| 摘要 |
A sensor provided with a thin membrane is capable of storing electric charges and its surface is in contact with the chemical, biological and/or other physical parameters to be measured. The membrane is part of an electromechanical resonance circuit which works with continuous acoustic waves. Opposite to the membrane are arranged transducers provided with interdigital structures for emitting and receiving the continuous acoustic plate waves which act as narrow band filters. The emitting transducer and the receiving transducer are spaced apart by a propagation distance and the signal from the receiving transducer is capacitively detected. An appropriate electronic driving and evaluating circuit or a feed-back is provided between the output signal of the receiving transducer and the emitting transducer. Finally, a direct voltage is applied between the membrane and the emitting transducer, as well as between the membrane and the receiving transducer, upon which is superimposed an alternative voltage at the emitting transducer. The acoustic plate waves at the emitting transducer are solely generated by the electrostatic attraction or excitation between the interdigital structures of the emitting transducer and the membrane. The output signal of the receiving transducer is uncoupled in a capacitive manner in such a way that the oscillation amplitude of the acoustic continuous plate wave is measured in the receiving transducer by the capacitor formed by the interdigital structures of the receiving transducer and the membrane. On the emitting side, the membrane is spatially separated from the interdigital structures of the emitting transducer by a gap, and on the receiving side, it is spatially separated from the interdigital structures of the receiving transducer by another gap. There is no fixed mechanical connection between the membrane and the interdigital structures of the emitting and receiving transducers, so that the narrow gap forms a dielectric in which the membrane can move in the direction of the interdigital structures. |
