How to Use a Multimeter (Basic Guide for Beginners)

Is a circuit broken? Is your switch functional? Perhaps you want to know the amount of power left on your batteries? Whatever the case, a multimeter can help you answer those questions! Digital multimeters have become indispensable tools for evaluating electronic devices’ safety, quality, and malfunctions.

In general, with the use of a multimeter, you can measure or test: 

  • Voltage (battery and circuit)
  • Current 
  • Resistance
  • Continuity

Multimeters are extremely useful for diagnosing various electrical components. In this handy guide, I’ll educate you on the things you need to know about to use a multimeter with its basic functions.

What is a Multimeter?

different multimeter

A multimeter is a tool that can measure a wide range of electrical values. You can use it to figure out what’s happening with your circuits. It will assist you in debugging any component in your circuit that isn’t working correctly. Moreover, the multimeter’s outstanding versatility stems from its capacity to measure voltage, resistance, current, and continuity. They are most commonly used to test:        

  • Outlets in the wall
  • Adapters
  • Appliances
  • Electronics for home use
  • Electricity in vehicles

Multimeter Parts 

multimeter testing a battery

A digital multimeter is made up of four main sections:

Display

This is the pane that displays the electrical measurements. It has a four-digit display with the capacity to show a negative sign.

Selection Knob 

It’s a round dial on which you can select the type of electrical unit you want to measure. You can choose from AC volts, DC volts (DC-), amps (A), milliamps (mA), and resistance (Ω). On the selection knob, a diode sign (triangle with a line on the right side) and/or a soundwave symbol indicate continuity.

Probes

These are red and black wires used to test electrical components physically. There’s a pointed metal tip on one end and a banana plug on the other end. The metal tip probes the component being tested while the banana plug connects into one of the multimeter’s ports. You can use the black cord to test Ground and neutral connections, while the red wire is typically used to test hot terminals. (1)

Ports 

Multimeters commonly include three ports:

  • COM (-) – stands for common and where the black probe is usually plugged. A circuit’s Ground is usually always linked to it.
  • mAVΩ – is where the red probe is conventionally plugged to monitor voltages, resistance, and current (up to 200mA).
  • 10A – is used to measure currents greater than 200 mA.

Measuring Voltage

You can perform either DC or AC voltage measurements with a digital multimeter. DC voltage is the V with a straight line on your multimeter. On the other hand, AC voltage is the V with a wavy line. (2)

Battery’s Voltage

To measure a battery’s voltage, such as an AA battery:

  1. Connect the black probe to the COM and the red probe to mAVΩ.
  2. In the DC (direct current) range, set the multimeter to “2V.” Direct current is used in almost all portable devices.
  3. Connect the black probe to the ‘-‘ on the battery’s Ground and the red probe to the ‘+’ or power.
  4. Apply a light squeeze to the probes against the AA battery’s positive and negative terminals.
  5. You should see roughly 1.5V on the monitor if you have a brand-new battery.

Circuit’s Voltage 

Now, let’s look at the basic circuit to monitor the voltage in a real-world situation. The circuit consists of a 1k resistor and a Blue ultra-bright LED. To measure voltage in a circuit:

  1. Make sure to turn on the circuit you’re working on.
  2. In the DC range, turn the knob to “20V.” In most cases, multimeters are not auto-range. So, you must first set the multimeter to a measurement range that it can handle. If you’re testing a 12V battery or 5v system, select the 20V option. 
  3. Push the multimeter probes onto two exposed sections of metal with some force. One probe should contact a GND connection. Then, the other probe should connect to the VCC or 5V supply.
  4. You should observe the whole voltage of the circuit if you measure from where the voltage enters the resistor to where Ground is on the LED. After that, you can then determine the voltage used by the LED. It’s referred to as the voltage drop across the LED. 

Furthermore, it’s not a problem if you choose a voltage setting that’s too low for the voltage you’re trying to measure. The meter will just read 1, indicating overloaded or out of range. Also, inverting the probes will not injure you and result in a negative reading.

Measuring Current

multimeter test

You must physically interrupt the current flow and connect the meter to the line to measure the current. Here, assuming you use the same circuit we used in the voltage measurement section. The first item you’ll need is a spare wire strand. After that, you should:

  1. Disconnect the VCC wire from the resistor and add a wire in its place.
  2. Probe from the power supply’s power pin to the resistor. It effectively “breaks” the circuit’s power.
  3. Get your multimeter and insert it in-line to measure the current as it flows through the multimeter into the breadboard.
  4. Use alligator clips to hold the multimeter probes to the system.
  5. Set the dial to the right setting and measure the current connection with the multimeter.
  6. Start with a 200mA multimeter and work your way up from there. Many breadboard projects use less than 200 milliamps of current.

Additionally, ensure that you connect the red probe to the 200mA fused port. To be cautious, swap your probe to the 10A side if you anticipate your circuit will use near to or more than 200mA. In addition to an overload indicator, overloading the current can blow a fuse.

Measuring Resistance

multimeter test 01

To begin, ensure there is no current flowing through the circuit or component you’re testing. Turn it off, unhook it from the wall, and take out any batteries if it has any. Then, you should:

  1. Connect the black probe to your multimeter’s COM port and the red probe to the mAVΩ port.
  2. Turn your multimeter on and switch it to resistance mode.
  3. Set the dial to the right setting. Now, since most multimeters aren’t auto-ranging, you’ll have to manually adjust the range for the resistance you’ll be measuring.
  4. Place a probe at each end of the component or circuit you’re testing.

As I’ve mentioned, if the meter does not display the component’s actual value, it will read either 0 or 1. If it reads 0 or closer to zero, the range on your multimeter is set too high for accurate measurements. On the other hand, the multimeter will just read 1 or OL if the range is too low, indicating overload or out of range.

Continuity Test

multimeter continuity test

A continuity test determines if two objects are electrically connected, and if they are, an electric current can freely pass from one end to the other. However, if it’s not continuous, there is a break in the circuit. It could be a blown fuse, a faulty solder connection, or a poorly wired circuit. To test it, you must:

  1. Connect the red probe to the mAVΩ port and the black probe to the COM port.
  2. Turn on your multimeter and switch it to continuity mode (indicated by an icon that looks like a sound wave). Now, not all multimeters have continuity mode, and if yours doesn’t have it, you could switch it to the lowest dial setting of its resistance mode.
  3. Put one probe at each circuit or component’s end you want to test.

If your circuit is continuous, the multimeter beeps and the screen displays a value of zero (or close to zero). In the resistance mode, having a meager resistance is the other way to determine continuity. On the other hand, if the screen displays 1 or OL, there is no continuity, so there is no conduit for the electric current to travel from one probe to the next.

For more multimeter how-to learning guides, check the below list;






References
(1) metal – https://www.britannica.com/science/metal-chemistry
(2) straight line – https://www.mathsisfun.com/equation_of_line.html

About Sam Orlovsky

b1d87d2ee85af3e51479df87928bdc88?s=90&d=mm&r=gI realized early on carpentry was a huge passion for me and I’ve stayed in the industry for over 20 years now. This gives me a unique ability to really be able to tell you what the best tools and recommendations are. I’m not only a carpenter but I also like machinery and anything to do with electrics. One of my career paths starting off was as an apprentice electrician so I also have a lot of experience with electrical products and anything related.