Laser gas detection device

Abstract

The utility model discloses a laser gas detection device which comprises a laser, a reference measurement detector, a power supply circuit, a laser driving circuit, a laser temperature control circuit, a measurement reference signal acquisition circuit and a data processing circuit, and the laser driving circuit, the laser temperature control circuit and the measurement reference signal acquisition circuit are connected with the data processing circuit. The output end of the laser driving circuit is connected with the laser and modulates the laser, the laser is used for generating a laser beam and enabling the laser beam to sequentially pass through the measurement gas chamber and the reference gas chamber, the laser temperature control circuit is connected with a TEC of the laser and controls the temperature of the laser, and the measurement reference signal acquisition circuit is connected with the measurement reference detector. And the reference measurement detector is used for receiving an optical signal emitted after sequentially passing through the measurement gas chamber and the reference gas chamber and converting the optical signal into an electric signal. According to the utility model, the complexity of an external optical path structure is greatly simplified, the circuit structure of the optical module is also simplified, and the cost is reduced.

Description

TECHNICAL FIELD

[0001] The utility model belongs to gas detection technical field, specifically relates to a laser gas detection device. BACKGROUND

[0002] TDLAS technology (Tunable Diode Laser Absorption Spectroscopy, tunable diode laser absorption spectroscopy) and photoacoustic spectroscopy technology (PAS) are based on tunable diode laser, utilize the "frequency selection" characteristics of the measured gas molecules, realize the measurement of the measured gas characteristics. The "frequency selection" characteristics of gas molecules to light wave avoid the cross interference of other irrelevant gas components, become the preferred scheme of current precise real-time online gas detection system, its corresponding speed is fast, the measurement lower limit is low, can realize self-calibration and the characteristics of setting, especially suitable for the measurement of dangerous gas, including methane, carbon monoxide, carbon dioxide, oxygen, ammonia, hydrogen sulfide, acetylene, ethylene and other gases.

[0003] Based on the gas detection scheme and equipment of spectral detection technology, fixed test system, distributed test system, remote test system and various measurement modes have appeared in industrial application field.

[0004] At present, the device for realizing gas online detection based on TDLAS technology and photoacoustic spectroscopy technology (PAS) has the following main technical problems:

[0005] (1) the laser gas detection device used by the real-time online detector of the related art does not have laser temperature control temperature self-detection and self-setting function. That is, when each laser is matched with an optical module, the temperature control temperature point corresponding to the wavelength of the measured gas absorption needs to be manually debugged, which greatly reduces the production efficiency of the sensor and increases the production cost.

[0006] (2) the laser gas detection device used by the real-time online detector of the related art does not have laser light intensity wavelength self-calibration function. According to Beer-Lambert Law, wavelength change and intrinsic light intensity change will cause the change of absorption light intensity, which will lead to the change of gas concentration after inversion. However, the wavelength drift and the change of output light intensity slope efficiency caused by the use of high and low temperature change and the aging of laser will cause the wavelength drift and the change of output light intensity slope efficiency. Therefore, the optical module used by the current gas sensor needs to be calibrated regularly. It cannot work stably and reliably for a long time.

[0007] (3) the external optical path structure of the laser gas detection device used by the real-time online detector of the related technology is that the light beam emitted by the laser is output to the measurement path and the reference path after being split, and then respectively passes through the measurement gas chamber and the reference gas chamber to the measurement path detector and the reference path detector, forming a parallel optical path, the external optical path structure is relatively complex, and the cost is relatively high.

[0008] How to design a laser gas detection device with low cost and good performance has become a technical problem to be solved in the field. Practical new type content

[0009] The utility model aims at at least solving one of the technical problems existing in the prior art, and proposes a laser gas detection device.

[0010] The technical scheme of the utility model is implemented as follows: the utility model discloses a laser gas detection device, comprising:

[0011] A power supply circuit is used to power the whole device.

[0012] A laser is used to generate a laser beam and make the laser beam pass through a measurement gas chamber and a reference gas chamber in turn.

[0013] A laser driver circuit is connected with the laser at the output end, and connected with the first output end of the data processing circuit at the input end.

[0014] A laser temperature control circuit is connected with the TEC of the laser at the output end, and connected with the second output end of the data processing circuit at the input end.

[0015] A reference measurement detector is used to receive the optical signal emitted after passing through the measurement gas chamber and the reference gas chamber in turn, and convert it into an electrical signal.

[0016] A reference measurement signal acquisition circuit comprises a reference measurement transimpedance amplification circuit, the input end of the reference measurement transimpedance amplification circuit is connected with the reference measurement detector, and the output end of the reference measurement transimpedance amplification circuit is connected with the first input end of the data processing circuit.

[0017] Further, the reference measurement signal acquisition circuit further comprises a reference measurement analog phase-locked filter circuit, which is connected between the output end of the reference measurement transimpedance amplification circuit and the second input end of the data processing circuit, and is used to phase-locked filter the electrical signal output by the reference measurement transimpedance amplification circuit and output to the second input end of the data processing circuit.

[0018] Further, the reference measurement transimpedance amplification circuit adopts a transimpedance amplifier.

[0019] Further, the reference measurement analog phase-locked filter circuit is constructed by a phase-locked chip.

[0020] The utility model discloses a kind of laser gas detection devices, comprising:

[0021] Power supply circuit, the power supply circuit is used to power supply to entire device;

[0022] Laser, the laser is used to generate laser beam;

[0023] Optical splitter, the optical splitter is used to divide laser beam output by laser into measurement light and reference light, and measurement light is guided to measurement gas chamber, and reference light is guided to reference gas chamber;

[0024] Laser driver circuit, the output end of the laser driver circuit is connected with laser, and the input end of the laser driver circuit is connected with the first output end of data processing circuit;

[0025] Laser temperature control circuit, the output end of the laser temperature control circuit is connected with the TEC of laser, and the input end of the laser temperature control circuit is connected with the second output end of data processing circuit;

[0026] Measurement probe, the measurement probe is used to receive measurement light after emission after measurement gas chamber, and it is converted into measurement electric signal;

[0027] Reference probe, the reference probe is used to receive reference light after emission after reference gas chamber, and it is converted into reference electric signal;

[0028] Measurement signal acquisition circuit, measurement signal acquisition circuit includes measurement transimpedance amplification circuit, the input end of the measurement transimpedance amplification circuit is connected with measurement probe, and the output end of measurement transimpedance amplification circuit is connected with the first input end of data processing circuit;

[0029] Reference signal acquisition circuit, reference signal acquisition circuit includes reference transimpedance amplification circuit, the input end of the reference transimpedance amplification circuit is connected with reference probe, and the output end of reference transimpedance amplification circuit is connected with the second input end of data processing circuit.

[0030] Further, measurement signal acquisition circuit also includes measurement analog phase-locked filter circuit, measurement analog phase-locked filter circuit is connected between the output end of measurement transimpedance amplification circuit and the first input end of data processing circuit, and the measurement analog phase-locked filter circuit is used to carry out phase-locked filter to electric signal output by measurement transimpedance amplification circuit, and output to the first input end of data processing circuit;

[0031] The reference signal acquisition circuit further comprises a reference analog lock-in filter circuit, which is connected between the output end of the reference transimpedance amplification circuit and the second input end of the data processing circuit, and is configured to perform lock-in filtering on the electrical signal output by the reference transimpedance amplification circuit and output to the second input end of the data processing circuit.

[0032] The output end of the measurement transimpedance amplification circuit or the reference transimpedance amplification circuit is connected with the third input end of the data processing circuit.

[0033] Further, the measurement analog lock-in filter circuit and the reference analog lock-in filter circuit are constructed by using a lock-in chip.

[0034] Further, the analog lock-in filter circuit comprises a lock-in chip, an input pin INP of the lock-in chip is connected with the output end of the measurement transimpedance amplification circuit or the output end of the reference transimpedance amplification circuit, an input pin INN of the lock-in chip is connected with one end of a capacitor C64 and a common-mode voltage output pin VOCM of the lock-in chip, the other end of the capacitor C64 is grounded, an XOUT pin of the lock-in chip is connected with one end of a resistor R27 and one end of a resistor R28, the other end of the resistor R28 is connected with one end of a capacitor C45 and one end of a crystal oscillator X1, the other end of the capacitor C45 is grounded, the other end of the resistor R27 is connected with a clock input pin CLKIN of the lock-in chip, the other end of the crystal oscillator X1 and one end of a capacitor C41, the other end of the capacitor C41 is grounded, an output pin OUTP of the lock-in chip is connected with the first input end or the second input end of the data processing circuit, and a serial clock pin SCLK, a serial data input / output pin SDA, a synchronous output pin SYNCO, a chip selection pin or an address selection pin CS of the lock-in chip are connected with the data processing circuit.

[0035] A boot mode selection pin BOOT of the lock-in chip is grounded.

[0036] Further, the measurement transimpedance amplification circuit and the reference transimpedance amplification circuit both use a transimpedance amplifier.

[0037] Further, the transimpedance amplifier comprises an operational amplifier U2, a non-inverting input end of the operational amplifier U2 is connected with one end of a resistor R7 and one end of a capacitor C11, the other end of the resistor R7 and the other end of the capacitor C11 are grounded, an inverting input end of the operational amplifier U2 is an input end of the transimpedance amplification circuit, configured to receive an electrical signal output by a detector, the inverting input end of the operational amplifier U2 is connected with one end of a resistor R1 and one end of a capacitor C1, the other end of the resistor R1 and the other end of the capacitor C1 are connected with an output end of the operational amplifier U2, and the output end of the operational amplifier U2 is an output end of the transimpedance amplification circuit, configured to output an amplified electrical signal.

[0038] Further, the laser driver circuit comprises the operational amplifier U6 and the operational amplifier U4, the non-inverting input terminal of the operational amplifier U6 is connected with the first output terminal of the data processing circuit through the resistor R12, the inverting input terminal of the operational amplifier U6 is connected with one end of the resistor R9 and one end of the resistor R5 respectively, the other end of the resistor R9 is grounded, the other end of the resistor R5 is connected with the output terminal of the operational amplifier U6, the output terminal of the operational amplifier U6 is connected with the non-inverting input terminal of the operational amplifier U4 through the resistor R11, the non-inverting input terminal of the operational amplifier U4 is connected with one end of the resistor R14, the other end of the resistor R14 is connected with one end of the capacitor C22 and the positive electrode of the laser respectively, the other end of the capacitor C22 is grounded, the inverting input terminal of the operational amplifier U4 is connected with one end of the resistor R2 and one end of the resistor R4 respectively, the other end of the resistor R2 is grounded, the other end of the resistor R4 is connected with the output terminal of the operational amplifier U4, the output terminal of the operational amplifier U4 is connected with one end of the resistor R10, and the other end of the resistor R10 is connected with the positive electrode of the laser.

[0039] Further, the laser gas detection device further comprises a temperature sensor and a pressure sensor, the temperature sensor is used for detecting the temperature of the measurement gas chamber and transmitting to the data processing circuit, and the pressure sensor is used for detecting the pressure of the measurement gas chamber and transmitting to the data processing circuit.

[0040] And / or,

[0041] The reference gas chamber is internally provided with the to-be-measured gas.

[0042] Compared with the prior art, the laser gas detection device has the following beneficial effects:

[0043] The laser gas detection device comprises a reference gas chamber, a reference light path and a reference signal acquisition circuit, and is combined with a laser driver circuit and a laser temperature control circuit, the DAC output component of the MCU data processing circuit is connected with the laser driver circuit to modulate the laser, the DAC output component of the MCU data processing circuit is connected with the laser temperature control circuit to control the temperature of the laser, the reference light signal ADC acquisition component of the MCU data processing circuit is connected with the reference signal acquisition circuit to demodulate the reference photoelectric detector signal, and the wavelength and the light intensity of the laser are self-set and self-calibrated.

[0044] This invention's laser gas detection device uses the total absorbed signal obtained by superimposing the measurement path signal and the reference path signal as the input signal. This significantly simplifies the complexity of the external optical path structure. The parallel optical path, where the laser beam is split and output to the measurement and reference paths, then passes through the measurement and reference gas chambers before reaching the measurement and reference detectors, is simplified to a series optical path where the laser beam passes through the measurement and reference gas chambers and reaches the measurement and reference detectors. Furthermore, by combining the transimpedance amplifier circuits of the measurement and reference detectors into a single transimpedance amplifier circuit, the circuit structure of the optical module is simplified, reducing the cost of the laser gas detection device. Attached Figure Description

[0045] Figure 1 This is a schematic block diagram of the laser gas detection device provided in Embodiment 1 of this utility model;

[0046] Figure 2 This is a schematic diagram of the modulation and demodulation waveforms of the laser gas detection device provided in Embodiment 1 of this utility model;

[0047] Figure 3 A schematic diagram of the first harmonic waveform of the electrical signal output by the transimpedance amplifier circuit provided by this utility model after being filtered by analog phase-locked loop;

[0048] Figure 4 This is a schematic block diagram of a laser gas detection device provided in Embodiment 2 of this utility model;

[0049] Figure 5 This is a schematic diagram of the modulation and demodulation waveforms of the laser gas detection device provided in Embodiment 2 of this utility model;

[0050] Figure 6 This is a schematic diagram of the waveform of the electrical signal output by the transimpedance amplifier circuit provided by this utility model after filtering, fitting, and calculation. Figure 6 In the image, (a) shows a schematic diagram of the waveform after filtering and fitting, and (b) shows a schematic diagram of the waveform of the signal directly absorbed after solving.

[0051] Figure 7 This is a schematic block diagram of another laser gas detection device provided in Embodiment 2 of this utility model;

[0052] Figure 8 This is a schematic diagram of the modulation and demodulation waveforms of the laser gas detection device provided in Embodiment 2 of this utility model;

[0053] Figure 9 A schematic diagram of the second harmonic waveform of the electrical signal output by the transimpedance amplifier circuit provided by this utility model after digital phase-locked loop filtering;

[0054] Figure 10 The principle block diagram of the laser gas detection device provided in the third embodiment of the present application is shown in the figure;

[0055] Figure 11 The modulation and demodulation waveform schematic diagram of the laser gas detection device provided in the third embodiment of the present application is shown in the figure;

[0056] Figure 12 The demodulation waveform schematic diagram of the electric signal output by the transimpedance amplification circuit provided in the third embodiment of the present application after digital filtering, filtering and digital phase-locked filtering is shown in the figure, wherein Figure 12 In the figure, (a) shows the waveform schematic diagram after filtering and fitting, (b) shows the waveform schematic diagram of the direct absorption signal after calculation, and (c) shows the second harmonic waveform schematic diagram after digital phase-locked filtering;

[0057] Figure 13 The circuit diagram of the laser driver circuit provided in the first embodiment of the present application is shown in the figure;

[0058] Figure 14 The circuit diagram of the laser temperature control circuit provided in the first embodiment of the present application is shown in the figure;

[0059] Figure 15 The circuit diagram of the transimpedance amplification circuit provided in the first embodiment of the present application is shown in the figure;

[0060] Figure 16 The circuit diagram of the analog phase-locked filtering circuit provided in the first embodiment of the present application is shown in the figure;

[0061] Figure 17 The circuit diagram of the power supply circuit provided in the first embodiment of the present application is shown in the figure;

[0062] Figure 18 The circuit diagram of the MCU data processing circuit provided in the first embodiment of the present application is shown in the figure. DETAILED DESCRIPTION

[0063] In order for those skilled in the art to better understand the technical solutions of the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0064] Embodiment One

[0065] Referring to Figures 1 to 3 The present application discloses a laser gas detection device, comprising:

[0066] a power supply circuit for powering the entire device;

[0067] a laser for generating a laser beam;

[0068] a beam splitter for splitting the laser beam output by the laser into a measurement light and a reference light, and guiding the measurement light to the measurement cell and the reference light to the reference cell;

[0069] a laser driving circuit, the output of which is connected to the laser, and the input of which is connected to the first DAC output of the data processing circuit;

[0070] a laser temperature control circuit, the output of which is connected to the TEC and the thermistor of the laser, and the input of which is connected to the second DAC output of the data processing circuit;

[0071] a measurement detector for receiving the measurement light emitted after passing through the measurement cell and converting it into a measurement electrical signal;

[0072] a reference detector for receiving the reference light emitted after passing through the reference cell and converting it into a reference electrical signal;

[0073] a measurement trans-impedance amplification circuit, the input of which is connected to the measurement detector, and the output of which is connected to the input of the measurement analog lock-in filter circuit, for converting the current signal of the measurement detector into a voltage signal and amplifying the signal;

[0074] a reference trans-impedance amplification circuit, the input of which is connected to the reference detector, and the output of which is connected to the input of the reference analog lock-in filter circuit, for converting the current signal of the reference detector into a voltage signal and amplifying the signal;

[0075] a measurement analog lock-in filter circuit, the input of which is connected to the output of the measurement trans-impedance amplification circuit, and the output of which is connected to the first ADC input of the data processing circuit, for performing lock-in filtering on the electrical signal output by the measurement trans-impedance amplification circuit and outputting it to the first ADC input of the data processing circuit for ADC conversion;

[0076] The reference analog phase-locked filter circuit is connected with the output end of the reference trans-impedance amplification circuit, and the output end of the reference analog phase-locked filter circuit is connected with the second ADC input end of the data processing circuit, and the reference analog phase-locked filter circuit is used for phase-locked filtering of the electrical signal output by the reference trans-impedance amplification circuit and outputting to the second ADC input end of the data processing circuit for ADC conversion.

[0077] The output end of the measurement trans-impedance amplification circuit or the reference trans-impedance amplification circuit is connected with the third ADC input end of the data processing circuit.

[0078] Further, the first ADC input end of the data processing circuit is used for receiving the electrical signal output by the measurement end analog phase-locked filter circuit to obtain the measurement end harmonic signal, and the data processing circuit is used for measuring the concentration of the measured gas by using the measurement end harmonic signal.

[0079] The second ADC input end of the data processing circuit is used for receiving the electrical signal output by the reference end analog phase-locked filter circuit to obtain the reference end harmonic signal, and the data processing circuit is used for temperature self-setting and wavelength real-time self-calibration by using the reference end harmonic signal.

[0080] The third ADC input end of the data processing circuit is used for receiving the electrical signal output by the measurement end trans-impedance amplification circuit or the electrical signal output by the reference end trans-impedance amplification circuit to obtain the measurement end original absorption signal or the reference end original absorption signal, and the data processing circuit is used for light intensity real-time self-calibration by using the measurement end original absorption signal or the reference end original absorption signal.

[0081] The data processing circuit is used for measuring the concentration of the measured gas by using the measurement end harmonic signal, and specifically includes: when the measurement end harmonic signal is a first harmonic, obtaining the peak-to-peak value A c of the first harmonic signal, the zero-crossing value A c (corresponding to the ordinate, i.e. the baseline), and taking A c / A as the original value of the inversion of the detected gas concentration, and inverting the gas concentration according to the original value of the inversion of the detected gas concentration.

[0082] When the measurement end harmonic signal is a second harmonic, obtaining the peak-to-peak value A c2 of the second harmonic signal, and taking A c2 or A c2 / A as the original value of the inversion of the detected gas concentration.

[0083] Specifically, the zero-crossing point position λ c =(the peak position λ L +the valley position λ H ) / 2.

[0084] The data processing circuit comprises a data processing module, an ADC module and a DAC module, and the data processing module is connected with the ADC module and the DAC module respectively. The first DAC module of the data processing circuit is connected with the laser driver circuit to modulate the laser. The second DAC module of the data processing circuit is also connected with the laser temperature control circuit to control the temperature of the laser. The first ADC module of the data processing circuit is connected with the measurement analog lock filter circuit. The second ADC module of the data processing circuit is connected with the reference analog lock filter circuit.

[0085] In some embodiments, referring to Figure 18 , the data processing module adopts an MCU module, and the ADC module and the DAC module are integrated in the MCU module. Of course, the ADC module and the DAC module can also be located outside the MCU module. The model of the MCU in the embodiment is STM32H743VIT6.

[0086] In some embodiments, the laser driver circuit can adopt a voltage-controlled current source laser driver circuit. Referring to Figure 13 , the laser driver circuit comprises an operational amplifier U6 and an operational amplifier U4, the non-inverting input terminal of the operational amplifier U6 is connected with the first DAC output terminal of the data processing circuit through a resistor R12, the inverting input terminal of the operational amplifier U6 is connected with one end of a resistor R9 and one end of a resistor R5 respectively, the other end of the resistor R9 is grounded, the other end of the resistor R5 is connected with the output terminal of the operational amplifier U6, the output terminal of the operational amplifier U6 is connected with the non-inverting input terminal of the operational amplifier U4 through a resistor R11, the non-inverting input terminal of the operational amplifier U4 is connected with one end of a resistor R14, the other end of the resistor R14 is connected with one end of a capacitor C22 and the positive electrode of the laser respectively, the other end of the capacitor C22 is grounded, the inverting input terminal of the operational amplifier U4 is connected with one end of a resistor R2 and one end of a resistor R4 respectively, the other end of the resistor R2 is grounded, the other end of the resistor R4 is connected with the output terminal of the operational amplifier U4, the output terminal of the operational amplifier U4 is connected with one end of a resistor R10, and the other end of the resistor R10 is connected with the positive electrode of the laser.

[0087] In some embodiments, referring to Figure 14 , the laser temperature control circuit uses ADN8834 as a temperature control chip to construct the circuit.

[0088] In some embodiments, referring to Figure 15Both the measurement-end and reference-end transimpedance amplifier circuits employ transimpedance amplifiers. Each transimpedance amplifier includes operational amplifier U2. The non-inverting input of operational amplifier U2 is connected to one end of resistor R7 and one end of capacitor C11, respectively. The other ends of resistor R7 and capacitor C11 are grounded. The inverting input of operational amplifier U2 serves as the input of the transimpedance amplifier circuit, used to receive the electrical signal output by the detector. The inverting input of operational amplifier U2 is connected to one end of resistor R1 and one end of capacitor C1, respectively. The other ends of resistor R1 and capacitor C1 are connected to the output of operational amplifier U2. The output of operational amplifier U2 serves as the output of the transimpedance amplifier circuit, used to output the amplified electrical signal.

[0089] In some embodiments, see Figure 16 The reference analog phase-locked filter circuit and the measurement analog phase-locked filter circuit are both constructed using phase-locked chips. The analog phase-locked loop (PLL) filter circuit includes a PLL chip. The input pin INP of the PLL chip is connected to the output of the measurement-side transimpedance amplifier circuit or the reference-side transimpedance amplifier circuit. The input pin INN of the PLL chip is connected to one end of capacitor C64 and the common-mode voltage output pin VOCM of the PLL chip. The other end of capacitor C64 is grounded. The XOUT pin of the PLL chip is connected to one end of resistor R27 and one end of resistor R28. The other end of resistor R28 is connected to one end of capacitor C45 and one end of crystal oscillator X1. The other end of capacitor C45 is grounded. The other end of resistor R27 is connected to the clock input pin CLKIN of the PLL chip, the other end of crystal oscillator X1, and one end of capacitor C41. The other end of capacitor C41 is grounded. The output pin OUTP of the PLL chip is connected to the first ADC input or the second ADC input of the data processing circuit. The serial clock pin SCLK, serial data input / output pin SDA, synchronous output pin SYNCO, chip select pin, or address select pin CS of the PLL chip are connected to the data processing circuit. The BOOT pin of the phase-locked loop (PLL) chip is grounded.

[0090] In some embodiments, the phase-locked loop chip is model ADA2200.

[0091] In some embodiments, see Figure 17 The power supply circuit includes a power management chip and a level conversion chip. The input terminal of the power management chip is connected to an input voltage (e.g., 5V), and the output terminal of the power management chip is connected to the input terminal of the level conversion chip. The output terminal of the level conversion chip is used to output a first voltage, such as 3.3V in this embodiment. The power management chip is model MP5087GG. The level conversion chip is model SY98003D. The power supply circuit also includes a power module for converting the first voltage into the voltage required by this invention.

[0092] Further, the reference gas chamber is provided with the to-be-detected gas.

[0093] Preferably, the resistance value of the thermistor in the laser detected by the laser temperature control circuit can be used to inversely determine the current set temperature of the laser. The temperature control circuit can be used to scan the set temperature range T0 to T n .

[0094] Preferably, the data processing circuit is used to receive the electrical signal of the reference detector through the reference signal acquisition circuit. When the temperature of the laser is set to T0 to T n , the data processing circuit compares the zero-crossing point λ c of the signal after harmonic calculation, so as to determine the position of the zero-crossing point λ c that meets the set requirement, and the temperature of the laser temperature control corresponding to the position is the set point T c , so that the wavelength of the laser is self-aligned to the absorption wavelength of the to-be-detected gas.

[0095] In some embodiments, the data processing circuit is used to track the electrical signal of the reference detector received by the reference signal acquisition circuit in real time. When the first harmonic zero-crossing point λ θ deviates from λ c , the set point T c of the temperature of the laser is adjusted (for example, the set point T c1 of the temperature of the laser is changed), so as to correct the first harmonic zero-crossing point λ θ , so that the harmonic zero-crossing point λ θ returns to the position λ c , thereby calibrating the wavelength of the laser to align to the absorption wavelength of the to-be-detected gas in real time.

[0096] In some other embodiments, the data processing circuit is used to track the electrical signal of the reference detector received by the reference signal acquisition circuit in real time, so as to obtain the second harmonic signal. When the abscissa position λ θ2 corresponding to the peak value of the second harmonic signal deviates from λ c , the set point of the temperature of the laser is adjusted, so as to correct the position λ θ2 of the second harmonic signal, so that the position λ θ2 returns to the position λ c .

[0097] Preferably, the data processing circuit is used to receive the electrical signal output by the reference detector or the measurement detector, that is, the original absorption signal. When the change of the sine wave level in the second part of the original absorption signal is detected, the data processing circuit controls the laser driving circuit to adjust the amplitude of the sine wave level of the modulation signal, so that the sine wave level of the first part and the second part of the modulation signal returns to the set value, thereby maintaining the stability of the output light intensity of the laser.

[0098] The data processing circuit receives an electrical signal outputted by the reference detector or the measuring detector, i.e., an original absorption signal, and controls the laser driver circuit to adjust the starting or ending level of the low-frequency sawtooth wave of the modulation signal when a change of the high-level constant voltage signal or the low-level constant voltage signal in the second part of the original absorption signal is detected compared with the second set value, and the amplitude of the low-frequency sawtooth wave is not adjusted.

[0099] Further, the measuring chamber is provided with a temperature sensor and a pressure sensor, the temperature sensor is used for detecting the temperature of the measuring chamber and transmitting to the data processing circuit, and the pressure sensor is used for detecting the pressure of the measuring chamber and transmitting to the data processing circuit.

[0100] The utility model embodiment further discloses a temperature control self-setting method of the laser gas detection device, comprising the following steps:

[0101] The laser driver circuit outputs a corresponding periodic continuous modulation signal to tune the laser, wherein a single period signal of the modulation signal comprises a first part signal for wavelength calibration and real-time measurement and a second part signal for light intensity calibration;

[0102] The laser temperature control circuit sets a temperature scanning range for the laser;

[0103] The electrical signal outputted by the reference detector is received and solved, and when a zero-crossing point λ c that meets the set requirement exists in the signal, the temperature T c corresponding to the signal is obtained.

[0104] The laser temperature control circuit sets a temperature for the laser, and the laser temperature setting point is T c , so that the laser wavelength self-aligns with the absorption wavelength of the measured gas.

[0105] Further, the first part signal is a first superimposed signal formed by superimposing a low-frequency half sawtooth wave on a high-frequency sine wave.

[0106] The second partial signal is one of a second superimposed signal formed by superimposing a high-frequency sine wave on a high-level constant voltage signal, a third superimposed signal formed by superimposing a high-frequency sine wave on a low-level constant voltage signal, an unabsorbed front section of the first superimposed signal, and an unabsorbed rear section of the first superimposed signal, or the second partial signal is any combination of the six signals of the low-level constant voltage signal, the high-level constant voltage signal, the second superimposed signal, the third superimposed signal, the unabsorbed front section of the first superimposed signal, and the unabsorbed rear section of the first superimposed signal, and each combination includes at least one of the second superimposed signal, the third superimposed signal, the unabsorbed front section of the first superimposed signal, and the unabsorbed rear section of the first superimposed signal.

[0107] The amplitude and frequency of the sine wave of the first superimposed signal are consistent with the amplitude and frequency of the sine wave of the second superimposed signal or / and the third superimposed signal.

[0108] The level of the low-level constant voltage signal of the second partial signal and / or the low-level constant voltage signal of the third superimposed signal is the same as the starting low level of the first superimposed signal of the first partial signal.

[0109] The level of the high-level constant voltage signal of the second partial signal and / or the high-level constant voltage signal of the second superimposed signal is the same as the terminal high level of the first superimposed signal of the first partial signal.

[0110] Preferably, the second partial signal is one of the second superimposed signal formed by superimposing a high-frequency sine wave on a high-level constant voltage signal and the third superimposed signal formed by superimposing a high-frequency sine wave on a low-level constant voltage signal, or the second partial signal is any combination of the four signals of the low-level constant voltage signal, the high-level constant voltage signal, the second superimposed signal, and the third superimposed signal, and each combination includes at least one of the second superimposed signal and the third superimposed signal.

[0111] Further, the time period corresponding to the high-level constant voltage signal and the second superimposed signal is after the time period corresponding to the first superimposed signal. The time period corresponding to the low-level constant voltage signal and the third superimposed signal is before the time period corresponding to the first superimposed signal.

[0112] As a specific embodiment, the voltage-controlled current source laser driver circuit uses four parts of a low-level constant current signal superimposed on a high-frequency sine wave and a low-frequency half-sawtooth wave superimposed on a high-frequency sine wave to periodically and continuously tune the laser. The low-level constant voltage signal is 40 mA, the half-sawtooth wave is 40 mA to 70 mA at a frequency of 5 Hz, and the high-frequency sine wave has a peak-to-peak amplitude of 2 mA and a frequency of 2 KHZ to modulate the driving laser output.

[0113] Further, the control laser temperature control circuit sets a temperature scan of the laser according to a set scan range, specifically including: changing the laser temperature set point according to the set scan range to make the received reference detector output electrical signal appear a required zero-crossing point λ c .

[0114] The control laser temperature control circuit sets a temperature scan of the laser according to a set scan range, specifically including: changing the laser temperature set point according to the set scan range to make the received reference detector output electrical signal appear a required zero-crossing point λ c , and make λ c Position located in the single cycle signal center of the first harmonic signal.

[0115] The electrical signal output by the reference detector is an original absorption signal, the original absorption signal is filtered, fitted and calculated to obtain a direct absorption signal, and the original absorption signal is calculated by phase-locked filtering to obtain a harmonic signal.

[0116] The utility model embodiment further discloses a wavelength real-time self-calibration method of the laser gas detection device, comprising the following steps:

[0117] The control laser drive circuit outputs a corresponding periodic continuous modulation signal to tune the laser, wherein a single cycle signal of the modulation signal comprises a first part signal for wavelength calibration and real-time measurement and a second part signal for light intensity calibration.

[0118] The electrical signal output by the reference detector is received and calculated to obtain a first harmonic signal, when the first harmonic zero-crossing point position λ θ Deviation λ c , the laser temperature set point is adjusted to correct the first harmonic zero-crossing point position λ θ , make the harmonic zero-crossing point position λ θ Return to λ c Position.

[0119] Or

[0120] The electrical signal output by the reference detector is received and calculated to obtain a second harmonic signal, when the second harmonic peak corresponding horizontal coordinate position λ θ2 Deviation λ c , the laser temperature set point is adjusted to correct the second harmonic signal position λ θ2 , make the position λ θ2 Return to λ c Position.

[0121] Optionally, the laser temperature set point is adjusted to correct the first harmonic zero-crossing point position λ θ , make the harmonic zero-crossing point position λθ back to lambda c position, specifically comprising: obtaining lambda θ deviation value, obtaining temperature adjustment amount according to the deviation value, adjusting the laser temperature set point from T c to T c , so as to correct the harmonic zero-crossing position lambda c1， back to lambda θ position. c .

[0122] The utility model discloses a kind of light intensity real-time self-calibration method of laser gas detection device, comprising the following steps:

[0123] Control laser driver circuit output corresponding periodic continuous modulation signal to tune laser, wherein the single cycle signal of the modulation signal includes the first part signal for wavelength calibration and real-time measurement and the second part signal for light intensity calibration;

[0124] Receive the electrical signal of reference detector or measurement detector output, i.e. original absorption signal, when detecting that the sinusoidal wave level in the second part signal of original absorption signal changes compared with first set value, control laser driver circuit adjusts the sinusoidal wave level amplitude of modulation signal, so that the sinusoidal wave level of modulation signal returns to set value;

[0125] Receive the electrical signal of reference detector or measurement detector output, i.e. original absorption signal, when detecting that the high level constant voltage signal or low level constant voltage signal in the second part signal of original absorption signal changes compared with second set value, control laser driver circuit adjusts the low frequency sawtooth wave starting point or terminal point level of modulation signal, and low frequency sawtooth wave level amplitude does not adjust.

[0126] The utility model embodiment further discloses a kind of gas concentration measurement control method of laser gas detection device, comprising the following steps:

[0127] Step S1: complete laser temperature self-setting, so that its wavelength self-alignment measured gas absorption wavelength;

[0128] Step S2: complete laser wavelength, light intensity self-calibration;

[0129] Step S3: accept the electrical signal of measurement signal acquisition circuit, obtain the first harmonic peak-peak value A c , zero-crossing value A of signal after harmonic solution, and A c / A as the original value of detection gas concentration inversion;

[0130] Step S4: according to gas concentration original value, gas concentration is inverted using Beer-Lambert law.

[0131] The laser gas detection device can realize temperature self-detection and self-setting of any laser controller, that is, each laser does not need manual debugging to find the temperature control point of the wavelength of the corresponding measured gas absorption when the optical module is matched, the sensor production efficiency is greatly improved, and the production cost is reduced.

[0132] Embodiment two

[0133] Referring to Figures 4 to 9 The utility model discloses a kind of laser gas detection devices, including:

[0134] Power supply circuit, the power supply circuit is used to power supply to whole device;

[0135] Laser, the laser is used to generate laser beam;

[0136] Optical splitter, the optical splitter is used to divide laser beam output by laser into measurement light and reference light, and measurement light is guided to measurement gas chamber, and reference light is guided to reference gas chamber;

[0137] Laser driver circuit, the output of the laser driver circuit is connected with laser, and the input of the laser driver circuit is connected with the first DAC output of data processing circuit;

[0138] Laser temperature control circuit, the output of the laser temperature control circuit is connected with TEC and thermistor of laser, and the input of the laser temperature control circuit is connected with the second DAC output of data processing circuit;

[0139] Measurement probe, the measurement probe is used to receive measurement light after measurement gas chamber and be converted into measurement electric signal;

[0140] Reference probe, the reference probe is used to receive reference light after reference gas chamber and be converted into reference electric signal;

[0141] Measurement trans-impedance amplifier circuit, the input of the measurement trans-impedance amplifier circuit is connected with measurement probe, and the output of measurement trans-impedance amplifier circuit is connected with the first ADC input of data processing circuit;

[0142] Reference transimpedance amplification circuit, the input end of the reference transimpedance amplification circuit is connected with the reference detector, and the output end of the reference transimpedance amplification circuit is connected with the second ADC input end of the data processing circuit.

[0143] Further, the first ADC input end of the data processing circuit is used for receiving the electrical signal output by the measurement end transimpedance amplification circuit for ADC conversion to obtain the measurement end original absorption signal; and the second ADC input end of the data processing circuit is used for receiving the electrical signal output by the reference end transimpedance amplification circuit for ADC conversion to obtain the reference end original absorption signal.

[0144] Further, the data processing circuit is provided with a measurement end digital lock-in filter module and / or a measurement end digital filter module, the measurement end digital lock-in filter module is used for performing digital lock-in filtering on the measurement end original absorption signal to obtain the measurement end harmonic signal, and the measurement end digital filter module is used for filtering, fitting and solving the measurement end original absorption signal to obtain the measurement end direct absorption signal.

[0145] The data processing circuit is used for measuring the concentration of the measured gas by using the measurement end harmonic signal or / and the measurement end direct absorption signal.

[0146] The data processing circuit is provided with a reference end digital lock-in filter module and / or a reference end digital filter module, the reference end digital lock-in filter module is used for performing digital lock-in filtering on the reference end original absorption signal to obtain the reference end harmonic signal, and the reference end digital filter module is used for filtering, fitting and solving the reference end original absorption signal to obtain the reference end direct absorption signal.

[0147] The data processing circuit is used for temperature self-setting and wavelength real-time self-calibration by using the reference end harmonic signal or the reference end direct absorption signal.

[0148] The data processing circuit is used for light intensity real-time self-calibration by using the measurement end original absorption signal or the reference end original absorption signal.

[0149] Further, the data processing circuit is used for measuring the concentration of the measured gas by using the measurement end harmonic signal or / and the measurement end direct absorption signal, and is used for using the concentration of the measured gas measured by the measurement end harmonic signal as the concentration of the measured gas when the volume concentration of the measured gas is less than a preset value, and using the concentration of the measured gas measured by the measurement end direct absorption signal as the concentration of the measured gas when the volume concentration of the measured gas is greater than the preset value.

[0150] The embodiment can use a digital phase-locked filtering algorithm (i.e., a digital phase-locked filtering module) or a digital filtering algorithm (i.e., a digital filtering module) arranged in the data processing circuit to replace the analog phase-locked filtering circuit in the first embodiment, so as to simplify the circuit.

[0151] The utility model embodiment further discloses a kind of temperature control self-setting method of laser gas detection device, comprising the following steps:

[0152] The laser driver circuit outputs a corresponding periodic continuous modulation signal to tune the laser, wherein the single cycle signal of the modulation signal includes a first part signal for wavelength calibration and real-time measurement, and a second part signal for light intensity calibration.

[0153] The laser temperature control circuit sets the temperature of the laser according to the set scan range.

[0154] The reference detector outputs an electrical signal, which is received and calculated. c When the signal has a set requirement-absorbing peak or zero crossing point λ c , the corresponding temperature T c of the signal is obtained.

[0155] The laser temperature control circuit sets the temperature of the laser, and the laser temperature set point is T c , so that the laser wavelength self-aligns with the absorption wavelength of the measured gas.

[0156] Further, the first part signal is a first superimposed signal formed by superimposing a low-frequency half sawtooth wave on a high-frequency sine wave.

[0157] The second part signal is one of a second superimposed signal formed by superimposing a high-level constant voltage signal on a high-frequency sine wave, a third superimposed signal formed by superimposing a low-level constant voltage signal on a high-frequency sine wave, an unabsorbed portion of the front section of the first superimposed signal, and an unabsorbed portion of the rear section of the first superimposed signal, or the second part signal is any combination of the six signals, and each combination includes at least one of the second superimposed signal, the third superimposed signal, the unabsorbed portion of the front section of the first superimposed signal, and the unabsorbed portion of the rear section of the first superimposed signal.

[0158] The amplitude and frequency of the sine wave of the first superimposed signal are consistent with those of the sine wave of the second superimposed signal or / and the third superimposed signal.

[0159] The level of the low-level constant voltage signal of the second part signal or / and the low-level constant voltage signal of the third superimposed signal is the same as the starting low level of the first superimposed signal of the first part signal.

[0160] The level of the high-level constant voltage signal of the second partial signal or / and the high-level constant voltage signal of the second superimposed signal is the same as the end-point high level of the first superimposed signal of the first partial signal.

[0161] Preferably, the second partial signal is one of a second superimposed signal formed by superimposing a high-level constant voltage signal on a high-frequency sine wave and a third superimposed signal formed by superimposing a low-level constant voltage signal on a high-frequency sine wave, or the second partial signal is any combination of the four signals of a low-level constant voltage signal, a high-level constant voltage signal, the second superimposed signal and the third superimposed signal, and each combination includes at least one of the second superimposed signal and the third superimposed signal.

[0162] Further, the time period corresponding to the high-level constant voltage signal and the second superimposed signal is after the time period corresponding to the first superimposed signal.

[0163] Further, the control laser temperature control circuit performs temperature scanning on the laser according to the set scanning range, and specifically includes: changing the laser temperature set point according to the set scanning range to make the received reference detector output electric signal appear a required absorption peak point or zero-crossing point λ c .

[0164] The control laser temperature control circuit performs temperature scanning on the laser according to the set scanning range, and specifically includes: changing the laser temperature set point according to the set scanning range to make the received reference detector output electric signal appear a required absorption peak point or zero-crossing point λ c , and make λ c The position is located at the center of a single period signal of the direct absorption signal or the harmonic signal, and the absorption peak point is located at the center of a single period signal of the original absorption signal.

[0165] The electric signal output by the reference detector is an original absorption signal, the original absorption signal is filtered, fitted and solved to obtain a direct absorption signal, and the original absorption signal is phase-locked filtered to obtain a harmonic signal.

[0166] The utility model embodiment further discloses a wavelength real-time self-calibration method of the laser gas detection device, and includes the following steps:

[0167] The control laser drive circuit outputs a corresponding periodic continuous modulation signal to tune the laser, wherein a single period signal of the modulation signal includes a first partial signal for wavelength calibration and real-time measurement and a second partial signal for light intensity calibration.

[0168] The electrical signal of the reference detector output is received and calculated to obtain a direct absorption signal, and when the peak value A of the direct absorption signal deviates from the set value A θ The corresponding abscissa position λ θ1 Deviation of λ from the set value c The laser temperature set point is adjusted to correct the position λ of the direct absorption signal θ1 The position λ is returned to λ θ1 The position λ is returned to λ c ;

[0169] Or

[0170] The electrical signal of the reference detector output is received and calculated to obtain a first harmonic signal, and when the first harmonic zero-crossing position λ of the first harmonic deviates from λ θ The laser temperature set point is adjusted to correct the first harmonic zero-crossing position λ c The harmonic zero-crossing position λ is returned to λ θ The harmonic zero-crossing position λ is returned to λ θ The harmonic zero-crossing position λ is returned to λ c ;

[0171] Or

[0172] The electrical signal of the reference detector output is received and calculated to obtain a second harmonic signal, and when the abscissa position λ corresponding to the peak value of the second harmonic signal deviates from λ θ2 The laser temperature set point is adjusted to correct the position λ of the second harmonic signal c The position λ is returned to λ θ2 The position λ is returned to λ θ2 The position λ is returned to λ c .

[0173] The utility model discloses a kind of light intensity real-time self-calibration method of laser gas detection device, comprising the following steps:

[0174] Control laser driver circuit output corresponding periodic continuous modulation signal to tune laser, wherein, the single period signal of the modulation signal includes the first part signal for wavelength calibration and real-time measurement and the second part signal for light intensity calibration;

[0175] The electrical signal of the reference detector or measurement detector output is received, i.e. the original absorption signal, and when the sinusoidal level in the second part signal of the original absorption signal is detected to change compared with the first set value, the laser driver circuit is controlled to adjust the sinusoidal level amplitude of the modulation signal, so that the sinusoidal level of the first part signal and the second part of the modulation signal returns to the set value;

[0176] The system receives the electrical signal output by the reference detector or the measuring detector, which is the original absorption signal. When the high-level constant voltage signal or the low-level constant voltage signal in the second part of the original absorption signal changes compared to the second set value, the system controls the laser drive circuit to adjust the start or end level of the low-frequency sawtooth wave of the modulation signal. The amplitude of the low-frequency sawtooth wave level is not adjusted.

[0177] This utility model embodiment also discloses a gas concentration measurement and control method for a laser gas detection device, including the following steps:

[0178] Step S1: Complete the laser temperature self-setting so that its wavelength is automatically aligned with the absorption wavelength of the gas being measured.

[0179] Step S2: Complete the self-calibration of the laser's wavelength and intensity;

[0180] Step S3: Receive the electrical signal from the transimpedance amplifier circuit at the measurement end, and obtain the peak-to-peak value A of the first harmonic of the signal after harmonic decomposition. c If the value of A is zero, then A will be... c / A is used as the raw value for inverting the gas concentration, or the peak-to-peak value A of the second harmonic signal is obtained. c2 , will A c2 Or A c2 / A is used as the raw value for inverting the concentration of the detected gas, or the peak value A of the direct absorption signal is obtained. c1， A c1 The original value of the detected gas concentration is used to invert the gas concentration based on the original value of the detected gas concentration.

[0181] Step S4: Use Beer-Lambert's law to invert the gas concentration based on the original gas concentration value.

[0182] Example 3

[0183] See Figures 10 to 12 This utility model discloses a laser gas detection device, comprising:

[0184] A power supply circuit, which supplies power to the entire device;

[0185] A laser, which generates a laser beam and passes the laser beam sequentially through a measuring gas chamber and a reference gas chamber;

[0186] A laser driving circuit, wherein the output terminal of the laser driving circuit is connected to the laser, and the input terminal of the laser driving circuit is connected to the first DAC output terminal of the data processing circuit;

[0187] A laser temperature control circuit, wherein the output terminal of the laser temperature control circuit is connected to the TEC and thermistor of the laser, and the input terminal of the laser temperature control circuit is connected to the output terminal of the second DAC of the data processing circuit;

[0188] a reference measurement probe for receiving the light signal emitted after sequentially passing through the measurement gas chamber and the reference gas chamber and converting it into an electrical signal;

[0189] a reference measurement signal acquisition circuit, which comprises a reference measurement transimpedance amplification circuit, an input end of the reference measurement transimpedance amplification circuit being connected with the reference measurement probe, and an output end of the reference measurement transimpedance amplification circuit being connected with a first ADC input end of the data processing circuit.

[0190] The first ADC input end of the data processing circuit is used to receive the electrical signal output by the reference measurement transimpedance amplification circuit for ADC conversion to obtain a reference measurement original absorption signal.

[0191] Further, a reference measurement analog phase-locked filter circuit is arranged between the output end of the reference measurement transimpedance amplification circuit and the second ADC input end of the data processing circuit, or a reference measurement digital phase-locked filter module and / or a reference measurement digital filter module are arranged in the data processing circuit;

[0192] The reference measurement analog phase-locked filter circuit is used to perform phase-locked filtering on the electrical signal output by the reference measurement transimpedance amplification circuit and output to the second ADC input end of the data processing circuit for ADC conversion, so that the second ADC input end of the data processing circuit receives the electrical signal output by the reference measurement analog phase-locked filter circuit to obtain a reference measurement harmonic signal;

[0193] The reference measurement digital phase-locked filter module is used to perform digital phase-locked filtering on the reference measurement original absorption signal to obtain a reference measurement harmonic signal, and the reference measurement digital filter module is used to filter, fit and solve the reference measurement original absorption signal to obtain a reference measurement direct absorption signal;

[0194] The data processing circuit is used to measure the concentration of the measured gas by using the reference measurement harmonic signal or / and the reference measurement direct absorption signal;

[0195] The data processing circuit is used to perform temperature self-setting and wavelength real-time self-calibration by using the reference measurement harmonic signal or the reference measurement direct absorption signal;

[0196] The data processing circuit is used to perform light intensity real-time self-calibration by using the reference measurement original absorption signal.

[0197] In some embodiments, the data processing circuit is configured to measure the concentration of the measured gas by using the reference measurement harmonic signal or / and the reference measurement direct absorption signal, and configured to use the concentration of the measured gas measured by the reference measurement harmonic signal as the concentration of the measured gas when the volume concentration of the measured gas is less than a preset value, and use the concentration of the measured gas measured by the reference measurement direct absorption signal as the concentration of the measured gas when the volume concentration of the measured gas is greater than the preset value.

[0198] That is, the peak-to-peak value A of the harmonic signal is used when the volume concentration is small c The original value of the detected gas concentration is calculated, and the gas concentration is inverted. The data processing circuit is configured to measure the concentration of the measured gas by using the measurement end harmonic signal, specifically comprising: when the measurement end harmonic signal is a first harmonic, the peak-to-peak value A of the first harmonic signal is obtained c , the zero-crossing value A (the zero-crossing value A is the position λ c of the zero-crossing point, which is the baseline of the corresponding ordinate), and A c / A is used as the original value of the inversion of the detected gas concentration, and the gas concentration is inverted according to the original value of the inversion of the detected gas concentration.

[0199] When the measurement end harmonic signal is a second harmonic, the peak-to-peak value A of the second harmonic signal is obtained c2 , and A c2 or A c2 / A is used as the original value of the inversion of the detected gas concentration.

[0200] The peak value A of the direct absorption signal is used when the volume concentration is large c1 as the original value of the detected gas concentration, and the gas concentration is inverted. The original measured gas concentration value Ct is obtained after the inverted value Cr+t is deducted from the reference gas chamber concentration value Cr.

[0201] In some embodiments, the data processing circuit is further configured to invert the gas concentration according to the original value of the inversion of the detected gas concentration, and deduct the reference gas chamber concentration value C r+t from the inverted value of the harmonic calculation gas concentration C r to obtain the original measured gas concentration value C t .

[0202] Further, the reference gas chamber is provided with a to-be-measured gas.

[0203] Further, a temperature sensor and a pressure sensor are arranged in the measurement gas chamber, the temperature sensor is configured to detect the temperature of the measurement gas chamber and transmit the temperature to the data processing circuit, and the pressure sensor is configured to detect the pressure of the measurement gas chamber and transmit the pressure to the data processing circuit. The data processing circuit corrects the obtained gas concentration according to the detected temperature and pressure.

[0204] The light path of the first and second embodiments is that the laser beam is split into the measurement path and the reference path, and then respectively passes through the measurement gas chamber and the reference gas chamber to reach the measurement detector and the reference detector, forming a parallel light path. Different from the light path of the first and second embodiments, the light path of the present embodiment is that the laser beam sequentially passes through the measurement gas chamber and the reference gas chamber to reach the reference measurement detector, forming a series light path.

[0205] The data processing circuit of the present embodiment is the same as the data processing circuits disclosed in the first and second embodiments.

[0206] The data processing circuit includes a data processing module, an ADC module and a DAC module, and the data processing module is connected with the ADC module and the DAC module. The DAC module of the data processing circuit is connected with the laser driver circuit to modulate the laser. The DAC module of the data processing circuit is also connected with the laser temperature control circuit to control the temperature of the laser. Different from the first and second embodiments, the present embodiment combines the measurement end trans-impedance amplification circuit and the reference end trans-impedance amplification circuit into one reference measurement trans-impedance amplification circuit. The data processing circuit is connected with the reference measurement acquisition circuit to demodulate the signal of the reference measurement detector, to calibrate the wavelength and light intensity of the laser and measure the concentration of the measured gas.

[0207] In some embodiments, the reference measurement acquisition circuit includes a reference measurement trans-impedance amplification circuit (the reference measurement trans-impedance amplification circuit of the present embodiment does not provide an analog phase-locked filter circuit), the input end of the reference measurement trans-impedance amplification circuit is connected with the reference measurement detector, and the output end of the reference measurement trans-impedance amplification circuit is connected with the ADC input end of the data processing circuit. The data processing circuit is provided with a reference measurement digital phase-locked filter module, the ADC module of the data processing circuit is used to receive the electrical signal output by the reference measurement trans-impedance amplification circuit to perform ADC conversion to obtain a digital signal, the reference measurement digital phase-locked filter module is used to perform digital phase-locked filtering on the digital signal to obtain a reference measurement harmonic signal, and the data processing circuit is used to utilize the reference measurement harmonic signal to implement the steps of the light intensity wavelength self-calibration method as described below. The present embodiment uses the digital phase-locked filtering algorithm in the data processing circuit to replace the analog phase-locked filter circuit of the first embodiment, simplifying the circuit. Of course, the reference measurement acquisition circuit of some embodiments can also be provided with an analog phase-locked filter circuit between the reference measurement trans-impedance amplification circuit and the data processing circuit to replace the digital phase-locked filtering algorithm in the data processing circuit.

[0208] The power supply circuit of the embodiment is the same as the power supply circuits disclosed in Embodiment One and Embodiment Two. The laser driver circuit of the embodiment is the same as the laser driver circuits disclosed in Embodiment One and Embodiment Two. The laser temperature control circuit of the embodiment is the same as the laser temperature control circuits disclosed in Embodiment One and Embodiment Two. The reference measurement trans-impedance amplification circuit of the embodiment adopts a trans-impedance amplifier, which is the same as the trans-impedance amplifier circuits disclosed in Embodiment One and Embodiment Two.

[0209] The utility model embodiment further discloses a kind of temperature control self-setting method of laser gas detection device, comprising the following steps:

[0210] The laser driver circuit is controlled to output corresponding periodic continuous modulation signal to tune the laser, wherein the single cycle signal of the modulation signal includes a first part signal for wavelength calibration and real-time measurement, and a second part signal for light intensity calibration;

[0211] The laser temperature control circuit is controlled to set temperature scanning on the laser according to the set scanning range;

[0212] The electrical signal output by the reference detector is received and solved, and when the signal has a set requirement-absorbing peak value or zero crossing point λ c , the temperature T c corresponding to the signal is obtained.

[0213] The laser temperature control circuit is controlled to set temperature on the laser, and the laser temperature set point is T c , so that the laser wavelength self-aligns with the measured gas absorption wavelength.

[0214] Further, the first part signal is a first superimposed signal formed after low-frequency half sawtooth wave is superimposed on high-frequency sine wave;

[0215] The second part signal is one of a second superimposed signal formed after high-level constant voltage signal is superimposed on high-frequency sine wave, a third superimposed signal formed after low-level constant voltage signal is superimposed on high-frequency sine wave, a front non-absorbed part of the first superimposed signal, and a rear non-absorbed part of the first superimposed signal, or the second part signal is any combination of the six signals of low-level constant voltage signal, high-level constant voltage signal, second superimposed signal, third superimposed signal, front non-absorbed part of the first superimposed signal, and rear non-absorbed part of the first superimposed signal, and each combination includes at least one of the second superimposed signal, the third superimposed signal, the front non-absorbed part of the first superimposed signal, and the rear non-absorbed part of the first superimposed signal.

[0216] The amplitude and frequency of the sine wave of the first superimposed signal are consistent with the amplitude and frequency of the sine wave of the second superimposed signal or / and the third superimposed signal.

[0217] The level of the low-level constant voltage signal of the second partial signal or / and the low-level constant voltage signal of the third superimposed signal is the same as the starting low level of the first superimposed signal of the first partial signal.

[0218] The level of the high-level constant voltage signal of the second partial signal or / and the high-level constant voltage signal of the second superimposed signal is the same as the ending high level of the first superimposed signal of the first partial signal.

[0219] Preferably, the second partial signal is one of a second superimposed signal formed by superimposing a high-frequency sine wave on a high-level constant voltage signal and a third superimposed signal formed by superimposing a high-frequency sine wave on a low-level constant voltage signal, or the second partial signal is any combination of the four signals of the low-level constant voltage signal, the high-level constant voltage signal, the second superimposed signal and the third superimposed signal, and each combination includes at least one of the second superimposed signal and the third superimposed signal.

[0220] Further, the time period corresponding to the high-level constant voltage signal and the second superimposed signal is after the time period corresponding to the first superimposed signal.

[0221] Further, the control laser temperature control circuit performs temperature scanning on the laser according to the set scanning range, and specifically includes: changing the laser temperature set point according to the set scanning range to make the received reference detector output electric signal appear the required absorption peak point or zero-crossing point λ c .

[0222] The control laser temperature control circuit performs temperature scanning on the laser according to the set scanning range, and specifically includes: changing the laser temperature set point according to the set scanning range to make the received reference detector output electric signal appear the required absorption peak point or zero-crossing point λ c , and make λ c The position is located at the center of a single period signal of the direct absorption signal or the harmonic signal, and the absorption peak point is located at the center of a single period signal of the original absorption signal.

[0223] The electric signal output by the reference detector is an original absorption signal, the original absorption signal is filtered, fitted and solved to obtain a direct absorption signal, and the original absorption signal is phase-locked filtered and solved to obtain a harmonic signal.

[0224] The utility model embodiment further discloses a wavelength real-time self-calibration method of the laser gas detection device, and comprises the following steps:

[0225] The laser driver circuit outputs a corresponding periodic continuous modulation signal to tune the laser, wherein a single period signal of the modulation signal comprises a first part signal for wavelength calibration and real-time measurement and a second part signal for light intensity calibration;

[0226] The electrical signal output by the reference detector is received and calculated to obtain a direct absorption signal, and when the peak value A of the direct absorption signal deviates from the set value A θ The corresponding abscissa position λ θ1 Deviation from the set requirement λ c The laser temperature set point is adjusted to correct the position λ θ1 of the direct absorption signal, so that the position λ θ1 returns to the position λ c .

[0227] Or

[0228] The electrical signal output by the reference detector is received and calculated to obtain a first harmonic signal, and when the first harmonic zero-crossing position λ of the first harmonic signal deviates from the set value λ θ The laser temperature set point is adjusted to correct the first harmonic zero-crossing position λ c , so that the harmonic zero-crossing position λ θ returns to the position λ θ . c

[0229] Or

[0230] The electrical signal output by the reference detector is received and calculated to obtain a second harmonic signal, and when the abscissa position λ corresponding to the peak value of the second harmonic signal deviates from the set value λ θ2 The laser temperature set point is adjusted to correct the position λ c of the second harmonic signal, so that the position λ θ2 returns to the position λ θ2 . c

[0231] The utility model discloses a kind of light intensity real-time self-calibration method of laser gas detection device, comprising the following steps:

[0232] The laser driver circuit outputs a corresponding periodic continuous modulation signal to tune the laser, wherein a single period signal of the modulation signal comprises a first part signal for wavelength calibration and real-time measurement and a second part signal for light intensity calibration;

[0233] The electrical signal output by the reference detector or the measurement detector, i.e., the original absorption signal, is received, and when a change in the sinusoidal level in the second part signal of the original absorption signal is detected compared to the first set value, the laser driver circuit adjusts the sinusoidal level amplitude of the modulation signal so that the sinusoidal level of the first part signal and the second part of the modulation signal returns to the set value.​​

[0234] The electrical signal of the reference detector or the measurement detector output, i.e., the original absorption signal, is received, and when a change occurs in the high-level constant voltage signal or the low-level constant voltage signal in the second part of the original absorption signal compared with the second set value, the laser driver circuit is controlled to adjust the low-frequency sawtooth wave starting point or ending point level of the modulation signal, and the low-frequency sawtooth wave level amplitude is not adjusted.

[0235] The utility model embodiment further discloses a gas concentration measurement control method of the laser gas detection device, comprising the following steps:

[0236] Step S1: completing laser temperature self-setting, so that the wavelength is self-aligned to the measured gas absorption wavelength;

[0237] Step S2: completing laser wavelength and light intensity self-calibration;

[0238] Step S3: receiving the electrical signal of the reference measurement detector through the reference measurement acquisition circuit, and taking the first harmonic peak-peak value A c of the signal after harmonic calculation and the zero-crossing value A as the original value of the gas concentration inversion; c

[0239] Step S4: using the Beer-Lambert law to invert the gas concentration according to the gas concentration original value;

[0240] Step S5: deducting the reference gas chamber concentration value C r from the harmonic calculation gas concentration inversion value C r+t to obtain the original measured gas concentration value C t .

[0241] The utility model uses the total absorption signal after the measurement road signal is superposed with the reference road signal as the input mode of the signal, which greatly simplifies the complexity of the external optical path structure, and simplifies the parallel optical path from the laser beam output to the measurement road and the reference road after the light splitting, the measurement gas chamber, and the reference gas chamber to the measurement road detector and the reference road detector into the series optical path from the laser beam output to the measurement gas chamber, the reference gas chamber, and the measurement reference detector. On the other hand, the circuit structure of the optical module is also simplified after the measurement detector transimpedance amplifier circuit and the reference detector transimpedance amplifier circuit are combined into the reference measurement detector transimpedance amplifier circuit. The utility model reduces the use and production cost of the product without reducing the performance of the product, and improves the performance of the product.

[0242] ​The utility model solves the light module of prior art real -time on -line detector, does not have laser temperature control temperature self -checking, self -setting function. And because the wavelength of laser drift, laser threshold value and the change of light intensity slope efficiency, and bring the need to return to factory calibration cannot realize long -term stable reliable work. And because the algorithm filter function of the lack of light intensity small amplitude change, causes sensor indication stability difference, or a series of problems such as the response speed of multiple average algorithm slow. Summarized above, the utility model provides a kind of for gas detection's self-stable frequency full integration optical machine assembly in the case where other structural components and assembly mode do not change, light emission assembly can select the assembly of different light beam output form;Reference detector assembly and wave detection detector light assembly can also select different light receiving assembly.Combining with the use of innovative active optical interference link coupling adjustment process and laser welding process, improve the temperature adaptability and reliability of product, reduce manufacturing cost and use cost, realize the function of factory calibration-free and calibration-free in true sense after product.

[0243] It can be understood that the above embodiments are only exemplary embodiments adopted for illustrating the principles of the utility model, and the utility model is not limited to this. For ordinary skilled persons in the art, various modifications and improvements can be made without departing from the spirit and essence of the utility model, and these modifications and improvements are also regarded as the protection scope of the utility model.

Claims

1. A laser gas detection device, characterized in that, include: A power supply circuit, which supplies power to the entire device; A laser, which generates a laser beam and passes the laser beam sequentially through a measuring gas chamber and a reference gas chamber; A laser driving circuit, wherein the output terminal of the laser driving circuit is connected to the laser, and the input terminal of the laser driving circuit is connected to the first output terminal of the data processing circuit. A laser temperature control circuit, wherein the output terminal of the laser temperature control circuit is connected to the TEC of the laser, and the input terminal of the laser temperature control circuit is connected to the second output terminal of the data processing circuit; A reference measurement detector is used to receive the optical signal emitted after passing through the measurement chamber and the reference chamber in sequence, and convert it into an electrical signal. A reference measurement signal acquisition circuit is provided, which includes a reference measurement transimpedance amplifier circuit. The input terminal of the reference measurement transimpedance amplifier circuit is connected to a reference measurement detector, and the output terminal of the reference measurement transimpedance amplifier circuit is connected to the first input terminal of a data processing circuit.

2. The laser gas detection device according to claim 1, characterized in that: The reference measurement signal acquisition circuit also includes a reference measurement analog phase-locked filter circuit. The reference measurement analog phase-locked filter circuit is connected between the output terminal of the reference measurement transimpedance amplifier circuit and the second input terminal of the data processing circuit. The reference measurement analog phase-locked filter circuit is used to perform phase-locked filtering on the electrical signal output by the reference measurement transimpedance amplifier circuit and output it to the second input terminal of the data processing circuit.

3. The laser gas detection device according to claim 2, characterized in that: The reference measurement transimpedance amplifier circuit uses a transimpedance amplifier.

4. A laser gas detection device, characterized in that, include: A power supply circuit, which supplies power to the entire device; A laser used to generate a laser beam; A beam splitter is used to split the laser beam output by the laser into a measurement beam and a reference beam, and to guide the measurement beam to the measurement gas chamber and the reference beam to the reference gas chamber. A laser driving circuit, wherein the output terminal of the laser driving circuit is connected to the laser, and the input terminal of the laser driving circuit is connected to the first output terminal of the data processing circuit. A laser temperature control circuit, wherein the output terminal of the laser temperature control circuit is connected to the TEC of the laser, and the input terminal of the laser temperature control circuit is connected to the second output terminal of the data processing circuit; A measuring detector is used to receive the measuring light emitted after passing through the measuring chamber and convert it into a measuring electrical signal; A reference detector is used to receive the reference light emitted after passing through the reference gas cell and convert it into a reference electrical signal; The measurement signal acquisition circuit includes a measurement transimpedance amplifier circuit, the input terminal of which is connected to the measurement detector, and the output terminal of which is connected to the first input terminal of the data processing circuit. The reference signal acquisition circuit includes a reference transimpedance amplifier circuit. The input terminal of the reference transimpedance amplifier circuit is connected to a reference detector, and the output terminal of the reference transimpedance amplifier circuit is connected to the second input terminal of the data processing circuit.

5. The laser gas detection device according to claim 4, characterized in that: The measurement signal acquisition circuit also includes a measurement analog phase-locked filter circuit, which is connected between the output terminal of the measurement transimpedance amplifier circuit and the first input terminal of the data processing circuit. The measurement analog phase-locked filter circuit is used to perform phase-locked filtering on the electrical signal output by the measurement transimpedance amplifier circuit and output it to the first input terminal of the data processing circuit. The reference signal acquisition circuit also includes a reference analog phase-locked filter circuit, which is connected between the output terminal of the reference transimpedance amplifier circuit and the second input terminal of the data processing circuit. The reference analog phase-locked filter circuit is used to perform phase-locked filtering on the electrical signal output by the reference transimpedance amplifier circuit and output it to the second input terminal of the data processing circuit. The output of the measuring transimpedance amplifier circuit or the reference transimpedance amplifier circuit is connected to the third input of the data processing circuit.

6. The laser gas detection device according to claim 5, characterized in that: The measurement analog phase-locked loop filter circuit and the reference analog phase-locked loop filter circuit are constructed using phase-locked loop chips.

7. The laser gas detection device according to claim 5, characterized in that: Both the measurement transimpedance amplifier circuit and the reference transimpedance amplifier circuit use transimpedance amplifiers.

8. The laser gas detection device according to claim 3 or 7, characterized in that: The transimpedance amplifier includes operational amplifier U2. The non-inverting input of operational amplifier U2 is connected to one end of resistor R7 and one end of capacitor C11, respectively. The other ends of resistor R7 and capacitor C11 are grounded. The inverting input of operational amplifier U2 is the input of the transimpedance amplifier circuit, used to receive the electrical signal output by the detector. The inverting input of operational amplifier U2 is connected to one end of resistor R1 and one end of capacitor C1, respectively. The other ends of resistor R1 and capacitor C1 are connected to the output of operational amplifier U2. The output of operational amplifier U2 is the output of the transimpedance amplifier circuit, used to output the amplified electrical signal.

9. The laser gas detection device according to any one of claims 1 to 7, characterized in that: The laser driving circuit includes operational amplifiers U6 and U4. The non-inverting input of operational amplifier U6 is connected to the first output of the data processing circuit via resistor R12. The inverting input of operational amplifier U6 is connected to one end of resistor R9 and one end of resistor R5, respectively. The other end of resistor R9 is grounded. The other end of resistor R5 is connected to the output of operational amplifier U6. The output of operational amplifier U6 is connected to the non-inverting input of operational amplifier U4 via resistor R11. The non-inverting input of operational amplifier U4 is connected to one end of resistor R14. The other end of resistor R14 is connected to one end of capacitor C22 and the positive terminal of the laser, respectively. The other end of capacitor C22 is grounded. The inverting input of operational amplifier U4 is connected to one end of resistor R2 and one end of resistor R4, respectively. The other end of resistor R2 is grounded. The other end of resistor R4 is connected to the output of operational amplifier U4. The output of operational amplifier U4 is connected to one end of resistor R10, and the other end of resistor R10 is connected to the positive terminal of the laser.

10. The laser gas detection device according to any one of claims 1 to 7, characterized in that: It also includes a temperature sensor and a pressure sensor. The temperature sensor is used to detect the temperature of the measuring chamber and transmit it to the data processing circuit. The pressure sensor is used to detect the pressure of the measuring chamber and transmit it to the data processing circuit. And / or, The reference chamber contains the gas to be tested.

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