Fiber - - bragg grating sensor for measuring differential pressures and flow velocities

摘要

The invention relates to a fibre Bragg-grating sensor (1, 25) which is suitable notably for the measurement of differential pressures and flow velocities v1 in oil boreholes. The operating principle of the sensor provided for in the invention is based on the fact that by means of a transducer (1) having two pressure chambers (7a, 7b) a hydrostatic pressure difference between two liquid or gaseous media (11a, 11b) is converted into a longitudinal fibre expansion or compression and measured via the displacement in the Bragg wavelength DELTA lambda B of at least one fibre Bragg grating (3, 4). Embodiments of the invention consisting of sensors comprising two fibre Bragg gratings (3, 4) having opposite expansion characteristics, temperature-compensated transducers (1) and a plurality of transducers (1) in wavelength multiplex configuration are given as examples. One application of the invention is the measurement of a flow velocity v1 using a Venturi tube (23).