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Test Systems Evolve with PXI Amplicon

Amplicon has been a supplier of IT and Instrumentation solutions to industry for over 40 years. In recent years, we have seen an increased interest in PXI (PCI eXtensions for Instrumentation) following its launch in 1998. As members of the PXI System Alliance (PXISA), Amplicon has followed and supported the developments PXI has taken over the past years, the latest being PXI Express which follows the adoption of PCI Express as a standard. This architectural development enables measurement data to be transferred to the PC more quickly than the existing PCI bus bandwidth restrictions would allow - achieved by using each of the existing bus connections as a standalone serial channel with the provision for channel multiplexing where higher data throughput is required.

PXI is based on the popular Compact PCI (cPCI) standard with its front loading PC controller and eurocard style interface cards. This physical architecture provides a stable, time-tested rugged platform that is ideal for test applications and is easy to use, program and maintain. If a card needs to be replaced, users can hot swap cards quickly providing a very low Mean Time To Repair (MTTR) and which in turn aids diagnosis in complex systems.

The PXI standard adds control features, such as triggering (as found in oscilloscopes) to the PCI functionality, in turn providing synchronisation between the PXI instruments contained within a single or multiple chassis. There is also a reference 10MHz clock source in each PXI chassis for timing control. Alternatively, the Star trigger bus, with equidistant control lines to each PXI module, can be used to negate propagation delays. Separate chassis can be synchronised by using the time portion of the GPS signal data which is connected to the Star trigger lines of the individual chassis, providing precise timing control over distance without the delays inherent in a wired system. This technique has been used successfully within manufacturing environments where multiple PXI systems are used to test a product on a production line where the individual chassis may be separated by a considerable distance, and a timing signal would arrive at each at slightly different times. Using this GPS signal method, the chassis can be accurately synchronised with each other to produce one continuous test sequence.

PXI utilises the same technology as PCI and runs under the same hardware and software platforms, such as the latest Pentium 4 or M processor. This enables users to develop and run their test applications as they would do on a standard PC with Windows or real-time operating systems. The application software then depends on the preference for either a visual programming language like Visual Basic and C++, or a graphical programming package such as National Instruments LabVIEW.

Depending upon on the application, customers can use either the embedded controller or a desktop/industrial PC to run their PXI application. Use of an embedded controller eliminates the need for a separate PC, which in turn reduces the size and eases the use of the test system and would be the ideal solution for a field application. Choosing an embedded controller does not cause any restrictions as they typically come with serial, Ethernet and USB interfaces as standard. For those users who want a PXI system, but who prefer to use a desktop or an industrial PC to accommodate an essential PCI or ISA card that is not available in a PXI version, a PCI to PXI bridge, available from Amplicon can be used. This provides a PCI bridge between the PC and PXI system, so the PXI system operates as though it were inside the PC.

With PXI becoming more accepted in industry, and with growth in this technology sector continuing through downturns in the overall manufacturing sector, there have been an increasing number of suppliers to the market that now boasts over 1100 products, giving customers a greater choice to choose from when building a test system.

Amplicon, for example, represents a number of PXI manufacturers in the UK and has seen new products being introduced at a fast pace. An example of this is the recently introduced Signametrics range which provides a 7½ digit Digital Multi-Meters (DMM) that offers similar, if not better, accuracy to a rack-mount alternative, while using the 32-bit PCI bus to transfer measurements at a much greater speed, thereby increasing productivity for the end user. The range of oscilloscopes now varies from 8-bit resolution, sampling at 2.5GS/s to high accuracy 16-bit cards from Ztec Instruments. A recent introduction to the range is the portable 8-slot chassis with integrated 15” colour LCD and separate keyboard, which is ideal for mobile solutions. Not all traditional instruments are available in the PXI form factor at present, so Amplicon can provide a GPIB interface card that allows integration of a whole solution.

The market largely adopting the PXI standard is the manufacturing industry. A recent application saw a manufacturer of electronic consumables use a PXI system to test and ID the manufactured item. With the PXI system in place, product failures in the field could be traced back to the source for investigation. PXI was chosen in this application because of its high reliability, fast data acquisition, ease of replacement and flexibility.

Amplicon has also seen enquiries from the avionics and military industry. The interest from this market lies with the fact that PXI offers a fast, rugged and portable test solution. An application recently adopting PXI was a military avionics company which required a test system to perform pre-flight checks. The company required that the test system to be deployed and assembled ready for action at a moments notice. Historically, this application could have only been done using a PC with rack-mount instrumentation that would typical tower above most operators’ heads. It always had the uncertainty of whether it would survive transportation in the field, which was not ideal since the equipment plays such a vital role in keeping aircraft operational.

PXI is increasingly the preferred solution for field instrumentation with all the test equipment and controller contained in a portable case with built in keyboard and screen. Previously, customers were faced with the prospect of carrying a PC under one arm, GPIB instruments under the other and cables ‘between their teeth’ which is never the best entrance to make when visiting prospective clients.

It is clear that PXI certainly has its place in the test & measurement world. For those users looking to increase productivity with a faster system or who seek to reduce the size of their test equipment, PXI should always be high on the list of potential options.

If you require more information on Amplicon's PXI product range please click here

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