| 摘要 |
PROBLEM TO BE SOLVED: To perform the simple correction of an instrumental error without the complicated operation of a vibrating system. SOLUTION: A coaxial double vibrating pipe 10 is constituted of an inner tube 1 and an outer tube 2. A vibrator 5 is provided at the center of the coaxial double vibrating pipe 10, and sensors 6 and 7 are provided at the symmetrical positions from the center. When the vibrator 5 is driven at the resonant frequency with a driving circuit 20, a mass flow rate Q in proportion to a phase difference signalΔT at the sensors 6 and 7 is obtained. An instrumental-difference changeΔE, which is generated from the change in temperature (t) and densityρof fluid to be measured flowing in the inner tube 1 with respect to the obtained mass flow rate, is determined as the sum of the following instrumental differences: the first instrumental-difference correcting value Ct from the temperature difference of the reference temperature and the actually measured temperature of the inner tube, the second instrumental- difference correcting value Cdt based on the temperature difference of the inner tube 1 and the outer tube 2 and third instrumental-difference correcting value Cf obtained with the instrumental error by the density difference of the fluid to be measured as the frequency difference. The mass flow rate Qa to be corrected is determined as Q(1+ΔE).
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