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Company Name: Beijing Furui Hengchuang Technology Co., Ltd.

Contact: Manager Gao

Phone: 010-59143021

Mobile phone: 15313875080

Fax: 010-62335265

Email: 3270194537@qq.com

Address: Middle Street, Xiliu Village, Sanfangfang, Chaoyang District, Beijing

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Realization of data processing system of thermal analysis instrument under Lab VIEW

浏览次数:4831 返回列表 Release time: 2016-08-12 Browse times: 4831 Return to list

Hardware development environment The hardware of the new instrument system mainly includes four parts: sampler, data acquisition system, thermal analysis instrument system host and virtual instrument operation platform. The sampler is the sensing part of the thermal analysis instrument. It has a photoelectric detection device to detect the weight change of the balance, and a thermocouple detection device to detect the temperature on both sides of the balance (between the sample side support and the reference side support) to detect thermal analysis. Thermocouple detection device for the temperature in the furnace. The data acquisition system is composed of an analog multi-way switch, a temperature transmitter, an A / D converter, and a 12-bit microcontroller, and is connected to a computer data acquisition and storage system as a virtual instrument operating platform through a serial communication interface provided by the microcontroller. The host of the thermal analysis instrument refers to the composition of the hardware system that provides the test environment of the sample, including the auxiliary structure such as the furnace body, the balance, the differential heating device and the cabinet. Virtual instrument operating platform refers to the computer system and virtual instrument software environment used for data storage, data processing, data analysis, display and control (see).

This research project includes hardware development and software development. Software development is the focus. It mainly implements a set of data processing system that can be applied to WCT, WCR, WRT and other thermal analysis instrument products. Each series is composed of a relatively independent sampler and analysis unit. On the one hand, the software system cooperates with the data conversion interface, and obtains the original test data by connecting with the instrument. On the one hand, the data is analyzed and processed, and the processing results are shown in graphs and tables. Printout.

The key to the hardware part is to develop data conversion and data acquisition interfaces. This part consists of a conditioning amplifier circuit that amplifies weak signals, a heating temperature control unit, and an A / D converter. Finally, communication is realized through the RS-232 serial input and output ports.

The development of the system software makes full use of the rich resources and powerful tools provided by Windows and LabVIEW. The interface is friendly, the human-computer interaction is fast, the operation is intuitive and convenient, and the hardware configuration is guaranteed, real-time sampling control, data processing, curve analysis The speed and quality are satisfactory. Using the characteristics of virtual technology, when developing this system, the test characteristics of the thermal analysis system were mainly improved and improved in the following aspects: single-chip microcomputer acquisition system, providing RS-232 serial port input / output function, and the program was realized through the computer Type heating, cooling, constant temperature and other control systems. Only need to determine the measured value of the sample, the calibration process can be completed automatically by the software.

The data acquisition system and data analysis method are designed in a modular manner, and several parts are interconnected and independent of each other, so that the characteristics of the multi-threaded work of the Windows system can be fully utilized, not only the interface is friendly, the level is obvious, but also the function is further Expand and improve. For different series of products, only the relevant functional modules need to be added and deleted to realize the widening and deepening of the flexible data processing system. 3.3 Thermocouple linearization The V-T characteristic of the thermocouple is nonlinear, and it must be linearized Change. According to the platinum rhodium 10% / platinum thermocouple index table (GB / T16839.11997 thermocouple part 1), establish a T-V corresponding array. When sending the heating parameters, you can directly find the corresponding voltage value according to the temperature. The temperature value is fitted by a straight-line small square method, and the temperature measurement range of the thermocouple is divided into N segments, and the regression equation of each segment is y. This ensures the accuracy of the sampling temperature.

Although the data undergoes low-pass digital filtering in the preprocessing, it is inevitable that some outliers will be superimposed. According to the mentioned "input empty (continued from page 26) written (program omitted): After this section of the program, we got the results of the A / D acquisition of eight channels, which were placed in a piece of RAM with the first address 0454 Area. Because we are using eight-bit precision, the result of each analog quantity acquisition corresponds to an eight-bit binary number, and we also need to convert the binary number to the actual voltage value we need, as follows: (2): VilN ―Indicates the actual voltage collected by the first meter set channel, which is theoretically equivalent to Va / d in formula (1); the limited change between them can only cause the limited change of the output space ”principle, and then the actual instrument obtains the variable change range Determine the appropriate peace order. If the corresponding Xi is included, it is considered that the variable does not exceed If I i is greater than a certain threshold, the data is considered to be outliers. After culling, the principle of small approximation is used, and the approximation point of this i-observed value that has been culled is used for correction processing.

5 One of the advantages of the curve analysis virtual instrument is the analysis and processing of the curve. According to the characteristics of thermogravimetric analysis, that is, not only can select a certain section of the TG curve for analysis, but also change the TG under different time and different temperature conditions of the entire experiment process to achieve the purpose of concise and clear interface and accurate and reliable results.

Compared with the thermogravimetric curve analysis, the analysis of the differential thermal curve is more detailed and complicated. It is easier to meet the requirements by using the "WaveformGraph" graphic display method. At the same time, the function of "PicturePlots" is also used to realize the zoom-in and curve-out of the curve Select, current point curve value and other operations.

The joint curve analysis module realizes the quantized value of the actual voltage of the multi-curve (that is, the eight-bit binary value we obtained).

Now that we have ADCi, according to formula (2), we can calculate Vv with the program, because VilN is equivalent to ViA / D, and then according to formula (1) and the set and adjusted correction coefficient Ai, we can calculate ViR This is the actual value of the analog quantity we want to collect, and convert it to ASC characters, which can be provided to the display program display and other programs.

Using the internal A / D acquisition system of the single-chip microcomputer, it is only necessary to consider the calculation and comparison of the lines of the object to be detected, normalize the curve according to the sample weight, and realize the difference calculation of the two curves and generate a multi-order differential curve.

This research system uses virtual instrument technology as the main method to upgrade the series of WCT, WCR, WRT and other thermal analysis instruments produced by Beijing Optical Instrument Factory, and uses advanced computer technology to improve the development of the original instrument system. It is better than the general thermal analysis system in various aspects such as easy operation, friendly interface and analysis accuracy. It realizes advanced instruments with accurate and reliable testing, simplified operation, convenient maintenance and low cost. The integration of intelligent test and analysis methods in a virtual instrument environment reduces the difficulty and cost of instrument system function changes and function expansion, shortens the development cycle, and provides conditions for rapid implementation and upgrade of instrument testing, analysis, and control. Beijing Furui Hengchuang Technology Co., Ltd.

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