Pickering Interfaces' Blog - Insights into Switching Technology

The Challenges Surrounding Switching for Automated Test Systems

Posted by Kelly Porter on Oct 3, 2019 10:35:27 AM


challenges-surrounding-ate-whitepaper-image

Automated test systems rely on the performance, quality, and configuration of the signal switching that they are based on, yet the most significant challenge when considering switching for automated test systems may not be technical at all. Often we hear from customers that they feel switching is the last portion of their test integration strategy that needs to be considered. Switching is so simple, maybe even boring… how can anyone go wrong?

Think about the questions you should ask yourself surrounding switching for automated test systems such as:

  • What is a the importance of high-quality switching?
  • What are the differences between reed relays, electromechanical relays and solid-state relays?
  • What types of switching configurations are available?
  • Which cables, connectors and mass interconnect products should be included with my switch module?

The switching system is intrinsic to the success of the test process, so it’s important to understand the possibilities and limitations. However dull switching may seem, there are very many challenges to be considered, but the information is all here to help you. To learn more on this subject, check out our newest white paper here:  The challenges surrounding switching for automated test systems

To learn more, take a look at our updated SwitchMate Book or if you have questions please contact us.

Topics: PXI, automated test system, test and measurement systems, PCI, Programmable Resistor, sensor simulation in test

Understanding Programmable Resistors for Sensor Simulation in Test

Posted by Kim Otte on Oct 25, 2018 12:58:49 PM

If you think about it, sensors control much of our daily lives. Sensors ensure that the food in your refrigerator stays cold, programmable-resistors-image-for-whitepaper-lpcount your steps on a smartphone, and even protects you in an automobile accident. So many devices in our personal lives as well as in business and other markets contain sensors.

All these sensors add a layer of complexity to your test strategy, as you need to simulate them when testing the circuit board that makes decisions based on a sensor’s response. Since it is usually not practical to incorporate actual sensors into a test fixture, Pickering Interfaces has created external hardware that is designed to replace these sensors in a test program. In this paper, we will talk about sensor simulation and how to select these products. With Pickering’s history of more than 15 years designing programmable resistors, we have the expertise and product depth to play an important role in testing sensor-driven products.

Learn the right questions to ask when testing sensor-driven products.

  • What is a programmable resistor and why is it used for sensor simulation in test?
  • What are the different types and parameters for programmable resistors?
  • What if I need more accuracy in my test?
  • Are there different types of configurations I can use?

As you can see, there are many things to consider when selecting programmable resistor modules in test. It is undeniable that sensors are in virtually every application for electronics, making testing important, and sensor simulation can help you get there. We recommend you take a look at our latest whitepaper -

Understanding Programmable Resistors for Sensor Simulation in Test

To learn more, take a look at our web page: Programmable Resistor Solutions for Sensor Simulation or contact our simulation application engineers.

Topics: PXI, automated test system, test and measurement systems, PCI, Programmable Resistor, sensor simulation in test

Moving Your Test & Measurement System from VXI  to PXI : Not If, But When

Posted by Bob Stasonis on Oct 31, 2017 9:21:02 AM

Moving from VXI switching to PXI switchingIn its day, VXI technology was a definite step forward. Built upon the modular VME computer bus, VME eXtensions for Instrumentation, or VXI, reduced the size and increased the performance of high-end test systems. Instead of bulky rack-and-stack systems, whose instruments were connected by the relatively slow GPIB interface, VXI systems featured modular instrumentation that plugged into a modified VMEbus that provided higher data transfer rates and real-time performance not possible with rack-and stack systems.

The VXIbus has served test & measurement engineers well, but it is more than 30 years old now, and it may be time to move to a more modern platform. Today, more test systems designers are choosing the PCI eXtensions for Instrumentation (PXI) platform when designing new modular test systems or replacing or updating existing test systems. Originally introduced in 1997 by National Instruments, PXI is now supported by nearly 70 companies working under the umbrella of the PXI Systems Alliance (PXISA), which publishes the PXI specification and ensures instrumentation interoperability.

PXI's main advantages: availability and lower cost

PXI's biggest advantage over VXI is product availability. In the nearly 30 years since VXI was introduced, the Consortium that manages the specification has gone from over 40 companies down to just eleven members. Even Pickering has dropped their VXI line due to key part obsolescence and reduced market requirements. A large number of the products that were available in VXI in the past are now obsolete and are often only available on the used market. That is not to say that VXI is no longer viable. In some specialized applications like Data Acquisition, there are VXI vendors producing new products. In other applications, VXI is mostly recommended for legacy applications and not for new designs.

A second reason to look closer at PXI for your test & measurement needs is that hardware costs are lower than VXI. Because PXI is based on the PCI bus, which is used in many personal computers, it can take advantage of the advances being made to serve the PC marketplace. Because many of the components used in PXI modules are also used for PCI modules, they cost less because so many more of them are made. This leads to overall reduced cost for PXI modules when compared to VXI modules. PXI systems typically cost one-half to one-third the cost of an equivalent VXI system.

Some of the other advantages that PXI enjoys over VXI include:

  • Data transfer. Standard PXI can transfer data that is 8, 16, 32, or 64 bits wide. VXI can only transfer data that's 8, 16, or 32 bits wide.
  • Data throughput. Because PXIe (Express version of PXI) systems can transfer data over high speed serial busses, the maximum throughput for PXI systems is higher than that for VXI systems. The maximum throughput for VXI systems is only 160 Mbytes/s, while the maximum throughput for PXIe systems is 12 Gbytes/s.
  • PXI modules are smaller than equivalent VXI modules. In fact, PXI systems have the smallest footprint of any open-architecture instrumentation system. This is a big advantage for PXI test systems because as test systems become more complex, test system developers need to cram more functionality into their test systems. PXI lets them do this while at the same time keeping test system size manageable.
  • Instrument availability. Aside from perhaps some very specialized instrumentation (an example would be Bustec with their specialized data acquisition systems), whatever you can buy in VXI, you can also buy in PXI. And, the trend is clear. There are fewer new VXI modules being developed than new PXI modules, and that will continue into the future as more designers specify PXI over VXI. In some applications, such as fault insertion during simulation, there are no VXI modules available. Also, because PXI is based on the CompactPCI specification, you can use CompactPCI boards in a PXI system.

Making the right choice

While the availability of PXI switching and instrumentation modules makes the choices relatively easy, there is the issue of migrating test programs from VXI to PXI, specifically in switching applications. The ability to replicate original test configurations to support legacy FRUs (Field Replaceable Units) is important to continue supporting older test programs while planning for future requirements.

To help ease this transition, we have developed PXI switching and simulation modules that closely match the operation of VXI switching modules from Racal, VTI Instruments, Agilent (Keysight), and other manufacturers. And, our policy of supporting our PXI Switching products for 15 to 20 years, or even longer, means that your next-generation test systems will have as long a life as their predecessors. An example of our VXI to PXI can be seen below.

Pickering's VXI to PXI switching cross-reference.

Our PXI modules listed in the table above are in many cases a close equivalent to the VXI modules. Because of the large PCB real estate of C-Size VXI modules, channel counts may be different, and specifications may not be exactly the same. Depending on your application, a different Pickering PXI module may be closer to your requirements than what is shown here. We also have cross-references to other manufacuturer's VXI switching.

Take a look at our VXI to PXI Cross-Reference here

Please contact our support team for more assistance in finding the correct module for your requirements.

Migration issues

While PXI is clearly the modular platform of choice when designing new test & measurement systems or upgrading existing systems, you may encounter some issues when doing so. One of them is module real estate. Clearly, a C-size VXI module has a lot more area to mount components, meaning that some VXI modules may have more features or functionality than a PXI module that you might choose to replace it. On the whole, however, VXI module designs are not as dense as today’s PXI module, so this is usually not an issue.

A related issue that you will have to address when migrating to PXI is cabling. VXI modules have a wider front panel (1.188-in.) than PXI modules (0.8-in.), meaning that many of the connectors used in VXI systems cannot be used in a PXI system. So, plan on building or buying new cables or buying adaptors.

If your instruments dissipate a lot of power, you may have cooling issues when migrating to a PXI system. The PXI cooling spec is less stringent than the VXI specifications, and generally, PXI chassis do not have the cooling power of VXI chassis. You may use multiple slots to achieve the necessary cooling.

Software is another area of concern. There is no easy way to migrate test programs. But, given the number of good test-development software packages available for the PC platform, this may not be as big an obstacle as it might appear.

Despite these drawbacks, if you're an automatic test system developer, the question is clear. It's not if, but when you should move to PXI-based systems from VXI. The answer is pretty clear, too. The answer is now.

Let us know your thoughts on moving from VXI to PXI.

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

LXI Switching- Everything You Want to Know And More!

Posted by Kelly Porter on Apr 20, 2017 3:37:09 PM

LXI Switching Products

Sometimes it seems like PXI is all the talk of the test and measurement industry. But, let's not forget about LXI and its solutions to your switching needs that you may not be aware of.

LXI Switching has come a long way since the LXI standard its introduction over 11 years ago and its popularity is becoming more prominent with the introduction of new products and capabilities.  There has been speculation that PXI and LXI are competing standards, but that is a view that we do not share. They are sufficiently different, and there often will be clear cases where one is better for a particular solution than another. Both the LXI and the PXI standards bring different advantages and disadvantages depending on what the user is trying to accomplish. So, let's talk about LXI Switching and how far it has come since its introduction in 2005.

That brings me to my first (obvious) question, What is LXI? LXI is the power of Ethernet and the Web applied to Test & Measurement (T&M) instruments, offering you new possibilities in test systems – local, remote, distributed and time-aware. LXI products are certified by third-party test routes to ensure they comply with the worldwide LXI standard. Today there are thousands of compliant instruments which have passed LXI conformance testing, and every one of them lets you use the connection you already have.

The use of switching systems to route instrumentation and stimulus signals to appropriate test points on a unit under test (UUT) has a very crucial role to play in most electronics test systems. The sharing of test resources, connection of calibration references, load management, and many other functions are all managed by the switching system; the switching system acts as the interface between the unit under test and the test equipment. 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 solution 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.

For additional information on LXI Switching check out our Knowledgebase.

The Pickering and LXI Switching Relationship

Pickering was one of the early adopters of the LXI standard as a means of providing a standardized interface for Ethernet (LAN) controlled instruments and continue to be active in the evolution of the specification. We are a Strategic Member of thelxi_logo.png LXI Consortium, for more information on the LXI Standard please visit their website at www.lxistandard.org. Today, the LXI Consortium has proudly certified over 3,500 LXI products from 41 vendors in 303 different product families all complying to the worldwide standard. 

We manufacture a wide range of LXI switching (Ethernet Controlled) solutions and we strive to ensure that we meet your test and measurement needs and have specific solutions available for you. 

Take a look at some of our Success Stories including how LXI supported the CERN collider for signal management and how LXI was used in HASS testing, among many other stories.

LXI Modular Chassis

For applications requiring diverse switching functions but preferring a LXI interface, look no further than our LXI modular chassis. These chassis are capable of hosting our extensive range of 3U PXI switching and test & measurement (T&M) modules in an LXI environment, allowing remote control over a gigabit Ethernet connection.

Our LXI modular chassis are available in 7-slot or 18-slot and support over 1,000 of our PXI modules, additionally our 2-Slot USB/LXI Chassis allows most of our 1 or 2-slot PXI modules to be controlled via USB or Ethernet. The PXI modules range from: PXI general purpose relays, matrices, multiplexers and RF switches to special PXI switching functions such as fault/signal insertion. Also supported are a selection of T&M modules such as programmable resistors, digital I/O, power supplies, battery simulators and attenuators.

New Product _ 2 Slot LXI ChassisNEW! 2 Slot USB/LXI Modular Chassis

The 2 Slot USB/LXI Chassis offers a small lightweight form factor, making it ideal for portable, benchtop and space restrictive applications. It supports one or two 3U Pickering PXI modules. The USB compatible and LXI compliant interfaces enable the chassis to be controlled directly through standard interfaces found on most personal computers—allowing for a very cost effective route into the modular test and measurement market.

LXI Products and Reference Map

Pickering offers various other LXI related products to satisfy your test and measurement needs including the Modular ChassisLow Frequency Matrices, RF/Microwave Matrices & Multiplexers and more. We also offer mating cables and connectors for these modules to ensure speedy and successful system integration.

We don't want to blow our own horn, but we are aware of our large and continuously growing range of LXI products. For that reason, we wanted to provide you with an easy way to find the products you need in our Product Reference Map. This is a single reference sheet to over 1,000 modular solutions and 150 switching systems, all of which comply to the worldwide LXI standard.

Product Reference Map

 LXI Switching Systems Product Map

 We also have similar reference maps available for our PXI, PCI, Programmable Resistors, Cable & Connectors and Reed Relay products - take a look >>
 

 

Want More Information on LXI Switching? Download Our LXImate!

To learn more about LXI, take a look at our LXIMate book - a guide for those new to LXI systems and a useful source of reference material for the more experienced. This is a living document that we will continue to develop in support of the LXI standard and its future evolution. We welcome any feedback on subjects you would like to be included in future issues. 

LXIMate Book

Get Your Free Copy Here

3 Year Warranty

Pickering stands behind all of our products with a standard three-year warranty. All products manufactured by Pickering Interfaces are warranted against defective materials and workmanship for a period of three years from the date of delivery. 

Pickering Product 3 Year WarrantyWhat does that mean to you? 

  • Lower cost of ownership
  • Increased confidence in product uptime
  • Reliable, long-lasting products
 

Questions/Comments?

We know this was a lot of information on LXI Switching and you are probably saying to yourself "Yes, But I want more!" If you want to learn more about Pickering and it's products please feel free to browse the Pickering Website.

If you have any Questions or Comments about what you read today, please contact us at: e-mail support@pickeringtest.com 

 

Topics: LXI Switching, test and measurement systems, LXI, LXI switching solutions, LXI modular chassis

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 we have an on-line Cable Design Tool where you can design your own custom cable assemblies. 

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

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 simulation engineers for more information or...

   Webinar: Using Programmable Resistors for Sensor Simulation  Video: Intro to Programmable Resistors 

                                                                        Product Reference Map

Topics: test and measurement systems, Programmable Resistor, pxi simulation, pci simulation, sensor simulation in test