CN207318348U - Gas concentration detection system based on Wavelength modulation spectroscopy - Google Patents
Gas concentration detection system based on Wavelength modulation spectroscopy Download PDFInfo
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- CN207318348U CN207318348U CN201721186465.6U CN201721186465U CN207318348U CN 207318348 U CN207318348 U CN 207318348U CN 201721186465 U CN201721186465 U CN 201721186465U CN 207318348 U CN207318348 U CN 207318348U
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- concentration detection
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Abstract
It the utility model is related to the gas concentration detection system based on Wavelength modulation spectroscopy,The sine wave signal output terminal connection adder of its first signal generator,The triangular signal output terminal connection adder of secondary signal generator,Adder output connects pulse width modulator,The signal output part connection laser driver of pulse width modulator,The laser-driven signal input terminal connection distributed feedback laser of laser driver,The laser signal output end face of distributed feedback laser detects gas chamber to gas concentration,Laser signal exit wound of bullet of the signal input part of laser detector towards gas concentration detection gas chamber,The signal input part of the laser induced signal output part connection processing device of laser detector,The cosine wave signal output terminal connection lock-in amplifier of first signal generator,The signal output part connection processing device of lock-in amplifier,The triangular signal output terminal connection processing device of secondary signal generator.The utility model can accurately measure gas concentration.
Description
Technical field
It the utility model is related to technical field of photo communication, and in particular to a kind of gas concentration inspection based on Wavelength modulation spectroscopy
Examining system.
Background technology
Existing gas concentration detection system, the modulator approach of used light source is for single triangular wave or individually just
String ripple is modulated, and the adjustment mode of this light source can not provide and modulated signal (single triangular wave or individually just in demodulation
String ripple) into 90 degree of demodulated signals, therefore the modulation accuracy of this modulation of source is not high, so as to have impact on gas concentration detection system
The precision of the Concentration Testing result of system.
Utility model content
The purpose of this utility model is to provide a kind of gas concentration detection system based on Wavelength modulation spectroscopy, the system
Can fast and accurate measurement gas concentration.
A kind of in order to solve the above technical problems, gas concentration detection based on Wavelength modulation spectroscopy disclosed in the utility model
System, it is characterised in that it includes the first signal generator, secondary signal generator, adder, pulse width modulator, laser and drives
Dynamic device, distributed feedback laser, gas concentration detection gas chamber, laser detector, lock-in amplifier and processor, described first
First signal input part of the sine wave signal output terminal connection adder of signal generator, the triangular wave of secondary signal generator
Signal output part connects the secondary signal input terminal of adder, the letter of the signal output part connection pulse width modulator of the adder
Number input terminal, the signal input part of the signal output part connection laser driver of pulse width modulator, the laser of laser driver drive
The driving signal input of dynamic signal output part connection distributed feedback laser, the laser signal of distributed feedback laser are defeated
Outlet is examined towards the laser signal entrance port of gas concentration detection gas chamber, the signal input part of laser detector towards gas concentration
The laser signal exit wound of bullet of survey gas chamber, the signal input part of the laser induced signal output part connection processing device of laser detector,
The signal input part of the cosine wave signal output terminal connection lock-in amplifier of first signal generator, the signal of lock-in amplifier are defeated
The demodulated reference signal input terminal of outlet connection processing device, the triangular signal output terminal connection processing device of secondary signal generator
Demodulated signal input terminal.
Gas concentration detection of the utility model based on optical fiber is to be completed by light in optical fiber, gas concentration detect gas chamber
, since transmission speed of the light in these media is fast, and the speed of opto-electronic conversion is also fast, so overall measuring speed compared with
It hurry up.The advantages of fiber laser arrays, includes its essential safety, and photo measure interference is small, and the utility model is using Wavelength modulation spectroscopy to swashing
When light device is modulated, the absorbing wavelength of gas can be accurately aimed at, hence it is evident that improve the inspection accuracy of gas concentration.
Brief description of the drawings
Fig. 1 is the block diagram of the utility model；
Wherein, the 1-the first signal generator, 2-secondary signal generator, 3-adder, 4-pulse width modulator, 5-
Laser driver, 6-distributed feedback laser, 7-gas concentration detection gas chamber, 8-laser detector, 9-locking amplification
Device, 10-processor.
Embodiment
Below in conjunction with the drawings and specific embodiments, the utility model is described in further detail：
Gas concentration detection system of the utility model based on Wavelength modulation spectroscopy, as shown in Figure 1, it includes the first signal
Generator 1, secondary signal generator 2, adder 3, pulse width modulator 4, laser driver 5, distributed feedback laser 6, gas
Bulk concentration detection gas chamber 7, laser detector 8, lock-in amplifier 9 and processor 10, the sine wave of first signal generator 1
Signal output part connects the first signal input part of adder 3, and the triangular signal output terminal connection of secondary signal generator 2 adds
The secondary signal input terminal of musical instruments used in a Buddhist or Taoist mass 3, the signal input part of the signal output part connection pulse width modulator 4 of the adder 3, pulsewidth
The signal input part of the signal output part connection laser driver 5 of modulator 4, the laser-driven signal output of laser driver 5
The driving signal input of end connection distributed feedback laser 6, the laser signal output end face of distributed feedback laser 6 to
Gas concentration detects the laser signal entrance port of gas chamber 7, and the signal input part of laser detector 8 detects gas chamber towards gas concentration
7 laser signal exit wound of bullet, the signal input part of the laser induced signal output part connection processing device 10 of laser detector 8, the
The signal input part of the cosine wave signal output terminal connection lock-in amplifier 9 of one signal generator 1, the signal of lock-in amplifier 9
The demodulated reference signal input terminal of output terminal connection processing device 10, the triangular signal output terminal connection of secondary signal generator 2
The demodulated signal input terminal of processor 10.
In above-mentioned technical proposal, sine wave signal and the frequency of cosine wave signal that first signal generator 1 exports
It is 100 times of the frequency for the triangular signal that secondary signal generator 2 exports.Selection triangular wave is to be able to needed for scanning
Gas absorption spectrum line, and sine wave and cosine wave are to be demodulated use to modulated signal.Frequency between two kinds of signals
The relation for being designed as 100 times is because can well distinguish scanning signal and modulated signal on frequency domain, is detected
When obtain high accuracy of detection.
In above-mentioned technical proposal, sine wave signal and the frequency of cosine wave signal that first signal generator 1 exports
It is equal, and frequency range is 100Hz~100kHz；The frequency model for the triangular signal that the secondary signal generator 2 exports
Enclose for 1Hz~1kHz.
In above-mentioned technical proposal, the superposed signal of the signal output part of the adder 3 output sine wave and triangular wave into
Enter pulse width modulator 4, pulse width modulator 4 carries out non-inverting input pulse-width signal to above-mentioned superposed signal.Pulsewidth modulation
The measurement to gas can be completed according to different measurement frequency demands, measurement frequency is high, and pulse width modulation frequency needs higher.
In above-mentioned technical proposal, the distributed feedback laser 6 is used for the laser signal to gas concentration detection gas chamber 7
Entrance port output wavelength scope for 1650~1656nm (this scope be according to the absorption line of gas (methane) come definite,
The absorption line of methane is within this range) laser.
In above-mentioned technical proposal, gas to be detected in gas concentration detection gas chamber 7 to the light intensity of incident laser into
Row absorbs, the laser signal of the laser signal exit wound of bullet output light intensity decrease of the gas concentration detection gas chamber 7.Weaken intensity
It is microvolt level after opto-electronic conversion calculates.
In above-mentioned technical proposal, the laser detector 8 is used for defeated to gas concentration detection 7 laser signal exit wound of bullet of gas chamber
The laser signal gone out is detected, and exports the laser induced electric signal of microvolt level to processor 10.
In above-mentioned technical proposal, above-mentioned processor 10 is used to absorb the under test gas in the laser induced electric signal of microvolt level
The second harmonic of light intensity signal afterwards using demodulated reference signal and triangular signal carry out locking amplification demodulation, obtain with it is to be measured
The relevant magnitude of voltage of gas concentration, the magnitude of voltage be second harmonic signal peak-to-peak value, then with the under test gas of concentration known
Concentration value be normalized, obtain the correspondence of multigroup voltage signal and under test gas concentration, the magnitude of voltage be two
The peak-to-peak value of rd harmonic signal, the correspondence of multigroup voltage signal and under test gas concentration is normalized to obtain
State second harmonic equation corresponding with test gas concentration.
A kind of gas concentration detection method using said system, it includes the following steps：
Step 1：First signal generator 1 is believed to the sine wave that 3 frequency of delivery scope of adder is 100Hz~100kHz
Number, triangular signal of the secondary signal generator 2 to 3 frequency of delivery scope of adder for 1Hz~1kHz；
Step 2：Adder 3 carries out above-mentioned sine wave signal and triangular signal after addition process to pulse width modulator 4
The superposed signal of sine wave and triangular wave is exported, pulse width modulator 4 carries out non-inverting input pulsewidth tune to above-mentioned superposed signal
Signal processed；
Step 3：Laser driver 5 controls distributed feedback laser 6 to be detected to gas concentration according to pulse-width signal
The laser signal entrance port output wavelength scope of gas chamber 7 is the laser of 1650~1656nm；
Step 4：The under test gas of concentration known is filled with gas concentration detection gas chamber 7, gas concentration is detected in gas chamber 7
The under test gas of concentration known the light intensity of incident laser is absorbed, the laser signal of the gas concentration detection gas chamber 7
The laser signal that exit wound of bullet output light intensity weakens；
Step 5：Laser signal of the laser detector 8 to gas concentration detection gas chamber 7 laser signal exit wound of bullet output
Detected, and export the laser induced electric signal of microvolt level to processor 10；
Step 6：First signal generator 1 exports the cosine equal with above-mentioned sine wave signal frequency to lock-in amplifier 9
Ripple signal, lock-in amplifier 9 carry out cosine wave signal locking amplification and form demodulated reference signal, and lock-in amplifier 9 will demodulate
Reference signal is conveyed to processor 10, and triangular signal is conveyed to processor 10 by secondary signal generator 2；
Step 7：Include the secondary humorous of the light intensity signal after the under test gas absorption of concentration known in the laser induced electric signal of microvolt level
Ripple, processor 10 carry out locking amplification demodulation (process to above-mentioned second harmonic using demodulated reference signal and triangular signal
Bibliography be：D’amico,A.,et al."Low-voltage low-power integrated analog lock-
in amplifier for gas sensor applications."Sensors and Actuators B:Chemical
144.2(2010):400-406.), it is secondary to obtain with the concentration dependent magnitude of voltage of the under test gas of concentration known, the magnitude of voltage
The concentration value of the magnitude of voltage and the under test gas of concentration known, is then normalized, obtains by the peak-to-peak value of harmonic signal
To multigroup voltage signal and the correspondence of under test gas concentration, by multigroup voltage signal and the correspondence of under test gas concentration
It is normalized to obtain the equation of above-mentioned second harmonic and under test gas concentration；
Step 8：The under test gas of concentration to be detected will be filled with gas concentration detection gas chamber 7, then repeats to walk
Rapid 1~step 3, then light intensity progress of the under test gas of the concentration to be detected in gas concentration detection gas chamber 7 to incident laser
Absorb, the laser signal of the laser signal exit wound of bullet output light intensity decrease of the gas concentration detection gas chamber 7；
Then step 5 and step 6 are repeated, then processor 10 is in the obtained laser induced electric signal of microvolt level
The under test gas of concentration to be detected absorb after light intensity signal second harmonic, using the second harmonic that step 8 obtains with it is to be measured
The equation calculation of gas concentration obtains the gas concentration of the under test gas of concentration to be detected.
In above-mentioned technical proposal, under test gas selected as formaldehyde gas.
In above-mentioned technical proposal, the second harmonic and the equation of under test gas concentration are y=3.862x+0.03669, its
In, x represents the amplitude of second harmonic, and y represents under test gas concentration value.
The content that this specification is not described in detail belongs to the prior art known to professional and technical personnel in the field.
Claims (8)
1. a kind of gas concentration detection system based on Wavelength modulation spectroscopy, it is characterised in that it includes the first signal generator
(1), secondary signal generator (2), adder (3), pulse width modulator (4), laser driver (5), distributed feedback laser
(6), gas concentration detection gas chamber (7), laser detector (8), lock-in amplifier (9) and processor (10), first signal
First signal input part of the sine wave signal output terminal connection adder (3) of generator (1), secondary signal generator (2)
The secondary signal input terminal of triangular signal output terminal connection adder (3), the signal output part connection arteries and veins of the adder (3)
The signal input part of wide modulator (4), the signal input of the signal output part connection laser driver (5) of pulse width modulator (4)
End, the driving signal input of the laser-driven signal output terminal connection distributed feedback laser (6) of laser driver (5),
The laser signal output end face of distributed feedback laser (6) swashs to the laser signal entrance port of gas concentration detection gas chamber (7)
The signal input part of optical detector (8) detects the laser signal exit wound of bullet of gas chamber (7), laser detector (8) towards gas concentration
Laser induced signal output part connection processing device (10) signal input part, the cosine wave signal of the first signal generator (1)
The signal input part of output terminal connection lock-in amplifier (9), the signal output part connection processing device (10) of lock-in amplifier (9)
Demodulated reference signal input terminal, the demodulation letter of the triangular signal output terminal connection processing device (10) of secondary signal generator (2)
Number input terminal.
2. the gas concentration detection system according to claim 1 based on Wavelength modulation spectroscopy, it is characterised in that：Described
The sine wave signal of one signal generator (1) output and the frequency of cosine wave signal are secondary signal generator (2) output
100 times of the frequency of triangular signal.
3. the gas concentration detection system according to claim 1 based on Wavelength modulation spectroscopy, it is characterised in that：Described
One signal generator (1) output sine wave signal and cosine wave signal frequency it is equal, and frequency range be 100Hz~
100kHz；The frequency range of the triangular signal of secondary signal generator (2) output is 1Hz~1kHz.
4. the gas concentration detection system according to claim 1 based on Wavelength modulation spectroscopy, it is characterised in that：It is described to add
The signal output part output sine wave of musical instruments used in a Buddhist or Taoist mass (3) and the superposed signal of triangular wave enter pulse width modulator (4), pulse width modulator
(4) non-inverting input pulse-width signal is carried out to above-mentioned superposed signal.
5. the gas concentration detection system according to claim 1 based on Wavelength modulation spectroscopy, it is characterised in that：Described point
It is 1650 that cloth feedback laser (6), which is used for the laser signal entrance port output wavelength scope of gas concentration detection gas chamber (7),
The laser of~1656nm.
6. the gas concentration detection system according to claim 1 based on Wavelength modulation spectroscopy, it is characterised in that：The gas
Under test gas in bulk concentration detection gas chamber (7) absorbs the light intensity of incident laser, the gas concentration detection gas chamber (7)
Laser signal exit wound of bullet output light intensity weaken laser signal.
7. the gas concentration detection system according to claim 1 based on Wavelength modulation spectroscopy, it is characterised in that：It is described to swash
Optical detector (8) is used to detect the laser signal of gas concentration detection gas chamber (7) laser signal exit wound of bullet output, and defeated
Go out the laser induced electric signal of microvolt level and give processor (10).
8. the gas concentration detection system according to claim 7 based on Wavelength modulation spectroscopy, it is characterised in that：Above-mentioned place
Manage the second harmonic utilization that device (10) is used for the light intensity signal after being absorbed to the under test gas in the laser induced electric signal of microvolt level
Demodulated reference signal and triangular signal carry out locking amplification demodulation, obtain and the concentration dependent magnitude of voltage of under test gas, the electricity
Pressure value is the peak-to-peak value of second harmonic signal, and then the concentration value with the under test gas of concentration known is normalized, and obtains
To multigroup voltage signal and the correspondence of under test gas concentration, which is the peak-to-peak value of second harmonic signal, will be multigroup
Voltage signal and the correspondence of under test gas concentration are normalized to obtain above-mentioned second harmonic and under test gas concentration
Corresponding equation.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN107478601A (en) * | 2017-09-15 | 2017-12-15 | 江汉大学 | Gas concentration detection system and detection method based on Wavelength modulation spectroscopy |
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| CN107478601A (en) * | 2017-09-15 | 2017-12-15 | 江汉大学 | Gas concentration detection system and detection method based on Wavelength modulation spectroscopy |
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