METHODS AND APPARATUS FOR REAL TIME FLUID ANALYSIS

A gas analyzer (10) integrated into the main passageway (11) of a breathing circuit includes pressure-drop flow element (12) that measures a pressure dr op across an orifice, an acoustic flowmeter (14) measures the speed of sound in the gas mixture, and a SAW device (20) from which the viscosity of the gas mixture is determined. The dielectric constant of the gas mixture is determined from the capacitance of spaced-apart charged plates of a capacito r (22) through which the mixture passes. The gas mixture density is determined from the measured pressure drop and flow rate, while the gas mixture specifi c heat is determined from the density and speed of sound in accordance with known relationships. The individual concentrations of five constituents of a mixture of gasses can be determined by solving five equations relating the independently measured properties of the gas mixture to the individual constituent concentrations.