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Protecting the Liberty Bell Image 4
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Protecting the Liberty Bell (Image 4)

June 29, 2010
Protecting the Liberty Bell (Image 4) A close-up view of the MicroStrain NANO-DVRT wireless sensors clamped to the Liberty Bell (the top and bottom sensors are the same design, but oriented perpendicular to each other). With even tiny motions of the crack--on the scale of millionths of a meter--the metal rod shifts its placement. The movement is detected by electrical coils, and that information is transmitted to a wireless receiver. The wires visible in this image are connecting the sensors to a wireless transmitter inside the Bell. This sensor technology--developed in part with support from the National Science Foundation's (NSF) Small Business Innovation Research program--was used on Oct. 9, 2003, to ensure that the Liberty Bell did not sustain further damage than its already-famous crack while being moved to its new (and present) location at the National Park Service's Liberty Bell Center, 6th Street between Market and Chestnut Streets in Philadelphia. While miniscule movements were detected during the move, none caused further damage to the bell. A Vermont company, MicroStrain, provided the gauges and monitoring system for free. To learn more about the Liberty Bell's move and it's history, see the NSF Special Report The Liberty Bell: Protecting an American Icon. (Date of Image: 2003) [One of several related images. See Next Image.]