| 主权项 |
1. System for non-intrusive and continuous level measurement of a liquid, where the liquid is enclosed by a solid wall of a horizontally lying, cylindrical vessel, the system comprising
an ultrasonic transducer mounted at the outside of the vessel wall for generating an ultrasound wave and for emitting it into the vessel wall, and at least one electronic control and data processing unit for controlling operation of the transducer and for determining the liquid level from a time of flight of the ultrasound wave,wherein
the transducer is a frequency-tunable transducer which is arranged to emit the ultrasound wave as a primary Lamb wave into the vessel wall so that a part of the primary Lamb wave leaks from the vessel wall into the liquid in form of a pressure wave, the at least one electronic control and data processing unit is adapted to
change the ultrasonic frequency of the transducer until the transducer receives a reflection of the emitted ultrasound wave in form of a reflection of the pressure wave,determine the corresponding time of flight, anddetermine the liquid level from the time of flight and from a corresponding and predetermined travel length of the emitted and reflected ultrasound wave, taking into account a predetermined speed of sound in the wall, a predetermined speed of sound in the liquid, a geometric dimension of the cross section of the vessel and the fact that the travel length must include a passage where the pressure wave is reflected by the vessel wall in a perpendicular upward direction to the surface of the liquid. |
