PC-based Test Automation [Sep 2011]

From initial design validation to the final production line, testing electrical or mechanical designs often involves varying a known stimulus and measuring the resulting response. PC-based test automation offers advantages of user-defined I/O and software flexibility to build a test system that meets particular application requirements
Top Five Advantages of PC-based Test Automation• User-defined I/O operation• PC technology for data processing, streaming, and storage• Customisable test sequencing and report generation• Integration with existing systems and instruments• Lower costs with COTS hardware and PC components.User-defined I/O operationMany vendor-defined instruments have fixed-function I/O with a standard set of features to address the majority of measurement needs. As test systems become more complex, the desired I/O functionality becomes more demanding and unique to a specific application. With more than 300 data acquisition devices to choose from, on a variety of PC buses, National Instruments offers the right combination of I/O to help meeting application requirements and define the I/O timing and triggering operations for any test cases you may have. NI-DAQmx driver software includes both high-level functions for standard measurements as well as low-level functions for user access to timing and synchronisation lines. This makes it easy to synchronise input and output lines on the same device, as well as among multiple devices, and create a higher-performance test system.
PC Technology for data processing, streaming, and storageBy taking advantage of the rapid improvements in standard PC technology; progressively faster processing, more memory, larger hard drives, and graphics displays for system visualisation can be achieved — all at increasingly lower costs. These technologies, which are taking PC-based test systems to new levels of performance, will only improve over time.
Today’s standard laptop and desktop computers include multiple processing cores that can be used to implement inline signal processing and analysis. This allows test systems to interpret measurement data in real time and produce results faster without depending on post processing.
Data storage is a valuable part of many test systems because of the need for offline analysis and report generation. PC technology innovation continues to increase the capacity of hard drives while decreasing cost. It’s not uncommon today to encounter standard PCs with terabyte hard drives in them, enough to log data 100 times a second for decades.
One of the biggest innovations in PC technology over the past 10 years has been the performance increase generated by high-speed peripheral buses such as USB 2.0 and PCI Express. Streaming measurement data across these high-speed buses has removed data bottlenecks and drastically improved what’s possible with data acquisition hardware. This has resulted in higher-speed I/O and higher-channel-count systems; all based on industry standard PC architectures.
Customisable test sequencing and report generationAs devices under test (DUTs) grow more complex, testing needs become more demanding. With software-defined PC-based test equipment, one can define custom test procedures to increase the test coverage and reliably verify device functionality. Customisable test sequences can also help decrease overall test times by automating a series of stimulus conditions, analysing the measurement results, and generating test reports. Also, signal processing steps can be added to test sequences for better understanding the measurement data and interpret results.
Test management software such as NI TestStand provides a framework for sequencing, branching/looping, report generation, and database integration. This test management tool provides tight integration with application development environments and helps facilitate code reuse and accelerated development. Integration with existing systems and instrumentsOne may already have instruments that work well for certain types of measurements. A big advantage to using data acquisition hardware on open PC platforms is the number of options available for connecting to existing equipment.
The user can choose from many PC hardware options and free LabVIEW functions for interfacing with major instrument control standards including the following:• GPIB• RS232, RS485, and RS422 serial• USB• Ethernet• IEEE 1394
Over 8,000 instrument control drivers from over 275 third-party instrument vendors are available for download from the Instrument Driver Network.
LabVIEW that makes it easy to reuse existing test equipment and create hybrid test systems with data acquisition hardware and specialised instruments. Lower costs with PC components and COTS hardware
Multiple processing cores, gigabytes of RAM, and terabyte hard drives were formerly thought of as components in a super computer, but they are now commonly found in standard consumer PCs. The PC industry continues to increase performance while driving down costs, and PC-based test systems are taking full advantage of commercial technology innovation. In addition, one can upgrade different parts of a PC-based test system over time and realise incremental performance improvements without having to redesign the entire system.
With hundreds of PC-based I/O options to choose from, the right hardware can be selected to meet budget and performance needs, from low-cost USB devices to high-performance PXI Express systems. By using commercial off-the-shelf (COTS) data acquisition hardware, the large initial investment of custom designs as well as long-term maintenance costs can be avoided. As higher-performance data acquisition I/O becomes available, you can easily migrate to new products and maximise software reuse to shorten development time.l

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