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Abstract

Gas analyzers of the non-dispersive infrared radiation type which are designed to measure the concentration of one gas in a mixture of gases containing that gas. An infrared radiation emitter is employed to emit energy at a frequency of 40-100 Hz with a system which includes a source driver and a timer; and a detector is used to intercept the attenuated beam after it has passed through the mixture being analyzed and output a signal indicative of the concentration of the selected gas. Also, a second detector is preferably provided so that a ratioed, error eliminating output signal can be supplied to the failsafe, signal processing circuitry of the analyzer. The detectors are electrically biased by way of flyback transformer based circuitry to improve the signal-to-noise ratio, and the signal processing circuitry can be adjusted to compensate for drift. The detectors are mounted on a thermally conductive substrate along with appropriate filters, a filter frame, and a cover. The signal processing circuitry and an analog-to-digital convertor supply information to a microcomputer which: turns the infrared radiation emitter on and off and controls a heater which keeps the infrared radiation detectors at a constant, precise temperature. The microcomputer also supplies temperature, barometric pressure, and other compensation factors. Typically, a disposable airway adapter with an elongated, flanged casing will be included in the gas analyzer to confine the gases being analyzed to a path having a transverse dimension of precise and specific length and to provide an optical path across that stream of gases between the infrared radiation emitter and the infrared radiation detectors. The emitter and detectors are incorporated in a transducer head which has a U-shaped recess and can be detachably fixed to the airway adapter with a detent arrangement. This application is a continuation of application Ser. No. 146,284 filed Jan. 20, 1988 (now abandoned). U.S. application Ser. No. 146,284 is a division of application Ser. No. 024,770 filed Mar. 11, 1987 (now U.S. Pat. No. 4,859,858). Application Ser. No. 024,770 is a continuation-in-part of application Ser. No. 938,030 filed Dec. 4, 1986, by Daniel W. Knodle et al. and entitled GAS ANALYZERS (now abandoned).

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First Claim