Abstract: A transducer comprising at least one planar capacitor with a thin coverlayer of material selected to maximize electric field coupling between cooperating capacitor electrodes within a region external to a principal surface of the coverlayer. Preferred coverlayer materials have low values of moisture absorption, surface free energy, permittivity, dielectric dissipation, and electrical conductance. According to one embodiment of the invention, a driven shield further enhances electric field coupling over and in a region external to the principal surface. The transducer also can promote a physical change in specific adsorbates and materials and simultaneously detect and measure an effect of the induced change. Applications for the transducer of the invention include the measurement of the moisture content of grain and bulk stored commodities, humidity, a dew point temperature, the onset of condensation and rates of adsorption and desorption.

Abstract: A micro-opto-electro-mechanical transducer in which an optical element is angularly positioned by electrical field coupling. Movable electrodes of two orthogonally disposed, differential variable capacitors are coupled to the optical element constrained by structural means to angular displacement around two free-axes of rotation. Cooperating stationary capacitor electrodes with surface contoured regions facing the movable electrodes are affixed to the structural means. A thin dielectric layer of high permittivity material provides a region of fixed spacing between the capacitor electrodes. The surface contoured regions constrain the approach of the movable electrodes with angular displacement of the optical element. Both the open-loop gain and the equilibrium voltage-angle response of the transducer is largely independent of displacement. Electrostatic force feedback maintains the optical element at voltage programmed positions of static equilibrium over a wide angular range of tip and tilt.

Abstract: A transducer with at least one variable-area capacitor comprising a flexible electrode with a surface facing a surface of a cooperating rigid electrode and an electret affixed to a portion of one of said surfaces, wherein said surface of said rigid electrode has a contoured region selected to increase a region of substantially fixed capacitance spacing as said flexible electrode deflects in response to an applied stress.

Abstract: A transducer comprising at least one planar capacitor with a thin coverlayer of material selected to maximize electric field coupling between cooperating capacitor electrodes within a region external to a principal surface of the coverlayer. Preferred coverlayer materials have low values of moisture absorption, surface free energy, permittivity, dielectric dissipation, and electrical conductance. According to one embodiment of the invention, a driven shield further enhances electric field coupling over and in a region external to the principal surface. The transducer also can promote a physical change in specific adsorbates and materials and simultaneously detect and measure an effect of the induced change. Applications for the transducer of the invention include the measurement of the moisture content of grain and bulk stored commodities, humidity, a dew point temperature, the onset of condensation and rates of adsorption and desorption.

Abstract: A method to construct a capacitive transducers comprising the steps of forming over and in a planar surface of a substrate at least one rigid electrode of a variable-area capacitor electrically connected to a location on said substrate reserved for electrode attachment; providing a cooperating flexible electrode with a dielectric layer; and bonding said flexible electrode to said substrate in a surface region surrounding said rigid electrode.

Abstract: A method to maintain a movable electrode of a variable capacitor in fixed relationship with a stationary electrode by electrostatic force feedback when one capacitor electrode is grounded. The invention exploits the high quiescent capacitance and capacitance-load sensitivity of a variable-area capacitance transducer in combination with the advantage of controlling the flexible electrode with a low voltage compared to transducers with parallel-plate capacitors. The invention can be used to accurately control the position of a surface, stylus, inertial mass, valve, electrical contact, electrical component; or an optical component such as a mirror, lens, grating, filter, or holographic element.

Abstract: A differential transconductance amplifier detects changes of the variable capacitor in a low-impedance, bridge circuit and feeds back current to balance the bridge. The voltage that controls the feedback current is proportional to capacitance over a wide dynamic range.

Abstract: An electret transducer with at least one variable area capacitor and a step to provide a contoured region of a rigid capacitor electrode of said variable area capacitor.

Abstract: A micro-opto-electro-mechanical transducer in which an optical element is angularly positioned by electrical field coupling. Movable electrodes of two orthogonally disposed, differential variable capacitors are coupled to the optical element constrained by structural means to angular displacement around two free-axes of rotation. Cooperating stationary capacitor electrodes with surface contoured regions facing the movable electrodes are affixed to the structural means. A thin dielectric layer of high permittivity material provides a region of fixed spacing between the capacitor electrodes. The surface contoured regions constrain the approach of the movable electrodes with angular displacement of the optical element. Both the open-loop gain and the equilibrium voltage-angle response of the transducer is largely independent of displacement. Electrostatic force feedback maintains the optical element at voltage programmed positions of static equilibrium over a wide angular range of tip and tilt.

Abstract: A method to maintain a movable electrode of a variable capacitor in fixed relationship with a stationary electrode by electrostatic force feedback when one capacitor electrode is grounded. The invention exploits the high quiescent capacitance and capacitance-load sensitivity of a variable-area capacitance transducer in combination with the advantage of controlling the flexible electrode with a low voltage compared to transducers with parallel-plate capacitors. The invention can be used to accurately control the position of a surface, stylus, inertial mass, valve, electrical contact, electrical component; or an optical component such as a mirror, lens, grating, filter, or holographic element.

Abstract: A method to construct a capacitive transducer comprising the steps of forming over and in a planar surface of a substrate at least one rigid electrode of a variable-area capacitor electrically connected to a location on said substrate reserved for electrode attachment; providing a cooperating flexible electrode with a dielectric layer; and bonding said flexible electrode to said substrate in a surface region surrounding said rigid electrode.

Abstract: A capacitance measurement circuit detects a change in capacitance between a variable capacitor and a fixed reference capacitor in a bridge network and provides feedback current to null-balance the bridge. An error signal is amplified at high gain by a differential integrator having an output that is converted to a high-frequency stream of digital pulses of constant amplitude and width. The pulse stream is integrated to provide a voltage to control feedback current used to balance the bridge. The average pulse density per unit time, or the frequency of the digital pulses, is linearly proportional to a change in capacitance of said variable capacitor to high accuracy over a wide dynamic range.

Abstract: A capacitive measurement circuit detects a change in capacitance between a variable capacitor and a fixed reference capacitor in a bridge network and provides feedback current to null-balance the bridge. Voltage that controls the feedback current is substantially linearly proportional to changes in capacitance over a wide range.

Abstract: A variable area capacitor with a flexible electrode responsive to a physical effect and a rigid electrode with a predetermined surface contour. The surface contour is dimensioned to provide a specific change in capacitance with deflection of the flexible electrode. A thin dielectric layer maintains a substantially fixed spacing between the two electrodes. Preferred embodiments include a pressure sensor, microphone and accelerometer. A differential transconductance amplifier detects changes of the variable capacitor in a low-impedance, bridge-like circuit and feeds back current to balance the bridge. The voltage that controls the feedback current is proportional to capacitance over a wide dynamic range.