How to Test VFD with Multimeter

The Variable Frequency Drive (VFD) stands as a cornerstone of modern industrial processes, providing precise control over motor speed and energy consumption. However, ensuring the proper functioning of a VFD is imperative for maintaining operational efficiency and preventing costly downtime.

How to Test VFD with Multimeter

Enter the multimeter, a versatile instrument that can prove invaluable in diagnosing VFD issues. By utilizing its various functions, technicians and engineers can perform a thorough assessment of the VFD’s electrical components, identifying potential faults and irregularities. Testing a VFD with a multimeter involves a systematic approach that entails measuring voltage, current, and resistance.

In this comprehensive guide, we delve into the step-by-step process of how to test VFD with multimeter. From understanding the unique characteristics of VFDs to navigating multimeter settings and interpreting readings, this article empowers professionals to confidently diagnose VFD problems, thereby contributing to seamless industrial operations.

What is VFD (Variable Frequency Drives) and Their Applications?

A Variable Frequency Drive (VFD) is a type of motor control that allows users to adjust the speed and torque of an AC induction motor. This is accomplished by varying the frequency of power supplied to the motor, which in turn adjusts its speed.

The main application for VFDs are pump and fan applications where variable speed operation can provide energy savings and system flexibility. VFDs can also be used in a wide variety of other applications, such as conveyors, mixers, crushers, and compressors.

Testing the performance of a VFD is important to ensure it operates correctly and efficiently. A common way to test a VFD is with a multimeter. Although the specific steps of testing the VFD vary depending on the type of multimeter and features available, there are some basic steps that all tests should follow to ensure accuracy.

First, connect one lead from the multimeter to a ground point, such as a motor frame or other metal surface. Next, attach the other lead to one of the power terminals on the VFD. This will measure the frequency of power being sent to the motor. If the VFD is operating correctly, it should display a “zero” reading on the multimeter.

Next, turn off all other loads connected to the VFD and reset it to its starting position before testing again. Then, adjust the speed setting on the VFD and observe the multimeter reading to ensure it is increasing or decreasing as expected. You should also test the VFD’s current output by attaching one lead of the multimeter to a ground point and the other to one of the power terminals, then adjust the speed setting on the VFD.

Importance of Testing VFDs for Proper Operation and Troubleshooting

Testing a Variable Frequency Drive (Vfd) With a Multimeter

Testing a variable frequency drive (VFD) with a multimeter is an important step when troubleshooting or doing regular maintenance on your system. By testing the VFD you can easily determine if it is working properly and identify any issues that could be causing problems. This guide outlines the steps to help you get started in testing and maintaining your VFD.

To begin, you will need to make sure your multimeter is set to the proper settings for testing. Set your multimeter’s dial to measure AC voltage and adjust the range setting according to the specification of your VFD. You can usually find this information in the manual that came with your drive or online at the manufacturer’s website.

Next, you will need to make sure your VFD is powered off and unplugged from its power source. Once it has been disconnected, you can now connect the multimeter to the VFD’s terminals. Make sure the positive (red) lead is connected to the terminal labeled “V+” and the negative (black) lead is connected to the terminal labeled “V-”.

Once the multimeter is connected to the VFD, you can now turn it on and check the readings. If your multimeter displays a voltage between 0V and 4V, then your VFD is working properly and you should not need to do any further testing or maintenance. However, if the reading exceeds 4V, then your VFD may need to be inspected and repaired.

10 Steps on How to Test VFD with Multimeter

Step 1: Safety Precautions

Before you begin testing a Variable Frequency Drive (VFD) with a multimeter, ensure your safety by wearing appropriate personal protective equipment, such as safety glasses and insulated gloves. Moreover, disconnect power sources, follow lockout-tagout procedures, and discharge capacitors to avoid electrical shocks.

Safety Glasses and Insulated Gloves

Step 2: Gather the Necessary Tools

Collect the required tools for the testing process. These typically include a digital multimeter capable of measuring voltage, current, and resistance, along with appropriate probes and leads.

Step 3: Familiarize Yourself with VFD

Understand the VFD’s structure, components, and electrical connections. Consult the manufacturer’s documentation to identify key components like input terminals, output terminals, control terminals, and any diagnostic LEDs.

Step 4: Set Up the Multimeter

Set your multimeter to the appropriate settings for the specific measurements you plan to take. For voltage and current measurements, select the appropriate AC or DC range, and ensure the probes are connected to the correct terminals.

Step 5: Measure Input Voltage

First, measure the input voltage to the VFD. Connect the multimeter probes to the input terminals of the VFD. Power on the VFD and observe the voltage reading on the multimeter. It should match the nominal voltage supplied to the VFD.

Step 6: Measure Output Voltage

Next, measure the output voltage of the VFD. Connect the multimeter probes to the output terminals of the VFD that connect to the motor. Run the motor at different speeds and observe the voltage readings. They should correspond to the VFD’s programmed output voltage for each speed.

Step 7: Measure Output Current

Measure the output current to ensure it matches the expected values. Use a clamp meter or an appropriate multimeter setting to measure the current flowing to the motor while it’s running. Compare the readings to the VFD’s rated current output.

Step 8: Test Control Signals

Examine the control signals going into the VFD. Connect the multimeter probes to the control terminals where external control signals are connected. Confirm that the VFD is receiving the expected control signals, such as start/stop signals and speed reference signals.

Step 9: Check for Abnormalities

While testing, monitor the VFD for any abnormal behaviors such as unusual noises, erratic voltage or current readings, or abnormal heat generation. These signs might indicate potential issues within the VFD.

Step 10: Interpret Results

Interpret the multimeter readings and compare them with the VFD’s specifications and the manufacturer’s guidelines. Discrepancies between the readings and the expected values could indicate faults or issues. Consult the manufacturer’s documentation or seek the expertise of a qualified technician to diagnose and address any identified problems.

A Qualified Technician to Diagnose

Things to Consider When Testing VFD with Multimeter

When testing a VFD with a multimeter, there are several important factors to keep in mind. First, make sure that the battery voltage is correct and that the device is properly connected to power. Additionally, it is important to use caution when accessing any part of the system or making connections as electrical shock can cause serious injury or death.

Next, it is important to ensure that the multimeter is correctly calibrated for VFD testing. Typically, this is done by adjusting the meter’s settings and selecting the appropriate DC voltage range. To ensure accuracy, it is also important to test leads regularly and verify that they are securely connected.

Once all of these steps have been completed, testing can begin. The most common tests involve measuring the input and output voltage of the system. The multimeter should be used to measure the incoming AC power, to make sure that it is within the acceptable range. In addition, the VFD’s output voltage can be tested by connecting a load resistor or incandescent lamp between phase A and B on the control panel.

Some Common Mistakes to Avoid When Testing VFD with Multimeter

It is important to be mindful when testing a variable frequency drive (VFD) with a multimeter. Doing so properly requires careful attention and precision, and it’s easy to make mistakes that can create costly problems. Here are some common mistakes to avoid:

  1. Failing to use the correct settings on the multimeter. A VFD is a complex device, and the multimeter settings must be adjusted accordingly. To properly test a VFD with a multimeter, make sure to use the proper resistance or voltage setting for measuring AC current.
  2. Testing without disconnecting all power sources first. Before performing any testing on a VFD, always be sure to completely disconnect it from all power sources. Failure to do so can lead to serious harm or even death.
  3. Not noting any damage on the VFD before testing, If you notice any signs of physical damage or corrosion on the VFD before testing, be sure to write them down and take pictures as evidence. This will help you identify potential problems that may have led to the damage.
  4. Not having a thorough understanding of VFDs beforehand. Before attempting to test a VFD with a multimeter, it is important to have an in-depth understanding of how the device works and how to properly use the multimeter for testing purposes. Without this knowledge, you could end up making costly mistakes due to lack of experience.
Use the Multimeter for Testing Purposes


Testing a Vfd with a multimeter is one of the simplest and most accessible ways to ensure your device is functioning properly. With the step-by-step instructions outlined in this post, you’ll be confident that you can measure voltage and check for any issues without much trouble.

What’s more, having a basic understanding of Vfd testing can potentially save you time and money if you ever come across an issue with any of your VFDs. Remember, whether it is performing tests or replacements, always consider safety first when dealing with power sources. To find out more about How to Test Vfd with Multimeter, have a look at our comprehensive blog post now!

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Enrique Howard

Hi, I am Enrique. I started my professional life as a handyman and did a lot of external and internal repair of home and office with a little bit of electric and plumbing support. I have extensive experience in tools testing such as drilling, turning, milling, and non-conventional machining like EDM. So let me help you on your journey towards becoming an enlightened DIYer with amazing tools that you can use on your project.

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