US3841150A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Strain gauge transducer signal conditioning circuitry
Assignee: Honeywell Inc
•
Filing: 1973-11-02
•
Granted: 1974-10-15
•
Expires: 1993-11-02
Abstract
Abstract The disclosure describes circuitry for obtaining a pressure measurement from two strain gauge resistors mounted on a diaphragm which moves in response to changes in pressure. Operational amplifiers produce constant current flow through the resistors. A difference amplifier produces a measurement voltage corresponding to the difference in voltage across the resistors due to pressure variations. A unique positive feedback circuit is used in connection with the operational amplifiers to linearize the measurement voltage with respect to pressure changes. Temperature correction circuitry is used to maintain a constant measurement voltage scale over a wide range of temperature.
Inventors
- 👤 R Pearson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-22 19:39
CPC Classifications
G; G01; G01L; G01L1/00; G01L1/20; G01L1/22; G01L1/2268; G01L9/00; G01L9/0041; G01L9/0051; G01L9/0052; G01L9/0054; G01L9/02; G01L9/06; G01L9/065
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
246 words
In a strain gauge comprising a first resistor and a second resistor carried by a substrate so that a variable strain is applied to the resistors in response to changes in the environment, improved apparatus for determining the changes in the environment by measuring the variations in an electrical property of the resistors comprising in combination: a first operational amplifier conprising a first noninverting input, a first inverting input and a first output; a second operational amplifier comprising a second non-inverting input, a second inverting input and a second output; circuit means for connecting the first and second non-inverting inputs to a current sink having a predetermined voltage; first means for connecting the first resistor between the first output and the first inverting input so that the current flowing through the first resistor remains constant in spite of changes in the resistance of the first resistor; second means for connecting the second resistor between the second output and the second inverting input so that the current flowing through the second resistor remains constant in spite of changes in the resistance of the second resistor; a voltage source; biasing means connected between the voltage source and the first and second inverting inputs for adjusting the quiescent current flowing through the first and second resistors; and differential means having inputs operatively connected to the first and second resistors and an output for producing a measurement voltage proportional to the difference in voltage across the first and second resistors.
Claim 2
Dependent Claim
246 words
In a strain gauge comprising a first resistor and a second resistor carried by a substrate so that a variable strain is applied to the resistors in response to changes in the environment, improved apparatus for determining the changes in the environment by measuring the variations in an electrical property of the resistors comprising in combination: a first operational amplifier conprising a first noninverting input, a first inverting input and a first output; a second operational amplifier comprising a second non-inverting input, a second inverting input and a second output; circuit means for connecting the first and second non-inverting inputs to a current sink having a predetermined voltage; first means for connecting the first resistor between the first output and the first inverting input so that the current flowing through the first resistor remains constant in spite of changes in the resistance of the first resistor; second means for connecting the second resistor between the second output and the second inverting input so that the current flowing through the second resistor remains constant in spite of changes in the resistance of the second resistor; a voltage source; biasing means connected between the voltage source and the first and second inverting inputs for adjusting the quiescent current flowing through the first and second resistors; and differential means having inputs operatively connected to the first and second resistors and an output for producing a measurement voltage proportional to the difference in voltage across the first and second resistors.
Claim 3
Dependent Claim
36 words
Apparatus, as claimed in claim 1, wherein the circuit means comprises a resistance network having A resistance value such that the first and second inverting inputs are maintained at a potential of less than one volt.
Claim 4
Dependent Claim
24 words
Apparatus, as claimed in claim 1, wherein each of the first and second operational amplifiers has an input impedance of greater than 250,000 ohms.
Claim 5
Dependent Claim
24 words
Apparatus, as claimed in claim 1, wherein each of the first and second operational amplifiers has an output impedance of less than 100 ohms.
Claim 6
Dependent Claim
33 words
Apparatus, as claimed in claim 1, and further comprising means for feeding back a portion of the measurement voltage to the circuit means, whereby the pressure linearity of the measurement voltage is improved.
Claim 7
Dependent Claim
147 words
Apparatus, as claimed in claim 5, and further comprising temperature compensating means comprising: temperature sensing means for producing a voltage proportional to the temperature of the substrate; first correction means for generating a first correction signal having a magnitude proportional to the change of the measurement voltage span over a first temperature range; second correction means for generating a second correction signal having a magnitude proportional to the change of the measurement voltage span over a second temperature range greater than the first temperature range; and switching means for transmitting to the biasing means a first temperature correction biasing voltage proportional to the first correction signal when the temperature of the substrate is in the first range and for transmitting to the biasing means a second temperature correction biasing voltage proportional to the second correction signal when the temperature of the substrate is in the second range.
Claim 8
Dependent Claim
34 words
Apparatus, as claimed in claim 6, wherein the first temperature range and the second temperature range lie below and above a minimum span temperature respectively at which the measurement voltage span is a minimum.
Claim 9
Dependent Claim
15 words
Apparatus, as claimed in claim 7, wherein the first correction means comprises an operational amplifier.
Claim 10
Dependent Claim
22 words
Apparatus, as claimed in claim 8, wherein the switching means comprises a diode network connected to the first and second correction means.
References Cited (Backward Citations)
US3572109A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-10-14 | 1978-04-15 | 1978-10-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-10-14 | 1982-04-15 | 1982-10-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-10-14 | 1986-04-15 | 1986-10-15 | $7700.00 | Window Closed / Lapsed |