抄録
A novel electromechanical pressure transducer is proposed. Essentially, as shown in Fig. 1, it operates using the acoustical resonance due to the stiffness of a fluid in cavities and the mass of a vibrating body. This transducer is suited for application to telemetering systems because: (1) The absolute pressure, not the pressure difference, is transformed into an electrical signal. No parts of the transducer support any difference of static pressure. Therefore, error due to creep is avoidable. (2) The output signal is the frequency, not the amplitude. Pressure is transformed directly into a high-power ac signal by a simple electrical circuit. This paper includes the operation analysis of this transducer, an experimental check of its operation and the trial construction of a rather practical model. The input-output relation of this transducer, shown in Fig. 2, is given by Eq. (8) where k_V_0 is the stiffness of the cavity at pressure P=P_0. The symbols k_e and k_<ee> are the elastic support stiffness related to two respective deformation modes shown in Fig. 3. When the condition given by Eq. (10) or (12) occurs, Eq. (8) is reduced to the approximate Eq. (11) or (13). A novel electromechanical transducer having no biasing magnet is utilized in the first experimental model shown in Fig. 6. There are no large attractive forces and no fragile voice coils. Fig. 8 shows the oscillatory circuit using the first model. The input-output relation of this circuit is shown in Fig. 10, which satisfies Eq. (11). A rather practical small model was constructed using two elastic support thicknesses, 15μm and 6μm. The input-output relation of this model is shown in Fig. 12, which fits Eq. (13), because the smaller support size causes greater stiffnesses k_e and k_<ee>. The dependence of the output period of this model on temperature is shown in Fig. 13. This effect can be compensated for, just as with conventional strain-gauge type pressure transducers.
