Abstract: A gas detection instrument comprises a combustible gas sensor and associated circuitry, which supplies power to the sensor and measures and displays resulting sensor response. The supplied power is switched between timed pulses of electricity and steady state electricity, with the intermittent electricity being employed only when no significant change in sensor output has been detected. Alternatively, timed pulses of electricity are maintained, and predictive software algorithms are used to give readings for gas concentration during interruption of the power supply. The sensor operation enables the instrument to respond to rapid changes in gas concentration while minimizing power consumption of the sensor.

Abstract: A gas detection instrument comprises a combustible gas sensor and associated circuitry, which supplies power to the sensor and measures and displays resulting sensor response. The supplied power is switched between timed pulses of electricity and steady state electricity, with the intermittent electricity being employed only when no significant change in sensor output has been detected. Alternatively, timed pulses of electricity are maintained, and predictive software algorithms are used to give readings for gas concentration during interruption of the power supply. The sensor operation enables the instrument to respond to rapid changes in gas concentration while minimizing power consumption of the sensor.

Abstract: A catalytic bead sensor or a semiconductor sensor is operated in a manner in which the power requirement is greatly reduced. The reduction in power is accomplished by operating the sensor at a temperature less than the desired operating temperature in the absence of a combustible gas and increasing to the desired operating temperature when the sensor is exposed to a combustible gas.

Abstract: A calibration adaptor for a gas sensing device having a gas entry port therein includes a base piece having a gas entry port therein which is fixedly attached to a surface of the gas sensing device, and provided with means for releasably retaining the base piece in a first position in which the gas entry port of the gas sensing device is open to detect ambient gases, and means for moving the attached base piece to a second position in which the gas entry port of the base piece is aligned with the gas entry port of the gas sensing device, and controls entry of gas into the gas entry port of the gas sensing device. A calibration gas source may be attached to the gas entry port of the base piece.

Abstract: A compact, long-lived oxygen sensor having an aqueous electrolyte and three gas diffusion electrodes, a working electrode, a reference electrode and a counter electrode. A porous, hydrophobic means is employed in conjunction with the counter electrode to allow air pressure in the sensor to be balanced with atmospheric pressure. The working and reference electrodes are further protected from contact with flow of electrolyte from the reservoir by a separator, so that the current output is fairly independent of sensor movement.

Abstract: A method for testing gas detection instruments includes providing at least two reagents, immobilizing at least one of the reagents into a matrix material, heating the matrix material until the matrix permits movement of the reagent and generating a gas responsive to chemical reaction between the reagents. The gas is introduced into the sensor portion of the gas detection instrument to test the same. The reagents may each be immobilized on the matrix material with the heating serving to soften or melt the matrix material to permit chemical interaction. In a preferred embodiment, the heating is effected at about 90 to 150° C. The method may be employed to generate carbon monoxide or other gases of interest. Corresponding apparatus is provided. The apparatus may be structured to be inserted into or receive the gas detection instrument or have its output in communication therewith.

Abstract: A method and apparatus for diagnosing defects in electrochemical gas sensors, in which the water vapor pressure of the air surrounding a sensor is suddenly changed by changing to more dry or more humid air, thereby causing a sharp change in the acidity at the working electrode, and hence, a transient current from the sensor. The response of the sensor to the change in water vapor pressure is monitored and is used for sensor diagnostics. Lack of sensitivity of the sensor to the water vapor pressure change is an indication that the sensor does not have appropriate sensitivity to the gas to be detected. The method and apparatus are particularly useful for diagnostic testing of sensors without a gas filter.

Abstract: A method of fabricating a catalytic bead sensor with improved stability by forming a coil of metal wire, depositing onto the coil of wire by CVD, PECVD, thermal spraying or electrophoretic deposition at least one first layer of an insulating, crack-free refractory coating, to form thereby a coil of coated wire, and depositing onto the coated wire coil at least one further layer to convert the coated wire coil to a sensing or compensating bead.

Abstract: A catalytic bead sensor or a semiconductor sensor is operated in a manner in which the power requirement is greatly reduced. The reduction in power is accomplished by operating the sensor at a temperature less than the desired operating temperature in the absence of a combustible gas and increasing to the desired operating temperature when the sensor is exposed to a combustible gas.

Abstract: A method and apparatus for diagnosing defects in electrochemical gas sensors, in which the water vapor pressure of the air surrounding a sensor is suddenly changed by changing to more dry or more humid air, thereby causing a sharp change in the acidity at the working electrode, and hence, a transient current from the sensor. The response of the sensor to the change in water vapor pressure is monitored and is used for sensor diagnostics. Lack of sensitivity of the sensor to the water vapor pressure change is an indication that the sensor does not have appropriate sensitivity to the gas to be detected. The method and apparatus are particularly useful for diagnostic testing of sensors without a gas filter.

Abstract: A poison resistant combustible gas sensing element, a method for its production and a method for determining poisoning of the element. The element includes an electric heating element, an inner layer coated on the electric heating element and containing a precious metal catalyst supported on a porous oxide, the precious metal catalyst catalyzing combustion of a combustible gas to be detected by the element, and an outer layer overlaying the first layer, and containing a catalytic compound capable of trapping gases which poison the precious metal catalyst, the catalytic compound being supported on a porous oxide.

Abstract: An amperometric electrochemical gas sensor includes a permanent electrical resistance means disposed between two electrodes, one of which is the working electrode, the electrical resistance means having an electrical resistance of between about 10 &OHgr; and 200 k&OHgr;. This resistance means provides a permanent shorting link between the electrodes, and constantly maintains the sensor in a ready-to-work condition.

Abstract: A docking station for use with an environmental monitoring instrument to provide predictive diagnostic information. The docking station is connected, typically via the Internet, to a remote service center, and exposure data, calibration data and diagnostic data are communicated from the instrument to the docking station and from the docking station to the service center. Mathematical analysis of the collected data from all available sources is performed at the service center and predictive warnings are generated to alert the users of potential instrument faults, thus allowing preemptive maintenance. The analysis methods include principle component analysis and other statistical methods, fuzzy logic and neural networks. This docking station can be used with monitoring instruments for water quality, pollution control, indoor air quality and breathing air quality.

Abstract: A method for identifying an unknown gas using a diffusion limited sensor providing an electrical signal output when exposed to the gas. According to the method, a sensor is disposed in a chamber of fixed volume and having a gas input and gas output through which the gas flows, and the chamber is connected to a source of a known test gas of known concentration and known diffusion coefficient Dk. The input to the chamber is opened, causing the sensor to be exposed to the known test gas until a steady state electrical signal output from the sensor is obtained. The time Tk necessary for the sensor to attain a predetermined percentage of the steady state output is determined. The chamber is then connected to a source of unknown gas, and the input is opened, and time Tu necessary for the sensor to attain the predetermined percentage of a steady state output for the unknown gas is determined.

Abstract: A method and apparatus for determining the operating condition of a gas sensor apparatus including an amperometric electrochemical sensor operating normally in a potentiostat mode. By coating the sensor with a conductive coating or by varying one or more operating conditions, a response of the sensor can be determined and compared with sensor response while operating normally. This testing enables abnormalities in sensor operation to be determined, and failure of the sensor to be predicted.

Abstract: Method and apparatus for determining the concentration of an analyte gas using a gas measurement device comprising a gas sensing element having an electrical current output dependent upon concentration of a gas being measured, means for measuring the electrical output signal and means for limiting diffusion of the gas being measured to the gas measurement device and defining a path for gas being measured to enter the gas measurement device. Concentration is determined by exposing the gas sensing element to the analyte gas at a first rate of diffusion and diffusivity, and measuring the output signal for a time sufficient to establish a first steady state signal, reducing diffusion of gas to the gas sensing element to a second rate of diffusion and diffusivity, and measuring the output signal for a time sufficient to establish a second steady state signal, and calculating the concentration of the analyte gas based on the second diffusivity and the first and second steady state output signals.

Abstract: A method for identifying an unknown gas using a diffusion limited sensor providing an electrical signal output when exposed to the gas. According to the method, a sensor is disposed in a chamber of fixed volume and having a gas input and gas output through which the gas flows, and the chamber is connected to a source of a known test gas of known concentration and known diffusion coefficient Dk. The input to the chamber is opened, causing the sensor to be exposed to the known test gas until a steady state electrical signal output from the sensor is obtained. The time Tk necessary for the sensor to attain a predetermined percentage of the steady state output is determined. The chamber is then connected to a source of unknown gas, and the input is opened, and time Tu necessary for the sensor to attain the predetermined percentage of a steady state output for the unknown gas is determined.

Abstract: A filter for reducing the cross-sensitivity of a chlorine dioxide detector to hydrogen sulfide. The filter includes a high surface area substrate impregnated with a silver (I) salt or copper (II) salt which is effective to remove hydrogen sulfide from a gas stream without producing undesirable compounds which might be detected by the sensor. The preferred compounds are copper chloride (CuCl2), copper bromide (CuBr2), silver acetate (AgO2CCH3), silver bromate (AgBrO3), silver bromide (AgBr), silver carbonate (Ag2CO3), silver chloride (AgCl), silver chromate (Ag2CrO4), silver cyanide (AgCN), silver iodate (AgIO3), silver oxide (Ag2O), silver perchlorate (AgClO4), silver permanganate (AgMnO4), silver sulfate (Ag2SO4), silver hexafluorophosphate (AgPF6), silver fluoride (AgF), silver tetrafluoroborate (AgBF4), silver iodide (AgI) and silver trifluoromethane sulfonate (AgO3SCF3).

Abstract: A method and apparatus for identifying an unknown reactive gas in a carrier gas, utilizing a sensor with a diffusion limited inlet. After a signal is established for the carrier gas, a flow of the mixture of carrier gas and reactive gas is passed to the sensor and a steady state signal S is established. Then, the input to and output from the sensor are closed, and the steady state signal decays as a known volume of reactive gas is consumed. The decay curve of the signal is integrated to produce an integrated response .SIGMA., and the ratio S/.SIGMA. is proportional to the diffusion coefficient for the reactive gas. By comparing this ratio to the ratio for a known reactive gas, the identity of the unknown reactive gas can be determined.

Abstract: A method by which an oxygen measuring instrument can test the functionality of the oxygen sensor. Oxygen sensors of the galvanic type operate by consumption of an internal easily oxidizable anode, such as lead or cadmium. Failure of the sensor due to complete consumption of all of the anode material, such that the oxygen sensor is no longer able to detect oxygen, is often rapid with little warning. This invention describes an electrical test, which may be performed in-situ on the oxygen sensor by the instrument, which provides a means for detection of an imminent failure, while the sensor is still operational.