Patent ID: 6652468
Filing Date: 2003-11-25
Classification: G01J

Abstract:
A method for pulse-wise identification, measurement and/or warning of one or more specific gases by means of a sensor composed of: at least one pulsed, radiation-cooled infrared radiation source, electrical means for pulse-wise heating of the at least one infrared radiation source with single pulses of electric current and in any preferred sequence of time, at least one infrared detector which is adapted to the detection of pulsed infrared radiation from the at least one infrared radiation source, at least one infrared spectrally selective element that is arranged between the at least one infrared radiation source and the at least one infrared detector and is adapted to spectral selection of the infrared radiation corresponding to specific spectral characteristics of the one or more specific gases, an open or closed volume of gas that is arranged between the at least one infrared radiation source and the at least one infrared detector, optical means which are arranged to guide infrared radiation from the at least one infrared radiation source via the at least one spectrally selective element onto the at least one infrared detector through the open or closed volume of gas, and electronic means adapted to the registration, amplification, treatment and/or presentation of such electrical signals as result when the infrared radiation is brought to illuminate the at least one infrared detector through the volume of gas via the at least one spectrally selective element, said method comprising the steps of:operating the at least one infrared radiation source at a large temperature difference &Dgr;T1 between a lower temperature level To and a certain higher temperature level Tm, maintaining said higher temperature level Tm for a certain period of time &thgr;1 for each of said at least one infrared radiation source and within each of said single pulses of electric current, causing the duration of each resulting pulse of infrared radiation expressed as the temporal extension of said period of time &thgr;1 to comply with the relation &thgr;1>(C&rgr;d0/2&egr;&sgr;Tm4)&Dgr;T1 in which do is the actual physical thickness of those parts of the at least one infrared radiation source that are adapted to be heated to the higher temperature level Tm, &sgr;=5.67Â·10âˆ’12 Wcmâˆ’2Kâˆ’4 is the Stefan-Boltzmann constant, &egr;<1 is the emissivity, &rgr; is the density and C is the specific thermal capacity of the at least one infrared radiation source, andadjusting the values of Tm and &Dgr;T1 as required by means of an iterative process until &thgr;1 satisfies certain requirements of temporal resolution for said identification, measurement and/or warning.