As basic information of bidirectional diac has been mentioned before, today Huixin will introduce the testing methods of this kind of diode to you.

　　Adjust the multimeter to R×1k or R×10k in order to test the forward and reverse resistance of the bidirectional diac. Generally speaking, the result should be infinite, however, when the number of testing result is small or is zero, then the diodeis damaged.

　　Testing of snapback voltage

　　There are three ways to measure the snapback voltage of bidirectional diac:

　　1. Connect the E pole and L pole of the megger to both electrodes of bidirectional diac so that the meeger could provide breakdown voltage. Meanwhile adjust the multimeter to DC voltage to measure the figure of voltage, then switch the two electrodes of bidirectional diac and test again. Compare the deviation of the two times testing (the deviation shall be 3~6V in general) and the smaller the deviation is, the better performance of the diode will be.

　　2. Use multimeter to measure the AC voltage U then connect the bidirectional diac to the AC voltage of multimeter to test the loop and write down the voltage figure U1. Switch the electrodes to connect the AC voltage of multimeter once more and write down the figure U2. If the voltage figures of U1 and U2 is the same but differs from U, then that indicates the bidirectional diac performs well in conduction symmetry; if there is a large difference between U1 and U2, that means the diode is not in conduction symmetry; if U1 and U2 equal to U, that is to say the diode is damaged inside by short circuit; if the voltage figures of both U1 and U2 are 0V, the diode is damaged inside by open circuit.

　　3. Connect the anode of a 0~50V continuously adjustable DC power supply to a 20kΩ resistor and also one electrode of the diode, then connect the cathode of the power supply to the multimeter which is adjusted to 1mA current mode and another electrode of the diode. Turn up the voltage gradually and when the needle of multimeter swings from ten to one hundred μA, that means this bidirectional diac is on-state. The voltage figure of the power supply at this moment is called the snapback voltage of the diode.

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