Description of Event or Problem · 0
THE USER HAD HIS PROSTHESIS EXPOSED TO THE DIRECT SUNLIGHT IN 80+ DEGREE WEATHER FOR 12 HOURS. THIS CAUSED HIS DARK-COLORED PROSTHESIS TO HEAT UP. THIS HEAT WAS TRANSFERRED THRU THE PROSTHESIS SOCKET TO THE DOME ELECTRODES. BECAUSE THE DOME ELECTRODES ARE METAL THEY ARE GOOD AT CONDUCTING HEAT. THIS CAUSED THE HEAT TO BE TRANSFERRED FROM THE HOTTER PROSTHESIS SOCKET TO THE COOLER SKIN OF THE USER. THIS FACT WAS STRENGTHENED BECAUSE THE ELECTRODES CONCENTRATED THE HEAT AND THE AREAS OF THE BLISTERS WERE CLOSE TO THE DOME ELECTRODE PLACEMENT OF THE SOCKET. THEY WERE NOT EXACTLY LINED UP WITH THE DOME ELECTRODES, BUT VERY CLOSE. THIS IS ANOTHER REASON WE BELIEVE IT IS NOT AN ELECTRICAL BURN. IF IT WAS AN ELECTRICAL BURN, THE MARKS WOULD HAVE LINED UP EXACTLY WITH THE DOME ELECTRODES. THIS IS AN ISSUE THAT WE DID NOT SEE WITH THE GEN1 DEVICE. WE BELIEVE THIS TO BE THE RESULT OF A NUMBER OF COMPOUNDING FACTORS: 1) RECENT TRENDS IN PROSTHESES TO BE CONSTRUCTED OF ALL-BLACK SOCKET MATERIALS; 2) REDUCED POWER CONSUMPTION FROM THE GEN2 SYSTEM; AND 3) THE ENHANCED FUNCTIONAL PERFORMANCE OF THE GEN2 SYSTEM. WHEREAS SKIN-COLORED PROSTHESIS WERE POPULAR A FEW YEARS AGO, DARK COLORED SOCKETS, ESPECIALLY BLACK CARBON FIBER, ARE BECOMING MORE POPULAR. THE BLACK MATERIALS ARE CONDUCTING AND RETAINING MORE HEAT FROM THE SUN AND HIGH AMBIENT TEMPERATURES. WITH PROLONGED WEAR OF A PROSTHESIS THAT IS RETAINING SO MUCH HEAT, THE INTIMATELY FITTING RESIDUAL LIMB IS ACTING AS A FLUID COOLING SYSTEM THAT CAN ONLY DISSIPATE SO MUCH HEAT. AFTER SIGNIFICANT WEAR, THIS CONDUCTED HEAT CAN BURN THE SKIN. REDUCED POWER CONSUMPTION AND GREATER FUNCTIONAL PERFORMANCE OF THE GEN2 DEVICE COMBINE TO MEAN THE USER CAN 1) WEAR THEIR PROSTHESES FOR LONGER PERIODS OF TIME, AND 2) CHOOSE TO WEAR IT FOR A WIDER RANGE OF FUNCTIONAL ACTIVITIES, SUCH AS OUTDOOR CHORES. ALL OF THESE FACTORS HAVE CONTRIBUTED TO THE HEATING UP OF THE PROSTHESIS AND TRANSFERRING THAT HEAT TO THE SKIN THRU THE DOME ELECTRODES. ALSO, WHEN THE USER STARTS TO SWEAT UNDERNEATH THE PROSTHESIS LINER, THE SWEAT CANNOT EVAPORATE. THIS CAUSES MORE HEAT TO BE TRANSFERRED FROM THE PROSTHESIS SOCKET THRU THE DOME ELECTRODES TO THE USER'S SKIN. TO DETERMINE THAT IT WAS NOT AN ELECTRICAL SHORT CAUSING THE MARKS ON THE USER'S SKIN, EXTENSIVE CONTINUITY TESTING WAS PERFORMED. IT WAS DISCOVERED THAT THERE WAS NO ELECTRICAL CONDUCTIVITY PRESENT BETWEEN ANY OF THE DOME ELECTRODE CONTACTS AND BATTERY SYSTEM, POWER/CHARGING SYSTEM, PROSTHESIS COMPONENTS, OR EXTERNALLY EXPOSED CONDUCTIVE AREAS. THERMAL RISE (UNDER NORMAL OPERATING CONDITIONS) TESTS WERE THEN PERFORMED: PRIOR TO ANY PROSTHESIS DISASSEMBLY, VARIOUS THERMAL EVALUATIONS WERE CONDUCTED USING A FLIR TG165 THERMAL MEASUREMENT GUN. AMBIENT TEMPERATURE OF TEST ROOM AND PROSTHESIS PRIOR TO POWER-ON WAS 77.5°F. AFTER 17 MINUTES OF PROSTHESIS POWER-ON, THE WARMEST AREA OF THE OUTER SOCKET REACHED A STEADY STATE OF 82.7°F, WITH A MAX, ONE-TIME MEASUREMENT OF 86.6°F. MEASURED TEMPERATURES OF DOME ELECTRODES ON THE SOCKET INTERIOR DID NOT EXCEED THE EXTERNAL TEMPERATURES. ALL MEASURED TEMPERATURES INDICATE NORMAL OPERATION. THERMAL FOCUS WAS MADE DIRECTLY ON THE COAPT CONTROLLER UNIT AND A 'CONTROL' CASE OF A 2ND (ON BENCH) CONTROLLER. BOTH CONTROLLERS MATCHED IN SURFACE TEMPERATURE UNDER POWER, AS WELL AS MATCHED IN POWER DRAW (APPROXIMATELY 0.42W). ALL MEASURED TEMPERATURES WERE AS EXPECTED. IT IS SURMISED THAT SUN EXPOSURE OF THE BLACK SOCKET WOULD HAVE RAISED THE SURFACE TEMPERATURE MUCH HIGHER THAN THE SYSTEM'S OPERATING TEMPERATURE.