I. Introduction

Smart sensors, or smart sensors, are a rapidly developing technology. It is widely believed that smart sensors are sensors that can automatically collect, process, self-diagnose and adapt to external information.


A good smart sensor is a set of sensors and instruments driven by A, with functions such as communication and on-board diagnostics. Smart sensors can store the various physical quantities detected and process the data according to instructions for creating new data. Smart sensors can exchange information, can determine what data should be transmitted, discard abnormal data, and complete analysis and statistical calculations.

Compared with traditional sensors, smart sensors usually have the following advantages: First, improve the accuracy of the sensor. Secondly, the reliability of the sensor is improved. Third, the sensor is more cost-effective. Finally, it contributes to the multi-function of the sensor.


Second, the intelligence of smart sensors

One of the biggest advances in automation has been the development and widespread use of smart sensors. But what exactly is a "smart" sensor?



Various sensors

Throughout the development process of smart sensors, it can be said that scholars of various periods have deepened their understanding of the meaning of "intelligent" or "intelligent". The production process underwent early centralized control and later distributed control

One. In order to meet the needs of large control systems with multi-point parameters, a fieldbus open control system (FCS) has been developed, which further develops the system and is a major revolution in the field of automation.


The future development of smart sensors is data fusion and miniaturization. Data fusion is the general trend of science and technology. A complex network is formed by many types of sensors. Taking advantage of the characteristics of each sensor in this network, use its complementarity to extend its life and improve its accuracy. The miniaturization of sensors is also a research hotspot. Its purpose is not only to make its parts smaller, but also to make them more functional, in order to achieve the effect of simplification and reduction of size.


Integrated smart sensors are an important standard for its future development. This is an important way to minimize the volume. For example, a smart thermometer can be added with a smart hygrometer and can also be equipped with a small processor. In this way, it can not only monitor the required information, but also provide solutions in a timely manner using microprocessors. Multi-functional integrated smart sensor more powerful, more cost-effective.


In addition, the networking of smart sensors is also an important trend for future development. An intelligent network of multiple sensors can diagnose and correct errors at a particular node on its own. Under the optimization algorithm, multiple sets of data measured by multiple sensors are undoubtedly more accurate. Just like the Internet, communication between smart sensors via network connections will become more convenient, and information processing will become faster. The application of bus technology is also one of the important development trends of future smart sensors. At the same time, the use of wireless connectivity technology makes the appearance and performance of smart sensors more concise and powerful. The problem of excessive expansion of traditional sensors due to too many cables can be solved well.


Third, the function of smart sensors

In short, the main functions of smart sensors are:

(1) With self-calibration and self-calibration function;

(2) with automatic compensation function;

(3) It can automatically collect data and preprocess the data;

(4) can automatically detect, self-select the range, self-find the fault;

(5) with data storage, memory and information processing functions;

(6) two-way communication, standardized digital output or symbol output function;

(7) With judgment and decision processing functions.

The function of smart sensors is proposed by simulating the coordinated movement 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 on the performance of the original hardware, and the software can greatly improve the performance of the sensor.


1. Information storage and transmission

With the rapid development of intelligent distributed systems, intelligent units are required to have communication functions, and communication networks are used for two-way communication in digital form, which is also one of the key signs of intelligent sensors. Smart sensors transmit test data or receive instructions to achieve various functions, such as gain setting, compensation parameter setting, internal check parameter setting, test data output, etc.


2. Self-compensation and calculation function

Engineers and technicians who have been working on sensors for years have been heavily compensating for the temperature drift and output nonlinearity of sensors, but they have not fundamentally solved the problem. The self-compensation and calculation functions of smart sensors open up a new way for temperature drift and nonlinear compensation of sensors. In this way, as long as the repeatability of the sensor can be ensured, the requirements for the processing accuracy of the sensor can be reduced and more accurate measurement results can be obtained. A microprocessor is used to calculate the test signal through software, and a variety of fitting and difference calculation methods are used to compensate for drift and nonlinearity.


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

Regular sensors need to be checked and calibrated regularly to ensure they have adequate accuracy. These tasks often require the sensor to be disassembled from the field of use to the laboratory or inspection department. The anomaly of the on-line measurement sensor cannot be diagnosed in time. The situation with smart sensors is very different. First, the self-diagnostic function self-checks when the power is turned on and performs diagnostic tests to determine if the component is faulty. Secondly, it can be corrected online according to the time of use. The microprocessor uses the measurement characteristic data stored in the EPROM for comparison and proofreading.


4. Composite sensitive function

Common signals include sound, light, electricity, heat, force, chemistry, etc. Sensitive components are usually measured in two ways: direct and indirect. Smart sensors have composite functions that can simultaneously measure a variety of physical and chemical quantities, providing information that more fully reflects the laws of material motion. For example, the composite liquid sensor developed by the University of California can simultaneously measure the temperature, flow rate, pressure and density of the medium. The composite mechanical sensor can simultaneously measure the three-dimensional vibration acceleration (acceleration sensor), speed (speed sensor), displacement (displacement sensor) and so on at a certain point of the object.


5. Integration of smart sensors

Due to the development of large-scale sensors, the corresponding circuit is integrated on the same chip, and the sensor with certain intelligent functions is called the integrated intelligent sensor. It has three advantages: a higher signal-to-noise ratio: the weak signal of the sensor is amplified by the signal and then transmitted over long distances, which can greatly improve the signal-to-noise ratio. Improved performance: Since the sensor and circuit are integrated on the same chip, the self-calibration unit can automatically calibrate the sensor's zero drift, temperature drift and zero position on a regular basis, and improve the sensor's frequency response by using appropriate feedback methods. Signal normalization: The analog signal of the sensor is normalized by a programmed amplifier and then converted to a digital signal by an analog-to-digital converter. The microprocessor normalizes the numbers according to several forms of digital transmission such as serial, parallel, frequency, phase and pulse.


Fourth, the characteristics of smart sensors

Intelligent sensor is a kind of computer detection system with microprocessor as the core and extended peripheral components. Compared with ordinary sensors, smart sensors have the following significant characteristics:


1. High precision

The intelligent sensor has information processing function, which can modify various deterministic system errors (such as nonlinear errors of sensor input and output, service errors, zero error, positive and negative formation errors, etc.) through software, and can also properly compensate random errors and reduce noise.


2. High reliability

The miniaturization of the integrated sensor system eliminates some unreliability factors of the traditional structure and improves the anti-interference function of the whole system. It also has diagnostic, calibration and data storage functions. The intelligent structure system also has an adaptive function.


3. High cost performance

Under the same accuracy requirements, the cost performance of multi-functional smart sensors has been significantly improved compared with single-function ordinary sensors, especially after the adoption of cheaper single-chip computers.


4. Multi-functional

Intelligent sensors have contributed to the multi-function of sensors. The intelligent sensor can realize the comprehensive measurement of multi-sensor and multi-parameter through programming, and expand the range of measurement and use. The range of output data forms can be changed accordingly according to changes in the detected object or condition. With the function of digital communication interface, the data can be directly sent to the remote computer for processing. Intelligent sensors have a variety of data output forms, suitable for various application systems.


5. Development and application

The rapid development and progress of the electronic automation industry has prompted sensor technology, especially integrated smart sensor technology, to become more and more active. With the rapid development of technology, some well-known companies and universities are vigorously carrying out the development of integrated smart sensors. Some well-known universities, research institutes and companies have also actively followed up, and the integrated smart sensor technology has made significant development. More and more countries are taking steps in the field of smart sensors. Using military product lines and processes, intelligent sensors with high precision, good stability and low cost are obtained. At the same time, for the specific needs of users (such as network measurement, custom communication protocols), it can be developed on the basis of the original product, and the time cycle is short. It has been widely used in aviation, aerospace, petroleum, chemical, mining, machinery, dam, geology, hydrology and other industries, for measuring the pressure, differential pressure, flow rate, height and weight of various gases and fluids.




Smart sensors in everyday life

Intelligent sensors have been widely used in aerospace, aviation, national defense, science and technology, industrial and agricultural production and other fields. For example, it has a wide range of applications in the field of robotics. Smart sensors enable robots with human-like facial features and brain functions that can sense various phenomena and complete various actions.


In industrial production, traditional sensors cannot quickly and directly measure and control certain product quality indicators (such as viscosity, hardness, surface finish, composition, color, and taste). However, smart sensors can directly measure certain quantities in the production process (such as temperature, pressure, flow, etc.), which have a functional relationship with product quality indicators, and use mathematical models established by neural network or expert system technology to calculate and infer the quality of the product.


In the medical field, people with diabetes need to measure their blood sugar levels to adjust their diet and inject insulin to prevent other complications. Usually, to measure blood sugar, you need to Pierce your finger, then place the blood sample on a blood glucose test strip, and finally place the test strip on an electronic blood glucose meter for measurement. This is a troublesome and painful method. The "blood glucose meter" looks like an ordinary watch and can be worn to achieve painless, bloodless and continuous blood glucose monitoring. The "glucose watch" has a pad coated with reagents. When the mat is in contact with the skin, the glucose molecules are adsorbed on the mat and react electrochemically with the reagent to generate an electric current. The sensor measures the current, the processor calculates the blood sugar concentration corresponding to the current, and displays it as a digital quantity.


Vi. Summary

As a wide-range system front-end sensing device, smart sensors can not only promote the upgrading of traditional industries, such as the renewal of traditional industries and the intelligent upgrading of traditional home appliances, but also promote innovative applications such as robotics, VR/AR, drones, smart home, smart medical and elderly care.


In the industrial sector, traditional enterprises are facing the problem of rising labor costs and declining market demand. Traditional enterprises have begun to shift from labor-intensive to automation and intelligence. In the entire transformation process, smart sensors play a vital role in promoting the transformation and upgrading of traditional industries.


Smart sensing technology is a leading technology for smart manufacturing and the Internet of Things. As a front-end sensing tool, it has very important significance