Detecting a faulty electrical wire is no fun for any aircraft technicians. But imagine the task for those who take care of the Space Shuttle and its 235 miles of wire! Add the fact that physically inspecting wires is not just time-consuming, but potentially damaging to the wires themselves, and one can understand why NASA devised a noninvasive test device to do the job. Known as the Standing Wave Reflectometer (SWR), this device takes advantage of the fact that a break or short circuit within a wire will cause certain electrical signals to be reflected back to the point of origin. By measuring the time it takes for the reflection to occur, an SWR fault locator can determine the location of the problem allowing for a faster, safer, and less-damaging and disruptive repair.
Since its invention in 1999, NASA has built its own handheld SWR fault locators for inspecting the ships’ electrical and signal distribution systems. Given the noninvasive nature of this technology, it was only a matter of time before it was commercialized. And it has been done by Eclypse International Corp. (www.eclypse.org) of Corona, CA.
A developer and manufacturer of aircraft test equipment, Eclypse licensed the patented SWR technology from NASA, then used it with the help of SWR inventor Dr. Pedro Medelius to create a more robust, user-friendly, and affordable SWR fault locator called the ESP. It comes packaged in a bright yellow handheld case with an LCD display; numeric keypad, Test and Menu buttons, and various test leads.
Today, this invention is being used by the Department of Defense. But don’t expect to find it readily available on your local shop floor. Despite the ESP’s proven capabilities, the FAA has not recommended this technology for commercial/civil use.
At first glance, the Eclypse ESP handheld seems a bit Star Trekish. It seems hard to believe that this small device, with its single pair of positive/negative test leads, would be capable of accurately locating faults in an aircraft’s wiring harness.
Yet it can do just that, according to tests conducted by Australia’s Defence Technical Information Center (DTIC). In a 2003 DTIC report titled ‘An Evaluation of the Eclypse ESP Hand-Held Standing Wave Reflectometer,’ author Jim Quinn reported that the Eclypse ESP “was shown to operate successfully and quickly on coaxial cables, twisted pairs, shielded cables, and pairs of wires within multi-wire looms. For aircraft wire management this offers an improved fault location capability prior to repairs on the flight line or during maintenance.” (The entire DTIC report can be viewed online at http://stinet.dtic.mil/oai/oai?verb=getRecord
So how does the Eclypse ESP handheld work its magic? “The Eclypse ESP exploits the fact that in many cases the cables [in an aircraft] are electromagnetic transmission lines which propagate high frequency electrical signals,” Quinn explains; whether the wires in question are coaxial cables, twisted pairs, or wires bundled together in a loom. “The device utilizes the fact a short circuit or an open circuit on a transmission line is a point of reflection for a signal injected by the device. By transmitting signals over a frequency range the device can determine the type of fault and its distance along the wires.”
“What this means is that a technician can use the ESP or the higher-end ESP+ to detect a fault in an aircraft that is, say 114 feet away from their position,” says Christopher Teal, Eclypse’s marketing director. “You just clip the positive lead onto the wire in question, and the negative either to an adjacent wire or the airframe. The signals themselves cover from approximately 10 to 50 MHz. It only takes a few seconds for the device to send them out and display back the location of the fault, within 6 inches on either side of its actual location.”
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