There is provided a method for measuring a composition of a gas circulating through a plasma-based detector, the plasma-based detector having a discharge chamber defining an internal volume and having discharge electrodes configured to apply a plasma-generating field across the discharge chamber. The method includes ramping a voltage until it reaches a breakdown voltage to generate a plasma, detecting the presence of the plasma, determining a pressure based on the breakdown voltage upon detection of the presence of the plasma, operating the detector at an operation voltage greater than the breakdown voltage, performing measurement(s) on the plasma, generating a detector signal based the measurement(s) and compensating the detector signal based on the determined pressure to obtain a compensated detector signal, the compensated detector signal being representative of the composition of the gas. A plasma-based detector for measuring the composition of the gas is also provided.

According to one aspect, the present description relates to a stabilized interferometric system comprising a light source (210) for emitting an initial beam (B.sub.0) of coherent light and a spatial light modulator (220) configured to receive at least a first part of said initial beam and input data (203), and configured to emit a spatially modulated beam (B.sub.0m) resulting from a spatial modulation of a parameter of said first part of said initial beam based on said input data. The stabilized interferometric system further comprises a scattering medium (230) configured to receive said spatially modulated beam and a detection unit (240) configured to acquire an interference pattern (IN.sub.0) in a first detection plane (241) at an output of said scattering material, wherein said interference pattern results from the interferences between randomly scattered optical paths taken by the spatially modulated beam through the scattering material. The stabilized interferometric system further comprises a control unit (250) configured to vary the frequency of the laser source in order to at least partially compensate a change in said interference pattern resulting from a change in at least one environmental parameter.

In order to make it possible to conduct a zero calibration even though an interference gas exists in a measurement area of a detector, a light absorbance analysis apparatus includes a detector that detects an intensity of light that transmits a gas, a total pressure sensor that measures a total pressure of the gas, an absorbance calculating part that calculates an absorbance based on an output value of the detector and a previously set zero reference value, a partial pressureabsorbance relation storing part that stores a partial pressureabsorbance relational data that indicates a relationship between a partial pressure of an interference gas that exists in a measurement area of the detector and an absorbance calculated by the absorbance calculating part, and a partial pressure calculating part that calculates an interference gas partial pressure as a partial pressure of the interference gas.

Methods, devices, and systems are provided for analyzing the moisture content in natural gas. In one embodiment, a portable moisture analyzer system is provided and can include a moisture analyzer and a housing. The moisture analyzer can include a tunable diode laser absorption spectrometer (TDLAS) and a natural gas sample conditioning system. The TDLAS can be configured to detect water vapor content within a natural gas sample. The sample conditioning system can be in fluid communication with the TDLAS and can be configured to condition at least one of temperature, flow rate, and pressure of a natural gas sample. The housing can be configured to receive the moisture analyzer therein and to protect the moisture analyzer from vibration and/or shock.

An embodiment of a system for measuring trace gas concentration is described that comprises a laser absorption spectrometer configured to detect an absorbance measure from a trace gas, as well as a temperature value and a pressure value that correspond to an environment in a gas cell; and a computer having executable code stored thereon configured to perform a method comprising: receiving the absorbance value, the temperature value, and the pressure value; defining a fitting range associated with the trace gas; applying a curve fitting model in the fitting range to the absorbance value using the temperature value and the pressure value as model parameters; and producing a concentration measure of the trace gas.

An arrangement for measuring gas concentrations in a gas absorption method, wherein the arrangement includes a plurality of light sources, a measuring cell, at least one measuring receiver and an evaluation apparatus. The measuring cell has a narrow, longitudinally-extended beam path with an entrance-side opening diameter B and an absorption length L with L>B, wherein the measuring cell has a gas inlet and a gas outlet wherein a plurality of light sources of different wavelength spectra is grouped into a first light source group wherein an optical homogeniser is interposed between the first light source group and the measuring cell, wherein, in particular, the homogeniser is coupled to the light source group directly or via a common optical assembly.

A flow cell has a tubular main body and a thermocouple. An internal space is formed in the main body, a plurality of opening portions allowing the internal space to communicate with an external portion is formed in a peripheral wall, and sample gas flowing from at least one of the plurality of opening portions passes through the internal space and flows out of the other opening portion. The thermocouple includes two metal wires which are integrally attached to the main body, and a joint part of the two metal wires is provided in the vicinity (proximate) of the opening portion closer to an upstream side of the sample gas in a distributing direction than a center axis line of the main body.

Methods, devices, and systems are provided for analyzing the moisture content in natural gas. In one embodiment, a portable moisture analyzer system is provided and can include a moisture analyzer and a housing. The moisture analyzer can include a tunable diode laser absorption spectrometer (TDLAS) and a natural gas sample conditioning system. The TDLAS can be configured to detect water vapor content within a natural gas sample. The sample conditioning system can be in fluid communication with the TDLAS and can be configured to condition at least one of temperature, flow rate, and pressure of a natural gas sample. The housing can be configured to receive the moisture analyzer therein and to protect the moisture analyzer from vibration and/or shock.

A bi-directional photoacoustic gas sensor includes a first photoacoustic cell, where an electromagnetic radiation source emits radiation to interact with an external gas and generate pressure waves that are detected by a MEMS diaphragm. A second photoacoustic cell has an interior volume and acoustic compliance that corresponds to the interior volume and acoustic compliance of the first photoacoustic cell. Processing circuitry within a substrate uses a first acoustic signal, received by the first photoacoustic cell, and a second acoustic signal, received by the second photoacoustic cell, to determine a bi-directional response of the gas sensor to remove noise and improve the sensor's signal-to-noise ratio.

Provided are light absorption spectrum correction devices, methods of manufacturing the light absorption spectrum correction devices, and methods of correcting a light absorption spectrum. The light absorption spectrum correction device includes: a light source configured to emit light; an attenuated total reflectance (ATR) crystal layer configured to contact a subject and provide an optical passage along which the light emitted from the light source travels to the subject; a pressure sensor configured to detect a contact pressure applied to the ATR crystal layer by the subject; a spectrum detector and analyzer configured to detect light emitted from the ATR crystal layer, form a light absorption spectrum based on the detected light, and determine an intensity of the light emitted from the ATR crystal layer; and a spectrum correction device configured to correct the light absorption spectrum based on the contact pressure.