Patent ID: 7437949

Claim:
A tertiary mode vibration type Coriolis flowmeter comprising: at least one flow tube, supported at opposite end portions, having inflow and outflow ports; a drive device for alternately driving the flow tube; and a pair of vibration detecting sensors for detecting a phase difference that is proportional to Coriolis forces acting on the flow tube, wherein: in causing the flow tube to make a tertiary mode vibration using the drive device, the drive device is provided at a central antinode from among three antinodes generated by the tertiary mode vibration; the pair of vibration detecting sensors are arranged at two antinodes of the three antinodes of the tertiary mode vibration of the flow tube exclusive of the central antinode; a displacement polarity of the drive device and a displacement polarity of the vibration detecting sensors are set to be in opposite phase with each other; and in a positive feedback loop of an excitation circuit portion for exciting the tertiary mode vibration of the flow tube and the vibration detecting sensors, the excitation circuit portion is structured so that conversion is effected so that the displacement polarities, which have been in opposite phase with each other, are converted to be in phase with each other.