JP2022026652A - Photoacoustic sensor, method for calibrating photoacoustic sensor, and air conditioning system - Google Patents

Abstract

To provide a new photoacoustic sensor, a method for calibrating the photoacoustic sensor, and an air-conditioning system, with which it is possible to accurately estimate at least the types of gas components independently of influences of temperature.SOLUTION: The photoacoustic sensor comprises: a sensor cell 14 for forming an inner space and storing the gas to be measured; a light source 15 for irradiating the gas in the sensor cell 14 with light; light source drive means 20 for causing the light source 15 to intermittently emit light; a microphone 18 for detecting the acoustic wave of a specific gas in the sensor cell 14; signal processing means 25 for processing the acoustic wave detected by the microphone 18; and control means 23 for executing a light source drive function to apply a drive signal to the light source drive means 20 and a gas estimation function to estimate the type of the specific gas on the basis of signals from the signal processing means 25. The gas estimation function of the control means 23 finds the average molecular weight of the specific gas on the basis of the frequency of the acoustic wave and the temperature information of the gas and estimates the type of the specific gas from the average molecular weight thus obtained.SELECTED DRAWING: Figure 2

Description

The present invention relates to a photoacoustic sensor that detects a gas component, a photoacoustic sensor calibration method, and an air conditioning system.

Generally, in offices, commercial facilities, factories, etc., the temperature and humidity of the indoor air, which is the living environment, are controlled. However, recently, there is an increasing demand for controlling air quality, such as not only controlling temperature and humidity, but also removing harmful gases and unpleasant odors, and adding fragrances and the like.

In order to control this air quality, it is necessary to appropriately control the gas concentration and the odor concentration, and a gas sensor that detects the gas component and the odor component according to the purpose is required. As a sensor for detecting a gas component or an odor component, a photoacoustic sensor using a photoacoustic effect has been proposed.

The photoacoustic effect is an acoustic wave in which when light of a specific wavelength is intermittently (pulse-shaped) applied to a molecule of a specific component constituting a gas, the molecule that has absorbed the light undergoes thermal expansion and contraction. This is a phenomenon in which (sound waves) are generated. Photoacoustic sensors are small in size and capable of detecting low-concentration gases with high sensitivity, and are therefore being applied to air conditioning systems in buildings. The photoacoustic sensor can be applied not only to the air conditioning system but also to other fields, but the application example of the air conditioning system will be described below.

The photoacoustic sensor encloses the measurement gas in a housing that forms a closed space called a cell, irradiates the light in a pulse shape to generate an acoustic wave, and the peak frequency (intensity is maximized) of this acoustic wave. The gas component is specified from the frequency). In the photoacoustic sensor used in the air conditioning system, at least one connection hole is formed in the cell in order to circulate the air outside the cell (indoor air) in the cell.

However, since the peak frequency of the acoustic wave generated by the photoacoustic effect tends to depend on the temperature of the measured gas, if the air temperature in the room changes, the estimation of the type of gas component may be erroneous. Therefore, it is required to compensate for the temperature dependence.

As a technique for responding to such a request, for example, in Japanese Patent Application Laid-Open No. 2001-507798 (Patent Document 1), a gas having a known type and concentration of a gas component is used to correct an unknown gas concentration calculation. It is shown to do.

Special Table 2001-507798 Gazette

By the way, in Patent Document 1, the concentration calculation of an unknown gas is corrected by using a gas having a known type and concentration, but if a known gas cannot be prepared, the type of gas is estimated and the gas is used. It has a problem that the concentration of a component cannot be measured, and a problem that the accuracy of estimating the type of gas and calculating the concentration of a gas component is lowered when a known gas leaks due to aged deterioration. Therefore, a photoacoustic sensor as in Patent Document 1 requires maintenance of a known gas, and it is not a good idea to adopt it in an air conditioning system, for example.

An object of the present invention is a novel photoacoustic sensor capable of accurately estimating the type of gas component at least without depending on temperature without using a known gas or the like, a method for calibrating a photoacoustic sensor, and a method for calibrating the photoacoustic sensor. It is to provide an air conditioning system.

The present invention comprises a sensor cell that forms an internal space and stores the measured gas, a light source that irradiates the gas in the sensor cell with light, a light source driving means that causes the light source to emit light intermittently, and an acoustic sound of a specific gas in the sensor cell. A microphone that detects waves, a signal processing means that processes acoustic waves detected by the microphone, at least a light source driving function that gives a driving signal to the light source driving means, and a specific gas based on a signal from the signal processing means. It is equipped with a control means that executes a gas estimation function that estimates the type, and the gas estimation function of the control means obtains the average molecular weight of a specific gas using the frequency of the acoustic wave and the temperature information of the gas, and specifies it from the obtained average molecular weight. It is characterized by estimating the type of gas.

According to the configuration of the present invention, it is possible to accurately estimate the type of gas component without depending on the temperature without using a known gas or the like. It should be noted that problems, configurations and effects other than those described above will be clarified by the following description of the embodiment for carrying out the invention.

It is a system diagram of the air conditioning system to which this invention is applied. It is explanatory drawing explaining the structure of the table which related the average molecular weight and a gas component. FIG. 3 is a flowchart illustrating a method for estimating a gas component according to a first embodiment executed in the air conditioning system shown in FIG. 1. FIG. 3 is a flowchart illustrating a method for estimating a gas component according to a second embodiment executed in the air conditioning system shown in FIG. 1. It is explanatory drawing explaining the structure of the table which related the intensity of an acoustic wave and the concentration of a gas component. FIG. 3 is a flowchart illustrating a method for estimating a gas component according to a third embodiment executed in the air conditioning system shown in FIG. 1. It is a system diagram of the air-conditioning system which becomes the 4th Embodiment of this invention. FIG. 5 is a flowchart illustrating a method for estimating a gas component according to a fourth embodiment executed in the air conditioning system shown in FIG. 7. It is a system diagram of the air-conditioning system which becomes the 5th Embodiment of this invention. FIG. 3 is a flowchart illustrating a method for estimating a gas component according to a fifth embodiment executed in the air conditioning system shown in FIG. 9. It is a system diagram of the air-conditioning system which becomes the 6th Embodiment of this invention. It is a system diagram of the air-conditioning system which becomes the 7th Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The embodiments are examples for explaining the present invention, and are appropriately omitted or simplified for the sake of clarification of the description. The present invention can also be implemented in various other forms.

First, the first embodiment of the present invention will be described with reference to FIGS. 1 and 2. Here, FIG. 1 shows an air conditioning system to which the present invention is applied, and FIG. 2 shows a flowchart illustrating a method for estimating a gas component according to a first embodiment implemented in the air conditioning system shown in FIG. ing.

In the air conditioning system shown in FIG. 1, the air conditioner (air conditioning means) 10 has a function of receiving sensor information from the sensor group 11 and executing an air conditioning operation based on the received signal. The sensor group 11 includes environment sensors such as a temperature sensor (temperature detecting means) for detecting the temperature of the living space, a CO ₂ sensor for detecting the CO ₂ concentration in the living space, and a dust sensor for detecting dust floating in the living space. It is composed of a heart rate sensor that detects the resident's heart rate and a human sensor such as a thermopile that detects the resident's body temperature.

Further, the air conditioner 10 is wirelessly or wiredly connected to a central management device (central management means) 12 composed of a server or the like, and operation information, sensor information, etc. are transmitted from the air conditioner 10 to the central management device 12. is doing. Further, the central management device 12 transmits the operation signal and the control signal of the air conditioner 10 to the air conditioner 10.

The photoacoustic sensor 13, which is a feature of the present embodiment, is connected to the air conditioner 10 wirelessly or by wire. The photoacoustic sensor 13 can be installed at any place such as an office, a commercial facility, or a factory. Further, although not shown in the drawing, it can be provided in the air conditioner 10 itself.

The photoacoustic sensor 13 is at least a sensor cell 14 that forms an internal space and stores a gas (here, air) to be measured, a light source A15 to a light source N17 that irradiate the gas (air) in the sensor cell 14 with light, and a sensor cell. It is provided with a microphone 18 for detecting an acoustic wave of air in the 14 and two connection holes 19 for connecting the internal space and the external space in the sensor cell 14. The two connection holes 19 are provided for circulating air in the sensor cell 14 as described above.

The light from the light source A15 to the light source N17 is emitted toward the internal space from the light incident portion formed in the sensor cell 14. Various light sources can be used as the light source A15 to the light source N17, and for example, a light source such as a semiconductor laser, a gas laser, or an LED can be used. In consideration of manufacturing cost and the like, LEDs are used in this embodiment. These light sources A15 to N17 are configured to emit light intermittently (in a pulse shape) to give light energy to the air stored in the sensor cell 14. As a result, the specific gas component to be measured in the sensor cell 14 repeats thermal expansion and contraction to generate an acoustic wave.

The wavelength of the light emitted from the light source A15 to the light source N17 is determined by the specific gas component to be measured, and in the present embodiment, the N light source A15 to the light source N17 are used so as to detect N gas components. It is prepared. Since an LED is used in this embodiment, an optical filter that transmits a predetermined wavelength is used to obtain a desired wavelength.

Since the light sources A15 to N17 emit light intermittently to give light energy to the air stored in the sensor cell 14, they are pulsed by the drive circuit (light source drive means) A20 to the drive circuit (light source drive means) N22. The light emission is controlled. Further, the drive circuit A20 to the drive circuit N22 are controlled to change (sweep) the frequency within a predetermined range in order to obtain (search) the peak frequency at which the intensity of the acoustic wave detected by the microphone 18 is maximized. Will be done.

Therefore, the drive circuit A20 to the drive circuit N22 are driven at a frequency determined by the control circuit unit (control means) 23. The control circuit unit 23 is composed of a microcomputer, an input / output circuit, and the like, and executes a predetermined function by control software stored in a ROM built in the microcomputer.

For example, at least, the function of changing the frequency of the drive circuit A20 to the drive circuit N22 described above (light source drive function), the function of obtaining the type and concentration of the gas component from the acoustic wave (gas estimation function), and the like are executed. The method of obtaining the type and concentration of the gas component from the acoustic wave will be described later.

Although the drive circuit A20 and the light source A15 will be described below, the same operation is performed for the other drive circuits B21 to the drive circuit N22 and the light source B16 to the light source N17.

The acoustic wave generated by the intermittent light emission of the light source A15 detected by the microphone 18 is converted into an electric signal by the detection circuit unit 24, and noise is further removed by the signal processing unit (signal processing means) 25. It is amplified and transmitted to the control circuit unit 23. The control circuit unit 23 obtains the drive frequency of the drive circuit A20 that causes this peak frequency from the peak frequency at which the intensity of the acoustic wave is maximized.

That is, since the emission frequency of the light source A15 and the frequency of the acoustic wave are substantially the same, the drive frequency of the drive circuit A20 is obtained in order to obtain a more accurate frequency. Since this drive frequency is generated by the control circuit unit 23 itself, this drive frequency may be obtained. The peak frequency at which the intensity of the acoustic wave is maximized and the intensity are temporarily stored in the memory (storage means) 26. The memory 26 is a rewritable memory, and a memory such as a battery-backed RAM, a flash ROM, or a microcomputer RAM can be used.

Further, the photoacoustic sensor 13 has a communication unit (communication means) 27 connected to the air conditioner 10 wirelessly or by wire, and the temperature information of the outside air (gas) detected by the temperature sensor of the sensor group 11. Is taken into the photoacoustic sensor 13 via the air conditioner 10. The captured temperature information is temporarily stored in the memory 26.

Many of the air conditioners 10 are provided with a temperature sensor for their own control, and the temperature sensor of the air conditioner 10 can be used to detect temperature information. Further, the temperature information is acquired from the air conditioner 10 or the sensor group 11 at the start of measurement of the photoacoustic sensor 13 or at predetermined intervals.

On the other hand, the gas component and its concentration obtained by the control circuit unit 23 are sent from the communication unit 27 to the air conditioner 10 and further to the central management device 12. The central control device 12 corresponds to the sent gas component and its concentration, and is an air conditioner 10, and an air quality adjusting device (air quality adjusting means) such as an odor adsorbing device, a dust collector, an ozone deodorizing device, and an aroma adding device. ) 28 is controlled. The air conditioner 10 can also be provided with the function of the air quality adjusting device 28.

Then, in the control circuit unit 23, the average molecular weight of the specific gas component to be measured is obtained from the drive frequency of the drive circuit A20 stored in the memory 26 and the temperature information of the air, and the specific gas component is obtained from the obtained average molecular weight. Performs an operation that estimates the type of. Specifically, the average molecular weight is obtained by executing the following operations on a microcomputer.

The resonance frequency (fr) of the acoustic wave of the sensor cell 14 can be expressed by the following equation (1). In a gas, the speed of sound generally depends on the specific heat ratio, average molecular weight, and temperature. Here, if "c" is the speed of sound, "κ" is the specific heat ratio of the gas, "R" is the gas constant, "T" is the gas temperature, and "M" is the average molecular weight of the gas, it is proportional to the resonance frequency (fr). The related sound velocity (c) is fr∝c = (κRT / M) ^1/2 …… (1)
It is expressed as.

For example, when the sensor cell 14 is composed of a combination of a detection cell (light source side) and a resonance cell (microphone side) connected to the detection cell (microphone side) via a duct, “fr∝c” is
fr = cd / 4π ・ ((π (V1 + V2) / LV1V2)) ^1/2 …… (2)
It is represented by. Here, "d" is the duct diameter, "L" is the duct length, "V1" is the detected cell volume, and "V2" is the resonance cell volume.

Other than the sound velocity (c) on the right side, it can be treated as a coefficient, which can be obtained in advance based on the configuration of the sensor cell 14.

Therefore, the speed of sound (c) can be calculated from the resonance frequency (fr) using the equation (2). Furthermore, in order to obtain the average molecular weight (M), equation (1) is transformed into a "predetermined arithmetic expression" (M = κRT / c ² ), and the speed of sound (c) and temperature (T) are substituted into this to average. The molecular weight (M) can be determined.

The equation (2) shows a case where the detection cell and the resonance cell are combined as the sensor cell 14, but there are cases where the sensor cell 14 is only the detection cell or there are two resonance cells. In this case, the coefficient portion of Eq. (2) may be modified accordingly, and the point is that the sound velocity (c) can be obtained from the resonance frequency (fr).

As described above, in the present embodiment, the average molecular weight (M) is obtained from the drive frequency (fr) of the light source corresponding to the resonance frequency and the temperature information (T) of the air stored in the memory 26. That is, the above-mentioned equation (1) is transformed into a "predetermined arithmetic expression" for which the average molecular weight (M) is obtained, and the drive frequency ( _fr ) and the air temperature information (T) are used from this predetermined arithmetic expression. Therefore, the average molecular weight (M) compensated for the temperature dependence can be obtained.

Then, the type of gas component is estimated from the obtained average molecular weight (M). As an estimation method, for example, as shown in FIG. 2, gas components A to N and corresponding average molecular weights A to N are tabulated, and the corresponding gas component is searched from the obtained average molecular weight (M). Therefore, the type of gas component can be estimated from the average molecular weight (M).

With the above configuration, it is possible to accurately estimate the type of gas component without depending on the temperature. In this embodiment, the concentration of the gas component is not estimated. The method of estimating the concentration of the gas component will be described in Example 2 below.

Next, a specific control flow executed by the microcomputer of the control circuit unit 23 will be described with reference to FIG. The control flow shown in FIG. 3 is activated by a temporal interrupt, and is executed, for example, by an interrupt generated by a compare match timer. Here, steps S11 and subsequent steps are control steps executed by the microcomputer of the control circuit unit 23.

<< Step S10 >>
In step S10, the temperature information is detected by the temperature sensor of the air conditioner 10 or the sensor group 11. The temperature information from this temperature sensor represents the average air temperature of the air circulating in the room. The purpose of obtaining the average air temperature is to prevent a temporary change in temperature from being detected so that an error does not occur in the calculation of the average molecular weight (M). When the temperature information is obtained, the process proceeds to step S11.

≪Step S11≫
In step S11, the temperature information obtained in step S10 is taken in via the communication unit 27 of the photoacoustic sensor 13, and the received temperature information is stored in a predetermined area of the memory 26. The stored temperature information is retained at least until the gas component described later is obtained. When the temperature information is stored, the process proceeds to step S12.

≪Step S12≫
In step S12, it is determined whether or not the operations of the drive circuit A20 to the drive circuit N22 for driving the light source A15 to the light source N17 are completed. That is, the operations of the drive circuit A20 to the drive circuit N22 are executed in order, and the acoustic wave is detected correspondingly. Therefore, when the operation of the drive circuit A20 to the drive circuit N22 is completed, the acoustic wave is detected. It is completed, which means that the estimation of the gas component is completed.

Therefore, when it is determined that the operations of all the drive circuits A20 to N22 are completed, the process exits to the "end" and the process of this control flow ends.

On the other hand, if it is determined that the operations of all the drive circuits A20 to N22 have not been completed, the process proceeds to step S13, and the gas component estimation process is continued. The estimation process described below is a process when the drive circuit A20 is driven. Since the estimation process of the gas component when the drive circuit B21 to the drive circuit N22 other than this is driven is substantially the same as the estimation process of the drive circuit A, the description thereof will be omitted.

≪Step S13≫
In step S13, the drive frequency of the drive circuit A20 is changed (sweep) at a constant speed, and the acoustic wave is measured by the microphone 18. By repeating this operation, the peak frequency at which the output intensity of the acoustic wave is maximized is searched for. This peak frequency is the frequency at which the gas component to be measured reacts most.

Since the drive frequency of the drive circuit A20 and the peak frequency of the acoustic wave substantially correspond to each other, the drive frequency of the drive circuit A20 at this time is determined as the peak frequency. When the peak frequency is obtained, the process proceeds to step S14.

<< Step S14 >>
In step S14, the peak frequency searched in step S13 is stored in a predetermined area of the memory 26. The stored peak frequency is maintained at least until the gas component described later is obtained. When the peak frequency is stored, the process proceeds to step S15.

≪Step S15≫
In step S15, the average molecular weight (M) is calculated using the temperature information stored in the memory 26 and the peak frequency. Specifically, the above-mentioned equation (1) is transformed into a "predetermined arithmetic expression" for which the average molecular weight (M) is obtained, and the peak frequency and temperature information are used in this predetermined arithmetic expression to make the temperature dependent. Can be obtained for the compensated average molecular weight (M). When the average molecular weight (M) is obtained, the process proceeds to step S16.

≪Step S16≫
In step S16, the type of gas component is estimated from the average molecular weight (M) obtained in step S15. In this estimation, as described above, the gas components A to N and the corresponding average molecular weights A to N are tabulated, and the corresponding gas components are table-looked up from the obtained average molecular weight (M). , The type of gas component can be estimated from the average molecular weight (M). In addition to the table lookup method, machine learning can also be used to estimate the type of gas component.

Then, when it is determined that the estimation of the gas component is completed, the process exits to the "end" and the processing of this control flow ends. On the other hand, the estimation of the gas component by the operation of the drive circuit B21 to the drive circuit N22 other than this can be performed by executing the above-mentioned steps S13 to S16.

By executing the calibration method as described above, it becomes possible to accurately estimate the type of gas component without depending on the temperature.

Next, a second embodiment of the present invention will be described with reference to FIG. The present embodiment is different from the first embodiment in that the concentration of the gas component is obtained from the intensity of the peak frequency. The description of the same control step as that shown in FIG. 3 will be omitted. Here, the air conditioning system of the present embodiment is basically the same as the system shown in FIG.

The control flow shown in FIG. 4 is also activated by a temporal interrupt, and is executed, for example, by an interrupt generated by a compare match timer. Here, steps S11 and subsequent steps are control steps executed by the microcomputer of the control circuit unit 23.

≪Step S10≫ ～ ≪Step S13≫
Since the control steps of steps S10 to S13 are the same as the control steps shown in FIG. 3, the description thereof will be omitted. Then, when the process up to step S13 is executed, the process proceeds to step S14A.

<< Step S14A >>
In step S14A, the peak frequency searched in step S13 and the intensity of the acoustic wave at this time are stored in a predetermined area of the memory 26. The stored peak frequency and intensity are retained at least until the gas component described below is sought. When the peak frequency is stored, the process proceeds to step S15.

≪Step S15≫ ～ ≪Step S16≫
Since the control steps of steps S15 to S16 are the same as the control steps shown in FIG. 3, the description thereof will be omitted. Then, when steps S15 to S16 are executed, the process proceeds to step S17.

≪Step S17≫
In step S17, the concentration of the gas component is estimated from the intensity of the acoustic wave obtained in step S14A. To estimate this concentration, the intensity of the acoustic wave and the corresponding concentration are tabulated, and the concentration of the corresponding gas component is table-looked up from the obtained intensity to obtain the concentration of the gas component from the intensity of the acoustic wave. Can be estimated.

For example, FIG. 5 shows the relationship between the intensity of the acoustic wave and the concentration of the gas component, and it can be understood that the concentration of the gas component can be obtained based on the intensity of the acoustic wave. Therefore, the relationships shown in FIG. 5 may be tabulated. Alternatively, the intensity of the acoustic wave itself may be regarded as the concentration of the gas component.

Then, when it is determined that the estimation of the type of gas component and the estimation of the concentration are completed, the process exits to the "end" and the processing of this control flow is terminated. On the other hand, the estimation of the type of gas component and the estimation of the concentration by the operation of the drive circuits B21 to N22 other than this can be performed by executing the above-mentioned steps S13 to S17.

By executing the calibration method as described above, it is possible to accurately estimate the type of gas component without depending on the temperature, and further, it becomes possible to estimate the concentration of the gas component from the intensity of the peak frequency. ..

Next, a third embodiment of the present invention will be described with reference to FIG. The present embodiment is different from the first embodiment and the second embodiment in that the gas component is estimated after the air temperature in the room is constant by the air conditioner 10. The description of the same control steps as those of the first embodiment and the second embodiment will be omitted. Here, the air conditioning system of the present embodiment is basically the same as the system shown in FIG.

The control flow shown in FIG. 6 is also activated by a temporal interrupt, and is executed, for example, by an interrupt generated by a compare match timer. Here, steps S11 and subsequent steps are control steps executed by the microcomputer of the control circuit unit 23.

≪Step S20≫
In step S20, desired set temperature information is transmitted from the central control device 12 to the air conditioner 10. In the air conditioner 10, the operation is started based on the set temperature information, and the operation is continued so that the indoor air approaches the set temperature. The process proceeds to step S21 while the air conditioner 10 continues to operate.

≪Step S21≫
In step S21, when it is determined by the temperature sensor of the air conditioner 10 that the room temperature has reached the set temperature while the air conditioner 10 continues to operate, the air conditioner 10 is set to itself. The temperature information is transmitted to the photoacoustic sensor 13 as air temperature information. When the transmission of the set temperature information is completed, the process proceeds to step S11.

≪Step S1≫ ～ ≪Step S16≫
Since the control steps of steps S11 to S16 are the same as the control steps shown in FIG. 3, the description thereof will be omitted.

Then, when it is determined that the estimation of the type of gas component is completed, the process exits to the "end" and the processing of this control flow ends. On the other hand, the estimation of the type of gas component by the operation of the drive circuits B21 to N22 other than this can be performed by executing the above-mentioned steps S13 to S16.

By executing the calibration method as described above, it becomes possible to accurately estimate the type of gas component without depending on the temperature. Further, by using the function of the air conditioner to control the air temperature in the room to the set temperature, it is possible to simplify the configuration of the sensor group. As in the second embodiment, the concentration of the gas component can be estimated from the intensity of the peak frequency.

Next, a fourth embodiment of the present invention will be described with reference to FIGS. 7 and 8. This embodiment is different from the first to third embodiments in that the photoacoustic sensor 13 is equipped with the temperature measurement function unit 29. It should be noted that the description of the same components as the components of the first embodiment to the third embodiment and the same control steps as the control steps shown in the first embodiment to the third embodiment will be omitted.

In FIG. 7, the photoacoustic sensor 13 includes a temperature measuring function unit 29, and the temperature measuring function unit 29 transmits temperature information to the control circuit unit 23. The temperature measuring function unit 29 can use a temperature measuring element such as a temperature sensor (resistance temperature detector or thermistor) or a thermopile provided on the circuit board of the photoacoustic sensor 13. A drive circuit 20 to 22 detection circuit unit 24, a signal processing circuit 25, a control circuit unit 23, and the like are mounted on the circuit board.

Next, a specific control flow executed by the microcomputer of the control circuit unit 23 will be described with reference to FIG. The air conditioning system of the present embodiment is basically the same as the system shown in FIG. 1 except that the temperature information is detected by the photoacoustic sensor 13.

The control flow shown in FIG. 8 is also activated by a temporal interrupt, and is executed, for example, by an interrupt generated by a compare match timer. Here, steps S22 and subsequent steps are control steps executed by the microcomputer of the control circuit unit 23.

<< Step S22 >>
In step S22, the temperature is detected by the temperature measuring function unit 29 using the temperature measuring element provided on the circuit board of the photoacoustic sensor 13, and the detected temperature information is stored in a predetermined area of the memory 26. The stored temperature information is retained at least until the gas component described later is obtained. When the temperature information is stored, the process proceeds to step S12.

≪Step S12≫ ～ ≪Step S16≫
Since the control steps of steps S12 to S16 are the same as the control steps shown in FIG. 3, the description thereof will be omitted.

Then, when it is determined that the estimation of the type of gas component is completed, the process exits to the "end" and the processing of this control flow ends. On the other hand, the estimation of the type of gas component by the operation of the drive circuits B21 to N22 other than this can be performed by executing the above-mentioned steps S12 to S16.

By executing the calibration method as described above, it becomes possible to accurately estimate the type of gas component without depending on the temperature. Further, even in a state where temperature information cannot be obtained from the side of the air conditioner 10, the type of gas component can be estimated only by the photoacoustic sensor 13. As in the second embodiment, the concentration of the gas component can be estimated from the intensity of the peak frequency.

Next, a fifth embodiment of the present invention will be described with reference to FIGS. 9 and 10. The present embodiment is different from the first to fourth embodiments in that the light source Q30 for measuring the known gas is mounted. The description of the same components as the components of the first to fourth embodiments and the same control steps as the control steps shown in the first to fourth embodiments will be omitted.

In FIG. 9, the photoacoustic sensor 13 includes a drive circuit Q30 and a light source Q31 for detecting a known gas component. By providing the light source Q31 for detecting the known gas component in this way, the temperature sensor for detecting the temperature information can be omitted. That is, since it is a known gas, if the average molecular weight (M) is known and the peak frequency (= drive frequency) of the acoustic wave can be detected, the temperature (T) in the equation (1) can be obtained by calculation.

Next, a specific control flow executed by the microcomputer of the control circuit unit 23 will be described with reference to FIG. The air conditioning system of the present embodiment is basically the same as the system shown in FIG. 1 except that the temperature information is obtained by calculation.

The control flow shown in FIG. 10 is also activated by a temporal interrupt, and is executed, for example, by an interrupt generated by a compare match timer. Here, steps S23 and subsequent steps are control steps executed by the microcomputer of the control circuit unit 23.

≪Step S23≫
In step S23, the drive frequency of the drive circuit Q30 is changed (sweep) at a constant speed, and the acoustic wave is measured by the microphone 18. While continuing to drive the drive circuit Q30, the process proceeds to step S24.

<< Step S24 >>
In step S24, the peak frequency at which the output intensity of the acoustic wave is maximized is searched for while repeating the sweep of the drive frequency of the drive circuit Q30. This peak frequency is the frequency at which the gas component of the known gas reacts most. When the peak frequency is detected, the temperature is calculated using Eq. (1).

This calculation is to calculate the temperature (T) from the average molecular weight (M) of a known gas and the speed of sound (c) obtained from the peak frequency. Since the speed of sound (c) can be obtained from the equation (2) as described above, the equation (1) described above is transformed into a "predetermined arithmetic expression" (T = c ² M / κR) from which the temperature (T) can be obtained. By substituting the speed of sound (c) and the average molecular weight (M) into this predetermined arithmetic expression, the temperature (T) can be obtained.

That is, the above-mentioned equation (1) is transformed into a "predetermined arithmetic expression" for which the temperature (T) is obtained, and the temperature is used from this predetermined arithmetic expression using the drive frequency (fr) of the light source and the average molecular weight (M). (T) can be obtained. When the temperature (T) is obtained, this temperature information is stored in a predetermined area of the memory 26. The stored temperature information is retained at least until the gas component described later is obtained. When the temperature information is stored, the process proceeds to step S12.

≪Step S12≫ ～ ≪Step S16≫
Since the control steps of steps S12 to S16 are the same as the control steps shown in FIG. 3, the description thereof will be omitted.

Then, when it is determined that the estimation of the type of gas component is completed, the process exits to the "end" and the processing of this control flow ends. On the other hand, the estimation of the type of gas component by the operation of the drive circuits B21 to N22 other than this can be performed by executing the above-mentioned steps S12 to S16.

By executing the calibration method as described above, it becomes possible to accurately estimate the type of gas component without depending on the temperature. In addition, it is possible to estimate the type of gas component only with a photoacoustic sensor without using a temperature sensor. As in the second embodiment, the concentration of the gas component can be estimated from the intensity of the peak frequency.

Next, a sixth embodiment of the present invention will be described with reference to FIG. In the present embodiment, a pair of light sources having the same wavelength are provided, and the average current value of the drive circuit connected to each light source is monitored by the current measurement circuit to determine the deterioration of the light source and issue an alarm. It is different from the fifth embodiment. The description of the same components as those of the first to fifth embodiments will be omitted. Here, the deterioration of the light source is the deterioration of the light source including the drive circuit.

In FIG. 11, a pair of light sources A15 and a light source A'15'of the same wavelength, a drive circuit A20 for driving the light source A'15', and a drive circuit A'20'are provided. A current measurement circuit A32 and a current measurement circuit A'32'are interposed between them. Therefore, the current measuring circuit A32 and the current measuring circuit A'32'measure the average current value flowing through the light source A15 and the light source A'15'.

Similarly, the light source B16, the drive circuit B21, the light source N17, and the drive circuit 22 are also provided with a paired light source and a drive circuit, and a current measurement circuit is also provided corresponding to these. FIG. 11 shows a light source N ′ 17 ′, a drive circuit N22 ′ driving the light source N ′ 17 ′, and a current measurement circuit N ′ 33 ′.

Then, when the photoacoustic sensor 13 is activated, the microcomputer of the control circuit unit 23 compares the average current values measured by the current measurement circuit A32 and the current measurement circuit A'32', and the difference is stored in the memory 26. Stored.

When the difference stored in the memory 26 is larger than a predetermined difference threshold value (for example, the difference of the average current value in the normal case), the microcomputer determines that the light source including the drive circuit is deteriorated. , Output an alarm. The alarm is transmitted to the air conditioner 10 and the central management device 12 via the communication unit 27, and can notify the deterioration of the photoacoustic sensor 13. Further, an alarm can be output by the blinking lamp 34 provided in the photoacoustic sensor 13.

As described above, in the microcomputer, the difference between the average current values measured by the pair of current measurement circuits deviates from a predetermined predetermined difference threshold value (difference between the average current values in the normal case). In some cases, an alarm generation function for generating an alarm is provided.

In addition to the above-mentioned method, various methods can be considered for detecting that the light source including the drive circuit is deteriorated. For example, if there is a difference of 20% or more between the average current values of the pair of drive circuits, an alarm can be issued assuming that the light source including the drive circuits is deteriorated. Further, regarding the intensity of the acoustic wave due to the deteriorated light source, the intensity can be corrected corresponding to the difference in the average current value.

By executing the calibration method as described above, it becomes possible to accurately estimate the type of gas component without depending on the temperature. In addition, it is possible to notify the deterioration of the light source of the photoacoustic sensor 13. Further, in the case where the concentration of the gas component is estimated from the intensity of the peak frequency as in the second embodiment, the deterioration of the light source can be detected and the intensity of the acoustic wave can be corrected. It is possible to improve the estimation accuracy of the concentration of the component.

Next, a seventh embodiment of the present invention will be described with reference to FIG. In the present embodiment, a pair of microphones 18 and 18'are provided in the sensor cell, and the outputs of the microphones 18 and 18'are monitored to determine the deterioration of the microphone and issue an alarm. It is different from the embodiment of 6. The description of the same components as those of the first to sixth embodiments will be omitted.

In FIG. 12, the sensor cell 14 is provided with a pair of the same microphones 18 and 18', and the outputs of the microphones 18 and 18'are input to the control circuit unit 23 via the detection circuit unit 24 and the signal processing unit 25. ing. The microcomputer of the control circuit unit 23 has a function of comparing the input outputs of the microphones 18 and 18'and determining the deterioration state of the microphones 18 and 18'.

Then, when the photoacoustic sensor 13 is activated, the intensities of the ambient environmental sounds measured by the microphones 18 and 18'are compared by the microcomputer of the control circuit unit 23, and the difference is stored in the memory 26.

When the difference stored in the memory 26 is larger than a predetermined difference threshold value (for example, the difference in intensity in the normal case), the microcomputer determines that the microphones 18 and 18'are deteriorated and gives an alarm. Is output. The alarm is transmitted to the air conditioner 10 and the central management device 12 via the communication unit 27, and can notify the deterioration of the photoacoustic sensor 13. Further, an alarm can be output by the blinking lamp 34 provided in the photoacoustic sensor 13.

As described above, in the case where the difference in the intensity of each acoustic wave measured by the pair of microphones deviates from a predetermined predetermined difference threshold value (for example, the difference in intensity in the normal case) in the microcomputer. Is equipped with an alarm generation function for generating an alarm.

In addition to the above-mentioned method, various methods can be considered for detecting that the microphone is deteriorated. For example, if there is a difference of 20% or more between the intensities that are the outputs of a pair of microphones, it is possible to issue an alarm that the microphones are deteriorated. Further, with respect to the intensity of the acoustic wave generated by the deteriorated microphone, the detected intensity can be corrected corresponding to the difference in intensity.

By executing the calibration method as described above, it becomes possible to accurately estimate the type of gas component without depending on the temperature. In addition, it is possible to notify the deterioration of the microphone of the photoacoustic sensor 13. Further, in the case where the concentration of the gas component is estimated from the intensity of the peak frequency as in the second embodiment, the deterioration of the microphone can be detected and the intensity of the acoustic wave can be corrected, so that the gas can be corrected. The estimation accuracy of the concentration of the component can be improved.

The present invention is not limited to some of the above-described embodiments, and includes various modifications. The above-mentioned examples have been described in detail in order to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the described configurations. Further, it is possible to replace a 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 configurations of each embodiment.

10 ... air conditioner, 11 ... sensor group, 12 ... central control device, 13 ... photoacoustic sensor, 14 ... sensor cell, 15 ... light source A, 16 ... light source B, 17 ... light source N, 18 ... microphone, 19 ... connection hole, 20 ... Drive circuit A, 21 ... Drive circuit B, 22 ... Drive circuit BN, 23 ... Control circuit unit, 24 ... Detection circuit unit, 25 ... Signal processing unit, 26 ... Memory, 27 ... Communication unit, 28 ... Air quality adjustment Device.

Claims (15)

A sensor cell that forms an internal space and stores the measured gas, a light source that irradiates the gas in the sensor cell with light, a light source driving means that causes the light source to emit light intermittently, and an acoustic wave of a specific gas in the sensor cell. Based on a microphone that detects a light source, a signal processing means that processes an acoustic wave detected by the microphone, a light source driving function that gives a driving signal to the light source driving means, and a signal from the signal processing means. Equipped with a control means to execute a gas estimation function that estimates the type of a specific gas,
The gas estimation function of the control means is characterized in that the average molecular weight of the specific gas is obtained by using the frequency of the acoustic wave and the temperature information of the gas, and the type of the specific gas is estimated from the obtained average molecular weight. Photoacoustic sensor. The photoacoustic sensor according to claim 1.
In the gas estimation function of the control means,
fr∝c = (κRT / M) ^1/2 (Here, “fr” is the frequency of the acoustic wave, “c” is the speed of sound proportional to the frequency fr, “κ” is the specific heat ratio of the gas, and “R”. Is the gas constant, "T" is the gas temperature, and "M" is the average molecular weight of the gas)
A photoacoustic sensor characterized in that the average molecular weight is obtained by using the frequency of the acoustic wave and the temperature information in the calculation formula obtained by transforming the calculation formula defined in the above into the calculation formula for obtaining the average molecular weight. The photoacoustic sensor according to claim 2.
In the gas estimation function of the control means,
A photoacoustic sensor characterized in that the type of the specific gas corresponding to the obtained average molecular weight is estimated from a table in which the relationship between the average molecular weight and the type of the specific gas is stored. The photoacoustic sensor according to claim 1.
In the light source driving function of the control means,
The drive frequency of the light source driving means is changed to make the light source emit light intermittently.
In the gas estimation function of the control means,
A photo-acoustic sensor characterized in that a peak frequency at which the output intensity of the acoustic wave detected by the microphone is maximized is searched for, and the peak frequency is used as the frequency of the acoustic wave for obtaining the average molecular weight. The photoacoustic sensor according to claim 4.
In the gas estimation function of the control means,
A photoacoustic sensor characterized in that the gas concentration of the specific gas is estimated from the intensity of the peak frequency of the acoustic wave. The photoacoustic sensor according to claim 1.
The temperature information of the gas is acquired from an externally provided temperature detection means via a communication means, or a circuit board on which the light source driving means, the signal processing means, and the control means are mounted. A photoacoustic sensor characterized by being acquired from a temperature measuring element provided in. The photoacoustic sensor according to claim 1.
The photoacoustic sensor is characterized in that the temperature information of the gas is based on set temperature information sent from the outside via a communication means. The photoacoustic sensor according to claim 1.
The light source includes a known gas light source for detecting a known gas component of the gas, and the light source driving means includes a known gas light source driving means for driving the known gas light source.
The photoacoustic sensor is characterized in that the temperature information of the gas is the temperature information obtained by the gas estimation function of the control means using the frequency of the acoustic wave and the average molecular weight of the known gas. .. The photoacoustic sensor according to claim 8.
In the gas estimation function of the control means,
fr∝c = (κRT / M) ^1/2 (Here, “fr” is the frequency of the acoustic wave, “c” is the speed of sound proportional to the frequency fr, “κ” is the specific heat ratio of the gas, and “R”. Is the gas constant, "T" is the gas temperature, and "M" is the average molecular weight of the gas)
A photoacoustic sensor characterized by obtaining the temperature information using the frequency of the acoustic wave and the average molecular weight, which is a calculation formula modified from the calculation formula defined in the above to the calculation formula for which the temperature information is obtained. The photoacoustic sensor according to claim 1.
The light source and the light source driving means have the same pair of the same light source and the same light source driving means, and a pair of current measuring means is provided between the pair of the light sources and the light source driving means. Ori,
The control means has an alarm generation function for generating an alarm when the difference between the average current values measured by the pair of current measuring means deviates from a predetermined difference threshold value. Have been
Alternatively, the microphone is provided with a pair of the same microphones.
The control means is provided with an alarm generation function for generating an alarm when the difference in the intensity of each of the acoustic waves measured by the pair of microphones deviates from a predetermined difference threshold value. A photoacoustic sensor characterized by being A sensor cell that forms an internal space and stores the measured gas, a light source that irradiates the gas in the sensor cell with light, a light source driving means that causes the light source to emit light intermittently, and an acoustic wave of a specific gas in the sensor cell. Based on a microphone that detects a light source, a signal processing means that processes the acoustic wave detected by the microphone, a light source driving function that gives a driving signal to the light source driving means, and a signal from the signal processing means. It is a calibration method of a photoacoustic sensor provided with a control means for executing a gas estimation function for estimating the type of the specific gas.
In the gas estimation function of the control means,
A step of obtaining the average molecular weight of the specific gas based on the frequency of the acoustic wave and the temperature information of the gas, and
A method for calibrating a photoacoustic sensor, which comprises performing a step of estimating the type of the specific gas from the obtained average molecular weight. The method for calibrating a photoacoustic sensor according to claim 11.
In the gas estimation function of the control means,
fr∝c = (κRT / M) ^1/2 (Here, “fr” is the frequency of the acoustic wave, “c” is the speed of sound proportional to the frequency fr, “κ” is the specific heat ratio of the gas, and “R”. Is the gas constant, "T" is the gas temperature, and "M" is the average molecular weight of the gas)
A photoacoustic formula obtained by transforming the calculation formula defined in the above into a calculation formula for obtaining the average molecular weight, wherein the step of obtaining the average molecular weight is executed using the frequency of the acoustic wave and the temperature information. How to calibrate the sensor. The method for calibrating a photoacoustic sensor according to claim 11.
In the light source driving function of the control means,
The step of changing the drive frequency of the light source driving means to make the light source emit light intermittently is executed.
In the gas estimation function of the control means,
Photoacoustic characterized by searching for a peak frequency at which the output intensity of the acoustic wave detected by the microphone is maximized and using the peak frequency as the frequency of the acoustic wave for obtaining the average molecular weight. How to calibrate the sensor. The method for calibrating a photoacoustic sensor according to claim 13.
In the gas estimation function of the control means,
A method for calibrating a photoacoustic sensor, which comprises performing a step of estimating a gas concentration of the specific gas from the intensity of the peak frequency of the acoustic wave. An air conditioning system for controlling the air quality of indoor air, which is the living environment of a building, wherein the air conditioning system includes a central control means, an air conditioning means controlled by the central control means, and an air quality adjusting means. The central control means is connected to a photoacoustic sensor that detects a gas component of the room air in order to control the air quality, and the central control means is the air conditioning means based on the output of the photoacoustic sensor. , And the air quality adjusting means, as well as
The air conditioning system, wherein the photoacoustic sensor is the photoacoustic sensor according to any one of claims 1 to 10.

Images