Zener DiodeTest Diagrams

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Zener Diode Test

If you want check a zener diode is whether  it's good or defective , there are two simple but effective  quick

you can do.

Test a Zener Diode with an Ohmmeter of a Multimeter

A very good test you can do is to check a zener diode with your  multimeter  set to the setting 

This is a simple test we can do is to check whether is good , opne or shorted.

So we take the ohmmeter and place it across the leads of the diode, the orientation is very important.

Anode -Cathode Diode  Resistance TEST 

We first take the ohmmeter and place the positive probe on the anode of the diode , the diode 

and the negative probe on the cathode of the diode the diode should read a moderately low 

resistance, maybe a few hundred thousand of ohms .

Cathode-Anode Diode Resistance  Test

Now take the ohmmeter and switch the probes around so that the probe of the multimeter  is now on the 

cathode of the diode and the negative lead on the anode. In this the diode should read a much higher resistance , well over 1MΩ. 

A typical reading may for example , be 2.3MΩ. The multimeter may even indicate 'OL' for an open circuit,

since the resistance is so high.

If you read a moderately low resistance with the zener diode one way and a high resistance with the leads 

the other, this is sign that the zener diode is good. A zener diode should read relatively low resistance in the 

forward biased direction and very high resistance in the reverse biased direction.

Open Diode

If a zener diode reads low resistance in both directions, this is a sign that the diode is open. A diode should not measure very high resistance in the forward biased direction.The diode should be replaced in the circuit.

Shorted Diode

If the zener diode reads low resistance in the both direction, this is a sign that the diode is shorte. A diode should not measure low resistance in the reverse biased direction. The diode should be replaced in the circurit.