MAGNETIC LIQUID SENSOR FOR VERY-LOW GAS-FLOW RATE WITH MAGNETIC FLOW ADJUSTING POSSIBILITY

A gas flow rate sensor which is based on the change of magnetic proper ties of magnetic fluid due to gas bubbles is well known. A vessel fill ed with magnetic fluid is equipped with an exciting coil and two detec ting coils, the voltage difference between the coils, induced by bubbl es, being a measure of the flow rate. This type of device does not per mit simultaneously adjustment of the flow rate. This paper describes a new type of micro flow sensor, including the components of the experi mental equipment used. The bubbling gas flow rate, i.e. the frequency of bubbles, was measured up to 20 Hz. Under the influence of a nonunif orm or uniform magnetic field, due to first order magnetic levitation and magnetic pressure effects, supplementary forces of magnetic origin appear beside the gravitational one, which significantly modify bubbl e formation and emission frequency. Experimental data are presented co ncerning the characteristics of a model sensor illustrating the effici ency of magnetic adjustment of gas flow rate. (C) 1997 Elsevier Scienc e S.A.