| 摘要 |
[Summary] [Object] To provide a signal processing apparatus which may always perform measurement with constant precision and performs phase measurement with high filtering performance and a small amount of computation even when a temperature of a fluid to be measured changes, air bubbles are mixed into the fluid to be measured, or the fluid to be measured rapidly changes from a gas to a liquid. [Solving Means] In a Coriolis flowmeter, a vibrator is operated to vibrate at least one flow tube or a pair of flow tubes (2 and 3). A phase difference and/or a vibration frequency proportional to a Coriolis force acting on the flow tubes (2 and 3) are/is detected by vibration detection sensors to obtain a mass flow rate and/or density of the fluid to bemeasured. The Coriolis flowmeter includes a frequency measurement unit (110) for measuring a frequency based on an input signal frequency of one of the sensors, of two flow rate signals obtained by A/D conversion on detection signals from a pair of the vibration detection sensors (7 and 8), a transmitter (120) for transmitting and outputting a desired frequency signal based on the measured frequency, frequency conversion sections (130 and 140) for adding (or subtracting) detection frequencies from the pair of the vibration detection sensors (7 and 8) to (or from) an output frequency of the transmitter (120) to perform frequency conversion, and a phase difference measurement section (150) for measuring a phase difference between respective frequency signals which are detected by the pair of the vibration detection sensors (7 and 8) and obtained by conversion by the frequency conversion sections (130 and 140). |
