Test Highway to the Danger Zone

Larry Desjardin- October 3, 2012

Those who read my Day 1 and Day 2 accounts of Autotestcon last month noticed a lot of modular news: VXI, PXI, and AXIe.  This is no coincidence.  Military test is growing increasingly modular and Autotestcon is the premier military test conference.

When I say “military” test, I am referring to testing avionics and similar electronics deployed in military vehicles and weapon systems.  These electronic boxes and boards experience environmental and mechanical extremes, and occasionally fail.  That means somebody needs to diagnose and repair them.  And guess what? When they do, they aren’t normally located next to the Geek Squad counter at your local Best Buy.  They're typically located where the weapon systems are- in the danger zone.  The test equipment itself may be at a high desert hanger or aboard an aircraft carrier in any given corner of the world.  Perhaps the equipment is in a truck that is driven to a site. Each of the armed services has their own particular challenges, but they have one thing in common- the test equipment must be an order of magnitude smaller than traditional instrumentation so it can be readily deployed and use a minimum of space once it is.

Modular instruments to the rescue.  The elimination of displays, front panels, and redundant power supplies leads to a much smaller footprint.  In fact, the first modular standard, VXI, was specifically created to address this need.  You can read about its unique history here.  VXI not only addressed the military needs, but it also was designed to satisfy additional commercial needs, enabling a successful standard that could address both markets.  Anyone who walked the floor of Autotestcon could see the impact that VXI made on the industry.  25 years later it is widely deployed.

Since then, three more instrument standards have been created: PXI, LXI, and AXIe.  PXI is well known in the industry and to readers of Outside the Box, and is the most popular modular standard today.  AXIe is a large format modular standard that can be thought of as the “big brother” to PXI.  Its large board size and horizontal format enables very high power capacity per rack inch for power hungry applications.  In Getting small, does one modular standard beat the others? a case is made for the size reduction attributes of each of the three standards. So what about LXI?

While LXI is best known as an interface for traditional instrumentation, there is no rule that LXI instruments must have full size displays and keyboards.  Indeed, LXI can be thought of as a modular standard of half and full rack widths in one dimension, and rack unit heights (multiples of 1-3/4 inches) in another.  And, sure enough, there are purpose-built LXI instruments in these small form factors.  Additionally, every system needs programmable power supplies. For high power applications, LXI-based power supplies (often internally modular) are expected to dominate this product category.

While modular instrumentation brings good single digit reductions in test system size, the next quantum step is synthetic instrumentation.  With synthetic instruments, the basic building blocks of front ends and data converters are combined with powerful software to perform complex measurements.  The pieces may be reconfigured for the next device under test, or even the next test.  Key functional blocks are shared or migrated to software to further reduce hardware content and footprint.  The increasing use of programmable FPGAs within the measurement blocks gives system integrators additional flexibility in defining measurements. 

This trifecta of advanced data converters, programmable FPGAs, and powerful software is enabling the next leap in size reductions.  Combined with a modular instrument infrastructure, synthetic instrumentation is creating the test highway to the danger zone.  Expect to see it widely incorporated in the next generation of military test systems.