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.
** Photo Credit: Curt Suplee, National Science Foundation
Click Here for a high resolution image (6 MB, 3008 x 2000)