1. Field instruments are entering a new stage of digitalization, intelligence, and networking. Fieldbus intelligent instruments are a specific concept, referring to intelligent instruments designed and manufactured according to the international fieldbus protocol. They emerged with the advent of fieldbus control systems and, like fieldbus itself, have developed rapidly. According to the International Electrotechnical Commission (IEC), a "fieldbus" is a digital, serial, and multi-point communication data bus installed between field devices in manufacturing or process areas and automatic control devices in control rooms. We can also describe the meaning of fieldbus from different perspectives: from a communication perspective, fieldbus can be defined as a bidirectional, serial digital communication system used to achieve two-way, serial communication between measurement and control equipment in the production field, or as an open, digital, multi-point communication technology; from a technical perspective, fieldbus technology can be considered as embedding dedicated microprocessors into traditional measurement and control instruments, enabling each to have digital communication capabilities and become a node in the network, capable of independently completing measurement, control, or communication tasks. The fieldbus system transforms multiple dispersed measurement and control instruments or devices into network nodes, forming a network and control system to complete automatic measurement and control tasks. From an information network perspective, the fieldbus integrates the automatic measurement and control system of the production process and its instrumentation devices into the information network, forming the enterprise's underlying information network. The fieldbus control system decentralizes control functions to the field, where intelligent field instruments handle them, achieving a truly fully distributed system architecture. Under the fieldbus control system, intelligent field instruments replace the analog field instruments in traditional distributed control systems. The term "intelligent" here refers to the field transmitters' control functions, such as PID control, in addition to signal conversion and compensation. Actuators, besides regulation and drive functions, also possess characteristic compensation and self-diagnostic functions. In other words, under the fieldbus control system, field instruments have functional autonomy, distributing sensing, measurement, compensation calculation, engineering quantity processing, and control functions among the field instruments. Generally speaking, the meaning of "intelligence" has two levels: (1) it is the adoption of artificial intelligence theory, methods and technologies; (2) it is the possession of human-like intelligent characteristics or functions, such as self-adaptation, self-learning, self-correction, self-diagnosis, self-organization, etc. Fieldbus intelligent instruments and fieldbus control systems have an inseparable and close relationship. The adoption of fieldbus control systems must be matched with fieldbus intelligent instruments. Therefore, the study of the implementation and development technology of fieldbus intelligent instruments is of great significance. Control instruments are technical tools for achieving control effects. They include various field instruments and computers, etc. They are not only technical tools, but also the source of information and a component of the information industry. In the process of control automation, they replace people in measuring, monitoring, controlling and protecting the control process, playing a very important role. The development of field instruments and control instruments has gone through several stages: mechanical, electronic, microcomputer and digital. In terms of instrument function, it has also gone through several levels: single-function instruments, combined instruments, digital, intelligent and networked instruments. In terms of technology, it has now moved beyond the era of analog technology and is entering a new stage of digitalization, intelligence and networking. 2. Digitalization and networking are the core technologies of fieldbus instruments. The widespread application of fieldbus, in a sense, hinges on whether field instruments possess the capability to network and match with the fieldbus, and whether various sensors, transmitters, actuators, pumps/valvees, and other field devices have digital, intelligent, and networked functions. Given the current multi-standard fieldbus architecture, to meet the requirements of different users and connect field instruments (I/O devices) with different communication protocols at the underlying level, it is necessary not only to design and develop various corresponding converters and gateways, but more importantly and urgently, to design and develop intelligent and networked fieldbus smart instruments such as transmitters, actuators, and pumps/valvees. Fieldbus is developing rapidly, but due to the coexistence of multiple standards and the lack of a unified standard, it is currently in a stage of fierce competition and diverse approaches. Also, because there is no unified standard for fieldbus, it is difficult to standardize the communication protocols of fieldbus smart instruments, and major instrument manufacturers are developing fieldbus smart instruments that conform to one or more communication protocols. In the 1980s, the development of computer technology and its application in instrumentation made instrument digitization possible. Microprocessor-based microcomputer instruments emerged, producing various digital transmitters, digital controllers, digital display recorders, programmable logic controllers (PLCs), and intelligent instruments. Compared to analog instruments, digital instruments have made a qualitative leap in functionality, performance, reliability, and communication capabilities. Various parameter information in control systems is generated by transmitters. Various new digital transmitters employ advanced sensors, microprocessors, parameter compensation, digitization, and network communication technologies, achieving integrated detection and conversion in their structure. Fieldbus is a fully distributed, fully digital, bidirectional, multi-variable, multi-point, and multi-station serial communication network that enables the transmission of multiple signals from multiple nodes on a single bus. Driven by the rapid development of computer networks, traditional loop control systems have undergone fundamental changes. Coupled with the development and application of fieldbus systems, networked products consisting of conventional sensors, transmitters, displays, controllers, and actuators have been formed, further realizing the networking of detection, transmission, display, control, and execution units. Network systems have undergone a fundamental structural change compared to conventional loop control systems. The transmission of electrical signals representing process control information is no longer through direct point-to-point connections, but rather through field-level networks in digital form. This means that all information between instruments is transmitted via the network. The network's extension and presence in the basic control loop is a fundamental manifestation of networked control. In fieldbus control systems, field instruments are treated as nodes in the network, called intelligent nodes or field intelligent devices. These devices should possess digital communication capabilities and functions such as control, compensation, parameter modification, alarm display, and fault diagnosis. 3. Fieldbus Intelligent Instruments Composed of Functional Modules. Fieldbus intelligent instruments can flexibly combine functional modules according to the characteristics of different controlled objects to achieve control strategies, becoming highly agile intelligent instruments. The 10 basic functional modules included in the FF fieldbus are shown in Table 1. These 10 functional modules can be flexibly combined to achieve various functions. For example, a temperature transmitter can be configured with an input (AI) function module, and a control valve can be configured with a PID function module and an output (AO) function module. Thus, a control loop can be constructed using only one transmitter and one control valve, as shown in Figure 1. It must be noted that the configuration and combination of function modules depend on the control strategy adopted for the controlled object; the choice of function modules varies depending on the system's control scheme. 4. Fieldbus Intelligent Instrument Control System The development of process control systems has undergone technological changes such as single-loop feedback control, distributed control, and fieldbus control. The system structure has gone through several stages: pneumatic, electric, direct digital control, and distributed control, and is now moving towards fieldbus network control systems. The application of systems has gone through several stages: single-machine automation, unit automation, and integrated automation, and is developing towards integrated control and management. Early single-loop PID control, based on classical control theory, has always been the main means of industrial process control; with the requirements of complex industrial control, cascade, ratio, feedforward, uniform and other complex control systems have been gradually developed; with the emergence of modern control theory based on state space method, control systems such as state feedback, decoupling control, optimal control, and adaptive control have emerged; with the rapid development of computer technology and its widespread application in industrial control, new control systems represented by distributed control systems DCS and PLC programmable controllers have emerged; the development of artificial intelligence has brought new breakthroughs to the control field, and advanced control technology and advanced control systems have emerged in industrial control. Advanced control software has formed a comprehensive solution for plant-wide integrated automation that integrates hardware and software. The emergence of fieldbus control system has changed the basic structure of traditional industrial control system, with stronger openness and practicality. Therefore, the automation control system built has greater flexibility and can provide enterprises with a comprehensive and integrated automation solution from field control to enterprise management. The following are some examples of fieldbus intelligent instrument control systems: (1) Fieldbus control system composed of multivariable transmitters. Multivariable transmitters can accept multiple input parameters and can measure multiple parameters. For example, it can measure fluid temperature, pressure, and differential pressure, and accurately determine the fluid flow rate based on the fluid's temperature, pressure, differential pressure, and fluid type. A block diagram of a multivariable transmitter matched with a fieldbus is shown in Figure 2. Multi-parameter signals from the field sensors are sent to the A/D conversion unit via a multi-input programmable amplifier. The transmitter's core microprocessor system is responsible for selecting the amplifier's amplification factor, realizing data acquisition and processing, and configuring the interfaces of the LCD display, transmitter keyboard, and fieldbus. The fieldbus uses the LON bus. To fully utilize the network communication function of the TP/FT-10 module, the transmitter adopts a dual-CPU design, using an 8-bit microprocessor chip 89C51 and a neural network chip to jointly complete various control functions. The TP/FT-10 module mainly provides LON network communication functions, while the 89C51 completes the field control functions, as shown in Figure 3. Data exchange between the neural network chip and the 89C51 is achieved through asynchronous serial communication. [align=center] Figure 3 Block diagram of dual-CPU multivariable transmitter[/align] (2) Fieldbus control system composed of intelligent pump controller As we all know, pumps are widely used in industrial control systems, and most process industries must use pumps. With the application of fieldbus control system (FCS) in industrial enterprises, the original pumps, due to the lack of parameter monitoring function and inability to be used in conjunction with fieldbus control system, can no longer meet the requirements of modern industrial systems. There is an urgent need to produce intelligent pumps that support fieldbus and have parameter monitoring function. In order to enable the pump performance to support fieldbus and have parameter monitoring function, it is necessary to develop intelligent pump controller. The main technical problems to be solved by intelligent pump controller are: connection interface with fieldbus, so that it has the function of communicating with fieldbus; the ability to monitor the main parameters of pump such as flow rate, head, speed, power, efficiency, bearing temperature, inlet pressure, outlet pressure, etc., that is, to have the function of parameter display and control, so it must be a digital system. The fundamental difference between intelligent pumps and ordinary pumps lies in their operating status. Ordinary pumps cannot sense their own working status and make self-adjustments and controls, while intelligent pumps not only have fieldbus functionality but also measure their operating and status parameters through sensors. The measurement results are then input into a microprocessor for automatic control. Since pumps have numerous operating and status parameters, selecting key parameters for measurement is essential to ensure a good performance-price ratio for intelligent pumps. The main pump parameters include flow rate, head, speed, power, and efficiency. In the FCS system, the intelligent pump controller acts as a slave device, exchanging data with the fieldbus interface (Anybus-S) according to specifications, and running and monitoring specific devices under fieldbus configuration. The intelligent controller has a local human-machine interface (operation keys and an LCD display) and can also be operated remotely. The intelligent pump controller has a communication standard interface of 485 or RS232. It is also equipped with a fieldbus interface, a 34-pin connector that can directly connect to a DeviceNet Anybus card or connect to a Profibus-DP IM183 card via a self-made DPRAM interface card. The W78E58 can use this port to write information to be sent into the DPRAM of Anybus or a self-made DPRAM interface card. It can also read information from the host computer from the DPRAM of Anybus or a self-made DPRAM interface card. This enables fieldbus network connections in Device Net or Profibus-DP formats. The intelligent pump controller has a standard RS232 interface, configured by the W78E58 through an extended serial interface (8250), connecting the SIN and SOUT pins of the 8250 to the MAX232C to complete the TTL to RS232 level conversion. The intelligent pump controller also has a fieldcommand interface, which is a parallel communication port that connects to the IM183 (Profibus-DP) via a 50-pin connector or to the Anybus (Device Net) card via a 34-pin connector. The W78E58 can use this port to write information to be sent into the dual-port RAM on the IM183. Simultaneously, information sent to the host computer via this port can be read from the IM183's dual-port RAM. This enables configuration of fieldbus networks in Profibus-DP or DeviceNet formats. In the DeviceNet system, the intelligent pump controller's bus interface uses the Anybus-s template. A communication interface with Anybus-s is designed in the intelligent controller. The Anybus-s communication module provides developers with both parallel and serial development methods. Here, we adopt the parallel development method. The communication module provides a 2KB dual-port RAM as a common data buffer for data exchange between the Anybus and application ends. The dual-port RAM can be used as an external data storage area, externally addressed and read/written by the application CPU. When the CPU writes to the second-highest byte register 7FEh (application status register), the dual-port RAM generates an interrupt to notify the Anybus end to process the relevant data. When reading the highest byte register 7FFh (anybus status register), the interrupt signal generated when the Anybus end writes to the highest byte register is cleared. The application and Anybus end rely on these two registers for handshaking during data and message exchange. The software design of the intelligent pump controller adopts a structured and modular design method. It is mainly divided into two parts: monitoring program and interrupt service program. Each part is composed of many functional modules. Taking the DL144-18X2 ordinary water pump as the object, under the control of the software, it automatically monitors its flow rate, pressure, temperature and other parameters, and controls the pump output according to the control requirements to realize the automatic adjustment and control of the pump. The intelligent pump control scheme is designed into two types: open-loop control and closed-loop control. In open-loop control, the controller monitors the parameters of the pump and displays the values ​​of each parameter in real time. In closed-loop control, the controller controls the flow rate or head. The overall system architecture of the demonstration system is shown in Figure 4. [align=center] Figure 4 Intelligent pump fieldbus control system[/align] The intelligent pump controller (lower computer) of the system transmits the field parameter information to the upper computer, and the upper computer receives the information and displays it on the interface. After obtaining the control rights, the upper computer can also perform direct remote operation. (3) Fieldbus control system composed of intelligent valves In industrial control systems, valves are widely used and very important. However, conventional valves do not support fieldbus and cannot be used in fieldbus control systems. Intelligent valves must be used in fieldbus control systems. Therefore, conventional valves must be transformed into fieldbus intelligent instruments, becoming fieldbus intelligent valves. Figure 5 shows an intelligent valve control system based on the DeviceNet fieldbus. The system measures the valve's operating parameters through sensors, inputs the measurement results into a microcontroller for processing, and the microcontroller sends open, close, and stop control signals to directly control the valve locally. The host system can also send control signals to the slave system via the DeviceNet fieldbus, allowing the slave microcontroller to adjust the valve and achieve remote control. The host system consists of configuration software, an OPC interface, and a DeviceNet bus adapter. The slave system consists of a microcontroller system, a bus slave interface, I/O interfaces, a keyboard, and an LCD display. The microcontroller system controls the various peripheral modules, and the bus slave interface is the slave communication module of the DeviceNet bus, connecting sensors, actuators, and the DeviceNet fieldbus. Input and output interfaces convert measurement data and output control signals to the actuators to control the equipment. The keyboard and LCD display enable setting, modifying, and displaying system parameters. The system has two main functions: local control and remote control. In local control, the microcontroller continuously collects data such as valve stroke and bearing temperature through the data acquisition circuit, makes control decisions, and drives the equipment. In remote control, the slave device transmits data to the master device via the bus for monitoring, while the master device sends valve opening and closing commands to the slave device for direct control, achieving remote operation. Generally speaking, an electric actuator is a system terminal control instrument. It directly operates and changes the valve opening degree based on control electrical signals. Utilizing microcomputer and communication technologies, it achieves functions required by various control technologies, such as bidirectional communication, PID regulation, online automatic calibration, self-calibration, and self-diagnosis. 5. Conclusion: Fieldbus intelligent instruments, characterized by bidirectional digital communication, self-diagnostic functions, and remote modification of instrument configuration data, and with digitalization and networking as their technological essence, have brought field instruments to a new stage. At present, due to the coexistence of multiple fieldbus standards, it is difficult to unify the communication protocol of fieldbus intelligent instruments. Therefore, it will develop towards open system and unified standard, just like fieldbus. 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