Photometrische Vorrichtung und photometrisches Verfahren zum Ermitteln des Brennwertes eines Pruefgases

Die Erfindung betrifft eine photometrische Vorrichtung und ein photometrisches Verfahren zum Ermitteln des Brennwertes eines Pruefgases insbesondere Erdgas mit einer Messstrahlung (2) erzeugenden Strahlungsquelle (1) und einer Modulationseinheit (4) zum Modulieren der Messstrahlung (2), wobei im Wege der Messstrahlung (2) nacheinander eine Probenzelle (3) mit Pruefgas und ein Strahlungsempfaenger (6) angeordnet sind. Die Messsignale des Strahlungsempfaengers (6) werden einer Auswerteeinheit zugefuehrt, die zumindest einen Signalverstaerker (9) zum Verstaerken der Messsignale aufweist. Der oder die Signalverstaerker (9) verfuegen ueber Einstellmittel zum Einstellen des Verstaerkungsgrades des Signalverstaerkers (9) in Abhaengigkeit spektraler Eigenschaften der Messstrahlung (2), die das zu verstaerkende Messsignal erzeugt. Die in einem Summenspeicher (10) erzeugte Summe der verstaerkten Messsignale liefert den Brennwert des Gases. Die Erfindung erlaubt eine schnelle Ermittlung des Brennwertes mit Hilfe einer bedienungsfreundlichen spektroskopischen Vorrichtung und eines Verfahrens, das auf die Bestimmung der Anteile einzelner Gaskomponenten im Gasgemisch verzichtet.

WO 200011452 A UPAB: 20000419 NOVELTY - Signal amplifiers (9) are individually-adjustable in accordance with spectral distribution of the incident measurement beam (2). The evaluation unit includes a summer (10) for their outputs. DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for the method of use, in which spectral interactions are measured to calculate the calorific value of a sample gas. Preferred Features: The evaluation unit comprises a circuit. Adjustment is provided by sources of controlled voltages, controlling in turn, gains of the amplifiers. The evaluation unit is a computer including the summer. It multiplies the measured signals by stored gain parameters. A dispersive element, e.g. a prism (4) or grating, splits the measurement beam spatially. The detection cell includes adjacent detectors, each connected to a signal amplifier. The modulator is a spectral switch, selecting set spectral regions of the beam, with a detector (7). It is e.g. a rotary filter wheel. Alternatively, an interferometer is included with a beam splitter forming two optical paths, and a mirror adjusted by an actuator. The source radiates and the detectors receive, in the mid- or near IR. Spectra are stored for comparative purposes. The apparatus allows examination of interactions in the wavebands of C-H oscillation at 3-4 mu m, and/or of the first harmonic at 1.5-2 mu m wavelength. USE - To measure the calorific value of a gas using a photometric method. ADVANTAGE - The method, though superficially complex, is rapidly and easily carried out, improving on earlier, more direct but cumbersome calorimetric approaches. It is reliable and costs little to operate. Combustion thermal energy is released from oxidation of C-H bonds. The apparatus measures spectral energy absorption due to C-H bond oscillation. Results are weighed in accordance with spectral properties of the source. With appropriate corrections and/or comparisons, the calorific value can be estimated.