Vibrating beam pressure sensor
First Claim
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1. A pressure sensor providing an output signal that is proportional to the natural frequency of a vibrating beam having a longitudinal axis, comprising;
- a base;
means to mount one end of said beam with respect to said base;
an actuator;
a first end of said actuator being operably coupled to an opposite end of said beam from the attachment of said beam to said base;
means to apply a pressure signal to said actuator to cause said actuator to change the force exerted on said beam by said actuator in direction along the longitudinal axis of said beam;
drive means having a longitudinal axis substantially normal to the longitudinal axis of the beam to provide a driving signal to oscillate said beam at its natural frequency;
and pick-off means to sense the frequency of oscillation of said beam, said drive means and pick-off means being fixed relative to each other and coupled as a unit to said base on the same side of the beam.
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Abstract
A sensor providing an output indicating pressure including means to excite a vibrating beam at its natural frequency, and means to load the beam in response to pressure to alter the natural frequency of the beam. The frequency output is sensed by a capacitor pick off mounted on the same side of the beam as the means to excite the beam. Changes in the output frequency provides an indication of the pressure being measured.
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Citations
18 Claims
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1. A pressure sensor providing an output signal that is proportional to the natural frequency of a vibrating beam having a longitudinal axis, comprising;
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a base; means to mount one end of said beam with respect to said base; an actuator; a first end of said actuator being operably coupled to an opposite end of said beam from the attachment of said beam to said base; means to apply a pressure signal to said actuator to cause said actuator to change the force exerted on said beam by said actuator in direction along the longitudinal axis of said beam; drive means having a longitudinal axis substantially normal to the longitudinal axis of the beam to provide a driving signal to oscillate said beam at its natural frequency; and pick-off means to sense the frequency of oscillation of said beam, said drive means and pick-off means being fixed relative to each other and coupled as a unit to said base on the same side of the beam. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A pressure transducer of the vibrating member type wherein said vibrating member is oscillated at a frequency dependent upon the stress in the vibrating member and the frequency of oscillation is sensed as a measurement of pressure having:
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a base; an elongated vibrating member having first and second ends; means to mount said vibrating member relative to said base at one end thereof; first means sensitive to a pressure signal coupled to the vibrating member to change the stress in said vibrating member as a function of the pressure signal; electromagnetic driver means for controlling oscillation of said vibrating member responsive to the pressure signal thereon; and second means to sense the oscillation of the vibrating member comprising a block of electrically nonconductive material disposed on the base and having a capacitor plate deposited thereon and positioned adjacent the vibrating member, said vibrating member having a flat surface facing said capacitor plate which, responsive to the pressure signal, moves toward and away from the capacitor plate during oscillation. - View Dependent Claims (10, 11, 12, 13, 14)
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15. A sensor providing an output signal that is proportional to the natural frequency of an elongated vibrating beam comprising a base;
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means to mount one end of said beam with respect to said base; an actuator mounted on said base and having a first end connected to an opposite end of said beam from the attachement of said beam to said base; means to apply load to said actuator to cause changes in the stress in said beam in direction along the longitudinal axis of said beam; a coil and pick-off sensor assembly mounted on said base, said pick-off sensor comprising a capacitor plate adjacent one side of said beam and said coil being on an opposite side of said capacitor plate from said beam; means connecting said coil in an energization circuit to provide oscillating flux to vibrate said beam and means connecting said capacitor in said circuit to control oscillation of said flux in response to capacitance changes between said beam and capacitor plate.
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16. In a pressure transducer of the vibrating beam type having a base, means to drive a vibrating beam to oscillate at its natural frequency, which varies as a function of the stress in the vibrating beam, means to sense the frequency of oscillation of the beam as a measurement of pressure and having means responsive to pressure to be sensed to exert a tension on the beam as a function of pressure, the improvement comprising:
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a vibrating beam comprising a center beam section having a natural frequency which changes with stress in the center beam section; means to mount a first end of said center beam section relative to the base; means to mount a second end of said center beam section to the means responsive to pressure whereby the tension in said center beam section changes from a first stress condition when the pressure to be measured is at a minimum to a fully stressed condition when the pressure to be sensed is at a maximum; said means to mount the first and second ends of said center beam section comprising first and second spring assemblies forming isolators, respectively; one end of the first isolator being connected to the first end of said center beam section and the other end of the first isolator being connected to the base; one end of said second isolator being connected to the second end of said center beam section and the other end of the second isolator being connected to the means responsive to pressure; said spring assemblies comprising the isolators each having a fundamental natural frequency greater than the natural frequency of the center section when the center beam section is fully stressed, and lower than twice the natural frequency of the center beam section when the center beam section is at its first stress condition. - View Dependent Claims (17, 18)
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Specification