On 11/24/2012 9:42 PM, KenO wrote:
Franc,


A second test you can do to check to see whether a zener diode is defective or not is to measure its voltage with a voltmeter of a multimeter (or simply just a voltmeter if you have one.)

In order for this test to work, we must feed voltage to the zener diode in reverse bias in series with a resistor. The voltage must be higher than the rated zener voltage of the zener diode. In the circuit below, we feed the zener diode and a 1K„¦ resistor 9 volts from a 9-volt battery. The zener diode is rated for 5.1V, well below the 9 volts, so the test will work wtih this diode. When measuring the voltage across the zener diode, it must measure a voltage near its rated zener voltage.

Zener Diode Voltage Test

If a zener diode reads a voltage near its rated zener voltage, VZ, then it is good.
Open Diode

If the diode reads a much higher voltage, of or near the voltage of the supply voltage feeding it, it is open and, thus, defective. It should be replaced.
Shorted Diode

If the diode is reading a much lower voltage than its rated voltage, such as near 0V, it is shorted internally and, thus, is defective and must be replaced."

What do you think?

Explane the readings when you connect the zener in reverse.

Wat are the readings when you use 9v AC instead of DC.