Abstract: A load cell having a parallelogram configuration formed by a pair of spaced-apart, generally parallel force-receiving members interconnected by a cantilever beam and a parallel spacer beam. The cantilever beam projects perpendicularly from one of the force-receiving members, and its end is secured to the other beam by a flexure hinge. The ends of the spacer beam are secured to the force-receiving members by respective flexure hinges. In order to maintain the parallelogram configuration of the load cell, the length of the spacer beam is equal to the length of the cantilever beam from the beam's virtual pivot point to its end. Rotational moments imparted to the force-receiving members apply forces to the beams along their longitudinal axes without deflecting the cantilever beam, thus making the load cell insensitive to such moments. A reduced thickness portion instrumented with semiconductor strain gauges is formed in the cantilever beam near its point of attachment with the force-receiving member.

Abstract: A load disc having an annular flex plate connected to a pair of parallel mounting plates through respective support rings. The support rings are of unequal diameters so that compressive or tensile forces applied to the mounting plates cause the flex plate to spherically deform. The deformation of the flex plate produces tensile and compressive strains on opposite faces of the flex plate which are measured by strain gauges mounted on opposite faces of the flex plate. The flex plate is recessed away from the support rings at the points of attachment thereto so that the support rings intersect the flex plate at its neutral plane. Consequently, spherical deformation of the flex plate does not tend to expand or contract the support rings thereby allowing freer deformation of the flex plate and desensitizing the flex plate against lateral forces applied between the mounting plates.

Abstract: A strain sensor or extensiometer with electrical output designed to measure relative displacements between two axially spaced points on a stressed structure comprising an elongated body with two end sections and a centrally located flexible beam extending in a direction perpendicular to the longitudinal axis of the sensor body. Relative displacements of the end sections generate two opposing symmetrical torques at the ends of the beam. These torques or bending moments are impressed onto the beam through two sets of flexible bridges which are symmetrically located but unequally spaced on opposite sides of the beam. These two torques or couples cause the beam to bend evenly over its entire length. Resistance strain gages bonded to both sides of the beam at its center measure this bending.