Patent ID: 8047080

Claim:
An electromagnetic flowmeter for supplying an excitation current to an exciting coil for giving a magnetic field to a measurement fluid, detecting an electric signal occurring in the measurement fluid according to the magnetic field, and computing a flow quantity value based on the electric signal, said electromagnetic flowmeter comprising: a zero point measurement section which measures a zero point of the measurement fluid; a storage section which stores the measured zero point measurement value; a determination section which determines whether the difference between a preceding zero point measurement value stored in said storage section and a present zero point measurement value stored in said storage section is beyond a value range; and at least either a transmission section which transmits the determination result or a display section which displays the determination result when said determination section determines that the difference is beyond the value range; wherein when said determination section determines that the difference is beyond the value range, an output current, the excitation current, and an excitation method of said electromagnetic flowmeter are changed, and the zero point is then measured by said zero point measurement section and the zero point measurement value is stored in said storage section, wherein the excitation method is changed between (a) a three-valued excitation method based on three signal patterns and (b) a two-frequency excitation method at a high repetition frequency and a low repetition frequency or two-valued excitation method based on two signal patterns.