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The passive pyroelectric infrared sensor is introduced and the application
( Time：2015/9/26 Visits：738 )
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In the field of electronic anti-theft, human detector, passive pyroelectric infrared detector has a very wide range of applications, because of its low cost, stable technical performance and welcomed by the masses of users and professionals.
Working principle of passive pyroelectric infrared sensor and features:
the human body has a constant body temperature, generally in 37 degrees, so have a specific wavelength of about 10 um infrared, passive infrared sensor is detecting human around 10 um of ir.The human body through the thin mud around 10 um of ir, filter enhanced gathered on infrared induction.Infrared induction source usually USES the pyroelectric element, the element in receives the infrared radiation human body temperature changes will lose charge balance, to release charge, the follow-up circuit can generate alarm signal after testing treatment.
1) of the probe is based on the human body radiation detection target.So the pyroelectric element of wavelength for around 10 um should be very sensitive to infrared radiation.
2) to only sensitive to the infrared radiation of human body, usually covered in its radiation exchanges have special thin mud filter, obvious control action to the interference of environment.
3) passive infrared sensor, the sensor consists of two series or parallel each other pyroelectric yuan.And made of two electric polarization direction on the contrary, environmental background radiation on two pyroelectric element almost have the same effect, make its produce release electrical effects cancel each other out, so no signal output detector.
4) once the intrusion detection area, the human body infrared radiation through the focus of part of the mirror, and pyroelectric yuan receives, but two pieces of pyroelectric yuan receives heat, pyroelectric also different, not offset, the signal processing and alarm.
5) Philippines mud filter according to different performance requirements, with different focal length (induction distance), so as to produce different monitoring field, field of view, the more control the more closely.
The advantages and disadvantages of passive pyroelectric infrared sensor:
Advantages:
Itself does not send any type of radiation, the power consumption of the device is small, good concealment.Prices are low.
Disadvantages:
Pieces are easily influenced by all kinds of heat source, light interference
Passive infrared penetration is poor, the infrared radiation of human body easily obscured, not easy to be received probe.
Pieces are susceptible to radio frequency radiation interference.
Environment and human body temperature is close to, detection sensitivity and decreased obviously, sometimes causing short-term failure.
Anti-interference performance:
1.The small animals
Detector installed in the highly recommended to use, the detection range on the mainland to small animals, generally do not produce the alarm.
2.Resistance to electromagnetic interference
Detector electromagnetic interference resistance can meet the demands of the GB10408 4.6.1, general mobile phones does not cause electromagnetic interference.
3.Light interference
Detector sensitivity in the normal range, the 3 meters outside the H4 halogen lamp light through the glass, do not produce alarm.
Infrared pyroelectric sensor installation requirements:
Infrared pyroelectric body sensor can only be installed in indoor, its rate of false positives and the installation way of position and have a great relationship.
The correct installation shall meet the following conditions:
1.Infrared pyroelectric sensors should be from the ground 2.0-2.0 meters.
2.Infrared pyroelectric sensor away from air conditioner, refrigerator, stove, such as air temperature sensitive places.
3.Infrared pyroelectric sensor detection range shall not lie between screen, furniture, large potted plants or other quarantine objects.
4.Infrared pyroelectric sensors don't straight to the window, otherwise the heat flow disturbance and people moving out of the window will cause false positives, conditional best drew the curtain.Infrared pyroelectric sensor, also do not install in a strong current activities.
Infrared pyroelectric sensor is less sensitive to the human body and the movement direction of the relationship is very large.Infrared pyroelectric sensor for radial moving least sensitive reaction, for the transverse direction (i.e., a direction perpendicular to the radius) movement is the most sensitive. At the scene to choose the appropriate installation position is to avoid the infrared probe false positives, obtained the best detection sensitivity is extremely important.
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