Capacitive digital integrated circuit pressure transducer
First Claim
1. A pressure transducer comprising, in combination:
- a semiconductor base;
first and second capacitors each with first and second conductive plates and with each said first conductive plate integrally formed on said semiconductor base;
said first capacitor at least partially formed on a deformable wall unitary with said semconductor base;
means to apply to said deformable wall a force or a pressure for measurement thereof by change of the distance and capacitance between said first and second plates of said first capacitor;
an Eccles-Jordan astable multivibrator including said first and second capacitors; and
an integrated circuit unitarily on said semiconductor base and including at least said multivibrator and said first and second capacitors.
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Accused Products
Abstract
A highly accurate and miniaturized pressure transducer is disclosed which includes first and second capacitors as a part of the integrated circuit, which also includes an Eccles-Jordan astable multivibrator. The miniaturization of both the capacitors and the entire multivibrator circuit in an integrated circuit establishes all components so that they are very closely matched on the two halves of the multivibrator, and so that whatever environmental disturbances, e.g., electrical, thermal, noise, etc., are encountered, are shared by both halves, and hence negated, so far as output drift is concerned. The multivibrator has a rectangular wave output and the duty cycle thereof is proportional to the force or pressure applied. This duty cycle is changed upon applied pressure, which changes one of the capacitors, and measurement of the duty cycle is a measurement of the applied force or pressure. The entire output circuit of the transducer is a digital output to provide digital processing through to a digital display. The foregoing abstract is merely a resume of one general application, is not a complete discussion of all principles of operation or applications, and is not to be construed as a limitation on the scope of the claimed subject matter.
44 Citations
20 Claims
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1. A pressure transducer comprising, in combination:
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a semiconductor base; first and second capacitors each with first and second conductive plates and with each said first conductive plate integrally formed on said semiconductor base; said first capacitor at least partially formed on a deformable wall unitary with said semconductor base; means to apply to said deformable wall a force or a pressure for measurement thereof by change of the distance and capacitance between said first and second plates of said first capacitor; an Eccles-Jordan astable multivibrator including said first and second capacitors; and an integrated circuit unitarily on said semiconductor base and including at least said multivibrator and said first and second capacitors. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A pressure transducer comprising, in combination:
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an Eccles-Jordan astable multivibrator including first and second capacitors; means to change the capacitance of one of the two capacitors in accordance with a change of pressure input; said multivibrator having a substantially rectangular wave output with a varying duty cycle of ON and OFF times in accordance with the capacitance change; high frequency means to establish plural high frequency pulses according to each of said ON and OFF times; counting means to count and determine the difference between the pulses in the ON and OFF times; and offset means to compensate for any initial departure of the duty cycle from fifty percent with no applied pressure or force. - View Dependent Claims (17, 18, 19, 20)
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Specification