Patent ID: 6223593
Filing Date: 2001-05-01
Classification: G01F

Abstract:
Apparatus for determining a selected property of a fluid of interest, comprising:heater means in thermal communication with the fluid of interest, said heater means having a resistance that changes with temperature;heater energizing means connected to said heater means for energizing said heater means;sensor means in thermal communication with the fluid of interest and spaced from said heater means, said sensor means having a resistance that changes with temperature;feedback means coupled to said sensor means and said heater energizing means for causing said heater energizing means to energize said heater means a predetermined time after the resistance of said sensor means changes by a predetermined amount;said heater energizing means, heater means, sensor means, and feedback means forming a closed loop that oscillates at a frequency that is related to a time lag between the energizing of said heater means and the change of resistance of said sensor means by the predetermined amount; anddetermining means for determining a selected property of the fluid of interest using the frequency of oscillation.