JP2003130794A - Infrared gas analyzer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an infrared gas analyzer capable of performing curing treatments at low temperatures at assembly by the adhesion of a sensor, maintaining high sensitivity for a long period, and performing stable measurement. SOLUTION: The part of a multi-level (a) of a through hole 2 is formed by boring a hole of a diameter ϕf and a hole of a diameter ϕb (ϕf<ϕb) in a metal block 1 from both end surfaces toward its center. Window plates 7 and 8 of CaF2 are made to adhere to a multi-level of the interface of a hole 5 connected to the hole of the diameter ϕf, and a rear lid 9 is made to adhere to a countersunk part of the hole of the diameter ϕb each by a chemically stable and low-reactive adhesive BB2130 made of an American company, Tra- Con, to form a front chamber 10 and a rear chamber 11. A through hole 3 and an L-shaped tunnel 4 each connecting with the holes of the diameter ϕf and of the diameter ϕb vertically from a side surface of the block 1 are formed, and a membrane-heating-coil flow sensor 12 is made to adhere to a bottom of the through hole 3 by the adhesive BB2130.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infrared gas analyzer for measuring the concentration of a specific gas species by utilizing the gas pressure fluctuation associated with the infrared spectrum absorption of an infrared active component gas.

[0002]

2. Description of the Related Art Many heteronuclear molecules composed of two or more different atoms undergo kinetic energy level transitions of vibration and rotation peculiar to their chemical species when irradiated with infrared light having a wavelength of 1 to 20 μm. It absorbs a specific infrared spectrum and causes thermodynamic changes such as an increase in internal energy, volume or pressure. Non-dispersive infrared gas analyzer (hereinafter ND
IR) is a device that measures the concentration of such gas components by utilizing such characteristics.

FIG. 5 shows the structure of a single beam NDIR having a flow sensor as a detector. As shown in the figure, this type of NDIR generally includes a light source section 20 for generating infrared light, a cell section 30 into which a gas to be measured (sample gas) is introduced,
The detector unit 40 of the detector unit 40 that finally measures the sample concentration by measuring the intensity of the infrared light that has passed through the cell unit 30.
It is composed of units. The light source unit 20 is responsible for generating infrared light, and is a heater (light source) 21 that is a generation source for generating infrared light, and for intermittently making infrared light incident on the cell unit 30 and the detector unit 40. It is composed of a chopper 22.

The chopper 22 includes, for example, a two-blade rotary disk 23 and a rotary disk 23 having two notches formed by cutting out a part of the light source 21 to allow passage of light from the light source 21. It is composed of a rotating motor 24 and a rotating disk 23.
When the uncut portion (light-shielding portion) of the rotating disc 23 is located in front of the light source 21, the light source is rotated by rotating the motor 24 with the light source.
Infrared light from 21 is blocked, and when the cutout is located in front of the light source 21, the infrared light from the light source 21 passes,
Irradiate 30.

The cell part 30 is a part into which the sample gas is introduced, and the front and rear of the pipe 31 are sealed with an infrared permeable glass or a window plate 32 such as CaF ₂ which can transmit infrared rays in a wide spectrum range. A gas inlet / outlet hole 33 is provided on the side surface of the pipe 31 so that the gas can flow from one end to the other end, and its inner surface is mirror-finished or coated with gold or the like to efficiently reflect infrared light. There is.

The detector section 40 is generally composed of a front block which is a front chamber and a rear block which is a rear chamber made of metal such as aluminum. This is because the detector uses the NDIR principle to inject the infrared light to be measured that has passed through the cell into which the gas to be measured (sample gas) has been introduced to boost the pressure of the enclosed sensitive gas. FIG. 6 schematically shows the configuration required to form two chambers in the front and rear and to arrange a sensor such as a flow sensor for detecting a pressure difference between the front and rear chambers in a communication passage that communicates the front and rear chambers.

Through holes of the same diameter are formed in the front and rear blocks B1 and B2. In the figure, the opposite side of the joint surface between the through holes of the front block B1 and the front block B1 of the rear block B2 is shown. One end of the through hole is sealed with a window plate 43 that transmits infrared light, and when the front and rear blocks B1 and B2 are joined and integrated as shown in the figure, the through hole of the front block B1 is sealed. The window plate 43 'facing the rear block B2 to be stopped serves as a partition wall for the front chamber 41.
And the rear room 42.

The front block B1 and the rear block B2 are connected to each other when the blocks are joined and integrated to form a communication passage.
L-shaped channels (tunnels) 51 and 52 forming 44 are formed, and the L-shaped formed in the front block B1 is 90.
° The channel 51 rotated counterclockwise is inserted from the horizontal channel opening on the end surface (left side in the figure) of the front block B1 and communicates with the front chamber 41. Arrangement by bonding the sensor 60 to the vertical pore in the figure. The opening is sized to allow work, and the channel 51 forms a sensor chamber.

Further, in these two chambers 41 and 42, a reactive gas which is referred to as a sensitive gas and is an object to be measured by NDIR, for example, chemical species such as CO ₂ , SO ₂ , CO, NO _X and NH _{3 is used.} Alternatively, or a gas obtained by diluting this chemical species with an inert gas such as Ar, He, or N ₂ is filled (enclosed). Further, as the sensor 60 arranged in the communication passage 44, any sensor may be used as long as it can detect the pressure difference between the front and rear chambers.
In the case of a flow sensor that detects the flow of the enclosed gas in the communication passage 44 by the pressure difference between the front and rear chambers, generally, a thin film type hot wire type flow sensor manufactured by a small and highly accurate thin film technology is used. There is. In addition, the window plate 43 to the front and rear blocks B1, B2
Bonding of the front and rear blocks B1 and B2 is done with an adhesive,
Araltite AV138 (hardening agent HV998) (Nagase-Ciba)
It is adhered using an epoxy adhesive such as.

With such a structure, the infrared light emitted from the light source section 20 passes through the cell section 30 and is incident on the detector section 40. At this time, if the component gas to be measured is present inside the cell,
Depending on the gas concentration in the cell, part of the incident infrared light is absorbed by the gas in the cell, and the rest of the infrared light is detected by the detector unit.
Incident on 40. The infrared light incident from the front of the front chamber 41 of the detector unit 40 is absorbed by the front chamber 41 and the rear chamber 42,
Most of it is absorbed in the antechamber 41. The absorbed light energy will be converted into translational motion of the molecule, and
A pressure difference is generated between the first and the second pressure chambers 42, which causes a flow of the enclosed gas in the communication passage 44 that connects the two chambers.

Since the flow velocity of this gas flow depends on the intensity of light incident on the detector section 40, the communication passage 44 between the front and rear chambers 41 and 42 is formed.
By measuring as the resistance value change of the heat ray resistance element of the thin film type heat ray type flow sensor 60 arranged inside, the infrared light intensity before and after entering the detector section 40, that is, the concentration of the component gas to be measured in the cell It can be measured.

FIG. 7 is a schematic view of a thin-film hot wire type flow sensor 60 which is disposed in the communication passage 44 of the front and rear chambers 41 and 42 and detects the flow velocity of the gas flowing in the communication passage. As shown in the plan view, the basic structure is such that a glass substrate (length 5 mm × width 5 mm × thickness 0.25 mm) 61 serving as a base is formed with a 1 mm square opening 62 at the center, Same figure on both sides
As shown in the side view of (b), across the opening 62, a comb-shaped electrode (length 1.1 mm, width 15 to 25 μm, thickness 2 to 2 as a heat wire resistance element made of a metal having a large temperature coefficient of resistance such as Ni) is formed. 6
μm, surface anticorrosion Au coat) 63, 64 are formed (arranged) opposite to each other by thin film technology. This comb-shaped electrode (heat wire resistance element)
63 and 64 are combined with two external resistors to form a bridge circuit to measure the flow rate.

Including the comb-shaped electrodes 63 and 64, when a constant voltage is applied to the bridge circuit and the enclosed gas passes through the two electrodes 63 and 64, the resistance of the electrode serving as the heat ray resistance element on the windward side absorbs heat. As a result, the temperature decreases and the resistance value decreases. On the other hand, the resistance of the electrode as the heat ray resistance element on the leeward side is given the heat taken from the resistance element on the leeward side, and the temperature rises to increase the resistance value. An imbalance of this resistance causes a potential difference in the bridge circuit.
The flow velocity of the gas flowing inside can be measured.

FIG. 8 is a block diagram of a signal processing portion of a thin film type heat ray resistance type flow sensor 60 in NDIR. Two heat ray resistance elements are combined with two external resistors to form a bridge circuit, and the bridge as a sensor is formed. Since the signal obtained from the circuit is a gas flow pulse generated from the infrared intermittent light incident on the detector unit 40, a waveform having a different amplitude will be generated depending on the infrared light intensity. NDIR generally rectifies the waveform when measuring a sample (= sample gas) with an object to be measured and the waveform with an inert gas (= zero gas) without the object to be measured, and outputs the subtracted value as the output signal. Is outputting a DC signal as.

[0015]

This type of the above configuration
NDIR is essentially a constant output from the detector (sensor) in the detector section during long-term continuous operation (measurement) with zero gas introduced into the sample cell. That is, the detection sensitivity should be constant over time and should not change. However, when the applicant carried out long-term continuous operation by introducing zero gas and collected output data of the detector, the output signal of the detector gradually decreased with the passage of time and did not show a constant value.

FIG. 9 shows an NDIR equipped with a detector placed in a constant temperature bath at 25 ° C., and zero gas, N ₂ gas flow rate of 200 ml / min.
FIG. 3 is a characteristic diagram showing a change with time of an output signal of a detector when the device is introduced into the measurement cell and continuously operated. As can be seen in the figure, a large output fluctuation occurred for the first 6 hours, and then the output signal decline, that is, the sensitivity decline did not subside, and the sensitivity of the detector output continued to decline at a rate of 1 mV / ° C even after 10 days. It was

Therefore, as a result of repeated sharp experiments and studies by the applicant regarding the factor that the output signal of the detector decreases with the passage of time, in other words, the factor of decreasing the sensitivity with the passage of time, the cause is the assembly of the detector. At that time, it was found that there is an adhesive used for adhering the block, the window material, and the sensor, which are the constituent members thereof, and by using an acidic adhesive for adhering the constituent members of the detector, the sensitivity decrease can be remarkably improved, It was experimentally confirmed that stable measurement can be performed without deterioration in sensitivity over a long period of time.

That is, in order to find out the cause of the decrease in the sensitivity of the detector in NDIR, first, the bridge caused by the alteration (oxidation, grain boundary growth in the manufacturing process by the thin film technology, etc.) of the thin film type hot wire type flow sensor. Assuming that there is a change in circuit output, various analyzes and aging of flow sensors (electricity,
Various attempts were made at various temperatures, but none of them had any effect, and the decrease in sensitivity was not improved. Therefore, in assembling the detector, attention was paid to each constituent member, that is, the adhesive used for adhering the block as the detector main body and adhering the window material, the sensor and the like to the block.

The detector section (detector section) of the detector section of this type of NDIR has a sensitive gas (for example, CO 2) in the front and rear chambers.
₂ chemical species only, or this chemical species as Ar, He, N ₂
(Inert gas diluted with inert gas) is sealed, so the front and rear blocks are joined together, and each block is joined to the window plate, sensor, etc. Epoxy resin adhesive, usually a general industrial epoxy adhesive Arartite AV138 (hardener H
V998) (manufactured by Nagase-Ciba) is used.

Therefore, the characteristic diagram shown in FIG. 9 is the continuous operation of NDIR equipped with a detector assembled by adhering each component of the detector (block as detector body, window material, sensor) with Arartite AV138. It is a characteristic view which shows the time-dependent change of the output signal of the detector at the time of carrying out.

Araltite AV138 is an adhesive that uses a typical polyamidoamine-based curing agent. Since polyamidoamine is alkaline, the unreacted curing agent when it is cured is sensitive to the inside of the detector. It is assumed that CO ₂ which is a gas may adsorb or react with the alkaline component of the adhesive agent, lowering the CO ₂ gas concentration and lowering the sensitivity of the detector.

From this point of view, therefore, the detector components are bonded by an adhesive F202 manufactured by Tra-Con, Inc., USA, as an acidic adhesive to assemble the detector, and the detector is mounted on the NDIR to prepare a sample cell. When zero gas was introduced into the device for long-term continuous operation, it was found that the detector output did not change over a long period of time, in other words, there was no sensitivity decrease and stable measurement was possible, which was confirmed experimentally. . Figure 10 shows the aforementioned US
After the detector components were bonded and assembled with the adhesive F202 made by Tra-Con, an NDIR equipped with a detector containing a sensitive gas (CO ₂ + Ar) was placed at 25 ° C as in Fig. 9. FIG. 4 is a characteristic diagram showing a change with time of an output signal of the detector when the N ₂ gas is introduced as a zero gas into the measurement cell at a flow rate of 200 ml / min and the detector is operated to continuously operate in the constant temperature bath of FIG. .

As can be seen from the figure, the temperature was stable after the initial transition of 6 hours, and there was no change in the output for 10 days after the measurement, and a constant high sensitivity was maintained. this is,
By using an acidic adhesive, since the adhesive is also CO ₂ also both acidic is an internal seal gas detectors, CO ₂ adsorption,
It is considered that the reaction can be suppressed and a decrease in CO ₂ gas concentration can be prevented. In particular, the curing agent for the adhesive F202 manufactured by US Tra-Con Co., which is used, is carboxylic acid such as maleic anhydride or fluteic acid anhydride, which is a carboxylic acid, that is, carbonic acid, that is,
Since it is an acid that is stronger than CO ₂ which is a sensing gas, CO ₂ is difficult to be absorbed (penetrated) in the adhesive due to the property that weak acid is released when weak acid is mixed with strong acid. Conceivable.

As a result, the alkaline component of the adhesive and CO ₂
It can be seen that there is no error in the previous assumption that the CO ₂ gas concentration is reduced by the adsorption / reaction of and the sensitivity of the detector is reduced. It should be noted that the detector components are bonded with an acidic adhesive.
The applicant has already proposed NDIR as Japanese Patent Application No. 2000-383169.

[0025]

When the constituent members of the detector are assembled by bonding with an acidic adhesive, there is no change in the concentration (decrease in concentration) due to the adsorption reaction of the sensitive gas enclosed in the front and rear chambers with the adhesive. As a result, although an infrared gas analyzer capable of maintaining high sensitivity for a long period of time and stable measurement can be obtained without lowering the sensitivity of the detector, there are the following problems. CO
₂ Decrease gas concentration

That is, in the case of an adhesive which is an acidic curing agent such as a carboxylic acid curing agent, the curing process requires a high temperature of 100 ° C. or higher, and therefore the workability is lower than that of an alkaline amine curing agent that can be cured at room temperature. To do. In particular, a flow sensor made of a metal thin film having a thickness of several μm is not preferable in terms of durability, and there is a high possibility that the sensor will be damaged by thermal expansion and destroyed, and the yield as a detector is reduced.

The present invention was devised to solve the above-mentioned problems, and does not require a high temperature for the curing process during assembly (manufacturing) by bonding the detector with an adhesive, and It is an object of the present invention to provide an infrared gas analyzer capable of maintaining the sensitivity of the detector part at a high constant level for a long period of time without lowering the sensitivity with time and enabling stable measurement.

[0028]

In order to solve the above-mentioned problems, in the infrared gas analyzer of the present invention, each component constituting the detector of the detector, that is, the block as the detector main body or the window to the block. The feature is that the materials, sensors, etc. are assembled by bonding with a chemically stable low-reactivity adhesive. The adhesive is preferably an epoxy resin adhesive whose curing agent is a polyamidoamine compound that can be cured at low temperature.
It is preferable that the hot wire type flow sensor measures the flow velocity (flow rate) of the enclosed gas flow in the communication path based on the pressure difference between the chambers, and further that the gas enclosed in the front and rear two chambers is an acid gas. preferable.

As described above, when the chemically stable low-reactivity adhesive is used, the curing process can be performed at a relatively low temperature, and therefore thermal damage such as thermal expansion is not given to the sensor. It is possible to improve the sex. In addition, even if it is a polyamidoamine-based adhesive that can be cured at low temperature, by using one that is chemically stable to acids and alkalis, adsorption of the sensitive gas and adhesive inside the front and rear chambers It is possible to obtain an infrared gas analyzer capable of maintaining high sensitivity for a long period of time without causing a concentration change (reduction in sensitivity) due to a reaction, that is, a decrease in sensitivity of a detector, and performing stable measurement.

[0030]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below based on experimental results. Note that the NDIR itself, as described in FIG. 5, finally determines by measuring the intensity of infrared light that has passed through the light source part for generating infrared light, the cell part into which the sample is introduced, and the cell part. 3 is composed of a detector (detection) unit for measuring the sample concentration, and the detector unit is, as described in FIG. 6, connected with a thin-film heat wire type flow sensor having a heat wire resistance element. The thin-film hot-wire flow sensor is composed of two chambers connected to each other by a passage, and, as described with reference to FIG. 7, a glass substrate having an opening in the center and both surfaces of the glass plate. And a comb-shaped electrode as a heat ray resistance element (resistor) made of a metal having a large resistance temperature coefficient and formed (arranged) facing each other by a thin film technique across the opening.

FIG. 1 shows a structure of a detector part which is a main part of the present invention. (A) is a sectional view showing each constituent part before assembly, and (B) is a sectional view after assembly. It is a figure. From the left end face of the cylindrical body (block) 1 made of metal such as aluminum, a hole with a diameter φf is directed, and from the right end face, a countersunk hole with a diameter φf (φf <φb) larger than the diameter φf is directed toward the center. To form the through hole 2, and the step a is inevitably formed on the inner peripheral wall of the central portion of the through hole 2 of the block 1 due to the different diameters of the holes drilled from both end surfaces.

Further, in the second stage of the through holes 3 having different diameters in three stages, which are vertically communicated with the hole of diameter φf from the side surface of the block 1 with the step a portion as a boundary, and the hole 3 of diameter φb. An L-shaped tunnel 4 that communicates is formed by perforation. In the embodiment, the diameter φf is the same as the inner diameter of the pipe (31 in FIG. 5) forming the cell so that the block 1 forms a part of the cell portion.
5, a hole 5 communicating with the hole 5 and an insertion hole 6 serving as a measured gas introducing / extracting hole (33 in FIG. 5) communicating with the hole 5 are formed.

The step a is attached to the step a portion of the block 1 perforated in this way to form a partition wall of the front and rear chambers.
The CaF ₂ window plate 7 is a low temperature curable polyamidoamine-based adhesive that is chemically stable against acids and alkalis, for example, epoxy adhesive BB2 manufactured by Tra-Con of the United States.
Adhesion at 130, and then CaF ₂ which becomes a rear window of the cell by attaching the step to the step at the boundary between the hole 5 and the hole of diameter φf
The window cover 8 and the rear cover 9 are bonded to the countersunk portion of the hole of diameter φb with the chemically stable low-reactivity adhesive BB2130. This allows
The inside of the through hole 2 is divided into a front chamber 10 and a rear chamber 11.

Then, the thin-film hot-wire type flow sensor 12 is bonded to the bottom of the through hole 3 with a chemically stable low-reactivity adhesive BB2130, and the lid member 14 is chemically attached to the opening 3'of the through hole 3. Adhesively fixed with a low-reactivity adhesive BB2130 that is stable and closed tightly. As a result, the communication passage 15 between the front chamber 10 and the rear chamber 11 is formed to form the detector portion shown in FIG. The curing conditions for the adhesive BB2130 are 65 ° C. in air for 4 hours. Further, the window plate 7, 8 and the rear lid 9 are adhered to each other, and the through hole 3 is formed by the lid member 14 after the thin film type hot wire type flow sensor 12 is arranged.
Any of the adhesive closure to the opening 3'may be performed first. Further, the left end surface of the assembled block 1 of the detector unit is aligned with and joined to the end of a pipe (not shown) that constitutes a cell.

FIG. 2 shows another embodiment. Holes having a diameter φf and a diameter φb (φf> φb) are bored in the block 1 to form a bottomed hole 16, and the window plates 7 and 8 are formed at the step portions. Are bonded to each other with a chemically stable low-reactivity adhesive (for example, epoxy adhesive BB2130 manufactured by Tra-Con Inc. in the US) to form the front and rear chambers 10 and 11. According to this configuration, in FIG. The rear lid 9 is unnecessary. The inner surfaces of the through hole 2, the bottomed hole 16 and the hole 5 in FIGS. 1 and 2 are preferably buffed to a mirror finish or coated with gold or the like in order to efficiently reflect infrared light. Further, in FIGS. 1 and 2, 17 is a gas lead-in / out hole of the cell inserted and fixed in the insertion hole 6 (33 in FIG. 5).
It is a thin tube.

Next, the action of bonding the respective constituent members with the chemically stable low-reactivity adhesive will be described based on the experimentally measured results. Fig. 3 shows the NDIR equipped with the detector in which the sensing gas (CO ₂ + Ar) is enclosed after the detector components are assembled by bonding with the above-mentioned adhesive BB2130 manufactured by Tra-Con, USA. Similar to the acquisition of the characteristic chart of 10, put it in a constant temperature bath at 25 ℃ and use N ₂ gas as zero gas at a flow rate of 200 ml / min.
FIG. 4 is a characteristic diagram showing a change in output of the detector when the detector is operated after being introduced into the measurement cell in 1. and continuously operated for 10 days. As you can see in the figure, after a transition time of about 80h,
The output was stable, and there was no change in output over the 10 days after the measurement, and a high level of sensitivity was maintained.

FIGS. 4, 11, and 12 show that with the passage of time,
FIG. 4 is an analysis waveform diagram showing the analysis result of the adhesive composition performed in order to determine the cause of the decrease in the output of the detector. FIG. 4 shows the adhesive composition of the adhesive BB2130 manufactured by US Tra-Con Co. used in the examples. The analysis results are shown in Figure 11: Nagase-Ciba Araltite
FIG. 12 shows the results of analysis of the adhesive composition of AV138, and FIG. 12 shows the results of analysis of the adhesive composition of adhesive F202 manufactured by Tra-Con, Inc., which is an acidic adhesive. As is clear from these waveform diagrams, in the adhesive F202, the peak of the ester bond, which is a characteristic of the acidic epoxy resin adhesive, can be observed at a wavelength of 1732 cm ⁻¹ .
Adhesive AV138 shows an analytical waveform of an adhesive using a typical polyamidoamine-based curing agent.

On the other hand, although the adhesive BB2130 is a polyamidoamine-based adhesive having a composition similar to the adhesive using the polyamidoamine-based curing agent similar to AV138, it can be cured at a low temperature. It can be seen that it is chemically stable and has low reactivity. This enables low-temperature curing by adhering and assembling each component of the detector (block as detector body, window material to block, sensor, etc.) with adhesive BB2130, and sealed in the front and rear chambers. Concentration change (decreased sensitivity) due to adsorption reaction between sensitive gas and adhesive,
That is, as shown in the characteristic diagram of FIG. 3, it is possible to obtain an infrared gas analyzer capable of maintaining a high sensitivity for a long period of time without degrading the sensitivity of the detector and performing stable measurement.

Although the embodiment is the single-beam type NDIR, the present invention can be applied to the double-beam type NDIR. Further, in the embodiment, the front and rear two chambers and the communication passage that connects the two chambers are formed by perforating a single block and adhering a window plate or the like, but as in the conventional example shown in FIG. The same effect can be obtained even when applied to a detector in which is joined and integrated. However, if a detector having two chambers, front and rear, is constructed by punching a single block as in the embodiment, the airtightness can be secured and the number of parts can be reduced as compared with the case where two blocks are joined and integrated. It has excellent workability and can reduce the number of assembly steps due to processing and adhesion.

Further, in the embodiment, as the sensor for detecting the pressure difference between the front and rear chambers, the flow sensor for detecting the fluctuation of the gas pressure as the flow rate of the internal sensitive gas is used. It may be a pressure sensing element such as a membrane capacitor for detecting as. Even in this case,
Since the curing process can be performed at a low temperature, the sensor is not thermally damaged due to thermal expansion and the like, and is chemically stable. Therefore, the same effect as using the thin-film hot-wire flow sensor in the embodiment is obtained. Is obtained. However, the detector can be downsized by using the thin-film hot-wire flow sensor.

[0041]

According to the present invention, since a chemically stable low-reactivity adhesive is used for assembling the constituent members of the detector by bonding, the sensor can be cured at a low temperature. Since it does not cause thermal damage to the detector, the yield of the detector and the productivity can be improved without destroying the sensor. Further, there is no change in concentration (decrease in concentration) due to the adsorption reaction of the sensitive gas sealed in the front and rear chambers with the adhesive. As a result, since the detection sensitivity of the sensor does not decrease, it is possible to obtain an infrared gas analyzer capable of maintaining high sensitivity of the detector section for a long period of time and performing stable measurement.

[Brief description of drawings]

FIG. 1 is a cross-sectional view schematically showing a configuration of a detector part which is a main part of the present invention.

FIG. 2 is a sectional view schematically showing a configuration of a detector section according to another embodiment.

FIG. 3 is an output characteristic diagram of an NDIR detector equipped with the detector unit of FIG.

FIG. 4 FTIR of the chemically stable low-reactivity adhesive BB2130 used for adhesive assembly of the detector part in FIG.
It is a waveform diagram of the analysis result by.

FIG. 5 is a cross-sectional view schematically showing the configuration of a single beam type NDIR.

6 is a cross-sectional view schematically showing a configuration of a sensor unit of NDIR in FIG.

FIG. 7 is a schematic diagram showing a configuration of a thin-film hot-wire flow sensor.

FIG. 8 is a block diagram of a sensor output signal processing unit of the hot-wire flow sensor.

FIG. 9 is an output characteristic diagram of a detector of an NDIR equipped with a conventional detector unit.

FIG. 10 is an output characteristic diagram of an NDIR detector equipped with another conventional detector unit.

[Figure 11] FTI of alkaline epoxy adhesive AV138BB2130
It is a waveform diagram of the analysis result by R.

FIG. 12 is a waveform diagram of the FTIR analysis result of the acidic adhesive F202.

[Explanation of symbols]

1: Block 2: Through hole 3: Through hole (3 '... opening) 4: Tunnel 5: Hole 6: Insertion hole 7, 8: Window plate 9: Rear lid 10: Front chamber 11: Rear chamber 12: Thin film type heat wire Flow sensor 13: Lid member 14: Lid member 15: Communication passage 16: Bottomed hole 17: Capillary tube

Claims (4)

[Claims] 1. A measurement cell, a light source section arranged on one end side of the measurement cell, and a detection section arranged on the other end side of the measurement cell for detecting the intensity of infrared light passing through the measurement cell. An infrared gas analyzer having two detector front and rear chambers filled with gas, a communication passage communicating these two chambers, and a sensor arranged in the communication passage for detecting a pressure difference between the two chambers. In addition, an infrared gas analyzer characterized in that the constituent members of the detection unit are bonded and assembled with a chemically stable low-reactivity adhesive. 2. The infrared gas analyzer according to claim 1, wherein the adhesive is an epoxy resin adhesive in which the curing agent is a polyamidoamine compound capable of curing at low temperature. Infrared gas analyzer. 3. The infrared gas analyzer according to claim 1 or 2, wherein the sensor measures the flow velocity of the gas flow in the communication passage based on the pressure difference between the two chambers. An infrared gas analyzer characterized by being a sensor. 4. The infrared gas analyzer according to claim 1, wherein the gas enclosed in the front and rear chambers is an acid gas.