Human Body Pyroelectric Passive IR Sensor - RE200B
The pyroelectric sensor (also known as Pyro-electric Infrared Transducer) is made of a crystalline material that generates a surface electric charge when exposed to heat in the form of infrared radiation. When the amount of radiation striking the crystal changes, the amount of charge also changes and can then be measured with a sensitive FET device built into the sensor. The sensor elements are sensitive to radiation over a wide range so a filter window is added to the TO5 package to limit incoming radiation to the 8 to 14 µm range which is most sensitive to human body radiation.
It is suggested to read both of the attached data sheets.