How to Use a Multimeter (Basic Guide for Beginners)

Is the chain broken? Is your switch working? Perhaps you want to know how much power is left in your batteries.

Either way, a multimeter will help you answer these questions! Digital multimeters have become indispensable tools for evaluating the safety, quality, and faults of electronic devices.

Multimeters are extremely useful for diagnosing various electrical components. In this handy guide, I'll walk you through what you need to know about using a multimeter with its basic features.

What is a multimeter?

A multimeter is an instrument that can measure a wide range of electrical quantities. You can use it to find out what's going on with your circuits. This will help you in debugging any component in your circuit that is not working properly.

In addition, the multimeter's outstanding versatility comes from its ability to measure voltage, resistance, current, and continuity. Most often they are used to check:        

• Sockets in the wall
• adapters
• Technique
• Electronics for home use
• Electricity in vehicles

Multimeter Spare Parts 

A digital multimeter consists of four main parts:

Monitor

This is a panel that displays electrical measurements. It has a four-digit display with the ability to display a negative sign.

Selection knob 

This is a round dial where you can select the type of electrical unit you want to measure. You can select AC volts, DC volts (DC-), amps (A), milliamps (mA), and resistance (ohms). On the selection knob, a diode sign (a triangle with a line to the right) and a sound wave symbol indicate continuity.

Probes

These are the red and black wires used for physical testing of electrical components. There is a pointed metal tip on one end and a banana plug on the other. The metal tip examines the component under test, and the banana plug is connected to one of the multimeter's ports. You can use the black wire to test for ground and neutral, and the red wire is usually used for hot terminals. (1)

Ports 

Multimeters usually include three ports:

• COM (-) - indicates a common and where the black probe is usually connected. The ground of a circuit is usually always connected to it.
• mAΩ - the place where the red probe is usually connected to control voltage, resistance and current (up to 200 mA).
• 10A - used to measure currents over 200 mA.

Measuring voltage

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

Battery voltage

To measure the voltage of a battery, such as an AA battery:

1. Connect the black lead to COM and the red lead 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 test lead to "-" on the "ground" of the battery, and the red test lead to "+" or power.
4. Lightly press the probes against the positive and negative terminals of the AA battery.
5. You should see about 1.5V on the monitor if you have a brand new battery.

Circuit voltage 

Now let's look at the basic circuit for voltage control in a real situation. The circuit consists of a 1k resistor and a super bright blue LED. To measure voltage in a circuit:

1. Make sure the circuit you are working on is enabled.
2. In the DC range, turn the knob to "20V". Most multimeters do not have autorange. So, you must first set the multimeter to the measurement range that it can handle. If you are testing a 12V battery or a 5V system, select the 20V option. 
3. With some effort, press the multimeter probes on two open areas of metal. One probe should make contact with the GND connection. Then the other sensor should be connected to the VCC or 5V power supply.
4. You have to watch the entire voltage of the circuit if you are measuring from where the voltage enters the resistor to where the ground is on the LED. After that, you can determine the voltage used by the LED. This is called LED voltage drop. 

Also, it won't be a problem if you select a voltage setting that is too low for the voltage you are trying to measure. The counter will simply show 1, indicating an overload or out of range. Also, flipping the probes will not hurt you or cause negative readings.

Current measurement

You must physically interrupt the current and connect the meter to the line to measure the current.

Here if you are using the same circuit we used in the voltage measurement section.

The first item you will need is a spare strand of wire. After that you must:

1. Disconnect the VCC wire from the resistor and add a wire.
2. A probe from the power output of the power supply to the resistor. It effectively "breaks" the power circuit.
3. Take a multimeter and stick it in line to measure the current flowing through the multimeter into the breadboard.
4. Use alligator clips to attach multimeter leads to the system.
5. Set the dial to the correct position and measure the current connection with a multimeter.
6. Start with a 200mA multimeter and gradually increase it. Many breadboards draw less than 200 milliamps of current.

Also, make sure you connect the red lead to the 200mA fused port. To be careful, switch the probe to the 10A side if you expect your circuit to use around or more than 200mA. In addition to the overload indicator, overcurrent can cause a fuse to blow.

Resistance measurement

First, make sure that no current is flowing through the circuit or component you are testing. Turn it off, unhook it from the wall and remove the batteries, if any. Then you should:

1. Connect the black lead to the multimeter's COM port and the red lead to the mAVΩ port.
2. Turn on the multimeter and switch it to resistance mode.
3. Set the dial to the correct position. Because most multimeters don't have autorange, you'll have to manually adjust the range of the resistance you'll be measuring.
4. Place a probe at each end of the component or circuit you are testing.

As I mentioned, if the multimeter is not displaying the actual value of the component, it will either read 0 or 1. If it reads 0 or closer to zero, your multimeter's range is too wide for accurate measurements. On the other hand, the multimeter will show one or OL if the range is too low, indicating overload or overrange.

Continuity test

A continuity test determines if two objects are electrically connected; if they are, electric current can flow freely from one end to the other.

However, if it is not continuous, there is a break in the chain. It could be a blown fuse, a bad solder joint, or a poorly connected circuit. To test it, you must:

1. Connect the red lead to the mAVΩ port and the black lead to the COM port.
2. Turn on the multimeter and switch it to continuous mode (indicated by an icon that looks like a sound wave). Not all multimeters have a continuous mode; if you don't, you can switch it to the lowest dial setting of its resistance mode.
3. Place one probe on each circuit or component 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). Low resistance is another way to determine continuity in resistance mode.

On the other hand, if the screen shows one or OL, there is no continuity, so there is no channel for electrical current to flow from one sensor to another.

See the list below for additional multimeter training guides;

• How to use a multimeter to check the voltage of live wires
• How to check the battery with a multimeter
• How to test a three-wire crankshaft sensor with a multimeter

Recommendations

(1) metal - https://www.britannica.com/science/metal-chemistry

(2) straight line - https://www.mathsisfun.com/equation_of_line.html