Abstract: A vibratory transducer (22) for an accelerometer (2) having a pair of parallel beams (50, 52) with first and second fixed end portions, and a pair of electrodes (62, 64) positioned adjacent to the beams for generating an electrostatic force to transversely vibrate the beams at a resonant frequency. The vibration frequency of the beam is generally related to axial (i.e., compression or tension) forces applied to either one of the fixed ends of the beam so that the magnitude of the force applied can be measured by changes in the vibration frequency. The electrodes and the beams each have a plurality of fingers (82, 80) extending laterally outward so that the beam fingers and the electrode fingers are intermeshed with each other. The intermeshed fingers reduce the transducer's sensitivity to changes in applied voltage, thereby increasing the accuracy of the frequency signal.

Abstract: A pendulous accelerometer wherein the active reaction mass is pendulously mounted external to a fixed support structure and may include sensor cover of covers in the total active reaction mass.

Abstract: A pendulous accelerometer wherein the active reaction mass is pendulously mounted external to a fixed support structure and may include sensor cover or covers in the total active reaction mass.

Abstract: A mechanical resonator having interconnected vibrating beams and counter balances whereby transfer of energy from the vibrating beams is essentially eliminated.

Abstract: An accelerometer formed from a semiconducting substrate and first and second active layers coupled to the opposite surfaces of the substrate. The substrate has a frame and a proof mass suspended from the frame by one or more flexures for rotation about an input axis in response to an applied force. The active layers each include a vibratory force transducer mechanically coupled to the proof mass for detecting a force applied to the proof mass. With this configuration, the transducers are located on either side of the substrate, which improves the differential design symmetry of the force detecting apparatus. This reduces the common mode non-linear response characteristics of the accelerometer, particularly in high dynamics applications, where high performance is required.

Abstract: The method of the present invention includes forming a frame and a proof mass suspended from the frame by one or more flexures, and including within a thin active layer one or more vibratory force transducers suitably coupled to the proof mass for detecting a force applied to the proof mass. According to the present invention, an insulating layer, such as silicon oxide, is formed between the substrate and the active layer to insulate the active layer from the substrate. Providing a separate insulating layer between the substrate and active layer improves the electrical insulation between the proof mass and the transducers, which allows for effective operation over a wide range of temperatures.

Abstract: An accelerometer formed from a semiconducting substrate and first and second active layers coupled to the opposite surfaces of the substrate. The substrate has a frame and a proof mass suspended from the frame by one or more flexures for rotation about an input axis in response to an applied force. The active layers each include a vibratory force transducer mechanically coupled to the proof mass for detecting a force applied to the proof mass. With this configuration, the transducers are located on either side of the substrate, which improves the differential design symmetry of the force detecting apparatus. This reduces the common mode non-linear response characteristics of the accelerometer, particularly in high dynamics applications, where high performance is required.

Abstract: The apparatus of the present invention includes a substrate and a thin active layer each comprising a semiconducting material. The substrate has a frame and a proof mass suspended from the frame by one or more flexures, and the active layer includes one or more vibratory force transducers suitable coupled to the proof mass for detecting a force applied to the proof mass. According to the present invention, an insulating layer, such as silicon oxide, is formed between the substrate and the active layer to insulate the active layer from the substrate. Providing a separate insulating layer between the substrate and active layer improves the electrical insulation between the proof mass and the transducers, which allows for effective operation over a wide range of temperatures.

Abstract: Accelerometers and methods of forming accelerometers are described. The accelerometers are provided with electrically conductive structure configured for connection with external circuitry. The electrically conductive structure has a folded-back architecture which reduces temperature-induced anomalies which can adversely impact acceleration-sensing function of the accelerometer.

Abstract: A tunnel current position sensor has a first sensing electrode coupled to a compliant beam for providing force relief to the sensor. The beam is connected in fixed relationship with a first object. A second sensing electrode is coupled to a second object. The compliant beam elastically deforms to prevent damage resulting from crashing of the electrodes.

Abstract: An electromagnetically-excited silicon micromachined vibrating beam accelerometer includes a proof mass or pendulum attached to an outer casing by way of a pair of flexures defining a hinge axis HA. A double-ended tuning fork (DETF) is connected between the proof mass and the casing along an axis generally perpendicular to the hinge axis (HA) defining a sensitive axis SA such that forces applied along the hinge axis HA will cause the DETF to go into either compression or tension. Electromagnetic excitation causes the vibrating beams to vibrate at a resonant frequency when the proof mass is at rest. In response to a force along the sensitive axis SA, the vibrating beams go into either tension or compression resulting in a change in the resonant frequency which, in turn, is used as a measure of the force. The excitation includes a magnetic field B, applied in a direction generally perpendicular to the plane of the DETF and perpendicular to the sensitive axis SA.

Abstract: A reactionless single beam vibrating force transducer utilizes counterbalances at opposite ends of the beam that rotate in directions opposite to the ends of the vibrating beam to reduce rotational and normal forces transmitted to the end supports for the beam. The proportions of the counterbalances relative to the size of the beam may be chosen to reduce forces in a direction normal to the beam to zero at the expense of some rotational moments at the end of the beam support, or to reduce moments at the expense of some normal force. The relative amounts of residual rotational moments and normal force can be adjusted to suit particular applications. Flexures may also be utilized to reduce the rotational moments transferred to the beam support even further.

Abstract: A method for selectively etching a semiconductor wafer in the presence of an electrochemical etchant wherein the electrical potential of the area that is selectively etched is automatically changed to a potential at which the etching is inhibited once the desired etching in the area is completed. The method is described with respect to making an electrode tip for a tunnel current sensing device.

Abstract: A servo accelerometer uses a tunnel current sensor having a first sensing electrode coupled in fixed alignment with a frame and a second sensing electrode coupled to a proof mass. A position sensing circuit develops a sensing signal indicative of displacement of the proof mass. A feedback circuit provides an output signal and provides a feedback signal to electrostatic drive electrodes for applying an electrostatic repositioning force to the proof mass. The proof mass and frame are connected by a highly compliant suspension structure.

Abstract: A servo accelerometer permits compliant suspension with a pair of flexures by using a plurality of tunnel current position sensors each respectively associated with a corresponding pair of electrostatic drive electrodes. The tunnel current position sensors and the electrostatic drive electrodes are positioned to control undesired movement of the proof mass about a first axis which is normal to the input axis of the accelerometer. In another embodiment, three tunnel current sensors and three pairs of drive electrodes are used to control movement of the proof mass about the first axis and a second axis.

Abstract: A vibrating beam force transducer is comprised of an oscillating sensing element having a frequency output indicative of the force applied to the sensing element. The sensing element has a variable electrical resistance which can vary in accordance with temperature fluctuations over the operating range of the transducer.A drive circuit is electrically coupled to the sensing element for causing the sensing element to oscillate at a resonant frequency that is a function of the force applied to the sensing element. The drive circuit includes a source of DC voltage, which is utilized for altering the electrical characteristics of the drive circuit in response to variations in the electrical resistance of the sensing element.

Abstract: An acceleration overload protection mechanism for use with a sensor unit. The sensor unit is generally defined by a sensor element or elements (i.e., proof mass, flexures, etc.) that are movable in relation to a sensor frame. The overload protection mechanism includes at least one arresting plate. The arresting plate includes a plate frame and an arresting element that are elastically coupled to one another to permit relative movement therebetween. The plate frame of the overload protection mechanism is placed in fixed alignment with the sensor frame to place the arresting element in spaced relation with the sensor element of the sensor unit. The arresting element and sensor element may move relative to one another to allow the arresting element to move to a position proximate the sensor element to limit the range of motion of the sensor element when the sensor unit is subject to an acceleration overload.

Abstract: A method for post-production reduction of scale factor nonlinearities including testing of an assembled torque coil and magnetic circuit to determine nonlinearities. To reduce the scale factor nonlinearities, the position of a magnetic circuit component which intercepts the magnetic flux passing through a torque coil is changed. The position of the interior surface of a magnetic end cap is changed with respect to the position of the torque coil. The location of the interior surface of the end cap is varied by using an end cap having a plug portion which is selected to have an interior surface at a location which minimizes scale factor nonlinearities.An force-balance accelerometer has an improved magnetic circuit for reducing nonlinear scale factors. The magnetic circuit which provides a return path for magnetic flux from a permanent magnet source includes an end cap having an interior surface which is located at an optimum distance from the torque coil of the accelerometer to minimize scale factor distortion.

Abstract: A push-pull accelerometer in which both force transducers lie in a common plane. Thus, when implemented in silicon micromachined device, both transducers can be fabricated from a single crystal layer, thereby producing transducers with closely matched common mode responses.

Abstract: Flexures, and a method for creating flexures, for use in micromechanical sensors such as accelerometers in which a first member is pivotally connected to a second member. In one aspect, the invention provides first and second flexures connecting the first and second members, the flexures permitting rotation about a common hinge axis. The flexures have a crossed configuration that provides increased stability. Each flexure is made by etching grooves in the opposite wafer surface, the positions and depths of the grooves being selected so as to form a flexure therebetween.