CN112857571A

CN112857571A - Photoacoustic spectrum detection system and calibration method for automatically calibrating working wavelength of laser

Info

Publication number: CN112857571A
Application number: CN202110183262.6A
Authority: CN
Inventors: 王世有
Original assignee: Individual
Current assignee: Individual
Priority date: 2021-02-10
Filing date: 2021-02-10
Publication date: 2021-05-28

Abstract

The invention discloses a photoacoustic spectrum detection system capable of automatically calibrating the working wavelength of a laser, which is provided with a rear quartz lens, wherein a reference gas pool capable of receiving light of the laser is arranged on the other side of the rear quartz lens, a reflector is arranged on the opposite side of the reference gas pool and the rear quartz lens, the reflector and the light of the laser are arranged in an inclined angle, a photoelectric detector is arranged on a reflection light path of the reflector, the output end of the photoelectric detector is connected with an AD converter, a standard gas mixture is sealed in the reference gas pool, the types of standard gases in the standard gas mixture are equal to the number of the lasers, the concentration of each standard gas in the standard gas mixture is greater than or equal to the maximum value of the concentration range of the corresponding gas to be measured, and various problems existing in the prior art of regular artificial calibration and calibration are solved.

Description

Photoacoustic spectrum detection system and calibration method for automatically calibrating working wavelength of laser

Technical Field

The invention relates to the technical field of photoacoustic spectroscopy gas absorption, in particular to a photoacoustic spectroscopy detection system and a photoacoustic spectroscopy detection method for automatically calibrating the working wavelength of a laser.

Background

Photoacoustic spectroscopy detection systems have been applied to gas concentration detection. The existing photoacoustic spectrum detection system comprises a base, a photoacoustic cell, an air inlet pipe and an air outlet pipe which are communicated with a resonant cavity of the photoacoustic cell are arranged on the base, the air inlet pipe and the air outlet pipe are provided with electromagnetic valves for controlling the air flow, the front end and the rear end of the photoacoustic cell are respectively provided with an anti-reflection vacuum double-layer quartz lens, a beam expander connected with a laser through an optical fiber is arranged in front of the quartz lens at the front end, a sound detection port and a sound pick-up are arranged in the middle of a resonant area of the photoacoustic cell, the sound pick-up is connected with a single chip microcomputer through an audio amplifier and an AD converter in sequence, and the single chip microcomputer is connected. Because the kind of the gas to be measured is already determined (for example, the transformer oil will dissolve to generate hydrogen, carbon monoxide, carbon dioxide and various hydrocarbon gases), it is necessary to set a plurality of lasers with the same kind as the gas to be measured and the working wavelength of each laser is equal to the corresponding absorption wavelength of the gas to be measured. During detection, the single chip microcomputer controls the plurality of lasers to sequentially emit light and pass through the beam expander, the anti-reflection vacuum double-layer quartz lens and the photoacoustic cell, spectral absorption is generated in the detected gas due to the fact that the working wavelength of the laser is equal to the absorption wavelength of the detected gas, the absorbed light energy is converted into photoacoustic spectrums through the sound detection port, the sound pick-up, the audio amplifier and the AD converter, and therefore the concentration of the corresponding detected gas is detected.

Because the output wavelength, the current threshold value and the like of the laser are directly influenced by the working temperature of the laser, a thermistor and a refrigerator such as a thermoelectric cooler (TEC) are integrated in the existing laser, and the singlechip controls the laser to work at a target temperature through a temperature controller, so that the output wavelength of the laser is locked as the working wavelength. However, as the light source of the laser attenuates along with the service life, the output wavelength of the light source may drift, which causes deviation between the actual output wavelength and the set working wavelength, so that the conventional photoacoustic spectroscopy detection system needs to be calibrated and calibrated regularly, which is time-consuming and labor-consuming, and has the problem that the precision is difficult to be ensured, especially in the field of a transformer substation, a power station, etc., the regular calibration and calibration are difficult to be realized regularly, thereby affecting the detection accuracy.

Disclosure of Invention

The invention provides a photoacoustic spectrometry detection system and a photoacoustic spectrometry detection method for automatically calibrating the working wavelength of a laser, which aim to solve the technical problems in the prior art.

The technical solution of the invention is as follows: a photoacoustic spectrum detection system capable of automatically calibrating the working wavelength of a laser comprises a base, a photoacoustic cell, an air inlet pipe and an air outlet pipe which are communicated with the photoacoustic cell are arranged on the base, a front quartz lens and a rear quartz lens are respectively and correspondingly arranged at the front end and the rear end of the photoacoustic cell, a beam expander is arranged in front of the front quartz lens, a sound detection port and a pickup are arranged in the middle of a resonant area of the photoacoustic cell, the pickup is connected with a single chip microcomputer through an audio amplifier and an AD converter in sequence, the single chip microcomputer is connected with the laser through a current controller and a temperature controller respectively, the laser is connected with the beam expander through an optical fiber, a reference gas cell capable of receiving the light ray of the laser is arranged at the other side of the rear quartz lens, a reflecting mirror is arranged at the rear end of the reference gas cell, the reflecting mirror is arranged at an inclined angle with the light ray of the laser, the output end of the photoelectric detector is connected with the AD converter, a standard gas mixture is sealed in the reference gas pool, the number of the standard gas types in the standard gas mixture is equal to that of the lasers, and the concentration of each standard gas in the standard gas mixture is greater than or equal to the maximum value of the corresponding measured gas concentration range.

A calibration method of the photoacoustic spectrometry detection system for automatically calibrating the working wavelength of the laser comprises the following steps:

a. the singlechip controls the laser to dynamically scan within the temperature range of-20-55 ℃ through the temperature controller and receives an optical power signal sent by the photoelectric detector within the temperature range;

b. the singlechip takes the laser output wavelength corresponding to the lowest moment of the optical power signal in the range as the calibrated working wavelength and locks the working wavelength through the temperature controller.

The invention can automatically calibrate the working wavelength of the laser before detection through the arranged photoelectric detector so as to correct the deviation between the actual output wavelength of the laser and the set working wavelength, overcomes the problems of time and labor waste, low precision, incapability of calibrating on site in a transformer substation, a power station and the like in the prior art by manual calibration at regular intervals, and effectively improves the detection accuracy of the photoacoustic spectrum detection system.

Drawings

Fig. 1 is a mechanical structure diagram of an embodiment of the present invention.

Fig. 2 is a schematic block diagram of a circuit of an embodiment of the invention.

Detailed Description

The invention relates to a photoacoustic spectrum detection system capable of automatically calibrating the working wavelength of a laser, which is shown in figures 1 and 2, and the photoacoustic spectrum detection system is also provided with a base 1 as in the prior art, wherein a photoacoustic cell 2, an air inlet pipe 3 and an air outlet pipe 4 which are communicated with the photoacoustic cell 2 are arranged on the base 1, a front quartz lens 5 and a rear quartz lens 6 are respectively and correspondingly arranged at the front end and the rear end of the photoacoustic cell 2, the front quartz lens 5 and the rear quartz lens 6 are respectively anti-reflection vacuum double-layer quartz lenses, a beam expanding lens 7 is arranged in front of the front quartz lens 5, a sound detection port and a sound pick-up 8 are arranged in the middle of a resonance area of the photoacoustic cell 2, the sound pick-up 8 is connected with a singlechip 11 sequentially through an audio amplifier 9 and an AD converter 10, the singlechip 11 is connected with a laser 14 through a current controller 12 and a temperature controller 13 respectively, the laser 14 is connected with the beam expanding lens 7 through an optical fiber, and a reference gas cell 15 capable of receiving, that is, the quartz lens 6 is a light inlet channel of the reference gas cell 15, the rear end of the reference gas cell 15 (i.e., the side opposite to the rear quartz lens 6) is provided with the reflector 16, the reflector 16 and the light of the laser 14 are arranged at an inclined angle (30-60 ℃) so as to prevent the reflected light of the reflector 16 from entering the photoacoustic cell 2, the reflected light path of the reflector 16 is provided with the photodetector 17, and the output end of the photodetector 17 is connected with the AD converter 11. And filling standard gas corresponding to the measured gas from a gas inlet 19 of the reference gas pool 15, and then sealing, namely sealing a standard gas mixture 18 in the reference gas pool 15, wherein the types of the standard gas in the standard gas mixture 18 are equal to the number of the lasers 7, and the concentration of each standard gas in the standard gas mixture 18 is greater than or equal to the maximum value of the concentration range of the corresponding measured gas. For example, the gas to be detected contains carbon monoxide, carbon dioxide and acetylene, the number of the lasers is 3, three standard gases of carbon monoxide, carbon dioxide and acetylene are contained in the standard gas mixture 18, and the concentration of the carbon monoxide, the carbon dioxide and the acetylene is greater than or equal to the maximum value of the concentration range of the carbon monoxide, the carbon dioxide and the acetylene detected by the photoacoustic spectrometry detection system.

Before each detection, the working wavelength of each laser is automatically calibrated in sequence, and the calibration process is as follows:

a. the singlechip 11 controls a laser 14 to dynamically scan within the temperature range of-20 to 55 ℃ through a temperature controller 13, laser emitted by the laser 14 enters a reference gas pool 15 through a photoacoustic pool 2 and a rear quartz lens 6 which are not introduced into gas to be detected, then passes through a standard gas mixture 18 to a reflector 16, light emitted by the reflector 16 is transmitted to a photoelectric detector 17, and a light power signal emitted by the photoelectric detector 17 is converted into a digital signal through an AD converter 11 and transmitted to the singlechip 11;

b. since the output wavelength of the laser 17 changes within the temperature range of-20 to 55 ℃, only the output wavelength equal to the absorption wavelength of a certain standard gas in the reference gas pool 15 is absorbed by the standard gas, and therefore the output wavelength of the laser 17 corresponding to the lowest time of the optical power signal within the range is the working wavelength for detecting the standard gas, the single chip microcomputer 11 uses the output wavelength of the laser 17 corresponding to the lowest time of the optical power signal within the range as the calibrated working wavelength and locks the working wavelength through the temperature controller 13.

Claims

1. A photoacoustic spectrum detection system capable of automatically calibrating the working wavelength of a laser comprises a base (1), a photoacoustic cell (2) and an air inlet pipe (3) and an air outlet pipe (4) which are communicated with the photoacoustic cell (2) are arranged on the base (1), a front quartz lens (5) and a rear quartz lens (6) are respectively and correspondingly arranged at the front end and the rear end of the photoacoustic cell (2), a beam expander (7) is arranged in front of the front quartz lens (5), a sound detection port and a sound pick-up (8) are arranged in the middle of the resonance area of the photoacoustic cell (2), adapter (8) loop through audio amplifier (9), AD converter (10) and meet with singlechip (11), and singlechip (11) meet through current controller (12), temperature controller (13) and laser instrument (14) respectively, and laser instrument (14) meet its characterized in that through optic fibre and beam expanding lens (7): back quartz lens (6) opposite side is equipped with reference gas cell (15) that can receive laser instrument (14) light, and reference gas cell (15) rear end is equipped with speculum (16), speculum (16) are the inclination setting with the light of laser instrument (14), are equipped with photoelectric detector (17) on the reverberation way of speculum (16), and the output and the AD converter (11) of photoelectric detector (17) meet, it has standard gas mixture (18) to seal in reference gas cell (15), the number of standard gas mixture kind and laser instrument (7) in standard gas mixture (18) equals, the concentration of every kind of standard gas is greater than or equal to the maximum value that corresponds measured gas concentration range in standard gas mixture (18).

2. A method for calibrating a photoacoustic spectroscopy detection system for automatically calibrating an operating wavelength of a laser according to claim 1, comprising the steps of:

a. the singlechip (11) controls the laser (14) to be at the temperature of-20-55 ℃ through the temperature controller (13)

Dynamically scanning in a range and receiving an optical power signal sent by a photoelectric detector (17) in the temperature range;

b. the singlechip (11) takes the output wavelength of the laser (17) corresponding to the lowest moment of the optical power signal in the range as the calibrated working wavelength and locks the working wavelength through the temperature controller (13).