Intelligent Sensor Analysis and Development Trend

　　As a tool for humans to obtain information, sensors are an important part of modern information technology. In the traditional sense, most of the sensors output are analog signals, and they do not have the function of intelligent signal processing. They need to be connected to a specific measuring instrument to complete the signal processing and transmission functions. Smart sensors can process raw data internally, and can exchange data with the outside world through standard interfaces, and change the work of sensors through software control according to actual needs, so as to achieve intelligence and networking. Due to the use of standard bus interface, the intelligent sensor has good openness and scalability, which brings a lot of development space to the expansion of the system.

　　What is a smart sensor?

　　Smart sensor is a new type of sensor that can detect and convert measured physical or chemical quantities, can learn, reason, judge and process signals, and has communication and management functions. Smart sensors have the ability to automatically zero, calibrate, compensate, and collect data. It is determined that the intelligent sensor has higher precision, resolution, stability and reliability, as well as better adaptability.

　　In the early smart sensor, the output signal of the sensor is processed and converted, and then sent to the microprocessor through the interface for calculation processing. In the 1980s, the intelligent sensor mainly took the microprocessor as the core, and integrated the sensor signal conditioning circuit, the microelectronic computer memory and the interface circuit into a single chip, so that the sensor had a certain artificial intelligence. In the 1990s, the intelligent measurement technology has been further improved, enabling the sensor to achieve miniaturization, structural integration, array type, digital type, easy to use, simple to operate, and has self-diagnosis function, memory and information processing function, data storage. function, multi-parameter measurement function, network communication function, logical thinking and judgment function.

　　Smart sensors can be roughly divided into three types: sensors with judgment ability; sensors with learning ability; sensors with creative ability.

　　The structure of the smart sensor

　　The intelligent sensor system is mainly composed of sensors, microprocessors and related circuits. The sensor converts the measured physical and chemical quantities into corresponding electrical signals, and sends them to the signal modulation circuit. After filtering, amplification, and A/D conversion, they are sent to the microprocessor. The microprocessor calculates and stores the received signals. After data analysis and processing, on the one hand, the sensor and the signal conditioning circuit are adjusted through the feedback loop to realize the adjustment and control of the measurement process; , Interface customization and output digital measurement results. The microprocessor is the core of the intelligent sensor, because the microprocessor gives full play to the functions of various software, makes the sensor intelligent, and greatly improves the performance of the sensor.

　　Key Features of Smart Sensors

　　The function of the smart sensor is proposed by simulating the coordinated actions of human senses and brain, combined with long-term research and practical experience of testing technology. It is a relatively independent intelligent unit. Its appearance reduces the harsh requirements of the original hardware performance, and relies on the help of software to greatly improve the performance of the sensor.

　　Smart sensors can often achieve the following functions:

　　1. Multi-signal conversion function

　　We observe natural phenomena around us. Common signals include sound, light, electricity, heat, force, and chemistry. Sensing components are generally measured in two ways: direct and indirect. The smart sensor usually has a compound conversion function, which can measure a variety of physical and chemical quantities at the same time, and can more comprehensively reflect the state of the measured object. For example, the composite liquid sensor developed by the University of California, USA, can simultaneously measure the temperature, flow rate, pressure and density of the medium.

　　2. Adaptive function

　　Intelligent sensors can automatically adjust product characteristics within a certain range to adapt to changes under changing conditions, and compensate for parameter drift caused by components. Adaptive technology can extend the life of smart sensor components and expand their field of work. Because the correction and compensation value of the smart sensor is no longer an average value, but the real correction value of the measurement point, the detection accuracy and accuracy of the sensor are actually improved.

　　3. Self-check, self-calibration and self-diagnosis functions

　　Traditional sensors require periodic inspection and calibration to ensure adequate accuracy during normal use. This requires the sensor to be disassembled from the field of use and sent to the laboratory or inspection department. The abnormality of the online measurement sensor cannot be diagnosed in time. With smart sensors, the sensor can perform a self-check, diagnostic test to determine if the component is faulty when the power is turned on. It can also be automatically corrected online by using the stored standard measurement characteristic data according to the usage time, which is convenient and quick.

　　4. Information storage function

　　Smart sensors can store a large amount of information for users to query at any time. This information can be the historical information left by the system hardware devices, for example, how many hours the sensor has worked, how many times the power supply has been replaced, etc.; it can also be sensor detection data or charts drawn by the system, and can also include serial numbers, production dates, catalogs, etc. table and final factory test results.

　　5. Data processing function

　　Process data processing is a very important task. Smart sensors can not only amplify the signal, but also digitize the signal, and then use software to realize the signal conditioning. For example, some smart sensors can linearize nonlinear signal output sensor data by querying historical data; most smart sensors can reduce the interference of noise or other related effects through digital filtering; environmental factor compensation is also a part of smart sensor data processing. important task. For example, the correct temperature compensation coefficient can be obtained by measuring the temperature of the basic detection element, so that the temperature compensation of the signal can be realized. Smart sensors make it easy for users to add, subtract, multiply, and divide multiple signals. In addition, smart sensors decentralize data processing operations from the central control room to the point of near signal generation, eliminating the cost of additional sensors and leads, and The negative effects (such as noise, potential difference, etc.) introduced by long-distance transmission are reduced, so that the signal is more accurate, the software in the main controller can also be simplified, and the speed of the control loop can be improved.

　　6. Configuration function

　　Configuration capabilities are another feature of smart sensors. For example, detection range, programmable on/off delay, group selection counter, normally open/normally closed, etc. Using the configuration function of the intelligent sensor can make the same type of sensor work in the best state, and can do different work in different occasions, and improve the adaptability of the sensor.

　　7. Digital communication function

　　Smart sensors generate a lot of information and data, so using a single wire from a normal sensor to transmit data would make the system very complex. Therefore it requires a flexible communication system. Smart sensors are often configured for digital serial communication with external connections. Because serial networks are much more resistant to environmental influences (such as electromagnetic interference) than ordinary analog signals. Patching serial communications to the device effectively manages the transfer of information so that data is output only when needed.

　　The high performance of smart sensors is not obtained by pursuing the precise design and continuous optimization of the sensor's own structure like traditional sensor technology, but by combining with microprocessors/microcomputers, using cheap integrated circuit technology, chips and powerful software. Therefore, it has a higher cost performance and is more practical on site.

　　The way to realize smart sensor

　　1. Non-integration

　　Non-integrated intelligent sensor is an intelligent sensor system composed of traditional basic sensor, signal conditioning circuit and microprocessor with digital bus interface as a whole. This kind of non-integrated intelligent sensor is developed rapidly under the impetus of the development of field bus control system. The original set of production process equipment of the automatic instrument manufacturer is basically unchanged. It is assembled with a microprocessor board with a digital bus interface, and is equipped with intelligent communication, control, self-calibration, self-compensation, self-diagnosis, etc. software to realize smart sensor functions. This is the cheapest and fastest way to achieve it.

　　2. Integration

　　The integrated intelligent sensor system adopts micromachining technology and large-scale integrated circuit technology to integrate sensitive components, signal conditioning circuits and microprocessor units on a single chip. The integrated technology realizes the purpose of miniaturization and structural integration of the intelligent sensor, and improves the detection accuracy and stability of the sensor.

　　3. Non-integration and integration mix

　　To realize the integration of intelligent sensor system on one chip, there are still many difficult problems in practical operation. According to needs, many smart sensors often integrate each integrated link of the system (such as sensitive unit, signal conditioning circuit, microprocessor unit, digital bus interface) on two or three chips in different combinations, and are assembled on In one housing, the sensor non-integration and integration are mixed.

　　Development Trend of Smart Sensor Technology

　　1. Focus on industrial control, automobile, communication, environmental protection, medical treatment, etc., and deepen the application development of intelligent sensor market.

　　2. Based on MEMS technology and relying on integrated, intelligent and networked technologies, strengthen the research and development of new smart sensors.

　　3. Accelerate the industrialization of intelligent sensor products with the main goal of increasing varieties, improving quality and improving economic benefits.