How to Test a Small Electric Motor with a Multimeter

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Let’s be honest. Electric motors are complex and intricate pieces of equipment. They could stop functioning for many different reasons. Both DC motors and AC motors could develop similar issues. 

Whether it is from wear and tear, lack of maintenance, or just old age, failure happens because of many causes. Having a preventative maintenance program in place is an excellent way to keep an eye on your electric motor’s health. It helps you determine, assess, and fix potential problems that arise over time and require repair service. 

What is a Small Electric Motor? 

A small electric motor runs a broad spectrum of electrical devices like:

  • computers
  • children’s railroad sets
  • remote control models
  • and more 

These small electric motors feature:

  • two small permanent magnets
  • three poles
  • two brushes
  • a commutator, and;
  • an electromagnet designs by winding wire around a piece of metal. 

It functions the same as a bigger electric motor does, but on a very much smaller scale. 

They typically run on low-voltage electricity—six to twenty-four volts—and are powered by a transformer or batteries that lower 110 volts to the needed low voltage. If any, there are some serviceable parts in small electric motors. Normally, it is less cheap to purchase a replacement instead of trying to fix them.

Nonetheless, is your small electric motor currently not working? You can utilize a digital multimeter to test it before you consider replacing it. The issue could be the power source or the wiring and not the electric motor itself. 

How Does an Electric Motor Work? 

Take note that an electric motor revolves around magnets and magnetism. A motor utilizes a magnet to create a motion. 

Have you ever played with magnets in your childhood? Then you are familiar with the basic law of all magnets: opposite attracts, and the like charge repels. Let’s say you have two bar magnets with each end marked south and north. 

The magnet’s north end will attract the south end of the other. On the contrary, one magnet’s north end will repel the north end of the other (and likewise, south will deter south). Those repelling and attracting forces make rotational motion inside a small electric motor. 

A toy motor is a good example of a small electric motor. Try to get one toy motor, and you’ll see what we’re trying to say here. A small electric motor is just as big as a dime. 

From the outside, you’ll see the steel can that shapes the motor’s body, a nylon end cap, an axle, and two battery leads. Try to hook the motor’s battery leads to a flashlight battery, and the axle will spin. But if you reverse the leads, it will spin oppositely. 

On the other hand, the nylon end cap is seized in place by two taps, which are a portion of the steel can. Twisting the tabs back helps release the end cap and eliminate it. You will find the motor’s brushes inside the end cap. 

Those brushes send and move power from the battery to the commutator as the electric motor spins. 

How Do You Test a Small Electric Motor?

Electric current comes out of the battery’s positive end and goes through the toy’s bulb and then back to the battery. That’s an electric circuit. 

But what do you do to measure the electric current? This is where a digital multimeter comes in. This device can measure both the voltage and current. But most multimeters could do more than that—measuring capacitance and resistance, among other things. 

The key to measuring electric current lies to the multimeter itself—it should be in the path of the current. Further, you need to be certain you use the proper plugs and proper settings. Many multimeters have a switch to put it in ammeter mode and distinct plugs to compute the electric current. 

Below are the crucial steps you can follow to test your small electric motor with a multimeter. 

  1. Check the label on the small electric motor to identify the voltage it needs to work. Consider making a note of the voltage on a piece of paper. 
  1. Find and get the two small metal terminals on your small electric motor. They are located near the back and have two colored wires—normally black and red connected to them.
  1. Turn on the power unit, which supplies electricity to your small electric motor. Make sure you check if electricity is transferring to the motor.
  1. For the next step, turn on your digital multimeter. Make sure it’s set to measure volts as a multimeter. Remember that it could measure ohms and amperes too. 
  1. Insert the copper sensors running from the meter into the small electric motor’s metal terminals. The sensors on the red wire’s end from the multimeter should touch the terminal, which has a red wire connected.

The sensor on the black wire’s end from the multimeter should touch the terminal, which has a black wire connected. Your job here is to make sure you don’t touch the motor’s outer casing, as it may give you inaccurate readings.

  1. Check the meter’s measurement. Does it have the same or similar measure to the voltage you noted earlier? Then, it means the power is reaching the motor. But if you have wrong readings and the motor is not working, it’s a clear sign the electric motor has an issue and needs replacing. If you don’t receive a measurement, it suggests the power is not reaching the electric motor. 
  1. Check the power source. Get the two terminals and insert the sensors from the multimeter wire’s ends onto the two terminals as before. (Check step #5.) 
  1. Read the reading on the multimeter. The power source is producing electricity if it reads the exact or similar voltage as you noted. If you do not receive a reading or the reading is low, you have an issue with the power source instead of the electric motor.

There you have it! Above is all the information you need to test a small electric motor with a multimeter. We hope you find this post enlightening and useful at the same time. Are you ready to test your electric motor using a multimeter? We wish you the best of luck!

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