Abstract: This paper introduces the working principle and basic components of intelligent instruments, briefly describes their main functions and development, and discusses their future development trends. Keywords: Intelligent instrument, transmitter, microprocessor. The emergence of intelligent instruments has greatly expanded the application scope of traditional instruments. With their advantages of small size, powerful functions, and low power consumption, intelligent instruments have been rapidly and widely used in home appliances, research institutions, and industrial enterprises. 1. Working Principle of Intelligent Instruments The sensor picks up the information of the measured parameter and converts it into an electrical signal. After filtering to remove interference, the signal is sent to a multiplexer analog switch. The microcontroller selects each input channel of the analog switch and sends the signal to a programmable gain amplifier one by one. The amplified signal is converted into a corresponding pulse signal by an A/D converter and then sent to the microcontroller. The microcontroller performs corresponding data calculations and processing (such as nonlinear correction) according to the initial value set by the instrument. The calculation result is converted into corresponding data for display and printing. At the same time, the microcontroller compares the calculation result with the set parameters stored in the on-chip FlashROM (flash memory) or E2PROM (electrically erasable memory), and outputs corresponding control signals (such as alarm device triggering, relay contact activation, etc.) according to the calculation result and control requirements. In addition, intelligent instruments can also form a distributed measurement and control system with a PC. The microcontroller acts as a lower-level machine to collect various measurement signals and data, and transmits the information to the upper-level machine—the PC—through serial communication for global management. 2. Functional Characteristics of Intelligent Instruments With the continuous development of microelectronics technology, ultra-large-scale integrated circuit chips (i.e., microcontrollers) have emerged, integrating circuits such as CPU, memory, timer/counter, parallel and serial interfaces, watchdog timers, preamplifiers, and even A/D and D/A converters onto a single chip. Using microcontrollers as the core, and combining computer technology with measurement and control technology, the so-called "intelligent measurement and control system," or intelligent instrument, is formed. Compared with traditional instruments, intelligent instruments have the following functional characteristics: ① Automated operation. The entire measurement process of the instrument, such as keyboard scanning, range selection, switch start-up and closure, data acquisition, transmission and processing, and display and printing, is controlled by a microcontroller, achieving full automation of the measurement process. ② Self-testing functions, including automatic zeroing, automatic fault and status verification, automatic calibration, self-diagnosis, and automatic range switching. Intelligent instruments can automatically detect the location and even the cause of faults. This self-test can run when the instrument starts up and also during operation, greatly facilitating instrument maintenance. ③ Data processing capabilities, which is one of the main advantages of intelligent instruments. Intelligent instruments, employing microcontrollers or single-chip microcomputers, enable the flexible solution of many problems that were previously difficult or impossible to solve using hardware logic. For example, traditional digital multimeters can only measure resistance, AC/DC voltage, and current, while intelligent digital multimeters can not only perform these measurements but also possess complex data processing functions such as zero-point shifting, averaging, extreme value calculation, and statistical analysis. This not only frees users from tedious data processing but also effectively improves the instrument's measurement accuracy. ④ They offer user-friendly human-machine interaction. Intelligent instruments use a keyboard instead of the switches found in traditional instruments, allowing operators to perform specific measurement functions simply by inputting commands. Simultaneously, the intelligent instrument displays the instrument's operating status, working condition, and the results of data processing, making operation more convenient and intuitive. ⑤ They offer programmable operation capabilities. Generally, intelligent instruments are equipped with standard communication interfaces such as GPIB, RS232C, and RS485, allowing them to easily integrate with PCs and other instruments to form multifunctional automatic measurement systems for more complex testing tasks. 3. Overview of the Development of Intelligent Instruments In the 1980s, microprocessors were used in instruments, and instrument front panels began to evolve towards keyboard-based designs. Measurement systems were often connected via the IEEE-488 bus. Personal instruments, unlike traditional independent instruments, saw development. In the 1990s, the intelligence of instruments was prominently reflected in the following aspects: advancements in microelectronics technology profoundly influenced instrument design; the advent of DSP chips greatly enhanced the digital signal processing capabilities of instruments; the development of microcomputers gave instruments stronger data processing capabilities; image processing functions became widespread; and the VXI bus was widely used. In recent years, the development of intelligent measurement and control instruments has been particularly rapid. A variety of intelligent measurement and control instruments have appeared on the domestic market, such as intelligent throttling flow meters capable of automatic differential pressure compensation, intelligent multi-segment temperature controllers capable of programmed temperature control, intelligent regulators capable of digital PID and various complex control laws, and intelligent chromatographs capable of analyzing and processing various spectra. Internationally, there is a wide variety of intelligent measuring instruments. For example, the DSTJ-3000 series intelligent transmitter produced by Honeywell in the United States can perform composite measurements of differential pressure and automatically compensate for the temperature and static pressure of the transmitter body, with an accuracy of ±0.1%FS. The 9303 ultra-high level meter from Raca-Dana in the United States uses a microprocessor to eliminate thermal noise generated by current flowing through resistors, achieving a measurement level as low as -77dB. The 5520A super multi-functional calibrator produced by Fluke in the United States uses three microprocessors internally, achieving short-term stability of 1ppm and linearity of 0.5ppm. The digital self-tuning controller produced by Foxboro in the United States uses expert system technology, enabling rapid tuning of the controller based on field parameters, much like an experienced control engineer. This type of controller is particularly suitable for control systems with frequent or nonlinear changes. Because this controller can automatically tune the control parameters, it ensures that the entire system maintains optimal quality throughout the production process. 4. Development Trends of Intelligent Instruments 4.1 Miniaturization Miniature intelligent instruments refer to instruments that integrate microelectronics, micromechanical technology, and information technology in their production, resulting in small, fully functional intelligent instruments. They can perform functions such as signal acquisition, linearization processing, digital signal processing, control signal output, amplification, interface with other instruments, and human interaction. With the continuous development of microelectromechanical technology, the technology of miniature intelligent instruments is maturing and prices are decreasing, thus expanding their application areas. They not only possess the functions of traditional instruments but also play unique roles in automation technology, aerospace, military, biotechnology, and medical fields. For example, currently, to simultaneously measure several different parameters of a patient and control certain parameters, several tubes are usually inserted into the patient's body, increasing the risk of infection. Miniature intelligent instruments can simultaneously measure multiple parameters, are small in size, and can be implanted in the human body, solving these problems. 4.2 Multifunctionality Multifunctionality is itself a characteristic of intelligent instruments. For example, to design faster and more complex digital systems, instrument manufacturers have produced function generators that integrate pulse generators, frequency synthesizers, and arbitrary waveform generators. These multifunctional integrated products not only offer higher performance (such as accuracy) than dedicated pulse generators and frequency synthesizers, but also provide better solutions for various testing functions. 4.3 Artificial Intelligence Artificial intelligence is a new field of computer applications that utilizes computers to simulate human intelligence for applications such as robotics, medical diagnosis, expert systems, and reasoning proof. Further development of intelligent instruments will incorporate a certain degree of artificial intelligence, replacing some of the mental labor of humans, thereby possessing certain abilities in vision (graphic and color recognition), hearing (speech recognition and language comprehension), and thinking (reasoning, judgment, learning, and association). In this way, intelligent instruments can autonomously complete detection or control functions without human intervention. Clearly, the application of artificial intelligence in modern instrumentation allows us not only to solve problems that are difficult to solve using traditional methods, but also promises to solve problems that are fundamentally unsolvable using traditional methods. 4.4 Integrating ISP and EMIT Technologies to Achieve Internet Access (Networking) for Instrumentation Systems With the rapid development of network technology, Internet technology is gradually penetrating the fields of industrial control and intelligent instrumentation system design, enabling intelligent instrumentation systems to achieve Internet-based communication capabilities and remote upgrades, function resets, and system maintenance. In-System Programming (ISP) technology is a cutting-edge technology for modifying, configuring, or reconfiguring software. First proposed by Latte Semiconductor, it is a new technology that allows for the configuration or reconfiguration of the logic and functions of devices, circuit boards, or the entire electronic system at any stage of product design and manufacturing, and even after the product is sold to the end user. ISP technology eliminates some limitations and connectivity drawbacks of traditional technologies, facilitating on-board design, manufacturing, and programming. ISP hardware is flexible and easy to modify in software, simplifying design and development. Because ISP devices can be processed on printed circuit boards (PCBs) like any other device, programming ISP devices does not require specialized programmers or complex processes; programming can be performed via a PC, embedded system processor, or even a remote Internet connection. EMIT (Embedded Micro-Internet Technology) was proposed by emWare when it established the ETI (eXtend the Internet) alliance. It's a technology for connecting embedded devices such as microcontrollers to the Internet. Using this technology, 8-bit and 16-bit microcontroller systems can be connected to the Internet, enabling remote data acquisition, intelligent control, and data file upload/download functions. Currently, companies such as ConnectOne, emWare, and Tasking in the US, and P&S in China, all provide Internet-based Device-Networking software, firmware, and hardware products. 4.5 Virtual Instruments: A New Stage in the Development of Intelligent Instruments The main functions of measuring instruments consist of three parts: data acquisition, data analysis, and data display. In virtual reality systems, data analysis and display are entirely performed by PC software. Therefore, by providing additional data acquisition hardware, a measuring instrument can be formed with a PC. This PC-based measuring instrument is called a virtual instrument. In virtual instruments, using the same hardware system, different software programming can produce measuring instruments with completely different functions. It is evident that the software system is the core of virtual instruments; "software is the instrument." Traditional intelligent instruments primarily utilize certain computer technologies within instrument technology, while virtual instruments emphasize the integration of instrument technology into general-purpose computer technology. As the core of virtual instruments, the software system possesses versatility, accessibility, visibility, scalability, and upgradeability, bringing significant benefits to users. Therefore, it boasts application prospects and a market unmatched by traditional intelligent instruments. 5. Conclusion Intelligent instruments are a combination of emerging technologies such as computer science, electronics, digital signal processing, artificial intelligence, and VLSI with traditional instrumentation technologies. With the development of application-specific integrated circuits (ASICs), personal instruments, and related technologies, intelligent instruments will find even wider applications. Single-chip computer technology, as the core component of intelligent instruments, is the driving force behind the development of intelligent instruments towards miniaturization, multi-functionality, and greater flexibility. It is foreseeable that intelligent instruments with various functions will be widely used in all sectors of society in the near future.