Liquid level torsional ultrasonic waveguide sensor

A two-zone torsional waveguide was investigated to sense liquid level H in a first zone and temperature T in an adjacent second zone for temperature compensation. Lab results utilized two aspects of mass loading. Relatively weak water/air interface echoes, of low SNR, exhibited much greater sensitivity to H than the end echo, in terms of flight time, for sensors made of an aluminum alloy, titanium, or 316SS (stainless steel). For 316SS, the interface echo sensitivity advantage was a factor of 19 over the end echo. Compared to the end echo, in terms of flight time, the interface echo appears less sensitive to bubble nucleation. For 316SS, at the end of a 90-minute test, the H error associated with the interface echo flight time was less than with the end echo, by a factor of 18.