Analysis of the composition of industrial automation (3), introduction of infrared sensors and magneto-optical effect sensors in industrial automation

Industrial automation is gradually developing, and the maturity of industrial automation represents the industrial level. For industrial automation, the editor has introduced it in the previous article. Friends who have read the previous article have more or less understanding of industrial automation. In order to further increase everyone’s understanding of industrial automation, this article will introduce infrared sensors and magneto-optical effect sensors for industrial automation.

Analysis of the composition of industrial automation (3), introduction of infrared sensors and magneto-optical effect sensors in industrial automation

1. Infrared sensor

The development of infrared technology has been well known to everyone, and this technology has been widely used in modern science and technology, national defense, industry and agriculture and other fields. Infrared sensing system is a measurement system using infrared as a medium, and can be divided into five categories according to functions:

(1) Radiometers for radiometric and spectral measurements;

(2) A search and tracking system for searching and tracking infrared targets, determining their spatial positions and tracking their movements;

(3) Thermal imaging system, which can generate a distribution image of infrared radiation of the entire target;

(4) Infrared ranging and communication systems;

(5) Hybrid system refers to a combination of two or more of the above types of systems.

Let’s first look at the composition of the infrared system, the main optical system and the auxiliary optical system, and on this basis, we will discuss the key components of the infrared in detail. In fact, the working principle of the infrared sensor is not complicated. The working principle of each part of a typical sensor system is as follows:

(1) The target on the side. The infrared system can be set according to the infrared radiation characteristics of the target.

(2) Atmospheric attenuation. When the infrared radiation of the target to be measured passes through the earth’s atmosphere, the infrared radiation emitted by the infrared source will be attenuated due to the scattering and absorption of gas molecules, various gases and various sol particles.

(3) Optical receiver. It receives part of the infrared radiation of the target and transmits it to the infrared sensor. It is equivalent to a radar antenna and is often used as an objective lens.

(4) Radiation modulator. It modulates the radiation from the target to be measured into alternating radiation light, provides target orientation information, and can filter out large-area interference signals. Also known as a modulation disc and a chopper, it has a variety of structures.

(5) Infrared detector. This is the heart of the infrared system. It is a sensor that detects infrared radiation by using the physical effect presented by the interaction between infrared radiation and matter. In most cases, it uses the electrical effect presented by this interaction. Such detectors can be divided into two types: photon detectors and thermally sensitive detectors.

(6) Detector cooler. Since some detectors must work at low temperature, the corresponding system must have refrigeration equipment. After cooling, the device can shorten the response time and improve the detection sensitivity.

(7) Signal processing system. The detected signals are amplified, filtered, and information is extracted from these signals. This information is then converted into the required format and sent to a control device or Display.

(8) Display equipment. This is a terminal device for infrared devices. Commonly used displays include oscilloscopes, picture tubes, infrared photosensitive materials, indicating instruments and recorders.

According to the above process, the infrared system can complete the measurement of the corresponding physical quantity. The core of the infrared system is the infrared detector. According to the different detection mechanisms, it can be divided into two categories: thermal detectors and photon detectors. The following takes the heat detector as an example to analyze the principle of the detector.

Thermal detectors use the radiant heat effect to cause the temperature of the detection element to rise after receiving radiant energy, which in turn changes the temperature-dependent performance of the detector. By detecting a change in one of these properties, radiation can be detected. Radiation is mostly detected by thermoelectric changes. When the element receives radiation and causes a physical change other than electricity, the corresponding change in electricity can be measured after appropriate transformation.

Infrared sensors have already played a huge role in modern production practices. With the improvement of detection equipment and other parts of technology, infrared sensors can have more performance and better sensitivity.

2. Magneto-optic effect sensor

Modern electrical measurement technology is becoming more and more mature. It has been widely used in the measurement of electrical and non-electrical quantities due to its high precision and easy connection with microcomputers to realize automatic real-time processing. However, the electrical measurement method is prone to interference. During AC measurement, the frequency response is not wide enough and there are certain requirements for withstand voltage and insulation. Today, with the rapid development of laser technology, the above problems have been solved.

The magneto-optical effect sensor is a high-performance sensor developed by using laser technology. Laser is another new technology developed rapidly in the early 1960s. Its appearance marks that people have entered a new stage in mastering and utilizing light waves. Due to the low monochromaticity of ordinary light sources in the past, many important applications were limited, and the emergence of lasers made radio technology and optical technology advance, penetrate and complement each other. Now, many sensors have been made by using laser, which solved many technical problems that could not be solved before, making it suitable for dangerous and flammable places such as coal mines, oil and natural gas storage.

For example, optical fiber sensors made of lasers can measure parameters of crude oil injection and cracking of large oil tanks. In the actual measurement site, there is no need for power supply, which is especially suitable for petrochemical equipment groups with strict requirements on safety and explosion-proof measures, and can also be used to implement optical telemetry chemical technology in certain links in large steel plants.

The principle of the magneto-optical effect sensor is mainly to use the polarization state of light to realize the function of the sensor. When a beam of polarized light passes through a medium, if there is an external magnetic field in the direction of beam propagation, the light will rotate an angle through the plane of polarization, which is the magneto-optical effect. That is, the applied magnetic field can be measured by the angle of rotation. Under a specific test device, the deflection angle is proportional to the output light intensity. By irradiating the laser diode LD with the output light, the digital light intensity can be obtained and used to measure a specific physical quantity.

Since the late 1960s, RC Lecraw’s research report on the magneto-optical effect has attracted everyone’s attention. Japan, the Soviet Union and other countries have carried out research, and domestic scholars have also carried out research. The magneto-optical effect sensor has the characteristics of excellent electrical insulation performance, anti-interference, wide frequency response, fast response, safety and explosion-proof, etc. Therefore, it has a unique effect on the measurement of electromagnetic parameters in some special occasions, especially in high-voltage and high-current power systems. In terms of measurement, it shows its potential advantages. At the same time, by developing the software and hardware of the processing system, the automatic real-time measurement of the welding machine and the robot control system can also be realized. In the use of magneto-optical effect sensors, the most important thing is to choose magneto-optical medium and laser. Different devices have different capabilities in terms of sensitivity and working range. With the emergence of high-performance lasers and new types of magneto-optical media in recent decades, magneto-optical effect sensors have become more and more powerful and their applications have become more and more extensive.

As a special-purpose sensor, magneto-optical effect sensor can play its own function in a specific environment, and it is also a very important industrial sensor.

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