Patent ID: 8725432
Filing Date: 2014-05-13
Classification: G01F,G01N

Abstract:
1. A signal processing method for a Coriolis flowmeter in which at least one flow tube or a pair of flow tubes which is included in a measurement flow tube is operated by a driving device using a vibrator to drive the at least one flow tube or the pair of flow tubes, and a phase difference or a vibration frequency proportional to a Coriolis force acting on the at least one flow tube or the pair of flow tubes is detected using a pair of vibration detection sensors when the at least one flow tube or the pair of flow tubes is vibrated, to thereby obtain a mass flow rate or a density of a fluid to be measured, the signal processing method comprising: performing frequency conversion to add or subtract the frequency of a modulatable frequency signal to or from the frequency of a first digital signal obtained by converting a first input signal from one of the pair of vibration detection sensors into the first digital signal; performing frequency conversion to add or subtract the frequency of the modulatable frequency signal to or from the frequency of a second digital signal obtained by converting a second input signal from the other one of the pair of vibration detection sensors into the second digital signal; measuring a phase difference between (i) the frequency converted first digital signal and (ii) the frequency converted second digital signal; obtaining a resonance frequency of the at least one flow tube or the pair of flow tubes based on the control signal, and calculating the density of the fluid to be measured based on the control signal.