DEVICE AND METHOD FOR DETERMINING THE CONCENTRATION OF AT LEAST ONE GAS IN A SAMPLE GAS STREAM BY MEANS OF INFRARED ABSORPTION SPECTROSCOPY

摘要

Devices are known for determining the concentration of at least one gas in a sample gas stream by means of infrared absorption spectroscopy, comprising an infrared radiation source (12), the radiation of which is directable through an analytical cell (16), a sample gas stream being directable by means of a feed line (34) into the analytical cell (16) and out of the analytical cell (16), and a detector (22) capable of measuring an absorption spectra generated in the analytical cell (16), and a suction jet pump (30) arranged downstream of the analytical cell (16) by means of which the measurement gas can be conveyed through the analytical cell (16) and the feed line (34). Frequently, however, measuring errors occur due to pressure fluctuations within the analytical cell, or increased maintenance- and manufacturing costs arise. In order to prevent these, the present invention provides a control valve (60) that is arranged in a propellant gas line (48) leading to a propellant gas connection (44) of the suction jet pump (30), by means of which the pressure in the propellant gas line (48) can be regulated so that the propellant pressure in the propellant gas line (48) and in the propelling nozzle (52) of the suction jet pump (30) is regulated as a direct function of the feed pressure within the analytical cell (16) or in the feed line (34).