A sensor assembly 40 for measuring seatbelt forces includes a first structural member 50 anchored to a vehicle structure and a second structural member 54 mounted for movement relative to the first structural member 50 in response to a seatbelt force (FIG. 2). A thin member 56 is mounted between the first 50 and second 54 structural members and provides a mounting surface for a sensor 58. The thin member 56 responds to movement of the second structural member 54 to provide high strain levels for the normal working range of the sensor 58. The thin member 56 is mounted between the first 50 and second 54 structural members such that the sensor 58 is isolated from movements due to non-axial loads. The first 50 and second 54 structural members are inter-related to define a maximum range of movement between the first 50 and second 54 members. Thus, overload protection is provided to prevent separation of the first 50 and second 54 structural members when a predetermined load limit is exceeded.