Panametrics, Inc.

General Electric Company

Ge Infrastructure Sensing, Inc.

Yuzef Gokhfeld

Yu Shen

Robert H Hammond

Gary Parece

An apparatus and method to measure combustible gases using a catalytic sensor includes: housing the catalytic sensor in a flow-through chamber isolated from a volume of ambient gas; periodically drawing into the chamber a sample of the ambient gas; burning on the catalytic sensor and in the chamber the combustible gas in the sample of ambient gas, e.g. essentially until the completion of burn out, and measuring the plurality of output signals of the sensor synchronously with the interrupted ambient gas sampling while burning the sample on the catalytic sensor.

Combustible gas detector having flow-through sensor container and method for measuring such gases

A pump for a gas sampling or analyzing system includes a pump body having walls impervious to the gas and an electrical coil within the body. The pump is coupled in series with a gas sensor and a gas volume containing the gas to be sampled or analyzed. By varying the amplitude of either the AC or DC current supplied to the coil, the temperature of the coil and, hence, the temperature of the gas within the pump can be varied, causing the pump to 'inhale' upon lowering the temperature of the gas within the pump and 'exhale' upon raising the temperature of the gas within the pump, thereby enabling the gas from the gas volume to be drawn periodically into and expelled from the sensor for sampling.

Pump for supplying a gas to a sensor and methods therefor

A high sensitivity pressure sensor with long term stability including a housing with first and second chambers, a membrane separating the first and second chambers, a first electrode located in the first chamber and spaced from one side of the membrane forming a first capacitor therewith, and a second electrode located in the second chamber and spaced from an opposite side of the membrane forming a second capacitor therewith. A measuring circuit is connected across the first and second capacitors for measuring membrane displacement by detecting differences in capacitance between the first and second capacitors and a compensation circuit is configured to apply an electric field to the membrane as a compensating force by reducing the voltage difference between the first electrode and the membrane and simultaneously increasing the voltage difference between the second electrode and the membrane or vice versa to provide long term stability. The invention also features a unique compensation circuit for a pressure sensor and a method of making and operating a pressure sensor.

High sensitivity pressure sensor with long term stability

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

A method of moisture measurement wherein a moisture responsive element is subjected to the measuring environment and its thermal capacitance or resistance temperature coefficient is measured. A system operates by cycling a sensor element between a first temperature and a second temperature and determining the sensor capacitance at each temperature. The sensor capacitance difference, corresponding to its temperature coefficient, is then compared to a previously compiled table of gas humidity or dew point versus capacitance increment values. The differential measurement thus made automatically corrects for systemic error originating in equipment drift, cable capacitance change and various aging and slow hysteresis or sensor capacitance variations. In one embodiment, a capacitive type relative humidity sensor is placed in thermal contact with an electric heater, a thermoelectric cooler, or both, and the heater and/or cooler are operated to drive the sensing element from a first temperature to a second temperature, under control of a microprocessor. Depending on the ambient temperature, the device may return to its initial temperature passively, or be actively driven by the heater or cooler, respectively. The frequency or cycle time of these temperature changes is selected to correspond to the time constant of the sensor, which in turn, may be a function of the relative humidity. In illustrative embodiments, a platinum film may be employed as the heater and a Peltier device may be employed as the cooler, and these are driven to change the sensor temperature and effect readings at upper and lower temperatures with time constant or cycle time of approximately 1-3 minutes. Preferably, a fixed cycle time is employed, and capacitance is measured at the upper and lower temperatures of each cycle with the sensor immersed in the sample environment, until the capacitance difference measurement stabilizes. This difference is then compared to a previously compiled table of differences for various dew points. In another embodiment or mode of operation, the thermal source is operated in two cycles or at two different power levels to drive the sensor to a first temperature T.sub.1 away from ambient temperature, and to a second more divergent, temperature T.sub.2. The temperature then returns to T.sub.1 by passive interaction with the surroundings. By identifying the dew point curve by reference to capacitance difference between two fixed temperatures, errors and uncertainty at the high humidity/high temperature range are also reduced. In another embodiment, an occasional differential measurement is performed to detect errors in a set of stored curves and update the tables used for single-point humidity measurements, thus obviating the need for protocols involving reference gases or recalibration.

Humidity sensor with differential thermal detection and method of sensing

A method of humidity measurement wherein a humidity responsive element is subjected to the measuring environment and its temperature coefficient is measured. A system operates a sensor element between a first temperature and a second temperature, determining its temperature coefficient, which is then compared to a previously compiled table. The differential measurement thus made automatically corrects for system error originating in equipment drift, cable capacitance change and various aging and slow hysteresis or sensor capacitance variations. In another embodiment, an occasional differential measurement is performed to detect errors in a set of stored curves and update the tables used for single-point humidity measurements, thus obviating the need for protocols involving reference gases or recalibration.

Growing community of inventors

Waltham, MA, United States of America

Yuzef Gokhfeld