Use of a multimeter: What is a Digital Multimeter? How to Use a Multimeter

How to Use a Multimeter

By

James Fitzgerald

James Fitzgerald

James Fitzgerald is a home improvement expert and writer with over a decade of hands-on experience in new construction, remodeling, carpentry, painting, plumbing, and landscaping. He has wrangled huge trees as a tree climber and aerial lift operator. James has written for sites Bob Villa Family Handyman and HomeServe and he also owns a handyman service.

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Editorial Process

Updated on 10/11/22

Reviewed by

Larry Campbell

Reviewed by
Larry Campbell

Larry Campbell is an electrical contractor with 36 years of experience in residential and light commercial electrical wiring. He worked as an electronic technician and later as an engineer for the IBM Corp. He is also a member of The Spruce Home Improvement Review Board.

Learn more about The Spruce’s
Review Board

Fact checked by

Sarah Scott

Fact checked by
Sarah Scott

Sarah Scott is a fact-checker and researcher who has worked in the custom home building industry in sales, marketing, and design.

Learn more about The Spruce’s
Editorial Process

The Spruce / Adrienne Legault

Multimeters are invaluable tools for troubleshooting a wide range of electrical components. The possible applications are many, but they’re typically used to test:

• Wall outlets
• Power cords
• Appliances
• Consumer electronics
• Vehicle electrical systems

What Is a Multimeter?

A multimeter is a measurement device used to measure multiple electrical values. Multimeters can measure voltage, current, resistance, and (sometimes) test for continuity.

The multimeter’s impressive versatility is owed to its ability to test for the three basic units of electricity, including:

• Voltage: Multimeters can test two forms of voltage: alternate current (AC) and direct current (DC). AC is the voltage used in your home’s electrical wiring, while DC is used primarily in vehicles, residential solar systems, and consumer electronics. Voltage is measured in volts.
• Resistance: Resistance is the opposition to the flow of current through a circuit, and is measured in Ohms.
• Current: Generally speaking, current is the amount of electricity flowing through the circuit, and is measured in amps. The amount of amps flowing through a circuit is the difference between the voltage applied and the resistance present. Milliamps (1/1,000 of an amp) are the most common unit of amps measured with a multimeter.

In addition to testing those three functions, some multimeters test for continuity, or the absence of resistance within a circuit. Not all multimeters have dedicated continuity functions, but those that do emit an audible beep when continuity is present. If this setting isn’t present, testing the resistance can be used instead.

Finally, there are two different types of multimeters: analog and digital. The main difference between the two is their display. Analog multimeters display their measurements with a needle that moves over a progressed scale. Digital multimeters have an LCD screen that displays the measurements in four or five digits. Another difference is that analog multimeters don’t usually offer a continuity function, though some do.

Parts of a Multimeter

• Display: The window where the electrical measurements are displayed.
• Selection Knob: A round dial that allows you to select the type of electrical unit to measure. You can switch between AC volts (V with a squiggly line on either side or above it), DC volts (DC-), and resistance (Ω), amps (A), and milliamps (mA). Continuity is marked with diode symbol (triangle with a line on the right side) and/or a soundwave symbol on the selection knob.
• Probes: Red and black wires used to physically test the electrical component. Each one is equipped with a pointy metal tip on one end, and a banana plug on the other. The metal tip is used to probe the component being tested, and the banana plug connects to one of the multimeter’s ports. While there’s no actual difference between the two probes, the black cord is often used to test ground and neutral (or common) terminals, and the red wire is usually used for hot terminals. When testing for resistance and continuity, it makes no difference which probe is used where.
• Ports: Most multimeters are equipped with three ports: COM (or “-”), mAVΩ, and 10A. COM stands for common and is what the black probe is usually plugged into. The mAVΩ port is where the red probe plugs into to measure volts, resistance, and current. The 10A port is a specialty port that’s used when measuring currents greater than 200 mA. Some multimeters have four ports that split the functions of the mAVΩ setting in two, with one VΩ setting for volts and resistance and a µAmA setting for current.

Safety Considerations

When using a multimeter to test live electricity, it’s important to take certain safety precautions to avoid any chance of electrocution as accidents can occur. These include:

• Wearing insulated gloves
• Not using a multimeter with any broken or frayed wires on the probes
• Not performing any electrical testing in wet conditions
• Not touching the tips of the probes together while testing

How to Use a Multimeter

1. Measure Volts

   Turn the selection knob to either AC or DC volts, depending on what you’re testing. Place the black probe on the negative terminal of the component you’re testing, and the red probe onto the positive terminal. 

   As an example, let’s assume you’re testing a standard, 3-pronged electrical outlet in a US home. Turn the selection knob to AC volts and ensure the probes are plugged into the appropriate port. Place the black probe into the slot on the top left of the outlet (neutral) and the red probe into the upper right slot (hot). If the measurement doesn’t read around 120-volts, a wiring issue is likely to blame. Another indication of a wiring issue is if you place the black probe into the u-shaped slot on the bottom of the outlet (ground), the red prong into the neutral slot, and the measurement is greater than 0.

   You can also test the outlet’s ground by inserting the black prong into the bottom slot, and the red probe in the hot slot. The measurement should be roughly 120-volts, or else the outlet has a bad ground.

   The Spruce / Adrienne Legault

2. Check Continuity

   If your multimeter has a dedicated continuity setting, turn the selection knob to continuity. Verify the meter and probes are working by touching the tips of the probes together. The meter should beep if it’s working properly. 

   A common use of continuity testing is checking the functionality of a power cord. Start by touching one of the multimeter probes to one of the prongs on the male side of the power cord. Insert the other probe into the corresponding slot on the female end of the cord. The multimeter will make an audible beep if there is continuity. Repeat this process on the remaining male prong and female slot. If there wasn’t a beep on either side, the power cord needs to be replaced.

   Next, touch one of the probes to one of the prongs on the male end of the cord, and the other probe to the other male prong on the same end. If the meter beeps, that indicates a short and the cord needs to be replaced. 

   If your meter doesn’t have a continuity setting, you can test the resistance instead. Turn the selection knob to the Ω setting, and use the same procedure outlined above. The only difference is that you’re looking for a reading between 0 and 1 on the display instead of listening for an audible beep. If the reading is 1 or OL (open loop), the circuit lacks continuity and the cord should be replaced.

   Tip

   Your resistance reading should be very near 0 if you are measuring from male end to female end for each of the lines (hot, neutral, and ground).

   The Spruce / Adrienne Legault

3. Measure Resistance

   Aside from testing continuity, measuring resistance is commonly used when checking an electrical component’s resistors (like in a speaker).  

   If checking a resistor, determine the resistor’s resistance value. This can either be found marked on the resistor itself or in the owner’s manual of the component being tested. Turn the selection knob to the Ω setting and place each of the multimeter’s probes to one of the resistor’s leads. If the resistor is functioning properly, the resistance value on the meter’s display should be the same as the resistor’s rating. If not, the resistor is defective and needs to be replaced.

   The Spruce / Adrienne Legault

4. Measure Amps

   One of the most common reasons to measure amps is for diagnosing vehicle electrical issues. For example, a parasitic draw on the battery.

   What Is a Parasitic Draw?

   Also called a “drain”, a parasitic draw is a term used to describe an electrical component that’s consuming electricity even when the vehicle is shut off. This can lead to low battery voltage, causing a persistently dead battery and vehicle starting issues.

   To diagnose this, disconnect the battery cable from the battery’s negative post (marked “-“, and usually black in color). Plug the red probe into the 10A port of your multimeter, and turn the selection knob to the amp setting. Connect one of the multimeter’s probes to the battery post, and the other probe to the battery cable. The measurement should be between 50 and 60 mA. Anything higher indicates a parasitic draw.

   If a parasitic draw is detected, remove and test the vehicle’s fuses one by one until you achieve the desired reading on the multimeter. The circuit operated by the fuse that was pulled is the source of the issue.

   The Spruce / Adrienne Legault

The Spruce uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

1. Employee Is Electrocuted From Contact With Energized Wires. Occupational Safety and Health Administration, U.S. Department of Labor.

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How to use a multimeter correctly – Lifehacker

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August 25, 2019

They can measure DC and AC voltage, resistance, current and check the circuit.

How a multimeter works

As the name implies, a multimeter is used to measure several electrical quantities. The multifunctional device combines a voltmeter, ammeter, ohmmeter, continuity, and may also have additional functions such as a thermocouple or a low-frequency generator, testing capacitors and transistors.

Analog testers with a scale and an arrow are almost never found, as they have long been supplanted by affordable digital instruments. The latter, in addition to the accuracy and number of modes, differ in the type of determination of quantities. Automatic show the result immediately after selecting the mode, in manual you need to additionally set the measurement range.

All multimeters have a similar design. There is a screen on the front panel, below it there is a rotary mode switch, and just below it there are connectors for connecting probes. Some models have buttons for turning on the backlight, storing readings, and for other additional functions.

Wires with probes that need to touch the workpiece during measurement are connected to the appropriate connectors. The black wire is always to the socket with the designation COM, and the red one, depending on the amount of current. If it does not exceed 200 mA, then to the VΩmA connector, if it exceeds, then to 10ADC (10A MAX). In everyday life, such high currents are not found, so the VΩmA socket is mainly used.

The numbers on the scale indicate the maximum value that can be tested in this range. For example, in DCV 20 mode, a constant voltage is measured from 0 to 20 V. If it is 21 V, then you need to switch one step higher, to position 200. It is important to choose a range in accordance with the measured one, otherwise the multimeter will deteriorate.

How to measure DC voltage with a multimeter

Check that the probes are connected correctly.

electronoff YouTube channel

Switch to constant voltage mode. It is usually denoted by the symbols V with a straight and dashed line, or DCV.

In multimeters with manual range selection, additionally set the approximate measurement value, and preferably one step higher. If you are not sure, start with the maximum and gradually lower.

YouTube channel electronoff

Touch the probes to the contacts and look at the screen. If a minus sign is displayed along with the number, then the polarity is reversed: the red probe touches the minus, and the black probe touches the plus.

electronoff YouTube channel

In a handheld multimeter, you may need to adjust the measuring range.

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If the display is one, you need to increase the measurement limit, if zero, the symbols OL or OVER – lower.

How to measure AC voltage with a multimeter

Check that the probes are connected correctly.

Switch on AC voltage mode. It is marked with the symbols V~ or ACV.

In handheld multimeters, also set the approximate measurement value. Better one step higher or the most maximum.

Hold the probes to the contacts and read the reading from the display.

YouTube channel electronoff

If a multimeter with manual ranges and a unit on the screen, increase the measurement limit, if zero (OL, OVER) – lower it.

How to measure resistance with a multimeter

Check that the probes are connected correctly.

Set resistance measurement mode. It is denoted by the symbol Ω.

If the tester is manual, select the approximate measuring range.

Touch the probes to the resistor terminals and look at the resistance on the screen.

YouTube channel electronoff

On a handheld multimeter, adjust the measuring range up or down as needed.

How to test a diode or circuit with a multimeter

Insert test leads into the correct terminals on the multimeter.

Switch to Diode Continuity Mode, marked with a vertical line arrow symbol.

Attach the probe needles to the diode leads. The multimeter will show the voltage drop on the screen. If you swap the probes, then with a working diode on the screen there will be a unit, and on a faulty one – any other number.

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In the same mode, you can ring a circuit or wire, but you must first de-energize them. If the integrity is not violated, an audible signal will sound, if there is a break, the screen will simply display one, OL or OVER.

YouTube channel electronoff

On some multimeters, the sound mode of the continuity is turned on separately. For example, on a black tester, as in the photo above. This mode is indicated by the volume up symbol, note or speaker.

How to measure current with a multimeter

Connect the test leads to the correct sockets on the multimeter depending on the amount of current.

electronoff YouTube channel

Set current measurement mode (DCA, mA).

In a manual range multimeter, set the maximum threshold.

When connected in series, the multimeter is part of the circuit.

Connect the probes in series in the circuit. Unlike voltage and resistance, current is not measured in parallel. That is, you need not just touch two points of the circuit or the conclusions of the part, but connect the multimeter to the open circuit. If connected in parallel, the device may be damaged!

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The current consumption will be displayed on the screen. If the multimeter is handheld, then you may need to switch the range for more accurate results.

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How to use a multimeter – Basic electronics

If you are wondering “ How to use a multimeter?” “, then at least you already know what electric current and voltage are. If not, then I suggest you read the first chapters of my electronics textbook.

So what is a multimeter?

Multimeter – is a universal multimeter that combines the functions of several measuring instruments, that is, it can measure a whole range of electrical quantities.

The smallest set of multimeter functions is the measurement of voltage, current and resistance. However, modern manufacturers do not stop there, but add to the set of functions, such as measuring the capacitance of capacitors, current frequency, diode continuity (measurement of the voltage drop at the p-n junction), sound probe, temperature measurement, measurement of some parameters of transistors, built-in low-frequency generator and much more. With such a set of functions of a modern multimeter, the question really arises how to use it after all?

In addition, multimeters are digital and analog . We will not delve into the jungle, I will only say that they outwardly differ in instruments for displaying the measured values. In an analog multimeter, it is an arrow, in a digital one, in the form of a seven-segment indicator. However, we are used to understanding the word multimeter as a digital multimeter. Therefore, in this article I will tell you how to use a digital multimeter.

Take the popular 9 series multimeters as an example0113 M-830 or DT-830 . There are several modifications in this series, their marking differs by the last digit, as well as by the set of functions embedded in this device.

I plan to review the multimeters of this line in one of the next issues of the magazine, so do not forget to subscribe to new issues of the magazine at the end of the article. I will describe how to work with a multimeter using the example of device M-831 .

Basic functions of the digital multimeter M-831 and assignment of instrument controls

Consider carefully the external panel of the multimeter. Here we see a seven-segment liquid crystal display in the upper part, on which the values ​​we measure will be displayed.

Further, we can say in the center of the device, there is a switch for values ​​​​and measurement limits.

Let us consider in more detail all the designations that are applied in a circle, thereby analyzing the operating modes of the multimeter.

1 – turn off the multimeter.

2 – AC voltage measurement mode, has two measurement ranges of 200 and 600 volts.

In other models of multimeters, the designation ACV – AC Voltage – (Eng. Alternating Current Voltage ) – alternating current voltage

3 – mode for measuring direct current values ​​in the following ranges: 200 μA, 2000 μA, 20 mA, 200 mA.

Other models of multimeters may use the designation DCA – (eng. Direct Current Amperage ) – direct current.

4 – mode for measuring large values ​​of direct current up to 10 amperes.

5 – sound continuity of wires, the sound signal turns on when the resistance of the called section is less than 50 Ohm.

6 – checking the health of the diodes, shows the voltage drop at the p-n junction of the diode.

7 – resistance measurement mode, has five ranges: 200 Ohm, 2000 Ohm, 20 kOhm, 200 kOhm, 2000 kOhm.

8 – DC voltage measurement mode, has five ranges of 200 mV, 2000 mV, 20 V, 200 V and 600 V.

In other models of multimeters, the designation DCV – DC Voltage – (eng. Direct Current Voltage ) – constant voltage may be used.

There are three sockets in the lower right corner of the front panel of the multimeter for connecting the included test leads.

Everything is simple here:

– lower socket for common (negative) wire in all modes and on all ranges;

– middle socket for positive wire in all modes and on all ranges except current measurement mode up to 10 A;

– upper socket for positive wire in the current measurement mode up to 10 A.

Be careful, when measuring current more than 200 mA, connect the positive wire only to the upper socket!

The multimeter is powered by a 9-volt battery type “Krona” or according to the standard size – 6F22.

Inside, under the rear cover of the multimeter there is a fuse, usually 250 mA, which protects the device in current measurement mode up to 200 mA.

Measuring electrical quantities with a multimeter

So, it’s time to learn how to use a multimeter. We will learn how to measure electrical quantities using the example of the same M-831 multimeter. Let me remind you once again that with this multimeter you can measure direct and alternating voltages up to 600 volts, only direct current values ​​​​up to 10 amperes and electrical (active) resistance values ​​\u200b\u200bup to 2 megaohms.

Let me remind you that to measure the voltage on an element (section) of an electrical circuit, the device is switched on in parallel with this element (or section of the circuit).

To measure the current in a circuit, the device is connected to the break of the measured circuit (that is, in series with the circuit elements).

How to use a multimeter to measure DC voltage.

Now let me tell you in detail, step by step, how to measure DC voltage with our multimeter.

The first thing to do is to select the type of voltage to be measured and the measurement limit. To measure DC voltage, the multimeter has a range of DC voltage values ​​that are set using the limit switch.

To set the measurement limit, first determine approximately what voltage value we want to measure. Here you need to act according to the situation, if you measure the voltage of the batteries (batteries, accumulators), then look for the inscriptions on the elements, if you measure the voltage in various electrical circuits, then I think since you “climbed” there, then you already know how use a multimeter!

Let’s say we need to measure the DC voltage on the battery from some electronic device (I’ll take a video camera battery).

1. We carefully study the inscriptions on the battery, we see that the battery voltage is 7.4 volts.

2. Set the measurement limit greater than this voltage, but preferably close to this value, then the measurements will be more accurate.

For our example, the measurement limit is 20 volts.

Nevertheless, when measuring voltage, for example, in circuits, I advise you to set a limit greater than the supply voltage of the circuit, so as not to cause the device to fail.

3. We connect the multimeter to the battery terminals (or parallel to the area where you measure the voltage).

– black probe one end to the COM socket of the multimeter, the other to the minus of the measured voltage source;

– red probe to the VΩmA socket and to the plus of the measured voltage source.

4. Read the DC voltage value from the LCD display.

Note: if you do not know the approximate value of the measured voltage value, then the measurement must begin with setting the largest limit, that is, for M-831 – 600 volts, and consistently approach the limit closest to the measured voltage value.

How to use a multimeter to measure AC voltage.

AC voltage measurement is made in the same way as DC voltage measurement.

Switch the instrument to AC voltage measurement mode by selecting the appropriate AC voltage measurement limit.

Next, connect the probes to an AC voltage source and take readings from the indicator.

How to use a multimeter to measure DC current.

As a reminder, the 830 series only measures DC current, so if you need to measure current in an AC circuit, look elsewhere.

A multimeter for measuring current is connected to the break of the measured circuit.

Again, it is necessary to determine the maximum possible current in the circuit being measured.

If the current values ​​are less than 200 mA , then select the appropriate measurement limit, connect the red probe to socket VΩmA and turn on the multimeter in the open circuit.

To measure current in the range of 200 mA-10 A , connect the red probe to socket 10A .

It is advisable to connect the multimeter in the current measurement mode to the circuit when the circuit is de-energized, and at the limit of 10A this is a mandatory operation, since at high currents it is not at all safe.

And the last nuance: in the characteristics of devices of some manufacturers it is not recommended to turn on the multimeter to measure the current at the limit of 10 A for more than 15 seconds.

How to use a multimeter to measure resistance.

To measure resistance with a multimeter, the latter must be switched to one of the five resistance measurement limits.

Moreover, the rules for choosing the measurement limit are as follows:

closer to him. Only in this case will you minimize the error in measuring resistance.

2. If you do not know the value of the measured resistance in advance, then you need to set the maximum measurement limit (for M-831 it is 2000 kOhm) and by changing the limits, gradually approach the measured resistance value.

Note: if “1” is displayed on the multimeter screen, then the value of the measured resistance is greater than the set measurement limit, in this case it is necessary to switch the limit towards its increase.