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US 6,644,128 B1Granted
Flow meter
AssigneeABB Research Ltd.
InventorsAnthony Byatt, Thomas Kleiner, Daniel Matter, Philippe Prêtre
Life of this patent
Estimating the term…
Abstract
A photoacoustic effect is used in order to measure a flow rate of a flowing medium (M), in particular of natural gas. A light emitter (1) is used to produce in the medium (M) a sound wave (S) which is transmitted by the medium (M) and detected by a sound detector (2). The light emitter (1) is less exposed to the medium (M) than a diaphragm such as used in the ultrasonic method.
Claims9
A method for measuring a flow rate of a flowing medium by means of detecting a sound wave transmitted by the medium, comprising the steps of:
- producing the sound wave in the medium by irradiating the medium with light, the light having a wavelength which is absorbed by the medium;
- measuring a propagation of time of the sound wave or a Doppler frequency of the sound wave in order to determine the flow velocity, measuring in addition a propagation time of the sound wave independently of the flow velocity in order to determine a density of the medium by means of a sound detector and a light emitter that are arranged in a plane at least approximately perpendicular to a flow direction in order to determine a density of the medium.
A flow meter, comprising:
- a light emitter for producing a photoacoustic sound wave in a flowing medium, and having a sound detector arranged at a spacing from the light emitter, wherein the light emitter has a focusing optical system for focusing a light beam at a focal point inside the medium and a propagation time of the photoacoustic sound wave or a Doppler frequency change in the photoacoustic sound wave is measured in order to determine a flow velocity, the flow meter further including an arrangement of a second light emitter and a second sound detector in a plane at least approximately perpendicular to the flow direction of the medium for measuring a propagation time of a sound wave independently of the flow velocity in order to determine a density of the medium.
Dependencies are inferred from the claim text.