Fundamental Behavior of Micro Gas Flow Sensor Using Magnetic Fluid

The fundamental properties of a differential voltage output type micro gas flow sensor using a magnetic fluid (MF) were studied. Gas bubbles entering the MF only pass through the upper sense coil around the MF cylinder, causing variation in the voltage generated by difference in the permeabilities of the MF and the gas. Thus the output from the differentially coupled sense coils around the MF cylinder is almost entirely due to the variation caused by the gas bubbles. This provides an extremely sensitive gas sensor in a simple configuration with superb response which is capable of detecting even a single gas bubble.