Detection of Bidirectional Trigger Diode

1. Measurement of forward and reverse resistance Use a multimeter with R×1k or R×10k to measure the forward and reverse resistance of a bidirectional trigger diode. Under normal circumstances, its forward and reverse resistance values ​​should be infinite. If the measured forward and reverse resistance values ​​are very small or 0, it means that the diode has been broken down and damaged.
2. Measuring the breakover voltage There are three ways to measure the breakover voltage of a bidirectional trigger diode.
The first method is to connect the positive pole (E) and negative pole (L) of the megohmmeter to the two ends of the bidirectional trigger diode, use the megohmmeter to provide the breakdown voltage, and use the DC voltage range of the multimeter to measure the voltage value. After swapping the two poles of the bidirectional trigger diode, measure it again. Compare the deviation of the voltage values ​​measured twice (usually 3~6V). The smaller the deviation, the better the performance of the diode.
The second method is: first use a multimeter to measure the mains voltage U, then connect the bidirectional trigger diode to be tested in series into the AC voltage measurement circuit of the multimeter, connect the mains voltage, read the voltage value U1, and then swap the two poles of the bidirectional trigger diode and read the voltage value U2.
If the voltage values ​​of U1 and U2 are the same, but different from the voltage value of U, it means that the conduction performance of the bidirectional trigger diode is symmetrical. If the voltage values ​​of U1 and U2 differ greatly, it means that the conductivity of the bidirectional trigger diode is asymmetrical. If the voltage values ​​of U1 and U2 are the same as the mains U, it means that the bidirectional trigger diode is short-circuited and damaged. If the voltage values ​​of U1 and U2 are both 0V, it means that the bidirectional trigger diode is open-circuited and damaged.
The third method is: use a 0~50V continuously adjustable DC power supply, connect the positive pole of the power supply in series with a 20kΩ resistor and then connect it to one end of the bidirectional trigger diode, connect the negative pole of the power supply in series with the current range of the multimeter (set it to 1mA) and then connect it to the other end of the bidirectional trigger diode. Gradually increase the power supply voltage. When the ammeter pointer swings significantly (more than tens of microamperes), it means that the bidirectional trigger diode is turned on. At this time, the voltage value of the power supply is the breakover voltage of the bidirectional trigger diode.
Figure 4-73 is a method for detecting the breakover voltage of a bidirectional trigger diode.