Sep 275 min read

How to Measure Voltage With a Multimeter

Follow Along on SkillCat: "Using a Multimeter" Course!

In this multimeter use guide, learn how to measure AC and DC voltage.

Want to test your knowledge? Skip to the quiz!

Things to Keep in Mind:

There are two types of multimeters: digital multimeters and clamp multimeters. Most of what is pictured in this guide is a digital multimeter.
- Multimeters can be used to measure various measurements:
  - Measure voltage in Volts - this if the focus of this guide!
  - Measure current in Amperes
  - Measure resistance in Ohms
  - Measure continuity in Ohms
  - Measure capacitance in Farads
  - Measure temperature in Farenheit or Celcius
- Multimeters have 2-4 ports for the provided test leads or probes to be plugged into.
  - Probes have one end of the wire called the plug end that plugs into the multimeter port. The other end of the wire called the probe end is used to touch the component of measurement.
  - Remember that black probe represents the negative probe, and red probe represents the positive probe.
  - Ensure that the probe ends of your probes do not touch as you measure using the multimeter, as that can short the circuit and become a safety hazard.
  - Instead of test probes, alligator clips can also be used.
- Ensure that your multimeter can measure the range of Volts of the equipment you are working on. Be especially careful with high voltages. Some multimeters may be able to measure higher voltages than others.
- Use the multimeter dial to ensure you're measuring the right measurement. In this post, we'll be working with the two different V symbols for voltage.
Voltage is measured in units of Volts.
There are two types of current: direct current (DC) and alternating current (AC). With DC, the current flows in one direction. With AC, the current will periodically alternate the direction it flows in. Each produce a unique voltage you can measure.

1. Setting Up

Start by getting your multimeter ready for measuring voltage. Plug your test leads or probes into the correct ports on your multimeter.

For measuring voltage, the plug end of the red probe plugs into the port marked with the "V” symbol, the symbol for voltage. The plug end of the black probe will be plugged into the port marked with “COM”.

Multimeter dial showcasing voltage measurement in volts while testing DC voltage.png

Keep in mind that alternating current (AC) and direct current (DC) each produce a unique voltage. Voltage coming from an AC system is called AC voltage. Likewise, voltage coming from a DC system is called DC voltage. Before taking any measurements, set your multimeter dial to either AC or DC voltage. The “V” symbol with a wavy line above it is for AC voltage; the “V” symbol with a solid and dashed line above it is for DC voltage.

Each dial position on a multimeter can have multiple measurements. It is common for AC and DC voltage to be on the same dial position. If they are on the same dial position, use the “function” key to switch between AC or DC voltage. For example, if you want to measure AC voltage, rotate the dial on your meter to its appropriate symbol. Then, you would press the function key until “AC” and “V” are displayed on the screen.

2. Measuring Voltage

Now that your multimeter is set to voltage measurement, let’s go through the process of measuring Volts using your probes.

First, determine if the system you are testing runs on AC or DC power. Usually, you can find this information on the schematic. Set your multimeter dial accordingly to measure AC or DC voltage.

When measuring voltage, place your probes in parallel with the component. In parallel means that there are multiple paths for current to flow through a circuit. Parallel components will have reduced current, but the same voltage as each other. To place your probes in parallel, you do not need to disconnect the circuit. You will place the tip of one probe on the entrance and the tip of the other probe on the exit of the component.

Measuring DC Voltage

When you are measuring DC voltage, the placement of your test probes effects the measurement. Since current flows in one direction in a DC circuit, each component has a positive and a negative end. For some components, the positive end will be marked in red, while the negative end will be marked in black. Place the probe end of the red probe on the positive end and the probe end of the black probe on the negative terminal of the component you are measuring.

If your multimeter displays a measurement of negative Volts, it means that your test leads are in the wrong position. To fix this, switch the order of your probes. Your black probe should go where your red probe is; your red probe should go where your black probe is. The measurement you see on the multimeter display should showcase the voltage in Volts.

For example, let's say that you wanted to measure the voltage across a 12 Volts DC battery. The red probe will go on the terminal marked with a “+” sign. The black probe will go on the terminal with a “-” sign. The voltage measurement will appear on the multimeter display. For example, it should appear as 12 Volts.

Measuring AC Current

Recall that AC circuit alternates direction. Because the current changes direction, there is no positive or negative side of components like in DC voltage. Your multimeter will not display a measurement of negative Volts while reading AC voltage.

Just like DC voltage, you need to place your probes in parallel with the component. Since there is no positive or negative terminals, you can place your red probe and black probe on either terminal of the component. The voltage and unit of Volts will appear on your multimeter display. For example, measuring an AC circuit of 5 Volts should prompt your multimeter to display a voltage of 5 Volts.

Recall that some multimeters require you to manually set the range of your measurement. If your multimeter is not auto ranging, you will need to change the range to get a more accurate measurement in Volts. Slowly turn the dial to lower ranges until you get an accurate measurement.

Quiz

Now that you know how to measure voltage using a multimeter and report the voltage of an AC or DC current in Volts, test your knowledge with a quick quiz!

Question #1: "V" is the universal symbol for voltage on a multimeter.

True
False