testing Zener Diodes
Zener diodes can be quickly tested for opens, shorts, or leakage with an ohmmeter. The ohmmeter is connected in forward and reverse bias in the same manner as with P–N junction diodes. However, these tests
do not provide information on whether the zener diode is regulating at the rated value. For that information, a regulation test must be performed with a metered power supply that can indicate both voltage and current.
Figure 30-5 shows the proper setup for a zener diode regulation test. The output of the power sup- ply is connected with a limiting resistor in series with a zener diode to be tested. A voltmeter is connected across the zener diode under test to monitor the zener voltage. The output voltage is slowly increased until the specified current is flowing through the zener diode. The current is then varied on either side of the specified zener current (IZ). If the voltage remains
constant, the zener diode is operating properly.
Questions
1. Describe the process for testing a zener diode with an ohmmeter.
2. What parameters are not tested when using an ohmmeter to test a zener diode?
3. Draw a schematic diagram showing how to connect a zener diode to check its breakdown voltage.
4. Describe how the circuit in question 3 operates to determine whether the zener diode is operat- ing properly.
How can the cathode end of a zener diode be determined using an ohmmeter?