Patent ID: 8442781

Claim:
A driving device for a Coriolis flowmeter having a structure in which a pair of flow tubes constituting measurement tubes are opposed to each other, an electromagnetic oscillator is operated by the driving device to alternately drive the flow tubes in a rotation direction, and an electromagnetic pick-off detects a phase difference and/or a vibration frequency proportional to a Coriolis force acting on the pair of flow tubes when the pair of flow tubes are vibrated, to thereby obtain a mass flow rate and/or density of a fluid to be measured, the driving device comprising: an operational (OP) amplifier for amplifying an analog input signal from the electromagnetic pick-off; an analog to digital (A/D) converter for converting an analog signal output from the OP amplifier into a digital signal; a digital signal processor (DSP) for performing digital processing on the digital signal output from the A/D converter based on phase detection; and a digital to analog (D/A) converter for converting a digital signal having a processed data amount output from the digital signal processor (DSP) into an analog signal, wherein the digital signal processor (DSP) comprises: an amplitude measurement section for amplitude-calculating using a fast Fourier transform a spectral strength at a resonance frequency, as an amplitude value, from the digital signal output from the A/D converter; a zero-cross calculation section for measuring a number of changes per unit time of a sign bit of the digital signal output from the A/D converter, and outputting a measured value as zero-cross data; a phase-locked loop (PLL) for performing the phase detection based on the zero-cross data and the digital signal output from the A/D converter; a drive waveform generation section for generating an output waveform, as the digital signal having the processed data amount, by determining an amplitude of the output waveform based on an output from the phase-locked loop (PLL) and amplitude data from the amplitude measurement section; and a frequency computing section for calculating a frequency based on phase data output from the phase-locked loop (PLL).