Electromagnetic flowmeter

Abstract

Excitation coils apply a magnetic flux corresponding to the excitation current to a fluid. An electromotive force induces in the fluid and the amplified electromotive force is supplied to first and second filter circuits. The first circuit generates a predetermined signal upon reception of a signal of a frequency higher than a first frequency. The second circuit generates a predetermined signal upon reception of a signal of a frequency lower than a second frequency which is lower than the first frequency. The contents of a flip-flop are inverted at every given period. A selection circuit outputs one of signals having the first and second frequencies as an excitation signal in response to the contents of the flip-flop. In response to the excitation signal, an exciting circuit selectively supplies to excitation coils a first excitation current of a frequency higher than the first frequency and a second excitation current of a frequency lower than the second frequency. When the exciting circuit outputs the first excitation current and the second circuit generates the predetermined signal, and when the exciting circuit outputs the second excitation current and the first circuit generates the predetermined signal. Thereby the control circuit prevents the flip-flop from being inverted.