Patent ID: 6845330

Claim:
An electromagnetic flowmeter comprising: a coil which applies a magnetic field to a fluid flowing in a pipe line; exciting means for supplying an exciting current to said coil; noise eliminating means for eliminating noise from a measurement signal detected from the fluid under excitation by using a differential frequency component between a commercial power frequency and an exciting frequency; and arithmetic processing means for calculating a measurement flow rate on the basis of the measurement signal output from said noise eliminating means, wherein said noise eliminating means comprises: band elimination filter means for attenuating a component with a frequency f, of frequency components contained in a measurement signal detected from the fluid under excitation by supplying, to said coil, an exciting current with a frequency lower than both first and second commercial power frequencies used as commercial power, which satisfies f=|m 1 fex±n 1 fac 1 |=| m 2 fex±n 2 fac 2 | where fex is an exciting frequency, fac 1 is a first commercial power frequency, and fac 2 is a second commercial power frequency; and A/D conversion means for converting an output from the band elimination filter means into a digital signal.