What started out as a demonstration of a solution to a signal multiplexing problem soon evolved into the provision of a variety of PXIe-based test and simulation modules and custom cabling to support the construction of five highly capable ATE stations.

In terms of business jets, until recently, the company in question had commercial jets that could seat up to about 50 passengers. However, the company has now developed an aircraft that will accommodate more than 100 passengers.

To support the development and production of the new aircraft, the company uses automated test systems (ATS) to verify the connectivity of the avionics systems. Four systems will be used during production, and a fifth will be kept in reserve as a spare or for developing new tests.

In early February 2023, the aerospace company shortlisted six systems integrators and asked them to quote for the provision of ATS hardware and software. One of the integrators quickly contacted Pickering to discuss hardware.

A particular challenge was going to be the multiplexing of a proprietary high-speed differential signal that has a strict line impedance of 78Ω; and the OEM had struggled in the past, not finding any suitable off-the-shelf solutions.

Fortunately, Pickering had encountered a similar problem before and was able to demonstrate a solution through the system integrator that had made contact. The solution combined an LXI chassis with custom-built cables. The demo worked perfectly, and Pickering won great respect with the aerospace company.

Pickering also gave an overview of its products, detailing the capabilities of modules used extensively in aerospace test and simulation applications. The company also stressed the importance of choosing the right chassis on which to base the ATS. Specifically, while the demonstration had employed an LXI chassis, it was felt PXIe would be better in the long run; in terms of future integration and modifications, and therefore a better total cost of ownership for the customer.

Michael Crespin, Sales Director for Pickering in France, comments: “It was a very good meeting as, up until this point, the end customer and Pickering had had no direct relationship. They had ordered some parts from us a few years before but for major projects everything had gone through systems integrators.”

The Solutions

To meet the customer’s test requirements, the following Pickering products were identified and agreed upon.

A PXIe, 18-slot full hybrid chassis (40-926-001). The chassis utilizes a single PCI segment with a dedicated PCIe-to-PCI bridge module for the hybrid slots. The PXI-specific high accuracy clocks and trigger signals are generated and controlled by an independent clock module attached to the rear of the backplane.

 

• PXIe 18-slot full hybrid chassis (42-926-001). Based on high-speed PCIe Gen2 technology, this chassis is a cost-effective option if you want a flexible, fully hybrid solution but don’t need the ultimate data transfer rate of our Gen3 chassis.
• Remote control interface kit (43-921-001-KIT). The kit comprises a PXIe module (43-921-001, on the left) with a daisy-chain facility, a PCIe remote control interface card (53-921-001), and a 2-meter interface cable (not shown)
•  PXIe multiplexers (40-739-001) are designed specifically for physical layer multiplexing or demultiplexing of differential signals that conform to the MIL-STD-1553 avionics serial data bus specification. These modules can be supplied as single or dual 2-pole multiplexers with 4, 8 or 16 channels, with each signal pair having a controlled 78 Ohm differential impedance.
• PXIe 16-channel analog output module (43-765-001) designed to meet the requirements of industrial control applications utilizing 4-20mA current loops. It consists of up to four 16-bit, digital-to-analog converters (DACs), capable of creating four current outputs each. Output current in the ranges 0 to 4mA and 20 to 24mA provide for simulating error or extra signaling conditions. The ±24mA mode gives the ability to simulate either sourcing or sinking sensor.
• PXIe 80xSPST relay module (42-139A-101, shown above) and a PXIe 52xSPDT relay module (42-139A-201). Both are suitable for high-density switching applications with medium power, and the relays have a 2A current capacity with voltage rating to 300 VDC/250 VAC.
• PXIe high-density power relay module (42-153-001-HI) with 50 SPST switches. Electro-mechanical power relays are used, which are suitable for switching loads up to 5A at 250VAC.
•  PXI 10 A power relay module (40-160-001) is suitable for switching heavy AC or DC loads or slaving to large external relays, contactors and solenoids.
•  PXIe 128-channel digital input module (42-414-101) with input voltages up to 50 V provides a convenient way of determining the status of input lines by comparing the input voltage with two programmable threshold voltages – quickly establishing if the input is low, high or in an intermediate logic state.
• LXI high-density 192×8 single-pole matrix module (60-550-023) capable of switching up to 300VDC/250VAC or 2A (60W max). High-quality electro-mechanical relays offer high switching confidence and make them suitable for signal routing in large ATE systems.

Though the above described in the singular, multiple of each have been supplied. Specifically, each ATE system is based on two 18-slot PXI hybrid chassis daisy-chained together; thus each system can accommodate multiple relay modules etc. Pickering also supplied more than 70 custom cables.

“Although we’re not well known for providing cables, custom cabling is, nonetheless, one of our core capabilities,” continues Crespin. “We have a Pickering Connect division that has created and delivered fit-for-purpose cables of various impedances for many customers in the past.”

The cables were designed and built in Pickering’s factory in the Czech Republic, where its Connect division is based, and a graphical design tool was supplied to speed the design-to-production process.

“Once we knew exactly what was required, it took us just a few working days to get a quote out for 14 different cables,” recalls Crespin. “Also, we had much shorter lead times compared to the customer’s incumbent supplier.”

Updated Strategy

After the hardware was agreed upon, quoted, and prices accepted, a change of plan was made. For expediency, the aerospace company decided to use in-house engineering resources to build the test systems. In other words, Pickering would supply the hardware and cables directly to the end customer.

Also, while the order was for five systems, it was decided to supply just one in the first instance and get it fully integrated. This gave the aerospace company’s engineers time to write some tests and devise a test sequence. Note: during this time, Pickering’s cabling specialists in the Czech Republic were on standby, ready to assist and, if necessary, visit the customer in case modifications needed to be made.

With this PXI hybrid setup, the chassis had to be powered before the PC boots so that the PC can detect hardware through the PCIe bus. When the chassis is contained within a cabinet, opening it to access power switches is not ideal, nor is keeping the chassis powered 24/7.

Note: most OEMs of PXIe chassis equipment (including NI, which owns most of the market) accept that as being the nature of PXI—something users must live with.

Pickering’s solution to the problem is to keep the chassis in sleep mode, a feature customers value.

Also worthy of note, and another reason for selecting Pickering, is that the ATE system’s operating system is Linux; whereas most test systems are Windows-based. There are perhaps 60 PXI vendors in the industry but only a very few – of which Pickering is one – offer Linux drivers.

“This was an amazing project,” concludes Crespin, “in terms of how it all came together, how technical problems were solved, such as multiplexing impedance-critical signals and the use of the sleep mode for the PXIe chassis, the rapid creation of custom cables and the staggered delivery of products to give the customer earliest possible access to hardware.”

Reproduced with the kind permission of Pickering Interfaces