set the proper range once you begin the test.
- If you’re not sure what voltage setting to use, start at the highest one. Work your way back until you get an accurate result. The voltage readout will change to 1 if you go too far.
3. Plug the colored probes into the slots on the multimeter.
- The mAVΩ port is meant for currents rated at 200 milliamps (mA). In most cases, you will end up using this port.
- Use the 10A port to test strong currents greater than 200 mA. If you don’t know the strength of the current you are testing, plug the red probe into the 10A port to avoid damaging the multimeter.
4. Connect the test leads to the circuit you wish to test
- To get accustomed to using a multimeter, test it on a battery. Hold the black probe against the negative terminal and the red probe against the positive one.
- If you’re attempting to test live wires, find the screws pinning the wires in place. Touch the black probe to one screw and the red probe to another.
- Be careful to avoid touching active wires or metal parts, since it could lead to an electrical shock. Also, the multimeter could short-circuit if you bump the metal tips of the probes together.
5. Adjust the multimeter as needed to get an accurate reading
- The multimeter range has to be set to the correct maximum voltage for the circuit in order to get the most accurate result possible. If it is set too high, it will have a hard time detecting the voltage of a weaker current.
- If the multimeter displays a negative number, for example, the probes are most likely in the wrong place. Reverse them so that the electrical current flows properly between them.
- If you don’t see any readout, the circuit may not be receiving any electrical power at all. Test the multimeter on something active, such as a battery or outlet, to make sure it still works.
Method 2: How to Use a Multimeter
1. Change the multimeter to test an AC or DC current.
Turn the dial to the proper setting. The AC setting is often indicated by a straight line or a label live ACV. The DC option usually as a series of dots or a label like DCV. The setting you need will depend on what you are testing.
- Use the AC setting to test wall outlets and most electronic devices. DC is for batteries and other low-voltage power sources.
2. Select a high range on the dial for the test.
- For instance, most home outlets maintain a 120-volt current. Set the multimeter to 200v or the next closest setting above 120.
- Most multimeters have fuses that protect them from serious damage, although inexpensive ones sometimes don’t. Using the wrong setting could destroy the multimeter.
- If you’re unsure what setting to use, start at the highest one and move down until the multimeter reacts.
3. Plug the probes into the ports on the multimeter.
- If you reverse the probes, you won't get an accurate test result. If you notice the multimeter needle moving in the wrong direction, check the probes first.
4. Touch the ends of the probes to the device you are testing
- You can test the multimeter using a battery first. The positive and negative terminals on the battery are labeled and easy to spot.
- Handle the probes one at a time to avoid touching the tips and short-circuiting the device.
5. Check the meter and adjust it to get an accurate reading
- If the needle doesn’t move much, turn the multimeter’s voltage setting down a little bit. It often doesn’t react when the voltage setting is too high. Also, make sure the testing device is active.
- If the needle moves all the way to the right, pull the probes out. Set the multimeter dial to a higher range, then perform the test again. Try to avoid having this happen, since it could damage the multimeter.
6. Unplug the multimeter probes when you’re done
Pull the red probe out first, followed by the black probe. Handle them carefully so the metal tips don’t come into contact with one another. When you’re done, you can also detach them from the multimeter.Analog multimeters have a needle that moves to measure voltage. Watch for the needle to move toward the voltage numbers printed on the multimeter. Analog multimeters also have separate rows of numbers labeled for AC and DC settings, so make sure you’re looking at the correct one. Note the measurement, then consider doing the test a couple more times to ensure you got an accurate reading.
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