When a communication is to be established, that too wirelessly, with a remote device, we typically employ optical radiations or radio waves or sometimes, acoustic waves (for underwater applications). These three types of wireless communications basically differ in their frequencies. All frequencies starting from frequency bands like LF, HF, VHF, UHF and so on, extending up to microwaves and millimeter waves are referred to as radio waves. Acoustic waves use ultrasonic portion of frequency spectrum. Optical Radiations use visible and infrared portion of the spectrum.
Fig. 1: Image Showing Wavelength Range of Infra red Rays in UV Spectrum
Fig. 2: Equation of Wein’s Displacement Law
Fig. 3: Equation Defining Emissivity
What is PIR Sensor?
Fig. 4: Image Showing Working of Passive Infrared Sensors
Fig. 5: Frensel Lens
Fig. 6: Image Showing Structure of A Typical PIR Sensor
Fig. 7: Diagrammatic Presentation of How PIR Sensors Work
Fig. 8: Image Showing How Signal Is Produced In A PIR Sensor
Passive Infrared Detectors : Classification
Fig. 10: A Typical Thermopile
Fig. 11: Image Showing A Normal Bolometer
Fig. 12: A Pyroelectric Detector
Quantum type PIRs
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