| 摘要 |
An electronic circuit serving as an interface between a piezoelectric transducer and a circuit for processing a measuring signal provided by said transducer, said electronic interface circuit serving for providing a constant direct current to said piezoelectric transducer, and for pre-processing an electric signal provided by the transducer via a voltage modulator, said electronic interface circuit being connected to said voltage modulator by a cable having two terminals at each end, the two terminals at a first end of the cable being connected to the output of the voltage modulator and the two terminals at a second end of the cable being connected to said electronic interface circuit. In order to eliminate the error signals caused in particular by common mode interference voltages ("frame voltage"), said electronic interface circuit is characterized in that it comprises (a) a first direct current source for providing a first constant current to said transducer through an electric current loop; (b) a second direct current source for absorbing a second constant current returning from said transducer to said electronic circuit through said loop while said transducer is supplied with said first current; (c) one or a plurality of passive elements allowing to absorb the difference between said first constant current and said second constant current.
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