How to find out the anode & cathode of a diode using a multimeter?

Semiconductors & PN Junction Diode

• What is Conductor, insulator & semiconductor?
• What is Intrinsic Semiconductor?
• What is Extrinsic Semiconductor?
• Crystal Structure & Behavior of semiconductor
• Comparative Analysis of Energy Level Diagrams
• Construction of PN junction diode
• How to find out the anode & cathode of a diode using a multimeter?
• What is Forward & Reverse Biasing of PN Junction?
• Rectifier Circuits: HWR, FWR & BR

Introduction

Diodes are very cheap in cost, so it is a general thing that every electronic hobbyist has large number of diodes in his/her stock. When you pick up a diode from your stock, sometimes the cathode marking band on the body of diode, may be wiped out, so its difficult to find our the anode and cathode just by looking at it.

Also when you are troubleshooting an electronic circuit, like a TV, DVD player, etc., and if you doubt a particular diode in the circuit, then after de-soldering it, you need to check it for its go no-go condition. So to check the diode there are two procedures as discussed below.

Procedure to find out anode and cathode

1. Take a multimeter and put it in ohmmeter range.
2. RED probe is positive and BLACK probe is negative.
3. Connect two probes to two terminals of diode, AT RANDOM.
4. If the multimeter DOES NOT DEFLECT, reverse the probes connections.
5. Now if the multimeter deflects, the terminal connected to RED probe is anode.
6. And the terminal connected to BLACK probe is cathode.
7. Refer the following diagram for connections.

Procedure to check the diode for faulty or OK condition

1. Take a multimeter and put it in ohmmeter range.
2. Condition 1: Connect RED probe to anode, BLACK probe to cathode.
3. Note down the deflection of multimeter.
4. Condition 2: Now reverse the connections.
5. Note down the deflection of multimeter again.
6. The result of testing is as follows –
7. If multimeter deflects only in one condition, the diode is OK.
8. If the multimeter deflects in both conditions the diode is FAULTY.
9. If multimeter does not deflect in both conditions, the diode is FAULTY.
10. Refer the following diagram for connections.