| 摘要 |
PROBLEM TO BE SOLVED: To provide a flowmeter for accurately measuring a flow rate from high to low with a timer having high time resolution with low power consumption. SOLUTION: The ultrasonic flowmeter includes a first timer 16 and a second timer 17 disposed correspondingly to the propagation direction of ultrasonic wave. Each timer includes a ring oscillator where a plurality of sets of signal generating means 5a-5g constituted by an inverting means 10 and a delaying means 11 are interconnected in a ring shape, a counter 20 for counting the oscillations of the ring oscillator, and an arithmetic means 8 for calculating the period from the counted value of the counter 20 to determine the flow rate. A holding means 19 for holding the outputs of the signal generating means 5a-5g is disposed in each of the joints between the signal generating means 5a-5g interconnected in a ring shape. The output holding state of the holding means 19 can be selected according to a holding selection signal from a control section 4. By achieving the measurement mode according to the measurement application, the time resolution of the ring oscillator can be improved. COPYRIGHT: (C)2008,JPO&INPIT |
