How to Check a Zener Diode
- 1). Placing the multimeter on the diode setting. This is usually indicated by a small diode symbol on the casing.
- 2). Measure the forward-biased voltage on the Zener diode. Do this by putting the positive or red lead on the anode side of the diode, which is unmarked. Place the negative or black lead on the cathode side of the diode, which is marked by a stripe. A Zener is made from silicon, so an undamaged one will read 0.5 to 0.7 V when it is forward-biased.
- 3). Measure the reverse-biased voltage on the Zener diode by switching the multimeter probes. Place the positive lead on the marked or cathode side, and the negative lead on the unmarked or anode side. You should get a reading indicating infinite resistance or no current flow.
- 4). Attach the positive side of the 9-V battery to one side of the resistor and connect the other end of the resistor to the cathode side of the Zener diode, so that it will be reverse-biased. Then wire the remaining diode terminal to the negative side of the battery.
- 5). Place the multimeter on a DC voltage setting. Measure the voltage across the diode by placing a multimeter lead on each terminal. It should read approximately 5.6 volts, though the value may be as low as 5.32 or as high as 5.88 volts. Note that the voltage between the battery and ground remains at 9 V.
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