Brief introduction of photoelectric sensor
Photoelectric sensor is a kind of sensor using photoelectric element as detection element. It first converts the measured change into the change of optical signal, and then further converts the optical signal into electrical signal with the help of photoelectric elements.
Photoelectric sensor is generally composed of processing path and processing element. Its basic principle is to convert the measured change into the change of the optical signal based on the photoelectric effect, and then further convert the non electric signal into the electric signal with the help of the photoelectric element. Photoelectric effect refers to irradiating an object with light, which can be regarded as a series of photons with a certain energy bombarding on the object. At this time, the photon energy is transferred to the electron, and all the energy of a photon is absorbed by an electron at one time. After the electron gets the energy transferred by the photon, its state will change, so that the object irradiated by light will produce corresponding effect The electric effect of the electric field.
Structure of photoelectric sensor
Photoelectric sensor is mainly composed of transmitter, receiver and detection circuit, and sometimes includes transmitting plate and optical fiber. Among them, the transmitter is the light source (such as light emitting diode, laser diode, infrared emitting diode, etc.) to provide light; the receiver is composed of photodiode, photoelectric triode and photocell to receive the beam emitted by the transmitter and convert it into electrical signal; The detection circuit is used to detect the electrical signal output by the receiver, filter out the effective signal and filter out the interference signal.
Working principle of photoelectric sensor
Photoelectric sensor is controlled by converting the change of light intensity into the change of electrical signal. Firstly, the transmitter aims at the target and continuously emits the beam; secondly, the receiver receives the beam from the transmitter and converts it into an electrical signal; finally, the detection circuit detects the output electrical signal of the receiver and only retains the effective signal.
Characteristics of photoelectric sensor
① Long detection distance
If the detection distance of more than 10 m is reserved in the opposite type, it can realize that other detection methods (magnetic, ultrasonic, etc.) can not detect remotely.
② Less restrictions on the detection of objects
Due to the detection principle of shading and reflection caused by the detection object, it can detect almost all objects such as glass, plastic, wood, liquid and so on, unlike proximity sensors, which limit the detection object to metal.
③ Short response time
The light itself is high speed, and the circuit of the sensor is composed of electronic parts, so the mechanical working time is not included, and the response time is very short.
④ High resolution
High resolution can be achieved by using advanced design technology to focus the projecting beam on small light spots, or by forming a special light receiving optical system. It can also detect small objects and high-precision position detection.
⑤ It can realize non-contact detection
It can realize the detection without mechanical contact with the detection object, so it will not cause damage to the detection object and the sensor. Therefore, the sensor can be used for a long time.
⑥ Color discrimination can be realized
The reflectivity and absorptivity of the light formed by detecting the object are different according to the wavelength of the light to be projected and the color combination of the detected object. Using this property, the color of the detected object can be detected.
⑦ Easy to adjust
In the type of projecting visible light, the projecting beam is visible to the eye, which is convenient to adjust the position of the detected object.
Application case of photoelectric sensor
Photoelectric detection method has the advantages of high precision, fast response, non-contact and so on. The structure of the sensor is simple. In recent years, with the development of photoelectric technology, photoelectric sensor has become a series of products, its variety and output are also increasing, and is widely used in a variety of light industry automation. Typical cases are as follows:
1. Application of photoelectric sensor in high voltage and high current test
In recent years, the use of optical equipment for high-voltage and large current measurement is developing rapidly in power system. Many new photoelectric sensor systems have been put into operation one after another, which brings many convenient conditions for high-voltage and large current monitoring. OCT has fast response speed and high measurement accuracy. OCT is different from CT. The basic point of OCT is that the signal power is small. OCT products use light to modulate the measured current in the process of converting from high potential to low potential. The optical instrument part only has micro watt level power, while the secondary coil of CT needs watt level power.
2. Application of photoelectric sensor in speed measurement system
Today, with the rapid development of mechanical automation, speed is an important characteristic parameter in the dynamic mechanical performance test, and its size and change are related to whether the mechanical operation is normal. Many characteristic parameters of power machinery are often determined by the speed, such as the output power of motor, and the vibration of power machinery, the pulsation of air flow in pipes and the wear state of various working parts are also closely related to the speed. Monitoring the change of speed in time can eliminate many faults in machine operation and avoid more losses.
3. Application of photoelectric sensor in relay protection
With the development of the power industry, the transmission capacity and voltage level of the power system are constantly improving. There are many shortcomings in the traditional transformer to measure and monitor the power grid. At present, the integrated automation system of optical fiber power generation and substation composed of optical fiber transformer and optical fiber communication network with photoelectric sensors has become one of the most promising development directions of power automation technology. Power transformer is an important electric quantity measurement equipment in power system, and it is also the key equipment to realize power automation.