Project Guide

How to Use a Multimeter

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Measuring AC Voltage
Someone using a multimeter on a jobsite

Measuring AC is the most common usage of a multimeter. Knowing how to use a digital multimeter makes it easy to check to see if a plug in the wall or even a surge protector is working properly. 

  • Step 1: Connect the black probe to the common jack on the multimeter. Then, connect the red plug to the jack labeled for AC voltage.
  • Step 2: Set the mode on your multimeter to AC voltage. Use a large enough range to work for the device you’re testing. If you’re testing a plug in the US, you’ll need to make sure your multimeter is set to and capable of handling 120 volts.
  • Step 3: Place the end of the common or black probe into the neutral slot on the plug. Then, place the positive or red probe into the hot slot on the plug. 
  • Step 4: Check your reading. Plugs in the US should show a range of approximately 120-volts AC.
Measuring DC Voltage
Someone using a multimeter on an engine

One of many electrical tools for checking batteries and power supplies, a multimeter makes it easy to test DC voltage. 

  • Step 1: Plug your multimeter probes into the jacks labeled common and DC voltage. Use the black plug for common and the red plug for DC voltage.
  • Step 2: Adjust your multimeter to measure DC voltage. Some models have a knob, while others use a push button. Adjust the knob according to the expected measurement if required.
  • Step 3: Touch the probe connected to the DC voltage plug to the positive terminal you’re testing. Touch the common plug to the negative terminal.
  • Step 4: Make note of your reading. If your reading is negative, you may need to switch the black and red probes for a positive reading.
Measuring Resistance
Someone using a multimeter to measure resistance

Measuring resistance is a common task for those who want to repair electrical components. Here’s how you can test resistors for a repair project:

  • Step 1: Disconnect the component that you’re testing from all live circuitry. Ideally, your test component should be isolated and not connected to anything.
  • Step 2: Plug your multimeter probes into the jacks labeled common and DC voltage. Use the black plug for common and the red plug for DC voltage.
  • Step 3: Set your multimeter to the ohm meter function. Choose a measurement range that seems correct for your resistors. If you’re not sure of your range, start measuring around 200-ohms (the unit of electrical resistance). Some models will show a “1” reading if the resistor has a higher capacity than your current setting.
  • Step 4: Move the ohm range up on your multimeter one step at a time. Once you reach a high enough range, you’ll see a more accurate display. For example, you may see a “1” on a 3k-ohm resistor until you move above the 2k-ohm range on your multimeter. If you’re not getting a proper reading, you may need to turn down the sensitivity on your multimeter. 

If you’re testing multiple resistors, alligator clip probes make this job much easier and are an essential addition to your measurement and layout tool kit.

Choosing the Right Multimeter
DIfferent types of multimeters on a table

Now that you understand the basics, you can begin to pick the right multimeter for your job. While a basic model will help you tackle measurements like DC voltage, AC voltage and resistance, some models are easier to read and more accurate. Here are a few popular options you can choose from when shopping for a multimeter:

  • Digital multimeters. These are an ideal option for heavy day-to-day users and DIY homeowners. Easy-to-read displays and auto functions make taking readings quick and easy for most basic tasks. Top brands like Fluke make a wide range of multimeters designed with basic and more specific functions in mind.
  • Analog multimeters. Simple and easy to use, these are cost-effective meters that often take just a little longer to dial in. They are still highly effective for tasks like measuring AC and DC voltage.