Panametrics, Inc.

Ge Infrastructure Sensing, Inc.

Robert H Hammond

Yu Shen

Yuzef Gokhfeld

Yufeng Huang

S Gregory Tsopelas

Gary Parece

An oxygen sensor has a sensor body formed of a crystalline material, such as zirconia, with first and second electrodes disposed on a single surface thereof. The electrodes are arranged to induce superionic oxygen transport in the body along current paths extending at a shallow depth in the crystalline material at the electrode surface. The electrodes may be interdigitated or juxtaposed porous electrodes that define an exposed surface pattern of ionic conduction for sensing, and the electrodes are preferably poisoned to inhibit cross sensitivity to reactive components, such as hydrogen, that may be present in the environment. The electrodes may effect electrode-limited superionic conduction in a thin slice of single crystal material, or a polycrystalline yttria-stabilized zirconia film sensing body, and operate at a relatively low temperature in the range of 250-400&deg; C., preferably about 300-350&deg; C., with negligible leakage current or cross sensitivity, allowing reliable measurement of oxygen concentrations in the ppb range. The oxygen sensor may be fabricated together with a heater, such as a resistive heating element, deposited on the back face of the sensor body, or the sensor body may be attached to a heater chip. One such heater chip includes both a heating electrode, and a resistive thermal device that may, for example, provide a feedback or control signal for controlling heater temperature in the desired range. The sensors may be lithographically formed in arrays with suitable lead pads, then scored and separated, and mounted on heater chips, providing a self-contained integrated unit of versatile application.

Thin film ppb oxygen sensor

An ultrasonic measurement system performs a signal path measurement by directing ultrasonic signals through a gaseous material in a conduit, and processing the detected signals to determine sound speed and to derive the average molecular weight of an unknown hydrocarbon mixture present in the material. The processor includes a plurality of stored tables of critical constants of hydrocarbon mixtures as a function of the average molecular weight of the mixture, and is configured to iteratively set a hypothetical molecular weight, determine the corresponding critical properties, and compute a predicted sound speed. If the two speeds differ, a new weight is set and the procedure is repeated until the predicted sound speed matches the measured speed, indicating that the current estimate is the correct average molecular weight. Once the processor has determined the critical constants from its stored tables, it applies the virial equation of state and mixing rules to determine the predicted sound speed for each hypothetical molecular weight of an unknown mixture of hydrocarbons present, together with one or more known inorganic components, in the fluid material. The processor may be configured for user input of known quantities of one or more gases such as nitrogen, hydrogen, sulfur dioxide, carbon dioxide or other inorganic or non-hydrocarbon gases present in the conduit. Alternatively, all or some of this data may be provided in an automated manner from suitable signals, settings or measurements from upstream conduits, valves or measurement and control instrumentation.

Ultrasonic measurement system with molecular weight determination

A sensor responds to a magnetic wind produced by the magnetic susceptibility of a target component gas, such as oxygen, which is present together with a background gas in a sample located in a measurement field produced in a measurement device. A background sampler also determines thermal and physical characteristics in a conditioned flow path, and a processor performs a computational correction on the detected magnetic wind signal to more accurately determine the concentration of the target gas. The background sampler includes a mass flow cell in series with a laminar flow device to measure heat capacity and viscous properties of the sample. It derives the gas viscosity from a differential pressure measurement; and preferably determines the heat capacity and thermal conductivity of background gases, the composition of which may be unknown, to compensate for their effects on the magnetic wind sensor elements. A further correction for diamagnetism of the background is made using one or more correlations between the measured parameters in certain common gases or classes of gases. The determination of gas bulk properties allows the concentration of the target gas to be made with enhanced accuracy in the presence of unknown, unquantified or changing background components, and the necessary hardware may be used in conjunction with existing magnetic wind sensor and processor. In that case, the processor program is modified to apply the additional sensor inputs to correct the magnetic wind reading. A thermal conductivity correction is also made, and this may be directly derived from the bridge control signal when operating the magnetic wind sensors in mode to maintain constant temperature. The system may be used in petroleum tanks and hydrocarbon vent systems to monitor for explosive levels of oxygen.

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Cambridge, MA, United States of America

Robert H Hammond