Sundstrand Data Control, Inc.

Sundstrand Corporation

Alliedsignal Inc.

Other

Brian L Norling

Rex B Peters

James R Woodruff

Mitchell J Novack

Rand H Hulsing, Ii

Graeme A Blake

Richard A Hanson

Peter H LaFond

Jeffrey F Tonn

Craig J Cornelius

John C G Dunfield

Edward A Urbach

A sensor system is formed from a micro machined resonant structure with multiple resonant elements, a tracking resonator control electronics, and signal processing algorithms. The moving elements of the resonator are coated with chemically active materials that change mass when exposed to the target chemical resulting in a change in frequency or period of oscillation. The changes in frequency or period are processed by multi-sensor chemical detection algorithms to identify chemical types and concentrations. In essence, the resonator and drive electronics form a closed loop oscillator operating at the resonator's natural frequency. The resonators are formed from silicon using photolithographic processes. The resonator design includes in-plane resonant motion combined with dynamic balance to operate with a high Q even in the presence of atmospheric pressure.

Resonant micromachined biochemical sensor

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.

Tunnel current sensor with force relief protection

A monolithic micromachined temperature switch obviates the necessity of assembling discrete components and also allows the temperature switch to be disposed in a relatively small package. In one embodiment of the invention, the temperature switch includes a bimetallic element operatively coupled to a pair of electrical contacts. In order to minimize contact wear due to contact arcing, a biasing force such as an electrostatic force is applied to the switch which provides snap action of the electrical contacts in both the opening and closing directions which enables the temperature set point to be adjusted by varying electrostatic force biasing voltage. In an alternate embodiment of the invention, the biasing force for providing the snap action effect can be eliminated by substituting the movable contacts with a field effect transistor with a movably mounted gate terminal. With such an arrangement since little or no current would normally flow through the gate terminal, the need to reduce contact arcing normally resulting from contact bounce would thus be eliminated. Thus, in such an embodiment, a biasing force such as an electrostatic biasing force is not necessary unless a snap action with hysteresis is desired. In alternate embodiments of the invention, the temperature switch may be formed with an integral power transistor for switching relatively large currents. The temperature switch may also be provided with an integrally formed capacitor for reducing the effects of switching inductive loads, such as relays and the like.

Micromachined thermal switch

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.

Servo accelerometer with tunnel current sensor and complementary

A force sensing element is formed with four vibrating beams having substantially the same width and length. The four beams are spaced apart and disposed parallel to one another and are connected at opposite ends by end portions. With such a configuration, the outer beams move in phase with each other but 180.degree. out of phase with the inner beams. As such, the linear and angular reaction forces at the end portions are effectively cancelled. One advantage of such a configuration is its relative insensitivity to manufacturing process variations. By utilizing four beams which are nearly identical in width, variation in fabrication tolerance has virtually an equal effect on beam mass such that the dynamic balance of the force sensing element is maintained to a high degree of accuracy. Various drive methodologies for the force sensing element are disclosed as well as force sensing elements with integrally-formed isolator systems.

Four bar resonating force transducer

A stress isolation technique for an accelerometer of the type that has a reed that includes a paddle, a support, and flexures connecting the paddle to an area of the support. The support includes one or more mounting pads through which the reed is mounted. The area of the support adjacent to the flexures is divided into first and second portions, such that the flexures are connected to the first portion and such that the mounting pads are positioned solely on the second portion. The flexures are therefore isolated from stress coupled into the reed through the mounting pads.

Accelerometer with flexure isolation

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. Projections extend between the arresting element and sensor unit to engage corresponding channels thereby protecting the sensor unit from damage due to cross-axis accelerations.

Acceleration overload protection mechanism for sensor devices

The mounting system of the present invention is adapted to support a precision transducer (14) in spaced alignment with a supporting case (12). The mounting system comprises a plurality of mounting elements (30), each mounting element having one end (34), an opposite end (32) and a resilient intermediate portion (36). One end is adapted to be connected to the transducer, and the opposite end is adapted to be connected to the case. Adjacent mounting elements are joined to one another by bridge sections (38) to form a continuous mounting ring (16) and to define a plurality of gaps (56). At least the end connected to the transducer and bridge sections is composed of a substance that has a coefficient of thermal expansion approximately equal to the coefficient of thermal expansion of the transducer. Each intermediate portion is configured to provide a low resistance to relative movement between the transducer and case in a radial direction, and a high resistance to relative movement in other directions.

Mounting system for an accelerometer

An accelerometer comprising a monolithic crystalline substrate, the substrate comprising a support, a proof mass, and a force transducer. The proof mass is connected to the support by one or more proof mass flexures that permit the proof mass to rotate with respect to the support about a hinge axis. One end of the force transducer is connected to the support, and the other end is connected to the proof mass by a transducer flexure. The transducer flexure has a thickness substantially less than the thickness of the transducer, such that when the proof mass rotates, the transducer rotates with respect to the proof mass about a transducer axis that passes through the transducer flexure. Preferably, the transducer axis is offset from the hinge axis in a manner so as to cancel nonlinearities in the force transducer, and the length of the proof mass along the pendulous axis is less than half the length of the transducer. Damping plates are positioned above and below the proof mass, and provide shock stops and damping.

Monolithic accelerometer with flexurally mounted force transducer

A vibrating crystal transducer for measuring temperature is disclosed. The crystal includes a single elongated vibrating beam that has a torsional mode resonant frequency that is a function of the temperature of the crystal. The torsional moments of the crystal are reverse symmetric with respect to a nodal line on the beam. The beam is contained in a frame that is secured to a sensor frame member. The beam is attached to the frame by a pair of opposed mounting posts that are in line with the nodal line on the beam. The beam, the beam frame (16) and the mounting posts are formed out of an integral section of crystalline material. When the beam is vibrated, the reverse symmetrically opposed torsional moments along the beam cancel each other out and, consequently, no torsional energy is transmitted through the mounting posts to the beam frame or the sensor frame. Since the beam frame does not serve as a recipient for the torsional energy, torsional energy is not lost through the beam frame so that the beam has a relatively high quality factor and torsional vibration of the beam cannot cause the crystal to eventually work loose of the sensor frame at the beam frame.

Crystal temperature transducer

A fiber optic transducer utilizes a single optical fiber having one end surface, disposed adjacent a sensor element, cut at an angle to result in frustrated total internal reflection. The end surface of the optical fiber is spaced away from the sensor element. As the sensor element is displaced with respect to the end surface of the optical fiber, the amount of light reflected from the sensor element varies. Light injected into the optical fiber is reflected back toward the light source until the element comes into relatively close proximity with the angled end of the optical fiber. When this occurs, a portion of the light is transmitted across the gap and absorbed by the sensor element. The ratio of the light reflected from the reflective surface to the total light input into the optical fiber produces a signal representative of the displacement of the sensor element. This signal can then be converted to a corresponding temperature or pressure signal and displayed at a remote location. The transducer is capable of being used with temperature or pressure sensitive elements to provide either an analog output signal or a digital output signal. Also disclosed is a self test circuit for the transducer.

Fiber optic thermal switch utilizing frustrated total internal

A transducer having compensation for a deflection due to an applied stress. The transducer a support ring (32) having a proof mass (34) cantilevered on a pair of flexures (38) between the magnets (26, 28) of a stator in which the transducer is mounted. Deflection of the support ring due to an imbalanced applied force is compensated by either moving the pads (30) used to mount the support ring, moving the centroid of capacitance (128) of the proof mass, or by modifying the support ring to provide a pair of moment arms (156), each approach insuring that an axis of deflection (102, 130) of the support ring is coaligned with the centroid of capacitance, thereby minimizing a bias error in the transducer output.

Stress compensated transducer

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.

Accelerometer with coplanar push-pull force transducers

An improved accelerometer of the type that includes a proof mass suspended from a support by one or more flexures, such that the proof mass can pivot with respect to the support about a hinge axis. The proof mass includes a paddle attached to the flexures, the paddle having first and second paddle surfaces. The coil is mounted on the first paddle surface, and the accelerometer includes a stator for mounting the support and for forming a magnetic circuit with the coil. The improvement comprises positioning the flexures such that a plane containing the hinge axis and the center of mass of the proof mass is parallel to one of the paddle surfaces, and closer to one paddle surface than to the other paddle surface. In a preferred arrangement, the plane containing the hinge axis and the center of mass is approximately coplanar with one of the paddle surfaces and with the flexures.

Asymmetric flexure for pendulous accelerometer

A transducer having compensation for a deflection due to an applied stress. The transducer includes a support ring (32) having a proof mass (34) cantilevered on a pair of flexures (38) between the magnets (26, 28) of a stator in which the transducer is mounted. Deflection of the support ring due to an imbalanced applied force is compensated by either moving the pads (30) used to mount the support ring, moving the centroid of capacitance (42) of the proof mass, or by modifying the support ring to provide a pair of moment arms (152), each approach insuring that an axis of deflection (102, 130) of the support ring is coaligned with the centroid of capacitance, thereby minimizing a bias error in the transducer output.

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Mill Creek, WA, United States of America

Brian L Norling