Question

How would you identify the anode of an unmarked diode?

What is the significance, if any, of the reverse-to-forward resistance ratio of a diode?

How do you identify a germanium from a silicon diode?

Answer 1

We can identify the anode of an unmarked diode by using the diode tester of a standard multimeter. When the red lead is connected to the anode and the black lead connected to the cathode the meter will display the forward voltage of the diode otherwise it will display "OL".

The significance of the reverse-to-forward resistance ratio of a diode is to determine the comparison of resistance value of both forward and reverse diode . The more the resistance the lower the current, the lower the resistance the higher the current. When reverse bias, the resistance is high and it acts in open circuit and the reverse current is very small that can be neglected. When forward bias, the resistance is low and it acts as short circuit and the forward current is increasing as the voltage supply is higher.

In Europe, the convention is that Germanium diodes begin with the prefix A, and Si will be B.

(Z for zener)

If the diode is not marked, then there is no way to know other than testing Vf.

This marking convention only applies to Euro diodes, in the US the 1N designator is used and makes no distinctions.

So, its not possible to make the distinction just by looking.