Abstract: This system fully utilizes the digital information of HART smart instruments to realize online monitoring of field HART smart instruments, improving the reliability of the control system, reducing the probability of false alarms, reducing the maintenance of field instruments, and significantly reducing maintenance costs. Keywords: HART; smart instrument; online monitoring 1 Widespread Application of Smart Instruments With the development of process control technology and smart instruments, DCS has been widely used in petroleum, chemical, steel, metallurgy, and power industries, realizing a high degree of automation in enterprise production operations. The development of intelligent sensor technology and the maturity of microelectronics technology have provided a reliable guarantee for fully leveraging the advantages of DCS. Intelligent instruments based on the HART protocol have been widely used in DCS. How to maximize the use of the expensive investment in automated systems for early manufacturing, and on the basis of existing intelligent instrument equipment and DCS, without affecting the normal operation of the original DCS, to construct an online diagnostic and management system for enterprise intelligent instruments, and to publish real-time intelligent instrument information to the local area network, extending real-time process management to every area of ​​the field information system, has become a technical issue to be solved in the field of automation. For the actual situation of enterprise field production, an online diagnostic and management system that can meet the above needs is particularly necessary. This paper will explore the design and implementation method of an online diagnostic management system. 2 System Architecture This system mainly consists of intelligent instruments, HART protocol communication devices, HART server communication software (including COM server software and OPC server software), a database, and upper-level management software (including application server and client). Intelligent instruments mainly refer to instruments based on the HART protocol, common types of which include differential pressure transmitters, pressure transmitters, valve positioners, flow meters, etc. The HART protocol communication device is responsible for collecting and transmitting digital signals from smart meters. These signals are transmitted to the host computer's RS-232 serial port via the Adam module. The COM server software parses the data and stores it in real-time through an SQL Server database. Other automation systems can remotely access the data from the field meters through the OPC communication server software. The application server's main function is to configure and monitor the field smart meters, providing a visual user interface for easy operation. The client is responsible for publishing monitoring information and connection status of the field smart meters on the network. The system architecture is shown in Figure 1. [b]3 HART Protocol Communication Device 3.1 Overview of the HART Protocol Communication Device[/b] The HART protocol communication device, without affecting the normal operation of the existing DCS, extracts the digital signals from the analog signals of the field HART smart meters, reads the basic information and process variables of the meters, and transmits them to the host computer via RS-232. It also supports the forwarding of commonly used special commands from the host computer, reads the special command information of the meters, and returns it to the host computer. The HART protocol communication device and the HART protocol communication server software work together to complete the information reading and command forwarding of the field HART smart meters. It provides sufficient interface components to facilitate the development and expansion of application server software. The interface and functions of the application server software can be customized based on the interfaces provided by the HART protocol communication server software, enabling the configuration and monitoring of HART smart meters. The main body of the HART protocol communication device consists of several HART protocol bridges mounted on a terminal block bracket (this article uses 20 bridges as an example). They are connected to the host computer via an RS-485 bus. The bridge addresses can be any value from 0 to 30, but cannot be repeated. The default addresses of the 20 bridges are 1 to 20 in the order of their installation positions. Each HART protocol bridge can collect 12 HART signals, thus the HART protocol communication device can achieve independent communication with 240 HART smart meters. Signals conforming to the HART protocol are processed by the HART bridges, then converted to RS-232 signals via an RS-485 communication line and an RS-485/RS-232 converter before entering the computer. The 20 HART protocol bridges are all powered by a unified 24V/1A power supply, while the RS-485/RS-232 converters are powered independently by a 24V/0.5A power supply. The system connection diagram of the HART protocol communication device is shown in Figure 2. 3.2 HART Protocol Bridge FW581 The block diagram of the FW581 is shown in Figure 3. The hardware circuit mainly includes: a central processing unit (CPU), a HART modem and coupling circuit, a signal selection and isolation circuit for field instruments, an RS-485 interface circuit, and a WDT circuit. The FW581 is divided into two layers, connected by two sets of pin headers. The upper layer board includes a DC-DC module, a CPU module, an RS-485 interface module, an address setting module, indicator lights, etc. The CPU module and RS-485 interface module of the upper layer board are placed on the back of the board, making the FW581 more aesthetically pleasing and secure. The two pairs of RS-485 bus interfaces on the lower board are connected in parallel, facilitating the wiring of multiple FW581s on the same RS-485 bus. The FW581's RS-485 communication signal must be converted to RS-232 signal via an RS-485/RS-232 converter before it can communicate with the upper-level management software. The communication rate is 19.2 Kbps. The FW581 can be powered by two redundant 24V power supplies. The two pairs of RS-485 bus interfaces are connected in parallel, facilitating the wiring of multiple FW581s. The upper board has four indicator lights to display the FW581's operating status; a DIP switch is used to set the FW581's address. The FW581 address is set via the SW4O1 DIP switch on the upper board. "1" on the DIP switch represents the least significant bit; "8" represents the most significant bit; "ON" indicates logic 1; otherwise, it represents logic 0. The address setting conforms to binary encoding, therefore the DIP switch directly displays the card's binary address. After converting the binary number to a decimal number, it becomes the decimal address of the card. 4 HART communication server software The HART communication server software that is compatible with the HART protocol communication device includes a COM server and an OPC server. The COM server realizes serial communication with the HART bridge, sends commands to the HART bridge to read basic information and process variables of the instrument, receives and processes the process variables and alarm information transmitted from the HART bridge; and supports forwarding special HART protocol commands downwards to realize the configuration and monitoring of the field HART instruments. The OPC server transmits the field HART instrument signals to the OPC server workstation. The interface description of the HART Server communication server is listed in Table 1. The commands of the HART protocol include three types [1]: general commands, ordinary commands and special commands. General commands are applicable to all smart devices that follow the HART protocol, and mainly include reading the manufacturer and device type, reading the value and unit of the main variable, reading the value of the dynamic variable and the main variable current, etc.; ordinary commands are applicable to most HART smart devices, but not all of them, and are used for common operations. The main commands include reading selected process variables, writing master variable range values, and handling non-master variable over-limits. Special commands are determined by the specific HART device manufacturer for specific applications. Most component interfaces provided by the COM server are based on general commands; both ordinary and special commands can be directly issued and parsed through the Transfunc interface of the HartTrans component. 5. Structure and Functions of the Host Computer Management Software In the central control room of a petrochemical enterprise, there is one HART instrument communication cabinet, one server, two PCs, and over 200 HART smart instruments of various types. With the gradual deepening of the enterprise's modern management system, configuring and monitoring smart instruments through HART handheld devices has become very inefficient. The SID smart instrument online diagnostic and management system based on the Windows-NT platform is adopted to fully utilize the digital communication and intelligent functions of smart instruments. Through the network, remote management, operation, and maintenance of real-time smart instruments in the field are realized, providing a direct and comprehensive reflection of the status and process information of real-time equipment in the field. 5.1 Software Structure The intelligent instrument online diagnostic and management system adopts the currently popular server/client model. Multiple clients can share the server's real-time information, allowing users to remotely monitor and maintain intelligent instruments from the site. This model is characterized by its high professionalism, strong security, and robust interactivity. After the COM communication server collects data, it stores it in a designated database. The application server then reads the real-time information from the database and publishes it over the network through the clients. However, this structure also has certain drawbacks, namely, it is difficult to maintain and integrate. If the instrument view on the application server changes, to ensure consistency between the client and the application server's instrument view, the client directly downloads the view data over the network to update the view, thus avoiding the cumbersome process of client software upgrades. 5.2 Main Functions of the Software According to management requirements, the main functions of the intelligent instrument online diagnostic and management system should include: a field device view module, which can organize views according to the manufacturer, device type, and device tag number of the intelligent instrument, as well as by control loop, making it easy for users to understand the specific location of each device, and also organize views according to the network connection status of the device, making it easy for users to understand which interface of which converter the device is on; a device access function module, which mainly completes communication with the intelligent instrument, obtains the parameters of the intelligent instrument, configures the intelligent instrument, and detects the real-time status information of the device; and a record review module, which records the modification operations made by the operator to the field device, including the old and new values ​​of the operation content, the time of the operation and the reason for the operation, and records the alarm status of the field device, including the alarm device, the alarm time and the alarm content, so as to facilitate timely and accurate decision-making by the management personnel. 5.3 Special Channel for Transmitting HART Commands The COM server has solved the communication with some intelligent instruments very well, but if the intelligent instrument follows the HART protocol with special commands, it must communicate normally through the special channel provided by the COM server, namely the Transfunc function of the HartTrans component. The data collected from the intelligent instrument is initially binary code. This requires converting the data into decimal according to the data link layer frame format and the IEEE 754 standard. However, the formats of each HART command are different, so each command needs to be parsed separately. Let's take the No. 1 general command as an example. When the No. 1 command is sent to the instrument through a special channel, the returned data is as follows: There are 9 bytes in total, each byte consisting of 2 hexadecimal digits. The first byte is the HART command number, currently the No. 1 general command; the second byte indicates the byte number starting from the third byte; the third and fourth bytes are the checksum of this response code; the fifth and ninth bytes are the current PV value of the smart instrument, which meets the IEEE 754 standard. The IEEE 574 single-precision floating-point standard specifications are listed in Table 2. In Table 2, 's' represents the sign of the mantissa, 1 for negative and 0 for positive; 'E' represents the exponent, and the difference between it and the decimal number 127 is represented in two's complement form; 'M' represents the mantissa. The value of the floating-point number is obtained by multiplying 2 raised to the power of the unoffset exponent by the 24-bit mantissa. The 24-bit mantissa consists of an assumed highest bit of 1, followed by a decimal point, and the 23rd bit of the mantissa. V = S1.M × 2E-127 The binary number composed of the last 5 bytes is 00111100 01001101 11000111 01011110, which, after conversion, has a decimal value of approximately 12.559 413 9%, and the value read by the instrument is 12.559, which is basically the same. 5.4 COM Server Polling Time Before the intelligent instrument online diagnostic and management system software runs, COM server initialization is necessary. This is to obtain the currently functioning HART bridges and online intelligent instruments in the HART protocol communication device, polling twice. Experiments and calculations show that with 20 bridges functioning normally and each bridge fully loaded (each bridge connecting 12 intelligent instruments, totaling 240 intelligent instruments), COM server initialization takes approximately 7 minutes. If the number of intelligent instruments is greater, the COM server initialization time will be longer. 6 Conclusion HART protocol communication devices offer good stability, and the host computer software is easy to operate, greatly improving the inefficiency of traditional instrument management modes and further enhancing the automation level and office efficiency of enterprises. References: 1 Yang Xianhui. Fieldbus Technology and Its Application. Beijing: Tsinghua University Press, 1999