Odor detection device and control method thereof

Abstract

To provide a smell detector that can ensure sufficient sensitivity and identification accuracy of a photoacoustic sensor even in the presence of environmental noise, and a method for controlling the same.SOLUTION: A smell detector comprises: band setting means that operates in a state where measurement target gas is not irradiated with light from a light source, compares a reference acoustic spectrum of the gas measured in advance with a noise acoustic spectrum obtained by a frequency analysis unit analyzing environmental noise, and sets a predetermined measurement frequency band where both acoustic spectra overlap each other; and drive frequency setting means that, when acoustic intensity of the noise acoustic spectrum in the measurement frequency band is larger than a predetermined intensity threshold, sets a predetermined frequency of another measurement frequency band different from the measurement frequency band, as a frequency of a drive signal provided to light source driving means.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an odor detection device that detects components of gas that cause odors, and more particularly to an odor detection device that detects odors using a photoacoustic sensor, and a control method for the same. [Background technology]

[0002] At manufacturing sites for fermented products such as miso and soy sauce, as well as at cosmetics manufacturing sites and food storage warehouses, smell (also known as aroma) is a quality control item, but it is difficult to implement digital transformation (DX).As a result, smell identification relies on the experience and senses of on-site workers, resulting in increased management and training costs.

[0003] Recently, attempts have been made to improve the efficiency of quality control through digitalization by quantifying odors (gas type, concentration, etc.) using odor sensors. Quantifying odors requires gas sensors that detect gas components and odor components according to the purpose. Photoacoustic sensors that use the photoacoustic effect, such as those described in JP 2022-26652 A (Patent Document 1), have been proposed as sensors for detecting gas components and odor components.

[0004] The photoacoustic effect is a phenomenon in which, when light of a specific wavelength (such as laser light) is intermittently (pulsed) irradiated onto molecules of a specific component that make up a gas, the molecules that absorb the light undergo thermal expansion and contraction, generating acoustic waves. Photoacoustic sensors are small and can detect gas components with high sensitivity, so they are being applied to a variety of manufacturing sites. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2022-26652 Summary of the Invention [Problem to be solved by the invention]

[0006] Photoacoustic sensors work by using a microphone to detect acoustic waves generated by the thermal expansion and contraction of molecules that absorb light. Therefore, the microphone may detect environmental sounds (background noise) generated in the surrounding environment, the operating sounds of machinery at manufacturing sites, and the like (collectively referred to as "environmental noise" hereafter). When the measurement acoustic spectrum band of a photoacoustic sensor overlaps with the noise acoustic spectrum band of environmental noise, the sensitivity and discrimination accuracy of the photoacoustic sensor decrease. Therefore, there is a need to solve this phenomenon of decreased sensitivity and discrimination accuracy of photoacoustic sensors.

[0007] An object of the present invention is to provide an odor detection device that can ensure sufficient sensitivity and discrimination accuracy of a photoacoustic sensor even in the presence of environmental noise, and a control method for the same. [Means for solving the problem]

[0008] The present invention is characterized by comprising: light source driving means for causing the light source to emit light intermittently with a drive signal of a predetermined measurement frequency; a microphone for detecting acoustic waves of a specific gas in a sensor cell; signal processing means for signal processing of the acoustic waves detected by the microphone; and control means for executing at least a light source driving function for providing a drive signal to the light source driving means and a gas estimation function for estimating the type of specific gas based on a signal from the signal processing means, wherein the control means comprises: band setting means that operates in a state where no light is irradiated from the light source, and compares a reference acoustic spectrum of the gas to be measured that has been measured in advance with a noise acoustic spectrum obtained by analyzing environmental noise in a frequency analysis unit, and sets a predetermined measurement frequency band in which both acoustic spectra overlap; and drive frequency setting means that, when the acoustic intensity of the noise acoustic spectrum in the measurement frequency band is greater than a predetermined intensity threshold, sets a measurement frequency band different from the measurement frequency band, and sets the predetermined frequency of this newly set different measurement frequency band as the frequency of the drive signal for the light source driving means. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide an odor detection device that can ensure sufficient sensitivity and discrimination accuracy of a photoacoustic sensor even in the presence of environmental noise, and a control method thereof. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a system configuration diagram showing the configuration of an odor detection device according to an embodiment of the present invention. [Figure 2] FIG. 10 is a flowchart illustrating a control flow before measurement of the odor detection device. [Figure 3] FIG. 2 is an explanatory diagram illustrating the relationship between a measurement frequency band and a noise frequency band. [Figure 4] FIG. 10 is a flowchart illustrating a first control flow during measurement by the odor detection device. [Figure 5] FIG. 5 is an explanatory diagram for reinforcing the explanation of the control flow shown in FIG. [Figure 6] FIG. 10 is a flowchart illustrating a second control flow during measurement by the odor detection device. [Figure 7] FIG. 7 is an explanatory diagram for reinforcing the explanation of the control flow shown in FIG. 6. [Figure 8] FIG. 10 is a flowchart illustrating another control flow before measurement of the odor detection device. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The embodiment is an example for explaining the present invention, and for the sake of clarity, some details have been omitted and simplified as appropriate. The present invention can also be implemented in various other forms. [Example]

[0012] First, an embodiment of the present invention will be described with reference to FIG. 1. The control means of the present invention is premised on operating in a state where no light is emitted from the light source driven by the light source driving means.

[0013] In the basic configuration of this embodiment, the control means comprises: a band setting means that compares a reference acoustic spectrum of the gas to be measured, which has been measured in advance, with a noise acoustic spectrum obtained by analyzing environmental noise in the frequency analysis unit, and sets a predetermined measurement frequency band in which the two acoustic spectra overlap; and a drive frequency setting means that, when the acoustic intensity of the noise acoustic spectrum in the measurement frequency band is greater than a predetermined intensity threshold, sets another measurement frequency band different from the measurement frequency band, and sets the predetermined frequency of this newly set another measurement frequency band as the frequency of the drive signal for the light source drive means.

[0014] With this configuration, the light source is driven while avoiding the noise acoustic spectrum band with high noise intensity, thereby ensuring sufficient sensitivity and discrimination accuracy of the photoacoustic sensor. Next, a specific configuration of this embodiment will be described with reference to FIG. 1, an odor detection device 10 includes a master clock generation unit 11, and the clock signal of this master clock generation unit 11 is supplied to a lock-in clock generation unit 12. The lock-in clock generation unit 12 generates pulsed laser light from a light source 15 of the photoacoustic sensor, and generates a clock signal that matches the gas component to be detected in the measurement target gas, that is, that thermally excites the measurement gas component.

[0015] The clock signal generated by lock-in clock generation unit 12 is input to pulse generation unit 13, which generates a pulse signal. This pulse signal is input to light source drive unit 14 and converted into an electrical signal that drives light source 15. Light source 15 is driven by light source drive unit 14 to generate intermittent pulsed light.

[0016] Here, the light source 15 is a laser emitter, which emits light in synchronization with the pulse signal generated by the pulse generating unit 13. Note that, in addition to the laser emitter, an LED illuminator can also be used.

[0017] Laser pulse light from light source 15 is irradiated into resonance cell 16, which constitutes the odor sensor, and thermally excites the gas components of the measurement target gas. Acoustic waves generated by the thermal expansion and contraction of these gas components are measured by microphone 17. The measured acoustic waves are detected as analog electrical signals by acoustic detection unit 18 and further converted into digital signals by AD converter 19.

[0018] The signal from AD converter 19 is input to lock-in detection unit 20, which outputs an intensity output and a phase output. A lock-in clock signal output from lock-in clock generation unit 12 is input to lock-in detection unit 20 and split into two input signals. That is, an in-phase lock-in clock signal is input to multiplication unit 21, and a lock-in clock signal with a phase difference of 90° is input to multiplication unit 23 by 90° phase shift unit 22.

[0019] The measurement signal from AD converter 19 is input to multiplier 21 and multiplied by the lock-in clock signal to produce a signal having high-frequency and low-frequency components. The signal from multiplier 21 is input to low-pass filter 24, which attenuates the high-frequency components while transmitting and averaging the low-frequency components. The signal from low-pass filter 24 is input to intensity calculator 25 and becomes the intensity output of the acoustic wave.

[0020] Similarly, the signal from AD converter 19 is input to multiplier 23 and multiplied by a lock-in clock signal with a phase difference of 90° to produce a signal having high-frequency and low-frequency components. The signal from multiplier 23 is input to low-pass filter 26, which attenuates the high-frequency components while transmitting and averaging the low-frequency components. The signal from low-pass filter 26 is input to phase calculator 27 and becomes the phase output of the acoustic wave.

[0021] These lock-in detection units 20 are well known and will not be described further, but the lock-in detection unit 20 can be configured by an analog circuit, a digital circuit, computer software, or the like.

[0022] The intensity output and phase output of lock-in detection unit 20 are input to odor concentration calculation unit 28, which determines the odor concentration. The determined odor concentration is input to measurement control unit 29 and sent to I / O unit (input / output unit) 30, and further input to external memory 32 via communication line 31 for storage.

[0023] Furthermore, measurement control unit 29 can compare the input odor concentration with a predetermined concentration threshold, and issue an alarm or other notification if the input odor concentration exceeds the concentration threshold. Furthermore, external memory 32 can store the odor concentration measured by resonance cell 16 on a time scale, allowing changes in odor concentration over time to be tracked.

[0024] The odor detection device having the above-described configuration is well known as described in Patent Document 1.

[0025] Next, a description will be given of the configuration of the first embodiment. As described above, the premise of this embodiment is that environmental noise is acquired from the microphone 17 of the resonance cell 16 in a state where the light source 15 is not irradiating the laser pulse light.

[0026] The output of the AD converter 19, which is the environmental noise, is input to a noise frequency analysis unit 33 for frequency analysis. The frequency analysis converts the environmental noise into an acoustic spectrum for each frequency (hereinafter referred to as a noise acoustic spectrum) using a fast Fourier transform. This noise acoustic spectrum is then input to a comparison unit 34.

[0027] In addition to the noise spectrum, a reference acoustic spectrum is input to the comparison unit 34. The reference acoustic spectrum is stored in the external memory 32, and is obtained by measuring or simulating the acoustic spectrum of the gas components of the measurement target gas in advance and storing it in the external memory 32 as the reference acoustic spectrum.

[0028] This reference acoustic spectrum is loaded into the I / O unit 30 via the communication line 31 by the operation of the measurement control unit 29, and is then loaded into the acoustic spectrum storage unit 35. SRAM can be used for the acoustic spectrum storage unit 35. By using SRAM, there is no need to frequently read the reference acoustic spectrum from the external memory 32, and computer resources can be used efficiently.

[0029] The comparison unit 34 executes an operation of comparing the noise sound spectrum from the noise frequency analysis unit 33 with the reference sound spectrum from the sound spectrum storage unit 35. This comparison operation sets a predetermined measurement frequency band where the noise sound spectrum and the reference sound spectrum overlap, and determines whether the sound intensity of the noise sound spectrum in this measurement frequency band is greater than a predetermined intensity threshold.

[0030] In other words, if the noise acoustic spectrum is large, the odor intensity may be calculated from this noise acoustic spectrum, resulting in an erroneous measurement result. To avoid this phenomenon, if the acoustic intensity of the noise acoustic spectrum is deemed to be greater than a predetermined intensity threshold, a new frequency of the lock-in clock is set by the frequency setting unit 36 ​​(described later).

[0031] The frequency setting unit 36 ​​sets a new measurement frequency band different from the measurement frequency band, and sets a predetermined frequency within this new measurement frequency band as a lock-in clock and the drive frequency of the drive signal for the light source drive means 14. Of course, it goes without saying that this new measurement frequency band is also compared with the intensity threshold value.

[0032] The predetermined drive frequency can be the center frequency of the new measurement frequency band. The set drive frequency is input to the measurement control unit 29, which then sets the drive frequency of the lock-in clock in the lock-in clock generation unit 12. Therefore, when measuring the gas components of the measurement target gas, the light source 16 is driven at this drive frequency.

[0033] In this way, the acoustic waves generated by the resonance cell 16 are not measured in the frequency band where the acoustic intensity of the noise acoustic spectrum is high, but are measured in the frequency band where the intensity of the noise acoustic spectrum is low. Therefore, sufficient sensitivity and identification accuracy of the photoacoustic sensor can be ensured even in the presence of environmental noise.

[0034] The phase output from the phase calculation unit 27 is input to a fluctuation amount detection unit 37, and the detected fluctuation of the phase output is input to the measurement control unit 29. Here, since the phase output has a correlation with the intensity output, the intensity output of the intensity calculation unit 25 can also be input to the fluctuation amount detection unit 37. The fluctuation calculation unit 37 will be described in the second embodiment.

[0035] The odor detection device according to the present embodiment can be implemented using a computer, and may include, for example, a central processing unit (CPU). Furthermore, the odor detection device may also include, or consist of, a graphics processing unit (GPU), a field-programmable gate array (FPGA), an application-specific integrated circuit (ASIC), etc., in addition to the CPU.

[0036] 1 shows the odor detection device 10 in functional blocks, but in reality, it can be implemented using a computer. In this case, the above-described operations can be performed by executing a control program stored in the computer's ROM on the CPU.

[0037] 2 shows a control flow when the operations of the noise frequency analysis unit 33, comparison unit 34, acoustic spectrum storage unit 35, and frequency setting unit 36 ​​are executed by a control program. Note that this control flow shows the basic concept, and includes many other control steps. Below, the control flow will be explained for each control step.

[0038] <Step S10> In step S10, the reference acoustic spectrum data is downloaded from the external memory 32 via the communication line 31 and stored in the acoustic spectrum storage unit 35. The reference acoustic spectrum is a reference acoustic spectrum that is generated when the measurement target gas is irradiated with laser pulse light at a specific excitation frequency at which the gas components of the measurement target gas undergo thermal expansion and contraction. This reference acoustic spectrum has a distribution of high intensity across a predetermined frequency band (see FIG. 3). Once the storage of the reference acoustic spectrum data is complete, the process proceeds to step S11.

[0039] <Step S11> In step S11, a peak search is performed to find the maximum acoustic intensity of the reference acoustic spectrum stored in the acoustic spectrum storage unit 35, and the peak frequency (fp) at which the influence of the laser pulse light is greatest, i.e., the peak value at which the absorbance is maximum, is selected. In other words, if the laser pulse light is emitted at this peak frequency, the gas component can be detected efficiently. Once the peak frequency (fp) is selected, the process proceeds to step S12.

[0040] <Step S12> In step S12, a frequency analysis of the ambient noise detected by the microphone 17 is performed under the condition that no laser pulse light is irradiated from the light source 15. A fast Fourier transform can be used for the frequency analysis. Once the frequency analysis of the ambient noise is performed and a noise acoustic spectrum is obtained, the process proceeds to step S13.

[0041] <Step S13> In step S13, a predetermined measurement frequency band is set with the peak frequency (fp) determined in step S11 as the center. In this embodiment, the measurement frequency band is set as "fp±f LPF " Note that fLPF is the frequency band determined by the low-pass filter. The sound intensity of the noise sound spectrum is determined in this measurement frequency band.

[0042] That is, it is determined whether the acoustic intensity of the noise acoustic spectrum exceeds a predetermined intensity threshold. In this embodiment, the predetermined intensity threshold is set to "50 dB." Therefore, if the acoustic intensity of the noise acoustic spectrum exceeds "50 dB" within the measurement frequency band, the frequency of this measurement frequency band is not set as the drive frequency of the lock-in clock. On the other hand, if the acoustic intensity of the noise acoustic spectrum does not exceed "50 dB," the center frequency of this measurement frequency band is set as the drive frequency of the lock-in clock.

[0043] Therefore, if the determination in this control step is "No", the process proceeds to step S14, and if the determination is "YES", the process proceeds to step S17.

[0044] <Step S14> Since it is determined in step S13 that the acoustic intensity of the noise acoustic spectrum exceeds "50 dB" within the measurement frequency band, in step S14 the peak frequency (fp) is shifted by "2 × fLPF" toward the lower frequency side to set a new peak frequency (fpL). Then, a predetermined new measurement frequency band is set centered on the new peak frequency (fpL) on the lower frequency side. In this embodiment, the new measurement frequency band is set to "fpL ± fLPF."

[0045] Then, the frequency with the maximum acoustic intensity in the noise acoustic spectrum of the new measurement frequency band is determined. Once this frequency is determined, the process proceeds to step S15.

[0046] <Step S15> In step S15, the peak frequency (fp) is shifted to the higher frequency side by "2×fLPF" to obtain a new peak frequency (fpH). Then, a predetermined new measurement frequency band is set centered on the new peak frequency (fpH) on the higher frequency side. In this embodiment, the new measurement frequency band is set to "fpH±fLPF."

[0047] Then, the frequency with the maximum acoustic intensity in the noise acoustic spectrum of the new measurement frequency band is determined. Once this frequency is determined, the process proceeds to step S16.

[0048] <Step S16> In step S16, the frequency at which the acoustic intensity of the frequency found in step S14 is smaller than that of the frequency found in step S16 is selected. This makes it possible to set a measurement frequency band with even less environmental noise. The selected frequency is replaced with the peak frequency (fp) used in step S13, and the process returns to step S13 to execute the process again.

[0049] In step S13, the measurement frequency band "fp±fLPF" is set with the peak frequency (fp) found in step S16 as the center, and the sound intensity of the noise sound spectrum is determined in this measurement frequency band. Steps S13 to S16 are then repeated, and the process proceeds to step S17.

[0050] <Step S17> In step S17, the frequency (fp) at the center of the measurement frequency band set in step S13 is set in the lock-in clock generating unit 12 as the drive frequency of the light source 15.

[0051] A supplementary explanation of the above-mentioned control process will be given based on Fig. 3. Fig. 3 shows a noise sound spectrum and a reference sound spectrum.

[0052] In the overlapping region between the noise and reference sound spectra, the first measurement frequency band is set around the peak frequency of the reference sound spectrum. This measurement frequency band contains the maximum value of the noise sound spectrum, which may be detected as the odor intensity.

[0053] Therefore, if the maximum intensity exceeds the intensity threshold "50 dB," a similar measurement frequency band is set on the low frequency side, and if the acoustic intensity of the environmental noise at this time does not exceed the intensity threshold, the center frequency of this measurement frequency band is used as the drive frequency of light source 15. Although the measurement frequency band is not shown on the high frequency side in Figure 3, it can be set in the same way as on the low frequency side.

[0054] 2, the absolute value (intensity threshold) of the sound intensity of the environmental noise is used as the judgment criterion, but it is also possible to compare the difference between the maximum sound intensity of the reference sound spectrum and the maximum sound intensity of the noise sound spectrum with a predetermined allowable difference threshold and judge whether it is greater than the predetermined allowable difference threshold. Therefore, if the difference is smaller than the allowable difference threshold, the process proceeds to step S14, and if the difference is greater than the allowable difference threshold, the process proceeds to step S17.

[0055] In this way, the light source 15 is driven while avoiding the noise acoustic spectrum band where the noise intensity is high, so that sufficient sensitivity and discrimination accuracy of the photoacoustic sensor can be ensured. [Example]

[0056] Next, a second embodiment of the present invention will be described. This second embodiment is based on the premise that laser pulse light from light source 15 is irradiated onto a measurement target gas in resonance cell 16 at the drive frequency set in the first embodiment, and the gas components of the measurement target gas are measured.

[0057] In odor detection device 10, if environmental noise suddenly occurs while measuring the gas components of the measurement target gas, there is a risk of erroneous measurement if this environmental noise is measured by microphone 17. For this reason, when sudden environmental noise is measured, it is necessary to avoid erroneous measurement by not adopting the measurement results. Therefore, in this embodiment, as shown in FIG. 1, a fluctuation amount detection unit 37 is provided to avoid erroneous measurement.

[0058] The fluctuation amount detection unit 37 monitors the phase output of the lock-in detection unit 20, compares the average value of the phase output (1st to N-1th) with the most recent phase output (Nth), and operates so as not to adopt the Nth measurement result if the fluctuation amount is a predetermined value, for example, a change of 10% or more. As mentioned above, the phase output has a correlation with the intensity output, so although the phase output is used in this embodiment, the intensity output can also be used directly. The control flow will be explained below with reference to Figure 4.

[0059] <Step S20> If the current acquisition of the phase output is the "Nth time," then in step S20, the average value (Savg) of the "1st" to "N-1th" times of the phase output from the lock-in detection unit 20 is calculated. This average value (Savg) becomes the center value of the allowable range for acquiring the phase output. Once the average value (Savg) is calculated, the process proceeds to step S21.

[0060] <Step S21> In step S21, the phase output (Sn) captured at this (Nth) timing is saved. The captured phase output (Sn) is temporarily stored in RAM, and when this is completed, the process proceeds to step S22.

[0061] <Step S22> In step S22, it is determined whether the currently acquired phase output (Sn) is within the acquisition allowable range defined by "0.9 x Savg" and "1.1 x Savg".

[0062] Figure 5 shows the relationship between the capture tolerance range and phase output. As shown in Figure 5, the capture tolerance range is set between the upper limit phase output determined by "1.1 x Savg" and the lower limit phase output determined by "0.9 x Savg." If the current phase output (Sn) satisfies the conditions "Sn<1.1 x Savg" and "Sn>0.9 x Savg," it is assumed that there are no sudden fluctuations.

[0063] Therefore, if the current (Nth) phase output is within the allowable range, it is determined to be a normal phase output. On the other hand, if the current (Nth) phase output is not within the allowable range, it is considered that sudden environmental noise has occurred, and the phase output is determined to be abnormal.

[0064] In this way, if it is determined that the phase output (Sn) is within the allowable range of capture (YES determination), the process proceeds to step S23, and if it is determined that the phase output (Sn) is outside the allowable range of capture (NO determination), the process proceeds to step S24.

[0065] <Step S23> In step S23, since it is determined that the phase output is normal, the intensity output of the lock-in detection unit 20, which is the measurement result, is sent to the I / O unit 30. Once the intensity output has been sent, the process proceeds to step S25.

[0066] <Step S24> In step S24, since it is determined that the phase output is abnormal, the intensity output of the lock-in detection unit 20, which is the measurement result, is ignored and stopped from being sent to the I / O unit 30. Once the transmission of the intensity output has stopped, the process proceeds to step S25.

[0067] <Step S25> In step S25, it is determined whether or not to continue measuring the gas components of the current measurement target gas. If the measurement is to be continued (YES determination), the process returns to step S20 and the control steps of steps S20 to S25 are repeated.

[0068] On the other hand, if the measurement of the gas components is not to be continued, that is, if it is to be stopped (NO determination), the flow goes to END and this control flow is terminated.

[0069] In this way, in this embodiment, even if environmental noise suddenly occurs while measuring the gas components of the gas to be measured, it is possible to avoid erroneous measurements that would occur if the microphone 17 were to measure this environmental noise. [Example]

[0070] Next, a third embodiment of the present invention will be described. This third embodiment is also an embodiment for avoiding erroneous measurements due to the microphone 17 measuring environmental noise that may suddenly occur during measurement of the gas components of the measurement target gas.

[0071] In addition, this embodiment also assumes that laser pulse light is irradiated from light source 15 onto the gas to be measured in resonance cell 16 at the drive frequency set in the first embodiment, and the gas components of the gas to be measured are measured.

[0072] The fluctuation detection unit 37 monitors the intensity output of the lock-in detection unit 20, compares the temporal fluctuation (differential value) of the intensity output with a predetermined fluctuation threshold, and operates not to adopt the current (Nth) measurement result if the temporal fluctuation is greater than or equal to the predetermined fluctuation threshold. As mentioned above, the intensity output has a correlation with the phase output, so although the intensity output is used in this embodiment, the phase output can also be used directly. The control flow will be explained below with reference to Figure 6.

[0073] <Step S30> If the current intensity output acquisition is the "Nth time," then in step S30, the "1st" to "N-1th" intensity outputs (Pn) of the lock-in detection unit 30 are stored in chronological order. Once the intensity output (Pn) is calculated, the process proceeds to step S31.

[0074] <Step S31> In step S31, the intensity difference (ΔPn) between the intensity output (Pnnew) captured at the current (Nth) timing and the intensity output (Pnold) captured at the previous timing, i.e., the amount of fluctuation in the intensity output, is calculated. Here, the previous intensity output (Pnold) may be not only the previous one, but also the intensity output captured at the timing before last or even the timing before that. In this embodiment, the explanation will be given assuming it is the previous timing. Once the intensity difference is calculated, the process proceeds to step S32.

[0075] <Step S32> In step S32, the calculated current intensity difference (ΔPn) is compared with a predetermined intensity difference threshold (ΔPnthd), which is a predetermined fluctuation threshold, to determine whether or not sudden environmental noise has occurred.

[0076] Fig. 7 shows the relationship between the normal intensity output of a normal lock-in detector 20 and the intensity output when sudden environmental noise occurs. As shown in Fig. 7, the change in intensity output at acquisition timings t0 to t2 normally changes from "Pn0" to "Pn1n" between time t0 and time t1, but when sudden environmental noise occurs, it changes significantly from "Pn0" to "Pn1a" as shown by the dashed line.

[0077] Similarly, between time t1 and time t2, the signal normally changes from "Pn1n" to "Pn2n," but if sudden environmental noise occurs, it changes significantly from "Pn1a" to "Pn2a," as shown by the dashed line. In this way, the occurrence of sudden environmental noise can be determined by comparing the magnitude of the intensity difference (ΔPn) of the intensity output with the intensity difference threshold (ΔPnthd).

[0078] Therefore, if it is determined that the intensity difference (ΔPn) is smaller than the intensity difference threshold (ΔPnthd) (YES judgment), the process proceeds to step S33, and if it is determined that the intensity difference (ΔPn) is larger than the intensity difference threshold (ΔPnthd) (NO judgment), the process proceeds to step S34.

[0079] <Step S33> In step S233, since the intensity output is determined to be normal, the intensity output of the lock-in detection unit 20, which is the measurement result, is sent to the I / O unit 30. After the intensity output is sent, the process proceeds to step S35.

[0080] <Step S34> In step S34, since it is determined that the intensity output is abnormal, the intensity output of the lock-in detection unit 20, which is the measurement result, is ignored and its transmission to the I / O unit 30 is stopped. Once the transmission of the intensity output is stopped, the process proceeds to step S35.

[0081] <Step S35> In step S35, it is determined whether or not to continue measuring the gas components of the current measurement target gas. If the measurement is to be continued (YES determination), the process returns to step S30 and the control steps of steps S30 to S35 are repeated.

[0082] On the other hand, if the measurement of the gas components is not to be continued, that is, if it is to be stopped (NO determination), the flow goes to END and this control flow is terminated.

[0083] In this way, in this embodiment, even if environmental noise suddenly occurs while measuring the gas components of the gas to be measured, it is possible to avoid erroneous measurements that would occur if the microphone 17 were to measure this environmental noise. [Example]

[0084] Next, a fourth embodiment of the present invention will be described with reference to Fig. 8. This embodiment makes it possible to detect data abnormalities in the measurement results by comparing the peak search results with past measurement results.

[0085] <Step S40> In step S40, in addition to the reference photoacoustic spectrum data, past measurement results at a certain point in time, for example, the same time on the previous day, are also downloaded.

[0086] <Step S41> In step S41, a peak search is performed in the same manner as in step S11 in FIG.

[0087] <Step S42> In step S42, the comparison unit 34 compares the current acoustic wave intensity at the peak frequency with the past acoustic wave intensity, and if the difference in intensity is within a set threshold value, the process proceeds to step S43 and subsequent steps.

[0088] Step S43 to Step S48 Note that steps S43 to S48 are the same control operations as steps S12 to S17 shown in FIG. 2, and therefore a description thereof will be omitted.

[0089] <Step S49> Returning to step S42, if a fluctuation (difference in intensity) greater than the set threshold occurs, the process proceeds to step S49. In step S49, the comparison unit 34 issues an alert to the measurement control unit 29 indicating that a sensor abnormality or a major disturbance has occurred in the installation environment, and the measurement control unit 29 outputs an instruction to stop the measurement.

[0090] Here, the past measurement results used for comparison are not limited to data from the same time on the previous day, and can be set arbitrarily by the user. Furthermore, the comparison of the peak search results with the past measurement results does not necessarily have to be performed by the sensor, but the peak search results may be sent to the external memory 32 via the I / O unit and performed in the external memory 32. Furthermore, the comparison may be sent from the external memory 32 to a computer such as a server and executed on the computer.

[0091] In this manner, in this embodiment, by comparing the peak search results with past measurement results, it becomes possible to detect data abnormalities in the measurement results, thereby making it possible to increase the reliability of the data.

[0092] As described above, according to the present invention, the control means is equipped with a band setting means that operates in a state where light is not irradiated from the light source, compares a previously measured reference acoustic spectrum of the measurement target gas with a noise acoustic spectrum obtained by analyzing environmental noise in the frequency analysis unit, and sets a predetermined measurement frequency band in which both acoustic spectra overlap, and a drive frequency setting means that, when the acoustic intensity of the noise acoustic spectrum in the measurement frequency band is greater than a predetermined intensity threshold, sets another measurement frequency band different from the measurement frequency band, and sets the predetermined frequency of this newly set another measurement frequency band as the frequency of the drive signal for the light source drive means.

[0093] This makes it possible to provide an odor detection device and a control method thereof that can ensure sufficient sensitivity and discrimination accuracy of the photoacoustic sensor even in the presence of environmental noise.

[0094] The present invention is not limited to the above-described embodiments, but includes various modifications. The above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. It is also possible to add, delete, or replace other configurations with respect to the configuration of each embodiment. [Explanation of symbols]

[0095] 10...Odor detection device, 11...Master clock generation unit, 12...Lock-in clock generation unit, 13...Pulse generation unit, 14...Light source drive unit, 15...Light source, 16...Resonance cell, 17...Microphone, 18...Acoustic detection unit, 19...AD converter, 20...Lock-in detection unit, 21...Multiplier, 22...90° shift unit, 23...Multiplier, 24...Low-pass filter, 25...Intensity calculation unit, 26...Low-pass filter, 27...Phase calculation unit, 28...Odor concentration calculation unit, 29...Measurement control unit, 30...I / O unit, 31...Communication line, 32...External memory, 33...Noise frequency analysis unit, 34...Comparator, 35...Acoustic spectrum storage unit, 36...Frequency setting unit

Claims

1. a sensor cell that forms an internal space and stores a gas to be measured; a light source that irradiates light onto the gas in the sensor cell; a light source driving means for causing the light source to emit light intermittently with a driving signal having a predetermined measurement frequency; a microphone for detecting an acoustic wave of a specific gas in the sensor cell; a signal processing means for processing the acoustic wave detected by the microphone; The device includes a control means for executing at least a light source driving function for providing a driving signal to the light source driving means and a gas estimation function for estimating the type of a specific gas based on a signal from the signal processing means, the control means operates under a condition in which no light is emitted from the light source; a band setting means for comparing a reference acoustic spectrum of the measurement target gas measured in advance with a noise acoustic spectrum obtained by analyzing environmental noise using a frequency analysis unit, and setting a predetermined measurement frequency band in which both acoustic spectra overlap; a drive frequency setting means for setting another measurement frequency band different from the measurement frequency band when the acoustic intensity of the noise acoustic spectrum in the measurement frequency band is greater than a predetermined intensity threshold, and setting a predetermined frequency of the newly set another measurement frequency band as the frequency of the drive signal of the light source drive means; The control means further includes a lock-in detection unit, and the control means controls the light source to irradiate the light. The lock-in detection unit outputs an intensity output of the acoustic wave based on the signal from the signal processing means, measures the concentration of the odor based on the intensity output, and the lock-in detector outputs a phase output in addition to the intensity output, The control means sets an acquisition tolerance range based on the average value of the phase output, and ignores the intensity output if the latest phase output does not fall within the acquisition tolerance range. An odor detection device characterized by:

2. The odor detection device according to claim 1, the control means includes an I / O unit, the I / O unit is connected to an external memory via a communication line, and data of the reference acoustic spectrum of the measurement target gas is stored in the external memory; The control means retrieves the data of the reference acoustic spectrum from the external memory through the communication line and the I / O unit. An odor detection device characterized by:

3. A sensor cell forming an internal space and storing a gas to be measured; a light source that irradiates light onto the gas in the sensor cell; a light source driving means for causing the light source to emit light intermittently with a driving signal having a predetermined measurement frequency; a microphone for detecting an acoustic wave of a specific gas in the sensor cell; a signal processing means for processing the acoustic wave detected by the microphone; The device includes a control means for executing at least a light source driving function for providing a driving signal to the light source driving means and a gas estimation function for estimating the type of a specific gas based on a signal from the signal processing means, the control means operates under a condition in which no light is emitted from the light source; a band setting means for comparing a reference acoustic spectrum of the measurement target gas measured in advance with a noise acoustic spectrum obtained by analyzing environmental noise using a frequency analysis unit, and setting a predetermined measurement frequency band in which both acoustic spectra overlap; a drive frequency setting means for setting another measurement frequency band different from the measurement frequency band when the acoustic intensity of the noise acoustic spectrum in the measurement frequency band is greater than a predetermined intensity threshold, and setting a predetermined frequency of the newly set another measurement frequency band as the frequency of the drive signal of the light source drive means; The control means further includes a lock-in detection unit, and the control means controls the light source to irradiate the light. The lock-in detection unit outputs an intensity output of the acoustic wave based on the signal from the signal processing means, measures the concentration of the odor based on the intensity output, and The control means determines a temporal intensity fluctuation amount of the intensity output from the lock-in detection unit, and ignores the intensity output if the intensity fluctuation amount is greater than a predetermined intensity fluctuation threshold value. An odor detection device characterized by:

4. A sensor cell forming an internal space and storing a gas to be measured; a light source that irradiates light onto the gas in the sensor cell; a light source driving means for causing the light source to emit light intermittently with a driving signal having a predetermined measurement frequency; a microphone for detecting an acoustic wave of a specific gas in the sensor cell; a signal processing means for processing the acoustic wave detected by the microphone; The device includes a control means for executing at least a light source driving function for providing a driving signal to the light source driving means and a gas estimation function for estimating the type of a specific gas based on a signal from the signal processing means, the control means operates under a condition in which no light is emitted from the light source; a band setting means for comparing a reference acoustic spectrum of the measurement target gas measured in advance with a noise acoustic spectrum obtained by analyzing environmental noise using a frequency analysis unit, and setting a predetermined measurement frequency band in which both acoustic spectra overlap; a drive frequency setting means for setting another measurement frequency band different from the measurement frequency band when the acoustic intensity of the noise acoustic spectrum in the measurement frequency band is greater than a predetermined intensity threshold, and setting a predetermined frequency of the newly set another measurement frequency band as the frequency of the drive signal of the light source drive means; The control means outputs an instruction to stop measurement when a difference in intensity between a previously measured sound spectrum and the sound spectrum of the measurement frequency band is smaller than a predetermined threshold value. An odor detection device characterized by:

5. A sensor cell forming an internal space and storing a gas to be measured; a light source that irradiates light onto the gas in the sensor cell; a light source driving means for causing the light source to emit light intermittently with a driving signal having a predetermined measurement frequency; a microphone for detecting an acoustic wave of a specific gas in the sensor cell; a signal processing means for processing the acoustic wave detected by the microphone; A control method for an odor detection device including a control means for executing at least a light source driving function for providing a driving signal to the light source driving means and a gas estimation function for estimating the type of a specific gas based on a signal from the signal processing means, The control means, under a state in which light is not emitted from the light source, A reference acoustic spectrum of the gas to be measured, which has been measured in advance, is compared with a noise acoustic spectrum obtained by analyzing environmental noise using a frequency analysis unit, and a predetermined measurement frequency band in which both acoustic spectra overlap is set. If the acoustic intensity of the noise acoustic spectrum in the measurement frequency band is greater than a predetermined intensity threshold, another measurement frequency band different from the measurement frequency band is set, and a predetermined frequency of this newly set another measurement frequency band is set as the frequency of the drive signal of the light source drive means, the control means includes a lock-in detection unit, and in a state in which light is irradiated from the light source by the control means, the lock-in detection unit outputs an intensity output of the acoustic wave based on a signal from the signal processing means; causing the lock-in detection unit to output a phase output in addition to the intensity output; Setting a capture tolerance set by the average value of the phase outputs, and ignoring the intensity output if the latest phase output is not within the capture tolerance. A method for controlling an odor detection device.

6. A sensor cell forming an internal space and storing a gas to be measured; a light source that irradiates light onto the gas in the sensor cell; a light source driving means for causing the light source to emit light intermittently with a driving signal having a predetermined measurement frequency; a microphone for detecting an acoustic wave of a specific gas in the sensor cell; a signal processing means for processing the acoustic wave detected by the microphone; A control method for an odor detection device including a control means for executing at least a light source driving function for providing a driving signal to the light source driving means and a gas estimation function for estimating the type of a specific gas based on a signal from the signal processing means, The control means, under a state in which light is not emitted from the light source, A reference acoustic spectrum of the gas to be measured, which has been measured in advance, is compared with a noise acoustic spectrum obtained by analyzing environmental noise using a frequency analysis unit, and a predetermined measurement frequency band in which both acoustic spectra overlap is set. If the acoustic intensity of the noise acoustic spectrum in the measurement frequency band is greater than a predetermined intensity threshold, another measurement frequency band different from the measurement frequency band is set, and a predetermined frequency of this newly set another measurement frequency band is set as the frequency of the drive signal of the light source drive means, the control means includes a lock-in detection unit, and in a state in which light is irradiated from the light source by the control means, the lock-in detection unit outputs an intensity output of the acoustic wave based on a signal from the signal processing means; A temporal intensity fluctuation amount of the intensity output from the lock-in detection unit is obtained, and if the intensity fluctuation amount is greater than a predetermined intensity fluctuation threshold, the intensity output is ignored. A method for controlling an odor detection device.

7. A sensor cell forming an internal space and storing a gas to be measured; a light source that irradiates light onto the gas in the sensor cell; a light source driving means for causing the light source to emit light intermittently with a driving signal having a predetermined measurement frequency; a microphone for detecting an acoustic wave of a specific gas in the sensor cell; a signal processing means for processing the acoustic wave detected by the microphone; The device includes a control means for executing at least a light source driving function for providing a driving signal to the light source driving means and a gas estimation function for estimating the type of a specific gas based on a signal from the signal processing means, the control means operates under a condition in which no light is emitted from the light source; a band setting means for comparing a reference acoustic spectrum of the measurement target gas measured in advance with a noise acoustic spectrum obtained by analyzing environmental noise using a frequency analysis unit, and setting a predetermined measurement frequency band in which both acoustic spectra overlap; a drive frequency setting means for setting another measurement frequency band different from the measurement frequency band when a difference intensity between the maximum sound intensity of the noise sound spectrum in the measurement frequency band and the maximum sound intensity of the reference sound spectrum is smaller than a predetermined difference intensity threshold, and setting a predetermined frequency of this newly set another measurement frequency band as the frequency of the drive signal of the light source drive means; An odor detection device comprising:

8. A sensor cell forming an internal space and storing a gas to be measured; a light source that irradiates light onto the gas in the sensor cell; a light source driving means for causing the light source to emit light intermittently with a driving signal having a predetermined measurement frequency; a microphone for detecting an acoustic wave of a specific gas in the sensor cell; a signal processing means for processing the acoustic wave detected by the microphone; A control method for an odor detection device including a control means for executing at least a light source driving function for providing a driving signal to the light source driving means and a gas estimation function for estimating the type of a specific gas based on a signal from the signal processing means, The control means, under a state in which light is not emitted from the light source, A reference acoustic spectrum of the gas to be measured, which has been measured in advance, is compared with a noise acoustic spectrum obtained by analyzing environmental noise using a frequency analysis unit, and a predetermined measurement frequency band in which both acoustic spectra overlap is set. If the difference intensity between the maximum sound intensity of the noise sound spectrum in the measurement frequency band and the maximum sound intensity of the reference sound spectrum is smaller than a predetermined difference intensity threshold, another measurement frequency band different from the measurement frequency band is set, and a predetermined frequency of this newly set another measurement frequency band is set as the frequency of the drive signal of the light source drive means. A method for controlling an odor detection device.

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