Abstract: With the increasing attention drawn to energy issues, jet refrigeration, a cooling method driven by low-grade heat sources, has gradually gained popularity. This experimental system uses electric heating to simulate solar energy. This paper mainly introduces the jet refrigeration measurement and control system developed on the LabVIEW platform, which can realize real-time data acquisition, storage, and data analysis. Keywords: jet refrigeration, measurement and control, LabVIEW 1. Introduction The development of air conditioning systems towards new energy sources and the reduction of electricity consumption is an inevitable trend. Currently, worldwide, the research and application of solar-driven jet refrigeration, absorption refrigeration, and adsorption refrigeration have received widespread attention and achieved certain results. In early research, absorption refrigeration systems were the focus of many researchers. However, their design and operation and maintenance are relatively complex, and after a period of operation, problems such as the decrease in the chemical stability of the working fluid and the difficulty in maintaining a high vacuum in the system will lead to a decrease in system efficiency. At the same time, the initial investment in absorption refrigeration is large, which is also an obstacle to its further development. Therefore, in recent years, jet refrigeration has received more attention [1]. However, if solar energy is used directly as a heat source for heating, it is easily affected by the weather and it is difficult to ensure the stability of the experimental process. Therefore, most of the experiments currently conducted use electrical energy as a direct heat source. In order to ensure the accuracy of the experiment, the water temperature must be accurately controlled. The PID controller is a control method that can be used for convenient and accurate temperature control. However, the disadvantage of this method is that a separate PID controller needs to be purchased, and it is not convenient for remote computer control. For this reason, the author developed a measurement and control system on the LabVIEW platform for the solar jet refrigeration experimental system. LabVIEW is a graphical programming software launched by National Instruments in the United States for the field of measurement and control. This article mainly introduces a PID control technology implemented by LabVIEW formula nodes and a measurement and control system established using its simple data acquisition method. 2. Working Principle PID Control Principle PID control achieves system control through three links: proportional, integral, and derivative. The block diagram of a conventional PID control system is shown in Figure 1. PID control is a linear control method. It constructs a control deviation based on the given value r(t) and the actual output value c(t): e(t) = r(t) - c(t) (1) After calculating the deviation proportionally (P), integrally (I), and derivatively (D), the control quantity is formed by linear combination and acts on the controlled object. Its control law is: (2) It is expressed in the form of a transfer function as: (3) Where kp — proportional coefficient Ti — integral time constant Td — derivative time constant The proportional link reflects the deviation signal of the control system proportionally. Once a deviation occurs, the controller generates a control action to reduce the deviation. The integral link is mainly used to eliminate static error and improve the accuracy of the system. The strength of the integral action depends on the time constant Ti. The smaller Ti is, the stronger the integral action. The differential element reflects the changing trend of the deviation signal. Introducing an effective advance correction signal into the system can accelerate the system's action speed and shorten the adjustment time. PID control is implemented in LabVIEW. LabVIEW provides the PID Toolkit to implement PID control of the controlled object. This article introduces a new and simple method for implementing PID control through a formula node. The formula node program is shown in Figure 1. Where Tset is the set temperature value, input is the actual temperature value, and unew is the output voltage value of the control voltage regulation module. The P, I, and D values ​​are set through the front panel. To prevent the integral accumulation of PID calculations during system startup, which could cause the calculated control quantity to exceed the maximum operating range of the electric heater and cause system overshoot, this system adopts an integral separation PID control method. e is the set threshold value. When enew is greater than e, only PD control takes effect, which avoids excessive overshoot and allows the system to have a faster response. When enew is less than or equal to the e value, i.e., the deviation is small, PID control is used to ensure the control accuracy of the system. Through a brief calculation within the formula node, the result unew is output as a voltage signal to the voltage regulation module, which controls the power of the electric heating. System Principle The entire system includes six HT100 pressure sensors, eight Pt100 temperature sensors, and a USB2000A to jointly complete the data acquisition function. The USB interface, PC, and LabVIEW together constitute the data receiving and display unit. The control function is performed by the voltage regulation module TY-H380D. The system block diagram is shown in Figure 2. First, the required parameters such as generator temperature, P value, I value, and D value are set on the PC, and the system starts running. The sensors send signals to the data acquisition card USB2000A, which then sends them to the PC via the USB interface. By comparing the actual measured generator temperature with the set value, the PC sends a signal to control the voltage regulation module to adjust the heating amount. 3. System Software Design This system uses LabVIEW to develop measurement and control software, which can easily realize real-time data acquisition, storage, processing, and analysis. Furthermore, this program, through its link with a simulation calculation program written in VC++, enables the comparison of simulation calculations and experimental data. This intuitive comparison allows for the analysis of the errors between experimental results and simulation calculations under given operating conditions. This allows for the correction of the simulation calculation method, making it more comprehensive and ensuring the calculation results better match actual experimental results. The program's front panel uses a tab container to easily switch between system principle flash display, real-time data display, and data analysis, as shown in Figure 3. The main program consists of a data acquisition module, a data storage module, a control module, and a data analysis module. The main function of the data acquisition module is to select the channel range of the board and package the acquired temperature and pressure data in a certain order for further processing. The main components of the module are shown in Figure 4. The data storage module saves the data obtained by the acquisition module in spreadsheet format. During data acquisition, the system creates a measurement data file to record the data. This module can convert the sampled data and sampling time into standard spreadsheet data and append it to the created data file. Since the data is written in real time, that is, the data is written to the file after each sampling is completed, the impact of unexpected situations on the measurement system can be minimized. The control module is designed for the electric heating control of the generator. This module mainly realizes the integral separation PID control of electric heating through the formula node. Experiments have shown that the control algorithm can well meet the requirements of temperature control accuracy. The data analysis module can process and display the data from the sampling module, and after processing, output it as a complete data table on the user terminal. At the same time, this module realizes the link with the VC++ simulation program through the CIN node provided by LabVIEW [2], which can display the simulation calculation results and experimental data at the same time, which is convenient for comparison and error analysis. [align=center] Figure 4 Main components of the data acquisition module [/align] 4. Summary Using the powerful functions of LabVIEW and combined with the simulation calculation program of VC++, a visual and intuitive solar jet cooling system measurement and control system was developed. It can perform real-time data acquisition, display, analysis and control of the experimental platform. The system is simple, reliable and has good real-time performance, which can provide a guarantee for the smooth progress of the experiment. References [1] HUANG BJ, CHANG JM, PETRENKO VA, et al., A solar ejector cooling system using refrigerant 141b, Solar Energy, 1998, 64: 223-226 [2] Huang Qiuyun (translator), E.Y. Sokolov, H.M. 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