A sensor assembly for detecting an occupant on a seating surface of a seat, comprising: a first plate and a second plate disposed in the seat in an orientation that is substantially parallel to the seating surface, wherein the first plate and the second plate are substantially non-compliant; an elastomeric mat disposed between the first plate and the second plate, the elastomeric mat including an array of protuberances that extend toward and contact at least one of the first plate and the second plate, where the protuberances collapse by an amount indicative of an occupant weight when the occupant sits on the seating surface; and a switch mechanism affixed to at least one of the first plate and the second plate, the switch mechanism having a first state corresponding to an absence of the occupant whereby the protuberances of the elastomeric mat are not collapsed and indicating an occupant weight less than a threshold, and a second state corresponding the presence of the occupant whereby the protuberances of the elastomeric mat are collapsed and indicating an occupant weight greater than the threshold, characterized in that the first plate defines a first integrated fastener and said second plate defines a second integrated fastener configured to engage with the first integrated fastener effective to slidably couple the first plate to the second plate, limit motion such that the first plate and the second plate are separated by less than a maximum distance when the protuberances of the elastomeric mat are not collapsed, and allow translational movement of the first plate relative to the second plate effective to collapse the protuberances when the occupant weight is greater than the threshold and thereby cause the switch mechanism to indicate the second state. a first plate and a second plate disposed in the seat in an orientation that is substantially parallel to the seating surface, wherein the first plate and the second plate are substantially non-compliant; an elastomeric mat disposed between the first plate and the second plate, the elastomeric mat including an array of protuberances that extend toward and contact at least one of the first plate and the second plate, where the protuberances collapse by an amount indicative of an occupant weight when the occupant sits on the seating surface; and a switch mechanism affixed to at least one of the first plate and the second plate, the switch mechanism having a first state corresponding to an absence of the occupant whereby the protuberances of the elastomeric mat are not collapsed and indicating an occupant weight less than a threshold, and a second state corresponding the presence of the occupant whereby the protuberances of the elastomeric mat are collapsed and indicating an occupant weight greater than the threshold, characterized in that the first plate defines a first integrated fastener and said second plate defines a second integrated fastener configured to engage with the first integrated fastener effective to slidably couple the first plate to the second plate, limit motion such that the first plate and the second plate are separated by less than a maximum distance when the protuberances of the elastomeric mat are not collapsed, and allow translational movement of the first plate relative to the second plate effective to collapse the protuberances when the occupant weight is greater than the threshold and thereby cause the switch mechanism to indicate the second state.