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Type FAP-50-12/S-6 strain gage

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White and red paper package for an SR-4 strain gage. The package indicates the type, resistance, and gage factor of the strain gages inside. The back of the package notes the American and Canadian patents that cover the technology. The inside has a paper with installation instructions and individual strain gages, which are small pieces of red felt with two wires attached the them. The gages are then attached to a paper backing.

"...the Committee does not feel that the commercial use is likely to be of major importance." -- MIT Patent Committee

Professor Arthur Ruge felt differently about his strain gauge. Ruge invented the device in 1938 to help his graduate student John Meier complete his investigation of earthquake stress on elevated water tanks. It was simple: a tiny piece of high-resistance filament was bent in a zigzag pattern and fixed in a rigid base (glue). The gauge was applied to the surface he wanted to test. Any stress on the surface could be easily detected by measuring the changes in electrical resistance of the current running through the wires of the gauge. Having been granted full rights to his invention, Ruge began the patent application process. Discovering that E.E. Simmons of Caltech had invented the same device a year earlier, the two men together applied for the patent. In 1939, Ruge started a business with MIT Professor Alfred deForest to manufacture the SR-4 gauge (the initials S and R honor the inventors), a device used in virtually all commercial weighing scales, in every structural stress test -- and it even allowed astronaut Neil Armstrong to declare: "The Eagle has landed."

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