A diode is the simplest semiconductor device. Used for rectifying alternating current to direct current, for blocking and limiting voltages, as well as for lighting and indication. Check the efficiency of the diode with a multimeter with a diode test function.
Instructions
Step 1
Before checking an element, exclude it from the wiring diagram, as external circuits may distort measurements. Before touching the terminals of the element and the device with your hands, touch the ground to discharge any static electricity that has accumulated in your body. Sensitive elements are capable of failing even from such a charge. Turn on the diode health check function on the multimeter (tester).
Step 2
Touch the test leads of the tester to both outputs of the element. It is important to observe the correct polarity. Connect the red test lead to the positive output of the diode (anode), the black test lead to the negative lead (cathode). To find the cathode on a diode, inspect both outputs of the element carefully. A stripe near one of them indicates the cathode. Do not touch the metal parts of the tester probe and diode leads with your hands.
Step 3
Take a multimeter reading. Then touch the red probe of the device to the cathode, and the black one to the anode and take the readings again. If, during the first reading, the tester gave a value close to zero (but not equal), and went off scale during the second, the diode is operational. If the tester goes off scale on both readings, the diode is faulty. A break has occurred within an element. If during both readings the tester showed zero, then the diode is short-circuited.
Step 4
If there is no digital tester with diode test function, test with an ohmmeter or analog (pointer) multimeter. To do this, turn on the device in the resistance measurement mode with the maximum possible limit. Connect the red lead of the tester to the anode and the black one to the cathode of the element under test. The meter should show negligible resistance. After changing the pins in places, the tester should show infinitely high resistance.
Step 5
For light-emitting diodes, the correct connection and serviceability check are performed visually.
