A PIR sensor detects changes in the amount of infrared radiation “seen” by the sensor
elements, which varies depending on the temperature and surface characteristics of the
object in front of the sensor.
When a person passes between the sensor and the background, the sensor detects the
change from ambient temperature to body temperature, and back again. The sensor converts
the resulting change in the incoming infrared radiation into a change in the output
voltage (VPIR(t)), as shown in the PIR
sensor motion detection principle. Other objects with the same temperature as
the background, but with different surface characteristics, will also cause the sensor
to detect a different emission pattern.Figure 2-1. PIR Sensor Motion Detection
Principle
The figure below shows a plot of the raw data captured from the sensor using Data
Visualizer. A hand is placed over the sensor and held there for a short time and then
removed.
Figure 2-2. PIR Sensor Raw Data Motion
Detection Using Data Visualizer
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