Photoelectric sensor is controlled by converting the change of light intensity into the change of electrical signal. Generally, it consists of three parts:  Transmitter, receiver and detection circuit (that is, infrared transmitting circuit, infrared receiving circuit, signal amplification and processing circuit and signal output circuit), it is the use of detected objects to block or reflect the light beam, by the synchronous circuit power selection, so as to detect the object.  Objects are not limited to metal; anything that reflects light can be detected.  Photoelectric detection method has the advantages of high precision, fast response, non-contact, and more measurable parameters, simple structure, flexible and diverse forms.  

    Because the object is in the process of textile processing all kinds of fiber or yarn, they are a kind of flexible objects, easy to deformation after affected by external force, therefore, to detect the change of some parameters in the process of machining, using non-contact sensor normally, the test results will exist errors due to the contact, and photoelectric sensor is a contact,  It does not change the original state of yarn, but converts the non-electric quantity such as yarn and yarn defects into the change of electric quantity, so as to realize the detection of these non-electric quantity.  Photoelectric sensors are widely used in the detection of broken yarn because of their non-contact characteristics.  In use, for example, photoelectric sensors can smoothly pick up the signal at the moment when a broken yarn falls, and then the control system can process it.  This is because the photoelectric sensor can not change the original rotary table of the yarn, coupled with precision machining technology, microscopic technology, information processing technology, which can realize to contain cotton fiber, spinning, weaving, printing and dyeing and finishing of online monitoring, testing, and in the subsequent textile production of each link of the test, the textile products to effectively control and improve quality. 

    The application of photoelectric sensor in other process of textile industry, for example, judging yarn break automatic stop device by the shade degree of yarn;  Using the principle of light projection, yarn hairiness and defects can be detected.  Using light to reflect different colors and different absorption procedures, has designed a different fabric map for photoelectric scanning, photoelectric pieces receive this signal through the implementation of the implementation of woven or knitted projects in photoelectric jacquard.  

    In the process of textile production, photoelectric sensors are mainly used for speed measurement, yarn defect removal, yarn hairiness detection and fabric inspection in the weaving process, printing and dyeing process control and product inspection, weft detection and jacquard and so on.  In a word, as a non - contact measurement sensor, the application of photoelectric sensor in textile should not be underestimated.