To reduce power consumption by accurately obtaining the flow rate of fluid to be measured at a low excitation voltage.
The electromagnetic flowmeter comprises a measurement tube 11 where fluid to be measured flows, a pair of electrodes 12 that are opposingly arranged at the measurement tube 11, an excitation coil 13 for giving flux in a direction for nearly orthogonally crossing the direction of the tube axis of the measurement tube 11 to the fluid to be measured, an excitation means 14 for supplying the excitation current of a waveform in a constant period to the excitation coil 13 for excitation, a sampling means 15 for sampling a voltage being generated at an electrode at two arbitrary points within the period where the primary differential values of an excitation current in the period are equal, and an operation means 16 for performing the operation of the fluid to be measured based on the voltage that is sampled by the sampling means 15. The excitation means 14 performs excitation by either a triangular or saw-tooth wave excitation current, and the operation means 16 obtains the flow rate (flow rate coefficient) of the fluid to be measured by obtaining the difference between the voltages at the two points that are sampled by the sampling means 15.
SAMEDA YOSHITOMI
IIJIMA TAKUYA
