JPS56148015A - Electromagnetic flowmeter - Google Patents

Abstract

PURPOSE:To obtain a rectangular wave exciting system electromagnetic flowmeter of less power consumption by controlling the amplitude and the cycle of the exciting current of given time width which is repeatedly supplied to an exciting coil so as to be inversely proportional to flow velocity, and obtaining a flow velocity from these values. CONSTITUTION:The amplitude and the repeated frequency of the exciting current of given time width which is repeatedly supplied to an exciting coil 6 are controlled so as to be inversely proportional to the flow velocity of a fluid, and a flow velocity signal is obtained from these values. For example, the amplitude and the cycle of the rectangulary wave current supplied to the exciting coil 6 from a power source 2 through a current-controlling circuit 3 and a switch 4 are controlled so as to be inversely proportional to the flow velocity respectively by employing the voltage signal between electrodes 81 and 82 on a pipe 7 and using a controller 10 and the like. Moreover, a reciprocal operation is performed in an arithmetic circuit 11 on the basis of the respective signals of the amplitude and the cycle to obtain a flow velocity signal. Thereby, the amplitude and the cycle are properly selected according to the flow velocity, so that power consumption can be decreased and the reliability of the measuring instrument can be improved.