阅读说明：本技术 试样分析装置 (Sample analyzer ) 是由 井上贵仁 内原博 涩谷享司 于 2020-05-12 设计创作，主要内容包括：本发明提供一种试样分析装置,在试样分析装置中能够降低维保的频率并且能够可靠地分析测定对象成分,本发明具备：加热炉(2),对由保持试样(W)的试样保持体保持的试样(W)进行加热；以及气体分析部(3),分析通过试样(W)的加热而产生的气体中包含的测定对象成分,气体分析部(3)具备：激光光源(12),向所述气体照射激光；以及光检测器(13),检测激光透过气体后的采样光的强度。(The present invention provides a sample analyzer capable of reducing maintenance frequency and reliably analyzing a component to be measured, the sample analyzer comprising: a heating furnace (2) that heats a sample (W) held by a sample holder that holds the sample (W); and a gas analysis unit (3) that analyzes a measurement target component contained in a gas generated by heating the sample (W), the gas analysis unit (3) comprising: a laser light source (12) that irradiates the gas with laser light; and a photodetector (13) for detecting the intensity of the sampling light after the laser light has passed through the gas.)

1. A sample analyzer is characterized in that,

the sample analyzer includes:

a heating furnace that heats the sample held by a sample holder that holds the sample; and

a gas analyzing section for analyzing a component to be measured contained in a gas generated by heating the sample,

the gas analysis unit includes:

a laser light source that irradiates laser light to the gas; and

and a photodetector for detecting the intensity of the sampling light after the laser light has passed through the gas.

2. The sample analyzer of claim 1,

the laser light source emits modulated light having a wavelength modulated at a predetermined modulation frequency.

3. The sample analyzer of claim 2,

the gas analysis unit further includes:

a first calculation unit that calculates a representative value that depends on the concentration of the measurement target component, using an intensity-related signal that is related to the intensity of the sampling light and a characteristic signal that obtains a predetermined correlation with respect to the intensity-related signal; and

and a second calculation unit that calculates the concentration of the component to be measured using the representative value obtained by the first calculation unit.

4. The sample analyzing apparatus according to claim 3,

the first calculation section calculates a sampled correlation value as the representative value, the sampled correlation value being a correlation value of the intensity-related signal and the characteristic signal,

the second calculation unit calculates the concentration of the measurement target component using the sample correlation value.

5. The sample analyzing apparatus according to any one of claims 1 to 4,

the sample analyzer analyzes a plurality of measurement target components contained in the gas,

the laser light source is provided with a plurality of laser light sources,

the plurality of laser light sources emit laser light having oscillation wavelengths corresponding to different measurement target components.

6. The sample analyzing apparatus according to any one of claims 1 to 5,

the plurality of measurement target components are CO₂、CO、SO₂、H₂O、NO_XAt least one of (a).

7. The sample analyzing apparatus according to any one of claims 1 to 6,

the sample analyzer further includes a gas flow path connecting the heating furnace and the gas analyzing unit, and introducing the gas from the heating furnace into the gas analyzing unit without dehydrating the gas with a dehydrating agent.

8. The sample analyzing apparatus according to any one of claims 1 to 7,

the sample analyzer further includes an analyzer using a non-dispersive infrared absorption method, which is different from the gas analyzer.

Technical Field

The present invention relates to a sample analyzer for analyzing a component to be measured contained in a sample.

Background

Conventionally, as shown in patent document 1, as an apparatus for analyzing carbon (C) and sulfur (S) in a solid sample such as steel, nonferrous metal, ceramics, coke, or the like, there is an apparatus as follows: a solid sample contained in a crucible is burned in a combustion furnace, and carbon dioxide (CO) contained in combustion gas generated from the solid sample is analyzed by a non-dispersive infrared absorption (NDIR) analyzer₂) Carbon monoxide (CO), sulfur dioxide (SO)₂) And (6) carrying out analysis.

In an apparatus for analyzing a solid sample using the NDIR analyzer, an infrared lamp is used, and infrared light having a wide range of absorption wavelengths including a component to be measured is emitted from the infrared lamp, and therefore, in order to measure the concentration of the component to be measured, a wavelength selective filter needs to be provided in front of a photodetector. By providing this wavelength selective filter, the amount of light detected by the photodetector decreases, and the SN ratio deteriorates. As a result, the analysis accuracy of the measurement target component is deteriorated particularly in the low concentration region.

On the other hand, as shown in patent document 2, there is a method of measuring SO contained in combustion gas by ultraviolet fluorescence₂And (4) a concentration device. By using the ultraviolet fluorescence method having higher sensitivity than the infrared absorption, SO can be detected even in a low concentration region₂The analysis is performed with high accuracy.

However, the ultraviolet light source using the ultraviolet fluorescence method has a problem that the amount of light is liable to decrease due to aging deterioration, and the ultraviolet light source needs to be frequently replaced, resulting in high maintenance frequency.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. Hei 6-265475

Patent document 2: japanese patent laid-open publication No. 2011-1699753

Disclosure of Invention

Problems to be solved by the invention

The present invention has been made to solve the above-described problems, and a main object of the present invention is to enable a sample analyzer to reduce the frequency of maintenance and to reliably analyze a component to be measured.

Technical solution for solving technical problem

That is, the sample analyzer of the present invention includes: a heating furnace that heats the sample held by a sample holder that holds the sample; and a gas analysis unit that analyzes a component to be measured included in a gas generated by heating the sample, the gas analysis unit including: a laser light source that irradiates laser light to the gas; and a photodetector for detecting the intensity of the sampling light after the laser light has passed through the gas.

In the sample analyzer, the gas analyzer includes: a laser light source that irradiates a gas with laser light; and a photodetector for detecting the intensity of the sampling light after the laser light has passed through the gas, so that by irradiating the gas with the laser light having an oscillation wavelength matching the component to be measured, there is no need to provide a wavelength selective filter in front of the photodetector, and it is possible to prevent a decrease in the light amount by the wavelength selective filter and increase the SN ratio. As a result, the component to be measured can be reliably analyzed. In addition, since the laser light source is used, the maintenance frequency can be reduced. As described above, according to the present invention, the frequency of maintenance can be reduced and the components to be measured can be reliably analyzed in the sample analyzer.

The laser light source is preferably a laser light source that emits modulated light having a wavelength modulated at a predetermined modulation frequency.

With this configuration, the component to be measured can be analyzed by using a wavelength modulation method (WMS: wavelength modulation spectrum) in which an intensity-related signal obtained by emitting modulated light having a wavelength modulated at a predetermined modulation frequency is used. As a result, the influence of the interfering component on the concentration of the measurement target component can be reduced.

Preferably, the gas analyzer further includes: a first calculation unit that calculates a representative value that depends on the concentration of the measurement target component, using an intensity-related signal that is related to the intensity of the sampling light and a characteristic signal that obtains a predetermined correlation with respect to the intensity-related signal; and a second calculation unit that calculates the concentration of the measurement target component using the representative value obtained by the first calculation unit.

With this configuration, in the wavelength modulation method, since the representative value depending on the concentration of the measurement target component is calculated from the intensity-related signal related to the intensity of the sampling light, and the concentration of the measurement target component is calculated using the representative value, the spectral computation process for concentration quantification, which is necessary in the conventional WMS, is not required, and the measurement target component contained in the solid sample can be reliably analyzed. In addition, because the ultraviolet fluorescence method is not used, the maintenance that the ultraviolet light source is not needed to be used and the ultraviolet light source is not needed to be frequently replaced is realized.

Specifically, it is preferable that the first calculation unit calculates a sample correlation value as the representative value, the sample correlation value being a correlation value between the intensity-related signal and the characteristic signal, and the second calculation unit calculates the concentration of the measurement target component using the sample correlation value. In addition, in the present invention, when calculating the correlation value, the correlation between the intensity-related signal and the characteristic signal is obtained, and the inner product of the intensity-related signal and the characteristic signal is also obtained.

With this configuration, since the sampling correlation value between the intensity-related signal related to the intensity of the sampling light and the characteristic signal is calculated and the concentration of the measurement target component is calculated using the calculated sampling correlation value, the characteristic of the absorption signal can be grasped with a very small number of variables without converting the absorption signal into the absorption spectrum, and the concentration of the measurement target component can be measured by a simple operation without performing a complicated spectral operation process. For example, although the number of data used in normal spectrum fitting needs to be several hundreds, in the present invention, concentration calculation can be performed with equal accuracy by using a maximum of about several to several tens correlation values. As a result, the load of the calculation process can be significantly reduced, a sophisticated arithmetic processing device is not required, the cost of the analysis device can be reduced, and the analysis device can be miniaturized.

Preferably, the sample analyzer of the present invention analyzes a plurality of components to be measured included in the gas, and the plurality of laser light sources are provided, and each of the plurality of laser light sources emits a laser beam having an oscillation wavelength corresponding to a different component to be measured.

Preferably, the plurality of measurement target components are CO₂、CO、SO₂、H₂O、NO_XAt least one of (a).

In the case of using an NDIR analyzer, water (H) contained in the gas₂O) as an interfering component, resulting in CO₂Concentration, CO concentration, SO₂The concentration gives rise to measurement errors. Therefore, a dehydrating agent for removing moisture contained in the gas is provided on the upstream side of the NDIR analyzer.

In the sample analyzer of the present invention, since it is not necessary to use an NDIR analyzer, a dehydrating agent may not be provided on the upstream side of the gas analyzer. Therefore, the sample analyzer of the present invention preferably further includes a gas flow path connecting the heating furnace and the gas analyzing unit, and the gas flow path introduces the gas from the heating furnace into the gas analyzing unit without dehydrating the gas with a dehydrating agent.

With this configuration, the dehydrating agent can be eliminated and maintenance such as periodic replacement of the dehydrating agent can be eliminated. In addition, since the dehydrating agent can be eliminated, the apparatus configuration can be simplified.

The sample analyzer of the present invention preferably further includes an analyzer (NDIR analyzer) using a non-dispersive infrared absorption method, which is different from the gas analyzing section. Thus, the measurement range can be expanded by using the gas analyzer and the NDIR analyzer in combination.

Effects of the invention

According to the present invention described above, the frequency of maintenance can be reduced and the components to be measured can be reliably analyzed in the sample analyzer.

Drawings

Fig. 1 is an overall schematic view of a sample analyzer according to an embodiment of the present invention.

Fig. 2 is an overall schematic view of the gas analysis unit of this embodiment.

Fig. 3 is a functional block diagram of the signal processing device of this embodiment.

Fig. 4 is a schematic diagram showing a method of modulating the laser oscillation wavelength according to this embodiment.

FIG. 5 shows the oscillation wavelength, the light intensity I (t), the logarithmic intensity L (t), and the characteristic signal F according to this embodiment_i(t), correlation value S_iAn example of the time series graph of (1).

Fig. 6 is a diagram showing a conceptual diagram of concentration calculation using the individual correlation value and the sampling correlation value according to this embodiment.

Fig. 7 is a diagram showing peak waveforms detected by the conventional metal analyzer and the metal analyzer of the present invention in the high concentration region and the low concentration region.

FIG. 8 shows SO₂A graph of peak waveforms detected by a conventional metal analyzer and the sample analyzer of the present invention when the concentration is 0.48 ppm.

Fig. 9 is a diagram showing the results of examining the linearity of a conventional metal analyzer and a sample analyzer of the present invention.

FIG. 10 shows SO in the case where a dehumidifier is provided and the case where a dehumidifier is not provided in the conventional metal analyzer and the sample analyzer of the present invention₂Graph of the measurement results of concentration.

Fig. 11 is a functional block diagram of a signal processing device of the second embodiment.

Fig. 12 is a time-series graph showing an example of the modulation signal, the output signal of the photodetector, and the measurement result according to the second embodiment.

Fig. 13 is a diagram showing a drive current (voltage) and a modulation signal in quasi-continuous oscillation.

Fig. 14 is a schematic diagram showing a measurement principle using quasi-continuous oscillation.

Fig. 15 is an overall schematic view of a gas analysis unit according to a modified embodiment.

Fig. 16 is a functional block diagram of a signal processing device according to a modified embodiment.

Fig. 17 is a schematic diagram showing an example of pulse oscillation timings and light intensity signals of the plurality of semiconductor lasers according to the modified embodiment.

Fig. 18 is an overall schematic diagram of a sample analyzer according to a modified embodiment.

Description of reference numerals:

100: a sample analyzer; w: a sample; r: a container (sample holder); 2: heating furnace; 3: a gas analysis section; 6: a gas flow path; 11: a pool; 12: a laser light source (semiconductor laser); 13: a photodetector; 162: a correlation value calculation unit (first calculation unit); 164: a density calculation unit (second calculation unit); 167: a synchronous detection signal generation unit (first calculation unit); 168: a density calculating section (second calculating section).

Detailed Description

< first embodiment >

Hereinafter, a sample analyzer 100 according to a first embodiment of the present invention will be described with reference to the drawings.

The sample analyzer 100 of the present embodiment analyzes carbon and sulfur in a sample such as steel, nonferrous metal, ceramic, coke, organic matter, mineral, and heavy oil. In the following, a metal analyzer that analyzes carbon and sulfur in a solid sample W will be described as an example of a sample analyzer.

Specifically, the sample analyzer 100 burns a solid sample W in an oxygen gas flow, and analyzes a component to be measured contained in the gas generated by the combustion by an infrared absorption method, and as shown in fig. 1, the sample analyzer 100 includes: a heating furnace 2 for heating and burning the container R for storing and holding the solid sample W; and a gas analysis unit 3 for analyzing a component to be measured contained in the gas generated by the combustion of the solid sample W. The container R of the present embodiment as a sample holder is a container called a crucible made of a magnetic material such as ceramic.

The heating furnace 2 has a heating space 2S in which a container R containing a solid sample W is disposed, and oxygen (O) is supplied to the heating space 2S₂) As a carrier gas. Therefore, the carrier gas supply path 4 is connected to the heating furnace 2. Further, the carrier gas supply path 4 is provided with a carrier gas purifier 42 for purifying the carrier gas (oxygen gas) from the gas bomb 41. The carrier gas purifier 42 may be omitted if the carrier gas in the gas bomb 41 is clean gas. Further, the carrier gas supply path 4 may be provided with an on-off valve 43, a pressure regulating valve 44, and a flow rate regulator 45 such as a capillary tube, as necessary.

The heating furnace 2 is a high-frequency induction heating furnace, and is provided with a heating mechanism 5 for high-frequency induction heating of the solid sample W in the container R disposed in the heating space 2S. The heating mechanism 5 includes a coil 51 and a power supply, not shown, for applying a high-frequency ac voltage to the coil 51. The coil 51 is wound along the side peripheral wall of the heating furnace 2. The coil 51 is provided at a height position surrounding the container R disposed in the heating space 2S.

When a high-frequency ac voltage is applied to the coil 51, an induced current flows in the vicinity of the surface of the solid sample W stored in the container R made of a magnetic material, and joule heat is generated in the solid sample W. Then, a combustion reaction by oxygen occurs with the heat generation, and the solid sample W is combusted to generate a gas (hereinafter also referred to as a sample gas). Further, the combustion improver may be stored in the container R together with the solid sample W, and the induction current may be applied to the combustion improver to heat the solid sample W.

The sample gas generated by the heating furnace 2 is introduced into the gas analyzer 3 through the gas channel 6. One end of the gas flow path 6 is connected to the heating furnace 2, and a dust filter 61 and a gas analysis unit 3 are provided from the upstream side of the flow path. The other end of the gas flow path 6 is open to the atmosphere. In the present embodiment, a pressure regulating valve 62 and a flow rate regulator 63 such as a capillary tube are provided between the dust filter 61 and the gas analyzing section 3, but these are not essential. Further, a flow rate regulator 64 such as a capillary tube and a flow meter 65 are provided downstream of the gas analyzer 3, but these are not essential. Since the gas flow path 6 of the present embodiment is not provided with a dehumidifier, at least the portion up to the gas analysis unit 3 is heated by the heating means 6H to, for example, 100 ℃. At least the dust filter 61 is also heated to 100 ℃ or higher by the heating means 6H.

The gas analyzer 3 measures a component to be measured (for example, CO or CO in this case) contained in the sample gas₂Or SO₂Etc.) of the gas analyzing section 3, as shown in fig. 2, includes: a cell 11 for introducing a sampling gas; a semiconductor laser 12 as a laser light source for irradiating the cell 11 with modulated laser light; a photodetector 13 disposed on an optical path of the sample light as the laser light transmitted through the cell 11, and receiving the sample light; and a signal processing device 14 that receives the output signal of the photodetector 13 and calculates the concentration of the measurement target component from the received output signal.

Each part will be explained.

The cell 11 is formed with an entrance port and an exit port for light made of a transparent material such as quartz, calcium fluoride, or barium fluoride which hardly absorbs light in the absorption wavelength range of the measurement target component. The cell 11 is provided with an inflow port for introducing the sample gas into the cell 11 and an outflow port for discharging the sample gas from the cell 11, which are not shown, and the sample gas is introduced from the inflow port and sealed in the cell 11.

The semiconductor Laser 12 is a Quantum Cascade Laser (QCL) as one type of the semiconductor Laser 12, and oscillates a Laser beam of a middle infrared wavelength (4 to 12 μm). The semiconductor laser 12 can modulate (change) an oscillation wavelength according to an applied current (or voltage). In addition, as long as the oscillation wavelength is variable, other types of laser light may be used, and temperature may be changed to change the oscillation wavelength.

The photodetector 13 may be a thermal type photodetector such as a relatively inexpensive thermopile, or may be another type of element such as HgCdTe, InGaAs, InAsSb, or PbSe equivalent type photoelectric element having good responsiveness.

The signal processing device 14 includes: an analog circuit including a buffer, an amplifier, and the like; a digital circuit including a CPU, a memory, and the like; and an AD converter and a DA converter which intervene between these analog/digital circuits; and the like, and functions as a light source control section 15 that controls the output of the semiconductor laser 12 and a signal processing section 16 that receives an output signal from the photodetector 13 and performs calculation processing on the value to calculate the concentration of the measurement target component, as shown in fig. 3, by the CPU and its peripheral devices operating in cooperation with each other based on a predetermined program stored in a predetermined area of the memory.

Each part will be described in detail below.

The light source control section 15 outputs a current (or voltage) control signal to control a current source (or voltage source) of the semiconductor laser 12. Specifically, the light source control unit 15 changes the drive current (or drive voltage) of the semiconductor laser 12 at a predetermined frequency, and modulates the oscillation wavelength of the laser light output from the semiconductor laser 12 at a predetermined frequency with respect to the center wavelength. Thereby, the semiconductor laser 12 emits modulated light modulated at a predetermined modulation frequency.

In this embodiment, the light source control unit 15 converts the drive current into a triangular waveform, and modulates the oscillation frequency into a triangular waveform (see "oscillation wavelength" in fig. 5). In practice, the drive current is modulated by another function so that the oscillation frequency becomes a triangular waveform. As shown in fig. 4, the oscillation wavelength of the laser beam is modulated so that the peak of the light absorption spectrum of the measurement target component is the center wavelength. The light source control unit 15 may change the drive current to a sinusoidal waveform, a sawtooth waveform, or an arbitrary function shape, and may modulate the oscillation frequency to a sinusoidal waveform, a sawtooth waveform, or an arbitrary function shape.

The signal processing unit 16 includes a logarithm calculation unit 161, a correlation value calculation unit (first calculation unit) 162, a storage unit 163, a density calculation unit (second calculation unit) 164, and the like.

The logarithm operation unit 161 performs a logarithm operation on a light intensity signal that is an output signal of the photodetector 13. The function i (t) indicating the temporal change of the light intensity signal obtained by the photodetector 13 is changed to "light intensity i (t)" of fig. 5, and is subjected to a logarithmic operation to be changed to "logarithmic intensity l (t)" of fig. 5.

The correlation value calculation unit 162 calculates each correlation value between the intensity-related signal related to the intensity of the sampling light and the plurality of predetermined characteristic signals. The feature signal is a signal for extracting a waveform feature of the intensity-related signal by correlating the intensity-related signal. As the characteristic signal, for example, a sine wave signal or various signals matching waveform characteristics to be extracted from other intensity-related signals can be used.

Hereinafter, an example of a case where a signal other than a sinusoidal signal is used as the characteristic signal will be described. The correlation value calculation unit 162 calculates the correlation value of each of the intensity-related signal related to the intensity of the sampling light and the plurality of characteristic signals for which correlation different from that of the sine wave signal (sine function) is obtained with respect to the intensity-related signal. Here, the correlation value calculation unit 162 uses the light intensity signal (logarithmic intensity l (t)) subjected to the logarithmic operation as the intensity-related signal.

The correlation value calculation unit 162 uses the feature signals F of the number equal to or greater than the number obtained by adding the number of types of the measurement target components to the number of types of the interference components_i(t) (i is 1, 2, … …, n), and a plurality of sampled correlation values S, which are correlation values between the intensity-related signal of the sampled light and each of the plurality of characteristic signals, are calculated based on the following expression (equation 1)_i. In addition, T in the mathematical formula 1 is a period of modulation.

[ mathematical formula 1]

S_i′＝S_i-R_i

Preferably, when calculating the sampled correlation value, the correlation value calculator 162 calculates the intensity-related signal l (t) of the sampled light and the plurality of characteristic signals F as shown in equation 1_i(t) correlation value S_iSubtracting the intensity-dependent signal L of the reference light₀(t) and a plurality of characteristic signals F_i(t) the correlation value, i.e. the reference correlation value R_iIs corrected to obtain a sample correlation value S_i'. Thus, the offset (offset) included in the sampling correlation value is removed, and the sampling correlation value becomes a correlation value proportional to the concentrations of the measurement target component and the interfering component, and the measurement error can be reduced. Alternatively, the reference correlation value may not be subtracted.

Here, the reference light is acquired at the same time as the sampling light, before and after the measurement, or at an arbitrary timing. The intensity-related signal or the reference correlation value of the reference light may be acquired in advance and stored in the storage unit 163. In addition, a method of simultaneously obtaining the reference light may be considered, for example, to provide two photodetectors 13, to branch the modulated light from the semiconductor laser 12 by a beam splitter or the like, and to use one as the sample light for measurement and the other as the reference light for measurement.

In the present embodiment, the correlation value calculation unit 162 uses, as the plurality of feature signals F, a function for which it is easier to grasp the waveform feature of the logarithmic intensity l (t) than the sine function_i(t) of (d). In the presence of a component to be measured (e.g., SO)₂) And an interference component (e.g. H)₂O), it is conceivable to use two or more characteristic signals F₁(t)、F₂(t) as two characteristic signals F₁(t)、F₂(t), for example, a function based on a lorentz function approximating the shape of the absorption spectrum and a differential function based on the function of the lorentz function can be considered. Further, instead of the function based on the lorentz function, a function based on a ford function, a function based on a gaussian function, or the like may be used as the characteristic signal. By using such a function for the feature signal, a larger correlation value can be obtained than when a sinusoidal function is used, and the measurement accuracy can be improved.

Preferably, the characteristic signal adjusts the offset so as to remove the dc component, i.e., so as to be zero when integrated over a modulation period. By doing so, it is possible to remove the influence of the variation in light intensity when the intensity-related signal is deviated. Instead of removing the dc component of the characteristic signal, the dc component of the intensity-related signal may be removed, or the dc components of both the characteristic signal and the intensity-related signal may be removed. Further, as the characteristic signal, an actual measurement value of the absorption signal of the measurement target component and/or the interference component, or a value simulating the actual measurement value can be used.

In addition, by combining two characteristic signals F₁(t)、F₂(t) is an orthogonal function sequence or a function sequence close to an orthogonal function sequence orthogonal to each other, and the feature of the logarithmic intensity l (t) can be extracted more efficiently, and the concentration obtained by a simultaneous equation described later can be increased.

The storage unit 163 stores the intensity-related signals and the characteristic signals F when the components to be measured and the interference components are present individually_i(t) the obtained individual correlation value, which is the correlation value per unit concentration of each of the measurement target component and each of the interfering components. A plurality of characteristic signals F for determining the individual correlation values_i(t) and a plurality of characteristic signals F used in the correlation value calculation unit 162_i(t) is the same.

Preferably, the storage unit 163 stores the individual correlation value obtained by subtracting the reference correlation value from the correlation value obtained when the measurement target component and each interference component are present individually and converting the obtained correlation value into the corrected individual correlation value per unit concentration. Thus, the deviation included in the individual correlation value is removed to obtain a correlation value proportional to the concentrations of the measurement target component and the interfering component, and the measurement error can be reduced. Alternatively, the reference correlation value may not be subtracted.

The concentration calculation unit 164 calculates the concentration of the measurement target component using the plurality of sampled correlation values obtained by the correlation value calculation unit 162.

Specifically, the concentration calculation unit 164 calculates the concentration of the measurement target component based on the plurality of sampled correlation values obtained by the correlation value calculation unit 162 and the plurality of individual correlation values stored in the storage unit 163. More specifically, the concentration calculation unit 164 calculates the concentration of the measurement target component by solving a simultaneous equation composed of the plurality of sampled correlation values obtained by the correlation value calculation unit 162, the plurality of individual correlation values stored in the storage unit 163, and the concentrations of the measurement target component and each of the interference components.

Next, an example of the operation of the analyzer 100 will be described as well as a detailed description of each of the above-described parts. Hereinafter, it is assumed that one measurement target component (for example, SO) is contained in the sample gas₂) And an interference component (e.g. H)₂O) is used.

< reference measurement >

First, the light source control unit 15 controls the semiconductor laser 12 to modulate the wavelength of the laser light with the modulation frequency and with the peak of the absorption spectrum of the measurement target component as the center. Further, before the reference measurement using the calibration gas, the reference measurement using the zero gas may be performed to measure the reference correlation value.

Subsequently, a calibration gas (gas having a known component concentration) is introduced into the cell 11 by an operator or automatically, and reference measurement is performed. The reference measurement is performed for the calibration gas in which the component to be measured exists alone and the calibration gas in which the disturbance component exists alone.

Specifically, in the reference measurement, the logarithm arithmetic unit 161 receives the output signal of the photodetector 13 and calculates the logarithmic intensity l (t). Then, the correlation value calculation unit 162 calculates the logarithmic strength l (t) and the two feature signals F₁(t)、F₂(t) dividing a value obtained by subtracting the reference correlation value from the correlation value by the concentration of the span gas, thereby calculating a correlation value, i.e., an individual correlation value, for each span gas per unit concentration. Alternatively, instead of calculating the individual correlation values, the relationship between the calibrant gas concentration and the correlation value of the calibrant gas may be stored.

The details are as follows.

Gas guide for calibration for separately containing components to be measuredThe correlation value calculating unit 162 calculates the correlation value S of the component to be measured by entering the cell 1_1t、S_2t(refer to fig. 6). Here, S_1tIs a correlation value, S, with the first characteristic signal_2tIs a correlation value with the second characteristic signal. Then, the correlation value calculating section 162 will calculate the correlation values S from these correlation values_1t、S_2tSubtracting a reference correlation value R_iThe obtained value is divided by the calibrant gas concentration C of the component to be measured_tThereby calculating individual correlation values S_1t、S_2t. Further, the gas concentration C for calibration of the component to be measured_tThe signal processing unit 16 is inputted in advance by a user or the like.

Further, the correlation value S of the interference component is calculated by the correlation value calculating unit 162 by introducing the calibration gas in which the interference component alone exists into the cell 1_1i、S_2i(refer to fig. 6). Here, S_1iIs a correlation value, S, with the first characteristic signal_2iIs a correlation value with the second characteristic signal. Then, the correlation value calculating part 162 calculates the correlation values S from these correlation values S_1i、S_2iThe value obtained by subtracting the reference correlation value is divided by the calibrant gas concentration C of the interfering component_iCalculating individual correlation values S_1i、S_2i. Further, the calibration gas concentration C of the disturbance component_iThe signal processing unit 16 is inputted in advance by a user or the like.

The individual correlation value S calculated by the above_1t、S_2t、S_1i、S_2iIs stored in the storage section 163. The reference measurement may be performed before shipment of the product, or may be performed periodically.

< measurement by sampling >

The light source control unit 15 controls the semiconductor laser 12 to modulate the wavelength of the laser beam with the modulation frequency and with the peak of the absorption spectrum of the measurement target component as the center.

Subsequently, the sampling gas generated in the heating furnace 2 is introduced into the cell 11 through the gas flow path 6 by an operator or automatically, and sampling measurement is performed.

Specifically, in the sampling measurement, the logarithm arithmetic unit 161 receives the output signal of the photodetector 13Number, logarithmic intensity l (t) is calculated. Then, the correlation value calculation unit 162 calculates the logarithmic strength l (t) and the plurality of feature signals F₁(t)、F₂(t) sampled correlation value S₁、S₂Calculating a reference correlation value R subtracted from the correlation value_iThe resulting sampled correlation value S₁’、S₂' (refer to FIG. 6).

Then, the concentration calculation unit 164 compares the sampled correlation value S calculated by the correlation value calculation unit 162 with the correlation value S₁’、S₂', individual correlation value S of storage section 163_1t、S_2t、S_1i、S_2iAnd the concentrations C of the measurement target component and each of the interfering components_tar、C_intThe following two-dimensional simultaneous equations are solved.

[ mathematical formula 2]

s_1tC_tar+s_1iC_int＝S₁′

s_2tC_tar-rs_2iC_int＝S₂′

Thus, by solving the simultaneous equations of the above formula (formula 2), the concentration C of the measurement target component from which the influence of the disturbance is removed can be determined by a simple and reliable operation_tar。

Even when it is assumed that two or more interference components may exist, the concentration of the measurement target component from which the influence of the interference is removed can be determined in the same manner by adding a single correlation value of the number of interference components and solving a simultaneous equation having the same number of elements as the number of component types.

That is, in the case where n types of gases exist by combining the component to be measured and the interfering component, if the individual correlation value of the kth gas type of the mth characteristic signal is S_mkC represents the concentration of the kth gas species_kThe m-th characteristic signal F_m(t) sample correlation value is set to S_m', the following expression (expression 3) holds.

[ mathematical formula 3]

By solving the n-ary simultaneous equation expressed by the equation (equation 3), the concentration of each gas of the measurement target component and the interference component can be determined.

Next, SO of a sample analyzer 100 (hereinafter, also referred to as "the present embodiment") using the gas analyzer 3 of the present embodiment and a metal analyzer (hereinafter, also referred to as "NDIR") using a conventional NDIR analyzer are measured₂The difference in the analytical accuracy of the concentration will be described. In addition, in a metal analyzer using a conventional NDIR analyzer, a dehumidifier is provided upstream of the NDIR analyzer.

FIG. 7 shows the NDIR in the high concentration region (2.4 to 20.10ppm) and the low concentration region (0.48 to 2.4ppm) and the peak waveforms detected in the present example. As can be seen from fig. 7, in the low concentration region, the peak waveform detected by the present embodiment is smoother than the peak waveform detected by NDIR.

In addition, SO is shown in FIG. 8₂The peak waveform detected by NDIR and this example at a concentration of 0.48 ppm. As is clear from fig. 8, the SN ratio in NDIR is 1.3, whereas in the present example, the SN ratio is 35.9. Thus, by using this example, the SN ratio was about 27 times as high as NDIR.

Next, fig. 9 shows results of examining NDIR and linearity of the present example. In the graph shown in fig. 9, the vertical axis represents the measured concentration, and the horizontal axis represents the theoretical concentration. As is clear from fig. 9, it is difficult to detect a concentration of 1ppm or less in NDIR, and variations in the detection concentration of NDIR are large. On the other hand, in the present example, even at a concentration of 1ppm or less, it is possible to detect the concentration without variation as in the case of the above concentration.

Fig. 10 shows NDIR, SO in the case where a dehumidifier is provided and the case where a dehumidifier is not provided in the present embodiment₂The results of concentration measurement. In NDIR, measurement of a case where a dehumidifier is installed and a case where a dehumidifier is not installedRatio of results (SO without dehumidifier)₂SO in case of concentration "/" with dehumidifier₂Concentration ") was 121.4%, whereas in the present example, the ratio thereof was 100.9%. As can be seen, in the present embodiment, the influence of disturbance due to water removal can be eliminated without providing a dehumidifier.

< Effect of the first embodiment >

According to the sample analyzer 100 of the present embodiment configured as described above, the gas analyzer 3 includes: a laser light source 12 that irradiates a gas with laser light; and the photodetector 13 for detecting the intensity of the sampling light after the laser light has passed through the gas, so that by irradiating the gas with the laser light having an oscillation wavelength matching the component to be measured, there is no need to provide a wavelength selective filter in front of the photodetector 13, and it is possible to prevent a decrease in the light amount by the wavelength selective filter and to increase the SN ratio. As a result, the component to be measured can be reliably analyzed. In addition, since the laser light source 12 is used, the maintenance frequency can be reduced. As described above, according to the present embodiment, the sample analyzer 100 can reduce the frequency of maintenance and can reliably analyze the measurement target component.

Further, according to the present embodiment, in the WMS using the intensity-related signal obtained by emitting the modulated light modulated at the predetermined modulation frequency, the representative value depending on the concentration of the measurement target component is calculated from the intensity-related signal related to the intensity of the sampling light, and the concentration of the measurement target component is calculated using the representative value. Specifically, in the present embodiment, the logarithmic intensity l (t) which is an intensity-related signal related to the intensity of the sampling light and the plurality of characteristic signals F for the logarithmic intensity l (t) are calculated_i(t) respective correlation values S_iUsing a plurality of calculated correlation values S_iSince the concentration of the component to be measured is calculated, the characteristics of the absorption signal can be grasped with a considerably small number of variables without converting the absorption signal into an absorption spectrum, and the characteristic can be easily obtained without performing complicated spectral calculation processingThe single calculation measures the concentration of the measurement target component. For example, although the number of data used in normal spectrum fitting needs to be several hundreds, in the present invention, concentration calculation can be performed with equal accuracy by using a maximum of about several to several tens correlation values. As a result, the load of the calculation process can be significantly reduced, a sophisticated arithmetic processing device is not required, the cost of the sample analyzer 100 can be reduced, and the size can be reduced.

In addition, in the sample analyzer 100 according to the present embodiment, since the ultraviolet fluorescence method is not used, it is not necessary to use an ultraviolet light source, and maintenance such as frequent replacement of the ultraviolet light source is not necessary.

In addition, in the sample analyzer 100 of the present embodiment, since the component to be measured can be analyzed without using an NDIR analyzer, a dehydrating agent is not required, and maintenance such as periodic replacement of the dehydrating agent is not required. In addition, since the dehydrating agent can be eliminated, the apparatus configuration can be simplified. That is, the gas flow path 6 of the present embodiment can be configured without providing a dehydrating agent.

< second embodiment >

Hereinafter, a sample analyzer 100 according to a second embodiment of the present invention will be described with reference to the drawings.

The sample analyzer 100 according to the second embodiment is different from the signal processor 14 according to the first embodiment in configuration. Other configurations are the same as those of the first embodiment, and the description thereof will be omitted below.

The signal processing device 14 includes: an analog circuit including a buffer, an amplifier, and the like; a digital circuit including a CPU, a memory, and the like; and an AD converter and a DA converter which intervene between these analog/digital circuits; and the like, and functions as a light source control section 15 that controls the output of the semiconductor laser 12 and a signal processing section 16 that receives an output signal from the photodetector 13 and performs calculation processing on the value to calculate the concentration of the measurement target component, as shown in fig. 11, by the CPU and its peripheral devices operating in cooperation with each other based on a predetermined program stored in a predetermined area of the memory.

Each part will be described in detail below.

The light source control unit 15 controls the current source (or voltage source) of the semiconductor laser 12 by outputting a current (or voltage) control signal, and by this control, changes the drive current (or drive voltage) at a predetermined frequency, and modulates the oscillation wavelength of the laser light output from the semiconductor laser 12 at the predetermined frequency.

In this embodiment, the light source control unit 15 converts the drive current into a sinusoidal waveform, and modulates the oscillation frequency into a sinusoidal waveform (see the modulation signal in fig. 12). As shown in fig. 4, the oscillation wavelength of the laser beam is modulated around the peak of the light absorption spectrum of the measurement target component.

The signal processing unit 16 includes an absorbance signal calculation unit 166, a synchronous detection signal generation unit (first calculation unit) 167, a concentration calculation unit (second calculation unit) 168, and the like.

The absorbance signal calculation unit 166 calculates the logarithm of the ratio of the light intensity of the laser beam (hereinafter, also referred to as "transmitted light") after passing through the cell 11 in a state in which the sample gas is sealed and light absorption is generated by the measurement target component therein, to the light intensity of the laser beam (hereinafter, also referred to as "reference light") after passing through the cell 11 in a state in which the light absorption is substantially zero (hereinafter, also referred to as "intensity ratio logarithm").

More specifically, when the light intensity of the transmitted light and the light intensity of the reference light are both measured by the photodetector 13 and the measurement result data is stored in a predetermined area of the memory, the absorbance signal calculation unit 166 calculates the logarithm of intensity ratio (hereinafter also referred to as an absorbance signal) by referring to the measurement result data.

Therefore, it is a matter of course that the former measurement (hereinafter, also referred to as sampling measurement) is performed for each sampling gas. The latter measurement (hereinafter, also referred to as a reference measurement) may be performed each time before or after the sample measurement, or the latter measurement may be performed only once at an appropriate timing, for example, and the results may be stored in a memory and used in common for each sample measurement.

In this embodiment, the light absorption is substantially achievedA zero gas, for example, N, in which the light absorption of the component to be measured is substantially zero in a wavelength range in which the light absorption can occur₂The gas is sealed in the cell 11, but other gases may be used, and the inside of the cell 11 may be evacuated.

The synchronous detection signal generation section 167 performs lock-in detection (lock-in detection) on the absorbance signal calculated by the absorbance signal calculation section 66 using a sinusoidal signal (reference signal) having a frequency n times (n is an integer equal to or greater than 1) the modulation frequency, extracts frequency components of the reference signal from the absorbance signal, and generates a synchronous detection signal. The phase-lock detection may be performed by digital operation or by operation using an analog circuit. Further, the extraction of the frequency component may be performed not only by phase-locked detection but also by a fourier series expansion method, for example.

The concentration calculation unit 168 calculates the concentration of the component to be measured based on the synchronous detection result of the synchronous detection signal generation unit 167.

Next, an example of the operation of the analyzer 100 will be described as well as a detailed description of the above-described parts.

First, as described above, the light source control unit 15 controls the semiconductor laser 12 to modulate the wavelength of the laser beam with the modulation frequency and with the peak of the absorption spectrum of the measurement target component as the center.

Next, if the zero point gas is sealed in the cell 11 by an operator or automatically, the absorbance signal calculation unit 166 that has detected this situation performs reference measurement.

Specifically, the output signal from the photodetector 13 in the state of the zero gas sealed cell 11 is received, and the value is stored in the measurement result data storage unit. The reference light intensity, which is the value of the output signal of the photodetector 13 measured by reference, is represented by a time-series graph as shown in fig. 12 (a). That is, only the change in the optical output due to the modulation of the drive current (voltage) of the laser light appears in the output signal of the photodetector 13.

Therefore, if the sample gas is enclosed in the cell 11 by an operator or automatically, the absorbance signal calculation unit 166 performs a sampling measurement. Specifically, an output signal from the photodetector 13 in a state where the sample gas is sealed in the cell 11 is received, and the value is stored in a predetermined area of the memory. The time series graph shows the transmitted light intensity, which is the value of the output signal of the photodetector 13 in the sample measurement, as shown in fig. 12 (b). It is known that peaks due to absorption occur every half period of modulation.

Next, the absorbance signal calculation unit 166 calculates the logarithm of the intensity ratio of the light intensity of the transmitted light to the light intensity of the reference light (absorbance signal) in synchronization with each measurement data and the modulation cycle. Specifically, an operation equivalent to the following expression (expression 4) is performed.

[ mathematical formula 4]

Here, D_m(t) the intensity of transmitted light, D_z(t) is the reference light intensity, and A (t) is the log intensity ratio (absorbance signal). If the absorbance signal is represented on a graph with time taken as the abscissa, it becomes as shown in fig. 12 (c).

In this case, the logarithm of the transmitted light intensity may be obtained after calculating the ratio of the transmitted light intensity to the reference light intensity, or the logarithm of the transmitted light intensity and the logarithm of the reference light intensity may be obtained separately and subtracted from each other.

Next, the synchronous detection signal generation section 167 phase-lock-detects the absorbance signal with a reference signal having a frequency 2 times the modulation frequency, that is, extracts a frequency component 2 times the modulation frequency, and stores the synchronous detection signal (hereinafter, also referred to as phase-lock data) in a predetermined area of the memory.

The value of the lock data is proportional to the concentration of the measurement target component, and the concentration calculation unit 168 calculates a concentration indication value indicating the concentration of the measurement target component based on the value of the lock data.

Thus, according to this configuration, even if the laser intensity varies for some reason, a constant deviation is added to the intensity ratio, and the waveform does not change. Therefore, the value of each frequency component calculated by performing the phase-lock detection does not change, and the concentration indication value does not change, so that highly accurate measurement can be expected.

The reason for this will be described in detail below.

In general, if fourier series expansion is performed on the absorbance signal a (t), it is represented by the following formula (mathematical formula 5).

In addition, a in the formula (equation 5)_nIs a value proportional to the concentration of the component to be measured, based on the value a_nThe concentration calculation unit 168 calculates a concentration indication value indicating the concentration of the measurement target component.

[ math figure 5]

Here, f_mIs the modulation frequency and n is a multiple relative to the modulation frequency.

On the other hand, a (t) is also represented by the above formula (formula 1).

Next, when the laser intensity fluctuates by α times for some reason during the measurement, the absorbance signal a' (t) is expressed by the following expression (expression 6).

[ mathematical formula 6]

As is clear from this expression (equation 6), when a' (t) is added to the absorbance signal A (t) only when the laser intensity is not varied, the value a of each frequency component is a constant value_nNor changed.

Therefore, the density instruction value determined based on the value of the frequency component 2 times the modulation frequency has no influence.

The above is an operation example of the sample analyzer 100 in the case where the sample gas does not contain any interfering component other than the measurement target component.

Then, one or more disturbance components (for example, H) having light absorption at the peak light absorption wavelength of the component to be measured included in the sample gas₂O) is described below.

First, the principle will be explained.

Since the shapes of the light absorption spectra of the measurement target component and the interference component are different, the waveforms of the absorbance signals when the components are present alone are different, and the proportions of the frequency components are different (linearly independent). By utilizing this, the concentration of the measurement target component in which the influence of the interference is corrected can be obtained by solving the simultaneous equations using the relationship between the value of each frequency component of the measured absorbance signal and each frequency component of the absorbance signals of the measurement target component and the interference component, which are obtained in advance.

A represents the absorbance signal per unit concentration when the component to be measured and the interfering component are present independently_m(t)、A_i(t) each frequency component of each absorbance signal is represented by a_nm，a_niThe following equations (equation 7 and equation 8) are established.

[ math figure 7]

[ mathematical formula 8]

The concentrations of the measurement target component and the interfering component are represented by C_m、C_iThe absorbance signal value a (t) in the present case is represented by the following formula (formula 9) according to the linearity of each absorbance.

[ mathematical formula 9]

Here, if f of A (t)_mAnd 2f_mRespectively is a₁、a₂Then, the following simultaneous equation (equation 10) is established based on the above equation (equation 9).

[ mathematical formula 10]

a_1mC_m+a_1iC_i＝a₁

a_2mC_m+a_2iC_i＝a₂

Frequency components a in the case where the measurement object component and the interference component are present independently_nm、a_niSince (n is a natural number, where n is 1 or 2) can be obtained by flowing each calibration gas in advance, the concentration C of the measurement target gas from which the influence of interference has been removed can be determined by a simple and reliable operation of solving the simultaneous equations of the above expression (expression 10)_m。

The analyzer 100 operates based on the above-described principle.

That is, the analyzer 100 in this case performs preliminary measurement or the like by, for example, flowing the calibration gas in advance, and thereby the frequency component a of each absorbance signal in the case where the measurement target component and the interference component are present separately_1m、a_2m、a_1i、a_2iStored in a prescribed area of the memory. Specifically, as in the previous example, the measured light intensity and the reference light intensity are measured for each of the measured component and the disturbance component, the logarithm of the intensity ratio (absorbance signal) between them is calculated, and the frequency component a is obtained by performing lock-in detection or the like based on the logarithm of the intensity ratio_1m、a_2m、a_1i、a_2iThese frequency components are stored. Alternatively, the following may be adopted: storing the absorbance signal A per unit concentration without storing the frequency component_m(t)、A_i(t) calculating the frequency component a from the above-mentioned expressions (expression 7, expression 8)_1m、a_2m、a_1i、a_2i。

Then, the analysis device 100 specifies the measurement target component and the disturbance component based on an input from the operator or the like.

Next, the absorbance signal calculation unit 166 calculates the intensity ratio logarithm a (t) according to expression (expression 4).

Then, the synchronous detection signal generating section 167 uses the signal having the modulation frequency f_mAnd a frequency 2f of 2 times thereof_mThe reference signal performs phase-locked detection on the intensity comparison number to extract each frequency component a₁、a₂(phase lock data) and stores it in a prescribed area of the memory.

Then, the density calculation section 168 calculates the value a of the lock data₁、a₂And a frequency component a stored in a memory_1m、a_2m、a_1i、a_2iThe value of (C) is applied to the above expression (expression 10), or an equivalent operation is performed to calculate the concentration (or concentration indication value) C indicating the concentration of the measurement target gas from which the influence of the disturbance is removed_m. At this time, the concentration (or concentration indication value) C of each interfering component may be calculated_i。

Even when it is assumed that the number of interference components is 2 or more, the concentration of the measurement target component from which the influence of interference is removed can be determined in the same manner by merely adding higher-order frequency components of the number of interference components and obtaining a simultaneous equation having the same number of elements as the number of component types.

That is, in general, if the i × f of the kth gas species is set in the case where n kinds of gases exist by combining the measurement target component and the interfering component_mHas a frequency component of_ikC represents the concentration of the kth gas species_kThe following expression (expression 11) is established.

[ mathematical formula 11]

By obtaining the n-ary simultaneous equation expressed by this equation (equation 11), the concentration of each gas of the measurement target component and the interference component can be determined.

Further, by adding a harmonic component of a larger order than n, creating a simultaneous equation of a larger number of elements than the number of gas types, and determining each gas concentration by the least square method, it is possible to determine a concentration that is smaller even with respect to a measurement noise error.

< Effect of the second embodiment >

According to the sample analyzer 100 of the present embodiment, the gas analyzer 3 includes: a laser light source 12 that irradiates a gas with laser light; and the photodetector 13 for detecting the intensity of the sampling light after the laser light has passed through the gas, so that by irradiating the gas with the laser light having an oscillation wavelength matching the component to be measured, there is no need to provide a wavelength selective filter in front of the photodetector 13, and it is possible to prevent a decrease in the light amount by the wavelength selective filter and to increase the SN ratio. As a result, the component to be measured can be reliably analyzed. In addition, since the laser light source 12 is used, the maintenance frequency can be reduced. As described above, according to the present embodiment, the sample analyzer 100 can reduce the frequency of maintenance and can reliably analyze the measurement target component.

Further, according to the present embodiment, in the WMS using the intensity-related signal obtained by emitting the modulated light modulated at the predetermined modulation frequency, the representative value depending on the concentration of the measurement target component is calculated from the intensity-related signal related to the intensity of the sampling light, and the concentration of the measurement target component is calculated using the representative value. Specifically, in the present embodiment, since a frequency component n times the modulation frequency is extracted from the absorbance signal a (t) and the concentration of the measurement target component is calculated using the extracted frequency component, the concentration of the measurement target component can be measured by a simple calculation without performing a complicated spectrum calculation process. As a result, a high-level arithmetic processing device is not required, the cost of the sample analyzer 100 can be reduced, and the size can be reduced.

In addition, in the sample analyzer 100 according to the present embodiment, since the ultraviolet fluorescence method is not used, it is not necessary to use an ultraviolet light source, and maintenance such as frequent replacement of the ultraviolet light source is not necessary.

Furthermore, in the sample analyzer 100 of the present embodiment, since the component to be measured can be analyzed without using an NDIR analyzer, the dehydrating agent is not required, and maintenance such as periodic replacement of the dehydrating agent is not required. In addition, since the dehydrating agent can be eliminated, the apparatus configuration can be simplified. That is, the gas flow path 6 of the present embodiment can be configured without providing a dehydrating agent.

< other modified embodiment >

The present invention is not limited to the above embodiments.

For example, although the logarithm calculation unit 161 of the first embodiment performs a logarithm calculation on the light intensity signal of the photodetector 13, a logarithm of the ratio of the intensity of the sample light to the intensity of the reference light (so-called absorbance) may be calculated using the light intensity signal of the photodetector 13. In this case, the logarithm calculation unit 161 may calculate the absorbance by calculating the logarithm of the intensity of the sample light and the logarithm of the intensity of the reference light and subtracting them, or may calculate the absorbance by obtaining the logarithm of the ratio after obtaining the intensity of the sample light and the intensity of the reference light.

Further, the correlation value calculation unit 162 of the first embodiment calculates the correlation value between the intensity-related signal and the feature signal, but may calculate the inner product value of the intensity-related signal and the feature signal.

In the first embodiment, the storage unit 163 stores the individual correlation value corrected using the reference correlation value, but the storage unit 163 may store the individual correlation value before correction in advance, and the density calculation unit 164 may obtain the individual correlation value corrected by subtracting the reference correlation value from the individual correlation value before correction and converting the result into the value per unit density.

The plurality of characteristic signals are not limited to the first embodiment, and may be functions different from each other. In addition, as the characteristic signal, a function indicating a waveform (actually measured spectrum) of light intensity, logarithmic intensity, or absorbance obtained by flowing a calibration gas having a known concentration, for example, may be used. In the case of measuring the concentration of one measurement target component, at least one characteristic signal may be used.

The light source control unit 15 of each of the above embodiments continuously oscillates (CW) the semiconductor laser, but as shown in fig. 13, the semiconductor laser may be quasi-continuously oscillated (quasi-CW). In this case, the light source control unit 15 outputs a current (or voltage) control signal to control the current source (or voltage source) of each semiconductor laser 12 so that the drive current (drive voltage) of the current source (or voltage source) is equal to or higher than a predetermined threshold value for pulse oscillation. Specifically, the light source control unit 15 performs quasi-continuous oscillation by pulse oscillation of a predetermined pulse width (for example, 10 to 50ns, duty ratio 5%) that is repeated at a predetermined period (for example, 1 to 5 MHz). The light source control unit 15 changes the drive current (drive voltage) of the current source (or voltage source) at a predetermined frequency at a wavelength scanning value smaller than the pulse oscillation threshold value, thereby generating a temperature change and scanning the oscillation wavelength of the laser light. The modulation signal for modulating the drive current is varied in a triangular waveform, a sawtooth waveform, or a sinusoidal waveform, and has a frequency of, for example, 1 to 100 Hz.

As described above, the optical intensity signal obtained by the photodetector 13 by quasi-continuous oscillation of the semiconductor laser is shown in fig. 14. In this way, an absorption spectrum can be obtained in the entire pulse train. Quasi-continuous oscillation has a smaller power consumption of the light source than continuous oscillation, facilitates heat dissipation, and can achieve a longer life of the light source.

As shown in fig. 15, the gas analyzer 3 may include a plurality of semiconductor lasers 12 as a light source for irradiating the cell 11 with laser light. As shown in fig. 16, the signal processing device 14 functions as a light source control unit 15 that controls the output of the semiconductor laser 12, a signal separation unit 17 that separates the signal of each semiconductor laser 12 from the light intensity signal obtained by the photodetector 13, and a signal processing unit 16 that receives the signal of each semiconductor laser 12 separated by the signal separation unit 17 and calculates the value of the signal to calculate the concentration of the component to be measured.

The light source control unit 15 pulse-oscillates each of the plurality of semiconductor lasers 12 and modulates the oscillation wavelength of the laser light at a predetermined frequency. The light source control unit 15 controls the plurality of semiconductor lasers 12 to have oscillation wavelengths corresponding to different measurement target components, and causes the plurality of semiconductor lasers to pulse-oscillate with the same oscillation period and at different oscillation times.

Specifically, the light source control unit 15 outputs a current (or voltage) control signal to control the current source (or voltage source) of each semiconductor laser 12. As shown in fig. 13, the light source control unit 15 of the present embodiment causes each semiconductor laser 12 to perform quasi-continuous oscillation (quasi-CW) by pulse oscillation of a predetermined pulse width (for example, 10 to 100ns, with a duty ratio of 5%) that is repeated at a predetermined period (for example, 0.5 to 5 MHz).

As shown in fig. 13, the light source control unit 15 changes the driving current (driving voltage) of the current source (or voltage source) at a predetermined frequency to generate a temperature change, thereby scanning the oscillation wavelength of the laser light. As shown in fig. 4, the oscillation wavelength of the laser light of each semiconductor laser is modulated around the peak of the light absorption spectrum of the measurement target component. The modulation signal for changing the drive current is a signal that changes in a triangular waveform, a sawtooth waveform, or a sinusoidal waveform and has a frequency of, for example, 100Hz to 10 kHz. Fig. 13 shows an example in which the modulation signal changes in a triangular waveform.

As described above, the optical intensity signal obtained by the photodetector 13 by quasi-continuously oscillating one semiconductor laser 12 is shown in fig. 14. In this way, an absorption signal can be obtained in the entire burst.

The light source control unit 15 causes the plurality of semiconductor lasers 12 to perform pulse oscillation at different timings. Specifically, as shown in fig. 17, the plurality of semiconductor lasers 12 are sequentially pulsed, and 1 pulse of each of the other semiconductor lasers 12 is included in 1 cycle of the pulse oscillation of one semiconductor laser 12. That is, the pulses adjacent to each other in one semiconductor laser 12 include 1 pulse of each of the other semiconductor lasers 12. At this time, the pulses of the plurality of semiconductor lasers 12 oscillate without being repeated.

The signal separation unit 17 separates the signals of the plurality of semiconductor lasers 12 based on the light intensity signal obtained by the photodetector 13. The signal separation unit 17 of the present embodiment includes: a plurality of sample-and-hold circuits provided corresponding to the plurality of semiconductor lasers 12, respectively; and an AD converter for digitally converting the light intensity signal separated by the sample-and-hold circuit. In addition, the sample-and-hold circuit and the AD converter may be one common to the plurality of semiconductor lasers 12.

The sample hold circuit acquires a sampling signal synchronized with the current (or voltage) control signal of the corresponding semiconductor laser 12, and separates and holds the signal of the corresponding semiconductor laser 12 from the light intensity signal of the photodetector 13 at a timing synchronized with the timing of pulse oscillation of the semiconductor laser 12. The sample-and-hold circuit is configured to separate and hold a signal corresponding to the second half of the pulse oscillation of the semiconductor laser 12. By collecting a plurality of signals of the semiconductor lasers 12 separated by the signal separating section 17 to become one optical absorption signal, an optical absorption signal having a wavelength resolution higher than that of an optical absorption signal obtained when one semiconductor laser 12 is quasi-continuously oscillated can be obtained. Here, since the absorption change position within the pulse changes according to the modulation signal, the waveform can be reproduced by collecting signals at the same timing for the pulse oscillation. In addition, since the signal corresponding to a part of the pulse oscillation is separated by the sample-and-hold circuit, the AD converter may be an AD converter whose processing speed is slow. The plurality of light absorption signals obtained for each of the semiconductor lasers 12 may be time-averaged and used.

In this way, the signal processing unit 16 calculates the concentration of the measurement target component corresponding to each semiconductor laser 12 using the absorption signal of each semiconductor laser 12 separated by the signal separating unit 17. The signal processing unit 16 calculates the concentration of the measurement target component in the same manner as in the above-described embodiment.

The functions of the gas analyzing unit according to the first and second embodiments function as a first calculating unit that calculates a representative value depending on the concentration of the measurement target component using an intensity-related signal related to the intensity of the sampling light and a characteristic signal that obtains a predetermined correlation with respect to the intensity-related signal, and a second calculating unit that calculates the concentration of the measurement target component using the representative value obtained by the first calculating unit, but other calculation methods may be used.

The light source is not limited to a semiconductor laser, and may be any other type of laser, as long as it is a single-wavelength light source having a half-value width sufficient to ensure measurement accuracy and capable of wavelength modulation. In addition, the light source may be intensity-modulated.

In each of the above embodiments, the gas flow path 6 is provided with one gas analysis unit 3, but as shown in fig. 18, an NDIR analyzer 8 may be provided in addition to the gas analysis unit 3. In this case, a dehumidifier 7 is provided on the gas flow path 6 downstream of the gas analysis unit 3, and an NDIR analyzer 8 is provided on the downstream side of the dehumidifier 7. Further, the dehumidifier 7 may be provided upstream of the gas analyzer 3. The gas channel 6 may be divided into a first channel for supplying gas to the gas analyzer 3 and a second channel for supplying gas to the NDIR analyzer 8. In this way, the gas analyzer 3 and the NDIR analyzer 8 are used in combination, whereby the measurement range can be expanded. For example, the measurement range of the gas analyzer 3 is set to 200ppm or less, the measurement range of the NDIR analyzer 8 is set to 200ppm to 5%, the measurement result of the gas analyzer 3 is used in the low concentration region, and the measurement result of the NDIR analyzer 8 is used in the high concentration region.

Further, if the gas analyzer 3 is provided upstream of the NDIR analyzer 8, the cell 11 of the gas analyzer 3 may function like a buffer tank, resulting in a slow signal and a reduced sensitivity. Therefore, in the case where the sensitivity of the NDIR analyzer 8 is required, the following configuration may be adopted: the NDIR analyzer 8 is provided on the upstream side of the gas flow path 6, and the gas analyzer 3 is provided on the downstream side. With this configuration, analysis can be performed using the sensitivity of the NDIR analyzer 8.

The heating furnace 2 of each of the above embodiments is a high-frequency induction heating furnace system, but may be a resistance furnace system. The heating furnace 2 may be an infrared gold imaging furnace that heats a sample using an infrared lamp. In addition, a graphite crucible containing a fixed sample may be sandwiched between the lower electrode and the upper electrode, and an electric current may be applied to the graphite crucible to heat the fixed sample. The present invention can also be applied to a device having a gas generating section for generating gas by burning a fixed sample stored in a crucible.

The sample holder in each of the above embodiments is a container R such as a crucible for storing the sample W, but may be configured to hold the sample W without storing it. The sample holder holding the sample W is disposed in the heating furnace 2, thereby heating the sample W.

Further, various modifications and combinations of the embodiments can be made without departing from the spirit of the present invention.

Industrial applicability

According to the present invention, the frequency of maintenance can be reduced and the components to be measured can be analyzed reliably in the sample analyzer.