A sensing frame is disclosed. The sensing frame includes a first rail and a second rail. The first and second rails are constrained to move along a first axis parallel to the first and second rails. The frame includes a base and at least two guiding arms for ensuring that the first rail and the second rail move in anti-phase fashion along the first axis. First and second guiding arms are flexibly coupled to the first rail and second rail. The first guiding arm is flexibly suspended to the base at first anchoring points for allowing rotation of the first guiding arm, and the second guiding arm is suspended to the base at a second anchoring point allowing rotation of the second guiding arm. The sensing frame includes a plurality of coupling flexures and a transducer for sensing motion of the first and second rails.