Patent ID: 8068998

Claim:
An electromagnetic flowmeter comprising: an exciting coil that creates a magnetic field orthogonal to the direction of fluid flow inside a measurement tube; a first signal electrode provided in the measurement tube facing orthogonally to the magnetic field created by the exciting coil; a second signal electrode provided in the measurement tube facing orthogonally to the magnetic field created by the exciting coil; and an AC synchronizing circuit that generates pulse signals synchronous to the frequency of a commercial power source, comprising: a dividing circuit that divides the AC signals input from the commercial power source into divided AC signals; and a comparator that monitors the level of the divided AC signals from this dividing circuit wherein, if the level of the divided AC signals exceeds a first threshold value, the levels of the pulse signals are inverted from the first level to a second level, and if the divided AC signals fall below a second threshold value, which is lower than the first threshold value, the levels of the pulse signals are inverted from the second level to the first level; wherein the switching of the exciting current that is supplied to the exciting coil and the sampling of flow rate signals produced between the signal electrodes are conducted at a timing that is controlled by the pulse signals produced by the AC synchronizing circuit.