CN104792729B - Hand-held laser gas concentration monitor and its control method - Google Patents
Hand-held laser gas concentration monitor and its control method Download PDFInfo
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- CN104792729B CN104792729B CN201510152780.6A CN201510152780A CN104792729B CN 104792729 B CN104792729 B CN 104792729B CN 201510152780 A CN201510152780 A CN 201510152780A CN 104792729 B CN104792729 B CN 104792729B
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Abstract
The present invention provides a kind of hand-held laser gas concentration monitor and its control method, the monitor includes handheld main machine, gas chamber and gas chamber connecting rod；Handheld main machine is connected with gas chamber by gas chamber connecting rod；The handheld main machine includes laser light source, the signal acquisition module being connected with gas chamber, the signal processing module being connected with signal acquisition module, laser light source current control module between laser light source and signal processing module, the first temperature sensor, second temperature sensor and the temperature compensation module and display module being connected respectively with signal processing module；First temperature sensor and temperature compensation module are located in laser light source, and second temperature sensor is fixed in handheld main machine.The present invention is based on tunable diode laser absorption spectroscopy technologies to measure gas concentration, while carrying out temperature-compensating to laser light source, stabilizes Output of laser wavelength, and current environmental temperature participates in gas concentration operation, realizes the accurate measurement to gas concentration.
Description
Technical field
The invention belongs to laser gas sensor field, it is related to a kind of hand-held laser gas concentration monitor and its controlling party
Method.
Background technology
In modern production, life, as the improvement of people's living standards, the mankind also get over the requirement that ecological environment purifies
Come it is higher, therefore for the pernicious gas in air it is real-time detection be particularly important.Especially as necks such as coal and chemical industry
Domain is a problem to be solved toxic, pernicious gas monitoring and prediction in air.And laser gas sensor is in this field
Application and research be vigorously developed.
Laser Modulation absorption spectroscopy techniques sensor has occurred, and advantage includes high certainty of measurement, fast response time etc.,
It is gradually applied in each monitoring field.
Based on the sensor utilizes gas near-infrared absorption spectrum technology, gas absorption spectra has been screened, has been used point
For cloth feedback laser as light source, PIN photodiode is to receive.Photodiode receives the laser signal exported from gas chamber
Afterwards, it is translated into electric signal and carries out signal processing, by the variation through laser intensity before and after gas chamber, extrapolate the dense of gas
Degree, final output gas concentration data.And in the prior art, in the process of work, temperature can change laser, cause
The drift of Output of laser wavelength, and the calculating that room temperature participates in gas concentration is usually chosen, bring error to result of calculation.
Invention content
In consideration of it, the present invention provides a kind of hand-held laser gas concentration monitor and its control methods, it is therefore intended that steady
Determine Output of laser wavelength, current environmental temperature participates in gas concentration operation, realizes the accurate measurement to gas concentration.
To achieve the above object, the present invention adopts the following technical scheme that：
On the one hand, a kind of hand-held laser gas concentration monitor provided in an embodiment of the present invention, including handheld main machine, gas
Room and gas chamber connecting rod；The handheld main machine is connected with gas chamber by the gas chamber connecting rod；The handheld main machine packet
Laser light source is included, the signal acquisition module being connected with the gas chamber, the signal processing module being connected with the signal acquisition module,
Laser light source current control module between the laser light source and signal processing module, respectively with the signal processing mould
Block connected the first temperature sensor, second temperature sensor and temperature compensation module and display module；First temperature
Sensor and temperature compensation module are located in laser light source, and second temperature sensor is fixed in handheld main machine.
Further, the handheld main machine further includes proportional-integral derivative controller, is mended for controlling the temperature
It repays module and accurate temperature-compensating is carried out to laser light source.
Further, the laser light source current control module includes that triangular current generator and sine-wave current occur
Device, the sine-wave current that the triangular current and sine-wave current generator that the triangular current generator generates generate is through adding
Musical instruments used in a Buddhist or Taoist mass is input to the laser light source, and the triangular current is for scanning absorption line, and the sine-wave current is for carrying out
High frequency modulated.
Further, the signal acquisition module includes the photodetector being connect with the gas chamber, for believing laser
Number be converted to electric signal；
The preamplifier being connect with the photodetector, for amplifying faint electric signal；
The filter capacitor being connect with the preamplifier for isolated DC signal and filters out low-frequency noise；
The bandpass filter being connect with the filter capacitor, for filtering out out-of-band noise；
Analog-digital converter between the bandpass filter and signal processing module；
Lock-in amplifier between the preamplifier and analog-digital converter, for providing second harmonic signal；
And
The filter inductance that one end is connect with the bandpass filter and analog-digital converter is made an uproar for further filtering out low frequency
Sound.
Further, the handheld main machine further includes rechargeable battery, for being supplied to each module in the handheld main machine
Electricity.
Further, the gas chamber is light optical coupling gas chamber, including gas chamber outer tube, optical fiber at gas chamber outer tube both ends is arranged
Collimator and the light flange on optical fiber collimator；It is provided with venthole on the gas chamber outer tube wall.
On the other hand, the control method of a kind of hand-held laser gas concentration monitor provided in an embodiment of the present invention, including
Following steps：
Signal processing module is by the temperature of the first temperature sensor measurement laser light source, by measured temperature and preset temperature
After relatively, heats up or cool down to laser light source by temperature compensation module, and front ring is worked as by second temperature sensor measurement
Border temperature；
Signal processing module drives laser light source to carry out Laser Modulation length scanning by laser light source current control module；
Signal acquisition module receives the laser signal exported from gas chamber, and signal acquisition is carried out to it；
Signal processing module receives the signal of signal acquisition module acquisition, carries out gas concentration calculating；
Signal processing module is shown gas concentration calculating result by display module.
Further, the signal acquisition module receives the laser signal exported from gas chamber, and signal acquisition packet is carried out to it
It includes：
Photodetector receives the laser signal exported from gas chamber, is converted into electric signal；
Preamplifier is amplified faint electric signal；
Filter capacitor isolation amplifies the direct current signal in electric signal and filters out low-frequency noise；
Bandpass filter filters out the out-of-band noise in amplification electric signal；
Filter inductance further filters out the low-frequency noise in amplification electric signal；
Lock-in amplifier generates second harmonic signal；
Analog-digital converter is to the electric signal and second harmonic signal progress analog-to-digital conversion after filtering out noise.
Further, before the progress gas concentration calculating, further include：
The frequency of signal processing module Automatic-searching absorption peak, and calculate the transmissivity of laser under the frequency.
Further, further include：
When holding laser gas concentration monitor without operation more than preset time, signal processing module breaks rechargeable battery
Electricity.
Compared with prior art, it is the advantages of technical solution of the present invention：
A kind of hand-held laser gas concentration monitor provided by the invention and its control method are swashed based on tunable semiconductor
Optical absorption spectra technology measurement gas concentration, high certainty of measurement, fast response time, while by temperature compensation module to laser light
Source carries out temperature-compensating, stabilizes Output of laser wavelength, and current environmental temperature participates in gas concentration operation, realizes dense to gas
The accurate measurement of degree.
Description of the drawings
Exemplary embodiments of the present invention will be described in detail referring to the drawings by general below, makes those skilled in the art
The above-mentioned and other feature and advantage for becoming apparent from the present invention, in attached drawing：
Fig. 1 is the structure diagram for the hand-held laser gas concentration monitor that the embodiment of the present invention one provides；
Fig. 2 is the structural schematic diagram for the hand-held laser gas concentration monitor that the embodiment of the present invention one provides；
Fig. 3 is the structural schematic diagram of hand-held laser gas concentration monitor provided by Embodiment 2 of the present invention；
Fig. 4 is the flow chart of the control method for the hand-held laser gas concentration monitor that the embodiment of the present invention three provides.
Specific implementation mode
To make the object, technical solutions and advantages of the present invention clearer, hereinafter with reference to attached in the embodiment of the present invention
Figure, technical scheme of the present invention is clearly and completely described by embodiment, it is clear that described embodiment is the present invention one
Section Example, instead of all the embodiments.Based on the embodiments of the present invention, those of ordinary skill in the art are not doing
Go out the every other embodiment obtained under the premise of creative work, shall fall within the protection scope of the present invention.
Embodiment one
Fig. 1 gives the structure diagram of the hand-held laser gas concentration monitor of the offer of the embodiment of the present invention one；Fig. 2 is provided
The structural schematic diagram for the hand-held laser gas concentration monitor that the embodiment of the present invention one provides, the present embodiment can be used for underground
The gas concentration of environment is monitored, and is suitable for a variety of to steam, methane, carbon monoxide, carbon dioxide, hydrogen sulfide, ammonia etc.
The detection of gas.As shown in Figure 1 and Figure 2, the hand-held laser gas concentration monitor include handheld main machine 10, gas chamber 12 and
Gas chamber connecting rod 11；Handheld main machine 10 and gas chamber 12 are connected by gas chamber connecting rod 11；Handheld main machine 10 includes laser light
Source 20, the signal acquisition module 21 being connected with gas chamber 12, the signal processing module 22 being connected with signal acquisition module 21 are located at and swash
Laser light source current control module 23 between radiant 20 and signal processing module 22, is connected with signal processing module 22 respectively
The first temperature sensor 24, second temperature sensor 25 and temperature compensation module 27 and display module 27；First temperature passes
Sensor 24 and temperature compensation module 27 are located in laser light source 20, and second temperature sensor 25 is fixed in handheld main machine.
Wherein, gas chamber 12 carries out spectral absorption under test gas to laser, which hangs over longer gas chamber connection
The front end of bar 11 has ensured instrument and the safety of personnel；Signal acquisition module 21 is used to receive the laser signal exported from gas chamber,
Signal acquisition is carried out to it；Signal processing module 22 is used to control laser light source current control module 23 and changes laser light source 20
Electric current is controlled, the first temperature sensor 24 of processing, the temperature signal of second temperature sensor 25 and signal acquisition module 21 export
Gas concentration signal, and by internal algorithm, calculate gas concentration, gas concentration data be finally output to display module
27；Temperature compensation module 27 is used to heat up or cool down to laser light source 20；First temperature sensor 24 is used for laser light source
20 temperature, second temperature sensor 25 is for measuring current environmental temperature.
Wherein, semiconductor laser, optical fiber laser etc. can be used in laser light source 20.Illustratively, the present embodiment is directed to
Absorption spectra of methane, using the distributed feed-back butterfly laser of wavelength near 1653nm as laser light source 20.Handheld main machine
There is panel outside 10, embeds display module 27 on panel and segment encode liquid crystal display can be used in switch key, wherein display module 27, the liquid
Crystalline substance screen is connect by winding displacement with signal processing module 22, is driven using the driving of M3 pins or MSP430；Liquid can be used in the present embodiment
Signal processing module 22 and interface are placed in the crystalline substance screen back side, and data are sent to segment encode liquid by interface by signal processing module 22
Crystalline substance screen, is shown by segment encode liquid crystal display, and wherein the interface installation with clamp can be used in interface；The segment encode liquid crystal display shows interior
Appearance includes：Gas concentration, environment temperature and abnormality, 22 pre-set gas concentration abnormality numerical value of signal processing module, if occurring
It is abnormal, then "abnormal" part is lighted, remaining does not show.There are rechargeable battery, the rechargeable battery sharp to holding in handheld main machine 10
Each module for power supply of light gas concentration monitoring instrument.
In addition, there are three connectors in handheld main machine 10：One is light source output connector, and light source output connector can connect placement
Light flange, light flange export two tail optical fiber connectors and are respectively output light connector and receive light connector, and FC/APC optical fiber can be used to connect
Head connection gas chamber connecting rod 11, optical fiber is located in gas chamber connecting rod 11, and other end is connected by mounting flange with gas chamber 12；Host
Upper second connector is charging connector, and third connector is switch contacts.
Illustratively, ARM microprocessor can be used in the signal processing module 22 of the present embodiment；First temperature sensor 24,
PT100 thermistors can be used in second temperature sensor 25；TEC (Thermoelectric can be used in temperature compensation module 27
Cooler, thermoelectric cooler) chip, the present embodiment uses the TEC chips of model max1978, to control deviation signal.
The hand-held laser gas concentration monitor that the embodiment of the present invention one provides is based on tunable semiconductor laser absorption light
Spectral technology measures gas concentration, high certainty of measurement, fast response time, while carrying out temperature to laser light source by temperature compensation module
Degree compensation, stabilizes Output of laser wavelength, and current environmental temperature participates in gas concentration operation, realizes to the accurate of gas concentration
It measures.
Embodiment two
Fig. 3 gives the structural schematic diagram of hand-held laser gas concentration monitor provided by Embodiment 2 of the present invention, such as Fig. 3
It is shown, with the embodiment of the present invention one it is different be：
Handheld main machine further includes proportional-integral derivative controller 30, for controlling temperature compensation module 27 to laser light
Source 20 carries out accurate temperature-compensating.
Specifically, proportional-integral derivative controller 30 according to given value V+ and output valve v-shaped at control deviation △,
Ratio P, the integral I and differential D of deviation constitute controlled quentity controlled variable by linear combination, control controlled device.
In addition, in the present embodiment, laser light source current control module includes triangular current generator 31 and sine wave electricity
Flow-generator 32, the sine wave that the triangular current and sine-wave current generator 32 that triangular current generator 31 generates generate
Electric current is input to laser light source through adder 33, wherein triangular current makes laser frequency scanning warp for driving laser light source
Absorption line is crossed, sine-wave current is for carrying out high frequency modulated.At this point, the change of laser light source operating current can change simultaneously it is sharp
Luminous intensity and laser frequency, can according at absorption peak respective frequencies input laser intensity and transmission laser light intensity and temperature survey
Go out gas concentration.
In the present embodiment, signal acquisition module includes the photodetector 34 being connect with gas chamber 12, is used for laser signal
Be converted to electric signal；
The preamplifier 35 being connect with photodetector 34, for amplifying faint electric signal；
The filter capacitor 36 being connect with preamplifier 35 for isolated DC signal and filters out low-frequency noise；
The bandpass filter 37 being connect with filter capacitor 36, for filtering out out-of-band noise；
Analog-digital converter 38 between bandpass filter 37 and signal processing module 22；
Lock-in amplifier 40 between the preamplifier 35 and analog-digital converter 38, for providing second harmonic
Signal；And
The filter inductance 39 that one end is connect with bandpass filter 37 and analog-digital converter 38, makes an uproar for further filtering out low frequency
Sound.
In the present embodiment, the signal exported through preamplifier 35 is divided into two-way, is generated all the way by lock-in amplifier 40
Second harmonic signal, second harmonic signal are received after analog-to-digital conversion by signal processing module 22, and signal processing module 22 extracts
The gas concentration information carried in second harmonic signal, calculates gas concentration, wherein the reference signal of lock-in amplifier 40 by
Sine-wave current generator 32 provides, and is 2 times of real gas concentration by the calculated gas concentration of second harmonic signal；
Another way signal filtered capacitance 36, bandpass filter 37 and filter inductance 39 successively, have filtered out low-frequency noise, then through mould
It is received by signal processing module 22 after number conversion, signal processing module 22 extracts the gas concentration information carried in signal, directly
Calculate gas concentration.
Illustratively, gas chamber 12 uses light optical coupling gas chamber, the light optical coupling gas chamber to include gas chamber outer tube, be arranged in gas chamber
The optical fiber collimator at outer tube both ends and the light flange on optical fiber collimator；It is provided with venthole on gas chamber outer tube wall.Photoelectricity
Detector 34 selects PIN photodiode, 1200~1700nm of wavelength response range.
The present embodiment combination various filters, it is final to detect high-frequency absorption signal, significantly reduce laser, photoelectricity is visited
Surveying the self-noise of device influences, and improves the sensitivity of detection.
The other structures of the present embodiment are identical as in the embodiment of the present invention one, and details are not described herein again.
Hand-held laser gas concentration monitor provided by Embodiment 2 of the present invention is based on tunable semiconductor laser absorption light
Spectral technology measures gas concentration, high certainty of measurement, fast response time, while carrying out temperature to laser light source by temperature compensation module
Degree compensation, stabilizes Output of laser wavelength, and current environmental temperature participates in gas concentration operation, realizes to the accurate of gas concentration
It measures, finally by being used cooperatively for filter capacitor, bandpass filter and filter inductance, only detects high-frequency absorption signal, significantly
Ground reduces laser, the self-noise of photodetector influences, and improves the sensitivity of detection.
Embodiment three
Fig. 4 gives the flow of the control method of the hand-held laser gas concentration monitor of the offer of the embodiment of the present invention three
Figure, as shown in figure 4, this method comprises the following steps：
101, signal processing module by measured temperature and is preset by the temperature of the first temperature sensor measurement laser light source
After temperature is compared relatively, heats up or cool down to laser light source by temperature compensation module, and worked as by second temperature sensor measurement
Preceding environment temperature.
The variation of temperature can cause the variation of laser light source output wavelength, influence measurement accuracy.In the step, the first temperature
Sensor is placed on the emitting semiconductor in laser light source, and signal processing module is realized by the first temperature sensor to laser light
The real-time measurement of source temperature, while measured temperature being compared with preset temperature, give laser light source liter by temperature compensation module
Temperature or cooling, make laser light source accurate work on preset wavelength；Second temperature sensor is fixed in handheld main machine, signal
Processing module realizes the real-time measurement to current environmental temperature by second temperature sensor.
Signal processing module continuous acquisition environment temperature from second temperature sensor by bridge circuit, and participate in air
The operation of concentration.
102, signal processing module drives laser light source to carry out Laser Modulation wavelength by laser light source current control module
Scanning.
In the step, signal processing module can export DA controls by RS232 interface to laser light source current control module
Signal processed makes it drive the laser of laser light source output respective wavelength.
103, signal acquisition module receives the laser signal exported from gas chamber, and signal acquisition is carried out to it.
Signal acquisition module receives the laser signal exported from gas chamber, after converting thereof into electric signal, is amplified to it
It is filtered, is finally converted into digital signal and completes signal acquisition.
104, signal processing module receives the signal of signal acquisition module acquisition, carries out gas concentration calculating.
Wherein, it after signal processing module receives the signal that signal acquisition module acquires, according to the temperature data of processing, calculates
Go out gas concentration.
105, signal processing module is shown gas concentration calculating result by display module.
In the step, signal processing module can connect display module by RS-232 interface and show result of calculation.
In the present embodiment, signal acquisition module receives the laser signal exported from gas chamber, and carrying out signal acquisition to it includes
Step 1041~1047：
1041, photodetector receives the laser signal exported from gas chamber, is converted into electric signal；
1042, preamplifier is amplified faint electric signal；
1043, filter capacitor isolation amplifies the direct current signal in electric signal and filters out low-frequency noise；
1044, bandpass filter filters out the out-of-band noise in amplification electric signal；
1045, filter inductance further filters out the low-frequency noise in amplification electric signal；
1046, lock-in amplifier generates second harmonic signal；
1047, analog-digital converter is to the electric signal and second harmonic signal progress analog-to-digital conversion after filtering out noise.
In addition, before carrying out gas concentration calculating, further include：
The frequency of signal processing module Automatic-searching absorption peak, and calculate the transmissivity of laser under the frequency.
When under test gas concentration is relatively low, signal processing module directly handles the signal by bandpass filter, directly counts
Calculate gas concentration.When under test gas concentration is higher, it is dense that the present embodiment uses direct method and Harmonic Method to be combined calculating gas
Degree；Specifically, the second harmonic signal that signal processing module real-time reception lock-in amplifier generates, calculates fitted signal, paints
The curve of fitted signal is made, while real-time reception passes through the signal of bandpass filter, calculates direct measuring signal, drawn out straight
The curve of measuring signal is connect, a new curve is obtained by comparing two curves, the output frequency corresponding to the curve maximum
Rate is the centre frequency of absorption spectrum, according to the variation of light intensity before and after laser light gas chamber, calculates laser under the frequency
Transmissivity.The step eliminates the influence that power changes with bias current.
Finally, signal processing module also achieves the power-off protection function to rechargeable battery.More than preset time, if hand-held
Laser gas concentration monitor powers off rechargeable battery without any operation, signal processing module, makes monitor in a dormant state.
The embodiment of the present invention three is embodiment of the method, and the method for the present invention embodiment and product embodiments belong to same design,
The detail content of not detailed description in embodiment of the method can refer to the said goods embodiment.
The control method for the hand-held laser gas concentration monitor that the embodiment of the present invention three provides is based on tunable semiconductor
Laser absorption spectroscopy measurement gas concentration, high certainty of measurement, fast response time, while by temperature compensation module to laser
Light source carries out temperature-compensating, stabilizes Output of laser wavelength, and current environmental temperature participates in gas concentration operation, realizes to gas
The accurate measurement of concentration only detects high-frequency absorption finally by being used cooperatively for filter capacitor, bandpass filter and filter inductance
Signal significantly reduces the self-noise influence of laser, photodetector, improves the sensitivity of detection.
It is above-mentioned that only the specific embodiment in the present invention is illustrated, but it can not be used as protection scope of the present invention, it is all
Be according to the present invention in design spirit made by equivalent change or modification or equal proportion zoom in or out, be considered as falling
Enter protection scope of the present invention.
Claims (10)
1. a kind of hand-held laser gas concentration monitor, which is characterized in that connected including handheld main machine, gas chamber and gas chamber
Bar；The handheld main machine is connected with gas chamber by the gas chamber connecting rod；The handheld main machine includes laser light source, with institute
The connected signal acquisition module of gas chamber is stated, the signal processing module being connected with the signal acquisition module is located at the laser light
Laser light source current control module between source and signal processing module, the first temperature being connected respectively with the signal processing module
Spend sensor, second temperature sensor and temperature compensation module and display module；First temperature sensor and temperature are mended
It repays module to be located in laser light source, the second temperature sensor is fixed in the handheld main machine；
Wherein, the signal processing module by bridge circuit the continuous acquisition environment temperature from second temperature sensor, and join
With the operation of atmospheric concentration.
2. hand-held laser gas concentration monitor according to claim 1, which is characterized in that the handheld main machine is also wrapped
Proportional-integral derivative controller is included, accurate temperature-compensating is carried out to laser light source for controlling the temperature compensation module.
3. hand-held laser gas concentration monitor according to claim 2, which is characterized in that the laser light source electric current control
Molding block includes triangular current generator and sine-wave current generator, the triangular wave that the triangular current generator generates
The sine-wave current that electric current and sine-wave current generator generate is input to the laser light source, the triangular wave electricity through adder
Stream is for scanning absorption line, and the sine-wave current is for carrying out high frequency modulated.
4. hand-held laser gas concentration monitor according to claim 3, which is characterized in that the signal acquisition module packet
The photodetector being connect with the gas chamber is included, for laser signal to be converted to electric signal；
The preamplifier being connect with the photodetector, for amplifying faint electric signal；
The filter capacitor being connect with the preamplifier for isolated DC signal and filters out low-frequency noise；
The bandpass filter being connect with the filter capacitor, for filtering out out-of-band noise；
Analog-digital converter between the bandpass filter and signal processing module；
Lock-in amplifier between the preamplifier and analog-digital converter, for providing second harmonic signal；And
The filter inductance that one end is connect with the bandpass filter and analog-digital converter, for further filtering out low-frequency noise.
5. hand-held laser gas concentration monitor according to claim 4, which is characterized in that the handheld main machine is also wrapped
Rechargeable battery is included, for each module for power supply in the handheld main machine.
6. according to any hand-held laser gas concentration monitors of claim 1-5, which is characterized in that the gas chamber is light
Optical coupling gas chamber, including gas chamber outer tube, be arranged in the optical fiber collimator at gas chamber outer tube both ends and on optical fiber collimator
Light flange；It is provided with venthole on the gas chamber outer tube wall.
7. a kind of control method of hand-held laser gas concentration monitor, which is characterized in that include the following steps：
Signal processing module is compared measured temperature with preset temperature by the temperature of the first temperature sensor measurement laser light source
After relatively, heats up or cool down to laser light source by temperature compensation module, and current environment temperature is measured by second temperature sensor
Degree；
Signal processing module drives laser light source to carry out Laser Modulation length scanning by laser light source current control module；
Signal acquisition module receives the laser signal exported from gas chamber, and signal acquisition is carried out to it；
Signal processing module receives the signal of signal acquisition module acquisition, carries out gas concentration calculating；
Signal processing module is shown gas concentration calculating result by display module；
Wherein, signal processing module by bridge circuit the continuous acquisition environment temperature from second temperature sensor, and participate in big
The operation of gas concentration.
8. the control method of hand-held laser gas concentration monitor according to claim 7, which is characterized in that the signal
Acquisition module receives the laser signal exported from gas chamber, and carrying out signal acquisition to it includes：
Photodetector receives the laser signal exported from gas chamber, is converted into electric signal；
Preamplifier is amplified faint electric signal；
Filter capacitor isolation amplifies the direct current signal in electric signal and filters out low-frequency noise；
Bandpass filter filters out the out-of-band noise in amplification electric signal；
Filter inductance further filters out the low-frequency noise in amplification electric signal；
Lock-in amplifier generates second harmonic signal；
Analog-digital converter is to the electric signal and second harmonic signal progress analog-to-digital conversion after filtering out noise.
9. the control method of hand-held laser gas concentration monitor according to claim 8, which is characterized in that the progress
Before gas concentration calculates, further include：
The frequency of signal processing module Automatic-searching absorption peak, and calculate the transmissivity of laser under the frequency.
10. the control method of hand-held laser gas concentration monitor according to claim 9, which is characterized in that further include：
When holding laser gas concentration monitor without operation more than preset time, signal processing module powers off rechargeable battery.
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| CN101319989A (en) * | 2007-06-08 | 2008-12-10 | 派克森公司 | Gas concentration detection method and apparatus thereof |
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