Abstract: Virtual instruments are a product of the combination of testing technology and computer technology. Based on graphical programming languages, they allow for the design of custom instrument systems to meet diverse application requirements. This paper applies virtual instruments to the field of measurement and control, proposing and establishing a remote data measurement and control system scheme based on virtual instruments. From an application perspective, a practical application system was designed and completed based on LabVIEW software and a PCI-1711 data acquisition card. Remote monitoring and data acquisition of motors were achieved through Datasocket technology. Keywords: Virtual instrument; PCI-1711; Switching signal; Datasocket; Motor 1 Introduction In recent years, the design, production, and use of virtual instruments have become widespread in some developed countries, and modern measurement and control technologies based on virtual instrument technology are widely applied. Virtual instruments encompass and surpass all the functions of traditional instruments. New instrument systems can be constructed on a computer using a data acquisition card, and different functions can be implemented through virtual instrument programming. Currently, China's measurement and control technology, especially in hardware, remains very weak. Promoting virtual instrument technology to the network, leveraging its advantage of software as an instrument, helps to form a distributed network measurement system, embodying data and instrument sharing, thereby providing services for experimental teaching or remote measurement and control in enterprises. This system is a remote data measurement and control network system based on virtual instruments. While the data acquisition station is acquiring data, it transmits the data to the network server in real time via the network. LabVIEW provides DataSocket, a network software technology and programming tool, which allows data to be shared between different applications and data sources, and these data sources can be distributed across different computers. DataSocket software can also be used to strictly control resource access, grouping users according to different categories and assigning different read and write permissions, thus better protecting resources, reducing the probability of conflicts during resource access, and facilitating network monitoring. 2 Design of a Remote Data Measurement and Control System Based on Virtual Instruments 2.1 Scheme for a Remote Data Measurement and Control System Based on Virtual Instruments Virtual instruments were first proposed by National Instruments in the late 1980s and have long been in practical use internationally. Although it is still in its early stages in my country, virtual instruments have developed rapidly and are widely used in various fields, including electronic measurement, physical flaw detection, electronic engineering, vibration analysis, acoustic analysis, mineral exploration, fault analysis, and teaching and research. Compared with traditional instruments, they are characterized by low cost, full functionality, high efficiency, and distributed operation. Currently, virtual instruments are very common in developed countries. In the United States, virtual instruments have become a compulsory course for science and engineering students in universities. In China, some university laboratories have introduced virtual instrument systems. With the rapid development of science and technology, the application fields of testing technology will continue to expand. This paper mainly focuses on the use of virtual instruments to remotely control field equipment, allowing the pan-tilt unit to rotate up, down, left, and right to monitor the remote field. The PC at the field receives network signals, which are output through the acquisition card and then conditioned by the circuit to reach the pan-tilt unit. The basic measurement and control system framework is shown in Figure 1: [align=center] Figure 1 Measurement and Control System Framework[/align] The main monitoring system running on the receiving computer contains all the modules used to complete temperature and switch control functions. The signal acquisition module can independently control the field monitoring function and can receive control commands from the network. Datesocket is a network transmission technology provided by NI (National Instruments), built on the TCP/IP protocol. It allows simultaneous transmission of field measurement data to multiple remote clients over a network. The field acquisition card connects to the receiving PC. Signals from the sending PC reach the receiving end via Datesocket. LabVIEW software on the receiving PC triggers the acquisition card to output switch signals on its four designated digital output ports. The switch signals output from the acquisition card can be processed by relays, along with a drive circuit, to start or stop the motor on the pan-tilt unit. 2.2 Hardware System Composition The system hardware implements signal conditioning and input/output. Due to the high cost of NI's data acquisition cards, Advantech's PCI-1711 data acquisition card was used. The PCI-1711 provides 16 digital inputs and 16 digital outputs, allowing customers maximum flexibility to apply the technology according to their needs. It also features 16 single-ended analog inputs, a 12-bit A/D converter, a sampling rate up to 100kHz, programmable gain for each input channel, automatic channel/gain scanning, an on-board 1K sampling FIFO buffer, two 12-bit analog outputs, and programmable triggers/timers. Advantech also provides a 32-bit LabVIEW driver to integrate the PC data acquisition board with the LabVIEW software development platform, eliminating the need to develop a separate driver module for the acquisition card using CIN nodes. To save costs, a simple video transmission feature is added to transmit real-time footage of remote field experiments. A pan-tilt unit is added below the camera, which allows the network camera to rotate horizontally and vertically. The pan-tilt unit contains two motors, one for horizontal rotation and the other for vertical rotation. The angles of horizontal and vertical rotation can be adjusted using limit switches. The virtual instrument's internal software triggers a switch output that, through the digital output channel of the acquisition card, activates a relay to control the camera's up, down, left, and right rotation, allowing for omnidirectional observation of the remote experimental footage and achieving remote video monitoring. The ADAM-3968 is an industrial terminal block using a 68-pin SCSI cable. It facilitates communication between the PCI-1711 and external systems and helps shield against field interference. Solid-state relays are used to control the on/off state of motors, adjusting the motor speed through switch switching. A relay is a contactless switch assembled from solid components; its input is isolated using an optocoupler, requiring only a small current to operate. Because there are no moving parts inside the output section, it features reliable operation, fast switching speed, high operating frequency, long lifespan, and no electromagnetic interference. 2.3 System Software Design This remote monitoring system consists of a receiving computer main monitoring system running at the control site and a transmitting monitoring system running on the network. Researchers and engineers, even when not at the control site, can monitor the operation of the control system and real-time changes in system parameters via the network. They can also issue commands from the transmitting computer to the remote receiving computer control system, adjusting the operation of the control system based on images captured by a remote camera, thus achieving remote control. This has significant practical implications in the field of computational control applications. The transmitting end uses a LabVIEW front panel to develop the human-machine interface. Four buttons on the interface control the output of four switching signals. Four switching signals are sent to the remote site via Datesocket technology. The front panel interface is shown in Figure 2. [align=center] Figure 2 Transmitter Front Panel Interface[/align] The button action mode is set to a locked state before release. That is, when the UP button is pressed with the mouse, the UP switching signal is transmitted to the receiving end. Then, the receiving PC sends a command through the acquisition card port, and the pan-tilt unit rotates upwards until the mouse is released and the program reads the value once. The interface includes an acquisition card output port, and the interface designed using virtual instruments is simple and aesthetically pleasing. The receiving end is responsible for receiving commands and executing actions. Its back panel program is shown in Figure 3. [align=center] Figure 3 Receiving End Back Panel Program Diagram[/align] Actual data processing is completed in the back panel block diagram program. This block diagram uses two structures: 1: while loop structure: The entire program repeatedly executes a piece of code in the loop body until a certain condition is met and it terminates. 2. Case Selection Structure: This structure contains multiple sub-block diagrams, each with a code segment corresponding to a case option. During program execution, a segment is selected for execution. In this example, the true/false state is switched using signals received from remote buttons. Besides the sub-modules included with the LabVIEW driver of the acquisition card, this program also uses ActiveDAQ, a 32-bit ActiveX controller provided by Advantech. It enables analog, digital, and counting input/output control for a large number of Advantech data acquisition cards and control hardware. Advantech's ActiveDAQ makes data acquisition more convenient, high-performance, and flexible. Considering that only switch signals are output, the Write to Digital Line function in the ActiveDAQ DO module is used. A digital line is a physical terminal on the data acquisition card that connects to digital signals; the binary representation of a digital line is 0 or 1. Reading the state of the digital line corresponds to the state of the corresponding digital port. 3. Remote Data Transmission and Monitoring Technology: DataSocket is a real-time, high-speed data exchange technology developed by NI based on Microsoft's COM and ActiveX technologies, specifically designed for testing and networking. It is used in the field of automated measurement and control to share and publish dynamic data between applications or between different networks. The Datasocket field control station receives various control commands from the remote monitoring station, executes corresponding operations, and feeds back necessary information such as the motion status of each rotating axis and field alarm signals to the remote end, allowing the operator to monitor the field work from the remote monitoring station. In case of failure (such as a sudden communication interruption), all control tasks can also be completed by the operator on the field control station using a standalone operation mode. That is, the field control station can independently realize various control functions without the host computer. In this case, all operation steps will be entered by the operator on the keyboard of the integrated field control station. This emergency measure can improve the system reliability to a certain extent and ensure the strict work schedule. The Datasocket module has been used in Figure 3. 4 Conclusion The system has been tested and can effectively realize remote control of the field pan-tilt unit, fully realizing the requirements of the remote monitoring design. Due to the use of in-system programming and virtual instrument technologies, the system has good stability and data processing capabilities. Appropriate pre-amplifier circuits or drive circuits are usually designed according to different objects under test, and the functions are flexibly expanded, such as relay drive, solid-state relay drive circuits, etc., which can be applied to control equipment in modern industry. However, due to network latency, signals cannot reach the site in real time. The innovation of this paper lies in using virtual instrument data acquisition technology to save researchers significant effort, allowing for flexible and customized instrument design. LabVIEW's DataSocket technology provides a convenient method for remote measurement and control, enabling researchers to effectively control remote sites without time or space constraints. Furthermore, LabVIEW's web server can publish images or HTML files of the LabVIEW program's front panel over the network, enabling fast web browsing and secure, efficient remote program control. References: [1] Lei Zhenshan. Practical Technical Tutorial of LabVIEW 7 Express [M]. Beijing: China Railway Publishing House, 2004. [2] Li Boquan. Application of DataSocket Technology in Remote Measurement and Control Data Transmission [J]. Journal of Jiangsu University (Natural Science Edition), 2004, 25 (4): 286-288. [3] Chen Zefeng. Rapid Development of Data Acquisition System Based on LabVIEW [J]. Modern Electronics Technology, 2004, (16): 23-25. [4] Dong Xiang. Research on Remote Measurement and Control Method Based on LabVIEW [J]. Automation Instrumentation, 2006, 27 (1): 6-13. [5] Lan Bo. Application of LabVIEW in Virtual Instrument Remote Data Acquisition System [J]. China Test Technology, 2006, (6): 112-134. [6] Pan Hua, Xia Hongmei, Li An, Hu Baiqing. Research on LabVIEW Data Flow Control Method [J]. Microcomputer Information, 2006, 10 [7] National Instruments Corporation, LabVIEW User Manual, January 2004. Downloadable research materials on remote data measurement and control systems based on virtual instruments.