Meteorological Monitoring System Based on LabVIEW

The automatic weather station is relatively large in size, and the location and space when it is used will be affected by the location and space. If you take advantage of the advantages of virtual instrument technology such as easy development, small size and convenient use, you can use virtual instruments to replace the data collector and data preprocessor of the automatic weather station. Virtual instrument technology
uses the computer's hardware resources (CPU, memory, display, keyboard, mouse), standard digital circuits (GPIB, RS 232 interface bus, new VXI interface bus, signal conditioning and conversion circuit, image acquisition circuit, field bus, etc.), and through targeted development and testing, it becomes a set of traditional instruments equivalent to the user's own special design. LabVIEW (laboratory virtual instrument engineering workbench) is an innovative software product of NI (national instruments) National Instruments, and it is also the most widely used, fastest-growing and most powerful graphical software development integrated environment. Simply put, virtual instrument technology is a user-defined test and measurement solution based on PC technology. Compared with traditional instruments, it has four major advantages, namely high performance, strong scalability, less development time, and perfect integration functions.
Here we introduce a design method of a weather monitoring system, using the LabVIEW8.5 of NI Company of the United States as the platform and the weather data collector to realize the design of a virtual weather monitoring system. The system has functions such as data display and data storage. According to the historical data stored in the past, the weather conditions can be displayed and analyzed in a targeted manner.

1 System working principle
The meteorological monitoring system consists of sensors, data collectors, data processing terminals, etc. Sensors are used to sense meteorological elements. Data collectors can collect meteorological elements such as temperature, relative humidity, wind direction, wind speed, rainfall, and air pressure. Data processing terminals can perform calculations on the data obtained by the data collector. The system first collects meteorological data, and then sends the data back to the meteorological data center for data display and data storage. Finally, the meteorological center can also display and analyze historical weather conditions based on the historical data stored in the past. Using modular and hierarchical programming ideas, each module completes a specific function. The meteorological monitoring system designed here consists of four modules: data acquisition, data processing, data display, and data storage. The schematic diagram of the entire system is shown in Figure 1.

2 System Design
2.1 Data Acquisition Module
2.1.1 Data Acquisition Module Structure
To collect data into a computer and organize it reasonably, it is necessary to build a data acquisition module. It includes sensors and transducers, signal conditioning equipment, data acquisition cards, drivers, hardware configuration management software and computers. The physical quantities of meteorological parameters are output as voltage, current, frequency and other signals through various types of sensors, and then collected by the data acquisition card. The data acquisition module is used to obtain the data obtained by the data acquisition card. The module structure is shown in Figure 2.
There are many types of sensors and transducers, which directly deal with various physical quantities and convert these physical quantities into electrical signals that can be collected by the DAQ system. Before designing an automated measurement system, it is necessary to make a detailed analysis of the object to be measured and the measurement requirements, and correctly select the appropriate sensors and transducers. The sensor used in the system is WXT520, which can measure 6 meteorological parameters at the same time, is accurate and reliable, and has a USB interface. The signal conditioning equipment takes measures such as amplification, filtering, and isolation on the signals sent by the sensors and transducers, and converts them into signals that are easy to read by the acquisition equipment. If the actual signal meets the requirements of data acquisition cards and other acquisition devices, the signal conditioning module can be omitted. [page]

2.1.2 Data Acquisition Card
The data acquisition card used in this system is the NIUSB-6210 from the American NI company. It is a USB bus-powered M series multi-function DAQ module that can maintain high accuracy even at high sampling rates. The module provides 16 analog inputs; 250 kS/s single-channel sampling rate; 4 digital input lines; 4 digital output lines; 4 programmable input ranges (±0.2 v to ±10 V) per channel; digital trigger; 2 counters/timers. The USB-6210 pinout is shown in Figure 3. The NI USB-6210 is specially designed for mobile applications or applications with limited space. Its plug-and-play installation minimizes configuration and setup time. At the same time, it can be directly connected to screw terminals, thereby reducing costs and simplifying signal connections. The power supply of the USB bus eliminates the need for users to carry extra external power supplies. The module also features the new NI signal data stream technology, which implements bidirectional high-speed data stream operations similar to DMA on the USB bus.

2.2 Software Design
The system development adopts LabVIEW, a special programming language for virtual instruments of NI. It is a graphical programming language and development environment that has been widely accepted by industry, academia and research laboratories, and is recognized as a standard data acquisition and control software. When programming with this language, it is basically not necessary to write program code, but to "draw" a program flow chart. In the case of one hardware, the functions of different instruments can be realized by changing the software, which is very convenient. Its data analysis function and graphic display capability can meet the needs of the meteorological monitoring system. The open development environment and flexible scalability are difficult to achieve with existing means. In the real-time weather display part, the system mainly completes the two parts of data display and data storage.
2.2.1 Design of real-time weather display part
The data display part is relatively simple. The system can obtain the collected meteorological data such as temperature, relative humidity, wind direction, wind speed, rainfall and air pressure from the data acquisition module, and display them through the front panel of LabVIEW. The date and time of the meteorological elements collected by the system are obtained and displayed in real time. Through the LabVIEW platform, graphical programming is used, and there is no need to face complex and lengthy text codes, and the effect of getting twice the result with half the effort can be achieved. The data acquisition card completes the data acquisition function. The data operation analysis and processing as well as the control of the acquisition card are all performed in the background by the virtual instrument software. The measurement results are displayed on the front panel of the virtual instrument. The main interface of the real-time weather display part of the meteorological monitoring system is shown in Figure 4.

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LabVIEW adopts a new graphical programming method. Not only is the human-machine interface established using the "what you see is what you get" visualization technology, but the program code is also graphical. Each object placed on the front panel will have a corresponding terminal in the block diagram program. The various functional functions required by the block diagram program editing window, including various mathematical operation functions, signal analysis functions, instrument driver functions, etc., are provided by the function template in the form of icons. Designers only need to take out the corresponding icon from the function template, place it in the program block diagram editing window, and then use the "connection" tool to connect it to realize the data transmission between each other, thus forming a complete block diagram program. The system can update the meteorological data obtained from the data acquisition equipment in real time, and divide it into six factors: temperature, rainfall, air pressure, relative humidity, wind speed, and wind direction to display the latest weather data collected in real time. The real-time weather display part of the program block diagram is shown in Figure 5.

2.2.2 Design of historical weather analysis part
The historical weather analysis part is an independent program Weatherhistory.vi, which can analyze historical weather conditions based on historical data stored in the past. According to the rainfall, weather information at different times of the day can be stored in the computer as a data resource for reference and historical data analysis. The interface and program flowchart of the historical weather analysis part are shown in Figures 6 and 7.
The data storage part selects the data record file type to store meteorological elements. One of the main benefits of this type is that it can be stored selectively, effectively retaining various useful combination information. At the same time, the system has a file storage function, which can save the input data and the results of the analysis.

3 Conclusion
This meteorological monitoring system is developed on LabVIEW8.5 platform and cooperates with NI USB-6210 meteorological data collector to realize the basic functions of virtual weather station. The meteorological monitoring system has been successfully used in ground meteorological observation and has the advantages of low cost and convenient operation. With the continuous development of computer technology and modern instrument technology, the design of virtual instruments with LabVIEW as the development tool will be more and more applied in meteorological monitoring.