Sessions address modular instruments at Autotestcon

Schaumburg, IL. Two sessions Wednesday September 18 at Autotestcon focused on modular instruments. In one panel session, participants discussed AXIe, LXI, PXI, and VXI and offered comparisons to bench instruments. The second session included a paper that offered details on the AXIe architecture.

The panel session was titled “Status and Outlook of Modular Instrumentation in the T&M Industry” and was moderated by Bob Helsel of the VXIBus Consortium, PXI Systems Alliance, and AXIe Consortium. Panelists included Von Campbell (Agilent Technologies), Larry Desjardin (Modular Methods), Tom Sarfi (VTI Instruments), Luke Schreier (National Instruments), and Steve Schink (Agilent).

Desjardin started the discussion with a detailed review of modular vs. traditional box instruments. Modular has the advantages of size, speed, and flexibility. Bench or box instruments feature availability, ease of use, and (via LXI) distance. He said that both formats had similar prices but different costs of test.

Modular sales in 2012 grew by 15 to 20% more than traditional instrument sales grew. However, traditional instrumentation still accounts for about 85% of all T&M sales. Commercial applications are adopting modular because of its higher speed resulting from memory map addressing (registers). For RF applications, modular is overtaking bench instrumentation and causing changes to the whole test ecosystem.

According to Desjardin, LXI has become the primary box instrument interface with some USB as well. VXI enjoys about a $200M annual market, and will be around for a long time because of its use in legacy test systems. Of the various modular standards, PXI/PXIe is the big winner. Although AXIe has several technical advantages, it’s just too early to tell how it will work out. Desjardin called it a wildcard.

Each of the panelists then presented more details about a particular modular format. Tom Sarfi discussed VXI and the large installed base built up after the 1987 introduction. Today, 60 to 70% of the market is large-scale MIL-Aero test. VXI has remained attractive for several reasons. Fundamentally, it’s well suited to large test systems by its bigger board area and higher power and cooling capabilities. The latest spec calls for 300 W per slot. In addition, VXI has progressively adopted new technologies as they became available, while maintaining backwards compatibility.

Some of the applications supported by VXI include high-density switching and multi-function analog instrumentation via daughter boards. Control is flexible through plug-and-play source code. Sarfi commented that VXI’s large installed base somewhat helped ease the effects of sequestration. Nevertheless, most activity is in the form of sustaining engineering rather than new product development.

Luke Schreier presented the status of PXI/PXIe, stating that because many different markets were served, overall higher growth rate was occurring with less risk. The 30-W limitation on 3U modules was both a curse and a blessing. Compared to the much higher power ratings of VXI and AXIe, PXI applications were restricted. On the other hand, it drives modular efficiency. Schreier gave examples of the latest features such as the user programmable FPGA capabilities in the NI Vector Signal Transceiver and the flexibility of PXI triggering.

Von Campbell gave an overview of AXIe—the specification now up to AXIe1 rev 2. Aeroflex, Guzik, Giga-tronics, Elma, TEC, Informtest, ADLINK, Agilent, and Modular Methods comprise the AXIe Consortium. One of the major advantages of AXIe is that it runs PXI code—a test program written for PXI will run on AXIe with no changes. Elma has an interface card that makes programming easier. Hiller Measurements will provide the MAXIe development system from 2014.

Steve Schink went on to present LXI, but I did not attend that part of the session. Visit these EE-Evaluation Engineering articles for more on LXI:

AXIe Architecture

A session titled “ATE Techniques and Applications 2” was chaired by Jeff Murrill of Northrop Grumman. The first paper (and the only one I attended in this session) was titled “AXIe Local Bus Architecture Delivers Unprecedented Bus Speed and Flexibility,” by Larry Desjardin (Modular Methods) and Lauri Viitas (Guzik Test and Measurement).

Desjardin presented the paper, starting with a brief overview of AXIe. This standard is based on Advanced TCA and programs like PXIe but with much higher power and larger board size. Triggers include parallel, star, and local or segment. The 12 parallel lines operate up to about 100 MHz. Star has very low jitter. But the focus of the paper was the 62-pair local bus.

The local bus actually is a number of separate very short buses that run between the right side of one slot to the left side of the next slot. Guzik has made use of these buses to transfer data from the company’s high speed ADC 6131 Waveform Digitizer Acquisition and Processing Module to memory, for example, and has demonstrated a 40-GB/s speed. Another application supported by the local bus is cascaded DSPs. The high speed addresses areas such as radar with on-the-fly ADC, particle count detectors, and streaming transient search. Guzik’s AXIe DP6000 Digital Processor Module can be used as a DSP co-processor and features an open FPGA so customers can code their own algorithms. (See also “PXI, AXIe Expand Measurement Options.”)

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