Abstract: A method for measuring hydrogen concentration in a gas includes exposing a PdNi alloy thin-film gas sensor to the gas, alternately controlling the temperature of the PdNi alloy thin-film gas sensor between a first temperature for a first period of time and a second temperature for a second period of time while the PdNi alloy thin-film sensor is exposed to the gas, continuously monitoring the resistance of the PdNi alloy thin-film gas sensor during the first and second periods of time, and calculating the hydrogen concentration as a function of a transient in the resistance of the PdNi alloy thin-film sensor measured at a time that the temperature transitions between the first temperature and the second temperature.

Abstract: A method for measuring hydrogen concentration in a gas includes exposing a PdNi alloy thin-film gas sensor to the gas, alternately controlling the temperature of the PdNi alloy thin-film gas sensor between a first temperature for a first period of time and a second temperature for a second period of time while the PdNi alloy thin-film sensor is exposed to the gas, continuously monitoring the resistance of the PdNi alloy thin-film gas sensor during the first and second periods of time, and calculating the hydrogen concentration as a function of a transient in the resistance of the PdNi alloy thin-film sensor measured at a time that the temperature transitions between the first temperature and the second temperature.

Abstract: A method can be performed by adjusting a temperature of a gas sensor to a first temperature value for a first period of time and a second temperature value for a second period of time. The gas sensor signal may be measured during the first period of time to determine a first signal value and during the second period of time to determine a second value. Then, concentration information for at least one gas is calculated according to the first signal value and the second signal value. While the gas sensor signal may include information about a presence of a first gas and a second gas, the concentration information for the at least one gas may not substantially include concentration information for the second gas.

Abstract: A method can be performed by adjusting a temperature of a gas sensor to a first temperature value for a first period of time and a second temperature value for a second period of time. The gas sensor signal may be measured during the first period of time to determine a first signal value and during the second period of time to determine a second value. Then, concentration information for at least one gas is calculated according to the first signal value and the second signal value. While the gas sensor signal may include information about a presence of a first gas and a second gas, the concentration information for the at least one gas may not substantially include concentration information for the second gas.

Abstract: A temperature of a gas sensor may be adjusted to a first temperature value for a first period of time and a second temperature value for a second period of time. A signal of the gas sensor may be measured during the first period of time to determine a first signal value and during the second period of time to determine a second value. Then, concentration information for at least one gas is calculated according to the first signal value and the second signal value. While the gas sensor signal may include information about a presence of a first gas and a second gas, the concentration information for the at least one gas may not substantially include concentration information for the second gas.

Abstract: Amperometric electrochemical sensors for detection of an analyte gas in air are disclosed. The sensors can be used in a gas detector to detect the analyte gas and to compensate for the relative humidity and temperature of the air. In addition, an electrochemical sensor having high surface area electrodes, and an increased sensitivity, is disclosed.

Abstract: A biosensor comprising a substrate material, at least one antibody covalently immobilized on the substrate material, and a pair of metal contact electrodes for measuring the impedance of the biosensor. A process for producing a biosensor in accordance with this invention as well as a process for utilizing the biosensor are also disclosed.

Abstract: Apparatus for the detection of a vapor of a selected chemical substance includes a sensor whose impedance changes upon exposure to such a vapor. The sensor comprises a polymer whose physical structure is altered by the vapor, e.g., through expansion or disintegration, and electrically conductive elements that are interspersed with or separated by the polymer. The interspersed elements may consist of a fine powder of carbon or of a metal in a matrix of silicone or other vapor-sensitive polymer. The electrical contacts between the powder particles are weakened when the polymer swells or disintegrates, which results in increased resistance. Alternatively, the capacitance between two conductive layers separated by a polymer layer decreases, and hence the impedance increases, when the polymer swells upon exposure to the vapor. In yet another embodiment, the polymer exerts a stress on a piezoresistive element and the stress is increased when the polymer swells, which causes a further increase in resistance.

Abstract: Apparatus for detecting the presence of a gas in an ambient atmosphere comprises a multiple quantum well structure; a thin mesh of a transition metal formed on the multiple quantum well structure; and an arrangement for monitoring transmission of electromagnetic radiation through the mesh and the multiple quantum well structure.

Abstract: An optical waveguide sensor for the detection of acid vapors comprises a chemically sensitive reagent coating of bromothymol blue or thymol blue indicator suspended in a Nafion polymer film. The sensor uses a 562-nm light-emitting diode source and a phototransistor detector. The response to HCl and H.sub.2 S vapors is both rapid and reversible, with an estimated detection limit for H.sub.2 S of less than 15 ppmv (parts per million by volume). The sensor exhibits generalized response to protonic acid vapors, but does not produce an indicator response to CO.sub.2, even at large concentrations (60 volume-%) in the presence of water vapor. The sensor exhibits a systematic interference from water vapor which may be corrected by a differential approach, either using a reference sensor (Nafion without an indicator) or by monitoring the sensor responses at two wavelengths.

Abstract: A circuit and a method for measuring a quantity influencing the capacitance-voltage characteristic of a capacitive element, the measuring accuracy and the signal-to-noise-ratio being improved by determining such quantity on the basis of the area under the curve of the capacitance-voltage characteristic.

Abstract: A micro-amperometric electrochemical sensor for detecting the presence of a pre-determined species in a fluid material is disclosed. The sensor includes a smooth substrate having a thin coating of solid electrolytic material deposited thereon. The working and counter electrodes are deposited on the surface of the solid electrolytic material and adhere thereto. Electrical leads connect the working and counter electrodes to a potential source and an apparatus for measuring the change in an electrical signal caused by the electrochemical oxidation or reduction of the species. Alternatively, the sensor may be fabricated in a sandwich structure and also may be cylindrical, spherical or other shapes.

Abstract: Methods for spin coating electrolytic materials onto substrates are disclosed. More particularly, methods for depositing solid coatings of ion-conducting material onto planar substrates and onto electrodes are disclosed. These spin coating methods are employed to fabricate electrochemical sensors for use in measuring, detecting and quantifying gases and liquids.

Abstract: The open ended wrench includes a manually graspable handle and a nut-seizing jaw formation connected to the handle. The jaw formation has a nut-receiving opening therein defined between an upper jaw member, a lower jaw member spaced a fixed distance from the upper jaw member and a jaw back portion extending between the upper and lower jaw members. A slot communicates with the opening and extends through the jaw back portion. A plurality of substantially equal length shims are longitudinally slidable through the slot from a location outside of the opening to a location inside of the opening to provide a variable dimension for the nut-receiving opening. Each of the shims has an interlock formation for preventing any shim from being located inside of the opening unless there is supportive contact with the jaw.

Abstract: An open-ended wrench is provided in which the jaw and handle are formed as a unitary member with the jaw being offset with respect to the handle. A plurality of shims are longitudinally slidable from a location outside of the jaw to a location inside of the jaw to vary the dimension of the nut-receiving opening defined by the jaw. Interlocking means are provided to prevent one or more of the shims from being located inside the jaw opening unless there is supportive contact with the jaw.