Using National Instruments hardware, NI Gold Alliance Partner G Systems developed a LabVIEW and Test Executive based system to perform real time measurements and calculations. The system accelerates data collection, reduces errors, and automates calculations and report generation -all of which improve efficiency and profitability. Test sequences were created using Test Executive editor to perform waveform qualification, PWM waveform qualification, Voltage level detection, Terminal Block PCB check, Motor Auto-Restart check, Earth Fault Check, Motor and Fan circuit tests.
Toshiba manufactures single phase and three phase uninterrupted power supply units at their Houston facility. These units provide a good way to preserve equipment and data during power disturbance. The power range for the units manufactured at the facility are 0.6-50 KVA. The high power range makes it imperative for the in-house testing of the PCB boards used in these units to be automated with minimal user intervention. Acquiring data and controlling /sequencing tests to measure different trigger parameters, communication protocols and automated waveform validation in modular and integrated manner called for the use of a virtual instrumentation test system.
The test system would use NI based PXI Instruments and the functional board tester developed by Southwest Test. Software needs were to control power supply output, communicate with PCB through serial communication, use oscilloscope to read waveforms, use DMM to read voltage readings and MUX relay board to programmatically facilitate routing needed to obtain reading at a high rate and expand the capacity of DAQ device to handle large number of channels. The PCB boards and their respective modular functional testers change with production needs. The software needed device level modularity to facilitate rapid and easy creation of test sequences to add new tests with changing PCB / Functional modules.
Since the test system needed to be rugged and portable with the ability to fit on a rack-type arrangement, NI PXI instruments were used. To take care of the various measurement needs the NI PXI DMM, Oscilloscope and MUX boards were chosen. We chose National Instruments hardware for its easy installation and integration with the test software. In addition, it was possible to do all development work off site without interrupting the normal testing.
G Systems chose Test Executive Toolkit to develop the sequencing software. It was the ideal choice for this project since the requirements called for quick development time, flexibility to change sequences, ease in creating and editing sequences. The ease of integrating LabVIEW code into the sequences was also a strong factor. The modular device level wrapper drivers for serial, power supply, mux, dmm, oscilloscope were created using LabVIEW. These wrapper drivers leveraged off the IVI drivers (DMM & MUX) available from National Instruments. These drivers wrapped the required functionality of each of the instruments and presented a uniform interface to the Test Executive. Based on the basic functionality of each instrument sub-sequences were built, which were arranged to build Test Sequences. By using LabVIEW, no extra development time was devoted to creating standard objects such as graph displays or user interface buttons. Developing a convenient user interface and linking to the hardware were easy tasks with the power of LabVIEW. The operator user interface provided by Test Executive was modified to display test relevant data on the GUI. The report generation was automated to present data in the form required by the customer. The data file was also stored as an INI file for recalling and use by different programming environments. The data files can also be opened for quick review in the GUI.
The automated test system's main benefit to its users is its speed and accuracy. Encapsulated top level drivers were created to interact with the switch matrix, oscilloscope, DMM, and serial port. The result included a dynamic reduction in testing time and user intervention. The need for skilled technician was greatly reduced with automated analysis. User intervention was reduced from 21 times to 1 time at the onset of testing thus reducing risks involved with high voltages. Reports generated automatically with each test and provide a good reference of the results, and the modularity within the code provides great flexibility to integrate new PCB products with no change in code.
By using virtual instrumentation to automate the process of testing PCB boards we are able to improve reliability, accuracy, and speed. The system was easily made rugged by using a National Instruments PXI instrumentation. With improved testing efficiency, we are able to decrease test time, make better decisions about PCB Board failures, and thereby increase product reliability, quality and company profitability.
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