A deformation passive sensor includes a system for detecting a variation in the distance between two points or regions of a structure, and a carrier having first and second parts configured to be fixed to the points or regions. The system includes a measuring assembly carried by the first part and actuatable only in one measurement direction in order to measure and store a measurement associated with at least one deformation in a measurement direction, and an actuating device including an intermediary assembly having an actuating member for actuating the measuring assembly, and an actuating assembly having a push part facing the intermediary assembly and configured such that the actuating member is moved with respect to the measuring assembly only when the second part moves in the measurement direction.