FIBER-OPTIC SENSOR OF LIQUID CURRENT VELOCITY HEAD Russian patent published in 1996 - IPC

FIELD: measurement technology; metering speed and velocity head of sea water current in natural water reservoir. SUBSTANCE: fiber coils of fiber interferometer are arranged on substrate surface possessing pressure gradient in current along its surface. Interferometer output signal is proportional to current velocity head irrespective of influence of hydrophysical interferences: temperature, hydrostatic pressure, etc. Hydroacoustic interferences are filtered off by means of low-frequency filter mounted at photodetector output. Dynamic range is extended by introducing feedback circuit in sensor circuit to control phase shifter inserted in one of fiber interferometer sides whose other side incorporates phase shifter for initial setting of working point in absence of current. For measuring velocity head of current from moving vehicle, feedback circuit is provided with comparator having reference-voltage source which sets signal proportional to vehicle speed. EFFECT: extended dynamic range; eliminated effect of vehicle speed on velocity head measurement results. 10 cl, 7 dwg