You will need
  • Laboratory autotransformer (Latr), a resistor of 10 ohms, the rectifier voltage is 120 Volts, a multimeter.
Turn on the multimeter mode to check diodes. To do this, turn the handle to the position which is shown in the figure. Tap the insights of the Zener diode probes of the multimeter. Then reverse the probes and again touch their insights of the Zener diode. In one of the positions the multimeter should show a resistance of the Zener diode 300 – 600 Ohm, in a different position on the display should be the number 1 in the leftmost register (which means that the measured resistance of the device is infinitely large for the measurement range of the multimeter). In this case, the Zener diode is defective.
The Zener diode is faulty if multimeter in both cases, the measurement shows an infinite resistance (an internal open), very low resistance (breakout) or resistance of the order of 30 – 500 Ohm (polyprobe).
To verify Zener collect the following scheme: the mains plug of the rectifier 120 Volt plug to laboratory autotransformer. Controller laboratory autotransformer put in the position corresponding to the minimum voltage at its output. To the output terminals of the rectifier in series with the 10 kOhm resistor to connect the Zener diode (cathode to the positive terminal of the rectifier, in parallel with the Zener diode connect the multimeter included in the measure mode DC voltage in the range of 200 Volts.
Include laboratory autotransformer. Turn the knob to adjust the output voltage of the autotransformer, gradually increase the voltage of the Zener diode. At the same time follow the indications of the magnitude of the voltage on the display of the multimeter. The voltage must reach a certain size and stop growing. This value will be the voltage stabilization of Zener diode. If it is less than 20 Volts, set the multimeter in the measuring position of DC voltage in the range of 20 Volts. Consider the display of the multimeter more accurate indication of the voltage stabilization of the Zener diode.