Concentration measuring device and concentration measuring method

Abstract

To provide a density measuring device and a density measuring method.SOLUTION: A density measuring device is to measure density of an object to be measured by using an infrared ray, and comprises: a signal acquisition unit that acquires a detection signal from an infrared ray detection unit that detects an influence of the infrared ray on the object to be measured; a temperature information acquisition unit that acquires information on temperature measured by a temperature measuring unit; a correction unit that outputs a correction signal obtained by correcting a temperature dependency of the detection signal on the basis of, the temperature information; and a calculation unit that calculates the density of the object to be measured according to the correction signal by using calibration curve data at a predetermined reference temperature to calculate the density of the object to be measured. The correction unit outputs the correction signal obtained by linearly correcting the detection signal by using, of predetermined correction parameters different among three or more temperature sections, a correction parameter in a temperature section corresponding to the temperature information.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a concentration measuring device and a concentration measuring method. [Background technology]

[0002] Patent Document 1 describes "providing a gas sensor that accurately compensates for the effects of light source degradation." [Prior art document] [Patent] Patent Document 1: Japanese Unexamined Patent Publication No. 2017-015516 Patent Document 2 Special Publication No. 2007-502407 [Overview of the Initiative]

[0003] In a first aspect of the present invention, a concentration measuring device for measuring the concentration of a target object using infrared radiation is provided, comprising: a signal acquisition unit that acquires a detection signal from an infrared detection unit that detects the effect of infrared radiation on the target object; a temperature information acquisition unit that acquires temperature information measured by a temperature measurement unit; a correction unit that outputs a correction signal that corrects the temperature dependence of the detection signal based on the temperature information; and a calculation unit that calculates the concentration of the target object according to the correction signal using calibration curve data at a predetermined reference temperature for calculating the concentration of the target object, wherein the correction unit outputs a correction signal that linearly corrects the detection signal using a correction parameter in the temperature interval corresponding to the temperature information from among predetermined correction parameters that differ for each of three or more temperature intervals.

[0004] In a second aspect of the present invention, a concentration measurement method is provided for measuring the concentration of a target object through which infrared radiation has passed, comprising the steps of: acquiring a detection signal from an infrared detection unit that detects the effect of infrared radiation on the target object; acquiring temperature information measured by a temperature measurement unit; and outputting a correction signal that corrects the temperature dependence of the detection signal, wherein the step of calculating the concentration of the target object according to the correction signal using calibration curve data at a predetermined reference temperature for calculating the concentration of the target object, the step of outputting the correction signal comprises the step of linearly correcting the detection signal using a correction parameter in the temperature interval corresponding to the temperature information from among three or more predetermined correction parameters that differ for each temperature interval.

[0005] It should be noted that the above summary of the invention does not enumerate all of its features. Furthermore, subcombinations of these features may also constitute an invention. [Brief explanation of the drawing]

[0006] [Figure 1] An example of the configuration of the concentration measuring device 100 is shown. [Figure 2A] An example of the temperature characteristics of the detected signal Sd is shown. [Figure 2B] An example of the temperature characteristics of the correction parameter Zero(T) is shown. [Figure 2C] This is an example of a graph showing the temperature dependence of the error in the signal obtained by converting the correction signal Sc to a concentration. [Figure 2D] An example of a method for calculating the concentration of 110 measurement targets using calibration curve data is shown. [Figure 3A] This section describes a method for correcting measurement errors using zero correction. [Figure 3B] This section describes a method for correcting measurement errors using span correction. [Figure 4A] A comparative example of the temperature characteristics of the detection signal when three correction temperature points are corrected using a quadratic polynomial is shown. [Figure 4B] This section shows a comparative example of the error in the correction signal when correcting three correction temperature points using a quadratic polynomial. [Figure 5A]Shows a comparative example of the temperature characteristics of a detection signal when correcting four or more correction temperature points with a polynomial of degree 3 or higher. [Figure 5B] Shows a comparative example of errors in a corrected signal when correcting four or more correction temperature points with a polynomial of degree 3 or higher. [Figure 6] Shows an example of an operation flowchart of the concentration measurement apparatus 100. [Figure 7A] This is an example of a graph showing the temperature dependence of an error of a signal obtained by converting a corrected signal Sc into a concentration, when linearly correcting three temperature intervals with four correction temperature points. [Figure 7B] This is an example of a graph showing the temperature dependence of an error of a signal obtained by converting a corrected signal Sc into a concentration, when linearly correcting four temperature intervals with five correction temperature points. [Figure 7C] Shows an example of an error of a signal obtained by converting a corrected signal Sc into a concentration, when linearly correcting six temperature intervals with seven correction temperature points. [Figure 8] Shows a comparative example when seven correction temperature points are corrected with a sixth-degree polynomial. [Figure 9] Shows an example of an embodiment when six temperature intervals are linearly corrected with seven correction temperature points.

Mode for Carrying Out the Invention

[0007] Hereinafter, the present invention will be described through embodiments of the invention, but the following embodiments do not limit the invention according to the claims. Furthermore, not all combinations of features described in the embodiments are necessarily essential to the solution means of the invention.

[0008] FIG. 1 shows an example of the configuration of the concentration measurement apparatus 100. The concentration measurement apparatus 100 includes a light emitting unit 10, an infrared influence detection unit 20, a temperature measurement unit 30, and a signal processing unit 40. The concentration measurement apparatus 100 of the present example includes an optical path unit 12 and a reflection unit 14. The concentration measurement apparatus 100 measures the concentration of a measurement object 110 using infrared rays.

[0009] The light emitting unit 10 emits infrared rays for measuring the concentration of the measurement object 110. The light emitting unit 10 may emit infrared rays having a constant light amount to allow the infrared rays to pass through the measurement object 110 and calculate the concentration of the measurement object 110. The light emitting unit 10 may be provided outside the concentration measuring apparatus 100.

[0010] The optical path unit 12 is an optical path for allowing infrared rays to pass through the measurement object 110. The optical path unit 12 includes the measurement object 110, and allows infrared rays to pass through the measurement object 110 with a predetermined optical path length. The optical path unit 12 may be a container for holding the measurement object 110 in a closed space, or may be a flow path for flowing the measurement object 110. Infrared rays reflected by the reflection unit 14 may pass through the optical path unit 12.

[0011] The measurement object 110 is a substance for measuring concentration by transmitting the infrared rays emitted from the light emitting unit 10. The measurement object 110 may be a gas or a liquid. For example, the measurement object 110 is carbon dioxide gas, but is not limited thereto. The measurement object 110 is provided in the optical path unit 12 through which infrared rays pass.

[0012] The infrared influence detection unit 20 detects the influence of the infrared rays emitted from the light emitting unit 10 on the measurement object 110, and outputs a detection signal Sd. The infrared influence detection unit 20 may include an infrared sensor for detecting infrared rays. The infrared influence detection unit 20 may include a quantum well sensor for detecting infrared rays. When the measurement object 110 is a gas, the infrared influence detection unit 20 may include a microphone for detecting a pressure change (sound wave) of the measurement object 110 caused by a change in kinetic energy when the measurement object 110 absorbs infrared rays. That is, the infrared influence detection unit 20 may include a microphone for detecting an acoustic wave generated by the photoacoustic effect of the measurement object 110.

[0013] The infrared influence detection unit 20 in this example has a first detection unit 21 and a second detection unit 22. The first detection unit 21 and the second detection unit 22 in this example each have an infrared sensor for detecting infrared light emitted by the light-emitting unit 10. The first detection unit 21 and the second detection unit 22 may each be quantum well type sensors. The first detection unit 21 and the second detection unit 22 are not limited to these, and the first detection unit 21 and / or the second detection unit 22 may have microphones. The detection mechanisms of the first detection unit 21 and the second detection unit 22 may be the same or different. The following describes the case where the first detection unit 21 and the second detection unit 22 are infrared sensors.

[0014] The first detection unit 21 outputs a first output signal So1, which detects infrared light that has passed through the object to be measured 110. That is, the amount of infrared light incident on the first detection unit 21 changes according to the density of the object to be measured 110, etc. For example, the amount of infrared light incident on the first detection unit 21 changes according to the Lambert-Beer law. In this example, the first detection unit 21 detects infrared light reflected by the reflector 14. That is, the first detection unit 21 detects infrared light that has passed through the object to be measured 110, been reflected by the reflector 14, and has passed through the object to be measured 110 again. However, the first detection unit 21 may also detect infrared light emitted by the light-emitting unit 10 without reflecting it back to the reflector 14.

[0015] The second detection unit 22 outputs a second output signal So2, which detects infrared radiation that has not passed through the object to be measured 110. That is, the second detection unit 22 detects a constant amount of infrared radiation, regardless of the concentration of the object to be measured 110. The second detection unit 22 may also detect the infrared radiation emitted by the light-emitting unit 10 without reflecting it off the reflecting unit 14. The resistance value of the first detection unit 21 may be used as the second output signal So2. The resistance value of the second detection unit 22 may be used as the second output signal So2. The forward voltage of the light-emitting unit 10 may be used as the second output signal So2. The second output signal So2 is not affected by the concentration of the object to be measured 110.

[0016] The detection signal Sd is a signal based on the first output signal So1 and the second output signal So2. The detection signal Sd may include each of the first output signal So1 and the second output signal So2. The detection signal Sd may also include the signal ratio of the first output signal So1 and the second output signal So2. By comparing the first output signal So1 and the second output signal So2 output by the infrared influence detection unit 20, the concentration change of the object to be measured 110 can be detected.

[0017] The infrared sensor of the infrared influence detection unit 20 may be a pyroelectric sensor or a quantum well sensor. At least one of the first detection unit 21 or the second detection unit 22 may be a quantum well sensor. By using a quantum well sensor, the infrared influence detection unit 20 can achieve a faster response compared to a pyroelectric sensor. In addition, since the quantum well sensor can measure the absolute value of the signal, simpler signal processing can be achieved.

[0018] Furthermore, the light-emitting unit 10 may emit infrared light from a common light-emitting element and then branch the optical path, causing the first detection unit 21 and the second detection unit 22 to detect infrared light from different optical paths, respectively. Alternatively, the light-emitting unit 10 may emit multiple infrared rays from different light-emitting elements, causing the first detection unit 21 and the second detection unit 22 to detect infrared light from different optical paths, respectively.

[0019] The temperature measuring unit 30 measures the temperature using any temperature sensor. In this example, the temperature measuring unit 30 measures the temperature at any location on the concentration measuring device 100. For example, the temperature measuring unit 30 measures the temperature of the light-emitting unit 10, the infrared influence detection unit 20, or the signal processing unit 40. The temperature measuring unit 30 may also measure the temperature of the object to be measured 110.

[0020] In one example, the temperature measuring unit 30 measures the temperature of the infrared influence detection unit 20 using the second detection unit 22. The temperature measuring unit 30 may measure the temperature of the second detection unit 22 based on the second output signal So2. Specifically, the temperature measuring unit 30 may measure the temperature of the second detection unit 22 based on the infrared signal value of the second detection unit 22. Specifically, the temperature measuring unit 30 may measure the temperature of the second detection unit 22 based on the resistance value of the second detection unit 22. By pre-measuring the temperature dependence of the second output signal So2, the second output signal So2 can be used as a thermometer. The temperature dependence of the second output signal So2 may be stored in the storage unit 45, which will be described later.

[0021] Here, temperature characteristics that affect concentration calculation may occur in the light-emitting unit 10 or the infrared influence detection unit 20. In addition, the absorbance characteristics of the measurement target 110 also change depending on the temperature, which may affect concentration calculation. Therefore, by correcting based on these temperatures, the concentration measuring device 100 can more easily calculate the concentration of the measurement target 110 with higher accuracy.

[0022] The signal processing unit 40 includes a signal acquisition unit 41, a temperature information acquisition unit 42, a correction unit 43, a calculation unit 44, and a storage unit 45. The signal processing unit 40 may be composed of a microcomputer.

[0023] The signal acquisition unit 41 acquires the detection signal Sd from the infrared influence detection unit 20. The signal acquisition unit 41 inputs the detection signal Sd to the correction unit 43. The signal acquisition unit 41 may acquire the detection signal Sd from the infrared influence detection unit 20 which is located outside the concentration measuring device 100. The signal acquisition unit 41 may acquire the first output signal So1 and the second output signal So2 as the detection signal Sd, or it may acquire the signal ratio of the first output signal So1 and the second output signal So2. The signal acquisition unit 41 may acquire the first output signal So1 and the second output signal So2 and generate the signal ratio of the first output signal So1 and the second output signal So2.

[0024] The temperature information acquisition unit 42 acquires temperature information It measured by the temperature measurement unit 30. The temperature information It may include the temperature of the object to be measured 110. The temperature information It may also include the temperature of the light-emitting unit 10, the infrared influence detection unit 20, or the signal processing unit 40. The temperature information acquisition unit 42 may also acquire temperature information It from the temperature measurement unit 30 located outside the concentration measuring device 100.

[0025] The correction unit 43 outputs a corrected signal Sc, which corrects the temperature dependence of the detection signal Sd. The correction unit 43 generates the corrected signal Sc based on the detection signal Sd and the temperature information It. In this example, the correction unit 43 linearly corrects the detection signal Sd for every three or more temperature intervals using predetermined correction parameters. The correction unit 43 may linearly correct the temperature dependence of the detection signal Sd using different correction parameters for each temperature interval. The correction parameters will be described later.

[0026] The calculation unit 44 calculates the concentration of the object to be measured 110 according to the correction signal Sc, using calibration curve data at a predetermined reference temperature for calculating the concentration of the object to be measured 110. For example, the calculation unit 44 calculates the concentration of the object to be measured 110 using common calibration curve data at a reference temperature (25°C) by correcting the detection signal Sd at an arbitrary measurement temperature Tm and applying it to the calibration curve data. Therefore, there is no need to change the calibration curve data according to the measurement temperature Tm. Calibration curve data will be described later. The calculation unit 44 may also output the calculated concentration of the object to be measured 110 to the outside of the concentration measuring device 100.

[0027] The memory unit 45 stores information necessary for calculating the concentration of the object to be measured 110. In this example, the memory unit 45 stores information such as correction parameters used in the correction unit 43 to correct the detection signal Sd. The memory unit 45 may also store calibration curve data for calculating the concentration of the object to be measured 110 in the calculation unit 44.

[0028] In this example, the memory unit 45 stores different correction parameters for three or more temperature intervals. The memory unit 45 may store the temperature intervals and correction parameters in a table format. The memory unit 45 may store the function parameters used for linear correction for each temperature interval T1 to Tn.

[0029] The concentration measuring device 100 is housed in a single housing 50. That is, the concentration measuring device 100 is packaged as a single unit by the housing 50. In this example, the concentration measuring device 100 includes the signal processing unit 40, as well as the light-emitting unit 10, optical path unit 12, reflecting unit 14, infrared influence detection unit 20, and temperature measuring unit 30, all packaged as a single unit. However, any of these components may be provided outside the housing 50. That is, the concentration measuring device 100 may acquire the detection signal Sd and temperature information It measured outside the housing 50 and calculate the concentration of the object to be measured 110.

[0030] Here, the absorption of infrared radiation by the measurement target 110 will be explained using the Lambert-Beer law. In this example, a gas is used as the measurement target 110, but it is not limited to this. The amount of infrared radiation absorbed by the gas, Abs, is given by the following equation. Abs = I0 - I0 × e -k×l×c I0 represents the ideal absorbance unaffected by gas. k is the gas-dependent absorption coefficient, l is the optical path length, and c is the gas concentration. The absorbance AR is given by the following equation. AR = 1 - e -k×l×c When temperature coefficients are applied to the correction parameters for zero correction and span correction, each correction parameter is expressed by the following equation. Zero correction and span correction will be discussed later. Correction parameter Zero(T) = Zero × fz(T) Correction parameter Span(T) = Span × fs(T)

[0031] In this case, the absorbance signal Signal_Abs is given by the following equation. Signal_Abs=Span(T)×(1-Zero(T)×So1 / So2)

[0032] The amount of light that reaches the object is given by the following equation. I0 - Abs = I0 - (I0 - I0 × e -k×l×c ) The incoming light intensity signal, Signal, is given by the following equation. Signal=1-(1-(So1 / So2)×Zero(T))×Span(T)

[0033] In this way, the concentration measuring device 100 can calculate the concentration of the object to be measured 110 by acquiring a signal corresponding to the concentration of the object to be measured 110.

[0034] Figure 2A shows an example of the temperature characteristics of the detected signal Sd. The vertical axis represents the signal intensity of the detected signal Sd, and the horizontal axis represents the temperature. In this example, linear correction is applied to six temperature intervals T1 to T6, spaced 5°C apart, from 10°C to 40°C. The correction temperature points in this example are 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, and 40°C. The correction temperature points are the reference points for linear correction, where the error between the detected signal Sd and the correction parameter is minimized. As an example, the correction signal Sc may be a signal with a nearly flat temperature characteristic obtained by dividing the detected signal Sd by the correction parameter. Here, a nearly flat temperature characteristic means that the signal hardly fluctuates with changes in temperature.

[0035] Figure 2B shows an example of the temperature characteristics of the correction parameter Zero(T). The vertical axis represents signal intensity, and the horizontal axis represents temperature. The correction parameter Zero(T) may be a function obtained such that the correction signal Sc is approximately flat. That is, it may be a function that is the reciprocal of the detection signal Sd. In this example, linear correction is performed on six temperature intervals T1 to T6, at 5°C intervals from 10°C to 40°C. The correction temperature points in this example are 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, and 40°C. The correction temperature points are the reference points for linear correction, and are the points where the temperature characteristics of the correction signal Sc are processed to be approximately flat. That is, at the correction temperature points, the value obtained by multiplying the detection signal Sd by the correction parameter Zero(T) may be 1. The correction parameter Zero(T) may be obtained by linear interpolation of a function that is the reciprocal of the temperature characteristics of the detection signal Sd. Here, linear interpolation is the process of obtaining a parameter by fitting the function between the correction points. Linear correction involves using correction parameters to make the temperature characteristics of the corrected signal approximately flat. Therefore, linear correction and linear interpolation may be different concepts.

[0036] As described above, the correction signal Sc may be a signal that is made approximately flat by multiplying or dividing the detection signal Sd by the correction parameter Zero(T). In the example in Figure 2A, the correction signal Sc is made approximately flat by dividing the detection signal Sd by the correction parameter Zero(T), and in the example in Figure 2B, the correction signal Sc is made approximately flat by multiplying the detection signal Sd by the correction parameter Zero(T). In other words, linear correction may be a correction of the detection signal Sd using a correction parameter that is a linear function of temperature.

[0037] The correction signal Sc may be the absorbance signal Signal_Abs or the received light intensity signal Signal. The correction signal Sc should be a signal that changes according to the concentration of the object being measured 110. In this example, the correction signal Sc is the absorbance signal Signal_Abs.

[0038] In the concentration measuring apparatus 100 of the present example, a correction parameter Zero(T) is set for each temperature interval. The correction parameter of the present example is used for zero correction, but temperature characteristics may also be corrected using other correction parameters such as those for span correction.

[0039] The correction parameter Zero(T) of the present example is represented by the following formula. Zero(T)=ZeroN×(1+a zeroN T) The coefficient ZeroN and coefficient a zeroN may have different values for each temperature interval. The coefficient a zeroN of the present example is set as a zero1 to a zero6 respectively in the temperature intervals T1 to T6. That is, the correction parameter Zero(T) may have different values for each temperature interval.

[0040] As a modified example, when correcting temperature characteristics using the correction parameter Span(T) for span correction, the correction parameter Span(T) is represented by the following formula. Span(T)=SpanN×(1+a spanN T) The coefficient SpanN and coefficient a spanN may have different values for each temperature interval. That is, the correction parameter Span(T) may have different values for each temperature interval.

[0041] The concentration measuring apparatus 100 of the present example performs linear correction for each of three or more temperature intervals using different correction parameters for each temperature interval. In other words, the correction parameters may be different for each temperature interval. Thereby, the concentration measuring apparatus 100 can accurately approximate the temperature characteristic curve even for three or more temperature intervals. Further, by performing linear correction for each of three or more temperature intervals, overfitting caused by approximation is less likely to occur compared to the case of using a polynomial. Additionally, linear correction reduces the number of multiplications compared to using a polynomial, which can lower the calculation cost.

[0042] Figure 2C is an example graph showing the temperature dependence of the error in the signal obtained by converting the correction signal Sc to concentration. The error on the vertical axis represents the error in the signal obtained by converting the correction signal Sc to concentration with respect to the concentration of the measurement target 110. Multiple plots for each temperature show the simulation results for samples with different temperature characteristics. The concentration measuring device 100 in this example reduces wave-like errors at temperatures other than the correction temperature points described later by linearly correcting the detection signal Sd for every three or more temperature intervals. In this example, the error is kept within ±0.4 in the range from 10°C to 40°C. In this way, the concentration measuring device 100 can correct the detection signal Sd with higher accuracy while suppressing computation costs.

[0043] Figure 2D shows an example of a method for calculating the concentration of the substance to be measured 110 using calibration curve data. In this example, the calibration curve data is data at a predetermined reference temperature (for example, 25°C). The concentration measuring device 100 can calculate the concentration of the substance to be measured 110 using common calibration curve data by generating a correction signal Sc(Tm) at the measurement temperature Tm. That is, even if the reference temperature and the measurement temperature Tm are different, the concentration of the substance to be measured 110 can be calculated using calibration curve data at the reference temperature by correcting the measurement signal Sd and obtaining the correction signal Sc. Only one calibration curve data set at a predetermined reference temperature needs to be obtained.

[0044] Figure 3A shows a method for correcting measurement errors by zero correction. The solid line is a reference signal line showing the concentration dependence of the measured signal. The dashed line is a measured signal line showing the concentration dependence of the measured signal. For example, at a concentration of 0 ppm, the measured signal line is moved and corrected so that the measured signal intensity matches the reference signal intensity. Furthermore, correction of its temperature characteristics may also be included. In this example, the measured signal line with a signal intensity ratio S = So1 / So2 is corrected, but the type of signal to be corrected is not limited to this.

[0045] In this example, the measured signal line is aligned with the reference signal line using a signal intensity of 0 ppm for the measurement target 110. However, correction may be made using a concentration other than 0 ppm as the reference. For example, if the measurement target 110 is carbon dioxide gas, correction may be made using a signal intensity of 400 ppm.

[0046] Figure 3B shows a method for correcting measurement errors by span correction. Span correction involves adjusting the slope of the measured signal line, shown by the dashed line, so that the difference from the reference signal line in the measured concentration range falls within a predetermined range. Furthermore, it may also include correction of the temperature characteristics. In this example, the intensity change of the measured signal line from a predetermined gas concentration (e.g., 0 ppm) to the measured concentration range is corrected to fall within a predetermined reference output range. The reference output range may be the output range of the reference signal line, may be determined based on calibration curve data at a predetermined reference temperature, and may be included within the variation range of the calibration curve data.

[0047] The concentration measuring device 100 may correct its temperature characteristics using either zero correction or span correction, or it may correct its temperature characteristics using both. The concentration measuring device 100 may set the correction parameters for the method used for three or more temperature intervals.

[0048] Furthermore, the concentration measuring device 100 may perform temperature characteristic correction in addition to zero correction and / or span correction. For example, if the detection signal Sd is the signal ratio of the first output signal So1 and the second output signal So2, temperature characteristic correction may be performed on the first output signal So1 and / or the second output signal So2 before performing zero correction and / or span correction on the detection signal Sd. The temperature characteristic correction of the first output signal So1 and / or the second output signal So2 may be performed using correction parameters set for three or more temperature intervals, and may be the same type of correction as the correction of the detection signal Sd described above. By adding further temperature characteristic correction, the temperature characteristics can be further improved.

[0049] Figure 4A shows a comparative example of the temperature characteristics of the detection signal when three correction temperature points are corrected with a quadratic polynomial. In this example, correction is performed using a quadratic polynomial with correction temperature points of 10°C, 25°C, and 40°C. The correction parameter Zero(T) used in each temperature interval is given by the following equation. Correction parameter Zero(T) = Zero × fz(T) =Zero × (1 + a zero1 T+a zero2 T 2 ) Zero, a zero1 and a zero2 This can be any correction factor.

[0050] Figure 4B shows a comparative example of the error in the correction signal when three correction temperature points are corrected using a quadratic polynomial. The error on the vertical axis represents the error in the correction signal with respect to the concentration of the measured substance 110. The correction conditions and correction temperature points are the same as in the example in Figure 4A. When correcting with a quadratic polynomial, wave-like errors may occur at temperatures other than the correction temperature points, as in this example. In this example, the error is within ±0.5 in the range from 10°C to 40°C.

[0051] Figure 5A shows a comparative example of the temperature characteristics of the detection signal when four or more correction temperature points are corrected with a polynomial of degree three or higher. In this example, five correction temperature points at 10°C, 20°C, 25°C, 30°C, and 40°C are used for correction with a fourth-degree polynomial. The correction parameter Zero(T) used in each temperature interval is given by the following equation. Correction parameter Zero(T) = Zero × fz(T) =Zero × (1 + a zero1 T+a zero2 T 2 +a zero3 T 3 ...)

[0052] Figure 5B shows a comparative example of the error in the corrected signal when correcting four or more correction temperature points with a polynomial of degree three or higher. The correction conditions and correction temperature points are the same as in the example in Figure 5A. Even when increasing the number of correction temperature points and correcting with a polynomial of degree three or higher, wave errors may occur at temperatures other than the correction temperature points, as in this example. Furthermore, using a polynomial of degree three or higher makes wave errors at temperatures other than the correction temperature points more likely to occur than when using a quadratic polynomial. In this example, the error is ±0.5 or more in the range from 10°C to 40°C, which is an increase in error compared to when using a quadratic polynomial.

[0053] Figure 6 shows an example of the operation flowchart of the concentration measuring device 100. In step S100, correction parameters corresponding to the correction temperature interval are stored. In step S102, infrared light is emitted. The infrared light may pass through the object to be measured 110 and be detected by the first detection unit 21, or it may not pass through the object to be measured 110 and be detected by the second detection unit 22. In step S104, the detection signal Sd and temperature information It are acquired. In step S106, the correction parameters corresponding to the temperature information It are read out. In step S108, a correction signal Sc is generated by correcting the detection signal Sd based on the read-out correction parameters. In step S110, the concentration of the object to be measured 110 according to the correction signal Sc is calculated using calibration curve data at a predetermined reference temperature. The concentration measuring device 100 may output the calculated concentration of the object to be measured 110 to the outside.

[0054] In this example, the concentration measuring device 100 linearly corrects the detection signal Sd for every three or more temperature intervals using predetermined correction parameters in step S108. That is, the linear correction is performed in step S110 before calculating the concentration of the object to be measured 110 using calibration curve data. Therefore, the concentration measuring device 100 does not need to correct for the temperature dependence of the calibration curve data. In other words, the concentration measuring device 100 in this example only needs to prepare one calibration curve data at a predetermined reference temperature, and does not need to prepare different calibration curve data for each temperature.

[0055] Figure 7A is an example graph showing the temperature dependence of the error of the concentration-converted signal Sc when linear correction is performed on three temperature intervals using four correction temperature points. In this example, linear correction is performed on three temperature intervals T1 to T3 between 10°C, 20°C, 30°C, and 40°C using four correction temperature points. When the concentration measuring device 100 performs linear correction, even if there are many correction temperature points and three temperature intervals, there is no increase in wave-like errors at temperatures other than the correction temperature points, as can occur when using polynomials.

[0056] Figure 7B is an example graph showing the temperature dependence of the error of the signal obtained by concentration conversion of the correction signal Sc when linear correction is performed on four temperature intervals using five correction temperature points. In this example, linear correction is performed on four temperature intervals T1 to T4 between the temperatures of 10°C, 20°C, 25°C, 30°C, and 40°C using five correction temperature points. Thus, the widths of the three or more temperature intervals that the concentration measuring device 100 linearly corrects do not have to be equal. When the concentration measuring device 100 performs linear correction, even if there are many correction temperature points and the number of temperature intervals is three or more (four in this example), there is no increase in wave-like errors at temperatures other than the correction temperature points, as can occur when using polynomials. Conversely, the concentration measuring device 100 in this example can reduce wave-like errors at temperatures other than the correction temperature points by adding new correction temperature points to intervals where wave-like errors occurred at temperatures other than the correction temperature points in the comparative example.

[0057] Figure 7C shows an example of the error in the signal obtained by concentration conversion of the correction signal Sc when linear correction is performed on six temperature intervals with seven correction temperature points. In this example, linear correction is performed on six temperature intervals T1 to T6, at 5°C intervals from 10°C to 40°C. Similar to the embodiments in Figures 7A and 7B, when the concentration measuring device 100 performs linear correction, even when the number of temperature intervals is three or more (six in this example), there is no increase in wave-like errors at temperatures other than the correction temperature points, as can be seen when using polynomials. In the comparative example, it is conceivable to use higher-order polynomials for correction as the number of correction temperature points increases, but in this example, even when there are many correction temperature points and many temperature intervals, wave-like errors at temperatures other than the correction temperature points can be suppressed by linear correction. For example, in this example, the error can be reduced by about 30% compared to the comparative example shown in Figures 4B and 5B.

[0058] Figure 8 shows a comparative example where seven correction temperature points are corrected using a sixth-degree polynomial. The correction temperature range in this example is 10°C to 40°C. In this example, the simulation results are shown, with the signal value obtained at 25°C as the reference, and the change calculated from 25°C. Because the correction is done using a sixth-degree polynomial, the signal value changes rapidly outside the correction temperature range, indicating degradation due to overfitting. Overfitting can also reduce the reliability of temperature characteristic correction within the correction temperature range.

[0059] Figure 9 shows an example where six temperature intervals are linearly corrected using seven correction temperature points. In this example, the simulation results are shown, with the signal value obtained at 25°C as the reference, and the change from 25°C calculated. When linearly corrected, the behavior differs significantly from the case using the sixth-degree polynomial in Figure 8, and this example is clearly more stable outside the correction temperature range.

[0060] Thus, the concentration measuring device 100 improves temperature characteristics even when the number of temperature intervals increases by linearly correcting the detection signal Sd for each of the three or more temperature intervals. Furthermore, since the concentration measuring device 100 linearly corrects the detection signal Sd for each temperature interval, it can reduce the number of multiplications compared to using polynomials, thereby reducing computational costs.

[0061] The concentration measuring device 100 calculates a corrected signal Sc that corrects for temperature dependence by linearly correcting the intensity and intensity change of the detection signal Sd for each of three or more temperature intervals based on the temperature information It, so that the intensity and intensity change of the detection signal Sd fall within a predetermined reference output range within the concentration measurement range. It then outputs the concentration of the object to be measured 110 using calibration curve data at a predetermined reference temperature. In other words, the concentration measuring device 100 linearly corrects the temperature characteristics of the intensity and intensity change of the detection signal Sd for each of three or more temperature intervals based on the temperature information It, using a zero correction parameter Zero(T) and / or a span correction parameter Span(T) expressed in linear form of temperature. Then, it calculates the concentration of the object to be measured 110 from the corrected signal Sc using calibration curve data at a predetermined reference temperature. With this configuration, it is easier to improve the temperature characteristics even when the number of temperature intervals increases, and the computation cost can be reduced by reducing multiplication compared to when polynomials are used.

[0062] The above describes the case where the infrared effect detection unit 20 has an infrared sensor, but the infrared effect detection unit 20 may also have a microphone. When the infrared effect detection unit 20 has a microphone, the detection signal Sd may be an acoustic wave signal due to the photoacoustic effect of the object being measured 110. Even when the detection signal Sd is one of these signals, the above-described method for correcting temperature characteristics is still effective. That is, the temperature characteristics of these signals can be corrected using correction parameters set for each of three or more temperature intervals, making it easier to improve temperature characteristics even when the number of temperature intervals increases, and reducing computational costs by reducing multiplication compared to the case where polynomials are used.

[0063] Although the present invention has been described above using embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments. It will be apparent to those skilled in the art that various modifications or improvements can be made to the above embodiments. It will be clear from the claims that such modified or improved forms may also be included in the technical scope of the present invention.

[0064] It should be noted that the execution order of operations, procedures, steps, and stages in the apparatus, systems, programs, and methods shown in the claims, specifications, and drawings is not explicitly stated as "before," "prior to," etc., and that these can be implemented in any order unless the output of a previous process is used in a later process. Even if the operation flow in the claims, specifications, and drawings is described using phrases such as "first," "next," etc. for convenience, it does not mean that it is essential to perform the operations in that order. [Explanation of Symbols]

[0065] 10...Emitting unit, 12...Optical path unit, 14...Reflecting unit, 20...Infrared influence detection unit, 21...First detection unit, 22...Second detection unit, 30...Temperature measurement unit, 40...Signal processing unit, 41...Signal acquisition unit, 42...Temperature information acquisition unit, 43...Correction unit, 44...Calculation unit, 45...Storage unit, 50...Housing, 100...Concentration measuring device, 110...Measurement target

Claims

1. A concentration measuring device that measures the concentration of a target object using infrared light, A signal acquisition unit that acquires a detection signal from an infrared effect detection unit that detects the effect of infrared radiation on the object to be measured, A temperature information acquisition unit that acquires temperature information measured by the temperature measurement unit, A correction unit outputs a correction signal that corrects the temperature dependence of the detection signal based on the temperature information, A calculation unit that calculates the concentration of the target to be measured according to the correction signal using calibration curve data at a predetermined reference temperature for calculating the concentration of the target to be measured. Equipped with, The correction unit outputs a correction signal obtained by linearly correcting the detection signal using the correction parameter in the temperature interval corresponding to the temperature information, from among three or more predetermined correction parameters that differ for each temperature interval. Concentration measuring device.

2. The correction unit linearly corrects the temperature dependence of the detection signal using different correction parameters for each temperature interval. The concentration measuring device according to claim 1.

3. The correction unit linearly corrects the detection signal so that the intensity and intensity change of the detection signal fall within a predetermined reference output range within the measurement concentration range. The concentration measuring device according to claim 1.

4. The aforementioned reference output range is determined based on the calibration curve data. The concentration measuring device according to claim 3.

5. A first detection unit outputs a first output signal that detects infrared radiation passing through the object to be measured, A second detection unit outputs a second output signal that detects infrared radiation that has not passed through the measurement target. The infrared influence detection unit having the above-mentioned, The detection signal is a signal based on the first output signal and the second output signal. The concentration measuring device according to claim 1.

6. The correction unit linearly corrects the first output signal and / or the second output signal for each of the three or more temperature intervals. The concentration measuring device according to claim 5.

7. The temperature measuring unit measures the temperature of the infrared influence detection unit using the second detection unit. The concentration measuring device according to claim 5.

8. The temperature measuring unit measures the temperature of the second detection unit based on the second output signal. The concentration measuring device according to claim 7.

9. The temperature measuring unit measures the temperature of the second detection unit based on the resistance value of the second detection unit. The concentration measuring device according to claim 7.

10. The infrared influence detection unit has a quantum well type sensor for detecting the infrared radiation. A concentration measuring device according to any one of claims 1 to 9.

11. The infrared influence detection unit has a microphone for detecting the influence of infrared rays. A concentration measuring device according to any one of claims 1 to 9.

12. The system includes a storage unit that stores different correction parameters for each of the three or more temperature intervals. A concentration measuring device according to any one of claims 1 to 9.

13. The storage unit stores the three or more temperature intervals and the correction parameters in a table format. The concentration measuring device according to claim 12.

14. The signal processing unit comprises the signal acquisition unit, the temperature information acquisition unit, the correction unit, and the calculation unit, The signal processing unit is composed of a microcomputer. A concentration measuring device according to any one of claims 1 to 9.

15. The light-emitting unit for emitting infrared light, The object to be measured has an optical path section for allowing the infrared light to pass through and Equipped with, The concentration measuring device is housed in a single enclosure. A concentration measuring device according to any one of claims 1 to 9.

16. A concentration measurement method for measuring the concentration of a target object through which infrared light has passed, A step of acquiring a detection signal from an infrared influence detection unit that detects the influence of infrared rays on the object to be measured, The step of acquiring temperature information measured by the temperature measurement unit, In the step of outputting a corrected signal obtained by correcting the temperature dependence of the detection signal, A step of calculating the concentration of the target to be measured according to the correction signal using calibration curve data at a predetermined reference temperature for calculating the concentration of the target to be measured. Equipped with, The step of outputting the correction signal includes a step of linearly correcting the detection signal using the correction parameter in the temperature interval corresponding to the temperature information, from among three or more predetermined correction parameters that differ for each temperature interval. Concentration measurement method.

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