CN103175790A - Double-quartz-crystal-oscillator spectral phonometer and gas detection device employing same - Google Patents
Double-quartz-crystal-oscillator spectral phonometer and gas detection device employing same Download PDFInfo
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- CN103175790A CN103175790A CN2013100423459A CN201310042345A CN103175790A CN 103175790 A CN103175790 A CN 103175790A CN 2013100423459 A CN2013100423459 A CN 2013100423459A CN 201310042345 A CN201310042345 A CN 201310042345A CN 103175790 A CN103175790 A CN 103175790A
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Abstract
The invention relates to gas sensing technologies and particularly relates to a double-quartz-crystal-oscillator spectral phonometer and a gas detection device employing the same. The gas detection device is used for solving the technical problems of low sensitivity and cumbersomeness in operation of existing gas detection devices. The double-quartz-crystal-oscillator spectral phonometer comprises a gas chamber, wherein the gas chamber is located outside a double-quartz-crystal-oscillator assembly, and the bottom of the gas chamber is provided with a hole; an entrance window and an exit window are respectively formed in a sidewall of the gas chamber along a light path; and the entrance window, the double-quartz-crystal-oscillator assembly and the exit window are located on the same light path. The gas detection device comprises a light source and a light source driver connected with the light source; and a light beam focusing device and the spectral phonometer are sequentially arranged on an exit light path of the light source. The gas detection device further comprises a first phase-locked amplifier and a signal generator which are sequentially connected with each other. According to the spectral phonometer and the gas detection device, through the ingenious arrangement of the double-quartz-crystal-oscillator assembly, the technical problems in current gas detection that the detection sensitivity is low and the frequency of quartz crystal oscillators is required for being measured frequently are solved.
Description
Technical field
The present invention relates to the gas sensing technology, be specially a kind of biquartz crystal oscillator spectrophone and adopt the gas detection apparatus of this acousimeter.
Background technology
Gas molecule is present in human lives's whole space, with the mankind's economy, commecial activity, healthy etc. closely bound up.Along with the continuous acceleration of Chinese Industrialization process, the impact that the discharge of a large amount of poisonous hazardous gases is serious the mankind's healthy and existence.In the fields such as oil, chemical industry, space flight, medical science, environment, need to carry out the monitoring of high precision high selectivity to derivative gas molecule, to optimize various industrial processs simultaneously.Gas detection technology based on molecular spectroscopy, due to advantages such as it are highly sensitive, selectivity is good, can detect in real time online, is subject to people's attention in recent years gradually.Especially optoacoustic spectroscopy, characteristic optical source wavelength non-selectivity and detection sensitivity are directly proportional to power with it, be widely used especially.Within 2002, Rice Univ USA's laser science group takes the lead in using quartz tuning-fork to replace the microphone in traditional optoacoustic spectroscopy, and gas is surveyed, and device volume is dwindled greatly, has obtained good effect.This device core probe portion mainly is comprised of a tuning-fork type quartz crystal oscillator and two tubules.The front elevation that Fig. 7 is the tuning-fork type quartz crystal oscillator, the tuning-fork type quartz crystal oscillator has two and raises one's arm, the tuning-fork type quartz crystal oscillator is after being subject to external drive, raise one's arm along arrow direction double vibrations in figure, for convenience of description the upper face vertical with direction of vibration of raising one's arm of tuning-fork type quartz crystal oscillator is called to inside and outside vibration plane; The face parallel with direction of vibration (being face and the face behind of seeing on paper) is called the side of raising one's arm of tuning-fork type quartz crystal oscillator; Two gaps between raising one's arm are called the gap of raising one's arm, as shown in Figure 7 raise one's arm gap direction upwards.Two electrodes are arranged at tuning-fork type quartz crystal oscillator bottom, and each connects a pin, and a pin is connected with signal ground, and another pin is the electric signal because of generation of vibration for output.Two tubules tuning-fork type quartz crystal oscillator both sides that are placed in, the pipe axle center all and light path coaxial, form miniature sound cavities, light beam from two, raise one's arm after by first tubule between by then by second tubule, tested gas absorption after luminous energy, because the collision de excitation of gas is sent out, discharge acoustic energy, acoustic energy accumulates in miniature sound cavities, pass to again the tuning-fork type quartz crystal oscillator, cause tuning-fork type quartz crystal oscillator two vibration of raising one's arm, and then the tuning-fork type quartz crystal oscillator is converted into electric signal to mechanical vibrational energy by piezoelectric effect, and the intensity of these electric signal just is proportional to the gas concentration be detected.This configuration is called two-tube configuration.Subsequently, for further improving its sensitivity, the physical dimension of two tubules is further optimized.Also have the people only to use an independent long tube as sound cavities, a slit is opened at the long tube middle part, and long tube is equivalent to be divided into two sections, and only surplus sub-fraction connects; The tuning-fork type quartz crystal oscillator is placed on the side at long tube middle part, and the long tube slit is relative with the position, gap of tuning-fork type quartz crystal oscillator, in order to better meet resonant condition, this configuration is called the single tube configuration.But current no matter which kind of configuration, and how by position, the size of conversion resonance lumen and tuning-fork type quartz crystal oscillator, optimized experimental facility, all can't make detection sensitivity further improve, because detection sensitivity has arrived an optimal value under existing device, on the other hand, all there is a weak point in above device, due to the high Q characteristic of tuning-fork type quartz crystal oscillator, (Q refers to the quality factor of quartz crystal oscillator, quality factor=stored energy/per cycle loss of energy, the higher responsive bandwidth of quality factor is narrower), make its responsive bandwidth 2.5Hz that only has an appointment, even lower, and its response frequency can be along with the variation of environmental parameter, temperature for example, humidity, pressure etc. and changing, therefore at every turn when carrying out detection of gas, all must be measured its resonant frequency, and then use its resonant frequency (first harmonic detection) or resonant frequency half (second harmonic detection) to be modulated its light source, otherwise the tuning-fork type quartz crystal oscillator will can not respond the sound wave discharged after gas absorption luminous energy.This makes current gas detection apparatus operation comparatively loaded down with trivial details, and detection efficiency is lower.
Summary of the invention
The present invention is for solving the technical matters that current gas detection apparatus detection sensitivity is not high, operation is comparatively loaded down with trivial details, a kind of biquartz crystal oscillator spectrophone is provided and adopts the gas detection apparatus of this acousimeter.
Biquartz crystal oscillator spectrophone of the present invention is realized by the following technical solutions: a kind of biquartz crystal oscillator spectrophone comprises a biquartz crystal oscillator assembly; Described biquartz crystal oscillator assembly comprises relative arrange and two the tuning-fork type quartz crystal oscillators that have a fixed gap in the gap of raising one's arm, and the side of raising one's arm of described two tuning-fork type quartz crystal oscillators is parallel to each other; Each tuning-fork type quartz crystal oscillator all has a pin to be connected with signal ground; The pin that each tuning-fork type quartz crystal oscillator is not connected with signal ground is connected with a prime amplifier jointly.
During application, light beam passes from the space between two tuning-fork type quartz crystal oscillators.Adopt biquartz crystal oscillator array mode of the present invention to utilize the coupling effect between the tuning-fork type quartz crystal oscillator, their response curve is merged, and the impedance between them reduces, and the Q value further reduces, and modulation frequency range obviously increases, can effectively strengthen detection sensitivity.
Further, described biquartz crystal oscillator assembly also comprise one through described tuning-fork type quartz crystal oscillator between space axially and the tuning-fork type quartz crystal oscillator to the miniature sound cavities of the lateral vertical of raising one's arm; Described miniature sound cavities middle part lateral surface has the slit with the gap parallel aligned of raising one's arm of two tuning-fork type quartz crystal oscillators, among the partial insertion slit of raising one's arm of described two tuning-fork type quartz crystal oscillators.
The tuning-fork type quartz crystal oscillator inserts among slit but does not contact with tube wall.This array mode is at the tuning-fork type quartz crystal oscillator on the basis to coupling, increased miniature sound cavities and tuning-fork type quartz crystal oscillator between coupling, make the Q value further reduce, and modulation frequency range also further increases, detection sensitivity has obtained further raising.Pipe (miniature sound cavities) only is connected by very narrow part in the part perpendicular with the gap direction of raising one's arm.This array mode needs meticulousr machining, because the raise one's arm degree of depth of inserting miniature sound cavities of tuning-fork type quartz crystal oscillator is more shallow, miniature sound cavities and tuning-fork type quartz crystal oscillator between coupling be not very strong, but the center have no occluder of miniature sound cavities, be very easy to carry out beam collimation.
Further, described biquartz crystal oscillator assembly also comprise one through described tuning-fork type quartz crystal oscillator between space axially and the tuning-fork type quartz crystal oscillator to the miniature sound cavities of the lateral vertical of raising one's arm; The lateral surface both sides vertical with the gap direction of raising one's arm, described miniature sound cavities middle part respectively have a slit, among two slits of insertion of raising one's arm all partly of described each tuning-fork type quartz crystal oscillator.
The miniature sound cavities both sides vertical with the gap direction of raising one's arm respectively have a slit, and whole pipe only leaves very narrow part and connects in the both sides relative with the gap of raising one's arm; Raising one's arm of two tuning-fork type quartz crystal oscillators inserted in slit, and superposed raising one's arm inserted the slit of top, and raising one's arm of below inserted the slit of below, and the coupling part of pipe is positioned among the gap of raising one's arm.The tuning-fork type quartz crystal oscillator does not contact with tube wall.This array mode not only possesses all advantages of front a kind of mode, and raises one's arm and can further insert miniature sound cavities due to the tuning-fork type quartz crystal oscillator, and coupling further strengthens; Simultaneously because raising one's arm of two tuning-fork type quartz crystal oscillators is inserted into miniature sound cavities inside from junction, pipe center, light beam passes through between must raising one's arm from two, therefore this array mode not only needs meticulous machining, also needs to carry out careful optical alignment.
Further, described biquartz crystal oscillator assembly also comprises that symmetry is located at the miniature sound cavities be comprised of two single tubes of the axial and lateral vertical of raising one's arm that the tuning-fork type quartz crystal oscillator is right of the right both sides, space of tuning-fork type quartz crystal oscillator.
In fact this array mode is equivalent to a pair of miniature sound cavities and forms a micro resonant cavity, and two tuning-fork type quartz crystal oscillators are equivalent to the inside that enters into micro resonant cavity of part.This array mode does not need meticulous machining, the tuning-fork type quartz crystal oscillator degree of depth of inserting micro resonant cavity of raising one's arm is very dark, make the Q value of whole system to drop to 4000 left and right from 12000 left and right of single sound V shape quartz crystal oscillator, therefore this combination belongs to the strong coupling mode, and modulation band-width is also further widened; Because raising one's arm of two tuning-fork type quartz crystal oscillators is inserted into micro resonant cavity inside, light beam must pass through from two gaps of raising one's arm, and therefore this mode need to be carried out careful optical alignment.
The comparison diagram that Fig. 5 is biquartz crystal oscillator assembly and single quartz crystal oscillator component responds curve.Described single quartz crystal oscillator assembly refers to the parts and the configuration mode thereof that adopt on classic method.In figure, transverse axis is frequency (Hz), and the longitudinal axis is when the external excitation signal, the squared magnitude (arbitrary unit) of single quartz crystal oscillator assembly or biquartz crystal oscillator component responds voltage.The response curve that S1 is single naked tuning-fork type quartz crystal oscillator, responsive bandwidth only has 2.5Hz; S2 is the response curve that single quartz crystal oscillator adds a micro resonant cavity be comprised of two single tubes, and responsive bandwidth is 3.5Hz; The S3 curve is under the third configuration mode mentioned above, the response curve that the combination of two molecular miniature sound cavities of pipe and two tuning-fork type quartz crystal oscillators obtains, because there are the strong coupling effect in two miniature sound cavities and two tuning-fork type quartz crystal oscillators, making responsive bandwidth is 7.4Hz, greatly is wider than the responsive bandwidth of single quartz crystal oscillator assembly.
The comparison diagram of the signal intensity that Fig. 6 is the water in air measured under equal experimental situation of biquartz crystal oscillator assembly and single quartz crystal oscillator assembly.In figure, transverse axis is laser current (mA), and ordinate is signal intensity (V).S1 is the signal amplitude that single sound V shape quartz crystal oscillator is measured; S2 is that single quartz crystal oscillator adds the signal amplitude that a micro resonant cavity (being comprised of two pipes) is measured; S3 is under the third array mode of mentioning above, i.e. two miniature sound cavities and two signal amplitudes that the combination of tuning-fork type quartz crystal oscillator obtains.As can be seen from the figure, the S3 signal is 3 times of S2, is 46 times of S1, and detection sensitivity is significantly improved.
Further, also comprise that a bottom that is positioned at biquartz crystal oscillator assembly outside is provided with the air chamber in hole; Be respectively equipped with an incidence window and an outgoing window along light path on the sidewall of air chamber; Described incidence window, biquartz crystal oscillator assembly and outgoing window are positioned on same light path; Described air chamber upper end is provided with gas access near the position of outgoing window one side; The lower end of air chamber is provided with gas vent near the position of incidence window one side; Described tuning-fork type quartz crystal oscillator and miniature sound cavities are fixed on the inwall of air chamber by the bearing of being located at its underpart; Respective pin on two tuning-fork type quartz crystal oscillators is in parallel and with signal ground and prime amplifier, be connected respectively through behind hole.
While being measured, what gas to be measured was continuous flows into air chamber from gas access, and flows out from gas vent, surveys light outgoing after incidence window, biquartz crystal oscillator assembly and outgoing window; Biquartz crystal oscillator assembly is corresponding electric signal by the acoustic energy Conversion of Energy of sending out generation due to the collision de excitation between molecule after gas absorption luminous energy to be measured and inputs to corresponding analytical equipment by prime amplifier and analyzed.
Gas detection apparatus of the present invention is realized by the following technical solutions: a kind of gas detection apparatus comprises light source and the light source drive be connected with light source; Be provided with in turn light beam focuser and spectrophone on the light source emitting light path; Also comprise the first lock-in amplifier and the signal generator that connect in turn; The modulation signal output terminal of signal generator is connected with the modulation port of light source drive; A synchronous signal output end of signal generator is connected with the synchronous signal input end of the first lock-in amplifier; Also comprise data collecting card and computer system; The signal output part of the first lock-in amplifier is connected with a signal input part of data collecting card; The signal output part of data collecting card is connected with the signal input part of computer system; Described spectrophone adopts biquartz crystal oscillator spectrophone; The signal output part of the prime amplifier of biquartz crystal oscillator spectrophone is connected with the signal input part of the first lock-in amplifier; Described incidence window, biquartz crystal oscillator assembly and outgoing window are positioned on the emitting light path of light beam focuser in turn.
When trace gas is detected, signal generator is with 1/2nd f
0(f
0for biquartz crystal oscillator assembly resonant frequency) frequency output sinusoidal modulation signal to light source drive, the electric current of light source drive is supplied to light source after being modulated by described sinusoidal modulation signal, output light is carried out to wavelength-modulated, the light that light source sends is after biquartz crystal oscillator spectrophone, biquartz crystal oscillator assembly converts the vibration received corresponding electric signal to and this electric signal is passed to prime amplifier, prime amplifier is transferred to the first lock-in amplifier after this electric signal is amplified, the first lock-in amplifier synchronizing signal that the acknowledge(ment) signal generator is sent here is simultaneously carried out the second harmonic demodulation to photo detector signal, the electric signal that includes gas concentration information to be measured demodulated is gathered by data collecting card, data collecting card inputs to computer system by the signal collected, computer system converts the signal received corresponding image to and shows under the support of corresponding software, the concentration of gas to be measured can directly be read from image, the known technology that described corresponding software is those skilled in the art, be easy to write.When certain gas is measured, should by this kind of gas of concentration known, to measurement mechanism, be demarcated in advance, calibrated device just can be measured this kind of gas.Described scaling method is technology known in those skilled in the art.
Further, also comprise gas reference to be measured pond and the photodetector be positioned in turn on biquartz crystal oscillator spectrophone emitting light path; Photodetector is connected with second lock-in amplifier by signal output part, and described the second lock-in amplifier is connected with photodetector by signal input part; Another synchronous signal output end of signal generator is connected with the synchronous signal input end of the second lock-in amplifier, and the signal output part of the second lock-in amplifier is connected with another signal input part of data collecting card; The signal output part of computer system is connected with the modulation port of light source drive.
Gas reference to be measured pond, the second lock-in amplifier, data collecting card and computer system have formed feedback system of the present invention jointly.Be filled with the gas identical with gas componant to be measured in gas reference to be measured pond, entering photodetector by the light of air chamber outgoing through the gas reference pond is laggard, photodetector converts the light signal of acceptance to corresponding electric signal, then give the second lock-in amplifier, the second lock-in amplifier synchronizing signal that the acknowledge(ment) signal generator is sent here is simultaneously carried out the third harmonic demodulation to photo detector signal, obtain the frequency discrimination signal, the frequency discrimination signal is gathered by data collecting card, carry out the PID signal by computer system regular, and adjust the output current of light source drive according to the frequency discrimination signal, by light source drive, control on the tested Absorption Line that laser wavelength remains at gas to be measured, the detection optical wavelength of light source output is higher than the Absorption Line (while being absorption frequency) of gas to be measured, and the electric current that reduces light source drive makes to survey light wavelength to be reduced, when surveying light wavelength lower than the Absorption Line of gas to be measured, the electric current of rising light source drive makes to survey light wavelength and raises, the detection optical wavelength of adjusting so in real time light source output remains on the Absorption Line of gas to be measured.The introducing of feedback system can be locked in the optical wavelength of light source emission on the tested Absorption Line of gas to be measured, has avoided the process that light source must constantly be scanned according to frequency range in the past from low to high, has effectively improved detection efficiency.
The present invention's prime amplifier used, lock-in amplifier, signal generator are the common instrument of this area, have Multiple Type available; Described PID signal is regular is those skilled in the art's methods commonly used.
The invention has the beneficial effects as follows: one, use biquartz crystal oscillator assembly to be surveyed object gas, broken current single quartz crystal oscillator and object gas has been surveyed to the bottleneck that is difficult to further promote sensitivity; Two, the use of biquartz crystal oscillator assembly is not the simple Overlay of signal, but by the tuning-fork type quartz crystal oscillator between and coupling effect between tuning-fork type quartz crystal oscillator pair and miniature sound cavities, make the impedance between them very little, energy can exchange between them, cause biquartz crystal oscillator spectrophone quality factor q to reduce, but signal strengthen on the contrary; Three, when resonant frequency is almost constant, the reduction of quality factor q further increases bandwidth, like this, biquartz crystal oscillator spectrophone can use in very wide modulation frequency range, while having avoided single quartz crystal oscillator to be detected object gas, must frequently measure the technical requirement of its resonant frequency; Four, the introducing of gas reference to be measured pond and feedback system makes optical maser wavelength can rest on all the time the position of tested Absorption Line, and, without to carried out periodic scan by survey line, has improved detection efficiency; Five, the position of gas access and gas vent arranges and can guarantee that tested gas advances from an end of miniature sound cavities, from another of miniature sound cavities, brings out, and gas can be full of rapidly miniature sound cavities like this, reaches the fast detecting purpose.
The accompanying drawing explanation
Fig. 1 is a kind of structure and the pin connection diagram of biquartz crystal oscillator assembly of the present invention while specifically implementing.
Fig. 2 is the second structure and the pin connection diagram of biquartz crystal oscillator assembly of the present invention while specifically implementing.
Fig. 3 is the third structure and the pin connection diagram of biquartz crystal oscillator assembly of the present invention while specifically implementing.
Fig. 4 is gas detection apparatus structural representation of the present invention.
Fig. 5 is for adopting the response curve contrast schematic diagram of Fig. 3 described biquartz crystal oscillator assembly and single quartz crystal oscillator assembly.
Fig. 6 is for adopting the comparison diagram as a result after Fig. 3 described biquartz crystal oscillator assembly and single quartz crystal oscillator assembly are measured water in air vapour under equal experimental situation.
The main TV structure schematic diagram of Fig. 7 tuning-fork type quartz crystal oscillator.
The 1-light source, 2-light beam focuser, the 3-spectrophone, the 4-plane mirror, the 5-concave mirror, 6-gas reference to be measured pond, the 7-photodetector, the 8-prime amplifier, the 9-electro-magnetic shielding cover, the 10-signal generator, 11-the first lock-in amplifier, the 12-computer system, the 13-data collecting card, 14-the second lock-in amplifier, the 15-light source drive, the 31-incidence window, 32-outgoing window, the miniature sound cavities of 33-, the 34-gas vent, the 35-gas access, 36-tuning-fork type quartz crystal oscillator, 37-biquartz crystal oscillator assembly, the 38-air chamber, the 331-slit, 61-the first incidence window, 62-the first outgoing window.
Embodiment
A kind of biquartz crystal oscillator spectrophone, comprise a biquartz crystal oscillator assembly 37; Described biquartz crystal oscillator assembly 37 comprises relative arrange and two the tuning-fork type quartz crystal oscillators 36 that have a fixed gap in the gap of raising one's arm, and the side of raising one's arm of described two tuning-fork type quartz crystal oscillators 36 is parallel to each other; Each tuning-fork type quartz crystal oscillator 36 all has a pin to be connected with signal ground; The pin that each tuning-fork type quartz crystal oscillator 36 is not connected with signal ground is connected with a prime amplifier 8 jointly.
Described biquartz crystal oscillator assembly 37 also comprise one through described tuning-fork type quartz crystal oscillator between space axially and the tuning-fork type quartz crystal oscillator to the miniature sound cavities 33 of the lateral vertical of raising one's arm; Described miniature sound cavities 33 middle part lateral surfaces have the slit 331 with the gap parallel aligned of raising one's arm of two tuning-fork type quartz crystal oscillators 36, among the partial insertion slit 331 of raising one's arm of described two tuning-fork type quartz crystal oscillators 36.As shown in Figure 1.
Described biquartz crystal oscillator assembly 37 also comprise one through described tuning-fork type quartz crystal oscillator between space axially and the tuning-fork type quartz crystal oscillator to the miniature sound cavities 33 of the lateral vertical of raising one's arm; The described miniature sound cavities 33 middle part lateral surfaces both sides vertical with the gap direction of raising one's arm respectively have a slit 331, among two slits of insertion of the part of raising one's arm all of described each tuning-fork type quartz crystal oscillator 36.As shown in Figure 2.
Described biquartz crystal oscillator assembly 37 also comprises that symmetry is located at the miniature sound cavities 33 be comprised of two single tubes of the axial and lateral vertical of raising one's arm that the tuning-fork type quartz crystal oscillator is right of the right both sides, space of tuning-fork type quartz crystal oscillator.As shown in Figure 3.
Also comprise that a bottom that is positioned at biquartz crystal oscillator assembly 37 outsides is provided with the air chamber 38 in hole; Be respectively equipped with an incidence window 31 and an outgoing window 32 along light path on the sidewall of air chamber 38; Described incidence window 31, biquartz crystal oscillator assembly 37 and outgoing window 32 are positioned on same light path; Described air chamber 38 upper ends are provided with gas access 35 near the position of outgoing window 32 1 sides; The lower end of air chamber 38 is provided with gas vent 34 near the position of incidence window 31 1 sides; Described tuning-fork type quartz crystal oscillator 36 and miniature sound cavities 33 are fixed on the inwall of air chamber 38 by the bearing of being located at its underpart; Respective pin on two tuning-fork type quartz crystal oscillators 36 is in parallel and with signal ground and prime amplifier 8, be connected respectively through behind hole.
A kind of gas detection apparatus, comprise light source 1 and the light source drive 15 be connected with light source 1; Be provided with in turn light beam focuser 2 and spectrophone 3 on light source 1 emitting light path; Also comprise the first lock-in amplifier 11 and the signal generator 10 that connect in turn; The modulation signal output terminal of signal generator 10 is connected with the modulation port of light source drive 15; A synchronous signal output end of signal generator 10 is connected with the synchronous signal input end of the first lock-in amplifier 11; Also comprise data collecting card 13 and computer system 12; The signal output part of the first lock-in amplifier 11 is connected with a signal input part of data collecting card 13; The signal output part of data collecting card 13 is connected with the signal input part of computer system 12; Described spectrophone 3 adopts biquartz crystal oscillator spectrophone; The signal output part of the prime amplifier 8 of biquartz crystal oscillator spectrophone is connected with the signal input part of the first lock-in amplifier 11; Described incidence window 31, biquartz crystal oscillator assembly 37 and outgoing window 32 are positioned on the emitting light path of light beam focuser 2 in turn.
Also comprise the gas reference to be measured pond 6 and the photodetector 7 that are positioned in turn on biquartz crystal oscillator spectrophone 3 emitting light paths; Photodetector 7 is connected with second lock-in amplifier 14 by signal output part, and described the second lock-in amplifier 14 is connected with photodetector 7 by signal input part; Another synchronous signal output end of signal generator 10 is connected with the synchronous signal input end of the second lock-in amplifier 14, and the signal output part of the second lock-in amplifier 14 is connected with another signal input part of data collecting card 13; The signal output part of computer system 12 is connected with the modulation port of light source drive 15.
The emitting light path of described biquartz crystal oscillator spectrophone 3 is provided with plane mirror 4, described plane mirror 4 is 45 ° with the emitting light path angulation of biquartz crystal oscillator spectrophone 3, and the reflected light path of plane mirror 4 is provided with a concave mirror 5; Described concave mirror 5 is 45 ° with the emitting light path angulation of plane mirror 4, the emitting light path opposite direction of the emitting light path of described concave mirror 5 and biquartz crystal oscillator spectrophone 3; Described gas reference to be measured pond 6 is positioned on the emitting light path of concave mirror 5.
The incidence window 31 of described biquartz crystal oscillator spectrophone 3 and outgoing window 32 are all non-perpendicular with light path, and described incidence window 31 planes of incidence and light path angulation are 75 ° ~ 85 ° (can select 75 °, 80 °, 85 °); The reverse extending line angulation of the exit facet of described outgoing window 32 and light path is 75 ° ~ 85 ° (can select 75 °, 80 °, 85 °).
The outside of described prime amplifier 8 is provided with an electro-magnetic shielding cover 9.
The incidence window 31 of biquartz crystal oscillator spectrophone 3 and outgoing window 32 are all non-perpendicular with light path, have avoided the light beam feedback, have effectively suppressed the appearance of interference fringe; Electro-magnetic shielding cover 9 can effectively shield electromagnetic noise, avoids introducing outside noise and disturbs; Electro-magnetic shielding cover 9 is generally made by foreign copper-nickel alloy; Electro-magnetic shielding cover 9 connects signal ground, and prime amplifier 8 is placed on from biquartz crystal oscillator spectrophone 3 and is less than in the scope of 10cm.
Plane mirror 4 and concave mirror 5 form one 180 degree light path upset subassembly, can make light path folding, effectively utilize space, and the volume of gas detection apparatus is dwindled greatly; The use of concave mirror 5 makes light beam, by gas reference to be measured pond 6 time, slight converging action be arranged, and has not only avoided the saturated possibility of photodetector 7 of using lens to bring, the shortcoming that photodetector 7 signals of also having avoided free light beam to bring are weak.Light beam enters gas reference to be measured pond 6 by the first incidence window 61, by the first outgoing window 62 outgoing.The first incidence window 61 exit facets become 75 ° of angles with light path, the first outgoing window 62 exit facets and light path angulation are 75 °.
During concrete application, signal generator 10 is with biquartz crystal oscillator spectrophone 3 resonant frequency f
0the frequency values of half (f) sine wave output, by 15 pairs of light sources 1 of light source drive, modulated, modulated light by gas reference to be measured pond 6 after, be converted to corresponding electric signal by photodetector 7 and give the second lock-in amplifier 14, the second lock-in amplifier 14 is gathered by data collecting card 13 after demodulating the 3f signal, giving computer system 12, to carry out PID regular, then delivers to 15 pairs of laser currents of light source drive and compensate, and optical maser wavelength is rested on tested gaseous absorption line all the time.And the tested gas signal that biquartz crystal oscillator spectrophone 3 detects is given the first lock-in amplifier 11 after being amplified by prime amplifier 8, demodulate the 2f signal, by data collecting card 13, gathered, give computer system 12 and shown.
Introduce three kinds of specific embodiment: embodiment 1 as shown in Figure 1 below in conjunction with accompanying drawing, miniature sound cavities is a pipe, in two sides, beats slit, and the width of slit is between 0.35mm-1mm, and the tuning-fork type quartz crystal oscillator is inserted into.This mode needs meticulousr machining, and because the raise one's arm degree of depth of inserting micro resonant cavity of quartz crystal oscillator is more shallow, coupling is not very strong, but the center have no occluder of miniature sound cavities is very easy to carry out beam collimation.
As shown in Figure 3, micro resonant cavity is comprised of two stainless steel tubules embodiment 3, and two tuning-fork type quartz crystal oscillators insert between two pipes relatively, and between two tuning-fork type quartz crystal oscillator end faces, distance is between 0.1mm-1mm.This mode is the equal of that two discrete stainless steel tubules form a micro resonant cavity, therefore do not need meticulous machining, the tuning-fork type quartz crystal oscillator degree of depth of inserting micro resonant cavity of raising one's arm is very dark, make the Q value of whole system to drop to 4000 left and right from 12000 left and right of single sound V shape quartz crystal oscillator, so this strong coupling mode that belongs to, make modulation band-width further widen, because raising one's arm of two tuning-fork type quartz crystal oscillators is inserted into micro resonant cavity inside, light beam passes through between must raising one's arm from two, therefore this mode need to be carried out careful optical alignment.During application, miniature sound cavities length is between 5mm-15mm, and internal diameter is between 0.4mm-1.2mm, and external diameter is between 0.7mm-2mm; The resonant frequency of tuning-fork type quartz crystal oscillator 36 is 32.768kHz.
Claims (10)
1. a biquartz crystal oscillator spectrophone, is characterized in that comprising a biquartz crystal oscillator assembly (37); Described biquartz crystal oscillator assembly (37) comprises relative arrange and two the tuning-fork type quartz crystal oscillators (36) that have a fixed gap in the gap of raising one's arm, and the side of raising one's arm of described two tuning-fork type quartz crystal oscillators (36) is parallel to each other; Each tuning-fork type quartz crystal oscillator (36) all has a pin to be connected with signal ground; The pin that each tuning-fork type quartz crystal oscillator (36) is not connected with signal ground is connected with a prime amplifier (8) jointly.
2. biquartz crystal oscillator spectrophone as claimed in claim 1, it is characterized in that described biquartz crystal oscillator assembly (37) also comprise one through described tuning-fork type quartz crystal oscillator between space axially and the tuning-fork type quartz crystal oscillator to the miniature sound cavities (33) of the lateral vertical of raising one's arm; Described miniature sound cavities (33) middle part lateral surface has the slit (331) with the gap parallel aligned of raising one's arm of two tuning-fork type quartz crystal oscillators (36), among the partial insertion slit (331) of raising one's arm of described two tuning-fork type quartz crystal oscillators (36).
3. biquartz crystal oscillator spectrophone as claimed in claim 1, it is characterized in that described biquartz crystal oscillator assembly (37) also comprise one through described tuning-fork type quartz crystal oscillator between space axially and the tuning-fork type quartz crystal oscillator to the miniature sound cavities (33) of the lateral vertical of raising one's arm; The lateral surface both sides vertical with the gap direction of raising one's arm, described miniature sound cavities (33) middle part respectively have a slit (331), among two slits of insertion of raising one's arm all partly of described each tuning-fork type quartz crystal oscillator (36).
4. many quartz crystal oscillators spectrophone as claimed in claim 1, is characterized in that described biquartz crystal oscillator assembly (37) also comprises that symmetry is located at the miniature sound cavities (33) be comprised of two single tubes of the axial and lateral vertical of raising one's arm that the tuning-fork type quartz crystal oscillator is right of the right both sides, space of tuning-fork type quartz crystal oscillator.
5. biquartz crystal oscillator spectrophone as described as any one in claim 1 ~ 4, characterized by further comprising one and be positioned at the air chamber (38) that the outside bottom of biquartz crystal oscillator assembly (37) is provided with hole; Be respectively equipped with an incidence window (31) and an outgoing window (32) along light path on the sidewall of air chamber (38); Described incidence window (31), biquartz crystal oscillator assembly (37) and outgoing window (32) are positioned on same light path; Described air chamber (38) upper end is provided with gas access (35) near the position of outgoing window (32) one sides; The lower end of air chamber (38) is provided with gas vent (34) near the position of incidence window (31) one sides; Described tuning-fork type quartz crystal oscillator (36) and miniature sound cavities (33) are fixed on the inwall of air chamber (38) by the bearing of being located at its underpart; Respective pin on two tuning-fork type quartz crystal oscillators (36) is in parallel also to be connected with signal ground and prime amplifier (8) respectively through behind hole.
6. a gas detection apparatus, comprise light source (1) and the light source drive (15) be connected with light source (1); Be provided with in turn light beam focuser (2) and spectrophone (3) on light source (1) emitting light path; Also comprise the first lock-in amplifier (11) and the signal generator (10) that connect in turn; The modulation signal output terminal of signal generator (10) is connected with the modulation port of light source drive (15); A synchronous signal output end of signal generator (10) is connected with the synchronous signal input end of the first lock-in amplifier (11); Also comprise data collecting card (13) and computer system (12); The signal output part of the first lock-in amplifier (11) is connected with a signal input part of data collecting card (13); The signal output part of data collecting card (13) is connected with the signal input part of computer system (12); It is characterized in that described spectrophone (3) adopts biquartz crystal oscillator spectrophone as claimed in claim 5; The signal output part of the prime amplifier (8) of biquartz crystal oscillator spectrophone is connected with the signal input part of the first lock-in amplifier (11); Described incidence window (31), biquartz crystal oscillator assembly (37) and outgoing window (32) are positioned on the emitting light path of light beam focuser (2) in turn.
7. gas detection apparatus as claimed in claim 6, is characterized in that, also comprises the gas reference to be measured pond (6) and the photodetector (7) that are positioned in turn on biquartz crystal oscillator spectrophone (3) emitting light path; Photodetector (7) is connected with second lock-in amplifier (14) by signal output part, and described the second lock-in amplifier (14) is connected with photodetector (7) by signal input part; Another synchronous signal output end of signal generator (10) is connected with the synchronous signal input end of the second lock-in amplifier (14), and the signal output part of the second lock-in amplifier (14) is connected with another signal input part of data collecting card (13); The signal output part of computer system (12) is connected with the modulation port of light source drive (15).
8. gas detection apparatus as claimed in claim 7, it is characterized in that, the emitting light path of described biquartz crystal oscillator spectrophone (3) is provided with plane mirror (4), described plane mirror (4) is 45 ° with the emitting light path angulation of biquartz crystal oscillator spectrophone (3), and the reflected light path of plane mirror (4) is provided with a concave mirror (5); Described concave mirror (5) is 45 ° with the emitting light path angulation of plane mirror (4), the emitting light path opposite direction of the emitting light path of described concave mirror (5) and biquartz crystal oscillator spectrophone (3); Described gas reference to be measured pond (6) is positioned on the emitting light path of concave mirror (5).
9. gas detection apparatus as described as any one in claim 6 ~ 8, it is characterized in that, incidence window (31) and the outgoing window (32) of described biquartz crystal oscillator spectrophone (3) are all non-perpendicular with light path, and described incidence window (31) plane of incidence and light path angulation are 75 ° ~ 85 °; The exit facet of described outgoing window (32) and light path reverse extending line angulation are 75 ° ~ 85 °.
10. gas detection apparatus as described as any one in claim 6 ~ 8, is characterized in that, the outside of described prime amplifier (8) is provided with an electro-magnetic shielding cover (9).
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