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Abstract

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.

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