The Method of Judging the Quality of Optocoupler

The Method of Judging the Quality of Optocoupler

The optocoupler is an electro-optic-electro converter which transmits electric signal through optical medium. It uses light as a medium to convert electrical signals at the input end into optical signals, and then couples them to the output end and converts them into electrical signals.


The Method of Judging the Quality of Optocoupler

To judge the quality of the analog optocoupler, the forward and reverse resistance of the internal diode and triode can be measured. More reliable detection methods are the following three:


1. Comparing mehod: Remove the photocoupler which may have problems and measure its internal diode with a multimeter; then compare the normal positive and reverse resistance of the transistor with the measured value of the corresponding foot of the good photocoupler. If the resistance difference is large, the photocoupler is damaged.

2. Digital Multimeter Detection Method: The following is using an example of PCIll photocoupler detection to illustrate the method of digital multimeter detection. During detection, the + terminal ① foot and - terminal ② foot of the photocoupler inner diode are inserted into the c and e jacks of hfE of the digital multimeter respectively. At this time, the digital multimeter should be placed in the NPN block; then, the black pen of the pointer multimeter is connected with the C pole ⑤ foot of the photoelectric transistor, and the red pen is connected with the e pole ④ foot, and the pointer multimeter is set in the 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 reverse. If the needle does not move, the optocoupler has been damaged.


3. Photoelectric effect judgment method: We will still take the detection of ICIll photoelectric coupler as an example, and the multimeter is placed in Rxlk resistance block, and the two pens are connected to the output terminal ④、⑤ of the photocoupler respectively. After connecting a 1.5V battery in series with a resistance of 50-100 ohms, the positive terminal of the battery connects with the ① leg of PC111, and the negative terminal with the ② foot, or the positive terminal with the ② foot and the negative terminal with the ① foot. Then  we observe the pointer deflection in output multimeter. 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.


Prospects of Optocoupler  

Photocouplers are widely used in many electronic devices. With the rapid development of digital communication technology and the expanding application of automatic control components such as optical isolators and solid relays in the mechanical industry, especially the application and promotion of microprocessors in various fields and the gradual improvement of product performance, the application market of optocouplers will expand day by day. At the same time, its social benefits and economic benefits will be increased. The economic benefits will also be remarkable. In the future, the optocoupler will develop in the direction of high speed, high performance, small size and light weight.

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