Extending the accuracy of ultrasonic level meters

Abstract

The applicability of instruments based on ultrasonic technology to determine variations of the level of liquids contained in tanks of arbitrary shape may be limited by the coherent interference of multiple reflections in the tank walls. This fact, which depends on the geometry, frequency and beamwidth, degrades the reliability of this kind of equipment, that usually requires expensive transducers and/or sophisticated reconstruction techniques to yield acceptable performances. Moreover, their behaviour is too sensitive to temperature or other external parameters to maintain an accurate response in any operating environment. Here a method to maximize accuracy and minimize sensitivity to perturbations is described. It is based on the use of the phase information contained in the main pulse of a complex echo pattern resulting from the sound reflecting in multiple objects. Its performance and the results of its application to a real case are studied.