With the chosen resistors in the circuit the current is approximately: 1mA, 2mA, 5mA, 10mA and 20mA. Great precision is not required.
If meter is chosen here for a small DVM module. However, every other meter is applicable, provided that the input resistance is high enough.
The circuit is simple to build on a piece of PCB holes. Note that the DVM module separate from the circuit galvanic isolated power supply needs.
Connect the test zener diode between the terminal A and K. Start with a current of 2mA. This is a safe value for most type zener diodes. Depending on the type of zener diode, may be chosen for a greater current. Than the Zener voltage will vary slightly.
Join the zener diode on backwards, the meter will indicate approximately 0.7V. The same picture shows an ordinary silicon diode. A germanium diode, a voltage of about 0.3 V to 0.4 V indicate when a Schottky approximately 0.2 V indicates.
Connect an LED to A and K, it will be highlighted and the Vforward (LED voltage) of the LED indicate.
The diode / LED failure, the meter displays zero if the voltage at the collector of Q1 is, this is> 25V.
Bridge rectifier BR1 = 40V 500mA
R1 = 3k3 ¼ W
R2 = 5K6 ¼ W
R3 = 2k7 ¼ W
R4 = 1k ¼ W
R5 = 560 ohm W ½
R6 = 270 ohm ½ W
C1 = 470µF 35V
D1 = 6V2 zener 400mW
Q1 = BC161-16
S1 = on / off switch
S2 = 5 modes 1 mom ignition switch
ENG = The diode under test (Device Under Test)
DVM DVM = module of BACO or Dick Best (input adapted to 200V)
Category: Test and Measurement