METHOD AND APPARATUS FOR DETERMINING RATE OF FLOWING LIQUID Russian patent published in 2013 - IPC G01F1/66 

FIELD: physics.

SUBSTANCE: liquid is heated by an optical heating beam. The heating point is illuminated with an optical detecting beam. Optical axes of the heating and detecting beams coincide at least at the heating point. The heating beam is a modulated or pulsed beam. The detecting beam is picked up by a detector array. The detector array takes several consecutive measurements during one light pulse of the heating beam, thereby determining the time characteristic of the refraction index of the heated area in the liquid. The apparatus for determining flow rate of a liquid has a pipe through which the liquid flows, a device for heating at least one area inside the liquid, a laser for generating measurement radiation and an electronic processing device. The pipe has a wall which is at least partially permeable for the measurement radiation. The device for heating a limited internal area of the liquid and an optical device which guides the laser beam are arranged such that the measurement beam illuminates the heated area at the exact heating point thereof. The heating device is a laser for generating intensity modulation or a pulsed heating beam. A focusing lens is made such that the optical axes of the heating and detecting beams coincide at the heating point and the detector array is designed to receive measurement radiation.

EFFECT: high accuracy of determining flow rate of a liquid in a pipe.

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