| 摘要 |
<p>A method and apparatus for measuring a predetermined parameter having a known relation to the transit time of movement of an energy wave through a medium by: transmitting from a first location (A) in the medium a cyclically-repeating energy wave (e.g., an acoustical wave, or electromagnetic wave); receiving the wave at a second location (B) in the medium; detecting a predetermined fiducial point in the wave received at the second location (B) continuously changing the frequency of transmission of the wave from the first location (A) to the second location (B) in accordance with the detected fiducial point of each wave received at the second location (B) such that the number of waves received at the second location (B) from the first location (A) is a whole integer; and utilizing the change in frequency to produce a measurement of the predetermined parameter.</p> |
