Zener diode tester
Zener diode tester
The design of a simple Zener diode tester with a nominal value of 3.3… 18 V is described. The voltage drop on the zener diode being tested is indicated on the scale of the graduated potentiometer VR1. Using this tester, you can also determine the polarity of the zener diodes.
The power supply stage consists of transformer XI, rectifier diode D1, filter capacitor C1, resistor R1, transistor T1, zener diodes ZD1 and ZD2, providing approximately 20 V of constant stabilized voltage for the sensor stage. The sensor stage consists of resistors R2 and R3, potentiometer VR1, red LED1 and transistor T2.
The calibration of the potentiometer scale is done as follows. Having closed the red and black contacts, turn on the tester and, turning the potentiometer shaft clockwise (previously brought to the extreme left position), wait for the LED to light up. This will be *0* of the scale. The remaining sections of the scale are marked by testing zener diodes with known ratings.
The nominal value of an unknown zener diode is measured by reading the scale at the moment the LED lights up. When the zener diode is connected in reverse polarity, the LED shines brightly at any rotation of the potentiometer shaft.
