# Diode Tester Circuit Diagrams

Parts Placement Layout Logic Probe, It is difficult to determine the polarity of a diode when its marking is already erased. The color ring at one end usually indicates the cathode lead. But if this color ring is erased, what are you going to do? This problem can be solved by using a multimeter. However, when one must test a large number of unmarked diodes, the multitester becomes uncomfortable to use. The best way is to build a tester circuit that is specially designed for testing diodes alone like the one featured here. This circuit not only determines the polarity of the diode but also tests whether the diode is open or short circuited.
 Diode Tester Circuit Diagrams

### Diode Tester Circuit

It is difficult to determine the polarity of a diode when its marking is already erased. The color ring at one end usually indicates the cathode lead.

But if this color ring is erased, what are you going to do? This problem can be solved by using a multimeter.

However, when one must test a large number of unmarked diodes, the multitester becomes uncomfortable to use.

The best way is to build a tester circuit that is specially designed for testing diodes alone like the one featured here.

This circuit not only determines the polarity of the diode but also tests whether the diode is open or short circuited.

The diode to be tested is connected to the terminals as shown. When the LED lights, the diode is connected correctly and the symbol shows the polarity.

To check whether the diode is shorted, reverse the diode and if the LED remains lighted, then the diode has an internal short circuit.

On the other hand when the LED does not light up in both directions, the diode is open.

The circuit can test both germanium and silicon diodes. The tester must be housed in a plastic box and the test electrodes must be marked with cathode(K) and anode (A) respectively.

A box with fixed contact points installed on it is highly practical in testing a large number of diodes. A suggested design is shown in Fig. 61.3.