| 摘要 |
A flowmeter sometimes called ultrasonic, but sometimes not ultrasonic including two phase locked loops, a portion of each of which form a common path through amplifiers, an electronic attenuator with automatic gain control, a pulse detector, and a pulse or phase comparator. The pulse comparator, through switches, controls first and second voltage controlled oscillators on a time shared basis. First and second counters are connected from the first and second voltage controlled oscillators, respectively. The first and second counters supply transmission pulses to submerged first and second facing transducers, respectively, at different times. The voltage controlled oscillators are always driven until a later counter pulse coincides with a corresponding received pulse. Time sharing is, in part, accomplished by beginning energy propagation in opposite directions at successive times and before either pulse is received.
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