ApplicationNo. 05/608954 filed on 08/29/1975
US Classes:374/44, Thermal conductivity600/504, Measuring blood flow in body portion other than heart702/136, Thermal related property73/204.17, With distinct heating circuitry for a self-heated sensor73/204.18Including response characteristic or condition compensation
ExaminersPrimary: Goldstein, Herbert
Attorney, Agent or Firm
AbstractAppropriate heating and temperature sensing means are immersed in a medium the thermal conductivity, k, and thermal diffusivity, , of which are to be determined both in the presence of and in the absence of a flow of fluid therethrough. The method and system used for making such measurements operate in accordance with a thermal model of the heating means and the medium wherein the heating means is treated as a distributed thermal mass and wherein heat conduction occurs in a coupled thermal system which comprises both the heating means and the adjacent region of the medium which surrounds such heating means. The thermal conductivity of the medium is determined as a function of the temperature difference between the temperature of the unheated medium and the temperature of the heated medium, of the resistance of the heating means, of the power applied to the heating means, of the thermal conductivity of the heating means and of the radius of a spherical heating means having a volume equivalent to that of the actual heating means. In accordance with various embodiments of the invention the temperature difference and heating means resistance are maintained constant or are permitted to vary with time over the time period of measurement. Measurements of the thermal conductivity in the presence and in the absence of fluid flow permit a further measurement to be made of the rate of flow, ω, of a fluid which is flowing through the medium.