Method for controlling the sensitivity and linearity of capacitive transducer systems
First Claim
1. A method for controlling nonlinearities in a transducer having a movable member responsive to an input stimulus and in which nonlinearities of a first type degrade performance of the transducer, comprising the step of introducing into the transducer during manufacture thereof a nonlinearity of a second type defined by a stiffness which changes with an input, said nonlinearity being introduced into a constraining member attached to the movable member so as to offset the linearities of the first type and thereby control the overall nonlinearity of the transducer.
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Accused Products
Abstract
Inherent capacitive-type nonlinearities in a capacitive displacement transducer can be eliminated or reduced by the introduction of an oppositely-sensed nonlinearity. The oppositely sensed nonlinearity is introduced by selecting a diaphragm thickness to define a stiffness such that there is an increased resistance to deflection. The increased resistance to deflection generates a nonlinearity which decreases with increasing input to offset an oppositely sensed inherent nonlinearly which increases with increasing input, thereby balancing the nonlinearities and achieving an overall linear output.
30 Citations
38 Claims
- 1. A method for controlling nonlinearities in a transducer having a movable member responsive to an input stimulus and in which nonlinearities of a first type degrade performance of the transducer, comprising the step of introducing into the transducer during manufacture thereof a nonlinearity of a second type defined by a stiffness which changes with an input, said nonlinearity being introduced into a constraining member attached to the movable member so as to offset the linearities of the first type and thereby control the overall nonlinearity of the transducer.
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8. A method for controlling nonlinearities in a transducer having a movable member responsive to an input stimulus, and in which first type nonlinearities degrade performance of the transducer, comprising the steps of:
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attaching said movable member to a fixed frame with a constraining support; and constructing said constraining support with a material having a predefined thickness such that with changes in movement of said movable member said constraining support provides changes in resistance to said movement, said change in resistance defining a second type nonlinearity which offsets said first type nonlinearities to thereby control overall nonlinearities. - View Dependent Claims (9, 10, 11, 12, 13)
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14. A method for controlling nonlinearities in a transducer having a member which is movable in response to an input stimulus, and in which there is an increase in sensitivity with an increase in the input stimulus, comprising the steps of:
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selecting a parameter of said transducer which decreases said sensitivity with increasing input such that an overall nonlinearity can be controlled, and selecting said parameter as a change in resistance of movement of said movable member with a change in input stimulus; and fabricating a transducer having the selected resistance of the movable member to control overall nonlinearity. - View Dependent Claims (15, 16, 17, 18, 19, 28)
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20. A method for constructing a transducer of the type having a member deflectable in response to an input stimulus to produce a change in output capacitance, comprising the steps of:
selecting a gap spacing associated with said capacitance and constructing said movable member such that with increasing member deflection there is increased resistance to deflection so that a sensitivity of said transducer is made substantially independent of said input stimulus. - View Dependent Claims (21, 22)
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23. A method for reducing nonlinearities in a capacitive transducer of the type having an element movable in response to an input stimulus, comprising the steps of:
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selecting a parameter ratio comprising a displacement parameter of the movable member and a thickness parameter of a support structure which supports said movable member; and fabricating the support structure that supports the movable member to conform to said parameter ratio to thereby introduce a nonlinearity into the transducer for controlling the overall nonlinearity of said transducer. - View Dependent Claims (24, 25, 26)
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27. A method for constructing a capacitive displacement transducer, comprising the steps of:
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forming a thin diaphragm; supporting said diaphragm at edges thereof so that said diaphragm is spaced apart from a capacitor plate by a gap to thereby define a capacitance; and selecting the gap spacing and the thickness of the diaphragm to substantially reduce an overall nonlinearity of said transducer. - View Dependent Claims (29)
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30. A method for defining dimensions affecting performance of a capacitive pressure transducer system, said system being of the type having a clamped diaphragm movable in response to a pressure and at least one fixed capacitance plate, comprising the steps of:
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a) for a given set of transducer dimensions and a given input pressure, determining the deflection of a large number of regions of said diaphragm; b) determining the capacitance(s) between said diaphragm and said capacitance plate(s) by summing the capacitance(s) between said diaphragm regions and said capacitance plate(s); c) determining the electrical output of the transducer system based upon a given capacitance-to-electrical output conversion algorithm; d) repeating steps a) through c) for a range of said pressures to determine the sensitivity and nonlinearity of said transducer system; e) repeating steps a) through d) for a range of said transducer dimensions to determine the effect of said transducer dimensions on sensitivity and nonlinearity; and f) selecting transducer dimensions to achieve a desired nonlinearity. - View Dependent Claims (31, 32, 33)
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34. A method for reducing nonlinearity of a capacitive displacement transducer of the type having a movable member which is movable in response to an input physical stimulus, and at least one fixed capacitance plate, comprising the steps of:
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selecting a capacitive gap spacing between said fixed capacitance plate and said movable member to define a nonlinearity having a sense which increases sensitivity with increasing input; selecting a thickness of a support element connected to said movable member to define a nonlinearity having a sense which decreases sensitivity with increasing input; and selecting said capacitive gap and said support element thickness so that the nonlinearity associated with the capacitive gap is substantially offset by the nonlinearity associated with said support element. - View Dependent Claims (35, 36, 37, 38)
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Specification