| 摘要 |
A sensor apparatus for detecting sludge in a tank, e.g. an oil storage tank, wherein sonar transmission and reception is effected by a transducer (29) whose acoustic centre is coincident with the centre of curvature of a liquid filled part spherical sonar dome part (15) of a housing (13) for the apparatus. The acoustic pressure waves consequently pass through the dome part of the housing in a direction normal to its surfaces thus minimising velocity, amplitude and phase changes of the waves as they pass to and from the transducer, and avoiding blind spots in the area monitored by sensor apparatus. Preferably, the apparatus further includes means (31, 33, 35, 37) within the housing for angularly moving the transducer (29) about two orthogonal axes which intersect at said centre of curvature. |
