ChineseAnalysis and development trend of intelligent sensors
As a tool for humans to obtain information, sensors are an important part of modern information technology. In the traditional sense, sensors mostly output analog signals, which do not have the function of intelligent signal processing. They need to be connected to specific measuring instruments to complete the signal processing and transmission functions. Intelligent sensors can process raw data internally, exchange data with the outside world through standard interfaces, and change the work of sensors through software control according to actual needs, thereby realizing intelligence and networking. Due to the use of standard bus interfaces, intelligent sensors have good openness and scalability, which brings great development space for system expansion.
What is an intelligent sensor?
Intelligent sensors are a new type of sensor that can detect and convert measured physical or chemical quantities, can learn, reason and judge processing signals, and have communication and management functions. Intelligent sensors have the ability to automatically zero, calibrate, compensate, and collect data. This determines that intelligent sensors have high accuracy, resolution, stability and reliability, as well as good adaptability.
Early intelligent sensors sent the output signals of sensors to microprocessors for calculation and processing after processing and conversion. In the 1980s, intelligent sensors were mainly based on microprocessors, integrating sensor signal conditioning circuits, microcomputer storage and interface circuits on a chip, giving the sensors a certain degree of artificial intelligence. In the 1990s, intelligent measurement technology was further improved, making sensors miniaturized, structurally integrated, array-based, digital, easy to use, and simple to operate. They also have self-diagnosis functions, memory and information processing functions, data storage functions, multi-parameter measurement functions, networking communication functions, logical thinking and judgment functions.
Intelligent sensors can be roughly divided into three types: sensors with judgment capabilities; sensors with learning capabilities; sensors with creative capabilities.
Structural composition of intelligent sensors
Intelligent sensor systems are mainly composed of sensors, microprocessors and related circuits. The sensor converts the measured physical and chemical quantities into corresponding electrical signals, sends them to the signal modulation circuit, and sends them to the microprocessor after filtering, amplification, and A/D conversion. After the microprocessor calculates, stores, and analyzes the received signals, it adjusts the sensor and the signal conditioning circuit through the feedback loop to achieve the regulation and control of the measurement process; on the other hand, it transmits the processed results to the output interface, and after being processed by the interface circuit, it outputs the digital measurement results according to the output format and interface customization. The microprocessor is the core of the intelligent sensor. Since the microprocessor gives full play to the functions of various software, the sensor is intelligent and the performance of the sensor is greatly improved.
Main functions of intelligent sensors
The function of intelligent sensors is proposed by simulating the coordinated actions of human senses and brains, combined with long-term research and practical experience in testing technology. It is a relatively independent intelligent unit. Its appearance has reduced the stringent requirements for the original hardware performance, and the performance of the sensor is greatly improved with the help of software.
Intelligent sensors can usually achieve the following functions:
1. Multi-signal conversion function
We observe the natural phenomena around us. Common signals include sound, light, electricity, heat, force, and chemistry. Sensitive element measurements are generally carried out in two ways: direct and indirect measurement. Smart sensors usually have a composite conversion function, which can measure multiple 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
Smart sensors can automatically adjust product characteristics within a certain range to adapt to changes in conditions and compensate for parameter drift caused by components. Adaptive technology can extend the life of smart sensor components and expand their working range. Because the correction and compensation values of smart sensors are no longer an average value, but the true correction value of the measurement point, the detection precision and accuracy of the sensor are actually improved.
3. Self-test, self-calibration, and self-diagnosis functions
Traditional sensors need to be inspected and calibrated regularly to ensure that they are accurate enough during normal use. This requires the sensor to be disassembled from the site of use and sent to the laboratory or inspection department for processing. If an abnormality occurs in the online measurement sensor, it cannot be diagnosed in time. When using smart sensors, the sensor can perform self-test and diagnostic tests when the power is turned on to determine whether the component is faulty. It can also automatically calibrate online according to the usage time using the stored standard metering characteristic data, which is convenient and fast.
4. Information storage function
Intelligent sensors can store a large amount of information for users to query at any time. This information can be historical information left by the system hardware device, such as 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, or it can include serial number, production date, catalog table and final factory test results.
5. Data processing function
Process data processing is a very important task. Intelligent sensors can not only amplify signals, but also digitize signals, and then use software to adjust signals. For example, some intelligent sensors can linearize nonlinear signal output sensor data by querying historical data; most intelligent sensors can reduce the interference of noise or other related effects through digital filtering functions; environmental factor compensation is also an important task of intelligent sensor data processing. For example, by measuring the temperature of the basic detection element, the correct temperature compensation coefficient can be obtained, so that the temperature compensation of the signal can be realized. Smart sensors make it easy for users to perform addition, subtraction, multiplication and division operations on multiple signals. In addition, smart sensors transfer data processing operations from the central control room to the point close to the signal generation point, eliminating the cost of additional sensors and leads, and reducing the negative effects introduced by long-distance transmission (such as noise, potential difference, etc.), thereby making the signal more accurate, simplifying the software in the main controller, and increasing the speed of the control loop.
6. Configuration function
Configuration function is another feature of smart sensors. For example, detection range, programmable on/off delay, group selection counter, normally open/normally closed, etc. The configuration function of smart sensors can make the same type of sensors work in the best state, and can perform different tasks in different occasions, improving the adaptability of sensors.
7. Digital communication function
Smart sensors generate a lot of information and data, so using a single connection of ordinary sensors to transmit data will make the system very complex. Therefore, it requires a flexible communication system. Smart sensors are often configured with digital serial communication connected to the outside. Because the ability of serial networks to resist environmental influences (such as electromagnetic interference) is much stronger than that of ordinary analog signals. Connecting serial communication to the device can effectively manage the transmission of information so that data is output only when needed.
The high performance of smart sensors is not achieved 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 processes, chips and powerful software, so it has a higher cost performance and is more practical on site.
Ways to implement smart sensors
1. Non-integration
Non-integrated smart sensors are smart sensor systems that combine traditional basic sensors, signal conditioning circuits, and microprocessors with digital bus interfaces into a whole. This type of non-integrated smart sensor has developed rapidly under the impetus of the development of fieldbus control systems. The original set of production process equipment of the automation instrument manufacturer remains basically unchanged, and is assembled with a microprocessor plug-in board with a digital bus interface, and is equipped with intelligent software that can perform communication, control, self-correction, self-compensation, self-diagnosis, etc., thereby realizing the functions of smart sensors. This is the most economical and fastest way to achieve it.
2. Integration
The integrated intelligent sensor system is composed of sensitive components, signal conditioning circuits and microprocessor units integrated on a chip using micromachining technology and large-scale integrated circuit technology. The integration technology realizes the miniaturization and structural integration of intelligent sensors, and improves the detection accuracy and stability of sensors.
3. Non-integration and integration hybrid
To realize the integration of intelligent sensor systems on a chip, there are still many thorny problems in actual operation. According to needs, many intelligent sensors often integrate various integrated links of the system (such as sensitive units, signal conditioning circuits, microprocessor units, digital bus interfaces) in different combinations on two or three chips, and assemble them in a shell to achieve non-integration and integration of sensors.
Development trend of intelligent sensor technology
1. Focus on industrial control, automobiles, communications, environmental protection, medical care and other key service areas to deepen the market application development of intelligent sensors.
2. Based on MEMS technology, relying on integration, intelligence and networking technology, strengthen the research and development of new intelligent sensors.
3. Accelerate the industrialization of smart sensor products with the main goals of increasing variety, improving quality and enhancing economic benefits.