Pressure sensor for monitoring open-air exhibition sites and spaces in a monitoring region which can be defined

The pressure sensor is placed in or on the ground in order to detect unauthorised entry into a space or site. It has a signal conductor (10) which is surrounded by an insulation layer (11). In the event of deformation of the insulation layer (11), a potential change is produced on the signal conductor (10), which potential change is evaluated to produce an alarm signal. The signal conductor (10) is embedded in a sheath (17), together with a heating conductor (13). If moisture penetrates into the insulation layer (11), a current can be passed through the heating conductor (13) in order to vaporise and force out the fluid which has penetrated in.