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An electromechanical differential motion sensor is disposed to detect transverse motion of a first piece relative to a second piece. The sensor includes a base anchored to the first piece, a lever arm that engages the second piece, a hinge, a retention mechanism, and a fuse wire. The hinge connects

An electromechanical differential motion sensor is disposed to detect transverse motion of a first piece relative to a second piece. The sensor includes a base anchored to the first piece, a lever arm that engages the second piece, a hinge, a retention mechanism, and a fuse wire. The hinge connects the lever arm to the base, such that the lever arm rotates relative to the base when the second piece displaces laterally with respect to the first piece. The retention mechanism retains the electromechanical differential motion sensor in a closed position wherein a first jaw of the base is aligned with a second jaw of the lever arm. The fuse wire carries an electrical signal current, and extends through the jaws such that transverse motion of the second piece relative to the first piece deflects the sensor from the closed position to an open position, thereby severing the first fuse wire.

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1. An electromechanical differential motion sensor disposed to detect transverse motion of a first piece relative to a second piece, the electromechanical shear fuse system comprising: a base disposed to be anchored to the first piece, and having a first jaw;a lever arm extending from the base to en

1. An electromechanical differential motion sensor disposed to detect transverse motion of a first piece relative to a second piece, the electromechanical shear fuse system comprising: a base disposed to be anchored to the first piece, and having a first jaw;a lever arm extending from the base to engage the second piece, and having a second jaw;a hinge disposed along a hinge axis and pivotally connecting the lever arm to the base, such that the lever arm rotates relative to the base when the second piece displaces laterally with respect to the first piece;a retention mechanism disposed between the base and the lever arm and configured to supply a retention load that retains the electromechanical differential motion sensor in a closed position wherein the first jaw is aligned with the second jaw;a first fuse wire configured to carry a first electrical signal current, and extending through the first jaw and the second jaw, such that transverse movement of the second piece relative to the first piece sufficient to overcome the retention load deflects the second jaw relative to the first jaw from the closed position to an open position wherein the first jaw is not aligned with the second jaw, thereby severing the first fuse wire. 2. The electromechanical differential motion sensor of claim 1, further comprising: a current source configured to generate the first electrical signal current; anda controller configured to receive the first electrical signal current through the first fuse wire, and further configured to flag a shear event if the first electrical signal current is not received. 3. The electromechanical differential motion sensor of claim 1, further comprising a second fuse wire disposed parallel to the first fuse wire, through the first jaw and the second jaw, to carry a second electrical signal current from the current source to the controller. 4. The electromechanical differential motion sensor of claim 3, wherein the controller flags a shear event only if neither the first electrical signal current nor the second electrical signal current are received by the controller. 5. The electromechanical differential motion sensor of claim 1, wherein the retention mechanism comprises: a destructible retention pin connecting a first retention location of the lever arm to a second retention location on the base, such that the electromechanical differential motion sensor cannot open from the closed position into the open position without breaking the destructible retention pin. 6. The electromechanical differential motion sensor of claim 5, wherein the first and second retention locations are aligned in a plane normal to the hinge axis, when the electromechanical fuse sensor is in the closed position, and further comprising: a first ridge at the first retention location extending from the base towards the lever arm; anda second ridge at the second retention location extending from the lever arm towards the base, such that the first ridge abuts the second ridge when the electromechanical differential motion sensor is in the closed position. 7. The electromechanical differential motion sensor of claim 6, wherein the first ridge engages the second ridge when the differential motion sensor is in the open position, thereby preventing the electromechanical differential motion sensor from returning to the closed position after entering the open position. 8. The electromechanical differential motion sensor of claim 1, wherein the retention mechanism comprises: a plurality of detents in one of the lever arm and the base, situated opposite the hinge from the fuse wire; anda ridge extending from the other of the lever arm and the base, situated opposite the hinge from the fuse wire;wherein the ridge engages a first of the plurality of detents while the electromechanical differential motion sensor is in the closed position, but engages a second of the plurality of detents while the electromechanical differential motion sensor is in the open position. 9. The electromechanical differential motion sensor of claim 8, further comprising a spring biased to apply a spring force along the hinge axis that pushes the base and lever arm together, such that the spring force determines the retention load. 10. The electromechanical differential motion sensor of claim 9, wherein the hinge is a hinge pin passing through the base and the lever arm, and wherein the spring is an annular spring plate positioned on the hinge pin and biased by a retaining nut disposed on the hinge pin. 11. The electromechanical differential motion sensor of claim 1, wherein the lever arm engages a slot within the second piece. 12. The electromechanical differential motion sensor of claim 1, wherein the base has a retaining tab with a fastener opening disposed to receive a fastener that anchors the base to the first piece. 13. The electromechanical differential motion sensor of claim 1, wherein the first fuse wire is an insulated wire comprising a conductive wire core surrounded by an insulating sheath. 14. The electromechanical differential motion sensor of claim 1, wherein the first jaw and the second jaw are formed of a non-conductive material. 15. The electromechanical differential motion sensor of claim 14, wherein the non-conductive material is a ceramic. 16. The electromechanical differential motion sensor of claim 1, wherein the first and second jaws are biased together and have first and second cutting surfaces, respectively, and wherein the first and second cutting surfaces are angled oppositely with respect to the hinge axis, and converge towards the hinge axis. 17. A method for sensing transverse motion between a first piece and a second piece, the method comprising: running a fuse wire through a scissor passage comprised of a first jaw in a base anchored to the first piece, and a second jaw in a lever arm pivotably secured to the base such that the lever arm engages the second piece;transmitting a signal current through the fuse wire;biasing the lever arm towards a closed position wherein the first and second jaws are aligned, with a biasing load;severing the fuse wire when transverse motion of the first piece relative to the second piece is sufficient to overcome the biasing load, thereby rotating the lever arm relative to the base, such that the lever arm moves from the closed position to an open position wherein the first and second jaws are not aligned; andsensing resulting interruption of the signal current when the fuse wire is severed. 18. The method of claim 17, wherein biasing the lever arm comprises connecting the lever arm to the base via a destructible retention pin, such that the lever arm cannot move from the closed position to the open position without breaking the destructible retention pin. 19. The method of claim 17, wherein biasing the lever arm comprises retaining a ridge on one of the lever arm and the base against a plurality of detents on the other of the lever arm and the base, such that the lever arm cannot move from the closed position without the ridge shifting from one of the plurality of detents to another of the plurality of detents. 20. The method of claim 17, further comprising: resetting the lever arm into the closed position;replacing the fuse wire; andresuming transmission of the signal current through the replaced fuse wire.