Pingshang Technology teaches you how to test diodes
September 03 11:30:15, 2025
How to Test if a Diode is Good or Bad
Using a multimeter is one of the most effective ways to test the condition of a diode. Before starting, make sure your multimeter is set to the RX1K ohm range (avoid using the RX1 setting as it may damage the diode). Next, short the red and black leads together to calibrate the meter to zero resistance.
1. **Forward Bias Test**
Connect the black probe of the multimeter to the anode (positive terminal) of the diode and the red probe to the cathode (negative terminal). If the needle moves slightly but doesn’t reach zero, this reading represents the forward resistance. A good diode should show a low resistance value, typically in the range of hundreds to thousands of ohms. If the resistance reads 0, the diode is shorted and damaged. If it shows a very high or infinite resistance, the diode is open and not functioning. In either case, the diode should be replaced.
2. **Reverse Bias Test**
Now reverse the probes: place the red probe on the anode and the black probe on the cathode. In a properly working diode, the meter should show a very high resistance or "infinity." This indicates that the diode is blocking current in the reverse direction, which is its normal behavior. If the needle moves significantly or shows a low resistance, the diode is faulty and needs to be replaced.
By performing both the forward and reverse tests, you can accurately determine whether a diode is in good condition or defective. Always make sure to handle the diode carefully and double-check your connections to avoid incorrect readings.
This method is widely used by technicians and hobbyists alike for quick and reliable diode testing. Whether you're working on electronics projects or troubleshooting a circuit, knowing how to test a diode is a valuable skill.
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