Leidl, A.A.Leidl2022-03-082022-03-081998https://publica.fraunhofer.de/handle/publica/303948The liquid sensor has several comb shaped electrodes (12,14,16,18) which are formed as an interdigital converter (20,22) producing an electroacoustic wave (24) from a transmitter converter (20) to a receiver converter (22). The number of finger pairs (26) of the interdigital converter, and the material from which the electrodes are made, are selected, such that a surface shear wave produced by the transmitter converter, and a volume shear wave produced by the transmitter converter, have different frequencies. The selected electrode material has a high mass per unit area. The selected electrode material has a low sound propagation speed. Respectively two fingers of an electrode are arranged near to each other in the interdigital converter, and form a pair (26). One pair of an electrode with an adjacently arranged pair of the second electrode, form a quartet of fingers. ADVANTAGE - Provides high sensitivity with respect to liquid characteristics and small sensitivity to adverse influence s.de608621patent1996-19630890