| 摘要 |
PROBLEM TO BE SOLVED: To correct a flow rate value of a mass flowmeter at a drift zero point value. SOLUTION: A measuring pipe where a fluid flows is shaken. Signals of a phase difference proportional to a Coriolis force acting on the measuring pipe are obtained from sensors 1, 1', and processed by analog signal-processing circuits 3, 3' to remove noise components. The signals are alternately switched by an S/C switching part 4. The signals are converted by a comparator 5 to a phase difference pulse signal. The Coriolis force is converted to a flow rate value by a CPU 6. In the absence of the flow rate, that is, when a control circuit 2 is kept on (SW1: on, SW2: off), a zero point value is obtained according to a command from the CPU 6. In the presence of the flow rate, i.e., when the control circuit 2 is kept off (SW: off, SW2: on), a drift zero point value is obtained from the zero point value. An actually measured value of the mass flowmeter is corrected with the drift zero point value. The mass flowmeter of a wide rangeability can secure a reliability.
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