Abstract: The chopped infrared radiation leaving a measuring and sample gas chamber in an infrared gas analyzer is passed through and into two serially arranged detection chambers which are connected to a differential pressure chamber with capacitive pickup. The chambers are filled with gas of the type whose concentration, in the sample gas, is to be detected. One of the detector chambers contains a thin black wire, a diaphragm on the outside may shield an adjustable portion of that wire from radiation. The wire absorbs all radiation it intercepts and heats the environment.

Abstract: A two-beam, infrared gas analyzer includes a front and a rear detection cell in each path filled with gas of the type to be detected; and a pressure-differential chamber with capacitor pick-up is connected to these front and rear cells. The rear cells are constructed to ensure substantially complete absorption of all radiation of the absorption band being characteristic of the component to be detected. In one example, filters are interposed between front and rear cells for broadband, i.e., nonselective attenuation. Alternatively, the rear cells are connected to a reservoir of the same gas to attenuate pressure variations. Either case enhances frequency selectivity by reducing cross sensitivity.

Abstract: The two beam analyzer has chambers traversed by infrared beams and passed through by test gas; the intensity of each beam is detected by a detector having chambers which are filled with gas of the same type as the gas to be detected (as a trace) in the test gas. Additionally, one beam path includes a selectivity cuvette or cell, filled exclusively with that type of gas, but at a rather low pressure.