We have seen three test platforms continue developing their market message and attracting new users from older platforms, such as GPIB and VXI; the choices seem to expand for users. From a professional and a business standpoint, we see the choices as good for both vendors and customers as it allows for a broader range of applications to be supported by many products and platforms that address every budget and requirement. In this short article, we point out where the various platforms appear to be headed and why, from a Pickering standpoint, the freedom of choice is a good thing.
The LXI Consortium has announced it has certified more than 1,500 products from 35 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. What does that mean for the vendors and users of LXI products? First, it ensures that complete test systems can easily be assembled with many 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 that their product line is compatible with all LXI products. For Pickering Interfaces, the core of our business is PXI-based switching systems, but we have invested heavily in the LXI platform for sound business reasons.
Doing the impossible in LXI
Many of our dedicated LXI solutions were 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. Creating a crosspoint matrix, for example, with 4,000 off 2A-rated relays, requires a significant number of modules to be interconnected, often filling or exceeding the capacity of a single PXI chassis. Some products require large components, such as microwave relays, which take up too much space in a PXI chassis, inflating the switch's actual cost and taking 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 - Granted, a higher cost than the PCI interface on PXI - and its 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; in the case of a large complex switching application, the overall cost advantage can be a 40% saving or even more. So for Pickering Interfaces, the benefits of LXI are clear; they enable us to provide switching systems with LXI, which are complicated, 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 apparent 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 vary from category to category. Control distances and robustness of the connection can also be significant - and LAN connections excel in this area because of their IT heritage.
The PXI standard continues to evolve as work has started, and the backplane trigger function API has been standardized. PXI remains the dominant implementation of the standard (relative to PXIe) in both modules and chassis, but there are applications where PXIe makes more sense because of the need to transfer large files into or out of the modules. For applications where PXIe modules are required, the use of hybrid chassis that support both versions of the standard (PXI and PXIe) makes clear sense since module choice is much broader in PXI than PXIe. The platform of choice for applications where the backplane speed of PXIe is likely to be Hybrid chassis where the slots (except the controller and timing slots) can accept either PXI or PXIe modules. Such a chassis is always likely to be a premium product since it has to support both power sources and control interfaces (PCI and PCIe).
PXI is not the only modular standard that is growing. AXIe has its adopters for higher-performance systems and embedded interfaces based on aspects of both LXI and PXI.
PXI in LXI
More options on the platform of choice arise with Pickering Interfaces supporting its PXI switching modules in an LXI-controlled modular chassis so that Pickering PXI switching modules can be placed in an LXI or a PXI-controlled environment.