Characterization of PIR detector for monitoring occupancy patterns and functional health status of elderly people living alone at home.

Changes in the behavioral activity of elderly people living alone at home may be an indicator for the assessment of their functional health status. In this paper, we evaluate the characteristics of a pyro-electric infrared detector (PIRD) to identify any section of the room where detector will fail to respond and assess the number of detectors required to identify the movements of the occupant reliably. The experimental results suggest that the PIRD output decreases very sharply from 1 V at 3 m to 0.2 V at 5 m and is below 0.5 V for hand movements at detection angle of <20 degrees and >50 degrees . Hence, spatial sensitivity of PIRD is non-uniform at different distances for different walking speeds. If a detector is used in a room of dimension half the maximum range of the PIRD, there exist dead points where detection sensitivity is low giving rise to false alarms. Hence, a single detector installed in a room fails to respond to small movements in the extended range. Four detectors at each corner of the room help to increase the sensitivity of the detection whereby even small movements such as reading a book, telephonic conversation etc. can be identified.