The Next Generation of TDR Technology

Category Archives: Innovation

Professor Helps Launch Device for Detecting Shorts

Since then, she and her students have refined the science and helped launch a startup company called LiveWire Innovation. The company is installing the technology in airplanes, and their latest product is the FaultChaser, a handheld device that can be used on consumer products – like cars and trailers. It’s the first easy-to-use device for detecting shorts on live or dead wires.

“LiveWire has been doing a great job chasing faults around the world with the predecessor to this device, so it is cool to have one that anyone can use,” Furse said. “You don’t need to be an electrical engineer to use the FaultChaser, you just push the button and it tells you where the fault is.”

The core technology behind the device works by sending a secondary signal through a wire. When the signal reaches a short, it reflects back to the device, which calculates where the short is based on the time it takes to travel to and from the damaged area. The technique is called spread spectrum time domain reflectometry.

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Solve a Problem that Means Something to You

I was recently reading this article on the excitement of invention:

Making Ideas Happen

Recovered TWA 800 wreckage

The inspiration of solving a problem that means something to you totally resonated with me.  In 1998, in the aftermath of TWA800 and SwissAir111, I was working on methods to locate faults on electrical cables in aircraft.  The trouble was, most of the difficult-to-find faults only happened in the air/during use.  These ‘no fault found’ conditions were plaguing maintainers.  And then, in relatively quick succession, these two major aircraft crashes brought to light the challenges, the importance, and the value of finding these faults before they bring a major airliner down.  This was a problem that meant a lot to the hundreds of people in those aircraft and to their families, friends, coworkers, neighbors, and to me.

I could see the importance of locating the faults while they were still small, often intermittent, little arcs that only last a few milliseconds.  But I couldn’t see how to do it.  I tried converting the frequency domain reflectometry (FDR) method for use on live cables, but the broad spectral noise in the aircraft environment created havoc with the FDR signals.  It also didn’t look promising for testing on digital signal lines, because the FDR frequencies would have to be tuned out of the band of the digital aircraft signal in order to prevent interference.

That is when I hit upon the idea of using a CDMA code, basically your cell phone signal, to locate faults on live wires.  This Spectral Time Domain Reflectometry (STDR) system or its closely related spread spectrum time domain reflectometry system (SSTDR) allow the test signal to be buried well below the signal and noise on the aircraft lines (for instance, 53dB below at Milstd1553 signal).  This new idea suddenly let us test wires while they were fully operational, and to be able to locate very precisely the intermittent faults often seen on aircraft.  Dry arcs are typically caused by vibration, where the wire vibrates against another wire or the aircraft structure. Wet arcs are caused by wires with damaged insulation that is bridged by moisture or water on the wires.  Both of these types of faults were extremely difficult to locate before, and they would recur over and over, confounding the aircraft electrical technicians, before they would finally get bad enough that they could find them.  Now, we finally had a way to locate them before they became so bad!  It was incredibly exciting to see what this new method could do!  How it opened up possibilities we had never had before in electrical testing.  This was the start of an incredibly exciting time in raw research, and then development, and finally commercial application that became LiveWire Innovation.

The article Making Ideas Happen reminded me of this … how rewarding it has been to work on a problem that really matters, and how exciting it is to come up with a solution to a big problem, and see that solution come to life. It’s really exciting, really rewarding, and really fun!


– Dr. Cynthia Furse, founding scientist, LiveWire Innovation