Abstract: Received ultrasonic bursts of energy are rectified and converted into pulse trains and also envelope detected. The envelope is fed to a ramp generator whose output is threshold detected to provide an arrival delay signal corresponding in time to the peak amplitude of the received bursts. A regulator circuit varies the timing of the arrival delay signal to coincide with the next negative-going zero crossover of the pulse train. A timing generator provides a reference delay offset, relative to the transmission time of the ultrasonic bursts, by the expected transit time thereof. The timing of the reference signal is varied in the same manner as the arrival delay signal by the regulator circuit and compared with the positive-going zero-crossover in the pulse train next following the negative-going zero-crossover. This determines accurately the actual time of arrival of the bursts, using low components.

Abstract: The amplification of periodic or aperiodic pulses is varied by envelope detecting the received pulses and passing the resulting envelope waveform to a latching comparator which, when enabled, provides an output pulse whenever the input waveform has an amplitude which exceeds a predetermined value. An itegrator coupled to the output of the comparator is continuously operative to increase or decrease the gain of the amplifier according to the absence or presence respectively of the output comparator pulse. In this manner the amplitude of signals or pulses is automatically controlled despite circuit and transmission vagaries.

Abstract: Ultrasonic signals are transmitted alternately upstream and downstream in a fluent media. A reference signal timed to occur at the estimated time of arrival of the alternate signals is used to ascertain whether the actual signals arrive earlier or later than the reference signal. Control circuitry responsive to the early and late signals generates two signal levels associated with transmission direction which adjusts the time position of the reference signal until it coincides with the actual arrival times. One signal level is related to flow velocity. The other signal level is related to sound velocity in the fluent media.

Abstract: An ultrasonic speed of sound and flow metering system which may utilize only one pair of ultrasonic transducers by incorporating a unique time share feature. In one embodiment a direct synthesis of a frequency proportional to the speed of sound in a flowing medium is obtained using one voltage controlled oscillator. An additional direct synthesis of a data frequency proportional to the flow of the medium is derived from signals inversely proportional to sound energy transit times upstream and downstream.