A digital multimeter is a super handy tool for measuring things like voltage, resistance, continuity, and current in various electrical circuits. However, it can be a bit daunting to use one at first because of all the different settings! Once you get the hang of it, though, using a digital multimeter is super easy and safe. We’ve put together answers to some of the most common questions people have about using their multimeters to measure electricity.
[Edit]Steps
[Edit]What do the settings on a multimeter mean?
- The voltage setting is for measuring AC and DC voltage. AC, or alternating current, voltage is used to measure things you might find around the house, like wall sockets, microwaves, or pumps. DC, or direct current, voltage is mostly used to measure batteries.[1]
- Both of these types of voltage are measured very similarly with only slight differences in how to get your reading.
- The resistance setting is for measuring resistors after disconnecting them. To measure resistance, the multimeter sends a small amount of current to the object you’re testing and gives you its resistance in ohms. Make sure you disconnect the thing you’re measuring so it’s not linked to a power source.[2]
- If you don’t turn off the power, you could damage your multimeter.
- Resistors are passive two-terminal electrical components used to limit the amount of current in certain parts of circuits. You can find them in all types of electrical circuits. They usually look like little cylindrical or oblong shapes with wires coming out of each end and have colorful stripes around their bodies.
- The continuity option is for testing whether wires are still working or not. If you’re not sure whether a certain cord or wire still has a good connection, you can test this by measuring its continuity. This tests the connection between two points in a circuit.[3]
- Continuity is the presence of a complete path of electrical flow. For example, a brand new electrical wire should have full continuity. However, if it is frayed or broken, it doesn’t have continuity because the electricity cannot flow through it.
- This is a good way to see if cables are broken internally or not.
- The amps setting is for finding the current of electrical circuits. Amps, short for ampere, is the unit of electrical current. This measurement tells you how much electricity is flowing through a given electrical circuit.[4]
- For example, measure the amperage of something to determine whether that object is pulling too much energy and draining your electricity.
- An electrical circuit is any path for transmitting electricity. For instance, the wall sockets in your home are electrical circuits.
[Edit]How do you check voltage with a multimeter?
- Plug the test leads into the COM and V terminals. Always plug the black test lead into the terminal that’s labeled “COM” for “Common.” Always plug the red test lead into the terminal labeled “V” for “Voltage,” since this is what you’re testing.[5]
- Both AC and DC voltage are measured using the test leads in this setting.
- Move the dial to V~ if you’re measuring AC voltage. Use the AC voltage setting if you’re measuring voltage in a wall socket, a washer or dryer, a TV, or any other home electrical system. Look for the V with a wave sign next to it and move your dial to this area.
- Switch the dial to V⎓ to measure DC voltage. DC voltage measures batteries. DC voltage is represented by a V with a horizontal line next to it and a dotted line under the horizontal one. Look for the DC voltage sign on your multimeter and move the dial to this section.
- Set the multimeter’s voltage range to its highest. That way, if you accidentally measure AC voltage on the DC setting, or vice versa, it doesn’t harm the multimeter.
- Place the probes on the positive and negative leads to measure voltage. Put the tip of the black probe on the negative lead of a battery or in the negative side of a wall socket. Put the red probe on the positive end of a battery or in the positive side of a wall socket.[6]
- If you’re not sure which end is positive and which is negative, try putting a probe on each end and seeing what the multimeter says. If it’s showing a negative number, your positive and negative are switched.
- To avoid getting shocked, keep your fingers away from the tips of the probes when you’re putting them near a wall socket.
- Keep the probes from coming into contact with one another or you can generate a short circuit and possibly cause an electrical fire.
- Look at the digital multimeter reading to see the voltage. Once your probes are connected to the positive and negative leads, you’ll get a reading on the multimeter telling you the voltage of what you’re testing. Look at the digital screen to find the reading and take note of it if desired.[7]
- Looking at your reading tells you whether or not the voltage you're measuring is average or not. For example, if you measure the wall socket and the multimeter reads 100V, this is below the average of 120V, letting you know this wall socket's voltage is low.
- If you’re checking the voltage of a new 12V battery, the reading should be right around 12V. If it is lower or there is no reading at all, the battery is low or dead.
[Edit]How do you measure resistance with a multimeter?
- Insert the black test lead in COM and the red test lead in the Ω terminal. Stick the black test lead’s plug into the COM terminal. The red test lead’s plug goes into the terminal labeled Ω, which is the symbol for ohms, the unit that resistance is measured in.[8]
- The Ω sign is likely linked with the V sign, meaning the terminal to measure ohms and voltage is the same.
- Set the dial to a number on the multimeter’s resistance scale. Look for the Ω symbol on your multimeter’s dial area. Twist the dial to a number close to the expected resistance in this section. If you aren’t sure what the expected resistance is, set it to a number at the top of the scale. You can adjust it as you measure until you get a precise reading.[9]
- Resistance is the opposition to flow of current in an electrical circuit. Conductive materials like metal have low resistance, while non-conductive materials like wood have high resistance.
- For example, if you’re measuring the resistance of a wire, set the dial to just above 0. You can look up the expected resistance for different electrical components online or in an owner’s manual.
- The Ω values on your multimeter can range from 200 to 2 million ohms, depending on the specific type of multimeter you have.
- Place the probes on the resistor to test the amount of resistance. Touch the tips of the probes onto each end of the resistor. Look at the multimeter’s digital screen to see the reading, which tells you the amount of resistance in ohms.[10]
- If your multimeter is just reading “1,” you might need to increase the value of ohms measured by turning the dial so your reading is more specific.
- Write down the reading if needed, noting the correct unit.
[Edit]How do you check continuity with a multimeter?
- Plug the probe wires into the multimeter and set the dial to continuity. Put the red plug into the terminal labeled as V, Ω, or with the sign for continuity, which looks like a sound wave. Insert the black plug into the COM terminal. Turn the dial to the picture that looks like a sound wave.[11]
- A sound wave looks like a series of increasingly larger “)” symbols.
- Unplug or remove the batteries from the device you want to test. If the device is still being powered, you can’t test for continuity.
- Instead of having a range of numbers in its area, the continuity option only shows one sound wave. Twist the dial until it’s pointing directly at the continuity sound wave to be sure it’s on the right setting.
- Connect the probes to the ends of the component you’re testing. Place the black probe on one end of the component and the red probe on the other. Make sure that the probes are both touching the ends at the same time so the multimeter works properly.[12]
- The component doesn’t have to be disconnected from a circuit to test for continuity.
- It doesn’t matter which probe you put on which end of the component.
- Examples of components you can test the continuity of are wires, switches, fuses, and conductors.
- You have to be touching two conductive ends to test for continuity. For example, two bare ends of a wire.
- Listen for a beep to signal that there’s a strong connection. As soon as the two probes are touching the wire's ends, you should hear a beep if the wire is working well. If you don’t hear a beep, this means you have a short in the wire.[13]
- If you have a cut or burnt wire, your wire might have a short.
- The beep is telling you that there’s almost no resistance between the two points.
[Edit]How do you calculate current with a multimeter?
- Plug in the test leads and turn the dial to the correct Amps setting. Insert the black plug into the COM terminal. Put the red plug into amps or milliamps, labeled with A or mA, depending on the amperage of what you’re measuring current of. Locate the Amps setting and turn the multimeter's dial to it.[14]
- Your multimeter likely has two terminals for amps: one for currents up to 10 amps (10A) and one that measures up to roughly 300 milliamps (300mA). If you’re not sure of the range of amperage you’re measuring, place your red plug in the amps terminal.
- You can always switch to milliamps for a more precise reading if necessary.
- Some multimeters have two As, one for alternating current (used for residential power and represented by the wave sign) and one for direct current (used in batteries and wires and represented by a horizontal line with a dotted line under it). Direct current is the one that's most used for this reading.
- Cut the wire you’re testing using a wire cutter. This is called breaking the circuit, and it turns your multimeter into an ammeter, which measures current. Use wire cutters to cut the wire you’re testing in half. If your wire has insulation on it, strip off roughly of insulation towards the end of each cut using the wire cutters.[15]
- If you don’t break the circuit by splicing the wires, you could blow a fuse and won’t get an accurate reading.
- Keep in mind that this means you have to splice the wires back together after you test the current.
- In some instances, you can avoid cutting the wire by disconnecting one wire and touching the ammeter to the bare wire end as well as the pole of the circuit.
- Splice in the multimeter to give you an accurate reading. Hold one probe to one split end of the wire, and the other probe to the other split end. Use alligator clips to hold the probes and wires together so your hands are free. Read the number on the multimeter to tell you the amps or milliamps.[16]
- "Splicing in the multimeter" means that you're connecting the multimeter to the current going directly through the wires.
- Use a current measurement to troubleshoot the electrical flow in circuits. For instance, if the flow is low in just one section of a circuit, there might be a wire with bad continuity or a component with too much resistance in that part of the circuit.
- Write this number down so you don’t forget it, if desired.
[Edit]Warnings
- Always hold a multimeter’s probes by the colored grips, which are insulated to protect you from shock.
- Don’t let the probes touch when they’re both in contact with their respective parts of a circuit or you can cause a short circuit and generate sparks.
- Never use a damaged multimeter that has cracked probe handles or frayed wires or you can get shocked.
[Edit]Video
[Edit]References
[Edit]Quick Summary
- ↑ https://circuitdigest.com/article/how-to-use-a-digital-multimeter
- ↑ https://www.youtube.com/watch?v=SLkPtmnglOI#t=5m10s
- ↑ https://circuitdigest.com/article/how-to-use-a-digital-multimeter
- ↑ https://www.allaboutcircuits.com/textbook/experiments/chpt-2/ammeter-usage/
- ↑ https://randomnerdtutorials.com/how-to-use-a-multimeter/
- ↑ https://randomnerdtutorials.com/how-to-use-a-multimeter/
- ↑ https://www.allaboutcircuits.com/textbook/direct-current/chpt-3/safe-meter-usage/
- ↑ https://randomnerdtutorials.com/how-to-use-a-multimeter/
- ↑ https://www.youtube.com/watch?v=TdUK6RPdIrA#t=4m18s
- ↑ https://electrical-engineering-portal.com/measuring-resistance-voltage-current-digital-multimeter
- ↑ https://circuitdigest.com/article/how-to-use-a-digital-multimeter
- ↑ https://startingelectronics.org/beginners/first-steps-in-using-a-multimeter/part-3/
- ↑ https://startingelectronics.org/beginners/first-steps-in-using-a-multimeter/part-3/
- ↑ https://www.allaboutcircuits.com/textbook/direct-current/chpt-3/safe-meter-usage/
- ↑ https://www.youtube.com/watch?v=SLkPtmnglOI#t=6m38s
- ↑ https://www.youtube.com/watch?v=SLkPtmnglOI#t=6m39s
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