| 摘要 |
A sensor for an electrostatic detector comprising an elongated vibratory element supported at a mechanical node at one end in the manner of a cantilever beam, a sensitive electrode on the vibratory element near the other end and adapted to be disposed toward an electrical charge, field or potential being measured, and a driver transducer on the vibratory element for vibrating the element in a direction to vary the capacitive coupling between the electrode and the electrical charge, field or potential being measured. The driver transducer is at a location along the beam and is operated at a vibratory frequency such that a virtual mechanical node appears along the beam. This, in turn, reduces vibration at the mechanical attachment node so that the degree of stiffness of the mechanical node does not affect the operating frequency and/or the displacement at the free end of the cantilever. The variation of the vibration amplitude of the beam and thus the detector's motion amplitude at the end of the beam is made independent of both the mass of the sensor/probe and/or the mass of the structure, such as a clamping/holding fixturing, used to place the sensor/probe into its measuring position relative to the surface or area under test. The electrical performance is thus stabilized and is made independent of the particular clamping/holding structure used. An amplifier on the vibratory element has an input connected to the sensitive electrode and an output adapted for connection to a readout/measuring device such as an electrostatic voltmeter. Preferably, the vibratory frequency corresponds to the second vibrational node of the beam and the driver transducer is located on the beam in overlapping relation to the peak of the beam vibration near the middle thereof.
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