JP2014219211A - Non-dispersive infrared analytical gas detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a non-dispersive infrared analytical gas detector capable of suppressing a deterioration of gas detection accuracy due to an influence of heater heating when a specified gas contained in an object gas to be measured is detected in an atmosphere of high humidity.SOLUTION: In a non-dispersive infrared analytical gas detector 1, an infrared detection element 31 of an infrared sensor 15 detects a gas (carbon dioxide) corresponding to the infrared of a detection wavelength based on intensity of the infrared received by a detection contact 61 while a reference contact 62 is used as a reference. The reference contact 62 is hardly affected by heat conduction as a result of being provided on a reference thin film part 44 instead of a flame part 41 of an infrared detection element 31. Consequently, the infrared detection element 31 can suppress a deterioration of gas detection accuracy because a fluctuation of a sensor output caused by a temperature change of the reference contact 62 by the heat conduction from a heater 17 is hardly generated.

Description

  The present invention relates to a non-dispersive infrared analytical gas detector that detects a specific gas contained in a gas to be measured.

Conventionally, a non-dispersive infrared analysis type (NDIR type) gas detector that detects a specific gas in an atmosphere is known.
The non-dispersive infrared analytical gas detector uses the characteristic that gas molecules absorb infrared rays of a specific wavelength, and it is specified by measuring the infrared intensity of this specific wavelength for the infrared rays that have passed through the measurement target gas. It detects gas.

  The components of the non-dispersive infrared analytical gas detector are roughly divided into a light source, a measurement cell (barrel), a wavelength selection filter (bandpass filter), and a light receiver (infrared sensor). Among these, the measurement cell generally serves as a lens barrel that delivers infrared rays emitted from a light source to an infrared sensor (Patent Document 1).

  By the way, when such a gas detector is used in a high humidity atmosphere, the reflectance of infrared light may be significantly reduced due to the formation of condensation on the inner wall surface of the measurement cell (lens barrel), which may cause false detection. is there. Examples of the case where such condensation occurs include an application for detecting a specific gas contained in a person's breath.

  As a gas detector for such a problem, there is one having a heater for heating a measurement cell (Patent Document 2). This non-dispersive infrared analytical gas detector is configured to suppress dew condensation on the inner wall surface of the measurement cell by heating the measurement cell with a heater.

  In addition, dew condensation may occur not only on the measurement cell but also on the surface of the light receiving unit (infrared sensor) (particularly, a window unit for receiving infrared rays). In such a gas detector, heat conduction from the heater is also conducted to the light receiving part (infrared sensor) through the measurement cell, and not only the measurement cell but also the light receiving part (infrared sensor) is heated, thereby causing condensation. Occurrence can be suppressed.

  On the other hand, an infrared detector using a thermopile as an infrared sensor is known (Patent Document 3). In Patent Document 3, in order to solve the problem that the offset voltage is generated in the thermopile due to the temperature rise of the thin film portion due to infrared rays received from other than the object to be measured, the first thin film portion is provided with a hot junction and the second thin film. An infrared detecting device having a cold junction in the part has been proposed. Patent Document 3 does not describe a heater, and this infrared detection device is used for detecting infrared rays without providing a heater.

JP 2004-138499 A International Publication No. 2010/085557 Japanese Patent No. 3101190

  However, in the configuration in which not only the measurement cell but also the light receiving part (infrared sensor) is heated by the heater, a MEMS type (micro electromechanical element type) thermopile or MEMS type focus is used as the infrared detecting element of the light receiving part (infrared sensor). When an electric sensor is used, the detection result (output signal) of the light receiving unit (infrared sensor) may fluctuate due to a rapid temperature change due to the effect of heater heating.

  For example, a MEMS thermopile is configured to generate an electromotive force due to a temperature difference between a hot junction formed on a thin film portion (membrane) and a cold junction formed on a frame portion (rim). Since the heat conduction speeds to the hot junction are different from each other, the temperature difference between the cold junction and the hot junction is temporarily shifted, and as a result, the detection result (infrared detection signal) may fluctuate. As a result, there is a possibility that the MEMS thermopile cannot correctly measure the intensity of incident infrared rays.

Here, the structure of a conventional MEMS thermopile will be briefly described with reference to FIGS.
In the infrared detecting element 931 as a conventional MEMS thermopile, the frame portion 941 (cold contact 949) is in thermal contact with a pedestal (not shown), while the thin film portion 943 (hot contact 948) is pedestal. And a thermal isolation from the cold junction 949 of the thermoelectric stacking part 945. An infrared absorption layer 947 is formed on the hot contact point 948 of the thermopile unit 945. When the infrared absorption layer 947 is irradiated with infrared rays from the outside, the temperature of the infrared absorption layer 947 changes, and the cold junction 949 is changed. And a temperature difference (ΔT) occurs at the hot junction 948. Since the infrared detection element 931 (thermopile) generates an electromotive force (ΔV) according to the temperature difference (ΔT), the infrared intensity (I) can be obtained by using this electromotive force. The infrared detection element 931 outputs an infrared detection signal corresponding to the electromotive force ΔV from the two electrode pads 950 to the outside.

  Here, when the measurement cell (lens) and the infrared sensor are heated by the heater for preventing condensation as described above, the frame portion 941 (cold junction 949) of the infrared detection element 931 (MEMS type thermopile) Heated through a heat transfer path through the pedestal. Therefore, the frame portion 941 (cold junction 949) that is in thermal contact with the pedestal has a stronger thermal connection with the ambient temperature than the thin film portion 943 (hot junction 948), and responds quickly to changes in the ambient temperature. . As a result, a phenomenon occurs in which the temperature difference between the cold junction 949 and the warm junction 948 is temporarily shifted, and the detection result (infrared detection signal) fluctuates. That is, since a temperature difference (ΔT) occurs due to an influence other than the incidence of infrared rays, the intensity of incident infrared rays may not be measured temporarily.

  In addition, as described in Patent Document 3, it is possible to eliminate such a problem by adopting a configuration that does not include a heater, but erroneous detection in an atmosphere with high humidity as described above occurs. There is a fear.

  Therefore, the present invention provides a non-dispersive infrared analytical gas detector capable of suppressing a decrease in gas detection accuracy due to the effect of heater heating when detecting a specific gas contained in a measurement target gas in a high humidity atmosphere. With the goal.

  The non-dispersive infrared analytical gas detector of the present invention is a non-dispersive infrared analytical gas detector that detects a specific gas contained in a measurement target gas, and includes a light source that emits infrared rays and a measurement target gas inside. A measurement cell, an infrared sensor that outputs an infrared detection signal corresponding to the intensity of the infrared light that has reached, and a heater that heats the measurement cell.

Among these, the light source and the infrared sensor are connected in a state of being thermally conducted to the measurement cell.
The infrared sensor has a frame portion that surrounds each of the plurality of thin film portions, and also has a detection element having a thin film portion and a thermopile disposed in the frame portion, and infrared rays having a predetermined wavelength according to each of the plurality of thin film portions. A wavelength selective filter that transmits the light.

The sensing element includes at least one reference thin film portion and at least one sensing thin film portion as a plurality of thin film portions.
The wavelength selection filter transmits infrared light having a reference wavelength to the reference thin film portion, and transmits infrared light having a detection wavelength to the detection thin film portion.

The thermopile has a configuration in which a plurality of reference contacts provided in the reference thin film portion and a plurality of detection contacts provided in the detection thin film portion are alternately connected.
The infrared sensor having such a configuration can detect a specific gas of a type corresponding to infrared rays having a detection wavelength based on the intensity of infrared rays received by the detection contact while using the reference contact as a reference.

  And since a reference contact is provided not in the frame part of a detection element but in a thin film part (reference thin film part), it becomes difficult to receive the influence of the heat conduction from the frame part of a detection element. As a result, the sensor output is less likely to fluctuate due to the temperature change of the reference contact due to the heat conduction from the heater, and the deterioration of the gas detection accuracy can be suppressed.

  In addition, since the thermopile has a plurality of reference contacts and a plurality of detection contacts, it has the same configuration as that of a plurality of thermopiles of the minimum configuration consisting of one reference contact and one detection contact, and is connected to an infrared sensor. A large output can be secured. By ensuring a large sensor output of the infrared sensor in this way, it is possible to reduce the influence of noise and suppress a decrease in gas detection accuracy.

Furthermore, since this invention can suppress that the inner wall face of a measurement cell condenses by providing the heater which heats a measurement cell, it can suppress the misdetection resulting from condensation.
Therefore, according to the present invention, when detecting the specific gas contained in the measurement target gas in a high humidity atmosphere, it is possible to suppress a decrease in gas detection accuracy due to the influence of heater heating.

  Next, in the non-dispersive infrared analytical gas detector of the present invention, the plurality of reference contacts are arranged radially from the center to the end of the reference thin film portion, and the plurality of detection contacts are detected. A configuration in which the thin film portions are arranged radially from the center toward the end portion can be employed.

  That is, in the thin film portion (reference thin film portion, detection thin film portion), the center is most excellent in heat insulation from the frame portion. Since the contact points can be arranged at least in the region close to the center by arranging them radially toward the part, the temperature change due to the received infrared rays can be detected with higher accuracy.

Therefore, according to the present invention, a temperature change caused by received infrared rays can be detected with higher accuracy, and a decrease in gas detection accuracy can be suppressed.
Next, in the non-dispersive infrared analytical gas detector of the present invention, it is possible to adopt a configuration in which the plurality of reference contacts and the plurality of detection contacts are arranged line-symmetrically.

  In other words, if the plurality of reference contacts and the plurality of detection contacts are arranged symmetrically with respect to each other, the influence of the reference contact and the detection contact due to changes in the ambient temperature is equal, so that stable gas detection is possible. .

Therefore, according to the present invention, the influence of the ambient temperature change can be reduced and stable gas detection can be realized, so that a decrease in gas detection accuracy can be suppressed.
Note that the arrangement state of the plurality of reference contacts and the arrangement state of the plurality of detection contacts may be the same arrangement state instead of the line-symmetric arrangement. Even in such an arrangement state, the influence of the ambient temperature change can be reduced and stable gas detection can be realized, so that a decrease in gas detection accuracy can be suppressed.

  Next, in the non-dispersive infrared analytical gas detector of the present invention, the sensing element includes at least one reference thin film portion and at least two detection thin film portions as a plurality of thin film portions, It is possible to adopt a configuration including at least two thermopile.

  Thus, it becomes possible to detect at least two kinds of specific gases by providing at least two detection thin film portions and two thermopile. Also, with this configuration, it is possible to reduce the size of the infrared sensor and the non-dispersive infrared analytical gas detector as compared with the case where a plurality of detection elements are used.

  Next, in the non-dispersive infrared analytical gas detector according to the present invention, the thermopile constitutes at least a part of the part arranged in the frame part and a part arranged in the detection thin film part and the reference thin film part. It is possible to adopt a configuration in which a low resistance portion made of a material having an electric resistance value lower than that of the material is provided.

Since the thermopile is provided with the low resistance portion in this manner, the electric resistance value in the frame portion of the thermopile can be reduced and the influence of noise can be reduced, so that a decrease in gas detection accuracy can be suppressed.
Next, in the non-dispersive infrared analytical gas detector of the present invention, the detection thin film portion may have a different size from the reference thin film portion.

  In this way, by forming the detection thin film portion and the reference thin film portion in different sizes, a temperature difference can be generated between the detection contact and the reference contact even in the absence of a specific gas, and the temperature difference can be reduced. A corresponding sensor output can be obtained.

  That is, in the configuration in which it is determined that the specific gas does not exist when there is no sensor output (in the case of zero), there is a possibility that the state such as disconnection may be erroneously determined as the state without the sensor output. It is possible to determine the state where the specific gas does not exist based on the sensor output.

In addition, according to the present invention, it is possible to determine an abnormal state such as a disconnection depending on whether or not there is no sensor output in a situation where the specific gas does not exist.
Therefore, according to the present invention, it is possible to determine a state in which the specific gas does not exist, and it is possible to suppress erroneous determination due to the influence of disconnection or the like, thereby improving the gas detection accuracy.

It is sectional drawing which shows the internal structure of the non-dispersion type | mold infrared analysis type gas detector of 1st Embodiment. It is sectional drawing which shows the internal structure of an infrared sensor. It is a top view showing the external appearance of an infrared detection element. It is sectional drawing showing the AA cross section in FIG. 3 of an infrared rays detection element. It is a top view showing the external appearance of the 2nd infrared rays detection element in the non-dispersion type | mold infrared analysis type gas detector of 2nd Embodiment. It is sectional drawing showing the BB view cross section in FIG. 5 of a 2nd infrared rays detection element. It is explanatory drawing which shows the arrangement | positioning state of the detection contact in the detection thin film part regarding a 2nd infrared rays detection element, and a reference thin film part, and a reference contact. It is sectional drawing which shows the internal structure of the 3rd infrared sensor in the non-dispersion type | mold infrared analysis type gas detector of 3rd Embodiment. It is a top view showing the external appearance of a 3rd infrared rays detection element. FIG. 10 is a cross-sectional view illustrating a third infrared detection element taken along the line CC in FIG. 9. It is a top view which shows the external appearance of a 4th infrared rays detection element. It is a top view showing the external appearance of a 5th infrared rays detection element. It is a top view showing the external appearance of a 6th infrared rays detection element. It is a top view showing the external appearance of the conventional infrared rays detection element. It is sectional drawing showing the DD sectional view in FIG. 14 of the conventional infrared rays detection element.

Embodiments to which the present invention is applied will be described below with reference to the drawings.
[1. First Embodiment]
[1-1. overall structure]
FIG. 1 is a cross-sectional view showing the internal configuration of the non-dispersive infrared analytical gas detector 1 of the first embodiment.

In this non-dispersive infrared analytical gas detector 1 (hereinafter also simply referred to as gas detector 1), the measurement target gas is human breath, and the specific gas that is the detection target is carbon dioxide (CO ₂ ). . That is, the gas detector 1 is used to detect carbon dioxide contained in a person's breath.

The gas detector 1 includes a light source 11, a measurement cell 13, an infrared sensor 15, and a heater 17.
The light source 11 emits light including infrared rays.

  The measurement cell 13 is a cylindrical member made of aluminum, and the light source 11 is disposed inside one end in the axial direction of the cylinder. The measurement cell 13 also serves as a lens barrel that delivers infrared rays emitted from the light source 11 to the infrared sensor 15.

  The measurement cell 13 introduces and discharges an inner wall surface 21 that reflects infrared rays radiated from the light source 11, a gas space 23 into which human exhalation is introduced, and a measurement target gas (human exhalation) into the gas space 23. Gas inlet / outlet portion 25. The inner wall surface 21 is made of aluminum.

  The infrared sensor 15 is disposed at the end of the measurement cell 13 opposite to the side where the light source 11 is disposed. The infrared sensor 15 is output from the light source 11 and passes through the gas space 23 of the measurement cell 13 or An infrared detection signal corresponding to the intensity of the infrared light that is reflected by the inner wall surface 21 of the measurement cell 13 and is reached is output.

FIG. 2 is a cross-sectional view showing the internal configuration of the infrared sensor 15.
The infrared sensor 15 includes an infrared detection element 31, a pedestal 33, a cap 35, and two band-pass filters 37 and 38 (specifically, a detection filter 37 and a reference filter 38).

The infrared detection element 31 is a MEMS (microelectromechanical element type) thermopile, and outputs an infrared detection signal corresponding to the intensity of received infrared rays.
Here, the structure of the infrared detection element 31 will be briefly described with reference to FIGS. 3 and 4. 3 is a plan view showing the appearance of the infrared detection element 31, and FIG. 4 is a cross-sectional view showing the infrared detection element 31 taken along the line AA in FIG.

  The infrared detection element 31 includes a frame part 41, a detection thin film part 43, and a reference thin film part 44. The frame part 41 is formed so as to surround the detection thin film part 43 and the reference thin film part 44.

  The infrared detection element 31 covers a plurality of thermoelectric stacks 45 disposed from the detection thin film 43 through the frame 41 to the reference thin film 44 and a portion of the thermoelectric stack 45 disposed on the detection thin film 43. A detection infrared absorption layer 47, a reference infrared absorption layer 48 that covers a portion of the thermoelectric stack 45 disposed on the reference thin film portion 44, and two electrode pads 50 that are electrically connected to the thermoelectric stack 45 It is equipped with.

  Of the end portions of the thermoelectric stack 45, the end portion disposed on the detection thin film portion 43 is the detection contact 61, and the end portion disposed on the reference thin film portion 44 is the reference contact 62. In FIG. 3, a portion of the thermoelectric stack 45 that is covered with the detection infrared absorption layer 47 and the reference infrared absorption layer 48 is indicated by a dotted line.

Further, the plurality of thermoelectric stacks 45 connected in series are electrically connected to the two electrode pads 50 via the electrode lead portions 64 having two different end portions.
In the infrared detecting element 31, when the temperature of the infrared ray absorbing layer 47 for detection and the infrared ray absorbing layer for reference 48 change according to the intensity of the irradiated infrared rays, and a temperature difference ΔT is generated between them, the temperature difference ΔT is changed accordingly. Electromotive force ΔV is generated, and an infrared detection signal corresponding to the electromotive force ΔV is output from the electrode pad 50 to the outside.

  Specifically, in the infrared detection element 31 as a MEMS thermopile, the frame portion 41 is in thermal contact with the pedestal 33 (see FIG. 2), while the detection thin film portion 43 (detection contact 61) and The reference thin film portion 44 (reference contact 62) has a structure thermally separated from the pedestal 33. In other words, the frame part 41 is in contact with the pedestal 33, and the detection thin film part 43 and the reference thin film part 44 are arranged so as to be bridged at the upper part of the frame part 41 and are separated from the pedestal 33. The detection thin film portion 43 (detection contact 61) and the reference thin film portion 44 (reference contact 62) are thermally separated from each other.

  A detection infrared absorption layer 47 is formed on the detection contact 61, and a reference infrared absorption layer 48 is formed on the reference contact 62. When the infrared ray that has passed through the detection filter 37 is irradiated to the infrared ray absorption layer 47 for detection, the temperature of the infrared ray absorption layer 47 for detection changes in accordance with the amount of irradiated infrared ray, and the infrared ray that has passed through the reference filter 38. When the reference infrared absorption layer 48 is irradiated, the temperature of the reference infrared absorption layer 48 changes according to the amount of irradiated infrared rays.

Here, the detection filter 37 is a bandpass filter that selectively transmits infrared light having a detection wavelength (4.3 [μm]), and infrared light having a wavelength of 4.3 [μm] is carbon dioxide (CO ₂ ) Is absorbed. The reference filter 38 is a bandpass filter that selectively transmits infrared light having a reference wavelength (3.9 [μm]), and infrared light having a wavelength of 3.9 [μm] is not absorbed by gas. There are characteristics.

Therefore, the CO ₂ concentration can be determined by detecting the temperature change state of the detection infrared absorption layer 47 while using the temperature of the reference infrared absorption layer 48 as a reference. In other words, the CO ₂ concentration can be determined based on the temperature difference between the detection infrared absorption layer 47 and the reference infrared absorption layer 48.

That is, the infrared detection element 31 generates an electromotive force (V) at both ends of the plurality of thermopile units 45 connected in series according to the temperature difference between the detection infrared absorption layer 47 and the reference infrared absorption layer 48.
Here, the electromotive force V when n thermoelectric stacking units 45 are connected in series is expressed by the following [Equation 1].

T1n is the temperature of the detection contact 61, T2n is the temperature of the reference contact 62, and α is the Seebeck coefficient of the thermopile 45.
That is, the electromotive force V of the thermopile 45 changes according to the temperature T1n of the detection contact 61 and the temperature T2n of the reference contact 62 without being affected by the temperature of the frame 41. The electromotive force V of the thermopile 45 changes in accordance with the intensity of the infrared detected by the infrared detecting element 31.

  Therefore, the infrared detection element 31 outputs the electromotive force V of the thermopile 45 as an infrared detection signal, thereby suppressing the influence of the temperature change of the frame 41 and detecting the infrared absorption layer 47 and the reference infrared absorption layer. An infrared detection signal corresponding to the temperature difference from 48 can be output. This infrared detection signal changes according to the concentration of carbon dioxide contained in the measurement target gas.

In FIG. 3, the temperatures T1 ₁ , T1 ₂ , T1 ₃ corresponding to the three detection contacts 61 are described with reference numerals, and the temperatures T2 ₁ , T2 corresponding to the three reference contacts 62 are shown. ₂ and T2 ₃ are described with reference numerals.

  Returning to FIG. 2, the pedestal 33 is an iron member that supports the infrared detection element 31. The thermal conductivity of the iron member constituting the pedestal 33 is 84 [W / m · K]. The pedestal 33 includes an insertion hole 34 through which the signal line 51 connected to the infrared detection element 31 is inserted. An insulating material 36 is disposed on the inner wall of the insertion hole 34, and the insulating material 36 electrically insulates the base 33 and the signal line 51.

  One end of the signal line 51 is electrically connected to the electrode pad 50 of the infrared detection element 31 and the other end is electrically connected to an external device, thereby providing a signal path for outputting an infrared detection signal to the outside. Form. The signal line 51 is electrically connected to the electrode pad 50 of the infrared detecting element 31 by bonding using a gold lead wire 54 while being inserted into the insertion hole 34 of the pedestal 33.

  Returning to FIG. 2, the cap 35 is a member made of a stainless alloy and forming an element arrangement space 55 that accommodates the infrared detection element 31 supported by the pedestal 33. The cap 35 is joined to the pedestal 33 by resistance welding to form an element arrangement space 55 together with the pedestal 33. The cap 35 includes a first window portion 57 and a second window portion 58 for taking light into the element arrangement space 55 from the outside.

  The detection filter 37 is fixed to the cap 35 with an epoxy adhesive so as to cover the first window portion 57 of the cap 35, and the reference filter 38 is an epoxy so as to cover the second window portion 58 of the cap 35. It is fixed to the cap 35 with a system adhesive.

As shown in FIG. 1, the infrared sensor 15 having such a configuration is fixed to the end portion of the measurement cell 13 by an aluminum fixing jig 59.
The heater 17 is a silicon rubber heater and is disposed so as to surround the measurement cell 13. The heater 17 heats the measurement cell 13 at a specific control temperature set to 40 [° C.] or higher (in this embodiment, set to 50 [° C.]).

[1-2. Gas detection]
The gas detector 1 having such a configuration introduces / exhales human exhalation (measurement target gas) into the gas space 23 of the measurement cell 13 via the gas inlet / outlet 25 and then exhales into the gas space 23. Detects the concentration of carbon dioxide (specific gas) contained in.

  That is, among infrared rays emitted from the light source 11, infrared rays having a wavelength of 4.3 [μm] are absorbed by carbon dioxide contained in the exhaled breath introduced into the gas space 23 of the measurement cell 13. The intensity of the infrared ray having a wavelength of 4.3 [μm] that is reached varies depending on the concentration of carbon dioxide. And since the infrared detection signal output from the infrared sensor 15 (infrared detection element 31) changes according to the concentration of carbon dioxide, the concentration of carbon dioxide contained in human breath can be detected based on the infrared detection signal. . The infrared sensor 15 corresponds to the transmission center wavelength (4.3 [μm]) of the detection filter 37 based on the infrared rays corresponding to the transmission center wavelength (3.9 [μm]) of the reference filter 38. Detect infrared rays.

  In the gas detector 1, the heater 17 heats the measurement cell 13 to suppress the formation of condensation on the inner wall surface 21 of the measurement cell 13, so that infrared rays emitted from the light source 11 are emitted from the inner wall surface 21 of the measurement cell 13. Reduce the amount of attenuation when reflecting.

The heat generated by the heater 17 is conducted not only to the measurement cell 13 but also to the light source 11, the fixing jig 59, and the infrared sensor 15 through the measurement cell 13.
In addition, as described above, the infrared detection element 31 outputs an infrared detection signal corresponding to the temperature difference between the detection contact 61 disposed in the detection thin film portion 43 and the reference contact 62 disposed in the reference thin film portion 44.

  At this time, the temperature of the detection contact 61 changes according to the concentration of carbon dioxide because the temperature changes due to the infrared rays transmitted through the detection filter 37. On the other hand, the temperature of the reference contact 62 is changed by the infrared rays that have passed through the reference filter 38 and is not affected by the change in the concentration of carbon dioxide when the temperature changes. Therefore, the reference contact 62 can be used as a reference temperature for detecting the concentration of carbon dioxide. For this reason, the infrared detection signal according to the temperature difference between the detection contact 61 and the reference contact 62 changes according to the concentration of carbon dioxide.

Further, since the detection contact 61 and the reference contact 62 are disposed on the detection thin film portion 43 and the reference thin film portion 44, they are not easily affected by the temperature change of the frame portion 41.
For these reasons, the infrared sensor 15 including the infrared detection element 31 detects infrared rays according to the concentration of carbon dioxide contained in the breath of the person introduced into the measurement cell 13 while suppressing the influence of the temperature change of the frame portion 41. Output a signal.

Therefore, by using this gas detector 1, it is possible to detect the concentration of carbon dioxide contained in human breath based on the infrared detection signal.
The heat generated by the heater 17 is transmitted to the pedestal 33 of the infrared sensor 15 through the measurement cell 13 and is conducted to the cap 35. Therefore, condensation on the surface of the cap 35 can be prevented by heating the heater 17.

[1-3. effect]
As described above, in the non-dispersive infrared analytical gas detector 1 of the present embodiment, the infrared detection element 31 of the infrared sensor 15 has the infrared intensity received by the detection contact 61 with the reference contact 62 as a reference. Based on this, the gas (carbon dioxide) corresponding to the infrared of the detection wavelength is detected.

And since the reference contact 62 is provided not in the frame portion 41 of the infrared detection element 31 but in the reference thin film portion 44, it is difficult to be affected by heat conduction from the frame portion 41 of the infrared detection element 31.
For these reasons, the infrared detection element 31 is less likely to fluctuate in sensor output due to a temperature change of the reference contact 62 due to heat conduction from the heater 17, and can suppress a decrease in gas detection accuracy.

  In addition, since the plurality of thermopile units 45 include a plurality of reference contacts 62 and a plurality of detection contacts 61 as a whole, a plurality of thermopile units 45 having a minimum configuration including one reference contact 62 and one detection contact 61 are connected in series. It becomes the structure equivalent to what was connected, and the sensor output of the infrared sensor 15 can be ensured largely. By ensuring a large sensor output of the infrared sensor 15 in this way, it is possible to reduce the influence of noise and suppress a decrease in gas detection accuracy.

Furthermore, since this embodiment can suppress that the inner wall surface of the measurement cell 13 condenses by providing the heater 17 which heats the measurement cell 13, it can suppress the misdetection resulting from dew condensation.
Therefore, according to the present embodiment, it is possible to suppress a decrease in gas detection accuracy due to the influence of heating of the heater 17 when detecting carbon dioxide contained in human exhalation in an atmosphere with high humidity.

[1-4. Correspondence with Claims]
Here, the correspondence of the words in the claims and the present embodiment will be described.
Human exhalation corresponds to an example of a measurement target gas, carbon dioxide corresponds to an example of a specific gas, the infrared detection element 31 corresponds to an example of a detection element, and the detection filter 37 and the reference filter 38 are wavelength selection filters. It corresponds to an example.

[2. Second Embodiment]
As a second embodiment, a plurality of detection contacts are arranged radially from the center to the end of the detection thin film portion, and a plurality of reference contacts are arranged radially from the center to the end of the reference thin film portion. A non-dispersive infrared analytical gas detector including the second infrared detecting element 131 is described.

  The non-dispersive infrared analytical gas detector of the second embodiment is configured by replacing the infrared detector 31 in the non-dispersive infrared analytical gas detector of the first embodiment with a second infrared detector 131.

  In the following description, the same configurations as those of the first embodiment among the configurations of the second embodiment are the same as those of the first embodiment and the description thereof is omitted, and the configurations of the second embodiment are omitted. A description will be given centering on differences from the first embodiment.

  FIG. 5 is a plan view showing the appearance of the second infrared detection element 131 in the non-dispersive infrared analytical gas detector of the second embodiment, and FIG. It is sectional drawing showing a B view cross section.

The second infrared detection element 131 is a MEMS (microelectromechanical element type) thermopile, and outputs an infrared detection signal corresponding to the intensity of received infrared light.
The second infrared detection element 131 includes a frame part 141, a detection thin film part 143, and a reference thin film part 144. The frame portion 141 is formed so as to surround the detection thin film portion 143 and the reference thin film portion 144.

  The second infrared detecting element 131 includes a plurality of thermopile units 145 arranged from the detecting thin film unit 143 through the frame unit 141 to the reference thin film unit 144, and a portion of the thermoelectric stacking unit 145 arranged in the detecting thin film unit 143. An infrared absorbing layer for detection (not shown) that covers the reference, an infrared absorbing layer for reference (not shown) that covers a portion of the thermoelectric stack portion 145 disposed on the reference thin film portion 144, and the thermoelectric stack portion 145 are electrically connected. The two electrode pads 150 are provided.

  In FIGS. 5 and 6, the detection infrared absorption layer and the reference infrared absorption layer are not shown, but similar to the detection infrared absorption layer 47 and the reference infrared absorption layer 48 of the first embodiment. The infrared ray absorbing layer for detection and the infrared ray absorbing layer for reference are irradiated with infrared rays that have passed through the filter for detection 37 and the filter for reference 38, so that the temperature changes according to the amount of infrared rays that are irradiated.

Of the end portions of the thermoelectric stack portion 145, the end portion disposed on the detection thin film portion 143 is the detection contact 161, and the end portion disposed on the reference thin film portion 144 is the reference contact 162.
Further, the plurality of thermopile units 145 connected in series are electrically connected to the two electrode pads 150 via the electrode lead portions 164 having two different ends.

  In the second infrared detecting element 131, the temperature of the detecting infrared absorbing layer (not shown) and the reference infrared absorbing layer (not shown) change depending on the intensity of the irradiated infrared rays, and a temperature difference ΔT is generated between them. Then, an electromotive force ΔV corresponding to the temperature difference ΔT is generated, and an infrared detection signal corresponding to the electromotive force ΔV is output from the electrode pad 150 to the outside.

Here, FIG. 7 is an explanatory diagram showing an arrangement state of the detection contact 161 and the reference contact 162 in the detection thin film portion 143 and the reference thin film portion 144 related to the second infrared detection element 131.
As shown in FIG. 7, the detection contacts 161 are arranged radially from the center to the end portion (specifically, four corners) of the detection thin film portion 143, and 27 detection contacts 161 detect the detection contacts 161. The thin film portion 143 is disposed. The reference contacts 162 are arranged radially from the center to the end portion (specifically, four corners) of the reference thin film portion 144, and 27 reference contacts 162 are arranged on the reference thin film portion 144. Has been.

  Here, in the detection thin film part 143, the center is most excellent in heat insulation from the frame part 141. Further, when the plurality of detection contacts 161 are arranged, the detection contacts 161 can be arranged at least in a region near the center by arranging them radially from the center of the detection thin film portion 143 toward the end.

  For this reason, in the second infrared detection element 131, the detection contact 161 is disposed at least in the central region of the detection thin film portion 143. Therefore, heat conduction from the frame portion 141 hardly occurs in the detection contact 161. The influence of heat conduction from the frame part 141 can be suppressed. Thereby, the detection contact 161 can detect the temperature change by the infrared rays received by the infrared absorption layer for detection (not shown) with higher accuracy.

  Similarly, in the reference thin film portion 144 and the plurality of reference contacts 162, heat conduction from the frame portion 141 to the reference contact 162 hardly occurs, and the influence of heat conduction from the frame portion 141 can be suppressed. . Thereby, the reference contact 162 can detect the temperature change by the infrared rays received by the reference infrared absorption layer (not shown) with higher accuracy.

Therefore, according to the second embodiment, the temperature change due to the infrared light received by the second infrared detecting element 131 can be detected with higher accuracy, so that a decrease in gas detection accuracy can be suppressed.
As shown in FIG. 7, in the second infrared detection element 131, the arrangement state of the plurality of detection contacts 161 and the arrangement state of the plurality of reference contacts 162 are line-symmetric with respect to the virtual line 170.

  In this way, if the plurality of reference contacts 162 and the plurality of detection contacts 161 are arranged symmetrically with respect to each other, the influence of the reference contact 162 and the detection contact 161 due to the ambient temperature change is equal.

  For this reason, the 2nd infrared rays detection element 131 can suppress that the influence by ambient temperature change will be in the state from which a reference contact 162 and the detection contact 161 differ greatly. In other words, the second infrared detection element 131 is unlikely to have non-uniform influences of ambient temperature changes between the reference contact 162 and the detection contact 161, and has a detection error due to non-uniform influences of ambient temperature change. Since it can suppress, stable gas detection is attained.

Therefore, according to the second embodiment, the influence of the ambient temperature change can be reduced, and stable gas detection can be realized, so that a decrease in gas detection accuracy can be suppressed.
Here, the correspondence of the words in the claims and the present embodiment will be described. The second infrared detection element 131 corresponds to an example of a detection element.

[3. Third Embodiment]
As a third embodiment, a third infrared detection element 231 having two detection thin film portions 243 and 246 (specifically, first detection thin film portion 243 and second detection thin film portion 246) and one reference thin film portion 244 is provided. A non-dispersive infrared analytical gas detector will be described. The third infrared detection element 231 is provided in the third infrared sensor 215.

  The non-dispersive infrared analytical gas detector of the third embodiment is configured by replacing the infrared sensor 15 in the non-dispersive infrared analytical gas detector of the first embodiment with a third infrared sensor 215.

  In the following description, the same configurations as those of the first embodiment among the configurations of the third embodiment are the same as those of the first embodiment, and the description thereof is omitted, and the configurations of the third embodiment are omitted. A description will be given centering on differences from the first embodiment.

FIG. 8 is a cross-sectional view showing the internal configuration of the third infrared sensor 215 in the non-dispersive infrared analytical gas detector of the third embodiment.
The third infrared sensor 215 includes a third infrared detection element 231 and three bandpass filters 237, 238, and 239 (specifically, a first detection filter 237, a reference filter 238, and a second detection filter 239). And). The cap 235 of the third infrared sensor 215 has three windows 257, 258, and 259 for taking light into the element arrangement space 55 from the outside (specifically, the first detection window 257 and the reference window 258). , Second detection window 259).

The third infrared detecting element 231 is a MEMS (microelectromechanical element type) thermopile, and outputs an infrared detection signal corresponding to the intensity of received infrared light.
Here, the structure of the third infrared detecting element 231 will be briefly described with reference to FIGS. 9 and 10. FIG. 9 is a plan view showing the appearance of the third infrared detection element 231, and FIG. 10 is a cross-sectional view showing the third infrared detection element 231 taken along the line CC in FIG. 9.

  The third infrared detection element 231 includes a frame part 241, a first detection thin film part 243, a second detection thin film part 246, and a reference thin film part 244. The frame portion 241 is formed so as to surround the first detection thin film portion 243, the reference thin film portion 244, and the second detection thin film portion 246.

  The third infrared detection element 231 includes a plurality of first thermopile units 245 arranged from the first detection thin film unit 243 through the frame unit 241 to the reference thin film unit 244, and a first detection among the first thermopile units 245. A first infrared absorbing layer for detection (not shown) that covers a portion disposed in the thin film portion 243, and a reference infrared absorbing layer (not illustrated) that covers a portion disposed in the reference thin film portion 244 in the first thermoelectric stack 245. ) And two first electrode pads 250 that are electrically connected to the first thermoelectric stacking unit 245.

Of the end portions of the first thermoelectric stack 245, the end portion disposed on the first detection thin film portion 243 is the first detection contact 261, and the end portion disposed on the reference thin film portion 244 is the first reference contact 262. is there.
Further, the plurality of first thermoelectric stacks 245 connected in series are electrically connected to the two first electrode pads 250 via the first electrode lead portions 264 having two different end portions.

  Next, the third infrared detecting element 231 includes a plurality of second thermoelectric stacking units 249 arranged from the second detecting thin film unit 246 to the reference thin film unit 244 through the frame unit 241, and the second thermoelectric stacking unit 249. A second detection infrared absorption layer (not shown) covering a portion disposed in the second detection thin film portion 246 and a reference infrared absorption layer covering a portion disposed in the reference thin film portion 244 in the second thermoelectric stack portion 249. (Not shown) and two second electrode pads 252 that are electrically connected to the second thermoelectric stacking part 249.

The plurality of second thermoelectric stacks 249 connected in series are electrically connected to the two second electrode pads 252 via the second electrode lead portions 268 having two different end portions.
In FIGS. 9 and 10, the first detection infrared absorption layer, the reference infrared absorption layer, and the second detection infrared absorption layer are not shown, but the first detection filter 237 and the reference filter are respectively shown. By irradiating the infrared rays that have passed through the second detection filter 239, the temperature changes according to the amount of the irradiated infrared rays.

  In the third infrared detecting element 231, the temperature of the first detecting infrared absorbing layer (not shown) and the reference infrared absorbing layer (not shown) change according to the intensity of the irradiated infrared rays, and the temperature difference ΔT between the two changes. Occurs, an electromotive force ΔV corresponding to the temperature difference ΔT is generated, and an infrared detection signal corresponding to the electromotive force ΔV is output from the first electrode pad 250 to the outside.

  Further, in the third infrared detecting element 231, the temperature of the second detecting infrared absorbing layer (not shown) and the reference infrared absorbing layer (not shown) are changed according to the intensity of the irradiated infrared rays, and the temperature of both is changed. When the difference ΔT occurs, an electromotive force ΔV corresponding to the temperature difference ΔT is generated, and an infrared detection signal corresponding to the electromotive force ΔV is output from the second electrode pad 252 to the outside.

  Specifically, in the third infrared detecting element 231 as a MEMS thermopile, the frame portion 241 is in thermal contact with the pedestal 33 (see FIG. 2), while the first detecting thin film portion 243 (first 1 detection contact 261), second detection thin film portion 246 (second detection contact 265), and reference thin film portion 244 (first reference contact 262 and second reference contact 266) are thermally separated from the base 33, respectively. It is. In other words, the frame part 241 is in contact with the pedestal 33, and the first detection thin film part 243, the second detection thin film part 246, and the reference thin film part 244 are arranged so as to be bridged at the upper part of the frame part 241. In addition, it is separated from the pedestal 33. The first detection thin film portion 243 (first detection contact 261), the second detection thin film portion 246 (second detection contact 265), and the reference thin film portion 244 (first reference contact 262 and second reference contact 266) are mutually connected. Thermally separated.

  A first detection infrared absorption layer (not shown) is formed on the first detection contact 261, and a second detection infrared absorption layer (not shown) is formed on the second detection contact 265. A reference infrared absorbing layer (not shown) is formed on the reference contact 262 and the second reference contact 266.

  When the infrared rays that have passed through the first detection filter 237 are applied to the first detection infrared absorption layer, the temperature of the first detection infrared absorption layer changes in accordance with the amount of infrared rays that are applied. When the infrared rays that have passed through the second detection filter 239 are applied to the second detection infrared absorption layer, the temperature of the second detection infrared absorption layer changes in accordance with the amount of the infrared rays applied. When the infrared rays that have passed through the reference filter 238 are applied to the reference infrared absorption layer, the temperature of the reference infrared absorption layer changes in accordance with the amount of irradiated infrared rays.

Here, the first detection filter 237 is a band-pass filter that selectively transmits infrared light having a first detection wavelength (4.3 [μm]), and infrared light having a wavelength of 4.3 [μm] It has the characteristic of being absorbed by carbon (CO ₂ ). The second detection filter 239 is a bandpass filter that selectively transmits infrared light having a second detection wavelength (4.7 [μm]), and infrared light having a wavelength of 4.7 [μm] is monoxide. It has the characteristic of being absorbed by carbon (CO). Further, the reference filter 238 is a bandpass filter that selectively transmits infrared light having a reference wavelength (3.9 [μm]), and infrared light having a wavelength of 3.9 [μm] is not absorbed by gas. There are characteristics.

For this reason, it is possible to determine the CO ₂ concentration by detecting the temperature change state of the first detection infrared absorption layer while using the temperature of the reference infrared absorption layer as a reference. In other words, the CO ₂ concentration can be determined based on the temperature difference between the first detection infrared absorption layer and the reference infrared absorption layer.

  Further, the CO concentration can be determined by detecting the temperature change state of the second detection infrared absorption layer while using the temperature of the reference infrared absorption layer as a reference. In other words, it is possible to determine the CO concentration based on the temperature difference between the second detection infrared absorption layer and the reference infrared absorption layer.

  That is, the third infrared detecting element 231 has electromotive forces (V) at both ends of the plurality of first thermoelectric stacks 245 connected in series according to the temperature difference between the first detecting infrared absorbing layer and the reference infrared absorbing layer. ) And an electromotive force (V) is generated at both ends of the plurality of second thermoelectric stacks 249 connected in series according to the temperature difference between the second detection infrared absorption layer and the reference infrared absorption layer.

  The electromotive force (V) generated at both ends of the plurality of first thermoelectric stacks 245 changes according to the concentration of carbon dioxide contained in the measurement target gas, and detects infrared rays output from the first electrode pad 250. The signal varies with the concentration of carbon dioxide. In addition, the electromotive force (V) generated at both ends of the plurality of second thermoelectric stacks 249 varies depending on the concentration of carbon monoxide contained in the measurement target gas, and the infrared rays output from the second electrode pad 252. The detection signal varies depending on the concentration of carbon monoxide.

  That is, although the third infrared detection element 231 is one element, the two detection thin film portions (first detection thin film portion 243, second detection thin film portion 246) and two thermopile stacks (first thermoelectric stack portion 245, first Since two thermoelectric stacking parts 249) are provided, two kinds of gases (carbon dioxide and carbon monoxide) can be detected.

  As described above, according to the third infrared detection element 231, it is not necessary to provide one element for each gas to be detected when detecting two types of gases (carbon dioxide and carbon monoxide). The size of the sensor and the non-dispersive infrared analytical gas detector can be reduced.

Here, the correspondence of the words in the claims and the present embodiment will be described. The third infrared detection element 231 corresponds to an example of a detection element.
[4. Fourth Embodiment]
The infrared detection element for detecting two types of gases is not limited to the third infrared detection element 231 described above, and may be an infrared detection element having two detection thin film portions and two reference thin film portions. .

Therefore, as a fourth embodiment, a fourth infrared detection element 331 having two detection thin film portions 43 and two reference thin film portions 44 will be described.
FIG. 11 is a plan view showing the external appearance of the fourth infrared detecting element 331. In addition, in FIG. 11, the infrared rays for a detection which cover the part arrange | positioned in the detection thin film part 43 among the thermoelectric stack parts 45, and the reference infrared which covers the part arrange | positioned in the reference thin film part 44 among the thermoelectric stack parts 45 are shown. The illustration of the absorption layer is omitted.

The 4th infrared detection element 331 can be comprised by connecting each frame part 41 integrally using the two infrared detection elements 31 of 1st Embodiment.
And as a bandpass filter corresponding to each of the two detection thin film parts 43, while using the bandpass filter which selectively permeate | transmits the infrared rays of the wavelength absorbed by detection object gas, each of the two reference thin film parts 44 is used. As a corresponding bandpass filter, a bandpass filter that selectively transmits infrared light having a reference wavelength (3.9 [μm]) is used.

  For example, as a bandpass filter corresponding to each of the two detection thin film portions 43, a bandpass filter that selectively transmits infrared light having a first detection wavelength (4.3 [μm]) and a second detection wavelength (4. 7 [μm]) and a band-pass filter that selectively transmits infrared rays, carbon dioxide and carbon monoxide can be detected.

  The fourth infrared detecting element 331 includes two reference thin film portions 44, and includes a thermopile 45 for detecting a first gas (for example, carbon dioxide) and a second gas (for example, carbon monoxide). Gas detection can be performed using the separate reference thin film portions 44 for the thermopile 45 for detection.

  Thereby, compared with the case where one reference thin film part is shared by two thermoelectric stack parts as in the third embodiment, the influence of the change in the amount of light incident on the detection thin film part 43 of one thermoelectric stack part 45 is affected. Thus, the output of the other thermopile unit 45 can be prevented from fluctuating.

Therefore, by using the fourth infrared detecting element 331, it is possible to suppress the occurrence of errors in detecting two types of gases, and thus it is possible to realize more accurate gas detection.
Here, the correspondence of the words in the claims and the present embodiment will be described. The fourth infrared detection element 331 corresponds to an example of a detection element.

[5. Fifth Embodiment]
As a fifth embodiment, a fifth infrared detection element 431 provided with a thermopile portion having a low resistance portion will be described. FIG. 12 is a plan view showing the appearance of the fifth infrared detection element 431. FIG.

  In the following description, the same configuration as that of the second embodiment among the configurations of the fifth infrared detection element is the same as that of the second embodiment, and the description thereof is omitted. Of these, differences from the first embodiment will be mainly described.

  The fifth infrared detecting element 431 is configured by replacing a part of the thermopile unit 145 in the second infrared detecting element 131 of the second embodiment with a low resistance part 445. In other words, the fifth infrared detecting element 431 is configured such that a part of the thermoelectric stacking part 145 extending from the detection thin film part 143 to the reference thin film part 144 in the second infrared detecting element 131 is a low resistance part. 445 is replaced.

  And the low resistance part 445 is comprised with the aluminum, and aluminum has a lower electrical resistance value than the material which comprises the part arrange | positioned in the detection thin film part 143 and the reference thin film part 144 among the thermoelectric accumulation parts 145.

  For this reason, the entire electrical resistance value of the thermoelectric stacking unit 145 and the low resistance unit 445 from the detection contact 161 (detection thin film unit 143) to the reference contact 162 (reference thin film unit 144) is the thermoelectric stacking unit 145 of the second embodiment. The resistance value is lower than

  As a result, sensor output noise can be reduced as a whole of the plurality of thermopile units 145 and the plurality of low resistance units 445. That is, the high-resistance component itself can be a noise generation source, but by reducing the resistance value, the generation of noise can be suppressed as an infrared detection element, and the deterioration of gas detection accuracy can be suppressed.

Therefore, by using the 5th infrared detection element 431, generation | occurrence | production of noise can be reduced by the resistance reduction of a thermopile part, and the fall of gas detection accuracy can be suppressed.
Here, the correspondence of the words in the claims and the present embodiment will be described. The fifth infrared detection element 431 corresponds to an example of a detection element.

[6. Other Embodiments]
As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, In the range which does not deviate from the summary of this invention, it is possible to implement in various aspects.

  For example, in the above-described embodiment, the detection thin film portion and the reference thin film portion have the same size. However, the detection thin film portion and the reference thin film portion may have different sizes.

  Therefore, the sixth infrared detection element 531 having a configuration in which the detection thin film portion and the reference thin film portion are different from each other will be described. FIG. 13 is a plan view showing the appearance of the sixth infrared detection element 531.

  In the following description, the same configuration as that of the first embodiment among the configurations of the sixth infrared detection element is the same as that of the first embodiment, and the description thereof is omitted, and the configuration of the sixth infrared detection element is omitted. Of these, differences from the first embodiment will be mainly described.

  The sixth infrared detection element 531 replaces the detection thin film portion 43 in the infrared detection element 31 of the first embodiment with a larger enlarged detection thin film portion 543, and the detection infrared absorption layer 47 becomes a larger enlarged detection infrared absorption layer 547. It is constructed by replacing with.

  As described above, the sixth infrared detection element 531 having a size different from that of the enlarged detection thin film portion 543 and the reference thin film portion 44 is referred to the detection contact 61 even when the specific gas (carbon dioxide in the present embodiment) does not exist. A temperature difference can be generated between the contact 62 and a sensor output corresponding to the temperature difference.

  That is, in the configuration in which it is determined that the specific gas does not exist when there is no sensor output (in the case of zero), there is a possibility that the state such as disconnection may be erroneously determined as the state without the sensor output. By using the detection element 531, it is possible to determine a state where the specific gas (carbon dioxide) does not exist based on the sensor output.

  Further, the sixth infrared detecting element 531 can determine an abnormal state such as a disconnection depending on whether or not there is no sensor output in a situation where the specific gas (carbon dioxide) does not exist.

  Therefore, according to the sixth infrared detecting element 531, it is possible to determine the state where the specific gas (carbon dioxide) does not exist, and it is possible to suppress erroneous determination due to the influence of disconnection or the like, so that the gas detection accuracy can be improved.

  Further, in the above-described embodiment, the embodiment in which carbon dioxide and carbon monoxide are detected as the specific gas has been described. However, the specific gas is not limited to these, for example, ethanol (detection wavelength: 3.4 [μm ] Or 9.4 [μm]) or the like may be applied to a non-dispersive infrared analytical gas detector. In that case, a band pass filter may be appropriately selected according to the detection wavelength of the specific gas.

  Furthermore, the number of detection thin film portions is not limited to one or two, and an infrared detection element including three or more detection thin film portions may be used.

  DESCRIPTION OF SYMBOLS 1 ... Non-dispersion type infrared analytical gas detector, 11 ... Light source, 13 ... Measurement cell, 15 ... Infrared sensor, 17 ... Heater, 31 ... Infrared sensing element, 33 ... Base, 37 ... Detection filter, 38 ... For reference Filter, 41 ... Frame portion, 43 ... Detection thin film portion, 44 ... Reference thin film portion, 45 ... Thermoelectric stacking portion, 47 ... Detection infrared absorption layer, 48 ... Reference infrared absorption layer, 50 ... Electrode pad, 51 ... Signal line , 61 ... detection contact, 62 ... reference contact, 131 ... second infrared detection element, 141 ... frame part, 143 ... detection thin film part, 144 ... reference thin film part, 145 ... thermopile stacking part, 150 ... electrode pad, 161 ... detection Contact, 162 ... Reference contact, 215 ... Third infrared sensor, 231 ... Third infrared detection element, 237 ... First detection filter, 238 ... Reference filter, 239 ... Second detection filter, 241 ... Frame portion, 243 Detection thin film portion, 243 ... first detection thin film portion, 244 ... reference thin film portion, 245 ... first thermoelectric stacking portion, 246 ... second detection thin film portion, 249 ... second thermoelectric deposition portion, 250 ... first electrode pad, 252 ... Second electrode pad, 261 ... first detection contact, 262 ... first reference contact, 264 ... first electrode lead, 265 ... second detection contact, 266 ... second reference contact, 268 ... second electrode lead , 431... 4th infrared detecting element, 431... 5th infrared detecting element, 445... Low resistance part, 531... 6th infrared detecting element, 543.

Claims (6)

A non-dispersive infrared analytical gas detector that detects a specific gas contained in a gas to be measured,
A light source that emits infrared light;
A measurement cell into which the measurement target gas is introduced;
An infrared sensor that outputs an infrared detection signal according to the intensity of the infrared light that has reached;
A heater for heating the measurement cell;
With
The light source and the infrared sensor are connected in a state of being thermally conducted to the measurement cell,
The infrared sensor is
A sensing element having a frame portion surrounding each of the plurality of thin film portions, and having a thermopile disposed on the thin film portion and the frame portion,
A wavelength selective filter that transmits the infrared light having a predetermined wavelength according to each of the plurality of thin film portions;
With
The detection element includes, as the plurality of thin film portions, at least one reference thin film portion and at least one detection thin film portion,
The wavelength selective filter transmits the infrared light of the reference wavelength to the reference thin film portion, and transmits the infrared light of the detection wavelength to the detection thin film portion,
The thermopile is alternately connected with a plurality of reference contacts provided on the reference thin film portion and a plurality of detection contacts provided on the detection thin film portion,
A non-dispersive infrared analytical gas detector. The plurality of reference contacts are arranged radially from the center to the end of the reference thin film portion,
The plurality of detection contacts are arranged radially from the center to the end of the detection thin film portion,
The non-dispersive infrared analytical gas detector according to claim 1. The plurality of reference contacts and the plurality of detection contacts are arranged in line symmetry,
The non-dispersive infrared analytical gas detector according to claim 1 or 2, wherein The detection element includes at least one reference thin film portion and at least two detection thin film portions as the plurality of thin film portions, and further includes at least two thermopile,
The non-dispersive infrared analytical gas detector according to any one of claims 1 to 3, wherein: The thermopile is formed of a material having a lower electrical resistance value than at least a part of the portion disposed in the frame portion than the material constituting the portion disposed in the detection thin film portion and the reference thin film portion. Having a resistance part,
The non-dispersive infrared analytical gas detector according to any one of claims 1 to 4, wherein: The sensing thin film portion is different in size from the reference thin film portion;
The non-dispersive infrared analytical gas detector according to any one of claims 1 to 5, wherein: