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

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

  1. Connect the probes:
    • Connect the positive (red) probe to the anode and the negative (black) probe to the cathode.
  2. 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

  1. Switch the probes:
    • Now, connect the positive (red) probe to the cathode and the negative (black) probe to the anode.
  2. 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

  1. 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.
  2. 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.

Final Answer:

To determine if a semiconductor diode is defective using an ohmmeter:

  1. Set the ohmmeter to resistance mode.
  2. Measure the forward resistance by connecting the positive probe to the anode and the negative probe to the cathode. Expect a low resistance value.
  3. Measure the reverse resistance by switching the probes. Expect a high resistance value.
  4. 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.