| 摘要 |
<p>An intervalometer (16) for determining the transit time of an ultrasonic energy pulse through a fluid medium employs an automatic gain control amplifier circuit (19) for amplitude stabilizing the electrical signal derived at a receiving transducer (14). The automatic gain control circuit (19) tracks both a rapidly increasing and a rapidly decreasing signal amplitude. In various embodiments, synchronous switching (300, 302) can be employed in conjunction with a single amplifier (212, 304) and a plurality of storage elements (211, 310) to rapidly scan a plurality of signal paths and for providing automatic gain control capability on each path. The intervalometer (16) further has a "slipped cycle" capability implemented by a microprocessor controller (120) for accurately determining arrival time when it is known that the signal pulse will be within a certain range of times. In addition, the relative time difference between two arriving signal pulses can be accurately determined using this method so long as the range of time difference is sufficiently small. The microprocessor controller (120) also provides for bad data rejection based upon limits applied to either transit time or signal amplitude.</p> |
