Ⅰ Introduction

The smart sensor or intelligent sensor is a high-tech that is developing rapidly. It is generally believed that smart sensors are sensors that can automatically collect, process, and self-diagnose and adapt to information from the outside world.

A good smart sensor is a package of sensors and instruments that driven by a and has functions such as communication and onboard diagnosis. Smart sensors can store various physical quantities detected and process the data according to instructions to create new data. Intelligent sensors can exchange information and can determine the data that should be transmitted, discard abnormal data, and complete analysis and statistical calculations.

Compared with traditional sensors, smart sensors generally have the following advantages: First, the accuracy of the sensor is improved. Secondly, the reliability of the sensor is improved. Third, the cost performance of the sensor is better. Finally, it contributed to the multi-functionalization of the sensor.

Ⅱ The intelligence of smart sensors

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

various kinds of sensors

Throughout the development process of smart sensors, it can be said that scholars in various periods have continuously deepened their understanding of the meaning of "smart" or "intelligence". The production process experienced early centralized control and later distributed control systems. To realize the needs of large-scale control systems with multi-point parameters, a field bus open control system (FCS) was bred out, which further developed the system and is a major change in the field of automation.

The future development of smart sensors is data fusion and miniaturization. Data fusion is the overall trend in science and technology. A complex network is formed by multiple types of sensors. The characteristics of each sensor in this network are exerted, and its complementarity is used to extend its life and improve its accuracy. The miniaturization of sensors is also a subject of great research focus. Its purpose is not only to make its parts smaller but also to make it more functional, to achieve the effect of simplifying and reducing the size.

The integrated smart sensor is an important standard for its future development. This is an important method for miniaturizing the volume. For example, a smart hygrometer can be added to a smart thermometer, and a small processor can also be equipped. In this way, it can not only monitor the required information but also use a tiny processor to give a timely solution. The multi-in-one smart sensor is more powerful and cost-effective.

Besides, the networking of smart sensors is also an important trend for future development. The smart network composed of multiple sensors can diagnose and correct the errors of a certain node by itself. Multiple sets of data measured by multiple sensors are undoubtedly more precise under the optimization algorithm. Just like the Internet, the communication between smart sensors through networked connections will be more convenient, and the processing of information will become faster. The application of bus technology is also one of the important development trends of smart sensors in the future. At the same time, the use of wireless connection technology makes the appearance and performance of smart sensors more concise and powerful. The problem of traditional sensors that are too bloated due to too many cables can be solved very well.

Ⅲ Functions of smart sensors

In summary, the main functions of smart sensors are:

(1) With self-calibration and self-correction functions;

(2) With automatic compensation function;

(3) It can automatically collect data and pre-process the data;

(4) It can automatically carry out inspection, self-select range, and self-finding fault;

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

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

(7) With judgment and decision processing functions.

The function of the smart sensor is proposed by simulating the coordinated movement of the human senses and brain, combined with the long-term research and practical experience of test technology. It is a relatively independent intelligent unit. Its appearance has reduced the harsh requirements of the original hardware performance, and the performance of the sensor can be greatly improved by software.

1. Information storage and transmission

With the rapid development of the smart distributed system, the intelligent unit is required to have a communication function, and the communication network is used for two-way communication in digital form, which is also one of the key signs of smart sensors. The smart sensor realizes various functions by transmitting test data or receiving instructions, such as gain setting, compensation parameter setting, internal inspection parameter setting, test data output, etc.

2. Self-compensation and calculation function

Engineers and technicians who have been engaged in sensor development for many years have been doing a lot of compensation for the temperature drift and output nonlinearity of the sensor, but they have not fundamentally solved the problem. The self-compensation and calculation functions of smart sensors have opened up new paths for sensor temperature drift and nonlinear compensation. In this way, lowering the requirements of sensor processing precision can also obtain more accurate measurement results, as long as the repeatability of the sensor can be ensured. A microprocessor is used to calculate the test signal through software, and multiple fitting and difference calculation methods are used to compensate for drift and nonlinearity.

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

Ordinary sensors need to be regularly checked and calibrated to ensure that they have sufficient accuracy. These tasks generally require the sensors to be disassembled from the use site to the laboratory or inspection department. It is impossible to diagnose the abnormality of the online measurement sensor in time. The situation with smart sensors is much different. First, the self-diagnosis function performs a self-check when the power is turned on, and a diagnostic test to determine whether the component is faulty. Secondly, it can be corrected online according to the usage time. The microprocessor uses the measurement characteristic data stored in the EPROM for comparison and proofreading.

4. Compound sensitive function

Common signals include sound, light, electricity, heat, force, chemistry, etc. Sensitive components are generally measured in two ways: direct and indirect. The smart sensor has a composite function, which can measure multiple physical and chemical quantities at the same time, giving information that can more comprehensively reflect the law of movement of substances. For example, the compound liquid sensor developed by the University of California in the United States 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 (velocity sensor), displacement (displacement sensor) of a certain point of the object, etc.

5. Integration of smart sensors

Because of the development of large-scale  sensors and corresponding circuits are integrated on the same chip, and such sensors with certain intelligent functions are called integrated smart sensors. It has three advantages: higher signal-to-noise ratio: the weak signal of the sensor is amplified by the signal and then transmitted over a long distance, which can greatly improve the signal-to-noise ratio. Improve performance: Since the sensor and the circuit are integrated on the same chip, the zero drift, temperature drift and zero position of the sensor can be automatically calibrated regularly by the self-calibration unit, and the frequency response of the sensor can be improved by using appropriate feedback methods. Signal normalization: The analog signal of the sensor is normalized by a program-controlled amplifier, and then converted into a digital signal by an analog to digital. The microprocessor normalizes the digital according to several forms of digital transmission, such as serial, parallel, frequency, phase, and pulse, etc.

Ⅳ Features of smart sensors

The intelligent sensor is a computer detection system with a microprocessor as the core and extended peripheral components. Compared with general sensors, intelligent sensors have the following significant features:

1. High accuracy

Smart sensors have information processing functions, which can modify various deterministic system errors (such as non-linear error of sensor input and output, service error, zero-point error, positive and negative formation error, etc.) through software, and can also properly compensate for random errors and reduce noise.

2. High reliability

The miniaturization of the integrated sensor system eliminates some unreliable factors of the traditional structure and improves the anti-interference function of the entire system. At the same time, it also has diagnostic, calibration, and data storage functions. There is also an adaptive function for the intelligent structure system.

3. High performance-price ratio

Under the requirement of the same accuracy, the performance-price ratio of the multi-function intelligent sensor is significantly improved compared with the single-function ordinary sensor, especially after the cheaper single-chip is adopted.

4. Multi-functional

Smart sensors contributed to the multi-functionalization of the sensor. The intelligent sensor can realize multi-sensor and multi-parameter comprehensive measurement, expand the measurement and use range through programming. According to the change of the detection object or condition, it can correspondingly change the range of the output data form. With the digital communication interface function, data can be directly sent to a remote computer for processing. Smart sensors have a variety of data output forms that are suitable for various application systems.

Ⅴ Development and applications

The rapid development and progress of the electronic automation industry have 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 achieved remarkable development. More and more counties are gradually taking steps in the field of smart sensors. Using military product lines and processes, smart sensors are obtained high accuracy, good stability, and low cost. At the same time, for the specific needs of users (such as networking measurement, custom communication protocol), secondary development can be carried out based on the original product with a short time cycle. It has been widely used in aviation, aerospace, petroleum, chemical, mining, machinery, dam, geology, hydrology, and other industries to measure the pressure, differential pressure, flow rate, height, and weight of various gases and fluids.

smart sensors in daily life

Smart sensors have been widely used in various fields such as aerospace, aviation, national defense, science and technology, and industrial and agricultural production. For example, it has broad application prospects in the field of robots. Intelligent sensors enable robots to have human-like facial features and brain functions, which can perceive various phenomena and complete various actions.

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

In the medical field, diabetics need to measure blood glucose levels to adjust their diet and inject insulin to prevent other complications. Normally, when measuring blood sugar, you need to pierce your finger, then put the blood sample on the glucose test paper, and finally put the test paper on the electronic blood glucose meter to measure. This is a troublesome and painful method. The "glucose watch" looks like an ordinary watch, and wearing it can achieve painless, bloodless, and continuous blood glucose testing. There is a pad coated with a reagent on the "glucose watch". When the pad comes into contact with the skin, glucose molecules will be adsorbed on the pad and react electrochemically with the reagent to generate an electric current. The sensor measures the current, calculates the blood glucose concentration corresponding to the current through the processor, and displays it in digital quantities.

Ⅵ To sum up

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

In the industrial field, traditional enterprises are faced with the problems of increasing labor costs and declining market demand. Traditional enterprises have begun to shift from labor-intensive to automation and intelligence. Throughout the transformation, smart sensors play a vital role in promoting the transformation and upgrading of traditional industries.

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