Optical fibre sensing type CH4 gas survey instrument

Abstract

The invention relates to an instrument for using a dual-wavelength optical fiber sensor for the measurement of CH4 gas. Two infrared lights are alternatively transmitted on the measured CH4 gas by a grating assembly type optical fiber sensor, the lights are reflected back to the optical fiber sensor after the lights are partially absorbed by the gas, the lights are sent to a pre-amplifier by receiving optical fibers to be converted into the electrical signals, after that, the electrical signals are sent to an A / D converter after the processing by a lock-in amplifying circuit. A signal processing system sends the signals after the A / D conversion to a data processing unit and divides the signals into the measurement signals, measurement light intensity signals, reference signals and reference light intensity signals. The concentration of the CH4 is finally obtained by processing the data according to the corresponding algorithms. The invention solves the problems of easy poisoning of an electronic gas sensor of the traditional CH4 gas detection and the misreport and missing-report because the resistance of a sensitive body of the gas sensor changes along with the temperature change of the outside; the invention adopts the grating assembly type transmitting-receiving optical fiber beams to avoid the direct contact with the gas, at the same time, the invention uses an auxiliary dual-wavelength ratio method to eliminate the influence of other gas components on the absorption wavelength and the influence of the background light, so as to improve the sensitivity and the reliability of the instrument.

Description

[technical field] [0001] The present invention relates to a CH 4 A gas measuring instrument belongs to the technical field of electronic measuring instruments. [Background technique] [0002] Compared with traditional electronic gas sensor measurement, infrared measurement method is one of several fast measurement methods. Its principle is to use the measured gas to only absorb specific infrared wavelengths, and different concentrations of gases correspond to different absorption light intensities, so as to obtain light Relationship between strength and concentration. Current domestic CH 4 The gas measuring instrument uses an electronic gas sensor to change the concentration of the gas to be measured into an electrical signal through the electrochemical reaction of the gas sensor. After the steady state is established, the changed electrical signal is processed, but the sensor is easy to be poisoned. At the same time, the gas sensor The resistance of the sensitive body al...

AI Technical Summary

Problems solved by technology

Current domestic CH 4 The gas measuring instrument uses an electronic gas sensor to change the concentration of the gas to be measured into an electrical signal through the electrochemical reaction of the gas sensor. After the steady state is established, the changed electrical signal is processed, but the sensor is easy to be poisoned. At the same time, the gas sensor The resistance of the sensitive body changes with the change of temperature, and the resistance value also changes, which is easily affected by the external temperature and leads to false positives and false negatives.

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