Detection and capture of toxic nitrogen oxides (NO.sub.x) is important for emissions control of exhaust gases and general public health. The low power sensor provides direct electrically detection of trace (0.5-5 ppm) NO.sub.2 at relatively low temperatures (50° C.) via changes in the electrical properties of nitrogen-oxide-capture active materials. For example, the high impedance of MOF-74 enables applications requiring a near-zero power sensor or dosimeter, such as for smart industrial systems and the internet of things, with 0.8 mg MOF-74 active material drawing <15 pW for a macroscale sensor 35 mm.sup.2 area.

A sensor element for detecting a specific gas concentration in a measurement-object gas includes: an element body provided with a measurement-object gas flow section therein, the measurement-object gas flow section introducing the measurement-object gas and causing the measurement-object gas to flow therethrough; a reference electrode disposed inside the element body; and a reference-gas introduction section that causes a reference gas to flow to the reference electrode, wherein the reference-gas introduction section has a reference-gas flow path, and one or more preliminary chambers which are disposed in a middle of the reference-gas flow path, and have a diffusion resistance lower than a diffusion resistance of the reference-gas flow path, and at least part of the reference-gas flow path is composed of a porous body so that any of the one or more preliminary chambers does not directly communicate with an outside of the element body.

The invention relates to a photometer (30) for analysing the composition of a sample gas. The photometer comprises an infra-red (IR) source (20) configured to direct a first plurality of pulses (40) of IR radiation through the sample gas to an IR detector (26), at least two of the first plurality of pulses being of different wavelength. The photometer further comprises an ultraviolet (UV) source (32) configured to generate a second plurality of pulses (38) of UV radiation for conveyance to a UV detector (36), at least two of the second plurality of pulses being of different wavelength. A path selection arrangement (22, 42-50) is configured to selectively convey different ones of the second plurality of pulses (38) to one of the sample gas and the UV detector (36). The photometer further comprises processing circuitry coupled to the IR source (20), the UV source (32), the IR detector (26), the UV detector (36) and the path selection arrangement (22, 42-50). The processing circuitry is configured to (i) select the wavelength to be used for a given UV pulse of the second plurality of pulses (38), (ii) receive a plurality of detection signals from each of the IR detector (26) and the UV detector (36) and (iii) based on the detection signals, determine a concentration of at least one component of the sample gas. A method for analysing the composition of a sample gas is also disclosed.

A sensing device for sensing a target gas includes a measurement module for providing measurement information about a measurement of the concentration. The sensing device further includes a signal calibration module for using a machine learning model for determining, on the basis of the measurement information, a calibrated measurement value of the concentration. The signal calibration module determines a feedback feature using the calibrated measurement value. The signal calibration module uses the machine learning model for determining a subsequent calibrated measurement value on the basis of subsequent measurement information about a subsequent measurement of the concentration and on the basis of the feedback feature.

A method of measuring a concentration of NO.sub.2 in a gaseous mixture using a multimode laser beam that covers a tunable spectral range with a width of no more than 5 nm, wherein the multimode laser beam provides a high resolution transmittance spectrum at an absorption cross section of NO.sub.2 molecules, and a system for measuring the concentration of NO.sub.2 in the gaseous mixture. Various combinations of embodiments of the system and the method are provided.

A controller of the gas sensor can perform diagnostic processing of diagnosing a situation of control to the gas sensor in a case that the gas sensor in an operation state is determined to satisfy a predetermined diagnostic condition and adjustment processing of adjusting a condition for controlling the gas sensor in accordance with a result of diagnosis. In the diagnostic processing, a main pump voltage and a diagnostic threshold as a value of a voltage not causing decomposition of NOx in the main pump cell are compared. In the adjustment processing, temperature adjustment processing to cause, in a case that the main pump voltage is diagnosed to be equal to the threshold or more, the main pump voltage to be less than the threshold, at least in a way that the heater part increases the element driving temperature in the operation state by a predetermined increase amount is performed.

A sensor element includes an element body that contains a measurement-object gas flow section and a heat generation portion. The measurement-object gas flow section includes a main pump chamber, an auxiliary pump chamber, and a measurement chamber. A distance X1 in a left-right direction between a part of a first inner linear portion and a part of a second inner linear portion of the heat generation portion that overlap a main pump chamber projection region is equal to or more than ⅓ of a width Wp of the main pump chamber projection region in the left-right direction. A distance X2 in the left-right direction between a part of the first inner linear portion and a part of the second inner linear portion that overlap an auxiliary pump chamber projection region is equal to or more than 0.4 times the width Wp.

In a method for manufacturing a gas sensor, a casing for holding a sensor element and a protective cover are connected to each other so that a distal end portion of the sensor element is covered with the protective cover. A first gas chamber, a sensor element chamber, and a second gas chamber into which gas is introduced from the outside are formed between the protective cover and the casing. In the gas introduction portion including the first gas chamber, the sensor element chamber, and the second gas chamber, there is no joint portion formed by welding.

A sensor element for detecting a target gas to be measured in a measurement-object gas includes: an element body including an oxygen-ion-conductive solid electrolyte layer; and a protective layer covering at least a part of a surface of the element body. The protective layer includes a porous material that has a pore inside; and, in the pore in the protective layer, a ratio (Lt/Lf) of a pore length (Lt) in a thickness direction perpendicular to the surface of the element body to a pore length (Lf) in a surface direction perpendicular to the thickness direction is 0.6 to 0.9.

A gas sensor for sensing a gas in a humid environment includes a first electrode layer, a second electrode layer that is spaced apart from the first electrode layer, and a gas sensing layer that electrically interconnects the first electrode layer and the second electrode layer. The gas sensing layer is made of a hygroscopic electrically insulating material.