A concentration sensor for at least one given gas comprising at least one suspended structure (2) with respect to a support, said suspended structure (2) being of an electrically conductive material and said structure having a low heat response time, means for biasing said suspended element (2) and means (8) for measuring the variation of the electric voltage at the terminals of the suspended structure (2), the biasing means (6) being formed by an alternating current source the intensity of which heats the suspended structure (2) and the frequency of which gives rise to a phase shift between a signal of the biasing means and a signal measured by the measuring means, and means for determining a phase shift variation due to a gas concentration variation and means for determining the concentration variation of said gas from the phase variation.

For measuring concentrations of fluid-soluble gases with improved drift stability and low production costs, thus dispensing with tedious calibration and/or drift correction routines and re-membraning procedures, a sensor and a system are provided, comprising at least two electrodes, which are covered by sensor fluid at at least one detection site; and an ion-balancing means (50), for example a mixed-bed ion-exchange resin, in contact with the sensor fluid for removing polluting ions.

A chemical sensor (10) is described with at least one layer of a metal oxide (11) arranged between two current injecting electrodes (16,16′) with the length (L) of the layer of a metal oxide between the current injecting electrodes being less than 50 microns and one or a pair of voltage sensing electrodes (17) connected to the layer of a metal oxide (11) with the electrodes (16,16′,17) forming a 3- or 4-terminal arrangement for determining the resistance changes of layer material (11) excluding series resistances such as contact resistances close to or at at least one of the current injecting electrodes (16) from the resistance measurement.

A chemical sensing system includes a substrate material, a detector capable of indicating a presence of a target compound, gas, or vapor, and a heater for rapidly releasing compounds, gases and vapors from the substrate material. The substrate material acts to concentrate the compounds, gases, and vapors from a sample area for improved detection by the detector.

A method of determining an internal volume (V) of a filter or bag device includes pressurizing the device to a first pressure (p.sub.1) lower than a proof pressure by supplying a test gas, pressurizing the device to proof pressure (p.sub.p), and at the same time, measuring the mass flow (m) or the volumetric flow of test gas, determining the gas temperature (T), and determining the internal volume (V) based on the equation for ideal gases, such that: V=m×R×T/(p.sub.p−p.sub.1) where V is the internal volume, m is the mass flow, R is the gas constant, T is the gas temperature, p.sub.p is the proof pressure and p.sub.1 is the first pressure. A computer program product and a testing apparatus for performing the above-mentioned method also are provided.

A method of determining an internal volume (V) of a filter or bag device includes pressurizing the device to a first pressure (p.sub.1) lower than a proof pressure by supplying a test gas, pressurizing the device to proof pressure (p.sub.p), and at the same time, measuring the mass flow (m) or the volumetric flow of test gas, determining the gas temperature (T), and determining the internal volume (V) based on the equation for ideal gases, such that: V=m×R×T/(p.sub.p−p.sub.1) where V is the internal volume, m is the mass flow, R is the gas constant, T is the gas temperature, p.sub.p is the proof pressure and p.sub.1 is the first pressure. A computer program product and a testing apparatus for performing the above-mentioned method also are provided.

A particulate matter (PM) sensor unit may include an exhaust line where exhaust gas passes, and a PM sensor that may be disposed at one side of the exhaust line and that generates a signal when particulate matter included in the exhaust gas passes the vicinity thereof, wherein the PM sensor may be an electrostatic induction type that generates an induction charge while the particulate matter having an electric charge passes the vicinity thereof.

A method and a device for determining a trigger condition for presenting a registered signal on a display of an oscilloscope on the basis of a rare signal event in the registered signal. The method and device determines a level-based and/or time-based distribution of frequencies of occurrence from level-based and/or time-based parameters determined from sampled values of the registered signal in a specified corresponding level-raster and/or time raster, and compares the determined level-based and/or time-based distribution of frequencies of occurrence with a previously given corresponding level-based and/or time-based reference-distribution of frequencies of occurrence. A first trigger condition is determined dependent upon an identified difference between corresponding level-based and/or time-based distribution of frequencies of occurrence and corresponding level-based and/or time-based reference-distribution of frequencies of occurrence. A trigger signal is activated if the trigger condition in the registered signal has been overstepped or undercut.

A gas sensor system is disclosed for detection of a compound that decomposes upon exposure to a metal oxide catalyst. The gas sensor system includes a sensor which includes a microheater, and a metal oxide catalyst that covers the microheater. The gas sensor system includes a pre-concentrator upstream from the sensor that lowers the limit of the detection of a compound.

A system and method of detecting gas leakage along an underground pipeline system accurately determines the presence of a gas leak while minimizing cost and preserving energy. The system includes at least one underground pipeline with a plurality of stack vents, a plurality of sensor units, and at least one remote server. Each sensor unit is mounted within a stack vent. The method begins by tracking a current time with each sensor unit. A gas-concentration reading with at least one specific unit is captured and then communicated along with a sensor location and a sensor identification to the remote server and recorded with the remote server. The tracking, capturing, and communicating of the gas-concentration reading is repeated so that actual gas-concentration data is compiled and compared to a baseline gas-concentration data or a defined gas-concentration threshold. A leak notification for a gas leak is then sent with the remote server.