DEVICE AND METHOD OF MEASURING CONCENTRATION OF GASEOUS SUBSTANCES Russian patent published in 2016 - IPC G01N21/61 

FIELD: measuring equipment.

SUBSTANCE: invention relates to measurement equipment and can be used for remote measurement of concentration of gaseous substances, including methane, in oil and gas industries, in power engineering etc. Device for measuring concentration of gaseous substances includes a unit of laser radiation with a wavelength varying in the absorption spectral range of a detected molecule and an analytical signal detector optically connected to the unit of laser emitter through a single-mode optical fibre and an analytical single-pass cell, as well as a unit of control, data receiving and processing, the laser emitter unit includes optically series-connected a module of diode laser, a fibre-optic splitter, one end of the fibres of which through the cell is optically connected to a comparing signal detector, and the second end through an additional fiber-optic cable delivering the radiation to an object of research and the analytical cell with fibre-optic input and output, is optically connected to an analytical signal detector. Unit of control, data receiving and processing is made up of three modules, namely: a digital programmable module, a module of digital-to-analog and analog-to-digital converters (DAC and ADC) and a module of analog signals converters, herewith by electric connections of outputs of the analytical signal detector, signal comparator, as well as control signals for the module of diode laser radiation the control is carried out over the diode laser power, its frequency tuning, registration, processing and comparing the analytical signal with the signal of comparison and, finally, calculation of concentration of the object of research. Method involves generating by the diode laser with a fibre radiation output of an optical radiation with a pulse duration overlapping the spectral absorption line of the analyzed gas, splitting this radiation with the help of the fiber splitter into the comparison channel for comparison at the calculation of concentration and to provide additional frequency stabilizing of the diode laser radiation at the level of 0.0002 cm^-1 along the line of methane absorption, input of the second part of the diode laser radiation into the analytical channel consisting of the single-pass cell with fibre-optic input and output, as well as fibre-optic cables for radiation delivery to the cell and outputting the radiation to the detector of analytical signal, determination of concentration of gaseous substances from the analytic and the comparison channels absorption spectra.

EFFECT: invention provides higher sensitivity and accuracy of measurements of volume concentration of methane on remote routes with the help of optical fibre and a single-pass optical cell of small length (less than 100 mm).

5 cl, 2 dwg