Siemens Schweiz Ag

Stefan Walker

Martin Allemann

Aleksandar Duric

Brigitt Schmid

Mathias Stäger

Mathias Stager

Various embodiments may include a method for fire detection comprising: radiating light at a first wavelength into a scattered light volume and measuring a radiation intensity generated by forward scattering; radiating light at a second wavelength and measuring a second scattered radiation intensity generated by forward scattering; determining a first quotient from the scattered radiation intensities and comparing it to a first and second value; and if the first quotient lies between the first and the second value; radiating pulses at the second wavelength into and measuring a third intensity generated by backward scattering; determining a second quotient from the first and third scattered radiation intensity and comparing the second quotient with a third value; and generating a fire alarm if the second quotient exceeds the third comparison value.

Fire detection using the scattered light principle with a staggered activation of a further LED unit for radiating in further light pulses with different wavelengths and scattered light angles

A scattered-light smoke detector includes a detector unit that operates according to the scattered-light principle. The detector unit includes a light-emitting diode (LED) to irradiate particles to be detected and a spectrally sensitive photosensor to detect the light scattered by the particles. The LED and photosensor are aligned such that a principal optical axis of the LED and a principal optical axis of the photosensor define a scattered-light angle. The LED includes a first and a second LED chip for emitting first and second light beams with light in a first wavelength range and a different second wavelength range, and an LED chip carrier arranged orthogonally to the principal optical axis. The two LED chips are arranged side-by-side on the LED chip carrier. The LED is rotated such that a chip axis extending through the two LED chips is orthogonal to an angle plane defined by the two optical axes.

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Altdorf, Switzerland

Stefan Walker