Abstract: The invention provides an apparatus and method for fill level monitoring in which the height of contents in a container (10) is monitored. The apparatus comprises an ultrasound reciever (30) and signal processing means (50-56) adapted to receive signals from the receiver, the arrangement being such that the signal processing means (50-56) identifies a first signal (32), in use, which is representative of a wavefront (26) transmitted through the contents of the container (10) independently of the height of the contents in the container (10), and a second signal (34) that is representative of a wavefront (24) that is reflected from the interface (22) between the surface of the contents in the container (10) and the environment above the contents, and in which the signal processing means (50-56) uses the difference in travel time for the two wavefronts (24, 26) to provide a measurement of the level of the contents in the container (10).

Abstract: An electromagnetic acoustic transducer for generating ultrasound waves in an electrically conducting sample comprises a magnetic element for producing a static magnetic field, and a coil through which brief current pulses are passed to create a dynamic magnetic field, the interaction between the fields and the sample generating ultrasound waves. The current pulses are produced by an input circuit, and their characteristics are arranged so that the frequency content of the ultrasound generated is broadband. Output pulses produced as a result of the input pulses are then also brief (substantially the same duration as the input pulses) so that accurate measurement of the interval between one output pulse and the next is relatively easy. The transducer can therefore be used to measure accurately the thickness of very thin samples, and to detect near surface defects. The generating transducer may also be used for detection of the output pulses, or a similar but separate detecting transducer may be used.

Abstract: In the apparatus disclosed herein, a bone containing body member to be tested is placed between a pair of transducers and a predetermined sequence of tone signals having frequencies spanning a range from 200 to 600 kilohertz is transmitted through the body member, and the set of values representing the amplitudes of the corresponding received signals are stored. The set of values obtained with the body member between the transducer is normalized using a set of values obtained from the same sequence without the body member in place thereby to generate a third set of values which are compensated for the response characteristics of the transducer and related interfaces. A value corresponding to the rate of change of attenuation with respect to frequency is then calculated from the third set of values and is adjusted for the bone thickness, this adjusted value being related to characteristics of the body member. The bone thickness is determined by a broadband pulse echo measurement.

Abstract: A high liquid level sensor comprising a tubular probe, with a peripheral wall (6), and arranged to be suspended in a liquid container. An ultrasonic signal is transmitted around the wall (6) from a transmitting transducer (12) potted in a block (11), which is bonded to the inner surface of the wall, to a receiving transducer also potted in the block. A detector circuit connected to the receiving transducer via a lead (10) discriminates between the signal level when the probe is immersed in gas and the lower signal level when the probe is immersed in liquid, and provides a corresponding switched output.