Pickering Interfaces' Blog - Insights into Switching Technology

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
• Voltage
• 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:

• DC power supplies
• Digital I/O
• Breadboards
• Signal conditioning (amplifiers and attenuators)
• Signal generation

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

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.

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”?

This 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. 

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...

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

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 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. 
    

• 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
  • If the desired accuracy, precision, range, number of channel, power handling, etc is not available, we are often able to configure custom builds or even design a new version of a PXI/PCI model.

Our 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...