| 摘要 |
A resonant wire instrument for producing a measurement signal, which is derived from the resonant frequency of a vibratable wire tensioned in accordance with the magnitude of a physical variable being measured, wherein a force impulse produced mechanically by an apparatus is applied to displace laterally one end of the vibratable wire so as to excite the wire into resonant motion. In one embodiment, the one end is rigidly attached to a housing and a piston applies a transverse force impulse to that end by momentarily striking the housing. In another embodiment, the one end is connected to a piezoelectric crystal which responds to a short-duration electric field to displace momentarily that end. In one species of this other embodiment, the crystal is made to oscillate at the resonant frequency of the tensioned wire by the application of an alternating-polarity voltage signal that is generated by a voltage source having an output connected to the crystal, and a feedback circuit coupled to receive the measurement signal operates to produce a control signal that is used for controlling the voltage source so that the voltage signal being applied to the crystal has a frequency which varies in accordance with changes in the resonant frequency of the wire.
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