How to Use a Multimeter or Voltmeter – Most Common Tasks

Testing voltages follows a simple process. For those new to electrical testing, we asked our resident experts how they teach apprentices how to use a multimeter or voltmeter. Once you know how to use a multimeter, you can move on to troubleshooting and fixing electrical problems, verifying power to outlets, checking continuity, and more.

First, a multimeter (voltmeter) is often used as an analog device. Every professional uses a multimeter for troubleshooting, but even homeowners sometimes benefit from using this tool.

You can get a basic multimeter for less than $20, and they're readily available. In this article, we assume you will be using a multimeter.

Analog and Digital Multimeters

The difference between analog and digital multimeters comes down to displays and what they measure. Analog multimeters measure voltage (volts), resistance (ohms), and current (amps). A dial on the display (which looks like a VU meter) responds to the magnetic field generated by the change in current that the device detects.

A digital multimeter (DMM) gives you a digital readout, but also offers other functions. For example, a digital multimeter includes internal electronics including converters, comparators, encoders, and logic controllers. Because the results are digital, a DMM has the potential to be more accurate and precise when taking measurements. This extra precision is associated with higher resolution provided by advanced digital components, error correction and processing.

Learn how to use the multimeter dial settings

Almost every multimeter uses a large dial to set the mode. It might seem intimidating – but we can help you learn everything you need to know. No matter which brand you use, there are a few key functions on each dial. You just need to know where to look, and you can easily find the pattern you want.

Multimeter with manual range setting

Some multimeters, divide each measurement area on the dial into sections with specific dial points for different scales.

On multimeters with manual range settings, set the dial above the maximum expected voltage. Many of these measurement tools have options labeled for various voltages. This changes the sensitivity of the meter, allowing you to take measurements without damaging the tool. If the tool does not display a range setting, your voltmeter may be using autorange.

If your meter doesn't have autoranging, don't worry, just set it to a higher voltage than you expect. For example, if you plan to test approximately 120V wall outlets (in the US), set the meter to 200V~. If you don't know what to expect, set the voltage on the meter to the maximum setting.

Just for your own information, household batteries typically run at 9V DC or less, while fully charged car batteries run at up to 12.6V DC. The alternator typically charges the vehicle's 12V battery at about 14V.

Multimeters with autoranging or pushbuttons

Other multimeters just direct you to the general measurement type and let the "range" button control the scale. Some even set the scale automatically. "Scale" refers to measuring the difference between volts (V), millivolts (mV), or microvolts (µV).

Editor's Note: When testing power tool batteries, the voltmeter will show that the 18V and 20V Max packs output the exact same voltage .

Browse through each main watch face setting

Let's walk through each of the main watch face settings so you can understand what the symbols and names mean. This should help you get into the correct mode so you can use the multimeter properly.

Measuring voltage with a tester

• V~ (AC voltage)
  Use the "V~" AC voltage setting to measure or test AC (alternating current) voltage. AC voltage is the voltage of any outlet or plug in your home that powers your refrigerator, computer, TV, and more. It should be around 120Vac. AC voltage is represented by V followed by a tilde (~). The reason is that alternating current reverses direction periodically.
• V—(DC voltage)
  The "V—" DC voltage setting allows you to measure DC (direct current) voltage. You can measure and troubleshoot batteries and portable electronics using DC current. The reason is that most home electronics take 120V AC wall voltage and immediately convert it to DC before powering sensitive internal processors, screens, and other systems. When measuring the voltage of a vehicle battery, you will also find DC current.

Author's Note: Sometimes manufacturers combine AC and DC voltages into one dial setting or position. When they do, you usually need to press the "Mode" button to toggle between AC and DC voltage modes. The LCD screen should give you an indication by toggling between the visible V~ and V— patterns.

How to Measure Ohmic Resistance and Continuity Using a Multimeter

• Ω (resistance)
  You set the multimeter dial to Ω to measure resistance. This is handy for continuity testing (although many multimeters have a dedicated mode for beeping). You can also measure resistance during many electronics troubleshooting steps on a circuit board. Electricians can also use a multimeter to test ground resistance when sinking ground rods for electrical panels.
• Continuity <br>The continuity symbol looks like a plus arrow pointing to the right (see above). You might also see a "speaker" symbol or something that indicates you'll hear a tone or beep. Use continuity to resolve potential breaks in the line. Connect each multimeter lead to
• both ends of the circuit. The beeping means you have a "closed" circuit, so the part of the wire or cable you can't see is somehow connected in a loop.

Measure current (amps) with a multimeter

• A (current, ampere)
  You measure current (amps) to troubleshoot various electrical systems. Measuring current can tell you things like how much power a particular circuit draws—all other things being kept in line. A multimeter measures current only by "breaking" a circuit. It has to be queued. If you want to measure current draw without disconnecting the circuit, you'll need a clamp meter and a separate "hot" wire – like you might find in a circuit breaker panel.

Measure current (amps) with a multimeter

• Temperature and Advanced Features <br>Depending on which DMM you have, there may be additional features and options for measuring temperature (using special probes). This is beyond the scope of this article, but these features can further aid in troubleshooting.

Note that DMMs and voltmeters are not the same as non-contact voltage testers (NCV). The latter will only light up and/or beep when you're near a live circuit. More advanced NCVs tell you the type of voltage detected (low voltage, high voltage, etc.) by dividing the LED into voltage ranges.

Plug in the multimeter test leads

Your multimeter contains at least two test leads, one red and one black. Each has a probe on one end and a plastic-covered metal jack on the other. The latter plug into the appropriate colored slots on the multimeter.

The black jack will always plug into the port labeled "COM" (Common). When measuring voltage, the red jack will plug into the hole labeled "VΩmA" or something similar. Typically, you'll find several "red" ports that differentiate between voltage (V) and current (A, mA, or µA).

Also, be aware of the maximum voltage (AC and DC) supported by your meter or tester. Typical ranges include 750VAC and 1000VDC. You'll also want to make sure you have a CAT II or better meter.

Since you can only measure current (amps) online, you need to be aware of the maximum capacity when using a DMM or voltmeter in this way. For example, many models only support up to 800mA. If you set the meter to measure current and hold it to more than the maximum amount, you could pop the integrated fuse – and possibly damage the tool.

Needless to say, this is also very dangerous!

Measuring voltage

Safety first

Safety is key when learning how to use a voltage tester. When dealing with electricity, it doesn't take a lot to stop the heart. When touching live circuits, keep fingers away from metal probes. Also, when using on a live circuit, prevent the probes from touching each other.

Also, as mentioned above, make sure your probe is properly inserted into the meter. This means using the high voltage port to measure the 120VAC circuits in your home. It also requires you to set the scope (if applicable) to high pressure mode (see above).

Insert the metal probe into the hot socket

Basically, you can test the voltage in a circuit by connecting wires in parallel. Starting with the previous example of testing a wall outlet, insert the black (negative) test lead into the larger vertical slot of the outlet. Most black probes have a retaining tab on them so you can insert them and let them go.

Next, you'll get to the red wire from the positive hole. This will be the smaller vertical hole on the 120V 15A receptacle. Check the reading on the gauge. You should get a reading of about 120V. However, if you get an overload reading ("OL" or "1"), you need to increase the range on your multimeter.

How to Test a Battery with a Multimeter

The process is also very simple. On the battery, you'll need to set your multimeter to read DC voltage (V–). Connect the black test lead of the voltage tester or multimeter to the negative pole, and the red test lead to the positive pole. If there is no reading on the meter, check the meter for a switch labeled DC+ or DC-. If so, switch places. If not, swap the positions of the red and black probes.

Still haven't read it? Lower the voltage setting by one step until you do.

Measured Current (Amps)

You'll notice that there are as many as two points on the multimeter for measuring current (amps). There are two main things to know when measuring current.

1. You always measure the current in series with the load; this means the current flows through your meter
2. You need to set the multimeter to the correct settings, including plugging the probes into the correct ports

Take care to follow the instructions for the maximum amount of current the meter can handle. If you don't, or connect to the wrong port, you could blow the internal fuse or even burn the meter.

How Most People Fry Their Multimeters

Most of the time when people destroy their multimeters they are measuring no load current. That means they set the meter for amps, insert the red probe into the spot marked 10A…then quickly insert the probe tip into an outlet or in parallel with the high current circuit.

That will burn out your meter – or at best the internal fuse. You just applied a 0 ohm load to the high current supply. Always measure the current in series with the load. This means you connect the meter in series with the hot leg.

Voltage is a "potential" measurement. This is available. Current doesn't actually exist until you create a load for it. What you never want to do is create a zero resistive load (your meter).

Pay attention to your meter, what you're measuring, and how your probes are connected, and you'll do just fine.

Multimeters and Voltmeters

Multimeters include the same functions as voltmeters, but can also test for current, resistance, and continuity. Sometimes, with the right probes and sensors, a multimeter can also capture other information, such as temperature.

Back to the voltmeter or voltmeter, it measures the difference in potential between two nodes of a circuit. Admittedly, this sounds rather complicated and technical. However, it only takes a few steps to master. Knowing how to use a multimeter works the same as using a voltage tester.

in conclusion

Clear as mud? OK If you don't recall anything, it's that you usually only measure the voltage directly across the outlet. With the right equipment, you can safely test any electrical circuit around your house or car. What are your best practices? Give our apprentices some tips on how to use a voltmeter below!