Universal Synaptics -Scope of the Problem


Selecting the Best Technology For Troubleshooting
 No Fault Found / Intermittent Conditions

There is little argument that one of the most important things for success or even survival is having superior tools and technology.  As such we have seen the unparalleled development and fielding of complex electronic systems that support our defensive, communications, power, transportation, space, industrial, and other infrastructures.  Keeping these now critical systems running reliably, in the face of relentless aging, has made the role of maintaining these costly systems one of critical importance.

Test equipment manufacturers have been working diligently to develop equipment with expanded features and phenomenal accuracy to help test and service these systems, yet maintainers still find themselves increasingly unable to keep them running with any significant degree of sustained reliability or cost efficiency.  This is especially true in military and commercial aviation systems, where it is not uncommon to have 50 percent or more of all reported operational malfunctions going undetected and therefore unrepaired during subsequent static or ground-based testing.

Diagnostic labels such as NFF (No Fault Found) or CND (Can Not Duplicate) and their statistically increasing rates of use, quantify the direction and extent of this testing-void problem.

From a root-cause perspective, electronic malfunctions can be categorized as either hard or intermittent failures.  If it’s a hard failure, the failure repeats every time and there is an estimated $100 billion worth of test equipment in place to accurately test and diagnose these comparatively easy failures.  You might even say that it would be impossible to misdiagnose a constant failure.  However, if it were an intermittent failure some would say that your best tool is a big bag of luck, and luck can be reduced to a notion of increased probabilities.

The probability of traditional test equipment being able to detect a randomly occurring intermittent failure or event is extremely low.  There’s simply too much fixed scanning, sampling and digital averaging involved to capture a brief, one-shot, low-level failure causing event.  There’s hope however.

As a rule, active and passive electronic components either stop working altogether or drift out of their original design parameters over time. In contrast, all the electromechanical connectivity elements (wiring, connectors, crimps, splices, solder joints, relays, circuit breakers, flex circuits, backplanes, etc) or the part of electronics that “glue” all the components together, rarely abruptly fails.  Instead, like machinery, they loosen or degrade over time, due to thermal, vibrational and contamination factors occurring in their operational environment.  With age, their operation becomes compromised and their failure mode is mostly intermittent in nature.

Because of the random nature of the failure mode, direct testing with expensive and highly accurate digital technologies (Digitizers, DMMs, DSOs), or other on-off technologies are simply not going to work.  And to be practical, a lot of analog technologies will not work either when large numbers of circuits or wires need to be tested.  An expensive analog oscilloscope is no better than a simple $3.00 test-light when the 30 millisecond blink rate of the human eye is the limiting factor and you need to be detecting intermittencies at least into the microsecond range.  A Time Domain Reflectometer (TDR)  and Standing Wave Ration (SWR) can tell you a lot about conditions on a transmission line, but if the line does not exhibit any intermittency during their short test period, what are they going to report?  And if you are going to test longer or on multiple lines, you are going to have to put hundreds of these devices to work at the same time, which is not likely to take place.

One technology from Universal Synaptics is based on analog neural sensing technology that does work effectively to find intermittency. . With this method of testing, as exemplified by the IFD-3000, all lines or wires of interest are connected to 256+ individual sensors arranged as a neural network. If a change in current is sensed on any of the lines, the network will report a problem, as well as automatically identify the failing line.   The accompanying computer will then capture and display a trace of the severity and duration of the failure event and it will update an on-screen graphics display and report its physical address in Unit Under Test terminology.  At the end of testing, the time stamp of each intermittency is also available for printing along with a reliability validation report for documentation requirements.

While legacy testing methods for continuity, functional or reliability testing delivers rather poor or non-existent performance when testing specifically for age-related intermittency or reliability, the IFD-3000 delivers increased levels of performance that is literally millions of times better on any individual test line. In addition, because of the IFD’s parallel nature, the increased performance in probability is orders of magnitude better when large systems need to be tested. 

For a more in-depth discussion of comparable testing capabilities and other aging-intermittency/NFF testing issues, see related article “The Achilles Heel of Modern Electronics” available at the following link:

 www.evaluationengineering.com/archive/articles/0604/0604modern_electronics.asp