Novel optical fiber flow sensor based on magnetic-field-induced displacement

The paper reports a novel optical fiber fluid flow sensor which is based on the measurement of magnetic-field-induced displacement. This sensor can be used to achieve volumetric flow and mass flow as well. The mechanical part of the sensor is similar as that of conventional turbine flowmeter, except that the single turbine is replaced by a dual-turbine structure. The two turbines are connected with a spring, and their relative position is specially designed that, the rotation phase delay between the two turbines is proportional to the mass flow through the conduit. Two magnets are embedded in the two turbines respectively, and two magnetic field probes are used to measure the rotation phase of turbine by detecting the position of each magnet. The signals from the probes are transformed into light pulses by optical fiber shutter sensors and then transmitted to the central controlling room. A post processing unit receives the light signals, and then calculates out volumetric flow and mass flow value. Compared with other kinds of mass flowmeter, this sensor is rather cheap and inherently safe. Experimental results show that the error of less than I % could he achieved with this sensor.