Patent ID: 7369949

Claim:
An electromagnetic flowmeter comprising: a measuring tube through which a fluid to be measured flows; an electrode which is placed in said measuring tube and detects an electromotive force generated by a magnetic field applied to the fluid and a flow of the fluid; an exciting unit which applies, to the fluid, a time-changing magnetic field asymmetrical to a first plane which includes said electrode and is perpendicular to an axial direction of said measuring tube; a signal conversion unit which extracts a ∂A/∂t component irrelevant to a flow velocity of the fluid and a v×B component originating from the flow velocity of the fluid, from a resultant electromotive force of an electromotive force based on the ∂A/∂t component and an electromotive force based on the v×B component, with A, t, v, and B respectively representing a vector potential, a time, a flow velocity, and a magnetic flux density; and a flow rate calculating unit which extracts a variation component dependent on a parameter from the ∂A/∂t component extracted by said signal conversion unit, corrects a span which is a coefficient applied to a magnitude V of the flow velocity of the v×B component input from said signal conversion unit on the basis of the variation component, and calculates the flow rate of the fluid from the v×B component whose span is corrected, the parameter being at least one of a characteristic and state of the fluid and a state in said measuring tube which are independent of the flow rate of the fluid.