Abstract: A dual vibrating beam force transducer having an electrostatic drive system. The transducer comprises a body having first and second generally parallel beams, coupled together at their ends. First and second electrodes are positioned adjacent to but not in contact with the respective beams. A drive circuit causes an oscillating voltage to be applied to the electrodes. The beams are thus subjected to electrostatic forces that cause the beams to oscillate in a vibration plane containing both beams. The mechanical resonance of the beams controls the oscillation frequency, such that the frequency is a function of a force exerted along the beams. An embodiment is also described in which the drive means is coupled directly to one of the beams.

Abstract: Prior steady-state accelerometers are subject to errors caused by differential thermal expansion between the force transducers and other accelerometer components. This problem is overcome by the present accelerometer that comprises a housing (32), a proof mass (30), a support (34,36) for mounting the proof mass with respect to the housing, and first and second force sensing elements (38,40). The force sensing elements have DC frequency responses, and are connected between the proof mass and the housing such that differential thermal expansion or contraction between the force sensing elements and the proof mass, support and housing results in rotation of the proof mass about a compensation axis (CA) normal to the sensitive axis (SA).

Abstract: A compact, low g range accelerometer comprising a support (22), a proof mass (20), flexures (24, 26) for mounting the proof mass to the support, and a force sensing element (40). The proof mass has a single rotational degree of freedom about a hinge axis (H) perpendicular to the accelerometer's sensitive axis (S). The force sensing element is positioned along a line that is normal to the hinge axis and that lies in a plane that is normal to the hinge axis and that passes through the center of gravity (46) of the proof mass. The perpendicular distance between the hinge axis and the force sensing element is less than the distance between the hinge axis and the center of the proof mass. The force sensing element may be parallel to the pendulous axis, to produce an extremely compact accelerometer, or may be oriented at an acute angle with respect to the pendulous axis, such that the line along which the force sensing element is positioned passes through the center of percussion of the proof mass.

Abstract: A push-pull force transducer comprising a unitary body formed from a crystalline substrate. The body comprises first and second mounting elements for mounting the force transducer to first and second structures, and first and second force sensing elements connected to the mounting elements. Each force sensing element has first and second ends, a line extending from the second to the first end defining a force sensing axis for the force sensing elements. The force sensing elements are oriented with their force sensing axes parallel to and aligned with one another. The first force sensing element has its first end connected to the second mounting element and its second end connected to the first mounting element. The second force sensing element has its first end connected to the first mounting element and its second end connected to the second mounting element. Also described are embodiments utilizing strain relief flexures and an embodiment featuring a leveraged design.

Abstract: An accelerometer comprising a body (10, 16, 12), a proof mass (18, 30, 32), a mounting strucutre comprising flexures (20, 22) for mounting the proof mass to the body, and force sensing elements (34, 38). The flexures permit translational motion of the proof mass with respect to the body along a sensitive axis SA and rotation of the proof mass with respect to the body about a hinge axis HA that is perpendicular to the sensitive axis. Acceleration of the accelerometer along the sensitive axis results in translational motion of the proof mass along the sensitive axis. The force sensing elements reacts to such translational motion by producing a signal indicative of acceleration along the sensitive axis.

Abstract: An accelerometer comprising a support (52) and a proof mass (40) mounted to the support by a flexure (50) or the like, such that the proof mass can rotate about a hinge axis (HA) perpendicular to sensitive axis (SA). An isolator (42) is also mounted to the support by an isolator suspension system (60, 62) that is relatively compliant for isolator movement parallel to a transducer axis (TA) normal to the hinge axis, and relatively noncompliant for isolator rotation about the hinge axis. Force transducers (80, 82) are connected between the isolator and the proof mass. The force transducers are parallel to the transducer axis, and positioned on opposite sides of the hinge axis from one another, such that rotation of the proof mass about the hinge axis puts one force transducer in tension and the other force transducer in compression.

Abstract: Prior vibrating beam accelerometers are subject to errors caused by differential thermal expansion between the vibrating beams and other accelerometer components. This problem is overcome by the present accelerometer that comprises a housing (32), a proof mass (30), a support (34,36) for mounting the proof mass with respect to the housing, and first and second force sensing elements (38,40). The force sensing elements are connected between the proof mass and the housing such that differential thermal expansion or contraction between the force sensing elements and the proof mass, support and housing results in rotation of the proof mass about a compensation axis (CA) normal to the sensitive axis (SA).

Abstract: An accelerometer with improved resistance to errors due to thermal stress. The accelerometer comprises a proof mass assembly (44), a stator (40), and an interface member (90) that includes a plate-like body positioned between the proof mass assembly and the stator. The proof mass assembly includes a reed (72) suspended from a support (70), and a reed capacitor plate positioned on the reed. The body includes a body capacitor plate (94) positioned to form a capacitor with the reed capacitor plate. The interface member includes first mounting member (110) for securely mounting a first area of the stator with respect to a corresponding first area of the support, and a mounting element (126) extending between a second area of the stator and a corresponding second area of the support. The mounting element is relatively compliant along a first axis, and relatively rigid along all other axes. The first axis lies in the plane of the body and passes approximately through the first mounting member.

Abstract: An accelerometer with a pivoting beam to accommodate differential thermal effects. The accelerometer measures acceleration along a sensitive axis, and comprises a housing, a proof mass, support means and a coupling assembly. The support means mounts the proof mass with respect to the housing. The coupling assembly is connected to the proof mass and housing, and comprises a beam and first and second force sensing elements. The beam is mounted for pivotal movement about a compensation axis normal to the sensitive axis. The first and second force sensing elements are connected to the pivot member at spaced-apart connection points on opposite sides of the compensation axis from one another, such that an acceleration along the sensitive axis results in respective compression and tension forces on the force sensing elements, and such that differential thermal expansion results in rotation of the beam about the compensation axis.

Abstract: An accelerometer comprising a proof mass assembly that includes a reed suspended from a support and a cylindrical coil mounted to the reed by a mounting system that minimizes errors due to thermal stress. The mounting system comprises at least three mounting elements. Each mounting element has first and second ends, and a resilient intermediate portion. The first end of each mounting element is connected to the coil, the second end of each mounting element is connected to the reed, and the intermediate portion of each mounting element provides a low resistance to relative movement between the coil and reed in a radial direction, and a high resistance to relative movement between the coil and reed in directions normal to the radial direction. The reed preferably comprises fused quartz, and the mounting system preferably comprises a fused quartz base mounted directly to the reed and connected to the second end of each mounting element.

Abstract: Thermally induced stress between a quartz proof mass and the metal stators which constrain it are relieved by a suspension system employing pliant members. Contact points between the proof mass and the stators are formed by raised pads on the proof mass which contact beams formed in the stators. Each beam has an axis of pliancy, which axis extends through a fixed, stable contact point between the proof mass and the stators, the beam being otherwise rigid to applied forces along axes orthogonal to the axis of pliancy. The resulting suspension system exhibits compliance to thermally induced loads while providing rigidity in response to seismic loads.In alternative embodiments of the suspension system, the pliant beams are positioned to provide temperature compensation for compounds of the transducer.