Abstract: A sensor having a mass that moves relative to a structure is disclosed. A spring mechanism applies a restoring force to the mass when the mass moves from an equilibrium position with respect to the structure. A first code scale is attached to the mass and viewed by a first imaging system that is fixed with respect to the structure. The first imaging system forms images of the first code scale that are used by a controller to provide an indication of the relative position of the mass with respect to the structure. The mass can be located in a sealed chamber in the structure that has a transparent liquid through which the mass moves. The first imaging can view the first code scale from outside the chamber through a transparent window in the chamber.

Abstract: A sensor having a mass that moves relative to a structure is disclosed. A spring mechanism applies a restoring force to the mass when the mass moves from an equilibrium position with respect to the structure. A first code scale is attached to the mass and viewed by a first imaging system that is fixed with respect to the structure. The first imaging system forms images of the first code scale that are used by a controller to provide an indication of the relative position of the mass with respect to the structure. The mass can be located in a sealed chamber in the structure that has a transparent liquid through which the mass moves. The first imaging can view the first code scale from outside the chamber through a transparent window in the chamber.