Pickering Interfaces' Blog - Insights into Switching Technology

How PXI Can Solve Your Toughest Test & Measurement Challenges

Posted by Kim Otte on Apr 30, 2015 1:37:55 PM

new-technologiesTechnology - who can keep up? New applications are announced daily, and many more already in our cars, PCs, appliances, and home theaters that did not exist a short time ago. Every year, products and systems with more intelligence and convenience are available, usually at a lower cost than previous models. The basic premise of our market driven economy is the need to create new products that people will purchase – essentially, technology drives the economy. And don't we all like new technology!

But just as technology progresses, test technologies and their implementation strategies must change as well. Today's test requirements include factors such as increased simulation of sensors, fault insertion, higher data rates, and increased precision. All of these factors must be accomplished while simultaneously increasing test throughput and lowering costs. While these electronic test strategies have always been a tough challenge for our industry, it seems to be a more daunting prospect to support today’s technology.

1000-pxi-modulesFortunately, the Test and Measurement industry has been developing new solutions to address these needs. In many cases, the solution has been the PXI (PCI eXtensions for Instrumentation) modular instrumentation architecture, which has shown itself to be a remarkably flexible platform. Over the last 17 years, the sixty plus members of the PXI Systems Alliance (PXISA) have continued to innovate and create modules that can address the newest technologies. Unique test and measurement solutions are being developed in PXI that are not available in other test platforms.

Why is PXI Successful?

Some of the reasons for PXI’s success are obvious. Many vendors, many more products, and many previous applications successes are key reasons. But looking beyond this, there are other reasons for success.
  • Choices in Software – Many programming languages, including Real Time Operating Systems, as well as focused software for applications like HILS (Hardware In the Loop Simulation) make implementing PXI easier.
  • Connectivity – The best hardware is useless unless you can connect it to the UUT (Unit Under Test). Fortunately, there are vendors who have created mass interconnects that work well with PXI.
  • Vendor Creativity – The small size of 3U was seen as a detriment back in 1997 when the PXI specification was released. It was felt that the small size, especially when compared to VXI, would limit the bandwidth and density that could be achieved. Fortunately, the naysayers were wrong! Switching densities of 4,000 to 8,000 relays in a single matrix, 1,000 volt isolation, and RF instrumentation of up to 26 GHz and greater are just a few examples of what is possible in PXI.
  • Ability to work with other test platforms – In many instances, hybrid test systems are the norm. This can be for reasons like—availability of test and measurement equipment, test budgets forcing hardware re-use, and partial re-hosting/upgrades of existing test systems. PXI has been shown to work well in these environments.
  • System Integrators – This segment of the test industry has embraced the PXI platform as a solution for many applications. Their ability to make PXI work is a big part of the success.

But enough talk on the “Why” – let’s focus on the “How”

Because we cannot adequately present applications on every PXI advantage above in the limited space we have, we are going to focus on those applications where specialized simulation of a particular portion of a UUT’s operating environment is necessary for test that could be simulated using PXI. Granted, every test system is a simulator as the system replicates the car, PC, or missile the UUT will ultimately end being part of. But new applications require new simulation techniques, which is what we want to showcase here.

PXI-modules-and-ChassisBelow you will find links to several application case studies where PXI was an important part of the required electronic test strategy and in some cases made the efforts easier. Some of these applications are unique enough that our readers may not normally think they would require advanced testing techniques, much less any simulation. But in each case, PXI was a major portion of the electronic test strategy.

  • Automotive ECU Fault Insertion - In this case, PXI provides an open platform for HILS requirements. Combining this with the large range of hardware available from Pickering Interfaces and many other vendors, enables the most flexible and cost-effective alternatives to proprietary systems. The modularity and openness of PXI enabled the integrator to design a highly scalable solution with plenty of potential for evolution. Read entire story here >>
  • Satellite Payload Testing - In this case, when specifying hardware for this simulation requirement, a decision was made by the customer not to base it on heritage tools and strategies. Instead, it was decided to take a fresh look at what was available and what was possible, with the goal of choosing an optimally engineered solution within a defined budget.
    The decision was made to base the hardware primarily upon the PXI standard, with Pickering Interfaces as one of the main suppliers. The reasoning behind this decision came down to one statement from the customer: “The solution fitted our requirement, as opposed to our requirement having to fit the solution”. Ultimately, PXI had the right products at the right price. Read entire story here >>
  • Diesel Engine Temperature Simulation - In this case, with various measurement and stimulus modules already available in PXI and a requirement to support RTOS software, PXI was seen as the natural choice of platform for new product design here. The solution developed was a 3U PXI module (model 40-262) that supports either six channels of RTD simulation (in one slot) or 18 channels (in two slots). Read the entire story here >>

In conclusion

From these three applications listed above, it’s clear that PXI products can simulate the signals necessary for a variety of applications, including Consumer, Transportation, and Aerospace. PXI can achieve the densities required to make the system manageable on the test floor, accurate enough to meet customer demands and support specialized environments like RTOS. And, of course, these three examples are simply from Pickering Interfaces’ perspective. Many other test and measurement applications, including others for simulation are being developed by other PXISA members and System Integrators. The key premise you can take from this article is that PXI can very likely address your test requirements – real or simulated.

To learn more about PXI, take a look at our PXIMate book - a guide for those new to PXI systems and a useful source of reference material for the more experienced.

Click here to get your free copy!

Pickering offers over 1,000 PXI modules

While PXI Switching & Programmable Resistors (for sensor emulation) are our main focus, we serve your electronic test requirements in other ways. Our PXI product line includes:

We also offer our eBIRST Switching System Test Tools - tools to help lower the cost of switching system ownership. No other switching vendor offers this level of support for their products.

Have questions about PXI or any of our switching products? Please feel free to contact one of our switching experts today.

About the authors

Shaun Fuller is the East Asian Business Development Manager for Pickering Interfaces. Shaun is based at the company headquarters in Clacton-on-Sea, England. Over the last 25 years, he has held engineering & product management positions within the company. E-mail: shaun.fuller@pickeringtest.com

Bob Stasonis is the Americas/Asia Sales & Marketing Director for Pickering Interfaces. Bob is based in the US Northeast headquarters in Chelmsford, MA. Bob has written numerous papers and articles on the subject of Electronics Test. Over the last 35 years, Bob has held Technical, Sales, and Marketing positions with Pickering Interfaces, Teradyne, GenRad, and Schlumberger. Bob is on the Board of Directors and past President of the PXI Systems Alliance, a Board Member of the LXI Consortium, and a former VP for the American Society of Test Engineers. E-mail: bob.stasonis@pickeringtest.com 

 

 

Smooth & Easy Implementation of Switching Applications
with Signal Routing Software

Posted by Kim Otte on Dec 12, 2014 12:45:06 PM

Switching and routing software helps to provide smooth and easy implementation of switching applications with minimal coding. This article will explain the benefits of using this type of software.

Within small switching system configurations or when utilizing just single switch modules, the user typically applies device drivers with the provided API to control the relays. Simple CLOSE and OPEN commands with additional parameters like module number and channel number control the required relays.

The user must always take care in order to avoid shorts or malfunctions even when performing simple switching tasks. If there are many relays involved, the risk of error increases significantly.

The example below of a 4-wire resistance measurement where a Digital Multimeter (DMM) and the Device-Under-Test (DUT) are connected to the matrix X-axis; turning a simple switching setup into something more complex.

tecap-switching-routing-fig1

For the correct measurement, all four signal paths between DMM and DUT must be properly set, meaning all crosspoints on all four Y-axis’ must be closed at the correct X position. If only one is wrong, it will end up in erroneous measurements or possible shorts to adjacent DUT terminals. For another example, an additional 4-wire resistance measurement takes place on the second matrix. Two 2-pole relays are cascading both matrices by interconnecting Y-bus 1 to 4. Now, even more relays distributed on three different modules have to be programmed properly to achieve a correct measurement.

It is obvious that switching system complexity increases when multiple modules configured and interconnected with each other are carrying signals routed throughout the system. For this reason, switching and routing software, like our Switch Path Manager, takes its role to manage any configuration complexity, yet remains easy to use and always takes safety aspects into account.

Switch Path Manager virtually describes any switching architecture and processes all stored project data for switching and routing at runtime. A multivendor and platform independent switch module library provides the models that are added to the project. In addition, the physical interconnections as well as the endpoints have to be defined. Endpoints are the boundary of the system where measurement and stimuli equipment and all the UUT access points are connected. By calling Point-to-Point or Point-to-Multipoint functions, the routing is processed, and the required relays are controlled to establish a signal path between these endpoints. The router will never interfere with existing routes and will find an alternate bypass or will terminate with an error message if not successful.

Continuing the first example and extending it to a 4-wire resistance measurement DMM to R2 (Channel 2) there are four routes to be established and therefore four CONNECT functions to be called. When using the device driver, 18 CLOSE commands have to be sent to achieve the same setup. Besides the increasing the number of commands, good knowledge of the system is required to understand which crosspoints have to be used.

tecap-switching-routing-fig2.jpg

Switch Path Manager with Auto-Routing

  • Connect Endpoints (DMM+, R2a) - to disconnect: Disconnect Endpoints (DMM+, R2a), etc.
  • Connect Endpoints (s+, R2b)
  • Connect Endpoints (DMM-, R2c)
  • Connect Endpoints (s-, R2d)

Classic Device Driver

  • Close Crosspoints (module1, y1, x1) - to disconnect: Open Crosspoints (module1, y1, x1), etc.
  • Close Crosspoints (module1, y2, x2)
  • Close Crosspoints (module1, y3, x5)
  • Close Crosspoints (module1, y4, x6)
  • Close Crosspoints (module1, y1, x29)
  • Close Crosspoints (module1, y2, x31)
  • Close Crosspoints (module1, y3, x30)
  • Close Crosspoints (module1, y4, x28)
  • Close Channel(module2, ch3) - to open: Open Channel (module2, ch3) , etc.
  • Close Channel(module2, ch4)
  • Close Crosspoints (module3, y1, x4)
  • Close Crosspoints (module3, y6, x3)
  • Close Crosspoints (module3, y7, x1)
  • Close Crosspoints (module3, y8, x2)
  • Close Crosspoints (module3, y1, x14)
  • Close Crosspoints (module3, y6, x6)
  • Close Crosspoints (module3, y7, x8)
  • Close Crosspoints (module3, y8, x12)

If frequently recurring, routes are required it might be more efficient to create fixed routes instead of calling Endpoint-to-Endpoint connections. Those routes can be grouped together to make connecting and disconnecting even simpler. Each separate route holds an attribute called Auto-Route or Static-Route. Thus determining in advance whether a route selects an independent path based on the current switch status or a static one, which might fail if an existing route is blocking the way.

For the R2 4-wire measurement four single routes (R2_DMM-, R2_DMM+, R2_DMMs+, R2_DMMs-) are grouped (GRP_DMM_R2) and switched by single Connect Route Group commands:

  • ConnectRouteGroup (GRP_DMM_R2) – to disconnect: DisconnectRouteGroup(GRP_DMM_R2)

Switch Path Manager handles individual relay control as well: a relay group, which is a group of one or more relays, is called by function:

  • ConnectRelayGroup (RELAYGRP) – to disconnect: DisconnectRelayGroup(RELAYGRP)

For example, relay group RELAYGRP contains the relay channel information of crosspoints Y2/X10, Y2/X11, Y3/X10, Y3/X11.

tecap-switching-routing-fig3


Short Circuit Detection (SCD)

A very important aspect, when applying routing software, is short circuit detection. If not handled correctly, routing might create shorts in a switching system. In the configuration below, there are two switching systems interconnected via a normally closed relay. Now, with an existing route established between A and B, a second route from C to D would cause an unwanted short of the two systems. The Switch Path Manager short circuit detection (SCD) prevents this condition, returns an error message and will not switch this second route.

tecap-switching-routing-fig4
Another more obvious example illustrates the short circuit detection when using multi-pole relays: Two matrices are interconnected on their Y1 and Y2 lines via a 2-pole relay. The blue and green routes have already been switched. Another signal path from X1 left side and X3 right side would allow a route over one pole of the 2-pole relay. However, Switch Path Manager prevents the closing; as on the first pole the green and the blue existing routes would then inadvertently be shorted.

tecap-switching-routing-fig5

Signal Isolation

If the switching system’s signal leads are not isolated, and therefore used for routing, it can lead to unintended connections and therefore to short circuits. The two block diagrams below illustrate this within the following task:

establish two independent connections Y1-Y4 and Y2-Y3.

The router searches for the best-unused path and switches the crosspoints regardless of what is connected. Picture 1 below shows an unwanted connection to the DMM+ and s+ leads, this happens because the router does not know which signals are applied to given nodes. Picture 2 below shows the routes on absolute free paths without any connections to the outside world; this happens because X1, X2, X5 and X6 (used for the DMM) are defined as “isolated” in the system configuration.

                                   tecap-switching-routing-fig6               tecap-switching-routing-fig7

                                                      Picture 1                                               Picture 2

Conclusion

For smooth and easy implementation of switching applications with minimal coding, switching and routing software like Switch Path Manager is unbeatable compared to low-level programming. A good and accurate setup helps minimize the risk of short circuit switching.

The performance speed of routing software should be considered separately. Such systems will always be slower compared to optimized direct programming; this is especially true when used in small switching configurations with one or very few switch modules. However, these delays are small, in the order of milliseconds.

Our Switch Path Manager supports our switching modules and the interconnection between these products; third party products can be supported upon request. Please contact us with any questions.

 


Switch Path Manager - Managing Switching Systems Effectively…

Learn more about  Switch Path Manager  here

 

 

 

Topics: software

Pickering 1000+ PXI Module FAQ's

Posted by Kim Otte on Nov 5, 2014 12:06:00 PM

With over 25 years of signal switching and instrumentation experience, we have learned that when it comes to electronic test –"One Size Does Not Fit All" – that is why we now offer over 1000 PXI modules. 

Below are a list of frequently asked questions on why and how we offer such a large range.


Why does Pickering offer so many modules?

We entered the PXI market in 1998 with just a few modules—since then, primarily through customer demand, our PXI range has grown to over 1000 modules. This has been driven by a number of application requirements including:

  • Number of input and output channels
  • Voltage1000-pxi-modules
  • Power
  • Current
  • Bandwidth
  • Switch time
  • Switching life
  • Switching technology
    • Reed Relay
    • EMR
    • Solid State
    • MEMS
    • Microwave Relay
  • Crosstalk/isolation
  • Budget limitations
  • Low noise
  • Switching configuration and density

These requirements are so varied that test engineers demand a very wide and ever increasing range of solutions. “One size fits all” just doesn’t work in switching for Test & Measurement.

Take a look at our PXI Switching web page, on the left under product navigation it shows a product count for the number of modules available by main category and for each sub-category.

What types of PXI modules are produced by Pickering?

While PXI Switching & Programmable Resistors (for sensor emulation) are our main focus, we serve your electronic test requirements in other ways. Our PXI product line includes:

With so many modules, how can I find the exact one I need?

product reference maps

We have recently redesigned our website so you can quickly drill down to the exact module you need. We also have easy-to-use product reference maps with an overview of our entire range on one sheet.

In addition, we have highly experienced sales and applications people who understand switching and sensor emulation, and are just a phone call or email away

With so many modules, is delivery time compromised?

No. Typical PXI module delivery time is three weeks for almost all module types, often faster if required.

So how does Pickering offer quick delivery for such a large product range?

All module production processes take place in our two factories on flexible, demand-based manufacturing lines. We have complete control of the whole manufacturing process—we do not subcontract any process; everything is designed and manufactured in-house.

How can Pickering possibly offer long-term product support on such a large range?

As stated above, our in-house manufacturing gives us complete product control. From time to time, we update designs to improve performance and reliability while seamlessly managing any component obsolescence issues, all while preserving form and fit compatibility. Typical PXI module lifetime is in excess of 20 years, which is very important for many of our customers, especially in the Mil/Aerospace and Transportation markets.

How can you maintain and repair all these modules?

Pickering offers fast repair on a quick turnaround basis at very reasonable cost.

Built-in Relay Self-Test (BIRST)

In addition, Pickering has a strong background in diagnostics. Modules with our BIRST™ feature can quickly diagnose down to component level. For most other modules, we have our eBIRST™ Switching System Test Tools, this toolset connects externally to the module and can diagnose faults quickly. All of our PXI modules carry a three-year warranty which is unaffected if users choose to undertake their own relay replacement.

Why not just offer software-configurable modules instead of so many different variants?

We do offer several software-configurable modules for customers who require this flexibility. However, these have not proved popular due to the added cost of configuration relays and the inherent disadvantages of lower switching density, reduced AC performance and crosstalk/isolation compromises.

Are Pickering PXI modules compatible with “NI PXI”?

PXImate-practical-guide-to-PXIThis is a common question. Yes, of course, all of our PXI modules are 100% compatible with PXI products from all other vendors, including NI, Keysight and the other 60 members of the PXI Systems Alliance (PXISA).

Interested in learning more about the PXI Standard? Take a look at the article: "What is PXI" or get a copy of the 5th edition of our PXImate book.  Click here to get your free copy!

What about Software?

Our module drivers support all popular software languages, including LabVIEW, Visual Studio, ATEeasy, LabWindows/CVI. We also support Real Time operating systems like Real Time LINUX as well as LabVIEW RT.

Can I use Pickering PXI Modules with other common buses?

Almost all of our PXI Modules can also be used in our LXI Ethernet chassis.

With such a big PXI range, where will I find suitable cabling and connectors?

We don’t leave you struggling to figure out your connectivity. We offer a similarly large range of connectivity options and in addition offer a custom quick-turn cabling/connectivity design and manufacturing service.

We also have strong partnerships with the two mass interconnect companies, Mac Panel and VPC, who have 100’s of off-the-shelf as well as custom solutions.

Does Pickering really understand switching?

We are experts in switching technology. We have been designing and manufacturing modular switching systems since 1988, and our sister company, Pickering Electronics, has been designing and manufacturing instrumentation grade reed relays since 1968.

Switching expertise is in our DNA!

Have additional questions or comments? Please post your comment below or...

Please Contact Us To Learn More

Topics: PXI, PXI Switching, automated test system, test and measurement systems

What is a Programmable Resistor?

Posted by Kim Otte on Aug 25, 2014 3:13:00 PM

A programmable resistor is designed to emulate the use of resistive sensors and variable resistors in systems when testing devices such as engine controllers.

programmable-resistor-chain
Resistor chain used in a typical programmable resistor

In their simplest form, Pickering's programmable resistors consist of a basic chain of resistance values switched in or out of circuit with reed relays, electro-mechanical relays or solid state switches. We also offer multi-channel programmable resistors with very fine value adjustment and high accuracy including programmable resistive bridges for strain gauge simulation.

two-channel-programmable-resistor
Two channel precision programmable resistor with calibration facility

Applications for Programmable Resistors 

Programmable resistors have many applications in automated test, verification and simulation systems: 

  • Strain Gauge Simulation
    • Used in mechanical systems to measure the tension or compression of structural components. Simulation requires extremely fine setting resolution with high accuracy and temperature stability. 
      strain-gauge-simulator-diagram
Strain Gauge Simulator with six channels and calibration facility
  • Temperature Sensor Simulation
    • Simulation of resistance based temperature sensors such as positive or negative temperature coefficient thermistors. 
    • Resistance Temperature Detectors (RTDs) can be wire-wound or thin film. Both PT100 and PT1000 types can be simulated, requiring fine setting resolution. 
  • Pressure Sensor Simulation 
    • For the simulation of pressure senders in mechanical systems or barometric pressure sensors in applications such as altimeters in the aerospace industry. 
  • Select on Test Resistance 
    • A programmable resistor can be used in a test environment where a component's value is optimized at the production test stage. 
  • Load Resistor 
    • Where a circuit under test requires the connection of an external load. 
  • Position Sensor Simulation 
    • Rotary or linear position sensors in mechanical systems usually take the form of potentiometers and are used in applications such as throttle position senders in automotive systems. 
  • Switch Simulation 
    • Can be used to simulate the contacts of a worn or contaminated switch for automotive ECU (Engine Control Unit) testing. 
  • Fault Insertion 
    • Can be used for injecting fault conditions when testing the fault tolerance of aircraft or automotive control systems. 

Selecting a Programmable Resistor

Pickering offers a variety of PXI programmable resistor modules and PCI programmable resistor cards for use in medical, automotive and aerospace applications. We offer different features for use in different applications, these include:

  • Platform
    • Solutions in both the PXI and PCI formats
    • Ethernet control of any of our PXI modules when installed in our LXI Chassis
  • Number of Channels
    • Between 1 and 18 channels
  • Range
    • Many resistance ranges are available with values from a short circuit to millions of Ohms
    • Modules and cards are available with a narrow setting range and very fine resolution for simulating sensors and strain gauges
  • Resolution
    • Resistance setting resolutions are available from 10Ω to 2mΩ for a wide range of applications
  • Power Handling
    • Generally 100mW for precision programmable resistors and up to 1W for standard programmable resistors
    • We also offer a PXI programmable load module with up to 15W power handling (model 40-292)
  • Minimum Resistance Value
    • The lower the minimum resistance value required the greater the errors caused by relay contact resistance and copper trace losses.
    • Generally, modules and cards with a low minimum resistance do not have as wide a range of resistance values as those with higher minimum resistances.
  • Accuracy
    • High accuracy requires careful design to ensure low loss paths, management of thermoelectric EMF and the use of higher stability resistors
  • Calibration Port
    • A calibration port allows the user to check the resistor channel without having to disconnect the front panel connector. It can be used to connect any of the resistor channels to a DMM to perform an accurate four terminal measurement.
  • Custom Programmable Resistors

pickering-programmable-resistorsOur entire range use real resistors, they do not use current loads or other electronic means to control the resistance value. Therefore they behave in exactly the same way as an actual resistor.

We carry over 130 PXI modules and over 120 PCI cards featuring:

  • Up to 18 channels in a single PXI/PCI slot
  • Resistance ranges from 1Ω to 22MΩ
  • Resolutions down to 2mΩ with accuracies down to 0.03%
  • PXI modules can be supported in our LXI Chassis
  • Supported by a full range of connector and cabling solutions

You can also learn more about programmable resistors on our knowledgebase, feel free to contact one of our switching experts for more information or...

  Request your free programmable  resistor reference map here!

A single sheet reference to our range of programmable resistors, including basic specifications and cabling optons.

Topics: PXI, test and measurement systems, PCI, Programmable Resistor

LXI or PXI Switching for Automated Test Systems?

Posted by Kim Otte on Jul 16, 2013 4:42:00 PM

pickering lxi pxi switchingIs there a better platform to use for switching in automated test system? The answer is no, both the LXI and the PXI standards bring different advantages and disadvantages depending on what the user is trying to accomplish. 

For companies that embrace both the LXI and PXI standards for their switching systems, it is a question of what they decide is the appropriate soluition for their application.  PXI and LXI are sufficiently different - there will often be clear cases where one option is better for a particular solution than another.

LXI instruments are largely platform agnostic whereas PXI is very dependent on the PC architecture (and in many implementations, Windows). LXI devices do not have many mechanical or electrical constraints, but PXI products must conform to the PXI standard to benefit from the multivendor chassis platform. They also can have quite different data speed drivers.

In the illustration below you will see some of these differences:

PXI and LXI Comparison

To see more on the comparison of LXI and PXI switching for automated test systems, take a look at this article from the July issue of Evaluation Engineering: 
http://www.evaluationengineering.com/articles/201307/embracing-lxi-and-pxi-for-switching.php

You can also visit our knowledgebase for additional articles on Switching Platform selection:http://wiki.pickeringtest.net/Platform+Selection 

If you want additional information, please feel free to contact us by leaving a comment here or going to: http://www.pickeringtest.com/contact.html  

Do you prefer one standard over the other? Let us know your thoughts.

 

 

 

 

 

 

Topics: PXI Switching, LXI Switching, automated test system

What is PXI? Your Questions Answered.

Posted by Kim Otte on Jun 26, 2013 11:25:00 PM


So you want to learn more about PXI, well you've come to the right place - below you will find a introduction to PXI.

What is PXI - Background and History

PXI, short for PCI eXtensions for Instrumentation, is a rugged PC-based platform that offers a solution for measurement and automation systems. 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 major 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 Systems Alliance

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 is able to 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 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 allows for trouble free multi-vendor solutions to be implemented.

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

Most PXI instrument modules are simple register based products that use software drivers to configure them as useful instruments; taking advantage of the increasing power of computers to improve hardware access and simplify embedded software in the modules. The open architecture allows hardware to be reconfigured to provide new facilities and features that are difficult to imitate in comparable bench instruments. 

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

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:

  • Pickering Interfaces PXI ChassisPXI 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 normally ranges from four slots up to twenty. 

    The chassis are typically designed to house either 3U or 6U PXI modules. 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 a particularly cost effective, but powerful option.

The choice of 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.
 
     
  • Pickering Interfaces PXI ModulesThe Modules - these come in many different varieties including test instruments that take a wide variety of measurements such as voltage, current, frequency as well as signal and waveform generators. They can also perform other functions including boundary scan test, image aquisition, power supplies, switching and more. 

PXI Software

The PXI standard is reliant on a standardized software and hardware environment. Since PXI is based on the PCI standard, many of the PCI 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.  Some vendors support Linux or other OS’ as well, but Windows is the minimum.

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

PXI Market Acceptance

In 2009 the PXISA announced that there were more than 100,000 PXI systems deployed containing more than 600,000 instruments. Today, there are more than 55 PXISA member companies that have produced more than 1,500 different PXI modules. (Source: PXISA web site) As shown in Figure 1, the 2011 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 6 years.  At this rate, the PXI market is expected to exceed 1 billion USD by 2017.

Figure 1 – Projected Modular Instrument Revenues by Standard

Source:  2011 Frost & Sullivan report “High Growth Test & Measurement Market Opportunity: Modular Instruments”

What is PXI Express?

As the commercial PC industry drastically improves the available bus bandwidth by upgrading from PCI to PCI Express, PXI has the ability to 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. 

For an article comparing PXI and PXI Express, please visit our support wiki at: http://wiki.pickeringtest.net/Comparing+PXI+and+PXI+Express 

You can also take a look at the PXI Express Specification Tutorial for more information on PXI Express.

PXImate-practical-guide-to-PXIWant more PXI Information?

Pickering Interfaces has published a book, PXImate, this book provides an overview of the PXI standard together with useful 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 useful source of reference material for the more experienced.

Topics: PXI, PXI Switching