GB1307310A - Sonar apparatus - Google Patents

Abstract

1307310 Echo-sounders SMITHS INDUSTRIES Ltd 29 Nov 1971 [28 Aug 1970] 41419/70 Heading H4D A marine craft sonar affording a representation of the depth of an underwater target by a measure of the time interval between wave transmission and reception includes means for sensing the heave (i.e. vertical displacement from long-term mean level) of the craft and varying a delay in the sonar accordingly to compensate for changes in depth arising from heaving. The heave measurement may be effected utilizing an inertial, resistive vertical accelerometer or the Doppler shift in a received echo. The embodiments incorporate a known electrochemical chart recorder but a cathode-ray tube display may be provided as an alternative. Delaying instant of transmission, Fig. 1.-A D.C. signal dependent in magnitude and sense on heave is compared, 24, with the output of a ramp, 23, initiated at a predetermined point in the cyclic movement of recorder stylus 11 and on equality a pulse from unit 27 triggers transmitter 3. A transistor circuit for variable delay unit 20 is elaborated, Fig. 4 (not shown). Correcting echo time.-If heave between transmission and echo reception cannot be ignored, correction to echo timing is also effected, Figs. 5, 6 (neither shown).