Functional Testing of High-Voltage X-Ray Tanks

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"The virtual instrumentation-based system was more cost-effective, compact, and easier to use than the previous system. We improved testing productivity by three times and saved even more time and effort during report generation."

- Roy Ignatius, Soliton Automation Private Limited

The Challenge:
Developing an automated test system to perform functional testing of a high-voltage source tank for X-ray generators used in high-voltage medical applications.

The Solution:
Creating a compact and cost-effective PXI-based system using an NI digital multimeter (DMM), oscilloscope, and data acquisition module running an NI LabVIEW application.

Roy Ignatius - Soliton Automation Private Limited

GE BEL, an Indian subsidiary of GE Medical Systems, needed an automated system for testing the functionality of high-voltage tanks, which is a critical component of X-ray machines. We manually conducted nine tests using individual instruments for measuring electrical parameters. Because an operator made the connections every time a particular test was performed, the process was very time-consuming and required operator intervention throughout the tests, which included high voltages of 2,500 V, to change connections and provide room for errors and safety concerns. In addition, we had to manually note the measurements and then transfer them to a computer for report generation.

GE needed a test station that would perform all nine tests with minimal human intervention. The automated test equipment (ATE) also needed to communicate with the existing instruments that had computer connectivity through GPIB or an RS232 interface. We built the ATE on a PXI platform to provide a compact and cost-effective replacement for the large manual test bay. We designed the system to restrict human intervention only to give the connections initially after the system takes over and switches between the various instruments for the nine tests. Also, the ATE generated consolidated reports for GE Six Sigma quality analysis, thereby significantly saving time for GE.

System Description

The automated system acquires data directly using the scope card, the DMM, and the data acquisition module. Data is also acquired from the external instruments using GPIB and RS232 interfaces.

We designed the ATE compactly using an 8-slot PXI chassis with an embedded controller. A PXI switch changes between the different external instruments. We used an NI PXI-6508 digital I/O module in combination with an electromechanical relay module to control switching needed for the various tests. The switching arrangement eliminated the need to change connections after every test. We also controlled high-voltage supplies using the relays through contactors.

In addition, the PXI scope captured the waveforms, and a PXI DMM measured resistances and the high voltage by dropping it across a resistor. We controlled a system leakage tester through the RS232 interface and measured high-voltage capacitance, impedance, inductance, and resonant frequencies using a Wayne Kerr high-precision LCR meter through a GPIB interface, which also controlled a programmable pulse generator to provide waveforms for different tests. The data acquisition module measures the resultant voltages at different points and we compare the results with preset limits.

Furthermore, operator safety was our primary concern due to the presence of high voltages up to 3,000 V. We analyzed all failure conditions and provided additional safety features to assist in harmful situations due to contactor or power failures. Lastly, we developed user-selectable test sequencing so the ATE can generate customized reports at the end of the test. We used the ActiveX features in LabVIEW to directly create the reports in the required Microsoft Excel format.

The virtual instrumentation-based system was more cost-effective, compact, and easier to use than the previous system. We improved testing productivity by three times and saved more time and effort during report generation by using LabVIEW and PXI.

Author Information:
Roy Ignatius
Soliton Automation Private Limited
Classic Towers
Coimbatore 641018
Tel: +91 422 302374
Fax: +91 422 302375

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