d4.jpg [25.72kb] d1.jpg [16.24kb] d2.jpg[43.59kb][img]/js/ckeditor/plugins/attach/attach_25.png [/img[d3.jpg[43.59kb[ I attach the images

Jean hello, according to the second photo it seems that it is written 4v, which is a known value, but if you really want to know exactly its value, you must connect a potentiometer of about 10K to a power source and give the pot at its ends the + and - about 10V will be enough, then the central leg of the pot is connected to a leg of the diode, the other to a probe of a milliammeter and the other probe is connected to one of the legs of the pot. In this way you make a voltage divider which slowly varying the value of the pot slowly you can see that the milliammeter begins to mark, now as I do not know what is the anode and the cathode of the diode because in the photos I do not see it clear, it can be that you make the variation of the pot and the milliammeter marks great value, then turn the diode and repeat the process, when the measurement that is controlled by the rotation of the pot begins, at that moment the zener starts to drive, what you have to do the disconnect the milliammeter, pass it to voltage measurement and measure between the central leg of the pot and the one that was connected the milliammeter, there you will read the working voltage of the zener and you will also know what the cathode and anode is.

Hi Jean, I leave 2 circuits for you to make your own zener meter, choose the one you like, they are really useful, since you rarely see the value of the zener.