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Abstract

An electromagnetic flowmeter in which a low-frequency rectangular wave is supplied to the electromagnet coil of the flowmeter to produce an excitation current establishing a magnetic field which is intercepted by the fluid passing through the flow tube to induce a signal voltage in the electrodes disposed in the tube. This signal voltage is proportional to flow rate and is accompanied by an objectionable D-C noise component. To eliminate this noise component, the signal voltage is passed through a first high-pass filter, and to compensate for errors introduced by this filter, the signal voltage derived from the first filter is divided by a comparison voltage derived from the excitation current, but only after this comparison voltage passes through a second high-pass filter having essentially the same characteristics as the first filter.

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First Claim