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Sensor Technology
for Outdoors |
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Light 'ON'. Light 'OFF'. Sensor-controlled
Automatic lights are created by using motion sensors. This is where two different technologies are employed: HF-sensors (see page 76) are the ideal solution for indoors. Outdoors, only passive infrared (PIR) sensors are used.
Heat radiation as a remote controller
The heart of a PIR sensor system is what's called a pyro-sensor. This electronic component responds to any fluctuation in incident infrared heat radiation with a change in voltage.
As all individuals give off infrared radiation through body heat, they automatically change the thermal image detected by the sensor on entering the system's field of vision. The sudden rise in voltage this causes is processed by the electronics for switching 'ON' light.
For sensor systems to respond to movements within the detection zone, they are equipped with a segment lens. This divides the pyrodetector's field of vision into active and passive zones (zones not visible to the sensor). When a heat source crosses a zone boundary, the IR radiation received changes for the sensor which then emits a signal.
Multi-sensor technology
STEINEL has developed the multisensor system for applications placing particularly exacting demands on the size of the detection zone. Within the system, two or even three pyro-sensors are positioned at a specific angle to each other that adds their detection zones together.
Heat radiated from the human body
Any object with a temperature above absolute zero (-273° C) gives off electromagnetic radiation. Given the temperature range of the human body, this radiation lies in the infrared portion of the spectrum. It is used by infrared sensors to detect people moving.
The segment lens
focuses IR radiation from its surroundings onto the sensor and divides the areas covered in active and passive zones (zones masked out for the sensor). The boundary between these zones forms what is called a switching zone as the sensor registers any person or object crossing this boundary as a fluctuation in radiation and emits a signal.
The segment lenses used are simple Fresnel lenses or STEINEL's high-performance multi-lens.
Multi-sensor technology
increases the size of the detection zone by means of two (illustrated) or three identical pyro-sensors within the system.
Segment lenses
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STEINEL multi-lens technology
Multi-lens technology (MLT) provides uninterrupted coverage of a semi-spherical detection zone. This makes it the ideal lens system for motion detectors with double or triple sensors. |
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Fresnel lenses
Fresnel lenses provide the simplest means of segmenting the detection zone of an infrared detector. A system of individual lenses is arranged here in the form of an arc. With a maximum coverage angle of 180°, they can watch over an area of up to 225 m2. A second optical window below the main detection zone makes it virtually impossible to creep past underneath the sensors without being detected. |
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Reach
STEINEL sensors generally provide a max. reach of 12 m that may be shorter when walking in a radial direction (towards the sensor). |
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