Full Title

Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm > by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water (involving the use of floats G01F23/30) > by measuring the variations of parameters of electromagnetic or acoustic waves applied directly to the liquid or fluent solid material > Acoustic waves