Abstract: Methods for using modified single wall carbon nanotubes (“SWCNTs”) to detect presence and/or concentration of a gas component, such as a halogen (e.g., Cl2), hydrogen halides (e.g., HCl), a hydrocarbon (e.g., CnH2n+2), an alcohol, an aldehyde or a ketone, to which an unmodified SWCNT is substantially non-reactive. In a first embodiment, a connected network of SWCNTs is coated with a selected polymer, such as chlorosulfonated polyethylene, hydroxypropyl cellulose, polystyrene and/or polyvinylalcohol, and change in an electrical parameter or response value (e.g., conductance, current, voltage difference or resistance) of the coated versus uncoated SWCNT networks is analyzed. In a second embodiment, the network is doped with a transition element, such as Pd, Pt, Rh, Ir, Ru, Os and/or Au, and change in an electrical parameter value is again analyzed. The parameter change value depends monotonically, not necessarily linearly, upon concentration of the gas component.

Abstract: A heating module for an oxygen sensor comprises an estimated mass module, a cumulative mass module, and a temperature control module. The estimated mass module determines an estimated mass of intake air to remove condensation from an exhaust system after startup of an engine. The cumulative mass module determines a cumulative mass of intake air after the engine startup. The temperature control module adjusts a temperature of an oxygen sensor measuring oxygen in the exhaust system to a first predetermined temperature after the engine startup and adjusts the temperature to a second predetermined temperature when the cumulative air mass is greater than the estimated air mass, wherein the second predetermined temperature is greater than the first predetermined temperature.

Abstract: A method of adjusting the output of an electrochemical sensor including a working electrode and a counter electrode, includes: electronically causing a current flow between the working electrode and the counter electrode via an electrolyte without introducing a test analyte to the electrochemical sensor; measuring a response of the sensor to the current demand resulting from the electronically generated current flow; and using the measured response to adjust the sensor output during sampling of an analyte gas.

Abstract: A chemical agent detector with a a lesser demand sensor, a greater demand sensor, an inlet; and a manifold; and methods associated therewith. The manifold is positioned between the inlet and the sensors, and includes a first intake associated with the lesser demand sensor, a second intake associated with a greater demand sensor, and at least one restrictor. The first intake is placed closer to the inlet than the second intake, and the second intake is isolated from the inlet by at least one restrictor within the manifold. The intakes and restrictor are sized and positioned such that the ratio between: the conductance of the path from the inlet to the greater demand sensor to the conductance of the path between the sensors effectively isolates the lesser demand sensor from the effects of the greater demand sensor.

Abstract: Systems and methods are disclosed that include adjusting a pressure level of a sample gas in a testing chamber, for example, using a pressurized inert reference gas, and determining a composition of the adjusted sample gas. By adjusting the pressure level of the sample gas, the composition of the sample gas may be determined more accurately than otherwise possible. Numerous other aspects are disclosed.

Abstract: A differential absorption spectrum for a reactive gas in a gas mixture can be generated for sample absorption data by subtracting background absorption data set from the sample absorption data. The background absorption data can be characteristic of absorption characteristics of the background composition in a laser light scan range that includes a target wavelength. The differential absorption spectrum can be converted to a measured concentration of the reactive gas using calibration data. A determination can be made whether the background composition has substantially changed relative to the background absorption data, and new background absorption data can be used if the background composition has substantially changed. Related systems, apparatus, methods, and/or articles are also described.

Abstract: Methods for using modified single wall carbon nanotubes (“SWCNTs”) to detect presence and/or concentration of a gas component, such as a halogen (e.g., Cl2), hydrogen halides (e.g., HCl), a hydrocarbon (e.g., CnH2n+2), an alcohol, an aldehyde or a ketone, to which an unmodified SWCNT is substantially non-reactive. In a first embodiment, a connected network of SWCNTs is coated with a selected polymer, such as chlorosulfonated polyethylene, hydroxypropyl cellulose, polystyrene and/or polyvinylalcohol, and change in an electrical parameter or response value (e.g., conductance, current, voltage difference or resistance) of the coated versus uncoated SWCNT networks is analyzed. In a second embodiment, the network is doped with a transition element, such as Pd, Pt, Rh, Ir, Ru, Os and/or Au, and change in an electrical parameter value is again analyzed. The parameter change value depends monotonically, not necessarily linearly, upon concentration of the gas component.

Abstract: Systems and methods are disclosed that include adjusting a pressure level of a sample gas in a testing chamber, for example, using a pressurized inert reference gas, and determining a composition of the adjusted sample gas. By adjusting the pressure level of the sample gas, the composition of the sample gas may be determined more accurately than otherwise possible. Numerous other aspects are disclosed.

Abstract: An assembly and method for gas analysis. The assembly comprises a catalyst compartment for catalytically reacting a component of a gas sample, producing one or more gas species as products. A product compartment receives the gas species, and a sensing element within the compartment senses the amount of one or more of the gas species. This amount is compared to the amount of the same gas species present in a reference compartment containing a non-catalyzed gas sample, providing the amount of the gas species produced by catalysis. Using this value, the content of the gas component in the gas sample is calculated based upon the stoichiometry of the catalyzed reaction. In preferred embodiments, the gas for analysis is a process gas for fuel production, and the catalyst is a high temperature shift catalyst that catalyzes the reaction of carbon monoxide and water into hydrogen and carbon dioxide.

Abstract: A method of analyzing a gas specimen mixture includes measuring the concentrations of inert components in the gas specimen mixture and the pressure and temperature of the gas specimen mixture. A number of sample gas mixtures are generated with varying percentages of hydrocarbon gases, each including the measured inert component concentrations. For each generated sample gas mixture, the method includes calculating the speed of sound therein based on the measured pressure and temperature and the particular percentages of hydrocarbon gases therein, measuring the speed of sound in the gas specimen mixture, and iteratively comparing the measured speed of sound with the calculated speed of sound in different sample gas mixtures until convergence for a particular sample gas mixture. The molecular weight of the particular sample gas mixture is calculated, and set the molecular weight of the gas specimen mixture to the calculated molecular weight.

Abstract: A gas specimen mixture analysis system includes at least one sensor for measuring the concentrations of inert components in the gas specimen mixture, a pressure sensor for measuring the pressure of the gas specimen mixture, and a temperature sensor for measuring the temperature of the gas specimen mixture. A subsystem measures the speed of sound in the gas specimen mixture, and a processing subsystem, responsive to the at least one inert component sensor, the pressure sensor, the temperature sensor, and the subsystem for measuring the speed of sound, is configured to generate a number of sample gas mixtures with varying percentages of hydrocarbon gases, each including the measured inert component concentrations.

Abstract: A method includes acquiring a chemical sample and modulating the chemical sample at a frequency greater than a drift frequency of a sensor. The method also includes determining at least one of a presence and a concentration of the analyte within the modulated chemical sample using the sensor. Modulating the chemical sample could include alternately absorbing at least some of the analyte into a sorbent material and releasing at least some of the analyte from the sorbent material. Modulating the chemical sample could also include heating the sorbent material, absorbing part of the analyte into the sorbent material, and passing a remaining portion of the analyte into the sensor. Modulating the chemical sample could further include stopping the heating of the sorbent material, releasing the part of the analyte from the sorbent material, and passing the sample with the released part of the analyte into the sensor.

Abstract: A differential absorption spectrum for a reactive gas in a gas mixture can be generated for sample absorption data by subtracting background absorption data set from the sample absorption data. The background absorption data can be characteristic of absorption characteristics of the background composition in a laser light scan range that includes a target wavelength. The differential absorption spectrum can be converted to a measured concentration of the reactive gas using calibration data. A determination can be made whether the background composition has substantially changed relative to the background absorption data, and new background absorption data can be used if the background composition has substantially changed. Related systems, apparatus, methods, and/or articles are also described.

Abstract: A System and Method for Gas Recognition by Analysis of Bispectrum Functions is based on the Higher-Order Spectral analysis of time series measurements of resistance fluctuations in Metal Oxide Semiconductor (MOS) gas sensors, such as Taguchi-type sensors. A two-dimensional contour plot module of the bispectrum function is treated as a pattern. These patterns include information about the analyte(s) whereby characteristics of the gas can be identified.

Abstract: A sensor system having an analyte modulator, detector and a pump. The concentration of an analyte sample may be modulated at one time constant. The detector may have an output with a drift at another time constant. The one time constant may be shorter than the latter time constant. The latter time constant may be substantially removed from the detector output with a discriminator. A reservoir may receive high concentrations of analyte from the modulator, before analyte is forwarded to the detector and pump via analyte conveyance lines and valving. The modulation or pre-concentration of analyte in the sensor system may entail shorter times and smaller volumes than those needed by the detector. Such mismatches may be alleviated via accumulation of analyte in the reservoir prior to being forwarded to the detector.

Abstract: An analysis method for a substrate processing apparatus capable of accurately detecting a state in a housing chamber. Emission intensities of processing gas before being introduced into the chamber and processing gas having passed therethrough are measured before an inter-chamber part is replaced. If an emission intensity measured after the replacement coincides with that measured before the replacement, an emission intensity of the processing gas having passed through the chamber is measured, and a variation between the emission intensities of the processing gas having passed through the chamber measured before and after the replacement is calculated. After start of plasma processing on wafers, an emission intensity of the processing gas having passed through the chamber is measured and the variation is removed therefrom to calculate an emission intensity really representing a state in the chamber, thus detecting an end point of plasma processing therefrom.

Abstract: A highly accurate gas sensor includes a circuit having an improved S/N ratio. First ends of a heat generating element and reference resistor brought into contact with a detected gas are commonly connected, and second ends are respectively connected to a first switch. The first switch is connected with a power source apparatus for supplying a current to the heat generating element or reference resistor. A voltage measuring portion measures a voltage across the heat generating element or reference resistor. An operating portion switches the first switch between the reference resistor and heat generating element by a predetermined timing by determining a condition of controlling a power source apparatus for supplying at least 3 stages of step-like currents to the heat generating element from the voltage across the reference resistor. A voltage measuring portion measures the voltage across the heat generating element and calculates a concentration of a detected gas.

Abstract: A distributed analysis system may include at least one analysis instrument for generating sample data from a sample at a local site. A storage device may hold a library of calibration models at a site remote from the local site). A data processor, which may be integral with or separate from the analysis instrument, may determine a trait of the sample using a calibration model selected from the library and the sample data. The data processor may be located at the local site and may be connectable to the storage device via a telecommunications link. The data processor may temporarily retain the selected calibration model received via the telecommunications link.

Abstract: The invention relates to a leak detector including a hand-held device with a sniffer tip. A distance detector for detecting a defined distance of the sniffer tip from the test object is provided on the sniffer tip. A test is only initiated if the distance between the sniffer tip and the test object is correct, thereby avoiding measuring errors due to wrong manual positioning of the sniffer probe. The leak detector can also be provided with an acceleration detector, which permits the test to be carried out only if the sniffer probe is kept steady.

Abstract: An exhaust emission analysis system is provided that includes an exhaust and dilution gas source respectively providing exhaust and dilution gases. A dilution unit includes exhaust and dilution gas mass flow controllers, fluidly connected to the exhaust and dilution gas sources. The mass flow controllers define a gas flow rate of gas from their respective gas source. A connection mixes the gases to provide a diluted exhaust gas having an incorrect dilution ratio. A water measurement device measures the water content of the exhaust gas. A water content dilution signal is sent from the water measurement device to a control device. An adjustment factor is calculated by the controller and a flow rate command signal is sent from the controller, to the exhaust gas mass flow controller to adjust the gas flow rate of the exhaust gas and provide a corrected dilution ratio at the connection.

Abstract: The invention concerns a procedure to determine a mass of particles or a particle mass flow in an exhaust gas system of an internal combustion engine, whereby at least one resistive particle sensor is disposed in the exhaust gas system of the internal combustion engine. The measured signal change of the particle sensor is compared with a predicted signal change of the particle sensor ascertained from an engine model. If the measured signal change of the particle sensor and/or the predicted signal change of the particle sensor are corrected while taking into account the influencing variables on the transverse sensitivities of the particle sensor, it is possible when ascertaining the predicted signal change of the particle sensor that a compensation for the transverse sensibilities can result even during dynamic operating point changes of the internal combustion engine, which occur faster than the actuation of the particle sensor.

Abstract: A single chip wireless sensor (1) comprises a microcontroller (2) connected to a transmit/receive interface (3), which is coupled to a wireless antenna (4) by an L-C matching circuit. The sensor (1) senses gas or humidity and temperature. The device (1) is an integrated chip manufactured in a single process in which both the electronics and sensor components are manufactured using standard CMOS processing techniques, applied to achieve both electronic and sensing components in an integrated process. A Low-K material (57) with an organic polymer component is spun onto the wafer to form a top layer incorporating also sensing electrodes (60). This material is cured at 300° C., which is much lower than CVD temperatures. The polyimide when cured becomes thermoset, and the lower mass-to-volume ratio resulting in K, its dielectric constant, reducing to 2.9. The thermoset dielectric, while not regarded as porous in the conventional sense, has sufficient free space volume to admit enough gas or humidity for sensing.

Abstract: A gas sensor control device for controlling a gas sensor, the gas sensor including a gas sensor element that includes a cell including a pair of electrodes and a solid electrolyte, the gas sensor control device including a circuit board connectable to the gas sensor. The circuit board has mounted thereon a voltage control unit mounted on the circuit board and configured to control a voltage developed across a pair of electrodes of the cell to a constant voltage; a temperature detecting unit mounted on the circuit board and configured to detect a temperature of the circuit board; and a voltage correcting unit mounted on the circuit board and configured to apply a correction voltage to the voltage control unit compensating for a temperature-dependent variation in the constant voltage based on the temperature detected by the temperature detecting unit.

Abstract: A System and Method of Molecule Counting Using Fluctuation Enhanced Sensors includes processes for improved chemical analyte detection and quantification through the measurement and generation of an amplitude density histogram of the measured time series of frequency fluctuations in the instantaneous frequency of a chemical sensor arranged to produce an oscillatory output signal when exposed to chemical substances. The system and method may use a chemical sensor, such as a surface acoustic wave (SAW) device. Statistical analysis produces the amplitude density of the frequency fluctuations, which are represented as a pattern that includes information about the quantity of the analyte on the surface of the sensor. Patterns in the measured amplitude density are then correlated to theoretical amplitude density functions in order to determine the number of analyte molecules on the surface of the sensor.

Abstract: A gas sensor assembly comprising a gas-sensitive element, and a first pulse modulation circuit comprising a first switching device is disclosed. The gas-sensitive element and the first switching device are arranged in series with a power supply. The first pulse modulation circuit further comprises a first control module adapted to control the first switching device in accordance with a monitored parameter of the gas-sensitive element, the parameter varying with the temperature of the element, thereby controlling the power consumed from the power supply by the gas-sensitive element.

Abstract: A solid electrolyte body is placed on and fixed to an upper plate of a press jig such that a major surface (an upper surface) of the solid electrolyte body faces one major surface of a guide plate having a through-hole. The upper plate is rotated by a transfer mechanism to incline the solid electrolyte body in one direction, and the inclined solid electrolyte body is moved toward the other major surface of the guide plate such that a first edge of the solid electrolyte body protrudes from the through-hole. Then, a cutter is slid along the other major surface, so that the first edge is chamfered to form a first chamfered portion.

Abstract: The present description relates to a process for measuring outgas emissions in fabrication chambers used for semiconductors, micromachines and the like. In one embodiment, the invention includes inserting a gas adsorption material into a processing chamber exhaust vent, running a process in the chamber, venting gasses in the chamber through the gas adsorption material, removing the adsorption material from the exhaust vent, and analyzing the adsorption material for gases.

Abstract: A method and system are disclosed for compensating a mass air flow signal produced by a mass air flow sensor in fluid communication with an air intake passageway of an internal combustion engine. A mass air flow signal produced by the mass air flow sensor is monitored and an expected oxygen concentration of exhaust gas produced by the engine is determined. A compensation parameter is determined as a function of the expected oxygen concentration and a measured value of the oxygen concentration of the exhaust gas. A compensated mass air flow value is determined as a function of the mass air flow signal and the compensation parameter.

Abstract: A gas sensor assembly detects the presence of a constituent in a first gas stream. The assembly comprises: (a) a flexible circuit having a pair of oppositely-facing surfaces, (b) a sensor mounted on one surface of the flex circuit, the sensor electrically connected to conductors in the flex circuit, and (c) a channel for directing a second gas stream across the flex circuit surface facing away from the sensor, the channel formed at least in part by the flex circuit surface facing away from the sensor. The first and second gas streams can be derived from a common gas stream. In operation, thermal conductivity between the sensor and neighboring heat-conducting structures components is reduced, thereby reducing sensor electric power consumption.

Abstract: An analysis method for a substrate processing apparatus capable of accurately detecting a state in a housing chamber. Emission intensities of processing gas before being introduced into the chamber and processing gas having passed therethrough are measured before an inter-chamber part is replaced. If an emission intensity measured after the replacement coincides with that measured before the replacement, an emission intensity of the processing gas having passed through the chamber is measured, and a variation between the emission intensities of the processing gas having passed through the chamber measured before and after the replacement is calculated. After start of plasma processing on wafers, an emission intensity of the processing gas having passed through the chamber is measured and the variation is removed therefrom to calculate an emission intensity really representing a state in the chamber, thus detecting an end point of plasma processing therefrom.

Abstract: A system and method is provided for obtaining calibration curves for CO and CO2 during laboratory calibration of one or more remote emissions sensing (RES) instruments, and for self-calibration of on-road RES instruments to compensate for changes in background CO and CO2 column densities.

Abstract: A humidity sensor capable of self-regulating temperature compensation and a manufacturing method thereof overcomes the inaccuracy caused by the resistor value of a conventional humidity-sensitive element changing depending due to changes in the temperature. The present invention proposes disposing two different humidity-sensitive elements in a humidity-sensitive substrate, wherein one humidity-sensitive element includes a saturated salt solution. The humidity-sensitive substrate has two different humidity-sensitive elements for achieving a self-regulating temperature compensation feature. The present invention of the humidity-sensitive element having the saturated salt solution can maintain the amount of humidity in the air regardless of the temperature.

Abstract: A method and apparatus for determining the quantities of pollutants in the exhaust gases of internal combustion engines wherein an essentially constant and fully conditioned quantity of humidity and/or temperature-conditioned combustion gas is supplied to the internal combustion engine at each instant whose quantity corresponds to at least the maximum quantity required by the respective combustion engine, wherein the exhaust gas is diluted with the quantity of combustion gas not used by the combustion engine, and then tested relative to quantities of pollutants and flow rate.

Abstract: A degradation diagnosis method for simply performing degradation diagnosis of a gas sensor such as a hydrogen sensor. The hydrogen sensor has a reference detector member and common detector member, with each detector member respectively constituted of a detector element and temperature compensating element that form a pair. Power is normally supplied to the common detector member, which performs concentration detection of the hydrogen gas. When performing degradation diagnosis of this common detector member, concentration detection is performed simultaneously by each detector member for the gas of the prescribed hydrogen concentration by supplying power to both the common detector member and reference detector member and comparing the output value of the common detector member and the output value of the reference detector member.

Abstract: A gas detector with a compensated electrochemical sensor exhibits altered sensitivity in response to decreasing sensitivity relative to both gas exposure and non-gas exposure. A sensitivity adjustment can be established in response thereto.

Abstract: Disclosed is a gas measuring device which comprises compensation of disturbances and offers high accuracy of measurement immediately after being activated. Said gas measuring device is provided with a gas sensor (1) for generating a measuring signal (S1) that depends on the gas concentration and can have a spurious component while a high-pass filter (13) having an adjustable limiting frequency is mounted downstream of said gas sensor (1). The limiting frequency can be predefined according to the spurious component by means of a selection unit.

Abstract: The method of detecting the hydrogen concentration by using a first heat-generating resistor of which a first electrophysical quantity varies depending upon the hydrogen concentration and a second heat-generating resistor which is neighboring said first heat-generating resistor in a direction of gas flow and of which a second electrophysical quantity varies depending upon the hydrogen concentration as does the first electrophysical quantity, to detect the concentration of hydrogen based on the first electrophysical quantity and the second electrophysical quantity, the method comprising: calculating the amount of change in a target physical quantity, which is either the first electrophysical quantity or the second electrophysical quantity, calculating the correction amount based on a difference between the first electrophysical quantity and the second electrophysical quantity, and a calculating the concentration of hydrogen based on a difference between the amount of change in the target physical quantity and

Abstract: An improved engine control system using a NOx sensor is disclosed. In one example, the NOx sensor structure and/or signals are modified to improve distance transmission of NOx sensor output signals so that at least some processing electronics can be relocated remote to the sensor and in an engine control unit, or other such control unit utilizing the NOx sensor signals, and controlling the NOx sensor heaters, if applicable.

Abstract: When the ignition switch of a vehicle is turned OFF, a purging process for increasing the flow of an off-gas fluidizing in each of the outlet side pipings of a fuel cell and discharging water remaining in a fuel cell system to an outside is started to be executed, and the amount of current conductance to the heater of the gas sensor is increased synchronously with the start of the execution of the purging process. With the completion of the purging process, the fluidization of the off-gas in each of the outlet side pipings stops, and the amount of current conductance to each of the units of the gas sensor (for example, an electrifying voltage) is gradually decreased depending on a predetermined current conductance reducing amount which is preset, thereby stopping the current conductance to each of the units and the amount of current conductance to the heater is gradually decreased, thereby stopping the current conductance to the heater.

Abstract: An engine diagnostic system for use with an internal combustion engine coupled to a lean NOx trap with a NOx sensor coupled downstream of the trap. Degradation of the NOx sensor is determined by estimated NOx exiting the trap based on engine out NOx and various other operating conditions. When the difference between the measured NOx and estimated NOx is greater than a predetermined value for a predetermined duration, degradation is indicated.

Abstract: An apparatus and method for purging and zeroing an analyzer. At times, for good analysis of a gas sample or taking a live reading, the analyzer needs to be zero out and/or purge of contaminants. The analyzer can take a live reading, purge and/or zero in any order. The purge function and zero function can automatically be done before, during or after taking a live reading.

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: A sensing system includes a ring oscillator that emits electromagnetic radiation at a characteristic frequency. The ring oscillator comprises an odd number plurality of inverters that are electrically connected in series. The sensing system also comprises a temperature stabilized voltage source that is used to supply voltage to the inverters of the ring oscillator. A sensing load for sensing a change in a preselected environmental condition is operably connected to the ring oscillator. When the load senses the preselected environmental condition, the sensing load alters the characteristic frequency of the ring oscillator and hence the electromagnetic radiation as emitted by the ring oscillator. A pick-up antenna receives the electromagnetic radiation as emitted by the ring oscillator and detection electronics, operably coupled to the pick-up antenna, measure the frequency of the electromagnetic radiation as received by the pick-up antenna.

Abstract: The self-calibrating carbon monoxide detector and method of the present invention utilize the gas for which the detector was designed to detect as the calibration gas. Specifically, a carbon monoxide gas generator is included in the detector assembly, and is controller to produce a known amount of CO. The sensor response to the quantity of CO generated is monitored, and the calibration thereof adjusted as necessary. The operation of the gas generator is also monitored, and any failures are flagged for user attention. The gas generator specifically suppresses the generation of hydrogen through the materials used in its construction. Temperature effects may also be compensated either through control of gas generation control parameters or compensation of the sensor output in view of the generator temperature effects.

Abstract: An A/F signal proportional to an oxygen concentration in the exhaust gas from an internal combustion engine is output upon application of a voltage based on an instruction from a microcomputer. At the time an element resistance is detected, a bias instruction signal Vr from the microcomputer is converted by a D/A converter 21 to an analog signal Vb. An output voltage Vc obtained by removing high frequency components from the analog signal Vb through an LPF 22 is input to a bias control circuit 40. During this time period in which the element resistance is detected, an accurate A/F signal is not output. Therefore, the A/F signal that has theretofore prevailed is held by a Sample/Hold circuit 70 to thereby prevent the use of an erroneous A/F signal. Namely, at the time of detecting the element resistance, the detected value of the oxygen concentration is prevented from becoming abnormal. As a result, an accurate A/F control can be executed using the detected element resistance.

Abstract: A carbon dioxide gas measurement and control system and method which comprises a thermal conductivity absolute humidity sensor which measures carbon dioxide during dynamic temperature and humidity changes by isolating the particular sensor response for absolute humidity and temperature, i.e., Vm(D,T) in order to track carbon dioxide concentration.

Abstract: A sensor for the measurement of carbon dioxide concentration within an air flow being input to a measuring cell (1) connected to at least one electroacoustic element (2, 3) for transmitting and receiving airborne acoustic waves within the measuring cell (1). The output signal of the sensor corresponds to the propagation velocity of these waves and an indirect measure of carbon dioxide concentration, with an automatic offset correction functionality for compensation of undesired offset variations of the signal, caused by temperature or humidity variations. Preferably, an accumulating function for minimizing the influence of the offset variations is included, which for humidity variations may consist of a material with high porosity and surface density of polar molecular groups. Temperature control of the inner sheath (4) is effected by a temperature sensor (11), a resistive heating element (12) in good thermal contact with the inner sheath (4), and a control circuit (13).

Abstract: An exhaust emission analysis system is provided that includes an exhaust and dilution gas source respectively providing exhaust and dilution gases. A dilution unit includes exhaust and dilution gas flow devices, such as mass flow controllers, fluidly connected to the exhaust and dilution gas sources, respectively. The metering device in the mass flow controllers defines a gas flow rate of gas from its respective gas source. The gas flow devices are fluidly connected at a connection that mixes the gases to provide a diluted exhaust gas having an incorrect dilution ratio. A water measurement device such as an analyzer measures the water content of the exhaust gas, preferably subsequent to dilution. A water content dilution signal corresponding to the water content in the exhaust gas is sent from the water measurement device to a control device.

Abstract: An apparatus and method for measuring the vapor or gas content of a vacuum chamber (1) by a vapor sensor (21) located in the fore-line of a vacuum system is provide. The gas or vapor content is determined by first providing a zero condition for the sensor using the vacuum pump (25) and them referencing the sensor response to the chamber gas during the evacuation cycle.

Abstract: A sensor for the measurement of carbon dioxide concentration within an air flow being input to a measuring cell (1) connected to at least one electroacoustic element (2, 3) for transmitting and receiving airborne acoustic waves within the measuring cell (1). The output signal of the sensor corresponds to the propagation velocity of these waves and an indirect measure of carbon dioxide concentration, with an automatic offset correction functionality for compensation of undesired offset variations of the signal, caused by temperature or humidity variations. Preferably, an accumulating function for minimizing the influence of the offset variations is included, which for humidity variations may consist of a material with high porosity and surface density of polar molecular groups. Temperature control of the inner sheath (4) is effected by a temperature sensor (11), a resistive heating element (12) in good thermal contact with the inner sheath (4), and a control circuit (13).