This article will cover the very basics of using a multimeter safely – there is no way a short article like this one could ever cover every single situation but I am confident that I can guide you some key concepts to get you on your way!

Quick anatomy of your multimeter

1. Red test lead
2. Black test lead
3. Function / range dial
4. Function button / second function
5. LCD / screen
6. Volt/Ohm/diode test red jack
7. Common / black jack
8. 10A range red current jack
9. 400mA range red current jack

Where to connect your test leads

You will notice that there may be up to four terminals on your multimeter where you can plug in your test leads. The good news is that the vast majority of the time, you only need 2 of them!

• The black lead goes into the black jack typically labelled “COM“
• The red lead, the vast majority of the time will go into the red jack labelled with “VΩ” and typically a myriad of other labels

WARNING!

Putting the red (or black) lead in the jack labelled either “A” or “mA μA” without knowing how to use these positions can lead to blown fuses, equipment damage or at the limit, personal harm. Please be careful!

Multimeter Functions

Your multimeter can do more than one thing, hence the word multi. In fact, some multimeters have so many functions that a lot of the functionality goes unused in a hobbyist’s hands. My recommendation is to learn the functions in this article and learn the rest as they come up. Don’t worry, you’ve got this!

Multimeter Function: Continuity

What does it do?

As one of the core functionalities of a multimeter, the continuity mode allows you to check that a conductor or a series of conductors are complete and unbroken. It will give you audible and visual feedback when a conductor or a series of conductors is complete from one end to the other and display “OL” or “1.” when there is no connection – which can be just as useful.

Some concrete examples of what you would use the continuity function for:

• To check if two wires you have soldered together are making a good electrical connection
• To check if one part of a circuit board is connected to another
• To ensure that a section of a circuit that is supposed to receive power is not connected to (shorted to) a part of a circuit that is grounded.
  • This can be vital to ensure that a piece of unknown equipment is not broken or will not destroy itself when powered on the first time. See this example here.

How to use it

Unfortunately certain manufacturers put the function behind a secondary selector within the Ohm/resistance range. Just look for the logo that looks like a sideways wifi logo.

1. Put the black lead into the black COM jack
2. Put the red lead into the red jack with either the continuity (sideways wifi logo) or the Ohm (Ω) logo – they should both be on the same red jack – with other symbols on it too!
3. Turn the dial / select the range with the continuity logo
   • Remember that you may have to press a “FUNC” or “2ND” button to switch to continuity vs the plain old “Ohm Ω” range. Make sure the logo shown on the screen looks like a sideways wifi logo
4. Next, ensure that your device under test is disconnected from any power source. TESTING A DEVICE WHILE POWER IS APPLIED CAN RESULT IN DAMAGE TO YOUR MULTIMETER.
5. Touch one side of your device (which can be a piece of wire, a trace on a circuit board, a pin on a connector etc…) with one of your two probes (doesn’t matter which one!) and touch the second probe to wherever you want to check for a connection.
   • Take note of what the display looks like before you touched any component – if there is no connection between the two probes, the screen will remain the same, meaning no current can flow between those two parts of the circuit

Practice exercises

1. On a piece of paper or in a text document, explain to the best of your abilities what continuity means.
2. Set your multimeter to continuity mode and touch one of your probes to the other probe. What happens? Now touch one of your probes to the handle of the other probe. What does your screen show? What does that mean?
3. Find a length of wire and touch your probes to both ends. What does this mean?
4. Take out a breadboard and check which holes have continuity with which other holes. Draw yourself a diagram to keep track of your results.
5. Go around your house and check what has continuity with with other things – some examples: Does your kitchen faucet have continuity with its handle? Does your front door have continuity with its hinges? PLEASE BE CAREFUL! IN SOME HOUSES/COUNTRIES WITH INADEQUATE GROUNDING, PLUGGED IN APPLIANCES CAN LEAK DEADLY VOLTAGE TO METAL PARTS OF IT.

Multimeter Function: Resistance

What does it do?

If continuity checks whether or not two conductors are connected to each other, resistance is the logical continuation of this – it tells you how well those two things are connected, or more precisely, how much resistance exists in the path between both leads. Also known as the “Ohm” range and characterized by the “omega” symbol: “Ω“. The higher the displayed number, the less current will be able to flow once powered up and sometimes this translates directly to how good the connection is. In the future, I will show you how to tell how much resistance there should be between two points, but for now, you will be able to objectively measure it.

Note: some multimeters do not have a single resistance section, but many of what we call “ranges”. When you do not know what range of resistance you are expecting, I recommend trying it in a higher (or highest) resistance range and gradually move the dial down through the ranges until you get a useable reading.

Some concrete examples of what you would use the resistance function for:

• To check what is the resistance value of a resistor without having to read the resistor’s color code
  • Many people are color blind and can’t rely on reading color bands on resistors. Some resistors – particularly the blue ones – are simply difficult to read because they offer poor contrast for different colors.
• To check the quality of a soldered connection – or any connection, really.
• To know how much current will flow in a section of a circuit when power is applied

How to use it

This one is usually easier than continuity to get into. Simply look for the “Omega” symbol: Ω.

1. Put the black lead into the black COM jack
2. Put the red lead into the red jack with either the continuity (sideways wifi logo) or the Ohm (Ω) logo – they should both be on the same red jack – with other symbols on it too!
3. Turn the dial / select the range with the omega logo “Ω” or “Ohm“
4. Next, ensure that your device under test is disconnected from any power source. TESTING A DEVICE WHILE POWER IS APPLIED CAN RESULT IN DAMAGE TO YOUR MULTIMETER.
5. Touch one side of your device (which can be a piece of wire, a trace on a circuit board, a pin on a connector etc…) with one of your two probes (doesn’t matter which one!) and touch the second probe to wherever you want to check for a connection.
6. The multimeter will display a numerical value depicting the resistance between the probes
   • PAY SPECIAL ATTENTION to the range of the reading, it should be depicted on the screen by a symbol or a letter. A reading of 645 Ω is NOT the same as 645 kΩ! On both the above multimeters, you can see a “M” – this depicts Megaohms – or Millions of Ohms!

The higher the resistance value, the less current will be allowed to flow when the circuit or device is powered on. Air has a comparatively high resistance, which is why your multimeter doesn’t display a number when the probes are just in free air!

Practice exercises

1. On a piece of paper or in a text document, write down your best understanding of what resistance is, and what a high resistance means, and what a low resistance means.
2. Set your multimeter in resistance mode and touch the probes together. What is the reading? What is this reading telling you?
3. Check the resistance of a really thick piece of wire. A thin piece of wire. Why are they similar in resistance?
4. Take out a breadboard and check the resistance of connected holes. Are they all the same reistance?
5. Carefully press a multimeter lead into each one of your thumbs – not so hard that you pierce the skin! What is your body’s resistance?

Multimeter Function: Voltage

What does it do?

Checking voltage in a circuit or from a power supply is another one of the key functions of a multimeter and is where most of the protection circuitry on your multimeter is put into practice. The crux here is that the meter reads the difference between the voltage at the red lead and the voltage at the black lead. Trust me, it isn’t complicated! Voltage is measured in Volts with the symbol “V” except it is often divided into two separate sections; Volts A/C (denoted by a squiggly line “~” over or under the V) and Volts D/C (denoted by a symbol similar to an equal sign “=” but the lower line is a series of 3 dashes). For the most part, electronics deal in DC Voltage but the current coming from the wall outlet is moved by A/C Voltage. More on that in an other article!

Some concrete examples of what you would use the Voltage function for:

1. Checking the state of charge of a battery
2. Checking the output voltage of a power supply
3. Checking if an integrated circuit (IC) is receiving voltage
4. Checking the voltage drop across a conductor
5. Verifying if a capacitor is discharged (or charged!)

How to use it

Look for the Volts symbol “V” with the DC current symbol (a symbol similar to an equal sign “=” but the upper line is a series of 3 dashes). Note: some multimeters do not have a single voltage section, but many of what we call “ranges”. When you do not know what range of voltage you are expecting, I recommend trying it in a higher (or highest) voltage range and gradually move the dial down through the ranges until you get a useable reading.

1. Put the black lead into the black COM jack
2. Put the red lead into the red jack with the Voltage “V” symbol – with other symbols on it too!
3. Turn the dial to the DC Voltage range (a V with a symbol similar to an equal sign “=” but the lower line is a series of 3 dashes)
   • Note: Your multimeter may have a bunch of different ranges instead of one dial position. If you do not know how much voltage you are expecting, put it to a high value and turn the dial down gradually until you get a useable reading) The number on the range depicts the maximum voltage that specific range can read
4. Connect the red lead to one area you want to read voltage from (Example: the positive terminal of a battery)
5. Connect the black lead to the other area you want to read voltage from (Example: the negative terminal of a battery)
6. The multimeter will read the difference in voltage between the two leads. When you are a beginner you will likely be measuring across the entire power supply, so the number you read will probably be the full voltage available to the load.
   • If you measure the voltage backwards (i.e. the black lead on the positive of the battery, and the red lead on the negative of the battery) you will get a negative voltage. This is fine and you can totally disregard the negative symbol on the screen. Unless the voltage is not what it was supposed to be!

Please note that I did not specify to make sure your circuit is disconnected in this case. The circuit gets its voltage from its power source, whether that would be a battery, a power supply, a solar panel, etc… so you would need to have it plugged in to measure voltage. If your device is powered, you must be careful not to short out parts of the circuit to other parts using your metal test leads – you can damage your device under test.

WARNING!

If your device under test is plugged into the wall, you are exposing yourself to potentially deadly voltage. If you are new to using a multimeter, it is probably best NOT to practice by testing it on devices that plug into the wall until you understand which parts of it are safe to touch

Practice exercises

1. On a piece of paper or in a text editor, explain to the best of your abilities how the voltage measurement works
2. Find a battery and test its voltage. Compare the voltage on the screen to the voltage on the label of the battery.
3. Find a plug pack (wall wart or plug-in power supply) with a barrel jack. Put one probe in the middle and touch the other probe on the outside metal. How many volts are shown? Was it positive or negative voltage? What does that tell you?

Multimeter Function: Current

What does it do?

This is a complicated measurement to do compared to the other ones but in the big scheme of things, it is still very simple! The difficulty comes from the methodology of the test – in order to test current, the circuit has to not only be plugged into its power source, but it also needs to be active – that is to say current must be flowing. Current is measured in Amperes, usually shortened to Amps, with “A” as the symbol.

Some concrete examples of what you would use the current function for:

1. To check the power consumed by a device (current is half the variables needed for the power calculation)
2. To check what gauge of wire is required for a device (thicker gauge wire can carry more current)
3. To check if circuit protections are triggering

How to use it

This is the first measurement where you will have to go into one of those two other red jacks marked “A” or “µA” but if you are unsure of the current you are expecting, just use the A range first.

Note: Your multimeter should be fused in the “A” range, typically to 10 Amps, but this isn’t 100% true. Some inexpensive multimeters do not have a fuse and rely on you not holding the measurement for long and giving the shunt resistor time to cool down. If you go over that current level, you will damage your multimeter. A high quality multimeter will have replaceable fuses in both the A and the µA ranges.

Taking a current measurement requires you to break the working circuit and “insert” your multimeter leads into the circuit in series. Especially if you aren’t well versed in circuits at this point, it is probably best to look at the pictures below or the video at the end, but think of it this way; you disconnect a wire from the working circuit and replace each end of the disconnected wire with each one of your probes.

1. Put the black lead into the black COM jack
2. Put the red lead into the jack marked “A“
3. Turn the dial to the current range “A“
   • Note that you need to specifically select D/C current unless you are checking A/C current.
4. Disconnect one wire/connection from a complete circuit
5. Touch one probe to one end of the circuit where the wire was disconnected from
6. Touch the other probe to the other end of the circuit where the wire was disconnected from
7. The circuit will come back to life and your multimeter will give you a current reading.

WARNING!

Your multimeter can technically check A/C (mains) current but if you are just now learning to use your multimeter, you should not be practicing on A/C (mains) voltage from the wall, you would have the potential to touch mains voltage which can be deadly if you do not know what you are doing

WARNING#2!

Always take the red lead out of the “A” or “µA” jacks after you are done testing current. The leads should always be stored disconnected from the multimeter or in the V/Ω and COM ports.

Practice exercises

1. On a piece of paper or a text editor, write down the reasons why measuring current is more difficult than checking resistance.
2. Sketch out a diagram on how you would connect up your multimeter to check current
3. Put your sketch in action and measure the current of several circuits.

Ok I am eager to start, but I don’t own a multimeter, which do I buy?

If you’re just going to use it for low voltages (like below 60V) you can sort-of buy anything you want – in my opinion, low-end multimeters have gone way up in value in the last 15 years. In an effort to keep this brief, I have selected a few multimeters, which are linked via affiliate links below, which will serve you just perfectly. If you are going to use your multimeter in high voltage situations and especially if you’re going to use it above mains voltage (like commercial purposes) you must buy a good quality, professional grade multimeter. This is no joke, when we are talking high voltages, saving a few hundred dollars CAN COST YOU YOUR LIFE.

Here are my selections for cheap / good / better / best multimeters

Please note, these are just some of the ones I picked. I personally use my Kaiweets HT118A the most but I DO NOT work on even mains voltage. YMMV.

Cheap as chips:

Aneng AN8202 (USA)(Canada)(International)

Good:

Kaiweets HT118A (USA)(Canada)(International)

Better:

Extech EX355 (USA)(Canada)

Fluke 106 (USA)(Canada)(International)

Best / pro / high voltage selection:

Fluke 117 (USA)(Canada)(International)

Bryman BR235 EEVBLOG Multimeter (Dave Jones’ multimeter!)(USA)(Canada)(International)