KR20240056955A - Device and method for measuring gas concentration - Google Patents

Abstract

A gas concentration measuring device that can increase the accuracy of gas concentration measurement is provided. The gas concentration measuring device outputs laser light in different wavelength bands to the detection area to detect the target gas at least twice, accurately calculates the amplitude of the resonance pulse from the light reflected from the detection area, and determines the amplitude of the resonance pulse. The amplitude can be made to match the peak value of the gas absorption curve.

Description

{Device and method for measuring gas concentration}

The present invention relates to a gas concentration measurement device and method based on Tunable Diode Laser Absorption Spectroscopy (TDLAS), which can increase the accuracy of gas concentration measurement.

Each gas has the property of absorbing light of a specific wavelength. Using these properties of the gas, laser light of the wavelength absorbed by the gas to be detected can be irradiated to the gas and the presence or absence of the gas and the concentration of the gas can be measured based on the amount of absorbed laser light.

Tunable Diode Laser Absorption Spectroscopy (TDLAS) is used to measure the presence and concentration of these gases. TDLAS uses a laser with variable wavelength to irradiate laser light onto gas while changing the bias current, and uses the difference between the intensity of light measured at a wavelength that is not absorbed by the gas and the intensity of light measured at a wavelength that is absorbed. By measuring the amount of light absorbed by the gas, the presence or absence of the gas and its concentration are measured at a specific point.

Gas detection and concentration measurement using TDLAS largely includes Wavelength Modulation Spectroscopy (WMS) and Direct Absorption Spectroscopy (DAS).

Wavelength modulation spectroscopy (WMS) is a method of modulating and investigating the signal of a tunable laser and measuring the returned measurement signal based on the modulated signal. Since the change in the signal is large, it can maximize the sensitivity for detecting the change in the signal. , it has the advantage of not being sensitive to the noise characteristics of the signal. On the other hand, there is a disadvantage that the structure and calculation process of the spectroscopic system become complicated because a process such as modulating the laser signal is required.

Direct absorption spectroscopy (DAS) irradiates light using the signal from a tunable laser. Therefore, there is an advantage that the structure and calculation process of the spectroscopic system are simple. On the other hand, it has the disadvantage of having low sensitivity in detecting changes in the signal and being sensitive to the noise characteristics of the signal.

Meanwhile, in gas detection and concentration measurement devices using conventional TDLAS, the wavelength of light absorbed by the gas among the light reflected at a specific point due to the driving temperature of the laser and instability of the current input to the light source generating the laser. A problem arises where the positions between the actual gas absorption peak wavelength do not match. Because of this, the accuracy of measuring the concentration of gas present at a specific point is decreasing.

Korean Patent No. 10-2309250 (2021.10.07.)

The purpose of the present invention is to provide a gas concentration measuring device and method that can increase the accuracy of gas concentration measurement.

A gas concentration measuring device according to an embodiment of the present invention includes a light source that generates light for a detection area; a light receiving unit that receives light reflected from the detection area; and changing the wavelength band of light output from the light source based on the first viewpoint reflection signal output from the light receiving unit, and a second viewpoint reflection signal output from the light receiving unit by the light whose wavelength band is changed from the first viewpoint reflection signal. It includes a control unit that measures the concentration of the target gas in the detection area based on.

The control unit may include a pulse extraction unit that extracts one or more pulses including a resonance pulse from the plurality of pulses of the first viewpoint reflection signal; A current variable unit that changes the wavelength band of the light output from the light source by adjusting the size variable range of the current applied to the light source based on the one or more extracted pulses; and a concentration measuring unit that measures the concentration of the target gas based on the difference between the amplitude of a reference pulse among the plurality of pulses of the first viewpoint reflection signal and the amplitude of the resonance pulse among the plurality of pulses of the second viewpoint reflection signal. do.

The current variable unit adjusts the size variable range of the current applied to the light source to decrease based on the one or more pulses.

The pulse extraction unit extracts the resonance pulse and one or more pulses adjacent to the resonance pulse from the plurality of pulses of the first viewpoint reflection signal.

The control unit controls the variable range of the size of the current applied to the light source to narrow the wavelength band of the light output from the light source.

The gas concentration measurement method according to an embodiment of the present invention outputs light in a first wavelength band generated from a light source according to a first current to a detection area, receives light reflected from the detection area, and produces a first viewpoint reflection signal. outputting; extracting one or more pulses including a resonance pulse from the first viewpoint reflection signal; generating a second current by adjusting a size variable range of the first current based on the one or more extracted pulses; Outputting light in a second wavelength band from the light source according to the second current, receiving light reflected from the detection area, and outputting a second viewpoint reflection signal; and measuring the concentration of the target gas in the detection area based on the first viewpoint reflection signal and the second viewpoint reflection signal.

The step of generating the second current is a step of generating the second current by reducing the size variable range of the first current based on the one or more pulses.

The step of extracting the one or more pulses is a step of extracting the resonance pulse and one or more pulses adjacent to the resonance pulse from the plurality of pulses of the first viewpoint reflection signal.

Measuring the concentration of the target gas may include calculating the amplitude of a reference pulse among a plurality of pulses of the first viewpoint reflection signal; calculating the amplitude of a resonance pulse among the plurality of pulses of the second viewpoint reflection signal; and calculating the concentration of the target gas based on the difference between the amplitude of the reference pulse and the amplitude of the resonance pulse.

The present invention outputs laser light in different wavelength bands to the detection area to detect the target gas at least twice, accurately calculating the amplitude of the resonance pulse from the light reflected from the detection area, and calculating the peak value of the gas absorption curve and can be made to match.

Accordingly, the present invention can prevent false detection of the target gas by increasing the accuracy of determining the type and calculating the concentration of the target gas in the detection area.

Figure 1 is a block diagram of a gas concentration measuring device according to an embodiment of the present invention.
Figure 2 is a flowchart of a method for measuring gas concentration according to an embodiment of the present invention.
3 to 5 are diagrams showing an embodiment of the gas concentration measurement method of the present invention.

The advantages and features of the present invention and methods for achieving them will become clear by referring to the embodiments described in detail below along with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below and may be implemented in various different forms. The present embodiments are merely provided to ensure that the disclosure of the present invention is complete and to be understood by those skilled in the art in the technical field to which the present invention pertains. It is provided to fully inform those who have the scope of the invention, and the present invention is only defined by the scope of the claims.

In describing embodiments of the present invention, if a detailed description of a known function or configuration is judged to unnecessarily obscure the gist of the present invention, the detailed description will be omitted. The terms described below are defined in consideration of functions in the embodiments of the present invention, and may vary depending on the intention or custom of the user or operator. Therefore, the definition should be made based on the contents throughout this specification.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings.

Figure 1 is a block diagram of a gas concentration measuring device according to an embodiment of the present invention.

Referring to FIG. 1, the gas concentration measuring device 100 of this embodiment may include a light source 110, an amplifying unit 120, a light receiving unit 140, and a control module 150.

The light source 110 may generate light in a predetermined wavelength band, for example, laser light, based on the driving current applied from the control module 150. Laser light may be output to the external detection area 10 through the optical unit 130, which will be described later.

Here, the light source 110 can be generated by adjusting the wavelength band of the laser light according to the size of the driving current applied from the control module 150. For example, the light source 110 can generate laser light in a short-wavelength band or a long-wavelength band depending on the size of the driving current, and as the size of the driving current increases, it can generate laser light in a long-wavelength band.

The amplification unit 120 may amplify and output the laser light generated by the light source 110. At this time, the amplification unit 120 can output laser light in the form of a pulse by adjusting the amplification rate by the control module 150.

The optical unit 130 may output the laser light output from the amplifying unit 120 to the detection area 10, receive the light reflected from the detection area 10, and provide it to the light receiving unit 140. This optical unit 130 may reflect light of a specific wavelength and transmit light of other wavelengths excluding this.

In addition, according to an embodiment of the present invention, the optical unit 130 reflects light at a specific location and transmits light at other locations excluding this, or reflects light of a specific polarization and transmits light of the remaining polarization except for this. It can also be transmitted.

The optical unit 130 may further include a spatial scanner capable of controlling and outputting the direction of the laser light in the up/down/left/right directions within a preset angle range.

The light receiving unit 140 may receive reflected light reflected from the detection area 10 through the optical unit 130. The light receiving unit 140 may convert the received reflected light into an electrical signal and output a reflected signal at each light reception point. This light receiving unit 140 may include one or more light receiving elements including a single photon detection cell.

Meanwhile, in this embodiment, the light receiving unit 140 converts the received reflected light into an electrical signal and outputs it as an example, but is not limited to this. For example, the light receiving unit 140 may output the received reflected light to the control module 150, and the control module 150 may convert the reflected light into an electrical signal.

The control module 150 applies a driving current to the light source 110 to control the light source 110 to generate laser light in a specific wavelength band, based on the reflection signal at the first time output from the light receiving unit 140. By adjusting the size of the driving current applied to the light source 110, the wavelength band of the laser light output from the light source 110 can be changed. At this time, the control module 150 can adjust the size by adjusting the variable range of the driving current.

In addition, the control module 150 receives the reflected signal at the second time point from the light receiving unit 140, and detects the target gas within the detection area 10 based on the already received reflected signal at the first time point and the reflected signal at the second time point. The concentration can be measured.

Here, the reflected signal at the second time point output from the light receiving unit 140 refers to a signal converted from the reflected light reflected in the detection area 10 by the laser light of which the wavelength band changed from the light source 110 is converted into an electrical signal. You can.

The control module 150 may include a pulse extraction unit 151, a current variable unit 153, and a concentration measurement unit 155.

The pulse extraction unit 151 may extract a plurality of wavelength signals included in the first viewpoint reflection signal output from the light receiving unit 140, for example, one or more pulses including a resonant pulse among the plurality of pulses. Here, the resonance pulse may refer to the pulse with the smallest amplitude among the plurality of pulses of the first viewpoint reflection signal.

The pulse extraction unit 151 may extract a pulse adjacent to the resonance pulse, for example, one or more adjacent pulses adjacent to the left/right of the resonance pulse, from among the plurality of pulses of the reflected signal at the first time point together with the resonance pulse.

The current variable unit 153 can adjust the variable range to adjust the size of the driving current applied to the light source 110 based on one or more pulses extracted by the pulse extractor 151. Here, the driving current generated in the current variable unit 153 may be an alternating current such as a sine wave, triangle wave, or square wave. The current variable unit 153 can adjust the size of the driving current applied to the light source 110 by varying the peak-to-peak range of the previously output driving current based on one or more extracted pulses. there is. At this time, the current variable unit 153 adjusts the range of the two peaks of the driving current applied to the light source 110 to narrow, that is, to reduce the size of the driving current, thereby reducing the laser light generated from the light source 110. has a narrow wavelength band compared to previously generated laser light.

The concentration measuring unit 155 may extract the amplitude of the reference pulse from the plurality of pulses of the reflection signal at the first viewpoint provided by the light receiving unit 140, and extract the amplitude of the resonance pulse from the plurality of pulses of the reflection signal at the second viewpoint. there is. The concentration measuring unit 155 may calculate the concentration of the target gas in the detection area 10 according to the difference between the extracted reference pulse amplitude and the resonance pulse amplitude. Here, the reference pulse may refer to the pulse that is furthest away from the resonance pulse in the first viewpoint reflection signal.

Additionally, the concentration measurement unit 155 may connect the amplitudes of each of the plurality of pulses of the first time reflection signal, for example, connect the amplitude high points of each pulse to generate a gas absorption curve of a predetermined shape. The concentration measuring unit 155 may determine the type of target gas in the detection area 10 based on the shape of the gas absorption curve. Accordingly, the concentration measuring unit 155 may output the determined gas type along with the previously calculated gas concentration.

In this way, the gas concentration measuring device 100 of this embodiment adjusts the driving current applied to the light source 110 so that laser light with different wavelength bands is output to the detection area 10 at least twice, so that the detection area 10 ), the amplitude of the resonance pulse caused by the target gas, that is, the amplitude peak, can be accurately calculated from at least two reflected lights reflected from ).

Accordingly, the gas concentration measuring device 100 of the present invention ensures that the amplitude of the resonance pulse exactly matches the peak value of the gas absorption curve, thereby improving the accuracy of determining the type of target gas in the detection area 10 and calculating the concentration of the target gas. By increasing , false detection of the target gas in the detection area 10 can be prevented.

Figure 2 is a flowchart of a method for measuring gas concentration according to an embodiment of the present invention, and Figures 3 to 5 are diagrams showing an embodiment of the method for measuring gas concentration of the present invention.

First, the control module 150 may apply a first current of a predetermined size to the light source 110 as a driving current through the current variable unit 153. The light source 110 may generate laser light in a first wavelength band according to the applied first current and output it to the detection area 10 (S10).

Here, one or more target gases for measuring gas type and concentration may exist in the detection area 10. This target gas may be ammonia, carbon dioxide, hydrogen fluoride, hydrogen sulfide, water vapor, or a combination of two or more of these, but is not limited thereto.

Additionally, the laser light in the first wavelength band output from the light source 110 may have a plurality of pulse forms by the amplification unit 120.

Next, the light receiving unit 140 may receive light reflected from the laser light in the first wavelength band in the detection area 10, convert it into an electrical signal, and output a first viewpoint reflection signal (S20). Here, the reflected light received by the light receiving unit 140 may be a state in which light of a specific wavelength among the laser light of the first wavelength is absorbed by the target gas in the detection area 10.

Subsequently, the pulse extraction unit 151 of the control module 150 may extract one or more pulses including a resonance pulse from the first viewpoint reflection signal (S30).

As shown in FIG. 3, the first viewpoint reflection signal output from the light receiving unit 140 may include a plurality of pulses corresponding to different wavelengths, for example, a plurality of wavelengths from λ1 to λn. These plural pulses may have amplitudes corresponding to each wavelength. At this time, as described above, the pulse of a specific wavelength among the first viewpoint reflection signals is generated from the reflected light remaining after being absorbed by the target gas, and therefore may have a relatively small amplitude compared to other pulses.

The pulse extractor 151 may extract a resonance pulse with the smallest amplitude among the plurality of pulses of the first viewpoint reflection signal. Additionally, a peak wavelength, for example, λr1 wavelength, may exist around the resonance pulse according to the absorption curve by the target gas.

Accordingly, the pulse extraction unit 151 selects one or more pulses adjacent in the left/right direction based on the resonance pulse, for example, adjacent pulses corresponding to the λr1-1 wavelength and λr1+1 wavelength among the plurality of wavelengths, respectively, with the resonance pulse. can be extracted together.

Next, the current variable unit 153 may generate a second current by adjusting the size variable range of the first current output to the light source 110 based on one or more extracted pulses (S40).

As described above, the driving current applied from the current variable unit 153 to the light source 110 may be an alternating current. Accordingly, as shown in FIG. 3, the current variable unit 153 narrows the size variable range of the first current, that is, the peak-to-peak range of the first current, to include one or more pulse regions previously extracted on the time axis. 2 Current can be generated. For example, assuming that the peak-to-peak range of the first current is 10 to 100 mA, the current variable unit 153 can generate the second current to have a peak-to-peak range of 30 to 60 mA.

Next, the current variable unit 153 applies the second current to the light source 110, and the light source 110 can generate laser light in the second wavelength band according to the second current. Laser light in the second wavelength band may be output to the detection area 10 through the amplification unit 120 and the optical unit 130 (S50).

Subsequently, the light receiving unit 140 may receive light reflected from the laser light in the second wavelength band in the detection area 10, convert it into an electrical signal, and output a second viewpoint reflection signal (S60).

Here, as shown in FIG. 4, the second viewpoint reflection signal output from the light receiving unit 140, like the previously described first viewpoint reflection signal, is a pulse of a specific wavelength absorbed by the target gas, so that it is relatively small compared to other pulses. It may be a resonant pulse with a small amplitude. This resonant pulse may correspond to a wavelength of λr2.

Meanwhile, Figure 4 shows the variable range of wavelength by the second current, for example, from λr1-1 wavelength to λr1+1 wavelength. Accordingly, the interval between the resonance pulse and the peak wavelength of the gas absorption curve in Figure 4 is It may be narrower than the peak wavelength interval between the resonance pulse and the gas absorption curve due to the first current described in FIG. 3. Additionally, the amplitude of the resonance pulse caused by the second current shown in FIG. 4 may be smaller than the amplitude of the resonance pulse caused by the first current shown in FIG. 3.

Next, the concentration measuring unit 155 of the control module 150 extracts the amplitude of the reference pulse from the plurality of pulses of the previously received first viewpoint reflection signal, and extracts the amplitude of the resonance pulse from the plurality of pulses of the second viewpoint reflection signal. Amplitude can be extracted. The concentration measuring unit 155 may calculate the concentration of the target gas in the detection area 10 according to the difference between the amplitude of the extracted reference pulse and the amplitude of the resonance pulse (S70).

In addition, as shown in FIG. 5, the concentration measurement unit 155 may generate a gas absorption curve by connecting the amplitude high points of each of the plurality of pulses of the first viewpoint reflection signal. At this time, the concentration measurement unit 155 can accurately extract the amplitude of the resonance pulse from the reflection signal at the second time point, so the peak value of the gas absorption amount can be accurately matched to the high point of the amplitude of the resonance pulse.

Accordingly, the concentration measurement unit 155 can determine the type of target gas present in the detection area 10 from the shape of the gas absorption curve generated by connecting the amplitude high points of each of the plurality of pulses. Accordingly, the concentration measuring unit 155 can output the previously calculated concentration of the target gas and the type of the target gas.

As such, the gas concentration measurement method according to this embodiment adjusts the driving current applied to the light source 110 so that laser light with different wavelength bands is output to the detection area 10 at least twice to detect the target gas, The amplitude of the resonance pulse caused by the target gas, that is, the amplitude high point, can be accurately calculated from at least two reflected lights reflected from the detection area 10.

Accordingly, the present invention improves the accuracy of determining the type of target gas in the detection area 10 and calculating the concentration of the target gas by ensuring that the amplitude of the resonance pulse and the peak value of the gas absorption curve are exactly consistent with each other in the detection area 10. False detection of target gas can be prevented.

Meanwhile, a computer program may be implemented to include instructions for causing a processor to perform each step included in the gas concentration measurement method according to the above-described embodiment. Additionally, a computer program including instructions for causing a processor to perform each step included in the method for measuring gas concentration according to the above-described embodiment may be recorded on a computer-readable recording medium.

Combinations of each step in each flowchart attached to the present invention may be performed by computer program instructions. Since these computer program instructions can be mounted on the processor of a general-purpose computer, special-purpose computer, or other programmable data processing equipment, the instructions performed through the processor of the computer or other programmable data processing equipment perform the functions described in each step of the flow chart. It creates the means to carry out these tasks. These computer program instructions may also be stored on a computer-usable or computer-readable recording medium that can be directed to a computer or other programmable data processing equipment to implement a function in a particular way, so that the computer program instructions are computer-usable or computer-readable. The instructions stored in the recording medium can also produce manufactured items containing instruction means that perform the functions described in each step of the flowchart. Computer program instructions can also be mounted on a computer or other programmable data processing equipment, so that a series of operational steps are performed on the computer or other programmable data processing equipment to create a process that is executed by the computer, thereby generating a process that is executed by the computer or other programmable data processing equipment. Instructions that perform processing equipment may also provide steps for executing the functions described in each step of the flowchart.

Additionally, each step may represent a module, segment, or portion of code containing one or more executable instructions for executing specified logical function(s). Additionally, it should be noted that in some alternative embodiments it is possible for the functions mentioned in the steps to occur out of order. For example, two steps shown in succession may in fact be performed substantially simultaneously, or the steps may sometimes be performed in reverse order depending on the corresponding function.

The above description is merely an illustrative explanation of the technical idea of the present invention, and those skilled in the art will be able to make various modifications and variations without departing from the essential quality of the present invention. Accordingly, the embodiments disclosed in the present invention are not intended to limit the technical idea of the present invention, but are for illustrative purposes, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention shall be interpreted in accordance with the claims below, and all technical ideas within the scope equivalent thereto shall be construed as being included in the scope of rights of the present invention.

According to an embodiment of the present invention, the target gas is detected at least twice by outputting laser light in different wavelength bands to the detection area, so that the amplitude of the resonance pulse is accurately calculated from the light reflected from the detection area to determine the gas absorption amount. It can be made to match the peak value of the curve. Accordingly, the present invention can prevent false detection of the target gas by increasing the accuracy of determining the type and calculating the concentration of the target gas in the detection area, and the present invention can be used in gas sensors and related technical fields.

100: Gas concentration measuring device 110: Light source
120: Amplification unit 130: Optical unit
140: light receiving unit 150: control module
151: pulse extraction unit 153: current variable unit
155: Concentration measurement unit

Claims (10)

A light source that generates light for the detection area;
a light receiving unit that receives light reflected from the detection area; and
The wavelength band of the light output from the light source is changed based on the first viewpoint reflection signal output from the light receiving unit, and the second viewpoint reflection signal output from the light receiving unit is changed by the first viewpoint reflection signal and the light with the changed wavelength band. A gas concentration measuring device including a control unit that measures the concentration of the target gas in the detection area based on the gas concentration measurement device. According to paragraph 1,
The control unit,
a pulse extraction unit that extracts one or more pulses including a resonance pulse from among the plurality of pulses of the first viewpoint reflection signal;
A current variable unit that changes the wavelength band of the light output from the light source by adjusting the size variable range of the current applied to the light source based on the one or more extracted pulses; and
A concentration measuring unit that measures the concentration of the target gas based on the difference between the amplitude of a reference pulse among the plurality of pulses of the first viewpoint reflection signal and the amplitude of the resonance pulse among the plurality of pulses of the second viewpoint reflection signal. Gas concentration measuring device. According to paragraph 2,
The current variable part,
A gas concentration measuring device that adjusts the size variable range of the current applied to the light source to decrease based on the one or more pulses. According to paragraph 2,
The pulse extraction unit,
A gas concentration measuring device for extracting the resonance pulse and one or more pulses adjacent to the resonance pulse from the plurality of pulses of the first viewpoint reflection signal. According to paragraph 1,
The control unit,
A gas concentration measuring device that controls the wavelength band of the light output from the light source to narrow by adjusting the variable range of the current applied to the light source. Outputting light in a first wavelength band generated from a light source according to a first current to a detection area, receiving light reflected from the detection area, and outputting a first viewpoint reflection signal;
extracting one or more pulses including a resonance pulse from the first viewpoint reflection signal;
generating a second current by adjusting a size variable range of the first current based on the one or more extracted pulses;
outputting light in a second wavelength band from the light source according to the second current, receiving light reflected from the detection area, and outputting a second viewpoint reflection signal; and
A gas concentration measurement method comprising measuring the concentration of the target gas in the detection area based on the first viewpoint reflection signal and the second viewpoint reflection signal. According to clause 6,
The step of generating the second current is,
A method of measuring gas concentration comprising generating the second current by reducing the size variable range of the first current based on the one or more pulses. According to clause 6,
The step of extracting one or more pulses includes:
A method of measuring gas concentration, comprising the step of extracting the resonance pulse and one or more pulses adjacent to the resonance pulse from the plurality of pulses of the first viewpoint reflection signal. According to clause 6,
The step of measuring the concentration of the target gas is,
calculating the amplitude of a reference pulse among the plurality of pulses of the first viewpoint reflection signal;
calculating the amplitude of a resonance pulse among the plurality of pulses of the second viewpoint reflection signal; and
A gas concentration measuring method comprising calculating the concentration of the target gas based on the difference between the amplitude of the reference pulse and the amplitude of the resonance pulse. A computer program stored on a computer-readable recording medium,
The computer program is,
A computer program including instructions for causing a processor to perform the gas concentration measurement method according to any one of claims 6 to 9.