PXI implementation - the list just gets longer Robert Jackson describes the rapid rise of this modular instrumentation platform standard, which is increasingly being applied to sophisticated industrial automation and data acquisition systems, alongside its more traditional applications in high-speed test and measurement Over the last thirty years, users of test, measurement and automation equipment have witnessed the introduction of several hardware platforms, including bench-top instruments. Traditional bench-top instruments are versatile and widely accepted, but do not match the bus performance of PCI. PC-based instrumentation is attractive because of the PCI bus performance, and support of standard software frameworks. However, desktop PCs lack rugged features and are limited to four PCI slots. With PXI, users combine the performance of the of standard PC-based technology with up to 18 slots in one chassis, and then PXI adds advanced timing and triggering capabilities, support for a wide range of measurement modules and rugged mechanical packaging. PXI (PCI eXtensions for Instrumentation) is a hardware platform built on the CompactPCI specification, but optimised for measurement and automation applications. It was introduced in response to the needs of test and measurement equipment users who seek high performance, functionality and reliability from compact rugged systems. The PXI specification is governed by the PXI Systems Alliance and outlines a standard software framework, enhanced mechanical features and advanced timing and triggering features. It offers the same high-performance electrical features as desktop PCs and CompactPCI, and offers nearly twice as many peripheral slots as desktop PCI systems per bus segment. Thus, multiple-segment PXI can offer far more slots than desktop systems. PXI defines system-level software requirements for standard frameworks, and this software framework, has resulted in much application development. PXI manufacturers of peripheral devices must also include appropriate device driver software, thus eliminating costly and timely development of these drivers by the end-user. PXI also defines that all vendors provide Windows drivers for PXI modules, but this does not preclude the use of real-time operating systems. Many test, measurement and automation applications require system timing beyond the capabilities of ISA, PCI, or CompactPCI backplanes. PXI uses a dedicated 10MHz system reference clock, bussed trigger lines, star triggers and slot-to-slot local buses to address the need for advanced timing, synchronisation and side-band communication. Applications that take advantage of the PC-based performance of PXI and the advanced timing and synchronisation features span the range from data acquisition systems with synchronised I/O to advanced measurements with devices. In addition to a wide range of measurement modules, PXI also integrates motion and vision modules. PXI Systems Alliance PXI was introduced in 1998 as an open industry standard to meet the increasing demands of complex instrumentation systems. Today, PXI is governed by the PXI Systems Alliance (PXISA), a group of 68 companies chartered to promote the PXI standard, ensure interoperability and maintain the PXI specification. These 68 companies offer more than a thousand PXI devices, including analogue I/O, boundary scan, bus interface and communication, digital I/O, DSP, functional test and diagnostics, image acquisition, board prototyping, motion control and RF devices to name a few. PXI is widely adopted among industries ranging from automated test equipment to military and aerospace. Revenues from industrial electronics sector, comprising the ATE and functional test market, recently experienced a quantum leap in growth. Similarly, revenues from the military and aerospace sector rose significantly compared with the overall PXI user base. This trend clearly signifies how PXI is poised to grow. With the adoption of PXI by military and aerospace accounts, and the PXISA promoting the standard, it offers a long and bright future. Not only is PXI an industry standard test and measurement platform; it is also bringing the power of PC-based technology to industrial and automation systems that require advanced control, high-frequency measurements and the integration of motion and vision. Trends for PXI PXI is used across the world to perform predictive and preventative maintenance on rotating machinery, and system users in the manufacturing sector are using the platform to find better ways of predicting machine failure and thus prolong the life of their plant equipment. A trend within the Automation Industry is to demand more power and flexibility without sacrificing industrial ruggedness. Programmable automation controllers (PACs), such as PXI, can meet this need, offering the processing power, speed and standard software framework of PCs, along with the reliability and ruggedness of PLCs. Moreover, PXI supports common operating systems as well as real-time operating systems, and offers hardware integration in one platform for analogue and digital I/O, signal conditioning, motion and vision - with the flexibility to connect to existing control systems. It offers a 0-55oC temperature range, EMC and EMI compliance and the ruggedness necessary to meet 30g shock and 0.31g vibration specifications. By making use of this platform, customers can combine advanced control algorithms with measurements to create powerful and flexible solutions. For more information on the PXI Systems Alliance, including the PXI specification, visit www.pxisa.org Robert Jackson is PXI Chassis product manager, National Instruments robert.jackson@ni.com Back to 25th Anniversary Issue Menu