How to Use a Digital Multimeter

A digital multimeter is an extremely useful tool for quickly measuring voltage, resistance, continuity, and current in a variety of electrical circuits. Once you understand what the various symbols on the dial mean, using a digital multimeter is a breeze. You’ll be testing all kinds of electronics with your digital multimeter in no time!

Method 1 Voltage

1. Connect the COM and V terminals with the test leads. Always connect the black test lead to the terminal labelled “COM” for “Common.” Because you’re testing voltage, always connect the red test lead to the terminal labelled “V” for “Voltage.”

In this configuration, the test leads are used to measure both AC and DC voltage.

2. Adjust the dial to the AC or DC voltage setting. If you’re measuring AC voltage, set the dial to V, or V with a wave sign next to it. To measure DC voltage, change the dial to V, or V with a horizontal line next to it.

AC, or alternating current, voltage is used to measure items such as wall sockets, microwaves, and other home electrical appliances.

DC voltage, also known as direct current voltage, is commonly used to measure batteries. DC voltage is also used in automobiles and many small electronic devices.

3. Set the voltage range to a voltage that is higher than expected. You won’t get an accurate reading if you set the voltage range too low. Examine the numbers on the dial and select the setting that is closest to the expected voltage of what you’re measuring while remaining above it.

For example, if you’re measuring a 12V battery and your multimeter has settings for 2V and 20V, set the dial to 20V.

If you don’t know what voltage you’re measuring, simply set the multimeter to its highest voltage rating.

4. Connect both probes to a load or power source. Place the tip of the black probe, for example, on the negative lead of a battery or the right side of a wall socket. Place the red probe, for example, on the positive end of a battery or the positive side of a wall socket.

If you’re not sure which end is positive and which is negative, put a probe on each end and see what the multimeter says. If it displays a negative number, your positive and negative values are reversed.

Keep your fingers away from the probe tips when placing them near a wall socket to avoid being shocked.

Avoid allowing the probes to come into contact with one another, as this can cause a short circuit and possibly an electrical fire.

Always hold the probes by the coloured handles, which are insulated to protect against shock.

5. The voltage should be displayed on the multimeter’s screen. Once your probes are connected to the positive and negative leads, the multimeter will display a reading indicating the voltage of what you’re testing. Look at the digital screen to find the reading and, if desired, make a note of it.

Looking at your reading will tell you whether the voltage you’re measuring is normal or not. For example, if you measure the wall socket and the multimeter reads 100V, this is less than the average of 120V, indicating that the voltage is low.

When testing the voltage of a new 12V battery, the reading should be close to 12V. If it is less than this or there is no reading at all, the battery is low or dead.

Method 2 Current

1. Connect the test leads to COM and A or mA, then set the dial to Amps. Connect the black plug to the COM port. Put the red plug into amps or milliamps, labelled with A or mA, depending on the amperage of the current you’re measuring. Turn the dial of the multimeter to the Amps setting.

Your multimeter most likely has two amp terminals: one for currents up to 10 amps (10A) and one for currents up to 300 milliamps (mA) (300mA). Place your red plug in the amps terminal if you’re unsure of the amperage range you’re measuring.

If necessary, you can always switch to milliamps for a more precise reading.

Some multimeters have two As, one for alternating current (represented by the wave sign and used for residential power) and one for direct current (used in batteries and wires and represented by a horizontal line with a dotted line under it). For this reading, direct current is the most commonly used.

2. Disconnect one of the wires in a circuit to break it. This enables you to complete the circuit and measure the current using your multimeter as an ammeter. Unplug or otherwise disconnect one wire from the terminals to which it is connected on one side of the circuit, leaving the other wire connected to its terminals.

It makes no difference which side of the circuit you disconnect. The goal is simply to create a space in the circuit for your multimeter to act as an ammeter and tell you how much current is flowing through it.

The term “splicing in the multimeter” refers to connecting the multimeter to the current flowing directly through the wires.

3. Read the current by touching the multimeter’s leads to the free terminals. To splice the wire back into the circuit, connect one probe to each of the terminals from which it was disconnected. Determine the amount of current flowing through the circuit by reading the screen.

It makes no difference which probe is touched to which side of the circuit. In either case, your multimeter will give you a reading.

Splicing your multimeter into different sections of electrical circuits allows you to troubleshoot them. If one section has a lower current reading, it could be due to a faulty wire that is impeding electrical flow.

If you first test amps and get a really low reading, such as 1, switch to milliamps to get a more precise reading.

Method 3 Resistance

1. 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.

  • The Ω sign is likely linked with the V sign, meaning the terminal to measure ohms and voltage is the same.

2. Set the dial to a number on the resistance scale of the multimeter. Look for the symbol on the dial of your multimeter. In this section, turn the dial to a number close to the expected resistance. If you’re not sure what the expected resistance is, set it to the highest number on the scale. You can fine-tune it as you go until you get a precise reading.

In an electrical circuit, resistance is the opposition to the flow of current. Metals have low resistance, whereas non-conductive materials, such as wood, have high resistance.

Set the dial to just above 0 if you’re measuring the resistance of a wire, for example. The expected resistance for various electrical components can be found online or in an owner’s manual.

Depending on the type of multimeter you have, the values on it can range from 200 to 2 million ohms.

3. Read the resistance by placing the probes on the resistor. Touch the probe tips to each end of the resistor. Examine the digital display of the multimeter to see the reading, which indicates the amount of resistance in ohms.

If your multimeter only reads “1,” you may need to increase the value of ohms measured by turning the dial to get a more precise reading.

If necessary, write down the reading and make a note of the correct unit.

Method 4 Continuity

1. Remove the batteries or unplug the device you want to test. You can’t test for continuity if the device is still powered on. Before you proceed, make sure it is unplugged from all power sources.

The continuity option on your multimeter is used to determine whether or not wires are still functional. If you’re not sure if a particular cord or wire still has a good connection, you can test it by measuring its continuity. This is used to test the connection between two points in a circuit.

The presence of a complete path of electrical flow is defined as continuity. A brand new electrical wire, for example, should have complete continuity. If it is frayed or broken, however, it does not have continuity because electricity cannot flow through it.

This is a good way to determine whether or not the cables are internally broken.

2. Insert the probe wires into the multimeter and turn the dial to the continuity setting. Insert the red plug into the terminal labelled V, or with the continuity sign, which resembles a sound wave. Connect the black plug to the COM port. Turn the dial to the image that resembles a sound wave.

A sound wave is represented by a series of increasingly larger “)” symbols.

Instead of displaying a range of numbers, the continuity option only displays one sound wave. To ensure that the dial is pointing directly at the continuity sound wave, turn it until it is.

3. Connect the probes to the component you’re testing. Connect the black probe to one end of the component and the red probe to the other. To ensure that the multimeter works properly, ensure that the probes are both touching the ends at the same time.

To test for continuity, the component does not need to be disconnected from the circuit.

It makes no difference which probe you use on which end of the component.

Wires, switches, fuses, and conductors are examples of components that can be tested for continuity.

To test for continuity, you must be touching two conductive ends. Touch the probes to the bare ends of two wires, for example.

4. Watch for a beep to indicate a strong connection. If the wire is working properly, you should hear a beep as soon as the two probes touch the wire’s ends. If you do not hear a beep, this indicates that there is a short in the wire.

If you have a cut or burned wire, it is possible that you have a short in your wire.

The beep indicates that there is virtually no resistance between the two points.

Method 5 Current

1. Connect the test leads to COM and A or mA, then set the dial to Amps. Connect the black plug to the COM port. Put the red plug into amps or milliamps, labelled with A or mA, depending on the amperage of the current you’re measuring. Turn the dial of the multimeter to the Amps setting.

Your multimeter most likely has two amp terminals: one for currents up to 10 amps (10A) and one for currents up to 300 milliamps (mA) (300mA). Place your red plug in the amps terminal if you’re unsure of the amperage range you’re measuring.

If necessary, you can always switch to milliamps for a more precise reading.

Some multimeters have two As, one for alternating current (represented by the wave sign and used for residential power) and one for direct current (used in batteries and wires and represented by a horizontal line with a dotted line under it). For this reading, direct current is the most commonly used.

2. Disconnect one of the wires in a circuit to break it. This enables you to complete the circuit and measure the current using your multimeter as an ammeter. Unplug or otherwise disconnect one wire from the terminals to which it is connected on one side of the circuit, leaving the other wire connected to its terminals.

It makes no difference which side of the circuit you disconnect. The goal is simply to create a space in the circuit for your multimeter to act as an ammeter and tell you how much current is flowing through it.

The term “splicing in the multimeter” refers to connecting the multimeter to the current flowing directly through the wires.

3. Read the current by touching the multimeter’s leads to the free terminals. To splice the wire back into the circuit, connect one probe to each of the terminals from which it was disconnected. Determine the amount of current flowing through the circuit by reading the screen.

It makes no difference which probe is touched to which side of the circuit. In either case, your multimeter will give you a reading.

Splicing your multimeter into different sections of electrical circuits allows you to troubleshoot them. If one section has a lower current reading, it could be due to a faulty wire that is impeding electrical flow.

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