A vehicle seat assembly including a rail pair defining a mounting rail and a triggering rail. One of the rails is supported on a floor pan of the vehicle and the other is adapted to support a seat cushion. The rails are moveably supported relative to each other. Also, included is a field effect sensor operatively supported by the mounting rail such that the field effect sensor can be positioned in a first range of positions as well as second range of positions relative to the triggering rail. The sensor is adapted to emit an electric field and to detect disruption of the field when the field effect sensor is positioned in the first range of positions.