Voltage is a measurement of potential electric energy between two points. You can measure the voltage of household circuitry or various batteries using an analog or digital multimeter.
1Set the multimeter range. Turn the dial to the AC side of the multimeter, then set the potential voltage range to the highest potential voltage you might test.
- AC stands for "alternating current." Outlets in the United States use AC voltage, so you'll need to set the multimeter to measure AC voltage when testing an outlet. This side of the range will usually be labeled with an "AV" or "~V."
- Standard outlet current is between 110 to 120 volts, but some heavy-duty outlets used for dryers, air conditioners, and other large equipment may have voltage between 220 and 240 volts. These outlets should be identifiable by their non-standard outlet plugs, however.
- You should always set the voltage range so that it can measure slightly higher than the expected amount of volts. If you set the range too low, you may end up overloading and damaging the multimeter.
2Connect the probes to the multimeter. Connect the black probe to the "COM" or "-" port and the red probe to the "V," "mAV," or "+" port.
- You'll need to connect the bent banana jack end of each probe to the multimeter. The straight probe tips will be applied to the outlet.
- Some multimeters may have three ports: 10A, COM, and mAV. Always plug the black probe into the COM port. Connect the red probe to mAV for low currents up to 200 mA, but connect it to the 10A port for high currents. For a standard wall outlet, use the low current (mAV) port.
3Carefully insert the probes. Grab both probe tips on the insulated portion beneath the metal pin. Insert the black probe into one of the straight outlet slots, then insert the red probe into the other.
- Only grab the probes by their plastic insulator bases. Do not touch the metal tip during any part of the process.
- After inserting the black probe, slowly release it. It should remain in the outlet without being held in place. If it doesn't, try inserting the black probe into the outlet again.
- As soon as you insert the red probe, the multimeter should give a voltage reading.
4Read the voltage. Read the voltage shown on the multimeter. If using a digital meter, the voltage should show on the display screen. If using an analog meter, you will need to examine the scale and identify the voltage based on where the needle lands.
- In most cases, the scale should read between 108 and 121 volts.
- If the voltage is higher or lower than expected, you may need to call a professional electrician to inspect the circuitry and identify any possible problems.
5Remove the probes. Carefully grip both probes by their insulated bases and pull them straight out of the outlet.
- Work carefully. Do not touch the metal tips with your bare hands and do not allow them to come into contact with one another.
- After removing the probes, turn the multimeter knob down to its lowest range and switch the device off.
1Set the multimeter range. Turn the voltage dial to the DC side of the multimeter. Set the voltage range so that it is a little higher than the expected voltage.
- Most batteries use "DC," or "direct current," voltage. When measuring any battery or any device run by a battery, you'll need to switch the multimeter to this setting. It is usually labeled with a "DC" or "-V."
- The correct range will vary depending on the type of battery being tested. For instance, if you're testing a standard 1.5V alkaline battery, you will need to set the multimeter to a range of 2V DC. Most automotive batteries are 12V batteries, though, so you'll need to set the multimeter to a range just above 12V DC.
- Note that if you set the range too low, you run the risk of overloading the multimeter and damaging the device.
2Connect the probes to the meter. Your multimeter should have a black probe and a red probe. Black is negative and red is positive, so you should plug the black jack into the "COM" or "-" port and the red jack into the "V," "mAV," or "+" port.
- Make sure that you connect the banana jack end of each plug to the multimeter. The straight probe tips on the other end of each wire will by touched to the battery.
- Some multimeters may have more than one port. In these instances, the black plug will always be connected to the COM port, but the red plug may need to be connected to the mAV port for low currents (up to 200 mA) or the 10A port for high currents. When testing most batteries, use the low current mAV port.
3Touch the probes to the battery. Touch the black probe tip to the negative side of the battery, then touch the red probe tip to the positive side of the same battery. Hold the two in place until the multimeter displays a measurement.
- Make sure that you only grab the insulator base of either probe when testing the battery voltage. Do not touch the metal tips.
- The multimeter should display a measurement almost instantly once the two probe tips are in place. If no measurement appears, make sure that both metal tips are placed directly over the correct terminal. Reposition as needed and try again.
4Take the reading. Read the voltage displayed on the multimeter. When using a digital version, the voltage should appear on a digital display screen. If you use an analog meter, however, you'll need to examine the scale and identify the position of the needle as you continue to hold the probes in place.
- Don't be surprised if a new or recently charged battery has a voltage that is higher than it is labeled for. For instance, some 1.5V batteries may actually read between 1.5 and 1.6 volts. The labeled voltage usually signifies the average number of volts you can expect from the battery throughout its lifetime, not necessary the highest amount it is capable of.
- If the voltage reads as "1," it means that the range is too small to measure the battery. Increase the range to a higher setting and try again.
- If the voltage reads as a negative value, you may have the probes connected to the wrong terminals. You will need to try again, touching the probes to the opposite terminals when you do.
5Remove the probes. After you've measured the voltage, simply pull the probe tips away from the battery terminals and set them aside.
- Make sure that you continue to handle only the insulated base of each probe. Avoid touching the metal tips, and avoid letting the metal tips come into contact with each other.
- After setting the probes aside, turn the knob on the multimeter down to its lowest range. You can then switch the device completely off.
- Always work carefully when measuring electrical energy. If you are uncertain about something or nervous about measuring voltage, ask someone with more experience for help.
- Make sure that the multimeter is set to measure voltage before attempting to do so. If the device is set to measure current/amps, it may become damaged when connected to a voltage source.
Things You'll Need
- Multimeter (digital or analog)
Sources and Citations
- ↑ http://www.acmehowto.com/electrical/outletvoltage.php
- ↑ http://www.sciencebuddies.org/science-fair-projects/multimeters-tutorial.shtml
- ↑ http://www.ladyada.net/library/metertut/voltage.html
- ↑ http://www.optimabatteries.com/en-us/experience/power-source/how-do-you-measure-battery-voltage/
- ↑ http://www.electronics-radio.com/articles/test-methods/meters/multimeter-voltage-measurement.php