Sensors, Inc.

Dynatech Electro-optics Corporation

Ross E Johnson

Keith Kaste

Edward L Tury

David O Danielson

Jacob Y Wong

Ronald B Alers

Larry J Schoennauer

A non-dispersive infrared gas analyzer especially adapted for measuring the concentrations of HC, CO and CO.sub.2 in a vehicle exhaust includes a sample chamber for holding a sample gas, a radiation emitter for directing a beam through the chamber and a detector for indicating the amount of radiation absorbed. A plurality of filters each of which transmit radiation at an absorption band of a gas component to be detected are alternatingly positioned in the radiation path to produce a time-multiplexed signal having concentration information for all gases. The time-multiplexed detector output is corrected for gain and offset errors 'on-the-fly', without requiring demultiplexing, through the use of an analog multiplier circuit. The correction factors are themselves determined without demultiplexing the detector output signal.

Method and apparatus for detecting a component gas in a sample

A non-dispersive infrared gas analyzer especially adapted for measuring the concentrations of HC, CO and CO.sub.2 in a vehicle exhaust includes a sample chamber for holding a sample gas, a radiation emitter for directing a beam through the chamber and a detector for indicating the amount of radiation absorbed. A plurality of filters, each of which transmit radiation at an absorption band of a gas component to be detected, are alternatingly positioned in the radiation path to produce a time-multiplexed signal having concentration information for all gases. A calibration assembly is provided which includes a plurality of calibration cells selectively positionable in the radiation path in order to provide an internal calibration standard for two-point calibration of each gas channel. The cells contain one or more of the gas components to be measured at concentrations and pressures predetermined to compensate for the difference in optical path length between the calibration cells and the sample chamber. A technique is provided for characterizing the calibration cells in situ after a conventional calibration, using bottled calibration gas, is performed.

Non-dispersive infrared gas analyzer system

Apparatus for inserting and removing several filters from an optical path and for determining at all times the instantaneous positional relationship of each filter with respect to the optical path includes a set of filters mounted on a carrier which is attached to a resonant piezoelectric system, and further includes reference tracks also located on the carrier and extending in the direction of the oscillatory motion and including a sequence of binary indicia progressing in the direction of the oscillatory motion. The reference tracks are read optically to produce a series of binary electrical signals which are processed to yield the instantaneous position of the carrier and filters with respect to a fixed optical path.

Resonant piezoelectric chopper for infrared radiation

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San Luis Obispo, CA, United States of America

Ross E Johnson