Passive infrared heat sensing monitor for ceiling-mounted security system e.g. in warehouse or factory hall

摘要

An infra-red heat sensing monitor (1) for ceiling mounting is employed as part of a security system for detecting entry to a protected space. The monitor (1) contains standard paired pyro-electric sensors (3) within a transparent cover (8). Each sensor is aided by an optical array (7) incorporating Fresnel lenses or similar which concentrate the IR radiation from a given sector in the monitored space. In this way a full 360 deg. coverage up to a radius of 15 m is achieved with enhanced sensitivity including response to radiation from immediately below the monitor. Heat shielding covers selectively applied to the transparent cover can limit the space being monitored e.g. for blocking out heat from radiator units.