The optocoupler is a relatively new type of electronic products. It is widely used in computers, audio and video. It is also called optocoupler or photo coupler. It is used in various control circuits. Because the light-emitting diodes and phototransistors in the photocoupler only change the voltage or current of the front and back stages of the circuit into the change of light, there is no electrical connection between them, so the potential connection between the circuits can be effectively cut off and the reliable isolation between the circuits can be realized.
1. The detection of optocoupler can judge the quality of optocoupler by measuring the internal resistance of diode and triode in circuit. More reliable detection methods are the following three. 1. Comparison method the suspected photocoupler is removed and its internal diode is measured with a multimeter. The positive and reverse resistance of the transistor is compared with the measured value of the corresponding foot of the good photocoupler. If the difference of the resistance is large, the photocoupler is damaged.
2. The detection method of digital multimeter the following is illustrated with the example of PCIll photocoupler detection. During the detection, the + terminal ① (foot) and - terminal ②(foot) of the photocoupler internal diode are inserted into the C and e jacks of the hfE of the digital multimeter respectively. At this time, the digital multimeter should be placed in the NPN block. Then the photocoupler is connected with the black pen of the phototransistor C pole ⑤(foot) of the pointer multimeter, and the e pole④ (foot) is connected with the red pen and then put the pointer multimeter in Rxlk block. In this way, the optocoupler can be judged by the deflection angle of the pointer of the pointer multimeter, which is actually the change of the photocurrent. The bigger the pointer deflects to the right, the higher the photoelectric conversion efficiency of the optocoupler, that is, the higher the transmission ratio. On the contrary, the situation is converse. If the needle does not move, the optocoupler has been damaged.
3. The photoelectric effect judgment method We still take the detection of ICIll optocoupler as an example. The multimeter is set in an inch:When it is in the Rxlk resistor block, two pens are connected to the output terminal ④、⑤ of the optocoupler respectively, and then a 1.5V battery is connected with a 50-100 ohm resistor in series. After the battery is connected with the ① foot of PC111 and the ② foot is connected to the negative pole, or the ① foot is connected to the positive extreme and the ② foot of the is connected to the negative extreme, we will observe the pointer deflection connected to the output multimeter at this time. If the pointer oscillates, the optocoupler is good. If it does not oscillate, the optocoupler is damaged. The bigger the pointer swing deflection angle of the multimeter is, the higher the photoelectric conversion sensitivity is.