Detection means for the selective detection of gases, based on optical spectroscopy

Abstract

An optical detection system for selectively detecting gases comprises a light source emitting light thermally or mechanically modulated and supplied to a measuring cell. The light source includes an emitter enclosed in an ellipsoid reflector. The ellipsoid reflector can receive measuring gas directly, or is evacuated or filled with an inert gas which does not absorb in the measuring gas absorption range. With measuring gas supplied directly to the reflector, the light emanating from the reflector is supplied to a wide-band detector, combined with a monochromator, e.g. an optical narrow-band filter. With an evacuated or inert gas filled reflector, after traversing a monochromator, the light is irradiated into a photoacoustic detection cell containing the measuring gas. The photoacoustic cell is completely or approximately closed during measurement. Devices, providing the acoustic decoupling in the photoacoustic cell during the measurement and gas exchanges, can include capillaries in the cell wall, liquid cutout devices, mechanical valves or diaphragm pump-valve combinations. Microphone signals processed by a lock-in amplifier operating in a digital off-line manner and controlled by a microprocessor can control the system. The gas scavenging and signal processing of several gas detector units can take place with a single processor unit.

Dependencies are inferred from the claim text.