1. Discrimination of positive and negative electrodes
From the appearance, the positive end of the metal-packed Zener diode body is planar, and the negative end has a semi-circular shape. One end of the plastically sealed diode body printed with a color mark is a negative electrode, and the other end is a positive electrode. For the Zener diode with unclear mark, the polarity can also be judged by a multimeter. The measurement method is the same as that of the ordinary diode. That is, using the multimeter R&TImes; 1k file, the two test leads are respectively connected to the two electrodes of the Zener diode, and one is measured. After the result, the two meter pens were measured. In the two measurement results, the resistance value is smaller, the black meter is connected to the positive pole of the Zener diode, and the red meter is connected to the cathode of the Zener diode.
If the positive and negative resistances of the Zener diode are measured to be small or infinite, the diode is broken or open circuit damaged.
2. Voltage measurement
With 0~30V continuously adjustable DC power supply, for the Zener diode below 13V, the output voltage of the regulated power supply can be adjusted to 15V, and the positive pole of the power supply is connected in series with a 1.5kΩ current limiting resistor. The negative pole is connected, the negative pole of the power supply is connected with the positive pole of the Zener diode, and then the multimeter is used to measure the voltage value across the Zener diode, and the measured reading is the steady voltage value of the Zener diode. If the regulation voltage of the Zener diode is higher than 15V, the regulated power supply should be adjusted to 20V or more.
Test power can also be supplied to Zener diodes with a megohmmeter below 1000V. the way is:
Connect the positive end of the megohmmeter to the negative pole of the Zener diode. After the negative end of the megohmmeter is connected to the positive pole of the Zener diode, shake the megohmmeter handle at a uniform speed as specified, and monitor the voltage across the Zener diode with a multimeter. The value (the voltage of the multimeter should be determined according to the magnitude of the stable voltage). When the indication voltage of the multimeter is stable, this voltage is the stable voltage of the Zener diode.
If the steady voltage value of the measured Zener diode is high or low, the diode is not stable.