A sensor is disclosed. The sensor includes a substrate and a mechanical structure. The mechanical structure includes at least two proof masses including a first proof mass and a second proof mass. The mechanical structure also includes a flexible coupling between the at least two proof masses and the substrate. The at least two proof masses move in an anti-phase direction normal to the plane of the substrate in response to acceleration of the sensor normal to the plane and move in anti-phase in a direction parallel to the plane of the substrate in response to an acceleration of the sensor parallel to the plane. The at least two proof masses move in a direction parallel to the plane of the substrate in response to an acceleration of the sensor parallel to the plane.