WO1999017110A1 - Combustible gas sensor with integral hydrogen generator - Google Patents
Combustible gas sensor with integral hydrogen generator Download PDFInfo
- Publication number
- WO1999017110A1 WO1999017110A1 PCT/US1998/019844 US9819844W WO9917110A1 WO 1999017110 A1 WO1999017110 A1 WO 1999017110A1 US 9819844 W US9819844 W US 9819844W WO 9917110 A1 WO9917110 A1 WO 9917110A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- combustible gas
- sensor
- hydrogen generator
- gas sensor
- combustible
- Prior art date
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Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/0004—Gaseous mixtures, e.g. polluted air
- G01N33/0006—Calibrating gas analysers
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/0004—Gaseous mixtures, e.g. polluted air
- G01N33/0009—General constructional details of gas analysers, e.g. portable test equipment
- G01N33/0027—General constructional details of gas analysers, e.g. portable test equipment concerning the detector
- G01N33/0036—Specially adapted to detect a particular component
- G01N33/0047—Specially adapted to detect a particular component for organic compounds
Definitions
- This invention relates to a method and apparatus for automatically testing the response of combustible gas sensors and more particularly to a combustible gas sensor with integral hydrogen generator.
- Combustible gas sensors have been used for over fifty years to detect the presence of potentially hazardous concentrations of flammable gases or vapors. They are widely used in industry for safety purposes, providing a warning of potentially hazardous conditions before gas levels reach explosive levels.
- Commercial combustible gas sensors detect gases through the use of a heated catalytic element. When a combustible gas or vapor comes in contact with this element, the gas or vapor is burned, causing an increase in heat on that element. The resistance of the catalytic element changes in proportion to the combustion heat, and the resistance change is compared to a similar but inert reference element.
- the catalytic element and the reference element form two legs of a simple Wheatstone bridge circuit which measures the resistance change caused by the presence of combustible gases and vapors.
- Combustible gas detectors are well known in the art and are described by Warren J. Reilly in an article entitled “Combustible Gas Detectors” based on a paper delivered at the Arrowspace/Test Measurement Conference, Philadelphia, 1975.
- the combustible gas sensing system of the present invention provides the automatic checking of the combustible sensor every twenty four hours and greatly reduces the manual labor needed to verify that the gas detection system is operable and will respond in the event of gas leakage.
- the present invention is intended to obviate the above- described problems and has for its object to provide a system for verifying the response of a combustible gas sensor by combining the combustible gas sensor with an integral hydrogen generator in one explosion-proof assembly.
- the present invention provides an electrochemical hydrogen generator capable of delivering relative high H 2 concentrations (needed to properly test this type of sensor) to the combustible sensor, and integrating the generator into the sensor itself.
- the result is a device that includes both the sensor and a mechanism for automatically testing that sensor to detect loss of sensitivity.
- an assembly for verifying the response of a combustible gas sensor including an explosion proof housing including a catalytic combustible gas sensor having active and passive sensing elements disposed within the housing.
- a hydrogen generator is disposed within the housing and separated from the catalytic combustible gas sensor by a gas diffusion chamber.
- the gas diffusion chamber has an opening in the wall of the explosion proof housing to allow combustible gases in the ambient air to diffuse to the sensing elements of the catalytic combustible sensor.
- a sintered metal flame arrestor separates the combustible gas sensing elements from the combustible gas chamber and a sintered metal flame arrestor separates the hydrogen generator from the combustible gas chamber.
- the hydrogen generator includes an electrochemical cell containing two embedded electrodes and a water based electrolyte, the electrolyte being a hygroscopic acid retained within a porous plastic medium within the hydrogen generator so that when water is electrolyzed to produce hydrogen, the water that is lost is replenished by the humidity in the ambient air to insure sufficient water for the hydrogen generation process over an extended period of time.
- a method including the steps of energizing the hydrogen generator of the aforesaid type to deliver a hydrogen test sample to produce a concentration above a predetermined lower explosive limit (LEL) within the gas diffusion chamber, causing the test gas to pass through the sintered metal flame arrestor to a sensor cavity adjacent the catalytic combustible gas sensor, and monitoring the output of the combustible sensor during the gas generation cycle.
- LEL lower explosive limit
- Fig. 1 is an elevational view partly in section of a combustible gas sensor with integral hydrogen generator embodying the present invention.
- Fig. 2 is a schematic diagram of the electrical circuit in the combustible gas sensor with integral hydrogen generator illustrated in Fig. 1.
- the assembly includes a catalytic combustible gas sensor 12 and a hydrogen generator 14 both disposed within an explosion proof housing 16.
- the catalytic combustible gas sensor has an active element 18 and a passive element 20.
- the passive element 20 is sometimes referred to as a reference element and the reference element 20 and active element 18 are arranged in a Wheatstone bridge. As shown in Fig. 2 the active and passive elements 18 and 20 form two legs of the
- the circuit also includes an adjustable resistor 26.
- combustible gas molecules react, via a catalyst, to form oxidation products on the active (open to air) element 18 increasing its temperature and resistance.
- the sensing elements may be either coated with a catalyst and coiled, or encased in a catalytic bead element, as well known in the art.
- a thermal barrier 28 preferably made from Teflon, and positioned to keep the heat generated at the active element 18, when exposed to combustible gases, from transferring to the passive element 20, which does not heat up on contact with combustible gases.
- a sintered metal flame arrestor 30 of stainless steel is positioned within the housing 16 to keep the sensing elements 18 and 20 isolated within the housing while allowing combustible gases to diffuse to a sensor cavity 32 adjacent to the sensing elements 18 and 20.
- the hydrogen generator 14 is mounted within the lower portion of the explosion proof housing 16 and is separated from the combustible gas sensor by a gas diffusion chamber 34.
- the gas diffusion chamber 34 has an opening 34a to the exterior of the housing 16.
- the gas diffusion chamber 34 is bounded by the sintered metal flame arrestor 30 which isolates the sensing elements 18 and 20 of the combustible gas sensor 12 and a second sintered metal flame arrestor 36 which isolates the hydrogen generator 14 from the gas diffusion chamber.
- the gas diffusion opening 34a allows ambient air and any combustible gases to diffuse into the chamber 34 of the housing 16 so that they are sensed by the active element 18 of the sensor.
- the hydrogen generator 14 is an electrochemical cell containing two embedded electrodes 38 and 40, Fig. 2, and a water based electrolyte 42, Fig. 1. In operation, a 2.5 volts DC potential is placed across the electrodes 38 and 40 when the switch 44 is closed with the current being limited by resistor 46 to about 60mA.
- water will be split into hydrogen and oxygen.
- the hydrogen is evolved from the surface of the electrode 38 nearest the diffusion opening and is allowed to move by natural diffusion through the sintered metal flame arrestor 36, across the gas diffusion chamber 34 and through the sintered metal flame arrestor 30 into the sensor cavity 32 adjacent the sensing elements 18 and 20.
- the hydrogen generator 14 relies on water inside the generator cell for hydrogen production. Since the generator cell must be relatively small from a packaging standpoint, the amount of water could potentially limit a number of tests that could be run prior to the generator failing. Requiring generators to be refilled with water adds a maintenance requirement that particularly negates the value of the self-check. Formulating the electrolyte so that it pulls water out of the air allows the generator to run for well over a year without any type of service. Basically, the electrolyte is a hygroscopic acid, such for example as concentrated sulfuric acid, which is retained inside a porous plastic medium similar to filter paper. When water is electrolyzed to produce hydrogen, the water that is lost is replenished by the humidity in the ambient air.
- the hydrogen generator 14 is activated on a periodic basis under software control for a fixed period of time. As may be seen in Fig. 2, hydrogen generator is activated when the switch 44 is closed. The switch 44 is microprocessor controlled. The current to the generator 14 is controlled to deliver a hydrogen concentration above 5 % LEL (0.2% hydrogen by volume).
- Lower explosive limit (LEL) data for common combustible gases and vapors are published by the National Fire Protection Association. The LEL is the lowest concentration of the gas, mixed with air, which will propagate a flame. In normal air, the LEL can vary from 0.6% to 12.5 % , by volume. Concentrations of gas above the LEL will propagate flame until the upper explosive limit (UEL) is reached.
- UEL upper explosive limit
- the output of the combustible gas sensor 12 is monitored during the gas generation cycle. If the sensor output reaches a predetermined LEL value, normally 5 % , the sensor is deemed to have passed the test and the hydrogen generator 14 is shut off. If the sensor does not reach the predetermined LEL value within a fixed time, the sensor 12 is deemed to have failed and an alarm signal is generated.
- a predetermined LEL value normally 5 %
Abstract
An assembly (10) for verifying the response of a combustible gas sensor combining a catalytic combustible gas sensor (12) and a hydrogen generator (14) in one explosion proof housing (16).
Description
COMBUSTIBLE GAS SENSOR WITH INTEGRAL HYDROGEN GENERATOR
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method and apparatus for automatically testing the response of combustible gas sensors and more particularly to a combustible gas sensor with integral hydrogen generator.
2. Description of the Related Art
Combustible gas sensors have been used for over fifty years to detect the presence of potentially hazardous concentrations of flammable gases or vapors. They are widely used in industry for safety purposes, providing a warning of potentially hazardous conditions before gas levels reach explosive levels. Commercial combustible gas sensors detect gases through the use of a heated catalytic element. When a combustible gas or vapor comes in contact with this element, the gas or vapor is burned, causing an increase in heat on that element. The resistance of the catalytic element changes in proportion to the combustion heat, and the resistance change is compared to a similar but inert reference element. In a typical catalytic gas detector, the catalytic element and the reference element form two legs of a simple Wheatstone bridge circuit which measures the resistance change caused by the presence of combustible gases and vapors. Combustible gas detectors are well known in the art and are described by Warren J. Reilly in an article entitled "Combustible Gas Detectors" based on a paper
delivered at the Arrowspace/Test Measurement Conference, Philadelphia, 1975.
There are many manufacturers of this type of combustible gas sensor and the technology has been widely applied to leak detection applications in chemical and petrochemical plants, oil and gas exploration wells and platforms, and a variety of other industries where the potential for either leakage or buildup of potentially explosive levels of gas or vapor exist.
All combustible gas sensors using this technology suffer from the same basic problem, which is the slow, or in some cases, fast, passivation or chemical attack of the catalytic surface on which proper operation depends. This process occurs when sensors are exposed to air containing small amounts of silicone vapor, lead compounds, hydrogen sulphide, and organic vapors containing halogens that can form strong acids on the surfaces during the combustion process. Because combustible gas sensors are often used in ambient air environments where there can be no control over the types of poisoning agents that might be encountered, users of combustible gas sensors are required to manually check sensor operation on a regular schedule. Since sensors can be poisoned quickly when exposed to the wrong environment, frequent checking is desirable to insure the integrity of the detection system.
When a combustible gas sensor becomes poisoned, it looses sensitivity to the gases it is intended to measure. However, this poisoned condition is not detectable automatically because it appears to be the same as a properly operating sensor exposed to clean air. The only reliable sensor test is to manually expose a sensor to a combustible gas and observe the response.
Heretofore there have been attempts to automate this process by attaching external gas cylinders to the sensor and using a solenoid valve to periodically allow gas to flow to the sensor. However, this approach is expensive, made more so by the fact that the gas delivery system must be explosion-proof.
The combustible gas sensing system of the present invention provides the automatic checking of the combustible sensor every twenty four hours and greatly reduces the manual labor needed to verify that the gas detection system is operable and will respond in the event of gas leakage.
SUMMARY OF THE INVENTION
Accordingly, the present invention is intended to obviate the above- described problems and has for its object to provide a system for verifying the response of a combustible gas sensor by combining the combustible gas sensor with an integral hydrogen generator in one explosion-proof assembly. The present invention provides an electrochemical hydrogen generator capable of delivering relative high H2 concentrations (needed to properly test this type of sensor) to the combustible sensor, and integrating the generator into the sensor itself. The result is a device that includes both the sensor and a mechanism for automatically testing that sensor to detect loss of sensitivity.
Accordingly to one aspect of the invention there is provided an assembly for verifying the response of a combustible gas sensor including an explosion proof housing including a catalytic combustible gas sensor having active and passive sensing elements disposed within the housing. A hydrogen generator is disposed within the housing and separated from the catalytic combustible gas sensor by a gas diffusion chamber. The gas diffusion chamber has an opening in the wall of the explosion proof housing to allow combustible gases in the ambient air to diffuse to the sensing elements of the catalytic combustible sensor. A sintered metal flame arrestor separates the combustible gas sensing elements from the combustible gas chamber and a sintered metal flame arrestor separates the hydrogen generator from the combustible gas chamber. In another aspect of the invention, the hydrogen generator includes an electrochemical cell containing two embedded electrodes and a water based electrolyte, the electrolyte being a hygroscopic acid retained within a porous plastic medium within the hydrogen generator so that when water is electrolyzed to produce hydrogen, the water that is lost is replenished by the humidity in the ambient air to insure sufficient water for the hydrogen generation process over an extended period of time.
In a further aspect of the invention there is provided a method including the steps of energizing the hydrogen generator of the aforesaid type to deliver a hydrogen test sample to produce a concentration above a predetermined lower explosive limit (LEL) within the gas diffusion chamber, causing the test gas to pass through the
sintered metal flame arrestor to a sensor cavity adjacent the catalytic combustible gas sensor, and monitoring the output of the combustible sensor during the gas generation cycle.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will be described in further detail with reference to the accompanying drawings.
Fig. 1 is an elevational view partly in section of a combustible gas sensor with integral hydrogen generator embodying the present invention.
Fig. 2 is a schematic diagram of the electrical circuit in the combustible gas sensor with integral hydrogen generator illustrated in Fig. 1.
DETAILED DESCRD7TION OF THE PREFERRED EMBODIMENT
Referring to Fig. 1 there is disclosed an assembly 10 for verifying the response of a combustible gas sensor. The assembly includes a catalytic combustible gas sensor 12 and a hydrogen generator 14 both disposed within an explosion proof housing 16. The catalytic combustible gas sensor has an active element 18 and a passive element 20. The passive element 20 is sometimes referred to as a reference element and the reference element 20 and active element 18 are arranged in a Wheatstone bridge. As shown in Fig. 2 the active and passive elements 18 and 20 form two legs of the
Wheatstone bridge with the other two legs being formed by the resistors 22 and 24. The circuit also includes an adjustable resistor 26. In operation combustible gas molecules react, via a catalyst, to form oxidation products on the active (open to air) element 18 increasing its temperature and resistance. The sensing elements may be either coated with a catalyst and coiled, or encased in a catalytic bead element, as well known in the art.
As may be seen in Fig. 1 there is a thermal barrier 28, preferably made from Teflon, and positioned to keep the heat generated at the active element 18, when exposed to combustible gases, from transferring to the passive element 20, which does
not heat up on contact with combustible gases. A sintered metal flame arrestor 30 of stainless steel is positioned within the housing 16 to keep the sensing elements 18 and 20 isolated within the housing while allowing combustible gases to diffuse to a sensor cavity 32 adjacent to the sensing elements 18 and 20. As may be seen in Fig. 1, the hydrogen generator 14 is mounted within the lower portion of the explosion proof housing 16 and is separated from the combustible gas sensor by a gas diffusion chamber 34. The gas diffusion chamber 34 has an opening 34a to the exterior of the housing 16. The gas diffusion chamber 34 is bounded by the sintered metal flame arrestor 30 which isolates the sensing elements 18 and 20 of the combustible gas sensor 12 and a second sintered metal flame arrestor 36 which isolates the hydrogen generator 14 from the gas diffusion chamber. The gas diffusion opening 34a allows ambient air and any combustible gases to diffuse into the chamber 34 of the housing 16 so that they are sensed by the active element 18 of the sensor. The hydrogen generator 14 is an electrochemical cell containing two embedded electrodes 38 and 40, Fig. 2, and a water based electrolyte 42, Fig. 1. In operation, a 2.5 volts DC potential is placed across the electrodes 38 and 40 when the switch 44 is closed with the current being limited by resistor 46 to about 60mA. At this power level, water will be split into hydrogen and oxygen. The hydrogen is evolved from the surface of the electrode 38 nearest the diffusion opening and is allowed to move by natural diffusion through the sintered metal flame arrestor 36, across the gas diffusion chamber 34 and through the sintered metal flame arrestor 30 into the sensor cavity 32 adjacent the sensing elements 18 and 20.
The hydrogen generator 14 relies on water inside the generator cell for hydrogen production. Since the generator cell must be relatively small from a packaging standpoint, the amount of water could potentially limit a number of tests that could be run prior to the generator failing. Requiring generators to be refilled with water adds a maintenance requirement that particularly negates the value of the self-check. Formulating the electrolyte so that it pulls water out of the air allows the generator to run for well over a year without any type of service. Basically, the electrolyte is a hygroscopic acid, such for example as concentrated sulfuric acid, which is retained inside a porous plastic medium similar to filter paper. When water is electrolyzed to
produce hydrogen, the water that is lost is replenished by the humidity in the ambient air.
In operation, the hydrogen generator 14 is activated on a periodic basis under software control for a fixed period of time. As may be seen in Fig. 2, hydrogen generator is activated when the switch 44 is closed. The switch 44 is microprocessor controlled. The current to the generator 14 is controlled to deliver a hydrogen concentration above 5 % LEL (0.2% hydrogen by volume). Lower explosive limit (LEL) data for common combustible gases and vapors are published by the National Fire Protection Association. The LEL is the lowest concentration of the gas, mixed with air, which will propagate a flame. In normal air, the LEL can vary from 0.6% to 12.5 % , by volume. Concentrations of gas above the LEL will propagate flame until the upper explosive limit (UEL) is reached. Above the UEL, gas concentrations are too rich to support combustion. The output of the combustible gas sensor 12 is monitored during the gas generation cycle. If the sensor output reaches a predetermined LEL value, normally 5 % , the sensor is deemed to have passed the test and the hydrogen generator 14 is shut off. If the sensor does not reach the predetermined LEL value within a fixed time, the sensor 12 is deemed to have failed and an alarm signal is generated.
While a preferred embodiment of this invention has been illustrated, it is to be understood that other modifications thereof may be made within the scope of the appended claims.
Claims
1. An assembly for verifying the response of a combustible gas sensor
comprising an explosion proof housing, a catalytic combustible gas sensor having an
active and a passive sensing elements disposed within said housing, and a hydrogen
generator disposed within said housing and separated from said catalytic combustible gas sensor by a gas diffusion chamber, said gas diffusion chamber having an opening in the
wall of said explosion proof housing to allow combustible gases in the ambient air to
diffuse to said sensing elements of the catalytic combustible gas sensor.
2. The assembly according to claim 1 wherein a sintered metal flame arrestor separates said combustible gas sensing elements from said combustible gas
chamber.
3. The assembly according to claim 2 wherein a sintered metal flame
arrestor separates said hydrogen generator from said combustible gas chamber.
4. An assembly according to claim 1 wherein said hydrogen generator
comprises an electrochemical cell containing two embedded electrodes and a water based
electrolyte.
5. An assembly according to claim 4 wherein said electrolyte in said
hydrogen generator is a hygroscopic acid retained within a porous plastic medium within
said hydrogen generator so that when water is electrolyzed to produce hydrogen the
water that is lost is replenished by the humidity in the ambient air to insure sufficient water for the hydrogen generation process over an extended period of time.
6. The assembly according to claim 5 wherein said hygroscopic acid is concentrated sulfur ic acid.
7. In a system for verifying a response of a combustible gas sensor
comprising an explosion proof housing, a catalytic combustible gas sensor having an
active and a passive sensing elements disposed within said housing, and a hydrogen
generator disposed within said housing and separated from said catalytic combustible gas
sensor by a gas diffusion chamber, said gas diffusion chamber having an opening in the
wall of said explosion proof housing to allow combustible gases in the ambient gas to
diffuse to said sensing elements of the catalytic combustible gas sensor, and a sintered
metal flame arrestor separating said combustible gas sensing elements from said
combustible gas chamber, the method comprising the steps of energizing the hydrogen generator to deliver a hydrogen test sample to produce a concentration above a
predetermined lower explosive limit (LEL) within the gas diffusion chamber, causing the
test gas to pass through the sintered metal flame arrestor to a sensor cavity adjacent said
catalytic combustible gas sensor, and monitoring the output of the combustible sensor
during the gas generation cycle.
8. The method according to claim 7 wherein the concentration in the gas
diffusion chamber is above about 5 % LEL.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US94208397A | 1997-10-01 | 1997-10-01 | |
| US08/942,083 | 1997-10-01 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| WO1999017110A1 true WO1999017110A1 (en) | 1999-04-08 |
Family
ID=25477550
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| PCT/US1998/019844 WO1999017110A1 (en) | 1997-10-01 | 1998-09-24 | Combustible gas sensor with integral hydrogen generator |
Country Status (1)
| Country | Link |
|---|---|
| WO (1) | WO1999017110A1 (en) |
Cited By (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2356708A (en) * | 1999-11-27 | 2001-05-30 | Central Research Lab Ltd | Sensor system with self-test facility |
| WO2005119248A1 (en) * | 2004-05-28 | 2005-12-15 | Honeywell International Inc. | Calibration device for gas sensors |
| WO2006060320A2 (en) * | 2004-11-30 | 2006-06-08 | Honeywell International Inc. | Nano-crystalline and/or metastable metal hydrides as hydrogen source for sensor calibration and self-testing |
| WO2006063183A2 (en) * | 2004-12-08 | 2006-06-15 | Honeywell International Inc. | Electrochemical sensor system |
| US7111493B2 (en) | 2002-11-26 | 2006-09-26 | Proton Energy Systems, Inc. | Combustible gas detection system |
| US7159444B2 (en) | 2002-11-26 | 2007-01-09 | Proton Energy Systems, Inc. | Combustible gas detection systems and method thereof |
| US7174766B2 (en) | 2005-05-24 | 2007-02-13 | Honeywell International Inc. | Calibration device for carbon dioxide sensor |
| US8826724B2 (en) | 2010-12-24 | 2014-09-09 | Honeywell International Inc. | Carbon dioxide sensor |
| DE102015015152A1 (en) | 2015-11-25 | 2017-06-01 | Dräger Safety AG & Co. KGaA | Method for checking a gas sensor in a gas measuring system |
| EP3220141A1 (en) | 2016-03-18 | 2017-09-20 | Dräger Safety AG & Co. KGaA | Method for checking a gas sensor and gas measuring device, and gas warning system with a test device for checking a gas sensor |
| EP3220142A1 (en) | 2016-03-18 | 2017-09-20 | Dräger Safety AG & Co. KGaA | Method for checking a gas sensor and gas measuring device, and gas warning system with a test device for checking a gas sensor |
| DE102016013958A1 (en) | 2016-11-23 | 2018-05-24 | Drägerwerk AG & Co. KGaA | Device with a pumping device for checking a functional readiness of a gas guide element of a gas measuring system |
| DE102016013959A1 (en) | 2016-11-23 | 2018-05-24 | Drägerwerk AG & Co. KGaA | Test device for a verification of a gas guide element |
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Cited By (30)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2356708A (en) * | 1999-11-27 | 2001-05-30 | Central Research Lab Ltd | Sensor system with self-test facility |
| US7159444B2 (en) | 2002-11-26 | 2007-01-09 | Proton Energy Systems, Inc. | Combustible gas detection systems and method thereof |
| US7111493B2 (en) | 2002-11-26 | 2006-09-26 | Proton Energy Systems, Inc. | Combustible gas detection system |
| US7073368B2 (en) | 2004-05-28 | 2006-07-11 | Honeywell International Inc. | Calibration device for gas sensors |
| WO2005119248A1 (en) * | 2004-05-28 | 2005-12-15 | Honeywell International Inc. | Calibration device for gas sensors |
| WO2006060320A2 (en) * | 2004-11-30 | 2006-06-08 | Honeywell International Inc. | Nano-crystalline and/or metastable metal hydrides as hydrogen source for sensor calibration and self-testing |
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| WO2006063183A3 (en) * | 2004-12-08 | 2006-12-28 | Honeywell Int Inc | Electrochemical sensor system |
| US7174766B2 (en) | 2005-05-24 | 2007-02-13 | Honeywell International Inc. | Calibration device for carbon dioxide sensor |
| US8826724B2 (en) | 2010-12-24 | 2014-09-09 | Honeywell International Inc. | Carbon dioxide sensor |
| DE102015015152A1 (en) | 2015-11-25 | 2017-06-01 | Dräger Safety AG & Co. KGaA | Method for checking a gas sensor in a gas measuring system |
| US9945827B2 (en) | 2015-11-25 | 2018-04-17 | Dräger Safety AG & Co. KGaA | Method for testing a gas sensor in a gas-measuring system |
| EP3220142A1 (en) | 2016-03-18 | 2017-09-20 | Dräger Safety AG & Co. KGaA | Method for checking a gas sensor and gas measuring device, and gas warning system with a test device for checking a gas sensor |
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| US10712324B2 (en) | 2016-11-23 | 2020-07-14 | Drägerwerk AG & Co. KGaA | Device with a pumping device for testing the operational capability of a gas guide element of a gas-measuring system |
| DE102016013959B4 (en) | 2016-11-23 | 2019-08-08 | Drägerwerk AG & Co. KGaA | Test device for a verification of a gas guide element |
| DE102016013959A1 (en) | 2016-11-23 | 2018-05-24 | Drägerwerk AG & Co. KGaA | Test device for a verification of a gas guide element |
| DE102016013958A1 (en) | 2016-11-23 | 2018-05-24 | Drägerwerk AG & Co. KGaA | Device with a pumping device for checking a functional readiness of a gas guide element of a gas measuring system |
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