Share 2 methods for testing laser diodes

　   1. Use special instruments to measure, which is simple, clear and accurate;

　　2. In the absence of instruments, a multimeter can be used to simply check the quality of the laser diode, but this detection method cannot measure the parameters of the diode. Before testing, first turn the multimeter's conversion switch to the RX1k position of the ohm range (be careful not to use the RX1 position to avoid excessive current burning the laser diode), then short-circuit the red and black test leads and perform ohm zero adjustment.

　　Forward characteristic test

　　Touch the black probe (positive pole inside the meter) of the multimeter to the positive pole of the diode, and the red probe (negative pole inside the meter) to the negative pole of the diode. If the needle does not swing to 0 but stops in the middle of the dial, the resistance value at this time is the forward resistance of the diode. Generally, the smaller the forward resistance, the better. If the forward resistance is 0, it means that the tube core is short-circuited and damaged. If the forward resistance is close to infinity, it means that the tube core is open-circuited. Short-circuited and open-circuited tubes cannot be used.

　　Reverse characteristic test

　　Touch the red probe of the multimeter to the positive pole of the diode and the black probe to the negative pole of the diode. If the needle points to infinity or close to infinity, the tube is qualified.

　　By using a multimeter to detect the forward and reverse resistance values, the electrodes of the diode can be identified and it can also be estimated whether the diode is damaged.

　　Polarity determination

　　Set the multimeter to the R×100 or R×1k position, connect the two test leads to the two electrodes of the diode respectively, and after measuring a result, swap the two meters and measure another result. In the two measurement results, one measured resistance value is larger (reverse resistance), and the other measured resistance value is smaller (forward resistance). In the measurement with smaller resistance value, the black test lead is connected to the positive electrode of the diode, and the red test lead is connected to the negative electrode of the diode.

　　Detection of unidirectional conductivity and judgment of quality

　　Generally, the forward resistance of a germanium diode is about 1kΩ, and the reverse resistance is about 300 kΩ. The resistance of a silicon diode is about 5 kΩ, and the reverse resistance is ∞ (infinity). The smaller the forward resistance, the better, and the larger the reverse resistance, the better. The greater the difference between the forward and reverse resistance values, the better the unidirectional conductivity of the diode. If the forward and reverse resistance values ​​of the diode are both close to 0 or the resistance value is small, it means that the diode has been short-circuited or leaked. If the forward and reverse resistance values ​​of the diode are both infinite, it means that the diode has been open-circuited and damaged.

　　As long as you master the above methods, laymen can also measure the quality of laser diodes!