Sensors, Inc.

Aerosport, Inc.

Charles P Howard

Donald Hugh Stedman

A metabolic rate analyzer is provided comprising a CO.sub.2 detector, an O.sub.2 detector, a flow resistance, a differential pressure transducer, a solenoid-actuated metering valve for producing a volumetrically-proportional sample of respired gas, a vacuum regulator for receiving the sample, a pump for drawing the sample from the vacuum regulator, and a processor for periodically sampling the differential pressure signal to provide a flow signal, to modulate power applied to the solenoid-actuated flow proportioning valve, and to provide a measure of the total volume of respired gas. The processor correlates the total volume of respired gas, O.sub.2 content and CO.sub.2 content to provide a measure of metabolic rate. Flow is recycled between the pump and the regulator valve to provide a source of mixed respired gas for analysis and digital integration of the flow signal provides a measure of the total volume of respired gas. A pulse generator driven by the microprocessor varies the frequency of pulses applied to the metering valve and the pulse width to provide volumetrically-proportional sampling and to control the effective sample volume of the analyzer, respectively. The processor determines the slope of the flow signal and increases the periodic sample rate of the pressure signal when slope is increasing and decreases the periodic sample rate when slope is decreasing to provide derivative augmentation of the sample period.

Metabolic analyzer

The metabolic rate analyzer comprises a flow proportioning valve for producing a proportional sample of the expired gas of the subject being studied. A sample cylinder is provided for drawing a proportional sample of the expired gas of the subject being studied from the flow proportioning valve. A test chamber is provided and an O.sub.2 sensor is provided. The test chamber is provided with a selectively-permeable membrane, the selectively-permeable membrane having a selective permeability for CO.sub.2, whereby CO.sub.2 is selectively vented from the test chamber. The sample cylinder is also used for charging the test chamber with the proportional sample of the expired gas of the subject. A pressure sensor is provided for monitoring the pressure of the sample and determining the rate of pressure decay in the test chamber due to the selective venting of CO.sub.2 through the permeable membrane. An analyzing means is provided for determining CO.sub.2 content in the expired gas from the rate of pressure decay in the test chamber, conducting a volumetric analysis of the proportioinal sample to determine total volume of expired gas, and then correlating O.sub.2 content, CO.sub.2 content and total volume of expired gas to provide a measure of the metabolic rate of the subject being studied.

Metabolic rate analyzer

The metabolic rate analyzer comprises a flow proportioning valve for producing a proportional sample of the expired gas of the subject being studied. A sample cylinder is provided for drawing a proportional sample of the expired gas of the subject being studied from the flow proportioning valve. A test chamber is provided and an O.sub.2 sensor is provided. The test chamber is provided with a selectively-permeable membrane, the selectively-permeable membrane having a selective permeability for CO.sub.2, whereby CO.sub.2 is selectively vented from the test chamber. The sample cylinder is also used for chrging the test chamber with the proportional sample of the expired gas of the subject. A pressure sensor is provided for monitoring the pressure of the sample and determining the rate of pressure decay in the test chamber due to the selective venting of CO.sub.2 through the permeable membrane. An analyzing means is provided fo determining CO.sub.2 content in the expired gas from the rate of pressure decay in the test chamber, conducting a volumetric analysis of the proportional sample to determine total volume of expired gas, and then correlating O.sub.2 content, CO.sub.2 content and total volume of expired gas to provide a measure of the metabolic rate of the subject being studied.

A gas analyzer for determining the concentration of the oxides of nitrogen in a sample gas is provided. The analyzer is particularly adapted for analyzing the exhaust from an internal combustion engine. In one embodiment, the analyzer comprises a sample chamber and a reference chamber. An arrangement is provided for delivering sample gas containing the lower oxide of nitrogen (NO) to the sample chamber and a quantity of ozone (O.sub.3) for reacting with this oxide of nitrogen and producing a chemiluminescence. After the chemiluminescence is completed, the sample gas is discharged to the reference chamber. A sample photodiode is disposed adjacent to the sample chamber for receiving light emitted from the sample chamber and producing a sample signal representative of the total photoemissivity of the sample gas. A reference photodiode is disposed adjacent to the reference chamber for receiving light emitted from the reference chamber and providing a reference signal representative of the dark current of the photodiodes and the background photoemissivity of the sample gas. A circuit is provided for conditioning and substracting the sample signal and the reference signal to produce an output representative of the concentration of the oxide of nitrogen in the sample gas. Dilution air is mixed with the sample gas either in the instrument with a viscous metering technique or in a sample probe, mounted in the exhaust of the engine, with a sonic metering technique. In other embodiments, a single sample photodiode is used to measure the chemiluminescent reaction and determine the oxide of nitrogen content of the sample gas.

Chemiluminescent gas analyzer for measuring the oxides of nitrogen

A liquid separator for a gas analyzer is provided comprising a sample gas inlet; a sample gas outlet; and a separation chamber in fluid communication with the gas inlet and gas outlet. The separation chamber is provided with a smooth, planar upper wall and a smooth planar lower wall, the upper and lower walls being substantially parallel and having a small uniform clearance therebetween. A motor is provided for rotating the lower wall of the separation chamber about a central axis normal to the surfaces of the upper and lower walls. The gas outlet is disposed on the central axis of the rotating lower wall. The gas inlet is disposed off of the central axis. A vacuum is applied to the sample gas outlet to draw sample gas through the separation chamber. A collection chamber is provided which surrounds the separation chamber for receiving liquids and other debris separated from the sample gas flow by contact with the rotating lower wall and centrifugal acceleration imparted thereto by the lower wall. A vacuum is also applied to the collection chamber to facilitate the exhaust of liquid and other debris from the separation chamber. The rapid response time and low flow rates of the separator make it particularly suitable for use in breath-by-breath, human gas analysis such as the art of capnography.

Liquid separator for gas analyzer

A gas analyzer for determining the concentration of the oxides of nitrogen in a sample gas is provided. The analyzer is particularly adapted for analyzing the exhaust from an internal combustion engine. The analyzer comprises a sample chamber and a reference chamber. An arrangement is provided for delivering sample gas containing the lower oxide of nitrogen (NO) to the sample chamber and a quantity of ozone (O.sub.3) for reacting with this oxide of nitrogen and producing a chemiluminescence. After the chemiluminescence is completed, the sample gas is discharged to the reference chamber. A sample photodiode is disposed adjacent to the sample chamber for receiving light emitted from the sample chamber and producing a sample signal representative of the total photoemissivity of the sample gas. A reference photodiode is disposed adjacent to the reference chamber for receiving light emitted from the reference chamber and providing a reference signal representative of the dark current of the photodiodes and the background photoemissivity of the sample gas. A circuit is provided for conditioning and substracting the sample signal and the reference signal to produce an output representative of the concentration of the oxide of nitrogen in the sample gas. Dilution air is mixed with the sample gas either in the instrument with a viscous metering technique or in a sample probe, mounted in the exhaust of the engine, with a sonic metering technique.

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Ann Arbor, MI, United States of America

Charles P Howard