Visual Identification of 1N4148 & 1N5231B

[liyin]

I was storing the parts of a circuit and couldn't tell which one is the 1N4148 diode and which is the Zener diode (5.1V).

 

[IanP]

If visual identification is impossible take a 9V battery (or a power supply), 1-10k resistor and a voltmeter, test both diodes in both directions and identify 5.1V diode that way ..
See: https://www.allaboutcircuits.com/vol_3/chpt_3/2.html

IanP

 

[liyin]

I tried a known Zener 5.1V diode with this circuit and got 4.5V consistently. Battery was providing 9.2V

 

[IanP]

I tried a known Zener 5.1V diode with this circuit and got 4.5V consistently

What resistor did you use?
It's possible that the resistor was to big and didn't allow sufficient current (at least 5mA) for test .. or, it was not 5.1 Zener ..

How to Use Zener Diodes
**broken link removed**

IanP

 

[liyin]

I used a 10KΩ metallic resistor (1/4W).

If anyone is guessing, the diode must be inverted in relation to the resistor/battery to read the rated voltage (5.1V).

 

[FvM]

I tried a known Zener 5.1V diode with this circuit and got 4.5V consistently.

That's O.K. Voltage is specified for 5 mA current and has a 5% tolerance, too.