Extensive Knowledge - Instar IN-MOTION 500 Installationsanleitung

6. Extensive Knowledge

6.1. What is PIR&Microwave Motion Detector?
Ӽ PIR Detector:
PIR stands for Passive Infrared or Pyroelectric Infrared. PIR
sensors can be defined as detectors of warm-bodied targets
in motion. A stationary target cannot be detected. To detect
a moving target, the target must have a surface temperature
that is substantially different than the surrounding ambient temperature. Although
the usual targets of a PIR detector are warm objects (mammals, birds), the PIR sen-
sor will also detect a moving target that has a surface temperature that is significant-
ly lower than the ambient temperature. As long as the target is large enough, and its
surface temperature is detectably different than the ambient (higher or lower) - and
the target is moving - it can be detected by a PIR sensor.
Ӽ Microwave Detector
detectors are different than PIR motion detectors in that they are active devices.
They transmit energy and look for a frequency (Doppler) shift due to motion in the
covered area. The microwave motion detector sends out high radio frequency waves
and then detects the level of energy reflected back to the device. If the radio fre-
quency wave hits a moving object, the frequency changes and the motion detector
is activated. Microwave motion detectors by themselves would cause frequent false
alarms as microwave energy penetrates building material.
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The Microwave sensor detects motion through the
principle of Doppler radar, it is similar to a radar
speed gun. It sends out microwave pulses and mea-
sures the reflection off a moving objects. They cover
a larger area than infrared sensors, but are more vul-
nerable to electrical interference. Microwave motion
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