Fluid property and flow sensing via a common frequency generator and FFT
AssigneeHoneywell International Inc.
InventorsDavid Kubisiak, Ulrich Bonne
Life of this patent
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Abstract
A method and apparatus for using a common frequency generator for measuring selected properties of a fluid of interest via one or more heater and/or sensor elements. The common frequency generator may sequentially and/or simultaneously provide input signals to selected heater and/or sensor elements. Application of more than one frequency component by the common frequency generator enables the determination of one or more time and/or phase lags more efficiently, especially when using an FFT analysis technique. From the time and/or phase lags, the selected fluid properties including fluid flow speed can be determined.
Claims7
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;
- energizing means connected to said heater means for energizing said heater means, said energizing means providing a periodic time-varying input signal to said heater means to induce a transient elevated temperature condition in said heater means;
- output means for providing an output signal that is related to the resistance of said heater means;
- FFT means for determining a phase lag between the input signal and the output signal during the transient elevated temperature condition using an FFT analysis;
- and
- determining means for determining the selected property of the fluid of interest using the phase lag.
A method for determining a selected property of a fluid of interest using a heater element, wherein the heater element has a resistance that changes with temperature and is in thermal communication with the fluid of interest, the method comprising the steps of:
- providing a time-varying input signal to the heater element, the input signal causing a temperature change, and a corresponding resistance change, in the heater element;
- sensing the resistance change of the heater element;
- determining a phase lag between the input signal and the sensed resistance change of the heater element using an FFT analysis;
- and
- determining the selected property of the fluid of interest using the phase lag.
Dependencies are inferred from the claim text.