Specific Features of Detection of Electric Characteristics of Conductive Liquids Using Normal Acoustic Waves

It is shown that the suppression of electromagnetic noise by at least 10 dB compared to the amplitude of the acoustic signal is of key importance in the measurement of the electric characteristics of liquid samples using normal acoustic waves, which can be achieved by placing the test sample in the gap between interdigital transducers on a plate and/or electronic suppression of interference in the measuring device. As distinct from the acoustoelectronic interaction of bulk and surface waves in piezoelectric semiconductors, the dependence of the absorption of Lamb modes in piezoelectric plates on conductivity σ of the liquid load is asymmetric. In this case, the selective measurement of conductivity σ is difficult due to the cross-sensitivity of waves to dielectric εl and viscous η properties of the liquid. It is found that σ ranges from 0 to 10 S/m under minor variations in parameters ε and η, the sensitivity of normal waves amounts to 0.4 dB/(S/m) with respect to amplitude and 4.4°/(S/m) with respect to phase, and the required sample volume is no greater than 200–500 µL.