PXI – PCI eXtensions for Instrumentation – is a modular instrumentation standard that is now supported by 70 vendors offering more than 1500 products. While it has made its mark in manufacturing test, its adoption in the design engineering environment has been slower. However, things are changing.
Loofie Gutterman, who is also president of PXI specialist Marvin Test Solutions (formerly Geotest), said: "Last year, we had a major programme with the US Airforce for an ultra-rugged flight line tester based on PXI," said Gutterman. The order was for 85 chassis and, at around $6million, was the largest in the company's history. "For Marvin, and for the PXI Systems Alliance, that is affirmation that the DoD is truly standardising on PXI – not just accepting it, but also standardising on it."
There has also been significant interest in PXI from the telecoms and wireless sectors. Gutterman pointed to the acquisition of ZTec by LitePoint, part of Teradyne, in October 2013. "In the same way as there is acceptance in mil/aero, the same thing is going on in wireless. LitePoint picked up ZTec because it wanted that PXI technology, specifically in the wireless LAN space."
The majority, although certainly not all, of such activity exists in manufacturing test, sometimes bringing a 'pull-through' effect in terms of encouraging the use of PXI at the engineering stage.
One area where this appears to be working the other way round is in the semiconductor industry, where most PXI-based test systems are being deployed in R&D and characterisation, then starting to migrate into production. Gutterman commented: "The attractive thing about PXI is that it is just geared for automation. People who are doing characterisation might be running 50 parts – the first units they want to characterise – and automating that measurement process is the way to go. PXI is the perfect candidate – and it is a very reasonable price compared to 'big iron' testers."
The cost of PXI is a curious topic. According to the New Electronics survey (see the roundtable discussion starting on p33), one of the barriers to adoption of PXI in the UK is the perception of it being a high cost platform. Gutterman said: "I don't think we ever had the problem of PXI being considered expensive. And, let's face it, if you have existing equipment that works, then you are not going to replace it, whether it is PXI or not." While product lifecycles are constantly getting shorter, the equipment used to test these products – at any stage of the design cycle – tends to remain the same. The complete change from a 'box architecture' to a 'modular card architecture' is therefore not one to be taken lightly.
It could be that PXI, particularly when used in the aerospace/defence type applications, is adopted in the UK on a 'by project' basis, with a view to migrating the test solution from design through to manufacturer and maintenance. In this way, it can seem relatively expensive compared to reuseable benchtop test instruments that are intended to remain with R&D.
The latest addition to the standard – which has evolved into a stable platform – was a the ratification of the trigger bus specification, something that should simplify engineers' lives when it comes to allocating trigger lines for different instrumentation across the backplane. Such changes in recent years have not had an impact on equipment interoperability.
In the early days of PXI, an annual Plug Fest would be held at AutoTestCon in the US, something which ironed out incompatibility issues between the suppliers. But confidence levels have improved to the point where it is no longer required. Yet the idea of revisiting Plug Fests is gaining momentum, with the possibility of running one at this year's AutoTestCon in St Louis, although this has yet to be finalised.
PXI has not suddenly become unstable; instead, it is the plethora of PXI related software that is driving the Plug Fest idea – and software was not included in the original Plug Fest format.
"PXI is an open architecture and open architectures are great, as they give people flexibility and options," said Gutterman. "But it also places a bit of a burden on vendors to make sure they are architecting their software environments correctly to make sure the different environments don't conflict and cause problems. That is the spirit of what we are trying to do with this potential Plug Fest."
While there is a software standard within PXI, Gutterman does not believe there is a concern about suppliers meeting this. "It is more about verifying that, when you install half a dozen different software packages from half a dozen different vendors, you are not going to cause problems. We want to ensure the customer has a positive experience using PXI; we want to prove that you don't have to be a rocket scientist to install PXI. We believe it is very simple."
PXI on the up
PXI demonstrated phenomenal growth in its formative years and Gutterman believes this is continuing. "My resources show growth rates are still at about 15%, which is pretty remarkable considering the age of the standard and the typical test and measurement market grows at between 4 and 6%. That shows people are converting from other platforms to PXI and we see that on a daily basis. It's amazing."
VXI emerged in 1988 and it is still used widely, but Gutterman believes users are at the point where they see their choices with VXI as limited. Support for VXI is becoming more difficult, so users are starting to look at the modular card architecture. "For many of them, it is a good time to move to PXI – it is an area where there is still a lot of potential."