US3617878A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Ac to de high-accuracy low-level voltage measuring system
Assignee: BLH Electronics Inc
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Filing: 1969-04-21
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Granted: 1971-11-02
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Expires: 1989-04-21
Abstract
Abstract An AC to DC system is provided for measuring with high accuracy the low-level output voltage signals from an AC-excited Wheatstone-bridge-type circuit arrangement including electrical strain-responsive elements in its arms. In such a circuit arrangement, output voltages from the initially balanced bridge will be caused by a change in impedance of the strain-responsive elements due to external influences which are to be measured. The output signals from the bridge circuit arrangement are operationally amplified, demodulated to DC, and then read by a digital indicator, such as a digital voltmeter, to give an indication proportional to the to-be-measured influences upon the electrical strain responsive elements. A second demodulator may be used to compensate for system lead resistance and any demodulator inaccuracy, by using the output thereof to control the AC excitation applied to the bridge circuit arrangement input. The second demodulator output may also be directly applied as a reference input for a ratiometer-type digital indication. In one particular application, the strain-responsive elements are mounted as part of a load cell or transducer, and, when loads are applied to the same, the system output indications will be accurately related to the applied load.
Inventors
- 👤 Donald A Senour
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 07:12
CPC Classifications
G; G01; G01G; G01G3/00; G01G3/12; G01G3/14; G01G3/142; G01G3/147
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
217 words
A load-measuring system for displaying with high-accuracy measurements related to low-level output voltages of a straingage transducer bridge-circuit arrangement including at least one strain gage in one of the arms thereof, comprising regulatedoscillator means for applying an AC voltage to a given pair of joining arm points of said bridge-circuit arrangement; means operationally amplifying outputs from said bridge-circuit arrangement appearing at the other pair of joining arm points of said bridge-circuit arrangements, said outputs being caused by unbalance of said bridge-circuit arrangement due to a loadinginduced change in impedance in said strain gage, said operationally amplifying means including a high-gain operational amplifier having feedback means preserving gain which is essentially independent of external influences, highly linear phase-sensitive demodulation means, means isolating the output of said operational amplifier from DC and coupling the isolated output of said operational amplifier to the input of said demodulation means, said demodulation means being responsive to the isolated outputs of said operationally amplifying means and converting the isolated outputs of said operationally amplifying means into DC voltages representative thereof; means filtering the DC output voltages of said demodulation means; and digital indicator means responsive to the filtered DC output voltages of said filtering means and characterizing the same to indicate loading of said transducer with high stability, speed of response, and accuracy.
Claim 2
Dependent Claim
217 words
A load-measuring system for displaying with high-accuracy measurements related to low-level output voltages of a straingage transducer bridge-circuit arrangement including at least one strain gage in one of the arms thereof, comprising regulatedoscillator means for applying an AC voltage to a given pair of joining arm points of said bridge-circuit arrangement; means operationally amplifying outputs from said bridge-circuit arrangement appearing at the other pair of joining arm points of said bridge-circuit arrangements, said outputs being caused by unbalance of said bridge-circuit arrangement due to a loadinginduced change in impedance in said strain gage, said operationally amplifying means including a high-gain operational amplifier having feedback means preserving gain which is essentially independent of external influences, highly linear phase-sensitive demodulation means, means isolating the output of said operational amplifier from DC and coupling the isolated output of said operational amplifier to the input of said demodulation means, said demodulation means being responsive to the isolated outputs of said operationally amplifying means and converting the isolated outputs of said operationally amplifying means into DC voltages representative thereof; means filtering the DC output voltages of said demodulation means; and digital indicator means responsive to the filtered DC output voltages of said filtering means and characterizing the same to indicate loading of said transducer with high stability, speed of response, and accuracy.
Claim 3
Dependent Claim
98 words
A load-measuring system as set forth in claim 1, wherein said regulated oscillator means includes means transformer-coupling the output from said oscillator means to said given pair of joining arms of said bridge-circuit arrangement, wherein said isolating means includes means transformer-coupling the output of said operational amplifier to the input of said demodulation means, wherein said demodulation means is a ring-diode demodulator, wherein said means transformer-coupling the output from said regulated oscillator means couples said output from said oscillator means to said ring-diode demodulator as reference voltage therefor, and wherein said digital indicating means comprises a digital voltmeter.
Claim 4
Dependent Claim
60 words
A load-measuring system as set forth in claim 1 comprising a further highly linear phase-sensitive demodulation means responsive to said AC voltage applied by said regulated oscillator means and directly converting said AC voltage into DC signals representative thereof; and means controlling the responses of said digital indicator means in accordance with said DC signals from said further demodulation means.
Claim 5
Dependent Claim
72 words
A load-measuring system as set forth in claim 3 wherein said regulated oscillator means comprises an oscillator producing AC voltages related to DC control signals applied thereto, and wherein said controlling means includes means applying DC signals from said further demodulation means to said oscillator as control signals therefor and thereby controlling the levels of said AC voltage applied by said oscillator, whereby effects of lead resistance and demodulation imbalance are offset.
Claim 6
Dependent Claim
48 words
A load-measuring system as set forth in claim 3 wherein said controlling means includes means applying DC signals from said further demodulation means as a reference voltage to the input of said digital indicator means, whereby said digital indicator means is caused to operate as a digital ratiometer.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-11-01 | 1975-05-03 | 1975-11-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-11-01 | 1979-05-03 | 1979-11-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-11-01 | 1983-05-03 | 1983-11-02 | $7700.00 | Window Closed / Lapsed |