The internal pipe wall of magnetic flowmeters should be non-conductive to prevent generated electromotive force from short-circuiting. Usually the inside of metallic pipe is lined with insulating material. The lining limits applicable temperature range of measured fluid and also its reliability. A new structure is proposed, in which the insulating liner is eliminated. A potential distribution is formed on the pipe wall by applying voltage proportional to fluid flowrate. The potential distribution is kept almost identical to the flow-induced potential in the fluid so that no current flows across the boundary between fluid and wall. Therefore the output signal is exactly the same as that of conventional magnetic flowmeters.
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