Pickering Interfaces' Blog - Insights into Switching Technology

Considerations for Effective PXI Test System Matrix Maintenance

Posted by Bob Stasonis on Jan 19, 2021 10:39:23 AM

A goal of any manufacturing organization is to maximize the time that their test systems are operational. A test system that is down due to maintenance issues costs a company significant dollars in unrealized revenue. Switching systems, and in particular, matrices, are central to most automated test systems and rely on relays as the switching element. Relays are mechanical in nature, and as such, may fail over time for various reasons. This white paper explores these issues and discusses methodologies that can help shorten repair cycle time, in turn, sustaining and maximizing system uptime.

Considerations for effective PXI test system maintenance

Matrices allow for very flexible connection strategies between a single core set of test equipment and one or more DUTs (Devices Under Test). This approach saves the cost of duplicating test equipment; however, it also means that the switching matrix is placed in a central, potentially vulnerable position, where it may be subjected to abuse or accidents during use due to programming errors in development, wiring errors or unexpected DUT faults. Typical repair cycles can take up to 2- 4 weeks and can be extended when faults cannot be reproduced at the OEM.

The main factors that affect test system matrix reliability are the choice of relay used for the signal switching, and the conditions under which the relays must operate. The relays used in most matrices are mechanical devices whose lifetime is determined by the quality of their construction and moving parts, and the contact materials. A faulty relay can bring a production line to a halt; therefore, quick identification of the fault and subsequent repair is crucial in getting the system quickly back online, enabling product shipping to resume. High-quality EMRs (electro-mechanical relays) can have lifetimes in the order of 100 million operations under light load conditions. Still, instrument-grade reed relays have lifetimes in excess of one billion operations, and it is for this reason, as well as their smaller size, that reed relays are generally preferred.

Factors That Influence Relay Lifetimes

The conditions under which relays are operated impact the integrity of the contact materials. While in most cases it is best to cold switch a signal – i.e., perform the switching operation without any applied current or voltage stimulus – that’s not always possible. But it must be noted thathot switching’ – opening or closing a relay while it is carrying a signal – reduces relay life. Relays that hot switch signals run hotter than relays that cold switch and their contacts will erode much faster. Both of these factors – temperature and contact damage - will cause the relay to fail sooner. In general, vendors life-test relays with resistive sources and loads. In the real world, however, loads can be both inductive and capacitive, and these loads can shorten relay life to a greater extent than simple resistive loads.

It is not always obvious how much voltage or current is being hot switched by a relay. For example, if a relay is connecting a low impedance source to a high impedance load, it could be expected that the switched current will be relatively low. However, if the cabling or load has significant parasitic capacitance, there may be a high surge current through the relay when it closes as the source charges the effective capacitor.

A relay may also experience a high surge current when it connects a source to a capacitive load that is carrying a charge from a previous state. This might occur, for example, when a switching system reverses the polarity on a DUT, or if an earlier operation has left a charge on a high impedance load.

Switching systems are also typically capacitive at their terminals. If a switching matrix has a large number of closures on a single Y-axis to X connections, the resulting capacitance can create an extra load that can shorten relay life when hot switching.

Resistance in the cable wiring and the PCB tracks can help reduce the surge currents and therefore increase relay life, but this effect declines rapidly as the signal voltage increases.

High current or high-power inrushes are the most damaging and most frequent cause of contact damage. As well as inrushes due to charging capacitive loads, discharging capacitors can be an even more significant issue as the current is often only limited by the resistance of the reed switch and PCB tracks. Even capacitors charged to quite low voltages can cause current inrushes of tens of amps, and although they may be for microseconds only, they can cause damage to small reed switches.

Common Failure Mechanism in Relay Switching

The most common failure mechanisms for switching system relays used to hot switch signals are:

  • Welded contacts - usually caused by high inrush currents as the contacts are closed, creating molten or soft metal in the contact area - Figure 1.
  • Contacts having variable or intermittent contact resistance. This occurs particularly at low current levels because of the erosion of the contact materials. It may also be that the relay is reaching end of life.
  • Failure to close – caused by severe erosion of the contacts or the build-up of debris on the contacts (more an issue with EMRs as their contacts are exposed to air; reed relays have hermetically sealed contacts).

A fuller discussion of factors that influence the lifetime of relays can be found in our white paper entitled  ‘Avoiding failure modes in switch systems for test.’

Often, failures in test systems are caused by accident. For example, cabling and software errors can cause parts of the system to be connected that were never intended to be, resulting in shorts on power supplies or turning hot switch events into capacitive loads. The relay may withstand these accidents, but it could suffer partial damage to its contacts, which will shorten its operational life as the system is used and ages. Even when the system is operating correctly, an attempt to test a faulty DUT can force operation beyond the relay specification, stressing the switching system.

Fault Diagnostics

Historically, due to demands from customers (usually military or aerospace), platforms such as VXI have offered a self-test facility for the relays. However, the extent of test coverage provided could be patchy. Sometimes only the control system was tested and not the relay contacts (the most likely part to fail); other practices tested the relay contacts through hardware internal to the switch module, but it could not test the integrity of the connector. Products based on smaller footprint platforms, such as PXI, did not initially provide self-test. This gave rise to perhaps one of the most misguided approaches to managing the issue – ‘relay counting’. Here, the software counts how many times a relay has been operated so that the relay can be replaced when the number of operations reaches a given threshold. This method is deeply flawed for several reasons:

  • Relay life changes by three orders of magnitude according to the load present. The software has little or more commonly no knowledge of the load. It is merely a counting system.
  • It takes no account of the accidents that happen in systems, such as UUT failures, that shorten relay life.
  • Relays are subject to significant variations in lifetime by batch.

The consequence of this is that real switching systems can have a much shorter or much longer life than a relay counting system will indicate.

Diagnostic Test Self Test Tools

The good news is that the status of self-test is changing. Pickering now provides PXI matrix solutions, which include a built-in self-test facility called BIRST™ (Built-In Relay Self-Test), which addresses the shortcomings of the older self-test systems and the relay counting methods. BIRST is implemented as a very compact hardware addition to the PXI modules; the source/measure hardware is on-board and measurements are made through the matrix. It works in conjunction with a dedicated software application to electrically explore the matrix, measuring the resistance of each signal path with repeatability measured in a few milliohms. The user simply needs to disconnect the PXI module from the test system and then run the BIRST program. The test process is fast, each relay requiring just a few 10s of milliseconds to test fully. The software then displays the test results as a graphical representation of the matrix, highlighting any relays that are faulty and allowing the user to identify the physical position of each faulty device quickly. Every relay is checked; welded closed and stuck open relays are quickly identified.

BIRST Built In Relay Self Test Display

BIRST only identifies those relays which need attention for maintenance and avoids unnecessary disturbance and system downtime. The tool can identify relays with higher than expected path resistance, allowing users to change those relays before they fail. Through-hole relays are extensively used on Pickering’s switch matrix modules, allowing the user to self service the module with commonly available tools and get it back into service quickly. We encourage this practice: warranties are unaffected, and we even supplies spare relays on each switch module for the purpose

Our eBIRST external diagnostic test tools work similarly to BIRST but require an external test tool to be connected to the switch module under test. The relay testing source/measure hardware is contained within the tool, and an eBIRST software application exercises both the module and the connected tool and returns the relay test results and analysis.

While BIRST identifies faults within the matrix, it cannot verify the switch module’s front panel connector. So if a connector is damaged in any way, BIRST will not help. This is a key advantage that eBIRST brings: it allows the user to analyze the switching system right out to the external interface. The eBIRST test hardware can be connected directly to every individual relay on the switch module via the external connector, and this results in superior fault resolution compared to the BIRST tool, which tests relays using discrete matrix paths consisting of multiple switches. Another significant advantage is that eBIRST is available for any configuration of the switch module, not just matrices.

Like BIRST, eBIRST enables faulty relays to be identified so they can be replaced by the user on-site with minimal downtime. As with BIRST, we encourage this practice, and again, the warranty is unaffected.

The eBIRST tools are self-contained; only a USB2 port on a PC running Windows and the supplied application program are additionally required. The program uses a Test Definition File created for each switching module that defines how to test it. This enables users to test any of our switching systems that use mechanical relays with precious metal contacts (typically contacts with a rating of 2A or less) and also those incorporating solid-state relays. DC coupled RF systems using SMB connectors are also supported using test adapters. Each tool is generic—it will support DC-coupled switching systems that use multi-pin connectors on our PXI, PCI and LXI controlled switching systems. eBIRST also supports all-new generations of our BRIC matrix solutions, which now feature cross-point counts of over 9000 in a compact PXI module.

Signal Routing Software

Once the user has run BIRST or eBIRST diagnostic test tools and has discovered a faulty relay in a matrix, they may find that testing is still halted as they do not have a spare matrix (or relay) in stock. However, by using our Switch Path Manager (SPM) software, there may be a way to keep the tester functioning until a replacement is available.

Switch Path Manager simplifies signal routing through switching systems and speeds up the development of switching system software. Switch Path Manager supports our switching modules and the interconnection between them. Once a switching system model has been created, signal routing can be performed simply by defining the endpoints that are required to be connected—the ability to automate signal routing results in effective and easy switching system management.

In the event described above where a faulty matrix relay is discovered, but no replacement is immediately available, and repair by the user is also not an option, the operator can use the Exclude Endpoint feature within SPM to instruct the router not to use that path in its calculations. Figure 3 shows a matrix connecting a power supply to a DUT. The left-hand side shows the relay closures necessary to make the connections. However, if a relay fails along the Y2 axis, in SPM, a single command can be used to set up the router to avoid using Y2. This is shown on the right-hand side of the figure where we see that the switch path that originally used Y2 now uses Y3. Once the matrix has been repaired or replaced, the test engineer can remove the exclusion, and the program will run as before.

Pickering's Switch Path Manager Software Features

A thorough understanding of the factors that adversely affect the life of mechanical relays – the critical component in a switching matrix – will enable preventative maintenance based on proper operating procedures. This will reduce test system downtime and improve productivity. If a component does fail, new test procedures will allow the rapid detection of the fault, and expedite its repair, or provide an effective means to work around the problem.

If you have questions on your PXI test system maintenance - please feel free to contact us or visit our Support Knowledgebase for answers.

Topics: PXI, automated test system, test and measurement systems, Relay Reliability, Relays, test system maintenance

Simplifying Test Interconnect with Pickering’s Cable Design Tool

Posted by Bob Stasonis on Apr 6, 2020 5:34:31 PM
Simplify test interconnect

Correct interconnect products need to be selected once instruments and switching products have been chosen for a test set-up. This can be a complex process while checks are made, resulting in a significant investment in time, money, and in some cases, even exceeding the initial purchase cost of the devices.

The cable design for a test system is probably the last section of a test system development. And because proper cabling is critical for repeatability and accuracy, it needs care and expertise. Depending on the application, the test engineer needs to consider test specifications, including voltage, current, temperature, insertion losses, and more. From there, the engineer needs to determine the connections between the instrument and the Device Under Test (DUT), and then select connector types, backshells, wire length, and wire types. Unless the test engineer is an expert on cabling, researching wires and connectors can be a daunting task.

As a leader in test and measurement switching and simulation for over 30 years, we fully understand the importance of high performance and reliable interconnection between the component parts of a test system and DUT. That is why we established our own in-house connectivity division that manufactures a comprehensive range of 1200+ high-quality cable and connector solutions. There are times, however, when a standard cable assembly is not suitable, and there is a need for custom connectors and wire types or specific harness wiring. Pickering's free online Cable Design Tool (CDT) is a simple and efficient way of creating these custom cabling solutions.

Pickering's Cable Design Tool and completed cableThe cable itself can be drawn in a few clicks, choosing connectors, backshells and wires from a library. Linking them together is achieved manually by clicking on pins, or an auto-link option will link user-selectable groups of pins in 1-1 order. A third option is to use the CSV import, where the pinout with signal names can be prepared in an Excel sheet.

Currently, there are around 500 connectors and 400 types of wires and cables in the library (which is growing daily). These can be selected by many attributes, including pin count, connector type, rated voltage, conductor count, insulation type, conductor size and more. Many sophisticated functions, such as screening, sleeving and labels, bundling, and much more, can also be added. 

When the design is completed, the tool creates the full datasheet with all part numbers, lengths, labeling and pinout map for each path which can be downloaded in PDF format. Also, if the customer decides to work with Pickering, it can be used as build instructions for their production department. Otherwise, the customer is free to take the design and solicit other cable vendors.

Cable Design Tool data sheet

The tool is collaborative, enabling several people to work on a design, and once finished, the design is then sent to us to review. Our cable technicians can assist by suggesting cost-saving design changes and optimize the design for ease of manufacture by using stocked parts. Lead time is typically four to five weeks after receiving the order.

The main advantage offered by our connectivity division is the ability to provide precisely what you need. Our flexibility starts with the first point of inquiry. Our technicians receive cable drawings in many formats—AutoCAD, Visio documents, Excel pinouts, text descriptions, etc. They can analyze, design and manufacture complex custom cable harnesses. Our designers are there to help, whether modifying existing designs or designing new ones, our in-house production is flexible to cope with such demands and can manufacture in single quantities or high volume.

Start Using The Tool 

Take a look at our on-demand webinar "Simplifying Test Interconnect with Cable Design Tool" here >>

To learn more about cabling for your automated test system, take a look at our SwitchMate book, there is a whole section to help you understand it.

Cabling for your automated test system - Switchmate

Have questions or need more information? Please contact us here.

Topics: automated test system, software, Cables and Connectors

Automating Test Within Manufacturing Processes - White Paper

Posted by Kelly Porter on Apr 2, 2020 2:29:37 PM

 

whitepaper-cover-automating-test-within-maufacturing-processesIt is best practice when automating test within a manufacturing process to consider interconnection as an extension of the test instrument. In production, the interface between a device under test (DUT) and the test instruments will likely include a network of cabling, a signal distribution or switching subsystem, a connector panel, and device-specific adapters. In essence, all of the cabling, interfacing and switching should now be considered as an extension of the test instrument and must be allowed for when assessing the instrument’s capabilities.

There are always potential issues in production to keep in mind between a device under test (DUT) and the test instruments, focusing on how path resistance, line capacitance and insertion loss affect test results and what can be done to minimize their impact. Signal routing for test would be considered to be perfect if the path between the test instrument and the device under test was electrically ‘invisible’. Of course, this is asking the impossible. This is why test engineers need to take care of the whole measurement channel by considering everything between the instrument and the DUT, including cables, switching subsystems, connectors and mass interconnect products.

Selecting a flexible switching platform that can cover a range of application requirements and provide for future expansion provides a solid foundation for a test system design. You also want to keep in mind that in some cases, cables are supplied with switch modules, so they will have been designed to work with that module. This is why Pickering's modular switching portfolio provides maximum flexibility for system designs. Pickering also has a dedicated facility that produces cables and accessories to ensure that the performance of the switching module is not compromised by poor interconnections. 

Read the entire white paper here to learn more about potential issues in production between a device under test (DUT) and the test instruments, focusing on how path resistance, line capacitance and insertion loss affect test results and what can be done to minimize their impact. 

If you have questions or need more information on automating test within your manufacturing process – please reach out to one of our engineers here.

Topics: PXI, automated test system, test and measurement systems, Device Under Test, DUT, Cables and Connectors

Using Switch Matrices in Complex Test and Verification Installations

Posted by Kelly Porter on Oct 17, 2019 3:27:28 PM


Switch matrices are a flexible solution that should be part of your test strategy to automate complex test and verification whitepaper-image-Switch-Matrices-in-Complex-Test-and-Verificationsystems, especially in demanding industries such as aerospace, defense, automotive and semiconductor manufacturing. These matrices help accelerate test times over a manual process for test and facilitate reliable, repeatable and accurate results by eliminating error-prone manual intervention. The use of switch matrices can also help consolidate test processes in one space, rather than be distributed around several locations. Depending on the matrix type, it can also simplify the efforts to add additional test programs to the test system because of its ‘any test point to any instrument’ capability. There are limitations on simultaneous multipoint access as well as bandwidth. But proper matrix selection can shrink your test system and make it more flexible for today and into the future.

There are specific things you can think about to help you to understand how the use of switch matrices can save time and cost, reduce test area floor-space and improve reliability. These include what type of matrix to use whether it be crosspoint, tree multiplexer, RF and Microwave etc. You also want to understand how to configure a large matrix where software packages like Pickering’s signal routing software, Switch Path Manager (SPM), can simplify this programming effort. The maintenance of a switching system to avoid vulnerable positions and much more must also be included in your test strategy.

To learn more on this subject, check out our newest white paper here:  Using switch matrices in complex test and verification installations

For more information take a look at our updated SwitchMate Book.  If you have questions please contact us.

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

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

In 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.

Moving from VXI switching to PXI switching

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.

Pickering LXI Module

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

How PXI Can Solve Your Toughest Test & Measurement Challenges

Posted by Kim Otte on Apr 30, 2015 1:37:00 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 up 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 >>

  • Find additional application studies using PXI here >>

In conclusion

From the 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 & Simulation are our main focus, we serve your electronic test requirements in other ways. Our PXI product line also includes:

We also offer our eBIRST Switching System Test Tools - tools to help lower the cost of switching system ownership. As well as our Switch Path Manager signal routing software which simplifies signal routing through switching systems and speeds up the development of switching system software. 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 Pickering Interfaces

 


Switch Path Manager - Managing Switching Systems Effectively…

Learn more about  Switch Path Manager  here

 

 

 

Topics: software