A sensor assembly for use within a portable medical infusion device for measuring the force generated by the drive system of said medical device when displacing a sliding member in a first direction to deliver a fluid to a patient, comprising: a beam structure comprising: an outer portion disposed about its periphery; a plurality of beams, each beam comprising an arm portion that extends radially inward from the outer portion to an end portion; an inner portion formed from the end portions of the beams; a sensing element disposed on each arm portion; a loading element mechanically coupled to the inner portion of the beam structure; and a rigid structure having a planar surface; wherein:. the outer portion is affixed to the planar surface of the structure; the end portion is separated from the planar surface of the structure by an airgap in the absence of a force applied by the loading element towards the structure; the arm portion of each beam of the plurality of beams is separated from the structure by a distance that is greater than a separation distance provided by the airgap; wherein the rigid structure is a back plate, and the beams are configured such that the end portions of the beams 302 contact the surface of the back plate when a force applied to the sensor assembly is greater than a threshold value, thereby limiting, preventing, or otherwise inhibiting additional deflection of the arm portions of the beams. a beam structure comprising: an outer portion disposed about its periphery; a plurality of beams, each beam comprising an arm portion that extends radially inward from the outer portion to an end portion; an inner portion formed from the end portions of the beams; a sensing element disposed on each arm portion; an outer portion disposed about its periphery; a plurality of beams, each beam comprising an arm portion that extends radially inward from the outer portion to an end portion; an inner portion formed from the end portions of the beams; a sensing element disposed on each arm portion; a loading element mechanically coupled to the inner portion of the beam structure; and a rigid structure having a planar surface; wherein:. the outer portion is affixed to the planar surface of the structure; the end portion is separated from the planar surface of the structure by an airgap in the absence of a force applied by the loading element towards the structure; the arm portion of each beam of the plurality of beams is separated from the structure by a distance that is greater than a separation distance provided by the airgap; wherein the rigid structure is a back plate, and the beams are configured such that the end portions of the beams 302 contact the surface of the back plate when a force applied to the sensor assembly is greater than a threshold value, thereby limiting, preventing, or otherwise inhibiting additional deflection of the arm portions of the beams. the outer portion is affixed to the planar surface of the structure; the end portion is separated from the planar surface of the structure by an airgap in the absence of a force applied by the loading element towards the structure; the arm portion of each beam of the plurality of beams is separated from the structure by a distance that is greater than a separation distance provided by the airgap; wherein the rigid structure is a back plate, and the beams are configured such that the end portions of the beams 302 contact the surface of the back plate when a force applied to the sensor assembly is greater than a threshold value, thereby limiting, preventing, or otherwise inhibiting additional deflection of the arm portions of the beams.