How can a semiconductor diode be tested whether it is defected by means of an ohmmeter
How can a semiconductor diode be tested whether it is defected by means of an ohmmeter?
Answer:
Testing a semiconductor diode to determine if it is defective using an ohmmeter (or multimeter) involves measuring the resistance of the diode in both forward-bias and reverse-bias directions. Here’s a detailed step-by-step guide on how to test a diode using an ohmmeter:
Step 1: Set the Ohmmeter
- Set your ohmmeter or digital multimeter to the resistance (Ω) mode. If your multimeter has a diode test mode, it is even better, as it provides more accurate readings for diodes.
Step 2: Identify the Diode Terminals
- Identify the anode and cathode of the diode. The anode is the positive side, while the cathode is the negative side. The cathode is often marked with a stripe.
Step 3: Measure Forward Resistance
- Connect the probes:
- Connect the positive (red) probe to the anode and the negative (black) probe to the cathode.
- Read the resistance:
- Observe the reading on the ohmmeter. A healthy diode will show low resistance (often between 0.5 to 0.9 V if using the diode test mode, or a few ohms in resistance mode).
Step 4: Measure Reverse Resistance
- Switch the probes:
- Now, connect the positive (red) probe to the cathode and the negative (black) probe to the anode.
- Read the resistance:
- Observe the reading on the ohmmeter. A healthy diode will show high resistance (usually an open circuit or very high resistance value, indicating no current flow).
Step 5: Interpret the Results
- Forward Bias:
- If the diode shows low resistance in forward bias, it indicates that the diode is allowing current to flow in one direction, as expected.
- Reverse Bias:
- If the diode shows high resistance in reverse bias, it indicates that the diode is blocking current in the opposite direction, as expected.
What to Conclude:
-
Good Diode:
- Low resistance (or specified voltage drop, typically 0.5-0.9 V) in forward bias.
- High resistance (or open circuit) in reverse bias.
-
Defective Diode:
- Shorted Diode:
- Shows low resistance in both forward and reverse directions.
- Open Diode:
- Shows high resistance (or infinite resistance) in both forward and reverse directions.
- Shorted Diode:
Final Answer:
To determine if a semiconductor diode is defective using an ohmmeter:
- Set the ohmmeter to resistance mode.
- Measure the forward resistance by connecting the positive probe to the anode and the negative probe to the cathode. Expect a low resistance value.
- Measure the reverse resistance by switching the probes. Expect a high resistance value.
- A good diode should show low resistance in forward bias and high resistance in reverse bias. A defective diode may show low resistance in both directions (shorted) or high resistance in both directions (open).
Using these steps, you can effectively determine whether a semiconductor diode is functional or defective.