Patent ID: 6829946
Filing Date: 2004-12-14
Classification: G01F

Abstract:
An electromagnetic flowmeter comprising:a measuring pipe through which a fluid to be measured flows; an electrode which is arranged in said measuring pipe and detects an electromotive force generated by a magnetic field applied to the fluid and flow of the fluid; a first exciting coil which is arranged separately from a plane, which includes said electrode and is perpendicular to a direction of an axis of said measuring pipe, and applies a first magnetic field having a first frequency to the fluid; a second exciting coil which is arranged on a side opposite to said first exciting coil with respect to the plane and applies, to the fluid, a second magnetic field obtained by amplitude-modulating a carrier having the first frequency by a modulated wave having a second frequency; a power supply section which supplies an exciting current to said first exciting coil and said second exciting coil; a signal conversion section which separates a component of the first frequency from the electromotive force detected by said electrode to obtain an amplitude, separates one of components of sum and difference frequencies of the first and second frequencies from the electromotive force to obtain an amplitude, and obtains a ratio of the amplitudes; and a flow rate output section which calculates a flow rate of the fluid on the basis of the amplitude ratio obtained by said signal conversion section.