What is PXI? Your Questions Answered.

What is PXI - Background and History
PXI, short for PCI eXtensions for Instrumentation, is a rugged PC-based platform that offers measurement and automation systems solutions. With PXI, you benefit from the low-cost, high-performance, and flexibility of the latest PC technology and the benefits of an open industry standard. PXI combines standard PC technology with the mechanical form/factor from the CompactPCI™ specification and added integrated timing and triggering to deliver a rugged platform with significant performance improvements compared to other test and measurement architectures. 

PXI's mechanical, electrical, and software features define complete systems for test and measurement, data acquisition, and manufacturing applications. PXI has become a dominant industry standard for measurement and automation applications such as military and aerospace, automotive, manufacturing test, machine monitoring, and industrial test. 

The PXI Standard

PXI is governed by the PXI Systems Alliance (PXISA), a group of more than 50 companies chartered to promote the standard, ensure interoperability, and maintain the PXI specification. Because PXI is an open specification, any vendor who joins the Consortium can build PXI products. CompactPCI, the standard regulated by the PCI Industrial Computer Manufacturers Group (PICMG), and PXI modules can reside in the same PXI system without any conflict because of interoperability between CompactPCI and PXI is a key feature of the PXI specification.

The PXI standard defines the mechanical, electrical, and software interfaces provided by PXI compliant products, ensuring that integration costs and software costs are minimized and that trouble-free multi-vendor solutions are implemented.

A PXI system appears as an extension to the peripheral slots in the user’s controller, regardless of whether the controller is embedded in the PXI chassis or is a separate computer.

The PXI modules, which provide the instrument and switching functions, are plugged into a chassis. This chassis may include its own controller running industry-standard operating systems or a PC peripheral slot to the PXI bridge that provides a high-speed link to a desktop PC. 

Depending on the connector types fitted to a module, CompactPCI and PXI products are interchangeable; they can be used in either CompactPCI or PXI chassis; however, installation in the alternate chassis type limits the functionality of certain features.

What is PXI - The System consists of three main components:

• PXI chassis - the chassis is the backbone of the system - it contains a high performance
  backplane giving the cards in the system the ability to communicate rapidly with one another. It also provides power and cooling, and the chassis range from two slots up to twenty. The chassis are typically designed to house either 3U or 6U PXI modules, and the PXI standard supports the design of chassis that allow both 3U and 6U modules. The PXI specification does not set a rigorous standard for what can be included in a PXI chassis, though all must comply with the mandatory parts of the specification. For that reason, PXI chassis vary in their capability, and the user needs to choose the chassis that is right for their specific application.
  
  

• The System Controller- The PXI chassis can use either an embedded controller in the Slot 1 position or an interface module allowing connection to an external controller (such as a PC). The use of a standard PC provides an exceptionally cost-effective but powerful option. The type of PXI controller will vary depending on the application. PXI has sufficient flexibility to enable it to be configured for internal embedded controllers, laptops and desktop PCs.
   
• The Modules - these come in many different varieties, including test instruments that take a wide variety of measurements such as voltage, current, frequency, and signal and waveform generators. They can also perform other functions, including boundary-scan test, image acquisition, power supplies, switching, etc. 
  
  

PXI Software
The PXI standard is reliant on a standardized software and hardware environment. Since PXI is based on the PCI standard, many PCI/PCIe routines can be moved into the PXI environment. The PXI modules cannot be controlled from a physical front panel. Therefore software control via the backplane is required. Minimum requirements are for Window 32-bit drivers, and there is also an extension for supporting Linux.

IVI drivers are optional. IVI Drivers are sophisticated instrument drivers that feature increased performance and flexibility for more complex test applications that require interchangeability, state-caching, or simulation of instruments. To learn more about IVI drivers, please visit the IVI Foundation's website: http://www.ivifoundation.org.

PXI Market Acceptance
The PXISA believes that more than 100,000 PXI systems are deployed, containing more than 600,000 instruments. Today, more than 60 PXISA member companies have produced more than 2,500 different PXI modules. (Source: PXISA website) As shown in Figure 1, the 2021 Frost and Sullivan Modular Instrumentation study expects the PXI instrumentation market to grow at a compounded annual growth rate of 18.1% for the next five years.  At this rate, the PXI market is expected to exceed 1.8 billion USD by 2025.

What is PXI Express (PXIe)?
As the commercial PC industry drastically improves the available bus bandwidth by upgrading from PCI to PCI Express, PXI can meet even more application needs by integrating PCI Express into the PXI standard. To ensure the successful integration of PCI Express technology into PXI and CompactPCI backplanes, engineers within the PXISA and the PICMG worked to ensure that PCI Express technology can be integrated into the backplane while still preserving some compatibility with the large installed base of existing modules. With PXI Express, users will benefit from significantly increased bandwidth, guaranteed backward compatibility, and additional timing and synchronization features. 

Take a look at our Knowledgebase article - "Comparing PXI and PXI Express" 

Want more PXI Information? Check out our PXImate eBook.

This book provides an overview of the PXI standard and helpful information about the technology behind the switching and instrumentation modules a typical chassis can contain. It is a guide for those new to PXI systems and a valuable source of reference material for the more experienced.