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Electrical Basics: How to Use a Digital Multimeter

Electrical Basics: How to Use a Digital Multimeter

Here at Mortonsonthemove we take on a lot of electrical projects and recommend the use of a multimeter for many of them. If you want to take on some basic electrical repairs yourself you’ll need to know how to use a digital multimeter.

This handy tool can help you measure voltage, current, and resistance, making it perfect for fixing many electrical problems. It’s also an inexpensive addition to any do-it-yourself tool kit.

Not sure how to use one? No problem! We’ll show you how it works. Keep reading to learn more.

How to Use a Multimeter for Beginners - How to Measure Voltage, Resistance, Continuity and Amps

What Is a Digital Multimeter? 

A digital multimeter is a versatile tool you can use to measure various electrical properties. It typically consists of a digital display, a set of probes, and a selection of dials or switches.

Digital multimeters are an essential tool for anyone doing electrical work, as they provide a quick and straightforward way to take accurate measurements.

What Can Digital Multimeters Read? 

The most basic function of a digital multimeter is to measure voltage. However, many people use it to measure current and resistance as well. Voltage, measured in volts, is the pressure it takes to push electrons through wires. Current, which you measure in amps, is how much electricity is flowing through a circuit. You measure resistance in ohms, and It represents a force hindering the flow of electricity.

Though a digital multimeter can measure amperage, we don’t recommend it for beginners unless the meter has a clamp. If the meter does not have a clamp, to measure amps, you’d have to shut down power and break the circuit then insert the meter to take a measurement.

Some multimeters have an amp clamp (or current clamp) to make measuring amps much easier and safer. We would recommend beginners only measure amps with an amp clamp.

Pro Tip: Overwhelmed by the electrical system in your RV? Don’t stress! We put together a guide on Helpful RV Electrical Basics for Beginners.

Electrician using a digital multimeter
You don’t need to be an electrician to do some easy electrical DIYs. Just make sure you have the right tools on hand.

How Do You Use a Digital Multimeter for Beginners? 

A digital multimeter is a valuable tool you can use for multiple tasks. However, it’s crucial to understand how to use a multimeter and its different functions properly. Misusing the multimeter can damage the components you are trying to test. It could even be dangerous.

Choose Your Measurement

First, decide what you want to measure and make your selection on the multimeter. When measuring voltage, you’ll choose between measuring alternating current (AC) or direct current (DC).

Most multimeters have a setting with V~ (a V followed by a tilde or squiggly line) for AC voltage. To measure DC, the multimeter should have a different setting with a V⎓ (a V followed by a solid line over three dots).

AC is the current powering electrical outlets, like the wall outlets where you’d plug in an appliance. DC is the current from a battery, like a car or deep-cycle battery.

If you need to measure resistance, you will be measuring ohms. This measures the difficulty of an electrical current passing through a conductor. A Ω symbol denotes resistance mode.

In addition to resistance, most meters can do a simple conductance measurement. This setting usually will cause the meter to beep when it detects a completed circuit. This is a very helpful setting for determining if a wire is broken or where it goes.

Close up of digital multimeter being used
If you see a little music note or sound projection symbol this is the continuity setting. If you touch the probes together the meter will beep.

Put Leads Into Proper Socket in Multimeter

For voltage and resistance, the leads plug into the same sockets of the multimeter. The black negative lead plugs into the COM port. The red positive lead plugs into the port labeled VΩ.

If you are measuring amperage, there is typically a different selection and setup. We don’t recommend doing this unless your unit has a clamp. In the case of using the clamp, there is no additional setup needed.

Measuring Voltage

When measuring voltage, select the correct current setting for AC (V~) or DC (V⎓).

To check AC voltage, like in a wall outlet, put the negative lead in the more prominent slot on the left and the positive lead in the smaller slot on the right of the outlet. This should return a reading of around 120 volts on the multimeter’s digital screen. 

When checking DC voltage, like on a car battery, touch the negative lead to the negative (-) post on the battery and touch the positive lead to the positive (+) post on the battery. It should read between 12.2 and 13.2 volts on the multimeter if the battery has a full charge.

This measurement can quickly tell you if your circuit is live at the location you are testing and is one of the simplest and most common checks.

Multimeter on red background
Before you begin your electrical project, make sure you know how to use a multimeter.

Measuring Resistance

Be sure to select the ohms symbol Ω when measuring resistance. The leads should plug into the COM (negative/black lead) and VΩ (positive/red lead) ports, like when measuring voltage.

Some multimeters, especially older ones, will require selecting a range of resistance. The decimal point in the readout will move as you change the selection, indicating a higher range. 

Newer digital multimeters have advanced, accurate auto-ranging, making readings more straightforward and more accurate.

The most significant drawback of a manual range selection isn’t that it is less accurate. It comes down to the user’s knowledge. You need to understand your target range to get a precise reading. Most auto-ranging multimeters adjust on the fly to produce an accurate reading.

When measuring resistance, it is best to remove the testing component from the electrical circuit. This negates the chance that another element in the system might affect the reading.

A quick touch of the leads to each other should produce a reading of 0 or no resistance. Next, touch the leads to the component to complete the circuit. This will then give a reading of the resistance in ohms. 

Resistance measurements can tell you if a circuit is not connected, or grounding out. It can also tell you if a component has failed if you have an idea of what its correct resistance should read. Note that resistance may vary wildly when reading into a complicated electronics circuit as capacitors and inductors will react to the meter’s measurement.

Measuring Current

When measuring current in amps, select the amperage setting on the dial. This is at the mA/A position for measuring milliamps and amps. The µA position is for measuring microamps and amperages below 300 milliamps.

Clamp the unit around only one wire at a time and read the screen. The screen should display the amperage of the circuit for the wire.

If you are using a digital multimeter without a current clamp, it is even more essential to understand how to use a multimeter. Select the amp setting on the settings dial, ensure you’ve plugged the black lead into the COM port, and plug the red lead into the amps port (marked by an A).

To get an amperage reading, you need to break the circuit you intend to measure. Measure the amps of the circuit by inserting the multimeter leads into the circuit to complete it. The current flows through the multimeter, providing a reading.

If you are unsure of this process, do not attempt it. Also, never try to read voltage with the leads in the amperage position or set the dial to amperage. It will shorten the multimeter. 

Pro Tip: In addition to a digital multimeter Here Are 21 Electrical Tools Every RVer Needs.

Measuring Current With A Multimeter
Measuring current with an amp clamp is super easy. However, without it the circuit would need to break and we don’t recommend it.

Additional Multimeter Recommendations

It’s crucial to understand how to use a digital multimeter before using its different functions. We have a few recommendations for using your multimeter to increase your safety and protect the multimeter and the devices you measure from damage.

Always Wear Insulated Gloves

You should always wear rubber or dry leather insulating gloves when using a multimeter. Rubber is a poor conductor of electricity, so rubber-insulating gloves help protect the user from shock. 

Dry leather gloves are helpful for up to about 120 volts but not beyond that. Higher voltages increase the risk of fire and shock beyond leather’s protection. Also, note that we are talking about dry leather gloves. Wet gloves or gloves with cracks or holes will allow the electricity to flow to your body. 

Never Test On Voltages or Currents Beyond Meter Rating

Never, ever use a multimeter to test electricity beyond its rating. If a digital multimeter is rated for ten amps but not 20, do not try to push it beyond ten amps. The same goes for voltages. Stay within the multimeter’s limits. 

Using a digital multimeter beyond its ratings can not only damage the device but can also cause bodily harm or even death.

Multimeter limiations
Your multimeter should say what it is rated for clearly. Do not exceed these ratings

Always Test Meter On Knows Circuit First 

When determining if voltage is present, first ensure the meter is working. Do this by testing it on a known circuit, like a car battery or a wall outlet.

This is critical. If you don’t test the multimeter and find that it is not working but go ahead and check for voltage, there is a potential shock hazard. Again, this can damage the multimeter, but more crucially, it could injure you.

Man holding electrical tool
Don’t use a multimeter with your bare hands. Make sure to use rubber or old dry leather gloves.

Can a Multimeter Damage a Circuit?

Yes, a multimeter can damage a circuit. However, this is usually due to an operator error. 

You can accidentally short something by forcing a hot wire to connect to the wrong conductive object. This can quickly happen if you set up the probes to read amps but try to measure voltage.

Always double-check your settings before taking a reading. Also, always ensure that the fuses of your multimeter are in good condition.

Basic Uses of a Multimeter for RVers

Is a Digital Multimeter Worth Having in Your Tool Box?

Yes! No tool kit is complete without a multimeter. Even if you do not use it often, a handyman or someone else helping you out might ask for it. Even a simple inexpensive model can help you understand whats going on so much quicker.

You can use it to measure voltage, amps, and ohms. You can also use it to test for continuity and find shorts in circuits.

If you are doing any work with electricity, a digital multimeter is worth having in your toolbox.

What electrical DIY projects are you planning?  Tell us in the comments!

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About Mortons on the Move

Tom & Caitlin Morton of Mortons on the Move gave up the stationary life for one where they are constantly on the move. They are full-time travelers, television hosts, and digital media producers.
They left their jobs, sold their house and possessions, and hit the road in September 2015 in their full-time “home on wheels”. Since then they have traveled the US, Canada, and even internationally by RV.
Now, they are Discovery Channel & PBS TV Co-stars of The RVers, producers of “Go North” on Amazon Prime, co-founders and instructors of RV Masterclass, and contributing authors for Hwy.co and an Arizona travel guide.

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