Abstract: A double-tube type Coriolis flow meter is provided for measuring mass flow. The flow meter includes a straight flow tube (4) through which the fluid being measured flows, a hollow outer tube (5) secured at both ends thereof to act as a counterbalance, a drive unit (7), and a pair of sensors. The flow tube (4) is caused to vibrate by the drive unit (7) so that the mass flow of the fluid is measured by detecting a phase difference proportional to Coriolis force acting on the flow tube (4) by the sensors. Sheet members (coupling plates 6) secure the flow tube (4) to both ends of the outer tube (5) and integrally form the coupling plate (6) with tube-assembly supporting leaf springs (14) in the double-tube type Coriolis flow meter. By connecting the flow tube to the outer tube via the sheet members in this manner, stresses produced between the tubes are absorbed and a uniform temperature distribution is maintained in the outer tube and manufacturing costs are reduced.

Abstract: A resonantly drivable straight tube type Coriolis flowmeter which is capable of correcting instrumental errors caused by a change in density and temperature of measurable fluid. A coaxial double tube body that is composed of an inner tube wherein fluid to be measured flows and an outer tube with a balance weight attached thereto for equalizing natural frequencies of the inner and outer tubes is driven at a resonant frequency having a constant amplitude. A change of fluid density causes a change of amplitude ratio of the inner tube and the outer tube, resulting in shifting of an instrumental error. At this time, a resonant frequency detecting circuit detects a resonant frequency without detecting the amplitude ratio. An instrumental error detecting circuit stores a relation between resonant frequencies and fluid densities and a relation between fluid densities and instrument errors and conducts correction of an instrumental error according to the detected resonant frequency.