Preaching the potential of PXI

Richard Wilson discovered why interest in PXI-based modular test systems is growing, during a visit to the National Electronics Week exhibition

PXI modular test system suppliers were attempting, and probably succeeding in, a takeover of the National Electronics Week exhibition in Birmingham last week.

The exhibition had an area dedicated to suppliers of PXI system hardware. PXI is also being used for development, with embedded design platforms such as CompactRio from National Instruments, but the demonstrations in Birmingham were all about using PXI as a programmable test platform.

The list of PXI suppliers was wide-ranging, including as it did, Amfax (NI systems specialist); ATE Solutions; Applicos; Goepel Electronic; Thurlby Thandar Instruments (TTI); Peak (PXI-based ATE firm); Pickering; Stantronic; Aspen Electronics and Jtag Technologies, as well as Keysight Technologies and, of course, National Instruments.

National Instruments’ UK marketing engineer Aaron Edgcumbe was encouraged by the positive response of engineers visiting the event. “The quality of the engineering enquiries has been very high,” Edgcumbe told Electronics Weekly.

For some engineers visiting the exhibition, the event represented an introduction to PXI and PXI Express‑based system hardware, making it “a way to learn about the capabilities of PXI for perhaps the first time”, said Edgcumbe.

Engineering interest was representative of the UK electronics market and included traditional industrial, defence and communications sectors. Modular test systems have advantages in fast-moving 5G mobile communications development, where data acquisition rates are near the limits and standards are yet to be finalised.

But PXI is also playing its part in testing devices for the internet of things, medical and renewable energy systems.

Howard Venning, managing director of Aspen Electronics, which sells PXI systems from Keysight Technologies and Tabor Electronics, said the company is an interesting new market for its test systems.

“There is big interest in making power measurements,” said Venning. “The traditional markets for our RF and microwave tester systems are defence and communications, of course, but we are also seeing growing interest in what I like to call niche products used for power measurement.”

According to Johannes van der Vegt, PXI sales engineer with Netherlands‑based measurement system supplier Applicos, the strongest applications for PXI-based systems are still in production test and system monitoring.

“We find that in the design departments engineers still prefer standalone test instruments – scopes and analysers – mainly because measurements can be made by simple button-pushes and not by programming software,” van der Vegt told Electronics Weekly.

PXI modular instruments are no longer only used in isolation. They can be part of a measurement set-up which incorporates different instrument formats such as LXI.

PXI systems are also used in tandem with USB connected devices, which can be standalone bench-top instruments.

USB
So, for example, Pickering Interfaces was demonstrating an eight-port USB hub at the PXI Show in Birmingham.

The 40-738 USB hub allows data to be streamed to and from the USB devices by the system controller.

The output ports can be connected or disconnected programmatically to simulate the mechanical connection of a USB device to the module. Additionally, each port has the ability to connect and disconnect the power and data paths separately, enabling the simulation of various connection faults.

Measurement step-up
Another test system re-seller, TTI, was demonstrating how a measurement step-up can use both PXI and LXI. The PXI modules were used for data acquisition and the switching between units carried out with the larger format LXI modules.

It used the CMX34 sub-system from VTI Instruments, which combines the high throughput of an 18-slot PXI Express mainframe for data intensive applications with a 16-slot LXI mainframe used for signal switching and I/O.

Also on the TTI stand was a portable PXI chassis from VTI Instruments, which incorporates a 14-inch touchscreen display and embedded computer with throughput rates of 1Gbyte/s.

The PMX04-DAQ is a preconfigured PMX04 four-slot PXI Hybrid mainframe packaged with EXLab data acquisition software and instrumentation options that include high-speed multi-channel digitisers and arbitrary waveform generators.

NI was demonstrating its PXI‑based multiple instrument concept, VirtualBench. It integrates a mixed‑signal oscilloscope, function generator, digital multimeter, programmable DC power supply and digital I/O. The user interface can be run on a PC or iPad.

Daughter boards
Applicos has an interesting spin on the design of PXI digitiser modules. It designs digitisers and generators as daughter boards which sit on a single slot PXI base module.

The base module provides PXI bus interfacing, power supplies, clock generation and calibration circuitry, and two daughter boards may be connected.
The daughter board interface is essentially PXI, with only “slight modifications”, said van der Vegt.

The PA72D16180A daughter board is a digitiser capable of capturing signals up to 180Msample/s with 16-bit resolution.

This latest version of the digitiser has a 1MΩ input impedance selection, which also allows for higher input range voltages, up to 30V peak-to-peak. Also the input bandwidth is increased up to 170MHz.

Other PXI daughter boards include 14- or 16-bit generators, digital I/O cards and analogue filtering cards.
To minimise cross-talk the boards have separate power supplies. Differential inputs and outputs are also used to reduce cross-talk between digitiser and signal generator.

PXI-based modular instruments are as popular as they have ever been. Take‑up is growing all the time and, according to market watcher Frost & Sullivan, by 2020 the market could be worth over $1.75bn to suppliers.

Last week’s event in Birmingham was evidence that the UK PXI test market is likely to contribute to this growth.

sue proud

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