Testing Diodes/LED (Light Emitting Diodes) Using Digital Multimeter - Electronics LAB

Although you can easily test an LED by connecting it to a circuit and seeing if it will light up, you can also use a multi-meter with a diode test function to test an LED and discover a few more things about it too.
  1. Connect the black lead to the COM terminal on the multimeter. 
  2. Connect the red lead to the Ω terminal, unless your particular model differs. 
  3. Turn the dial to the diode symbol on the multimeter. This allows for electric current to travel in one direction (the arrow) and not the other.
  4. Turn the multimeter on. The display window should indicate either 0L or OPEN. 
  5. Choose a regular red LED.
You may like our Multimeter related Posts
Testing AC Voltage
Testing DC Voltage
Testing Continuity
Testing Resistors
Measuring Current
Testing Diodes/LED (Light Emitting Diodes)

Connect the black probe to the cathode end of the LED, which usually is the shorter end and/or cut flat at its bottom. Connect the red probe to the anode end of the LED. 

Video Tutorial:Testing Diodes/LED (Light Emitting Diodes)

LED Forward Voltage Drop
The value displayed on your multimeter is called the forward voltage drop. This indicates the quantity of voltage used up by the LED, or dropped, when current is travelling in the appropriate direction, forward.

This data is extremely useful when it comes to building your own robot or designing your circuit board. Keep track of the total voltage used by your robot, whether it is from a LED or some other component, in order to choose a battery strong enough to power it.


  1. Nice guide on testing diodes!

  2. Our Readers feedback is important for us.Hope You guys enjoy reading articles on this Blog.Keep visiting for more stuffs.

  3. The same testing method that is used on simple electrical wires can be used on complicated appliance circuits as well. Fluke 115 Digital Multimeter