Electromagnetic flowmeter of the residual magnetism type

摘要

An electromagnetic flowmeter has identical exciting coils coupled to portions which exhibit residual magnetism. A control circuit delivers short durations of current to each coil such that the current polarity in each coil determines the polarity of the magnetic flux across the conduit due to each residual magnetic portion. Four states of magnetic flux are repeatedly produced, zero, of one polarity, zero and of the other polarity. Flow note is determined by the difference between sampled voltages in a zero state and a directly succeeding state to eliminate noise components.