JP7438051B2 - Photoacoustic sensor, photoacoustic sensor calibration method, and air conditioning system - Google Patents

Description

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

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

In order to control this air quality, appropriate control of gas concentration and odor concentration is required, and a gas sensor that detects gas components and odor components depending on the purpose is required. Photoacoustic sensors using photoacoustic effects have been proposed as sensors for detecting gas components and odor components.

The photoacoustic effect occurs when the molecules of a specific component of a gas are intermittently (pulsed) irradiated with light of a specific wavelength, and the molecules that absorb the light thermally expand and contract, producing acoustic waves. This is a phenomenon in which (sound waves) are generated. Photoacoustic sensors are being used in building air conditioning systems because they are small and can detect low concentration gases with high sensitivity. Note that the photoacoustic sensor can be applied not only to air conditioning systems but also to other fields, and below, an application example of air conditioning systems will be explained.

A photoacoustic sensor encloses a measurement gas in a housing that forms a closed space called a cell, and irradiates it with pulsed light to generate an acoustic wave. The gas components are identified from the frequency). In a photoacoustic sensor used in an air conditioning system, at least one connection hole is formed in the cell in order to circulate air outside the cell (indoor air) into the cell.

However, the peak frequency of the acoustic waves generated by the photoacoustic effect tends to depend on the temperature of the measured gas, so if the indoor air temperature changes, there is a risk of errors in estimating the type of gas component. Therefore, it is required to compensate for temperature dependence.

As a technique to meet such demands, for example, in Japanese Patent Publication No. 2001-507798 (Patent Document 1), by using a gas whose type and concentration of gas components are known, correction of the concentration calculation of an unknown gas is made. has been shown to do so.

Special Publication No. 2001-507798

By the way, in Patent Document 1, the concentration calculation of an unknown gas is corrected by using a gas whose type and concentration are known, but if a known gas cannot be prepared, the estimation of the gas type and the gas These problems include the inability to measure the concentration of a component, and the problem that when a known gas leaks due to aging, the accuracy of estimating the type of gas and calculating the concentration of the gas component decreases. For this reason, the photoacoustic sensor as disclosed in Patent Document 1 requires known gas maintenance, and it is not a good idea to employ it in, for example, an air conditioning system.

The object of the present invention is to provide a novel photoacoustic sensor, a method for calibrating a photoacoustic sensor, and a method for calibrating a photoacoustic sensor, which can accurately estimate at least the type of gas component without using known gases or the like and without depending on temperature. Our goal is to provide air conditioning systems.

The present invention provides a sensor cell that forms an internal space and stores a gas to be measured, a light source that irradiates light to the gas in the sensor cell, a light source drive means that causes the light source to emit light intermittently, and an acoustic sensor for a specific gas in the sensor cell. a microphone for detecting waves; a signal processing means for signal-processing the acoustic waves detected by the microphone; at least a light source driving function for supplying a driving signal to the light source driving means; The gas estimation function of the control means calculates the average molecular weight of a specific gas using the frequency of the acoustic wave and the temperature information of the gas, and identifies the gas from the calculated 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 relying on temperature, without using known gases or the like. Note that problems, configurations, and effects other than those described above will be made clear by the following description of the mode for carrying out the invention.

1 is a system diagram of an air conditioning system to which the present invention is applied. It is an explanatory view explaining composition of a table which relates average molecular weight and gas component. FIG. 2 is a flowchart illustrating a gas component estimation method according to the first embodiment, which is executed in the air conditioning system shown in FIG. 1. FIG. FIG. 2 is a flowchart illustrating a gas component estimation method according to a second embodiment that is executed in the air conditioning system shown in FIG. 1. FIG. FIG. 2 is an explanatory diagram illustrating the configuration of a table that correlates the intensity of acoustic waves and the concentration of gas components. FIG. 2 is a flowchart illustrating a gas component estimation method according to a third embodiment that is executed in the air conditioning system shown in FIG. 1. FIG. FIG. 3 is a system diagram of an air conditioning system according to a fourth embodiment of the present invention. FIG. 8 is a flowchart illustrating a gas component estimation method according to a fourth embodiment that is executed in the air conditioning system shown in FIG. 7; FIG. 3 is a system diagram of an air conditioning system according to a fifth embodiment of the present invention. FIG. 10 is a flowchart illustrating a gas component estimation method according to a fifth embodiment that is executed in the air conditioning system shown in FIG. 9; FIG. 3 is a system diagram of an air conditioning system according to a sixth embodiment of the present invention. FIG. 7 is a system diagram of an air conditioning system according to a seventh embodiment of the present invention.

Embodiments of the present invention will be described below with reference to the drawings. The embodiments are examples for explaining the present invention, and are omitted and simplified as appropriate for clarity of explanation. The present invention can also be implemented in various other forms.

First, a 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 gas component estimation method according to the first embodiment, which is executed in the air conditioning system shown in FIG. ing.

In the air conditioning system shown in FIG. 1, an air conditioner (air conditioning means) 10 has a function of receiving sensor information from a sensor group 11 and performing an air conditioning operation based on this received signal. The sensor group 11 includes environmental sensors such as a temperature sensor (temperature detection means) that detects the temperature of the living space, a CO ₂ sensor that detects the CO ₂ concentration of the living space, and a dust sensor that detects dust floating in the living space; It consists 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.

Furthermore, the air conditioner 10 is connected wirelessly or wired to a central management device (central management means) 12 composed of a server, etc., and the air conditioner 10 transmits operating information, sensor information, etc. to the central management device 12. are doing. Furthermore, the central management device 12 transmits operation signals and control signals for the air conditioner 10 to the air conditioner 10.

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

The photoacoustic sensor 13 includes at least a sensor cell 14 that forms an internal space and stores a gas to be measured (here, air), a light source A15 to a light source N17 that irradiates light to the gas (air) in this sensor cell 14, and a sensor cell. The sensor cell 14 includes a microphone 18 that detects acoustic waves in the air within the sensor cell 14, and at least two connection holes 19 that connect an internal space and an external space within the sensor cell 14. The two connection holes 19 are provided to circulate air within the sensor cell 14 as described above.

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

The wavelength of the light emitted from the light sources A15 to N17 is determined by the specific gas component to be measured, and in this embodiment, the N light sources A15 to N17 are used to detect N gas components. It is equipped. Since this embodiment uses LEDs, a desired wavelength is obtained by using an optical filter that transmits a predetermined wavelength.

Since the light source A15 to light source N17 emit light intermittently to give light energy to the air stored in the sensor cell 14, the light source A15 to light source N17 emit light in a pulsed manner by the drive circuit (light source drive means) A20 to the drive circuit (light source drive means) N22. Light emission is controlled. Further, the drive circuit A20 to N22 control the frequency to be changed (swept) within a predetermined range in order to find (search) the peak frequency at which the intensity of the acoustic wave detected by the microphone 18 is maximum. be done.

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

For example, at least the function of changing the frequencies of the drive circuits A20 to N22 described above (light source drive function), the function of determining the type and concentration of gas components from acoustic waves (gas estimation function), etc. are executed. A method for determining the type and concentration of gas components from acoustic waves will be described later.

Note that although the drive circuit A20 and light source A15 will be described below, the other drive circuits B21 to N22 and light sources B16 to N17 perform similar operations.

The acoustic waves generated by the intermittent light emission of the light source A15, which are detected by the microphone 18, are converted into electrical signals by the detection circuit section 24, and then noise is removed by the signal processing section (signal processing means) 25. The signal is amplified and transmitted to the control circuit section 23. The control circuit section 23 determines the drive frequency of the drive circuit A20 that produces the peak frequency from the peak frequency at which the intensity of the acoustic wave becomes maximum.

In other words, since the emission frequency of the light source A15 and the frequency of the acoustic wave almost match, the driving frequency of the driving circuit A20 is determined in order to obtain a more accurate frequency. Since this driving frequency is generated by the control circuit section 23, it is sufficient to find this driving frequency. The peak frequency and intensity at which the intensity of this acoustic wave is maximum are temporarily stored in the memory (storage means) 26. The memory 26 is a rewritable memory, and may be a battery-backed RAM, a flash ROM, a microcomputer RAM, or the like.

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

Note that many of the air conditioners 10 are equipped with a temperature sensor for controlling themselves, and the temperature sensor of the air conditioner 10 can also 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 by the photoacoustic sensor 13 or at every predetermined period.

On the other hand, the gas components and their concentrations determined 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 management device 12 controls the air conditioner 10 and air quality adjustment devices (air quality adjustment means) such as an odor adsorption device, a dust collector, an ozone deodorization device, and an aroma adding device in accordance with the sent gas components and their concentrations. )28. Note that the air conditioner 10 can also have the function of the air quality adjustment device 28.

Then, in the control circuit section 23, the average molecular weight of the specific gas component to be measured is determined from the drive frequency of the drive circuit A20 and the air temperature information stored in the memory 26, and the specific gas component is determined from the determined average molecular weight. Executes an operation to estimate the type of . Specifically, a microcomputer executes the calculations shown below to determine the average molecular weight.

The resonance frequency (fr) of the acoustic wave of the sensor cell 14 can be expressed by the following equation (1). In gases, the speed of sound generally depends on the specific heat ratio, average molecular weight, and temperature. Here, "c" is the speed of sound, "κ" is the specific heat ratio of the gas stored in the sensor cell 14, "R" is the gas constant of the gas stored in the sensor cell 14, and "T" is the gas stored in the sensor cell 14. If we define the gas temperature of the gas "M" as the average molecular weight of the specific gas stored in the sensor cell 14, then the sound velocity (c), which is proportional to the resonance frequency (fr), 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 this via a duct, "fr∝c" is
fr=cd/4π・((π(V1+V2)/LV1V2)) ^1/2 ...(2)
It is expressed as Here, "d" is the duct diameter, "L" is the duct length, "V1" is the detection cell volume, and "V2" is the resonance cell volume.

Note that the values other than the sound velocity (c) on the right side can be treated as coefficients, which can be determined 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 equation (2). Furthermore, in order to obtain the average molecular weight (M), equation (1) is transformed into a "predetermined calculation equation" (M = κRT/c ² ), and the sound velocity (c) and temperature (T) are substituted into this to calculate the average molecular weight (M). Molecular weight (M) can be determined.

Note that formula (2) shows the case where the sensor cell 14 is a combination of a detection cell and a resonance cell, but there are also cases where the sensor cell 14 is only a detection cell, a case where there are two resonance cells, etc. In this case, the coefficient part of equation (2) may be modified accordingly, and the point is that the speed of sound (c) may be found from the resonance frequency (fr).

In this manner, in this embodiment, the average molecular weight (M) is determined from the driving frequency (fr) of the light source corresponding to the resonance frequency and the temperature information (T) of the air, which are stored in the memory 26. In other words, the above-mentioned formula (1) is transformed into a "predetermined calculation formula" that calculates the average molecular weight (M), and the driving frequency (f _r ) and air temperature information (T) are used from this predetermined calculation formula. The average molecular weight (M) with temperature dependence compensated for can be determined by

Then, the type of gas component is estimated from the obtained average molecular weight (M). For example, as shown in FIG. 2, the estimation method is to create a table of gas components A to N and their corresponding average molecular weights A to N, and then search for the corresponding gas component from the obtained average molecular weight (M). Thus, 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 temperature. Note that in this embodiment, the concentration of gas components is not estimated. A method for estimating the concentration of gas components will be explained in Example 2 below.

Next, a specific control flow executed by the microcomputer of the control circuit section 23 will be explained based on FIG. 3. The control flow shown in FIG. 3 is activated by a temporal interrupt, and is executed, for example, by the occurrence of an interrupt by a compare match timer. Here, steps after step S11 are control steps executed by the microcomputer of the control circuit unit 23.

<<Step S10>>
In step S10, temperature information is detected by the air conditioner 10 or the temperature sensor of the sensor group 11. Temperature information from this temperature sensor represents the average air temperature of the air circulating indoors. The reason for determining the average air temperature is to avoid detecting temporary temperature changes and to avoid errors in calculating the average molecular weight (M). Once the temperature information is obtained, the process moves to step S11.

<<Step S11>>
In step S11, the temperature information obtained in step S10 is taken in via the communication section 27 of the photoacoustic sensor 13, and this received temperature information is stored in a predetermined area of the memory 26. The stored temperature information is retained at least until the gas components described below are determined. Once the temperature information is stored, the process moves to step S12.

<<Step S12>>
In step S12, it is determined whether the operations of the drive circuits A20 to N22 that drive the light sources A15 to N17 have been completed. In other words, the operations of the drive circuits A20 to N22 are executed in order, and the detection of acoustic waves is performed accordingly, so the completion of the operations of the drive circuits A20 to N22 means that the detection of acoustic waves is This means that the estimation of gas components has been completed.

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

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

<<Step S13>>
In step S13, the driving frequency of the driving circuit A20 is changed (swept) at a constant speed, and the acoustic waves are measured by the microphone 18. While 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.

Note that since the driving frequency of the driving circuit A20 and the peak frequency of the acoustic wave substantially correspond to each other, the driving frequency of the driving circuit A20 at this time is determined as the peak frequency. Once the peak frequency is determined, the process moves 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 held at least until the gas component described later is determined. Once the peak frequency is stored, the process moves to step S15.

<<Step S15>>
In step S15, the average molecular weight (M) is calculated using the temperature information and peak frequency stored in the memory 26. Specifically, by transforming the above-mentioned equation (1) into a "predetermined calculation formula" that calculates the average molecular weight (M), and using the peak frequency and temperature information in this predetermined calculation formula, the temperature dependence can be calculated. The average molecular weight (M) can be determined. Once the average molecular weight (M) is determined, the process moves to step S16.

<<Step S16>>
In step S16, the type of gas component is estimated from the average molecular weight (M) determined in step S15. As mentioned above, this estimation can be done by creating a table of gas components A to N and their corresponding average molecular weights A to N, and then looking up the corresponding gas component 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 gas components has been completed, the flow exits to "END" and the processing of this control flow is terminated. On the other hand, estimation of gas components by other operations of the drive circuit B21 to N22 can be performed by executing steps S13 to S16 described above.

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

Next, a second embodiment of the present invention will be described based on FIG. 4. This embodiment differs from the first embodiment in that the concentration of the gas component is determined from the intensity of the peak frequency. Note that explanations of control steps that are the same as those shown in FIG. 3 will be omitted. Here, the air conditioning system of this 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 the generation of an interrupt by a compare match timer. Here, steps after step S11 are control steps executed by the microcomputer of the control circuit unit 23.

≪Step S10≫ ~ ≪Step S13≫
The control steps from step S10 to step S13 are the same as the control steps shown in FIG. 3, so a description thereof will be omitted. Then, after executing up to step S13, the process moves 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 components described below are determined. Once the peak frequency is stored, the process moves to step S15.

≪Step S15≫ ~ ≪Step S16≫
The control steps from step S15 to step S16 are the same as the control steps shown in FIG. 3, so a description thereof will be omitted. After steps S15 and S16 are executed, the process moves to step S17.

<<Step S17>>
In step S17, the concentration of the gas component is estimated from the intensity of the acoustic wave determined in step S14A. This concentration can be estimated by making a table of the acoustic wave intensity and its corresponding concentration, and then looking up the concentration of the corresponding gas component from the determined intensity. 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 is determined based on the intensity of the acoustic wave. Therefore, the relationships shown in FIG. 5 may be made into a table. 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 have been completed, the flow exits to "END" and the processing of this control flow ends. On the other hand, the estimation of the type of gas component and the estimation of the concentration by the operation of the drive circuit B21 to N22 other than this can be performed by executing steps S13 to S17 described above.

By performing the calibration method described above, it is possible to accurately estimate the type of gas component without depending on temperature, and it is also 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 based on FIG. 6. This embodiment differs from the first and second embodiments in that the gas components are estimated after the indoor air temperature is stabilized by the air conditioner 10. Note that explanations of control steps that are the same as those of the first embodiment and the second embodiment will be omitted. Here, the air conditioning system of this 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 the occurrence of an interrupt by a compare match timer. Here, steps after step S11 are control steps executed by the microcomputer of the control circuit unit 23.

≪Step S20≫
In step S20, desired temperature setting information is transmitted from the central management device 12 to the air conditioner 10. The air conditioner 10 starts operating based on this set temperature information and continues to operate so that the indoor air approaches the set temperature. While the air conditioner 10 continues to operate, the process moves to step S21.

<<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 adjusts the settings set for 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 moves to step S11.

≪Step S1≫ ~ ≪Step S16≫
The control steps from step S11 to step S16 are the same as the control steps shown in FIG. 3, so a description thereof will be omitted.

Then, when it is determined that the estimation of the type of gas component is completed, the flow exits to "END" and the processing of this control flow is terminated. On the other hand, the types of gas components can be estimated by the operations of the drive circuits B21 to N22 other than this by executing steps S13 to S16 described above.

By performing the above-described calibration method, it becomes possible to accurately estimate the type of gas component without depending on temperature. Furthermore, by using the function of the air conditioner to control the indoor air temperature to a set temperature, it is possible to simplify the configuration of the sensor group. Note that, as in the second embodiment, it is also possible to adopt a configuration in which the concentration of the gas component is estimated from the intensity of the peak frequency.

Next, a fourth embodiment of the present invention will be described based on FIGS. 7 and 8. This embodiment differs from the first to third embodiments in that the photoacoustic sensor 13 is equipped with a temperature measurement function section 29. Note that descriptions of the same components as those in the first to third embodiments and the same control steps as those shown in the first to third embodiments will be omitted.

In FIG. 7 , the photoacoustic sensor 13 includes a temperature measurement function section 29 , and this temperature measurement function section 29 transmits temperature information to the control circuit section 23 . The temperature measuring function section 29 can use a temperature measuring element such as a temperature sensor (temperature measuring resistor or thermistor) provided on the circuit board of the photoacoustic sensor 13 or a thermopile. Drive circuits 20 to 22, a detection circuit section 24, a signal processing circuit 25, a control circuit section 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 explained based on FIG. 8. The air conditioning system of this embodiment is basically the same as the system shown in FIG. 1 except that 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 the generation of an interrupt by a compare match timer. Here, steps after step S22 are control steps executed by the microcomputer of the control circuit section 23.

<<Step S22>>
In step S22, the temperature measurement function section 29 using a temperature measurement element provided on the circuit board of the photoacoustic sensor 13 detects the temperature, 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 components described below are determined. Once the temperature information is stored, the process moves to step S12.

≪Step S12≫ ~ ≪Step S16≫
The control steps from step S12 to step S16 are the same as the control steps shown in FIG. 3, so a description thereof will be omitted.

Then, when it is determined that the estimation of the type of gas component is completed, the flow exits to "END" and the processing of this control flow is terminated. On the other hand, the types of gas components can be estimated by the operations of the drive circuits B21 to N22 other than this by executing steps S12 to S16 described above.

By performing the above-described calibration method, it becomes possible to accurately estimate the type of gas component without depending on temperature. Further, even in a state where temperature information cannot be obtained from the air conditioner 10 side, the type of gas component can be estimated using only the photoacoustic sensor 13. Note that, as in the second embodiment, it is also possible to adopt a configuration in which the concentration of the gas component is estimated from the intensity of the peak frequency.

Next, a fifth embodiment of the present invention will be described based on FIGS. 9 and 10. This embodiment differs from the first to fourth embodiments in that it is equipped with a light source Q30 for measuring a known gas. Note that descriptions of the same components as those in the first embodiment to the fourth embodiment and the same control steps as those shown in the first embodiment to the fourth embodiment will be omitted.

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

Next, a specific control flow executed by the microcomputer of the control circuit section 23 will be explained based on FIG. The air conditioning system of this embodiment is basically the same as the system shown in FIG. 1, except that temperature information is calculated.

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

<<Step S23>>
In step S23, the driving frequency of the driving circuit Q30 is changed (swept) at a constant speed, and the acoustic waves are measured by the microphone 18. While continuing to drive the drive circuit Q30, the process moves 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 becomes the frequency at which the gas component of the known gas reacts most. When the peak frequency is detected, the temperature is calculated using equation (1).

This calculation calculates the temperature (T) from the known average molecular weight (M) of the gas and the sound velocity (c) determined from the peak frequency. As mentioned above, the speed of sound (c) can be found from equation (2), so transform equation (1) above into a "predetermined calculation equation" (T=c ² M/κR) that allows temperature (T) to be found. By substituting the sound velocity (c) and the average molecular weight (M) into this predetermined arithmetic expression, the temperature (T) can be determined.

In other words, the above-mentioned equation (1) is transformed into a "predetermined arithmetic expression" for calculating the temperature (T), and from this predetermined arithmetic expression, the driving frequency (fr) of the light source and the average molecular weight (M) are used to calculate the temperature. (T) can be found. Once the temperature (T) is determined, this temperature information is stored in a predetermined area of the memory 26. The stored temperature information is retained at least until the gas components described below are determined. Once the temperature information is stored, the process moves to step S12.

≪Step S12≫ ~ ≪Step S16≫
The control steps from step S12 to step S16 are the same as the control steps shown in FIG. 3, so a description thereof will be omitted.

Then, when it is determined that the estimation of the type of gas component is completed, the flow exits to "END" and the processing of this control flow is terminated. On the other hand, the types of gas components can be estimated by the operations of the drive circuits B21 to N22 other than this by executing steps S12 to S16 described above.

By performing the above-described calibration method, it becomes possible to accurately estimate the type of gas component without depending on temperature. Furthermore, it is possible to estimate the type of gas component using only the photoacoustic sensor without using a temperature sensor. Note that, as in the second embodiment, it is also possible to adopt a configuration in which the concentration of the gas component is estimated from the intensity of the peak frequency.

Next, a sixth embodiment of the present invention will be described based on FIG. 11. In this embodiment, a pair of light sources with the same wavelength is provided, and a current measuring circuit monitors the average current value of the drive circuit connected to each light source to determine deterioration of the light source and issue an alarm. This embodiment is different from the fifth embodiment. Note that explanations of the same constituent elements 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'15' having the same wavelength, and a drive circuit A20 and a drive circuit A'20' that drive the light sources are provided. A current measurement circuit A32 and a current measurement circuit A'32' are interposed between these. Therefore, the current measurement circuit A32 and the current measurement 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 paired light sources and drive circuits, and are also provided with corresponding current measurement circuits. FIG. 11 shows a light source N'17', a drive circuit N22' that drives the light source, and a current measurement circuit N'33'.

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

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

In this way, the microcomputer has a problem in which the difference between the respective average current values measured by a pair of current measurement circuits deviates from a predetermined difference threshold (the difference between the average current values in a normal case). In some cases, an alarm generation function is provided to generate an alarm.

In addition to the above-mentioned method, various methods can be used to detect the deterioration of the light source including the drive circuit. For example, if there is a difference of 20% or more between the average current values of a pair of drive circuits, a warning may be issued because the light source including the drive circuits has deteriorated. Furthermore, the intensity of the acoustic wave caused by the degraded light source can be corrected in accordance with the difference in average current value.

By performing the above-described calibration method, it becomes possible to accurately estimate the type of gas component without depending on temperature. Further, deterioration of the light source of the photoacoustic sensor 13 can be notified. Furthermore, when the concentration of the gas component is estimated from the intensity of the peak frequency as in the second embodiment, the intensity of the acoustic wave can be corrected by detecting deterioration of the light source. The accuracy of estimating the concentration of components can be improved.

Next, a seventh embodiment of the present invention will be described based on FIG. 12. This embodiment is different from the first to third embodiments in that a pair of microphones 18, 18' is provided in the sensor cell, and the output of each microphone 18, 18' is monitored to determine the deterioration of the microphone and issue an alarm. This embodiment is different from the embodiment No.6. Note that explanations of the same constituent elements as those of the first to sixth embodiments will be omitted.

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

Then, when the photoacoustic sensor 13 is activated, the microcomputer of the control circuit section 23 compares the intensities of the surrounding environmental sounds measured by the respective microphones 18 and 18', and stores the difference in the memory 26.

If the difference stored in the memory 26 is larger than a predetermined difference threshold (for example, the difference in intensity in a normal case), the microcomputer determines that the microphones 18 and 18' have deteriorated, and issues an alarm. Output. The alarm can be sent to the air conditioner 10 and the central management device 12 via the communication unit 27 to notify the deterioration of the photoacoustic sensor 13. Furthermore, a flashing lamp 34 provided on the photoacoustic sensor 13 can also output an alarm.

In this way, if the difference in the intensity of each acoustic wave measured by a pair of microphones deviates from a predetermined difference threshold (for example, the difference in intensity in a normal case), the microcomputer can is equipped with an alarm generation function that generates an alarm.

In addition to the above-mentioned method, various methods can be used to detect that the microphone has deteriorated. For example, if there is a difference of 20% or more between the intensities of the outputs of a pair of microphones, a warning may be issued indicating that the microphones have deteriorated. Furthermore, regarding the intensity of the acoustic waves generated by the degraded microphone, the detected intensity can be corrected in accordance with the difference in intensity.

By performing the above-described calibration method, it becomes possible to accurately estimate the type of gas component without depending on temperature. Further, deterioration of the microphone of the photoacoustic sensor 13 can be notified. Furthermore, when the concentration of the gas component is estimated from the intensity of the peak frequency as in the second embodiment, it is possible to detect the deterioration of the microphone and correct the intensity of the acoustic wave. The accuracy of estimating the concentration of components can be improved.

Note that the present invention is not limited to the several embodiments described above, and includes various modifications. The above-mentioned embodiments have been described in detail to explain the present invention in an easy-to-understand manner, and the present invention is not necessarily limited to having all the configurations described. Furthermore, 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 configuration of each embodiment.

10...Air conditioner, 11...Sensor group, 12...Central management 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 section, 24... Detection circuit section, 25... Signal processing section, 26... Memory, 27... Communication section, 28... Air quality adjustment Device.

Claims (10)

a sensor cell that forms an internal space and stores a gas to be measured; a light source that irradiates light to the gas in the sensor cell; a light source drive unit that causes the light source to emit light intermittently; a microphone that detects waves, a signal processing means that processes the acoustic waves detected by the microphone, at least a light source driving function that provides a driving signal to the light source driving means, and a signal processing means based on the signal from the signal processing means. comprising a control means for executing a gas estimation function for estimating the type of the specific gas,
The gas estimation function of the control means determines the average molecular weight of the specific gas using the frequency of the acoustic wave and the temperature information of the gas, and estimates the type of the specific gas from the determined average molecular weight. There it is,
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 sound velocity which is proportional to the frequency fr, "κ" is the specific heat ratio of the gas, "R" is the gas constant of the gas, "T" is the gas temperature of the gas, and "M" is the average molecular weight of the specific gas)
Calculating the average molecular weight using the frequency of the acoustic wave and the temperature information using an arithmetic expression that is modified from the arithmetic expression defined in
In the gas estimation function of the control means,
A photoacoustic sensor characterized in that the type of the specific gas corresponding to the determined average molecular weight is estimated from a table in which a 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,
changing the driving frequency of the light source driving means to cause the light source to emit light intermittently;
In the gas estimation function of the control means,
Searching for a peak frequency at which the output intensity of the acoustic wave detected by the microphone is maximum, and using the peak frequency as the frequency of the acoustic wave for determining the average molecular weight.
A photoacoustic sensor characterized by: The photoacoustic sensor according to claim 2,
In the gas estimation function of the control means,
Estimating the gas concentration of the specific gas from the intensity of the peak frequency of the acoustic wave.
A photoacoustic sensor characterized by: The photoacoustic sensor according to claim 1,
The temperature information of the gas is obtained from an external 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. The temperature is obtained from the temperature measuring element installed in
A photoacoustic sensor characterized by: The photoacoustic sensor according to claim 1,
The temperature information of the gas is based on set temperature information sent from the outside via a communication means.
A photoacoustic sensor characterized by: a sensor cell that forms an internal space and stores a gas to be measured; a light source that irradiates light to the gas in the sensor cell; a light source drive unit that causes the light source to emit light intermittently; a microphone that detects waves, a signal processing means that processes the acoustic waves detected by the microphone, at least a light source driving function that provides a driving signal to the light source driving means, and a signal processing means based on the signal from the signal processing means. control means for executing a gas estimation function of estimating the type of the specific gas,
The gas estimation function of the control means determines the average molecular weight of the specific gas using the frequency of the acoustic wave and the temperature information of the gas, and estimates the type of the specific gas from the determined average molecular weight. hand,
The light source includes a known gas light source for detecting a gas component of the known gas, and the light source driving means includes a known gas light source driving means for driving the known gas light source,
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 known average molecular weight of the gas.
A photoacoustic sensor characterized by: The photoacoustic sensor according to claim 6,
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 sound speed proportional to the frequency fr, "κ" is the specific heat ratio of the gas, "R" is the gas constant of the gas, "T" is the gas temperature of the gas, and "M" is the average molecular weight of the gas)
Calculate the temperature information using the frequency of the acoustic wave and the average molecular weight using an arithmetic expression that is modified from the arithmetic expression defined in .
A photoacoustic sensor characterized by: a sensor cell that forms an internal space and stores a gas to be measured; a light source that irradiates light to the gas in the sensor cell; a light source drive unit that causes the light source to emit light intermittently; a microphone that detects waves, a signal processing means that processes the acoustic waves detected by the microphone, at least a light source driving function that provides a driving signal to the light source driving means, and a signal processing means based on the signal from the signal processing means. control means for executing a gas estimation function of estimating the type of the specific gas,
The gas estimation function of the control means determines the average molecular weight of the specific gas using the frequency of the acoustic wave and the temperature information of the gas, and estimates the type of the specific gas from the determined average molecular weight. hand,
The light source and the light source driving means have a 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 is configured to calculate the difference between the respective average current values measured by the pair of current measurement means.
It is equipped with an alarm generation function that generates an alarm if the difference deviates from a predetermined difference threshold.
Alternatively, the microphone is provided with a pair of the same microphones,
The control means includes an alarm generation function that generates an alarm when a difference in the intensity of the acoustic waves measured by the pair of microphones deviates from a predetermined difference threshold. being given
A photoacoustic sensor characterized by: a sensor cell that forms an internal space and stores a gas to be measured; a light source that irradiates light to the gas in the sensor cell; a light source drive unit that causes the light source to emit light intermittently; a microphone that detects waves, a signal processing means that processes the acoustic waves detected by the microphone, at least a light source driving function that provides a driving signal to the light source driving means, and a signal processing means based on the signal from the signal processing means. A method for calibrating a photoacoustic sensor, comprising a control means for executing a gas estimation function of estimating the type of the specific gas, the method comprising:
In the gas estimation function of the control means,
determining an average molecular weight of the specific gas based on the frequency of the acoustic wave and the temperature information of the gas;
performing a step of estimating the type of the specific gas from the determined average molecular weight;
Furthermore, 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 sound velocity which is proportional to the frequency fr, "κ" is the specific heat ratio of the gas, "R" is the gas constant of the gas, "T" is the gas temperature of the gas, and "M" is the average molecular weight of the specific gas)
calculating the average molecular weight using the frequency of the acoustic wave and the temperature information using a calculation formula that is modified from the calculation formula defined in
In the light source driving function of the control means,
changing the driving frequency of the light source driving means to cause the light source to emit light intermittently;
In the gas estimation function of the control means,
searching for a peak frequency at which the output intensity of the acoustic wave detected by the microphone is maximum, and using the peak frequency as the frequency of the acoustic wave for determining the average molecular weight;
In the gas estimation function of the control means,
A method for calibrating a photoacoustic sensor, comprising: 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 that is a living environment of a building, the air conditioning system comprising a central management means, an air conditioning means controlled by the central management means, and an air quality adjustment means. , the central management means is connected to a photoacoustic sensor that detects gas components of the indoor air to control the air quality, and the central management means controls the air conditioning means based on the output of the photoacoustic sensor. , and controlling the air quality regulating means,
The photoacoustic sensor is the photoacoustic sensor according to any one of claims 1 to 8.
An air conditioning system characterized by:

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