| 摘要 |
PCT No. PCT/EP94/03548 Sec. 371 Date Nov. 13, 1996 Sec. 102(e) Date Nov. 13, 1996 PCT Filed Oct. 28, 1994 PCT Pub. No. WO95/12123 PCT Pub. Date May 4, 1995A system for measuring fluid parameters of one or more liquids by an ultrasonic method comprises a voltage controlled oscillator; an ultrasonic resonator comprising one or more resonator cells, each of the resonator cells comprising an electro-acoustical transmitting transducer, an electro-acoustical receiving transducer, and a sample cavity between the transducers, wherein the transmitting transducer is connected to the output terminal of the voltage controlled oscillator; and a phase locked loop circuit comprising one of the resonator cells. The system also includes circuits for generating an ultrasonic frequency signal of variable frequency; applying the ultrasonic frequency signal to the transmitting transducer; responding to an output signal of the receiving transducer; providing a phase control voltage for controlling and varying the phase of the ultrasonic frequency signal; and providing a frequency control voltage for selecting a frequency of the ultrasonic frequency signal applied to the transmitting transducer according to a particular resonance peak of the resonator cells. |
