Recognition of a seat occupancy using a bladder transducer with an intermediate layer to prevent aging of the assembly

An arrangement for detecting when a seat is in use, esp a vehicle seat, comprises a padding layer (10) and a sensor layer (14) under it which detects forces acting on the padding layer. An intermediate layer (30) is located between the padding and sensor layers, and consists of a harder material than the padding, eg PUR. The sensor layer has numerous bubble type fluid cells (16) connected by a fluid channel (18).