Infrared intrusion detector

摘要

In an infrared intrusion detector which evaluates the body radiation of a burglar by means of a dual radiation sensor (3) having two sensor elements (18, 19) connected in a differential circuit for the purpose of producing an alarm signal, a functional monitoring and a detection of a sabotage attempt, for example by covering or spraying the input window is achieved by asymmetrically radiating the two sensor elements (18, 19) with a radiation source (11) through the input window. The asymmetry can be achieved by arranging the radiation source outside the plane of symmetry of the sensor elements or by an asymmetrically arranged auxiliary reflector. <IMAGE>