GB997481A - Improvements relating to arrangements for use in measuring the liquid content of a container - Google Patents

Abstract

997,481. Measuring by ultrasonics. BURNETT & ROLFE Ltd. June 4, 1962 [March 2, 1961], No. 4176/61. Heading H4D. The contents of a container, e.g. the depth of liquid in a vessel, is derived from the propagation time of sonic or ultrasonic waves which are directed upwardly through the bottom of the container and reflected at the upper surface of the content. As shown in Fig. 1, which is concerned with measuring the depth of a liquid 2 in a horizontal cylindrical vessel 1, pulses of ultrasonic wave energy produced by a transducer 4 (e.g. a piezo-electric crystal) under the control of a circuit 5 and directed upwardly from the bottom of the vessel are reflected at the upper surface 3 and returned via the transducer 4 and circuit 5 to an indicator device comprising a neon lamp 6 carried by a balanced arm 7 which rotates synchronously with the transmission of pulses the arrangement being such that as the lamp lights up on passing the zero mark of a circular scale 12 and lights up again when a reflected pulse is received. The neon lamp is covered by a mask 9 having a narrow radial slot 10 so that the scale which is calibrated in terms of depth may be read accurately. In an alternative arrangement, the lamp 6 may be stationary and the scale rotated so that the latter forms a stroboscopic disc. The lamp and scale may be replaced by a cathode-ray tube indicator for the transmitted and reflected pulses and in either arrangement the indication may given the volume or weight of the material in the container. When a plurality of containers are involved a single indicating device selectively connected to the different containers by suitable means may be employed. To avoid difficulties due to very short propagation times which arise when the level of the reflecting surface 3 is very low a minimum path length may be introduced by mounting the transducer 4 at the end of a tube 10, Fig. 3 (about two feet long) filled with a coupling liquid. The tube may be perpendicular to the position shown and a 45 degrees reflecting surface employed to direct the ultra-sonic waves vertically upwards (Fig. 4, not shown). For mounting the piezo-electric crystal the latter is rigidly held in a cup-like member 20 (Fig. 5) which is screwed into a ring 21 welded to the bottom of the container and a liquid tight seal provided by an 0-ring 22. A spacer ring 23 prevents the member 20 from being screwed in too far and the latter ring and ring 21 are provided with respective openings 25, 24 through which a coupling liquid may be introduced into the space 26. The assembly is completed by a further cup-like member 27 screwed around ring 21. It is stated that the device may be arranged to control the level of the contents of the vessel by controlling the opening of a supply line or a discharge passage.