Electromagnetic flowmeter

摘要

An electromagnetic flowmeter is energized by a tri-state excitation system having a first quiescent period, a first excitation period, a second quiescent period, a second excitation period for excitation with a polarity opposite to that of the first excitation period, and a third quiescent period. The electrode signals are sampled at equal intervals in each period except the second quiescent period and combined to provide an output which eliminates noise due to residual magnetic flux, electrochemical effects and commercial frequency.