VELOCITY MEASURING SYSTEM

摘要

1302632 Doppler systems FRIED KRUPP GmbH 19 April 1971 [5 March 1970] 23164/71 Addition to 1274054 Heading H4D The Doppler system of the parent Specification 1,274,054 is modified in that to reduce undesired side-lobes in the transducer array directional characteristic a star-connected inductor arrangement is connected across the 3-phase conductors, and the inter-transducer spacing in a direction oblique to a longitudinal axis of the array is made less than #/3, where # is the sound wavelength. In the embodiment of Figs. 1 and 3, where energization of transducers 1 by phases R, S, T gives a required wavefront W1 (Fig. 1), an undesired wavefront W2 is reduced by making X2 < #/3. The star-connected device 51 (Fig. 3) forces the sum of the voltage vectors supplying the transducers to be precisely zero, thus preventing any side-lobe generation in a direction normal to the plane of the transmitting array 2. A similar device, 511, is connected across the output lines R, S, T of receiving array 21. An auxiliary echo-sounding device with a verticallydirected sounding beam for determining water depth comprises a transmitter 53 for intermittently injecting a pulse via transformer 54 into common point 52 of the star-connected device 51, a transformer 541 and amplifier 56 for obtaining the resulting echo pulse via common point 521 of the star-connected device 511, and a timing unit 57 started by the injected pulse and stopped by the echo pulse. The depth measurement may be used at 62 to control the duration of the signals transmitted from array 2 for the Doppler measurement, so that the signal duration increases with depth. Capacitors may be used in conjunction with the star-connected devices (Fig. 4, not shown) to provide band-pass filtering for rejecting noise frequencies.