Servomex Group Limited

Martin Lopez

James D Hobby

Bahram Alizadeh

Richard P Kovacich

Ian C Gaskin

Christopher R Edwards

Colin G Stocks

Graham R Terry

Vasili Kasiutsich

Gary Robert Aylward

Chris Edwards

James Hobby

Michael Anthony Ratcliffe

Nicky Jay Batson

Michael Lawson

James David Hobby

Colin Stocks

Provided are methods, apparatus and systems for stabilization of a glow discharge from a plasma. Also provided are methods, apparatus and systems for processing optical signals from a stabilised glow plasma with enhanced signal to noise recovery. A first method comprises: generating an electric field within a plasma cell using an alternating excitation voltage to excite particles within the cell, to produce a glow discharge from a plasma in the plasma cell in a resonant condition; monitoring, in each excitation cycle of the alternating excitation voltage, one or more signals that correlate with glow discharge optical emissions from the plasma in the plasma cell; and, in response to said monitoring, controlling one or more operating conditions for the plasma cell to maintain the glow discharge emissions from the plasma within a desired operating range in each excitation cycle of the alternating excitation voltage. A relatively stable glow discharge optical emission is maintained via dynamic resonant feedback control of operating conditions such as the electric field that is used to excite particles within the plasma cell. The stabilization of the glow plasma can be used in glow discharge optical emission spectroscopy (GD-OES) for gas analysis and in other applications.

Glow plasma stabilization

A method and system for the suppression and/or modulation of absorption spectrum artifacts for the purpose of gas detection and concentration measurements using at least one magnetic, electric or electromagnetic field. A field applied selectively to at least one section of the system modulates absorption by influencing quantum energy state transitions of gas species.

Electromagnetic control of absorption and suppression of spectral artifacts

Methods and apparatus for determination of the gas composition of a sample gas using glow discharge optical emission spectroscopy, in which the method comprises: generating one or more oscillating electromagnetic fields within a plasma cell to excite particles within the cell, to produce a glow discharge plasma in the plasma cell, and controlling the operating conditions for the plasma cell while flowing a gas mixture through the plasma cell to maintain glow discharge optical emissions from the plasma within a desired operating range; and monitoring one or more glow discharge optical emissions from the plasma in the plasma cell by measuring the optical emissions, or measuring a signal that correlates with the optical emissions, at twice the plasma excitation frequency; and processing the signal during each excitation cycle of the electromagnetic excitation, to determine the concentration of a gas within a gas mixture flowing through the plasma cell.

Glow plasma gas measurement signal processing

An alignment device having two angular degrees of freedom is provided. The alignment device is adjustable such that it is suitable for aligning a first apparatus with respect to a second apparatus. The first apparatus may emit one or more of electromagnetic waves, acoustic waves and matter towards the second apparatus and for detection by the second apparatus. The first and second apparatuses may be disposed in a harsh environment such as is found in the vicinity of an industrial process stack. In some embodiments the first apparatus is a laser, preferably a tunable diode laser, and the second apparatus is a receiver incorporating a detector. In these embodiments the apparatuses may be used to perform laser absorption spectroscopy on a process gas flowing through an industrial process stack.

Alignment device and transmitter/receiver system with two angular degrees of freedom

A method and system for reducing the effect of distortions on the baseline signal in an absorption spectroscopy system used for the detection or measurement of chemical species in a medium, whereby one or more correlations or convolutions are performed on the signal using a kernel function. The shape of the kernel function is chosen to reduce the influence of the baseline distortions on the processed measurand determination. The kernel function may also be chosen to enhance the absorption signal.

Method and system for reduction of influence of baseline distortion in absorption spectroscopy measurements

A device is provided for combining two or more separate components of an optical analysis system, to use common entrance and exit apertures for optical measurements across a measurement space such as a stack, combustion chamber, duct or pipeline, in such way that the optical paths from the respective light sources to detectors are substantially the same, enabling multiple optical measurements over a single optical path or closely aligned optical paths with equivalent ambient conditions such as temperature and pressure distribution and background substance concentrations. The device and a set of interconnectable devices forming a modular system are useful, for example, in absorption spectroscopy, such as for measuring the amount fraction of the chemical constituents of a fluid in a measurement volume.

Attachment and alignment device for optical sources, detectors and analysers, and modular analysis system

A method and system for correcting the effect of intensity fluctuations of the transmitted light in an absorption spectroscopy system used for the detection or measurement of chemical species in a medium, whereby one or more modulation bursts are imposed onto a light beam that passes through the medium. This burst signal may be obtained by modulating the bias current of a tunable diode laser, and the modulation burst signal may be optimally at the second harmonic of the modulation frequency of a wavelength modulated beam to allow usage of the same signal path processing used for the spectroscopic detection of the measurand for a second harmonic detection system. The burst signal can be controlled using a smooth window function to minimise the effects of non-linear perturbations that are inherent in tunable diode laser wavelength modulation spectroscopy systems, of optical interference fringes (etalons) and of the residual light absorption by background chemical species or the measurand at the wavelength coinciding with the modulation burst.

Method and system for correcting incident light fluctuations in absorption spectroscopy

This present invention relates to a device for the measurement of the amount of oxygen in a gas mixture, or other gas with significantly different magnetic susceptibility than the background gas mixture, by the use of a suspended test body in a magnetic field that experiences force due to the magnetic susceptibility of the measurand gas. In order to enable a fast time response for the system with a change in oxygen concentration, a flow regime is presented which allows a fast sweep of the measurement volume combined with adjustable, balanced pressure drops via a flow balancing element (or elements) within the flow channels to independently minimise flow related uncertainties.

Paramagnetic gas sensor apparatus and adjustment method

Provided is a compact apparatus for measuring the flow rate of a fluid. The apparatus includes a heated measure element and a heated reference element which are in substantially the same thermal environment within a measure cell, except that the measure element is situated in the path of the cooling fluid flow and the reference element is sheltered from this direct fluid flow. These elements are arranged as parallel and concentric planar elements that are essentially identical to each other with matching thermal characteristics. The elements are electrically connected in a Wheatstone bridge arrangement. Thermal exchange between the reference and measure elements is used to optimise noise rejection due to common mode background thermal effects. Measured parameters from the bridge can be used to derive the fluid flow rate.

Apparatus for measuring the flow rate of a fluid

Provided are apparatus and methods for compensation of mechanical imbalance in a measurement apparatus, that provides options for increased accuracy and/or less expensive manufacture of a torsion balance. Orientation measurements are taken and an imbalance torque about the torsion spring's axis of rotation is determined, and used to calculate a compensation. The measurement apparatus of one embodiment includes a test body and a set of magnets for generating a first disturbing force on the test body in response to a paramagnetic gas. A conductor element in the magnetic field receives an electrical current that generates a second opposing force to the test body, under feedback control that varies the current until the test body achieves a balanced null position. The control signal required to achieve the fixed null position is measured. Corrections are then made for an imbalance mass by measuring the orientation of the apparatus relative to an acceleration or gravitational field and determining the imbalance torque resulting from the imbalance mass. Use of the invention can improve accuracy or reduce the cost of manufacture of a torsion balance, by enabling compensation for imbalances.

Apparatus and methods for imbalance compensation

The present invention relates to a probe having an elongated main body with a proximal end for attachment to a wall of a duct or volume and a distal end that is disposed on the interior of the duct, such that the main body forms a measurement space through which the fluid is drawn for analysis.

Probe

A sensor for determining the thermal conductivity of a fluid comprising a sensing module located within a housing having inlet and outlet ports for a fluid under test, the sensing module comprising a reference base surface and a sensing element spaced therefrom and having measure and reference sections, and there being provided electrical power monitoring means for monitoring the power through the measure and reference sections in order to generate a signal indicative of the power difference due to thermal conductivity through the fluid. The sensing element is a thick film printed disc with measure and reference resistors printed on it. All changes in the fluid are common to both the measure and reference sections except for the thermal conductivity of the fluid itself.

Thermal conductivity sensor

Correlation spectroscopy measure is improved by correcting for cross interference. This is achieved through applying different gains to the output signals whereby the effect of background interferent species can be calculated and an automatic correction factor applied.

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Rotherfield, United Kingdom

Martin Lopez