Abstract: A method and apparatus for measuring the velocity of a fluid relatively independently of the physical properties of the fluid. This is preferably accomplished by spacing two sensor elements at different distances from a heater element. The present invention also contemplates minimizing the effects of the non-zero heater time lag and/or the non-zero sensor time lag for increased accuracy. This is preferably accomplished by either measuring the time lags and subtracting the values thereof from an uncorrected transit time measurement, forcing the sensor elements to track the thermal disturbance in the fluid thereby minimizing the effects of the sensor time lags, or measuring the transit time using sensors that have substantially zero thermal mass.

Abstract: A method and apparatus for determining selected fluid properties including thermal conductivity, pressure and/or temperature using a single heater element of the sensor, and in a relatively short period of time. This is accomplished by measuring a variable phase or time lag between an input signal provided to the heater element and a subsequent transient temperature response of the heater element.

Abstract: A method and apparatus for providing a more direct approach to determine the thermal conductivity, thermal diffusivity and specific heat of a fluid of interest, independently of the amplitude of the sensor output. This is preferably accomplished by measuring one or more variable phase or time lags between selected input and output AC signals, and directly deriving the thermal conductivity, thermal diffusivity and specific heat therefrom. Such derivation is therefore less dependent than amplitude-based sensors on occasional or unpredictable drift in sensor resistive elements.

Abstract: A solid-state oxygen microsensor measuring the potential difference (EMF) generated across two electrodes deposited on a solid oxygen ion conducting electrolyte and located in a constant temperature gradient in the same ambient atmosphere is provided. An output voltage of the sensor is proportional to the corresponding temperature gradient established across the electrodes and the oxygen partial pressure of the ambient atmosphere at such time. The solid-state oxygen microsensor is useful in the application of combustion systems, for example, to maintain and improve combustion efficiency levels and reduce undesirable emissions within the exhaust.