US4817414A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Measuring arrangement for detecting the level of combustible gases mixed with air
Assignee: Draegerwerk AG and Co KGaA
•
Filing: 1987-06-30
•
Granted: 1989-04-04
•
Expires: 2007-06-30
Abstract
Abstract A measuring arrangement for detecting the level of combustible gases mixed with air such as methane in air includes a measuring sensor responsive to the heat-conductivity of the proportion of the gas to be detected. The effect of the ambient temperature on the heat-conductivity measurement is eliminated through a simple circuit configuration consuming low power for a measurement of heat-conductivity alone as well as for such a measurement in combination with a reaction-heat measurement. For this purpose, the heat-conductivity sensor is connected to a constant-current source. A measuring takeoff circuit for the heat conductivity is connected in parallel to the heat-conductivity sensor and is provided in the form of a series circuit including a measuring signal terminal and a compensating voltage source. The compensating voltage source generates a compensating voltage which changes in magnitude and direction in correspondence with the temperature-dependent change in the voltage drop across the heat-conductivity sensor.
Inventors
- 👤 Werner Hagen
- 👤 Claus-Dieter Brandt
- 👤 Gerd Mahrt
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 08:27
CPC Classifications
G; G01; G01N; G01N27/00; G01N27/02; G01N27/04; G01N27/14; G01N27/18
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
188 words
A measuring arrangement for detecting the proportion of a combustible gas mixed with air such as methane in air, the measuring arrangement comprising: constant-current supply means for supplying a constant current; a heat-conductivity measuring sensor for responding to the heat conductivity of the proportion of gas to be detected, said heat-conductivity measuring sensor being connected to said supply means for receiving said constant current with a voltage drop occurring across said measuring sensor that changes in dependence upon temperature; measuring signal terminal means for taking off a measuring voltage signal; compensating voltage source means for generating a compensating voltage which changes in magnitude and direction in correspondence with the temperature-dependent changes in said voltage drop; said measuring signal terminal means and said compensating voltage source means conjointly defining a series circuit connected in parallel with said measuring sensor; and, said compensating voltage source means being connected into said series circuit so as to cause said compensating voltage to act in opposition to said temperature-dependent changes in said voltage drop whereby said measuring voltage signal is independent of changes in temperature and is exclusively indicative of said heat conductivity.
Claim 2
Dependent Claim
188 words
A measuring arrangement for detecting the proportion of a combustible gas mixed with air such as methane in air, the measuring arrangement comprising: constant-current supply means for supplying a constant current; a heat-conductivity measuring sensor for responding to the heat conductivity of the proportion of gas to be detected, said heat-conductivity measuring sensor being connected to said supply means for receiving said constant current with a voltage drop occurring across said measuring sensor that changes in dependence upon temperature; measuring signal terminal means for taking off a measuring voltage signal; compensating voltage source means for generating a compensating voltage which changes in magnitude and direction in correspondence with the temperature-dependent changes in said voltage drop; said measuring signal terminal means and said compensating voltage source means conjointly defining a series circuit connected in parallel with said measuring sensor; and, said compensating voltage source means being connected into said series circuit so as to cause said compensating voltage to act in opposition to said temperature-dependent changes in said voltage drop whereby said measuring voltage signal is independent of changes in temperature and is exclusively indicative of said heat conductivity.
Claim 3
Dependent Claim
29 words
The measuring arrangement of claim 1, wherein said compensating voltage source means comprises a compensating constant-current source and a trimmable temperature-measuring sensor connected in parallel with said constant-current source.
Claim 4
Dependent Claim
26 words
The measuring arrangement of claim 2, wherein said compensating voltage source means further comprises a trimmable, temperature-independent, dropping resistor connected in series with said temperature-measuring sensor.
Claim 5
Dependent Claim
47 words
The measuring arrangement of claim 1, comprising: a measuring bridge connected to said constant-current source, said measuring bridge having a first measuring branch containing said heat-conductivity measuring sensor and a second measuring branch containing a reaction-heat sensor for responding to the reaction heat of the combustible gas.
Claim 6
Dependent Claim
178 words
A measuring arrangement for detecting the portion of a combustible gas mixed with air such as methane in air, the measuring arrangement comprising: supply means for supplying a current; a heat-conductivity measuring sensor for responding to the heat conductivity of the proportion of gas to be detected, said measuring sensor having a temperature characteristic curve and being connected to said supply means for receiving said current and providing a first signal indicative of said heat conductivity, said signal being influenced by temperature; temperature-measuring sensor for providing a second signal indicative of temperature; signal processing means connected to said heat-conductivity measuring sensor and also to said temperature-measuring sensor for correcting the influence on said first signal by the temperature; and, said signal processing means including: a multiplexer unit having a multiplexer for receiving said first and second signals and an analog-to-digital convertor; and, microprocessor connected to the output of said convertor, the microprocessor including: storage means for storing the temperature characteristic curve of said heat-conductivity measuring sensor; and, correction means for correcting said signals using said temperature characteristic curve.
Claim 7
Dependent Claim
178 words
A measuring arrangement for detecting the portion of a combustible gas mixed with air such as methane in air, the measuring arrangement comprising: supply means for supplying a current; a heat-conductivity measuring sensor for responding to the heat conductivity of the proportion of gas to be detected, said measuring sensor having a temperature characteristic curve and being connected to said supply means for receiving said current and providing a first signal indicative of said heat conductivity, said signal being influenced by temperature; temperature-measuring sensor for providing a second signal indicative of temperature; signal processing means connected to said heat-conductivity measuring sensor and also to said temperature-measuring sensor for correcting the influence on said first signal by the temperature; and, said signal processing means including: a multiplexer unit having a multiplexer for receiving said first and second signals and an analog-to-digital convertor; and, microprocessor connected to the output of said convertor, the microprocessor including: storage means for storing the temperature characteristic curve of said heat-conductivity measuring sensor; and, correction means for correcting said signals using said temperature characteristic curve.
Claim 8
Dependent Claim
52 words
The measuring arrangement of claim 5, comprising: a measuring bridge having a first measuring branch containing said heat-conductivity measuring sensor and a second measuring branch containing a reaction-heat sensor for responding to the reaction heat of the combustible gas; and, constant-current source means for supplying a constant current to said measuring bridge.
References Cited (Backward Citations)
US3091957A
Cited
DE1698549A1
Cited
DE1648857A1
Cited
US3519391A
Cited
FR2456950A1
Cited
US4498330A
Cited
DE3127431A1
Cited
GB2103806A
Cited
US4571543A
Cited
US4572900A
Cited
GB2165948A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1992-04-03 | 1992-10-03 | 1993-04-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-04-03 | 1996-10-03 | 1997-04-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-04-03 | 2000-10-03 | 2001-04-04 | $7700.00 | Window Closed / Lapsed |