Abstract
Electromagnetic flowmeters has been widely used since the introduction of pulsed DC excitation type in mid 70's. Pulsed DC excitation has improved the zero stability resulting higher accuracy, which is 0.5% of rate.
However, the type of pulsed DC excitation is liable to indicate significant fluctuation when applied to some kinds of slurry or low conductive liquids.
This paper describes particular characteristics of the flow-induced noise picked-up through the electrodes and proposes the technique called dual frequency excitation in order to reduce the flow-induced noise. This excitation method was realized by applying the magnetic field whose waveforms are superposed by low and high frequency. Measuring principle, practicable means and test results of the technique are demonstrated.
The dual frequency excitation has proved to be effective for reduction of the flow-induced noise without losing the advantageous features of good zero stability and quick response.
