Development of a graphical user interface based on a certain type of data storage pressure meter

0 Introduction
The explosion shock wave overpressure tester is an essential test instrument for various explosion tests. The reconfigurable data storage pressure gauge is a new type of explosion shock wave overpressure test instrument. This instrument is different from the traditional test system. It does not require lead cables, but combines piezoelectric sensors, adapter amplifiers, A/D converters, memory, control circuits, interface circuits and batteries to form an independent test system. It can withstand high impact acceleration, high ambient temperature and ambient pressure; it can be directly placed in the body under test, record the signal during the working process of the body under test, and then take out the device to read and process the data with a computer. The pressure gauge has the characteristics of small size, low power consumption and high precision. It is precisely because of the outstanding characteristics of the reconfigurable data storage pressure gauge that it is widely used in explosion power tests. However, the data processing software function of the pressure gauge is very limited. The software can only display the waveform and simply read the collected overpressure data one by one, which cannot meet the needs of in-depth analysis of test data in engineering practice. Therefore, it is necessary to redevelop the software so that it can quickly read the collected data and make further analysis and processing. MATLAB is a high-performance numerical calculation and visualization software that integrates numerical analysis, matrix operations, signal processing and graphic display. As a developmental programming software, it is widely used in system modeling and simulation, scientific and engineering drawing, and application development. In terms of graphical user interface design, it can use M files to create graphical user interfaces (GUIs). At the same time, it also provides a convenient and efficient user interface development environment (GUIDE), which integrates all user controls supported by GUIs and provides methods for setting interface appearance, properties and behavioral response methods. Using GUIDE to create GUI objects has high execution efficiency, can interactively layout components, and can also generate corresponding files for saving and publishing GUIs. Since MATLAB has unique advantages in interface development, this paper uses MATLAB language to carry out secondary development of the explosion shock wave overpressure tester data processing software.

1 Data Reading Programming
For most users, the MATLAB functions load and save provide sufficient tools for loading and storing data. Using file names ending with the extension .mat, load and save assume that the data is saved in a platform-independent binary format or in a so-called flat ASCII file format. When the file format is not flat ASCII or .mat, MATLAB provides low-level file I/O functions based on the C language. With these low-level file I/O functions, MATIAB can read and write any file format.
The data processing software of the pressure gauge stores the acquired data in the .dpr format by default. This data format is not a data format that MATLAB can read directly, so it is necessary to use MATLAB's low-level file I/O functions to read the acquired data. Usually, when using MATLAB to read a file, it is necessary to know the length and storage precision of the file data to be read, and the storage status of the .dpr format test data is not clear in advance, so it is necessary to try to read this file with different precision formats. Through interpretation, it can be known that this file needs to be read in three formats: '*char', 'long' and 'short'. The data read in the 'short' format is the 4 194 304 overpressure signal data collected. Figure 1 is the reading process of the .dpr file. Among them, P is the overpressure data collected by the pressure meter, and T is the collection time corresponding to the overpressure data.

Figure 2 is a comparison chart of the overpressure data read by the program and the overpressure data read by the pressure gauge's built-in software. The upper part is the overpressure data read by the pressure gauge's built-in program, and the lower part is the overpressure data read by MATLAB programming. It can be seen that the overpressure data read by the MATLAB program is completely consistent with the overpressure data read by the pressure gauge's built-in software, so the collected overpressure data can be further analyzed and processed.

2 Graphical user interface development
Graphical user interfaces (GUI) are a user interface composed of objects such as windows, cursors, buttons, menus, and text descriptions. Users select and activate these graphic objects in a certain way to achieve functions such as calculations and drawing. If the required data analysis program is relatively simple, then the production of GUI is generally not considered. However, if you need to provide an application to others, conduct a demonstration, or create a special tool that can be used repeatedly and is easy to operate, then the graphical user interface is one of the best choices. [page]

Since the overpressure test requires a program that is easy to use, fast, intuitive and simple to operate, this paper designs a corresponding graphical user interface for the .dpr file reading program of the overpressure tester. In MATIAB, the command figure is used to create a graphic window. Each execution of the figure command generates a graphic window, and these windows are automatically assigned a handle. There are a series of objects in the graphic window, each object has a handle associated with it, and each object can set and change properties. In the graphic window, objects such as the coordinate axis and the user interface are child objects of the graphic window, while lines, texts, surfaces and images are child objects of the coordinate axis. Each parent object can contain one or more child objects. All created objects will be automatically created first when the parent object exists. Figure 3 is the interface of the designed overpressure tester data analysis program. When using it, you only need to input the sensor number, the distance of the sensor relative to the explosive device, and the address where the test data is stored. The program can read the test data of all pressure instruments in the test at one time, and can automatically judge the peak value of the overpressure measured at each distance, calculate the positive pressure action time, impulse of the shock wave, and the average speed of shock wave propagation. In this way, the basic parameters of the explosion shock wave are obtained, so that the power of the explosion shock wave can be further evaluated.

3 Application Examples
In order to verify the practicality of the program, the program was applied in a free space TNT static explosion test. Test conditions: the mass of TNT is 35kg, the explosion height is 1.2m, the detonation method is two-end detonation, and 16 reconfigurable data storage pressure gauges are arranged in two ways at 5m, 6m, 8m, 10m, 12m, 14m, 17m, and 20m away from the projection center of the explosion point.

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After detonating the TNT explosives with a detonator, the reconfigurable data storage pressure meter is used to collect the explosion shock wave of the TNT. After the signal acquisition is completed, the pressure meter's built-in software is used to access the data stored in the pressure meter, and then the collected data is analyzed and processed using the development program to obtain the main power evaluation parameters of the shock wave generated by the explosion. Table 1 lists the main parameters of the explosion shock wave overpressure calculated using the program, Figure 4 shows the waveform of the explosion shock wave collected by the pressure meter at different distances, and Figures 5 and 6 are the curves of the overpressure peak, the average propagation speed of the shock wave, the positive pressure action time, and the impulse change with distance, respectively.

From the above charts, we can have a clear and intuitive understanding of the measured data of the TNT explosion shock wave, and from Figure 6 we can see that the data measured by the pressure meter at 10 m is not valid data, because the positive pressure action time and impulse measured at this point are abnormal.

4 Conclusion
(1) Through the analysis of the data format stored in the pressure gauge, the test data of the pressure gauge was read using MATLAB, and according to the actual test requirements, a data reading and analysis program based on a graphical user interface was developed. The program has good human-computer interaction and can analyze and process the measured data simply and conveniently.
(2) After practical application, the program can quickly and accurately judge the power evaluation parameters of all test points in an explosion, eliminating the complicated procedures and human errors in manual interpretation, saving time, and intuitively judging whether the measured data is valid, which is conducive to accurate evaluation of the explosion power.
(3) This program is based on the GUIDE template in MATLAB7.0 and has good scalability. In future applications, the functions of the program can be further expanded according to different requirements, such as digital filtering before data reading.