What is a microwave sensor? What is a PIR? Which one is best?

Why Use A Microwave or PIR Sensor?

Microwave Sensors detect movement by sending out electromagnetic pulses and measuring the changes in frequency due to reflecting off- a moving object.
Why use a microwave sensor? From Fern Howard Ltd

How it works?

Choosing between presence and absence detection can make a significant difference to user-friendliness and energy saving. With presence detection, all movement is detected (including that from trees and animals if installed outdoors).

Presence Detection (auto ON and auto OFF)

Presense detection
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Presense detection 3

Absence Detection (manual ON and auto OFF)

absense detection_1
absense detection_2
absense detection_3