Abstract: When outputs from two vibration detection sensors are measured by a Coriolis flowmeter in a form of phase difference time, a tube must be thinned to increase a sensitivity of the flowmeter to enable measurement and accordingly flow velocity and pressure loss increase, and a thickness of the flowmeter must be reduced and therefore a pressure resistance cannot be readily enhanced. In particular, the sensitivity of signals to flow rate is difficult to increase and, accordingly, a flow rate of a low-density gas cannot be accurately measured. In the present invention, a Coriolis vibration frame 16 carrying a U-shaped tube is swingably fixed to a forced vibration frame 19 fixed to a support base 22 to form a highly rigid frame structure limiting a vibrating direction to one degree of freedom in a Coriolis vibration direction. The forced vibration frame 19 is vibrated by a vibration exciter 20 so that a ratio of a forced vibration frequency to the Coriolis frequency of a pipeline is at least 1 to 10.

Abstract: When outputs from two vibration detection sensors are measured by a Coriolis flowmeter in a form of phase difference time, a tube must be thinned to increase a sensitivity of the flowmeter to enable measurement and accordingly flow velocity and pressure loss increase, and a thickness of the flowmeter must be reduced and therefore a pressure resistance cannot be readily enhanced. In particular, the sensitivity of signals to flow rate is difficult to increase and, accordingly, a flow rate of a low-density gas cannot be accurately measured. In the present invention, a Coriolis vibration frame 16 carrying a U-shaped tube is swingably fixed to a forced vibration frame 19 fixed to a support base 22 to form a highly rigid frame structure limiting a vibrating direction to one degree of freedom in a Coriolis vibration direction. The forced vibration frame 19 is vibrated by a vibration exciter 20 so that a ratio of a forced vibration frequency to the Coriolis frequency of a pipeline is at least 1 to 10.

Abstract: A flow rate measuring apparatus capable of accurately measuring a flow rate of fluctuating fluid. A mode setting circuit selectively sets any one of a plurality of predetermined transmission modes different in transmission timing. The mode setting circuit sets any one of a first transmission mode which permits an ultrasonic wave to be transmitted at a predetermined timing for every period of a flow waveform of exhaust gas, a second transmission mode which permits an ultrasonic wave to be transmitted at a timing shifted by a predetermined time for every period of the flow waveform of the exhaust gas and a third transmission mode which permits an ultrasonic wave to be transmitted at predetermined intervals.

Abstract: A flow rate measuring apparatus capable of accurately measuring a flow rate of fluctuating fluid. A mode setting circuit selectively sets any one of a plurality of predetermined transmission modes different in transmission timing. The mode setting circuit sets any one of a first transmission mode which permits an ultrasonic wave to be transmitted at a predetermined timing for every period of a flow waveform of exhaust gas, a second transmission mode which permits an ultrasonic wave to be transmitted at a timing shifted by a predetermined time for every period of the flow waveform of the exhaust gas and a third transmission mode which permits an ultrasonic wave to be transmitted at predetermined intervals.

Abstract: A control circuit (20) of a mass flow control device (1) retains the relation (Cd=f(ReTH)) between the Reynolds number and the actual discharge coefficient of a sonic nozzle (13) in the area where the Reynolds number is small. In such an area, the sonic nozzle can be used as a variable mass flow element for controlling mass flow rate. If a pressure Pu and a temperature Tu of an upstream fluid of the sonic nozzle 13 are detected, the theoretical mass flow rate QmTH and the theoretical Reynolds number ReTH can be calculated; since the actual discharge coefficient Cd can be calculated by the above relationship Cd=f(ReTH) based on the calculated Reynolds number, the actual mass flow rate Qm can be calculated based on the relation of Qm=Cd.multidot.QmTH.