Test & Measurement

Freedom is good

2nd December 2013
Nat Bowers

With continued development, this article takes a look at various test platforms and where they now appear to be headed, and why. By David Owen, Business Development Manager, with Pickering Interfaces USA, & Bob Stasonis, Marketing Manager, with Pickering Interfaces USA.

This year has seen the continued development of, specifically, three test platforms; a new market message has helped attract new users from older platforms such as GPIB and VXI, and the choices seem to continue to expand for users. From a professional and a business standpoint, choice is good for both vendors and customers as it allows for a broader range of applications to be supported by a greater number of products and platforms, enabling them to address every budget and requirement.

As the only Ethernet based T&M control platform, LXI is managed by the LXI Consortium, which as of May 2013 had certified more than 2,100 products from 40 different vendors (since products were first launched in December 2005).

That is particularly impressive since the consortium requires third party certification of LXI devices to ensure vendors maintain the interoperability standards set by the specification for Ethernet (LAN) controlled instruments. LXI is also the largest of the new T&M standards measured by annual value of products sold.

What does that mean for the vendors and users of LXI products? First of all, it certainly ensures that complete test systems can easily be assembled with a number of LXI products. Second, certification reinforces the robustness of the Ethernet interface and its widespread availability on computing platforms and ensures that it has the same feel and stability associated with GPIB systems. For vendors, it validates their product line is compatible with all LXI products.

Although Pickering Interfaces’ core business is PXI based switching systems, the company has invested heavily in the LXI platform, for good business reason.

Doing the impossible in LXI

Many of our dedicated LXI solutions were simply impractical to implement in a PXI form factor. PXI imposes modular mechanical constraints on product design and when there is a requirement for a large and/or very complex switching system, it simply will not fit elegantly. Creating a cross-point matrix for example with 4,000 off 2A rated relays requires a great number of modules to be interconnected, often completely filling or exceeding the capacity of a single PXI chassis.

Some products require the use of large components such as microwave relays which simply take too much of the space in a PXI chassis; doing so inflates the real cost of the switch and takes up valuable rack space. Each PXI module has its own overhead from the PCI interface it carries and the slots it occupies in the chassis.

In comparison the LXI platform requires its own LAN controller interface, and that has a higher cost than the PCI interface on a single PXI module alone. But LXI has its own case system to support its switch payload, which is typically much lower cost than the PXI chassis. An added advantage is that external cabling is usually greatly simplified as any inter-module is eliminated as it is handled internally, often by PCB tracks. In the case of a large complex switching application, the overall cost advantage can be a 40% saving or even more.

The introduction of the 65-110 wideband modular chassis has also demonstrated the flexibility of LXI; it can be used to create switching systems that out-perform their PXI counterparts by being more innovative about their architecture.

So for Pickering Interfaces the advantages of LXI are clear, they enable it to provide switching systems with LXI which are hard, impossible or uneconomical to do in PXI. It is not just switching systems these arguments apply to, in almost all product categories of test and measurement there are clear differences in what can be achieved in one platform compared to another. The differences may lie in measurement traceability, accuracy or particular areas of performance and they vary from one category to another.

Market growth

For Pickering Interfaces switching solutions PXI remains its largest switching platform, focussing on smaller and more diverse switching applications or where switching is mixed with PXI instrumentation. Pickering has been able to develop a huge range of switching solutions based on PXI, more than all other vendors combined. It allows the rapid development of modules for relatively low volumes of sales with manageable developments costs.

Its PXI switching modules can also be supported in its LXI controlled Modular Chassis, so PXI switching modules can be used in an LXI or a PXI controlled environment.

PXI is not the only modular standard that is growing. AXIe also has its adopters for much higher performance systems and has embedded interfaces based on both Ethernet and PXI.

It is unusual to have three relatively new (in terms of test and measurement) standards making market progress at the same time, but it seems the future for test and measurement is principally with these growing instrumentation standards. Users have more choice, that is good news for the industry and vendors have the opportunity to promote the platform that best suits their products, knowing that all three standards will have their place in test systems. Mixing control interfaces in a test system has never been easier, or more attractive.

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