Introduction: Most of the air conditioning tests in the past were tested for several functions of a single station, such as water-cooled cold water test, fan coil test, enthalpy test, and heat transfer test. With the increase in market demand, the production scale of air-conditioning enterprises has expanded correspondingly, and the requirements for testing have become higher and higher. More and more test benches need a set of test data management system for centralized testing and remote monitoring, effectively utilize existing test equipment, improve the utilization of test equipment, and fully utilize the functions of hardware to facilitate the effective use and analysis of personnel in different departments. A large amount of test data, cross-sectoral test data sharing, and effective management of test data between different departments.
System plan
Figure 1 System structure
Data acquisition equipment (DAQ Devices) and acquisition computer (DAQ Server) for hardware connection communication (supports a variety of bus type connections, such as GPIB, PXI, USB, RS232/485, etc., all communication protocols supported by LabVIEW can be collected to the acquisition computer on).
Data acquisition is performed by a LabVIEW data acquisition program installed on the acquisition computer. Any authorized client computer (Client) in the network establishes a data connection through the TCP/IP communication and the acquisition computer, obtains the data it needs, performs post-operation analysis, and finally saves the data to the data server through the TCP/IP network (Data Server) in the database. The client program can be installed on any authorized computer in the network to perform real-time data collection and analysis processing, and the historical data in the data server database can be analyzed and processed through the TCP/IP network.
2. System functions mainly include the following parts:
Data acquisition program
Customers are required to take full advantage of the original equipment and take advantage of the superior performance of the newly added NI PXI system. To have good compatibility, you can add new hardware acquisition functions to the data acquisition program by adding device drivers after adding hardware devices in the future. The data acquisition program is used for communication and data transfer between the data acquisition device and the acquisition computer. In this program, the data acquisition device can be set and selected, and each data acquisition channel is configured, such as a thermocouple or a platinum resistor. , voltage, current channel configuration, etc. The data obtained by the data acquisition program sends data to each client computer by establishing a TCP/IP connection (this client computer can be any computer on the network), so that the computers of other stations can read the data of the respective stations. If there is a network problem, you can run a client program on the acquisition computer and save the data to the local computer for a station test.
2. Test Wizard
Through the test wizard, you can complete unit type selection, test information input, acquisition channel configuration, channel template management, virtual channel management and other functions.
The unit type selection includes water-cooled chillers, air-cooled chillers, unit machines, multiple connections, compressors, heat exchangers, etc. When there is a new unit type, the user can customize the unit test type.
3. Display graphics in real time
The user can freely select the channel combination for real-time display of the curve.
4. Account rights management
The system has certain permission functions, including the following levels (users can also create new permission functions as needed):
l Visitor: View historical test data;
l Operator authority: Input settings for some test parameters;
l Team leader authority: You can change some calculation formulas, etc.
l Test engineer authority: all functions of the software can be used, but the source program cannot be entered or changed;
l Software administrator privileges: All operations can be performed including source program modification.
5. Data comparison
The data in the historical data can be compared graphically. Used on the same type of test for the same station. Users need to play a certain role in the similarity comparison, repeatability comparison and other occasions of the same test.
6. Historical data query
Through the Database Connectivity database toolkit, the data obtained by the client computer can be stored in the data server (with database software such as MSSQL, Oracle, MySQL, MSAccess installed). Then, the historical data in the data server is read and analyzed by the client computer software.
7. Report output
By using the Report Generation report generation toolkit combined with Microsoft Excel, users can create a report template by themselves, or select a template to create a corresponding location in the Excel template, and then output the Excel report. The user can define the conditions for outputting the report, first determine the parameters and conditions for determining the stability. After all the parameters have reached the stable condition and stabilized for a period of time after the program is running, the report can be output to the specified file path.
8. Sensor database
In the air-conditioning test, there are a large number of sensors used, and they need to be regularly calibrated after a period of use. However, due to the large number, a sensor database is needed to facilitate effective management and tracking in time after calibration. Therefore, a sensor database module was designed. The detailed information of the sensor can be recorded therein: station number, serial number, correction device name, correction device number, correction method, correction date, revision person, reviewer, correction formula coefficient, etc., and this database file can be maintained and set. Information on all test bench sensors is easy to select when testing.
Figure 2 sensor database interface
3. System advantages a. Software development advantages
Customers have previously commissioned other units to adopt VB, and Delphi has developed several sets of test procedures for a fixed station. Each station software development time is more than a few months, and it is functionally difficult to meet the changing requirements of customers. This system software is tested for all air-conditioning test stations throughout the plant and can be used in most stations. The development time has been reduced from the original few months to several weeks, and the functional modules are continuously updated according to the changes of customers' needs.
Figure 3 Plug-in
The data acquisition program takes the driver of each device into a plug-in form. If a new test device is added later, it only needs to be written according to a fixed input/output template and then placed in the specified plug-in directory ( Support\Plug-in), you can implement new test functions. The plug-in form uses VI Server technology. By calling the device driver VI in the plug-in directory and writing the device acquisition parameters in a fixed mode, the collected data can be output.
Figure 4 VI Server
Network acquisition analysis is easily achieved by using TCP/IP communication. In the past, traditional data acquisition generally used GPIB, RS232/485 and other traditional fieldbus methods, it is difficult to achieve long-distance data acquisition. By using the VISA support for TCP/IP in LabVIEW, combined with the stability of the modern factory network, the long-distance data acquisition function can be fully realized. And expand this function to achieve centralized monitoring and management of the test bench of the entire plant. NI Example comes with TCP/IP communication as follows:
Figure 5 TCP/IP Server Block Diagram
Figure 6 TCP/IP Client Block Diagram
TCP/IP communication can be developed based on the above routines and using the following communication strategies:
Figure 7 TCP/IP Server TCP/IP Client
In terms of user interface, LabVIEW integrates a lot of beautiful controls, which can be adjusted on-the-spot according to user needs, quickly get user feedback, reduce development time, and create a beautiful interface that meets user needs. As shown below:
Figure 8 test interface
b. Hardware development advantages
In the past, traditional test equipment was often very cumbersome, occupies a large amount of test space, and transportation is also very inconvenient. Communication is based on traditional methods such as GPIB, VXI, RS232/485, etc., and the sampling rate is low, which is difficult to meet the requirements of rapid data acquisition. With the NI PXI solution, due to the small size of the PXI, it takes up a lot of space. And the PXI bus has a higher communication speed. For example, with the PXI-4071 digital multimeter/digitizer/oscilloscope + PXI-2503 matrix/multiplexer scheme, the PXI 4071 can achieve a sampling rate of 1.8 MS/s, and the PXI-2503 can be as fast as possible. The switching rate of 200Cycle/s is realized, and the time required to acquire a circle is in the millisecond level. However, the sampling of a conventional device often takes several seconds, which cannot meet the requirements of rapid data collection.
Figure 9 live picture
As can be seen from Figure 1 and Figure 9, the installation and debugging of the hardware is more convenient after the introduction of LabVIEW and NI hardware. In addition to traditional test equipment, additional conversion equipment is required to complete these tasks. With NI hardware combined with LabVIEW and the corresponding toolkits and communication modules, a data management system that enables centralized testing and remote monitoring can be quickly built.
Through the comparison of these advantages, LabVIEW and NI hardware have broad application space in the air conditioning test industry. To change the traditional test method to the advanced virtual instrument test method.
Conclusion By using NI LabVIEW software, we can quickly tailor a software product to meet your needs. Compared with the traditional development method, it not only improves the programming efficiency, but also saves the customer communication time and improves the communication efficiency, so that we can better provide customers with software products that meet the requirements of high quality. The seamless integration of LabVIEW and NI hardware on the hardware saves a lot of hardware development time. In the past, writing software drivers for a board or module was a very time consuming task and required a lot of debugging work. Moreover, the stability is not well guaranteed. After using NI hardware, the stability is greatly improved, the development time is reduced, and the sampling points and sampling rate are greatly improved. It is foreseeable that LabVIEW and NI hardware must have more extensive and in-depth applications in industrial measurement and control.
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