US4498044A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method and circuitry for measuring the impedance of a sensor
Assignee: NOVASINA AG A CORP OF SWITZERLAND
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Filing: 1982-05-11
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Granted: 1985-02-05
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Expires: 2002-05-11
Abstract
Abstract A method of measuring the impedance of a sensor by applying a sine-shaped AC voltage and transforming the response signal proportional to said impedance into a DC voltage such that even for very little measured voltage highest linearity is present. The method comprises the steps of generating a square wave voltage together and in synchronism with said AC voltage, applying said AC voltage to said sensor impedance, filtering the resulting AC voltage and bringing it into a defined phase relation to the square wave and rectifying the AC voltage by means of a switch controlled by said square wave. The rectifier circuit is a low-pass circuit having a grounded resistor which by said switch intermittedly is short-circuited.
Inventors
- 👤 Petr Horn
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 23:14
CPC Classifications
G; G01; G01R; G01R27/00; G01R27/02; G01R27/22; G01R27/26; G02; G02B; G02B6/00; G02B6/44; G02B6/4401; G02B6/441; G02B6/4411
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
131 words
Method of measuring the impedance of a sensor by a sine-shaped AC voltage of defined frequency comprising the steps of generating a square wave voltage in synchronism with the sine-shaped AC voltage; applying the sine-shaped AC voltage to a measuring circuit containing said impedance; modifying the resulting AC voltage proportional to said impedance in a selective circuit of a defined phase-frequency- and amplitude-frequency characteristic, thereby bringing said AC voltage into a defined phase relation to said square wave voltage; rectifying the modified AC voltage and transforming it into a DC voltage proportional to said impedance in a rectifier- and low-pass circuit, said rectifying and transforming step being affected by intermittently short-circuiting a grounded resistor of said rectifier- and low-pass circuit by means of a switch controlled by said square wave voltage.
Claim 2
Dependent Claim
131 words
Method of measuring the impedance of a sensor by a sine-shaped AC voltage of defined frequency comprising the steps of generating a square wave voltage in synchronism with the sine-shaped AC voltage; applying the sine-shaped AC voltage to a measuring circuit containing said impedance; modifying the resulting AC voltage proportional to said impedance in a selective circuit of a defined phase-frequency- and amplitude-frequency characteristic, thereby bringing said AC voltage into a defined phase relation to said square wave voltage; rectifying the modified AC voltage and transforming it into a DC voltage proportional to said impedance in a rectifier- and low-pass circuit, said rectifying and transforming step being affected by intermittently short-circuiting a grounded resistor of said rectifier- and low-pass circuit by means of a switch controlled by said square wave voltage.
Claim 3
Dependent Claim
91 words
Circuitry for carrying out the method defined in claim 1 comprising an oscillator circuit (1) for generating a sine-shaped AC voltage and a square wave voltage in synchronism, a measuring circuit (2) connected to the oscillator circuit and containing an impedance to be measured, a rectifier- and low-pass circuit, and a filter circuit connected between said rectifier- and low-pass circuit and said measuring circuit, said rectifier- and low-pass circuit being a low-pass circuit having a grounded resistor and a switch controlled by said square wave voltage for short-circuiting said grounded resistor.
Claim 4
Dependent Claim
18 words
Circutry as defined in claim 2, wherein said measuring circuit comprises a bridge circuit and an impedance transformer.
Claim 5
Dependent Claim
28 words
Circuitry as defined in one of the preceding claims 2 and 3, wherein said measuring circuit comprises a voltage controlled current source (10) and an impedance transformer (11).
Claim 6
Dependent Claim
19 words
Circuitry as defined in claim 1, wherein said impedance to be measured is the resistance of an electrolytic solution.
Claim 7
Dependent Claim
12 words
Circuitry as defined in claim 5 for measuring humidity and water content.
Claim 8
Dependent Claim
15 words
Application of the method of claim 1 in the measurement of an electrolytic solution resistance.
Claim 9
Dependent Claim
14 words
Application as defined in claim 7 in the measurement of humidity and water content.
References Cited (Backward Citations)
US4160205A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1988-02-05 | 1988-08-06 | 1989-02-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-02-05 | 1992-08-06 | 1993-02-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-02-05 | 1996-08-06 | 1997-02-05 | $7700.00 | Window Closed / Lapsed |