The assignee for this patent, patent number 8649012, is Drager Safety AG & Co. KGaA (Lubeck, DE).
Reporters obtained the following quote from the background information supplied by the inventors: "Optical gas sensors operate with a light source (radiation source), a photosensor and a measuring section located between the light source and the photosensor. A wavelength range, in which the target gas has a characteristic absorption, can be selected with a band pass filter. Thermal light sources, such as diaphragm sources or spiral-wound filaments, lasers or light-emitting diodes (especially in the IR and UV ranges) are used as light sources. Thermal light sources emit in a very broad spectral band. However, this causes a lot of energy to flow into spectral ranges that are not used to analyze and calculate gas concentrations. Such gas sensors therefore have low efficiency in terms of their energy consumption. In addition, their output cannot be modified rapidly without additional mechanical components, which limits the use of noise suppression methods at a simultaneously fast response time.
"By contrast, lasers lead mostly to a very good signal-to-noise ratio, but they are relatively expensive and must be thermally stabilized.
"Light-emitting diodes (LEDs) are substantially more cost-effective than lasers and emit in a limited spectral range, so that they are more efficient in terms of their energy consumption than thermal light sources. In addition, just like lasers, LEDs lend themselves to fast electric modulation. On the other hand, the spectral emission characteristic of LEDs shows a thermal drift, which is noticeable in a disturbing manner in thermally non-stabilized optical gas sensors."
In addition to obtaining background information on this patent, VerticalNews editors also obtained the inventors' summary information for this patent: "An object of the present invention is to provide an optical gas sensor, which permits accurate measurements even without thermal stabilization with an LED as a light source.
"According to the invention, an optical gas sensor is provided comprising a light-emitting diode (LED), a photosensor, a measuring section between the light-emitting diode and the photosensor and a control and analyzing unit. The control and analyzing unit determines a concentration of a gas in the measuring section from a light intensity measurement by the photosensor. The control and analyzing unit measures a forward diode voltage over the light-emitting diode at a known current and determines a temperature of the light-emitting diode, from the forward diode voltage detected over the light-emitting diode, based on a preset dependence of the forward diode voltage on temperature. The control and analyzing unit applies a correction function, that is a function of the light-emitting diode temperature determined, with which the measurement is converted to that of a preset temperature of the light-emitting diode.
"The control and analyzing unit is set up according to the present invention to measure the forward diode voltage over the light-emitting diode at a known current through the diode. The temperature of the light-emitting diode can be derived from the detected forward diode voltage by means of a predetermined dependence of the forward diode voltage on the temperature of the light-emitting diode. The dependence, known in advance, may be available, for example, in the form of a look-up table or a temperature characteristic calibrated in advance as a function of the forward diode voltage. The control and analyzing unit is set up, furthermore, to apply a correction function, with which the measurement is converted to a preset reference temperature, as a function of the light-emitting diode temperature determined. The concentration of the target gas in the measuring section can be determined in this manner independently from the temperature of the light-emitting diode.
"In a preferred embodiment, the control and analyzing unit is set up, furthermore, to operate the photosensor alternatingly in a mode for light intensity measurement and in a temperature-measuring mode, in which a preset, constant current is applied over the photosensor and the resulting forward diode voltage over the photosensor is detected. Based on a predetermined dependence of the forward diode voltage on the temperature of the photosensor, a correction function, determined in advance, is applied to the measurement of the photosensor in the control and analyzing unit as a function of the photosensor temperature, and the measurement is converted to that of a preset temperature of the photosensor.
"The present invention will be described below on the basis of examples in connection with the drawings. The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated."
For more information, see this patent: Beckmann, Udo; Fornasiero, Livio. Optical Gas Sensor. U.S. Patent Number 8649012, filed
Keywords for this news article include: Electronics, Light-emitting Diode, Drager Safety AG & Co. KGaA.
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