US4818977A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Combustible gas detector having temperature stabilization capability
Assignee: MSA Safety Inc
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Filing: 1987-11-03
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Granted: 1989-04-04
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Expires: 2007-11-03
Abstract
Abstract A catalytic gas detector circuit in which the temperature of a resistance gas sensing element, contained in a bridge circuit, is reduced and therefore stabilized by energizing a transistor to draw off current from the sensing element when the sensing element is exposed to high concentrations of combustible hydrocarbon gases.
Inventors
- 👤 William J. Alexander
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 07:44
CPC Classifications
G; G01; G01N; G01N27/00; G01N27/02; G01N27/04; G01N27/12; G01N27/122; G01N27/14; G01N27/16
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
126 words
A catalytic gas detector circuit comprising: a bridge circuit having four branches and having input and output terminals wherein said input terminals are connected to a power source means capable of providing either constant current or constant voltage, and said output terminals are connected to a difference amplifier where; said first branch is a resistance gas sensing element having a catalytic coating that is reactive to combustible hydrocarbon gases; said second branch is a compensating element; said third and fourth branches are resistors; said difference amplifier output is connected to a current bypass means, that is parallel connected across said sensing element and responsive to said amplifier output, to pass current and; further having, a means to measure the current passed by said current bypass device.
Claim 2
Dependent Claim
126 words
A catalytic gas detector circuit comprising: a bridge circuit having four branches and having input and output terminals wherein said input terminals are connected to a power source means capable of providing either constant current or constant voltage, and said output terminals are connected to a difference amplifier where; said first branch is a resistance gas sensing element having a catalytic coating that is reactive to combustible hydrocarbon gases; said second branch is a compensating element; said third and fourth branches are resistors; said difference amplifier output is connected to a current bypass means, that is parallel connected across said sensing element and responsive to said amplifier output, to pass current and; further having, a means to measure the current passed by said current bypass device.
Claim 3
Dependent Claim
17 words
The detector circuit according to claim 1 wherein said difference amplifier is an integrated circuit operational amplifier.
Claim 4
Dependent Claim
14 words
The detector circuit according to claim 1 wherein said bypass means is a transistor.
References Cited (Backward Citations)
US3997837A
Cited
US4164699A
Cited
US4028057A
Cited
US4080821A
Cited
US4305724A
Cited
US4533520A
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 |