| 摘要 |
1,169,821. Ultrasonic liquid level gauge. L'ECTRONIQUE APPLIQUEE. 6 Feb., 1967 [8 Feb., 1966], No. 5582/67. Heading H4D. In a liquid level gauge an ultrasonic pulse is emitted by a fixed transducer towards the liquid surface, reception of the echo pulse at the transducer initiates the emission of a succeeding pulse and the recurrence period of the resulting pulse train is measured. In the Fig. 3 embodiment a transducer 1 arranged either above or below the surface of liquid in a tank is coupled to pulse generator 7 which is triggered by the echo pulse. Output pulses at a frequency (1/t) determined by the separation of the transducer and liquid surface are applied from generator 7 to a gate 9 opened by pulses from generator 11 having a lower fixed repetition frequency (1/T). The first pulse passing gate 9 triggers bi-stable circuit 10, the second pulse passing gate 9 resets bi-stable 10 and the resetting of bi-stable - 10 causes gate 9 to close. Bi-stable 10 is thus in its triggered state for a period t in every interval T and meter 13 gives a reading proportional to t/T and thus indicates the liquid surface/transducer separation. To compensate for changes in the medium separating the transducer from the surface, the frequency 1/T may be made proportional to the ultrasonic wave propagation velocity in the medium by replacing generator 11 with a generator comprising a triggered pulse generator (15, Fig. 4) coupled to an auxiliary transducer (14) disposed in the same medium a fixed distance from a reflecting surface. For remote indication of liquid level in either the Fig. 3 or Fig. 4 system, the two series of pulses of periods t and T are applied to a mixer circuit and the mixer output is fed by cable to the remote location and then decoded (Fig. 5, not shown). In alternative embodiments providing a digital readout (Figs. 6 and 8, not shown), gate 9 is alternately opened and closed by the pulses of period t and clock pulses with a much smaller period T are applied to a counter (18) during the gate-open interval. Counter (18) is reset to zero by every other pulse t and its count (proportional to t/T) is indicated on a visual and/or printed readout 19. As in the Fig. 4 system, the frequency 1/T may be made proportional to the ultrasonic wave propagation velocity. |
