Gas measuring device

Abstract

The present invention provides a gas measuring device. The gas measuring device comprises: a sample gas chamber; a light source; a detection unit that detects the intensity of light transmitted through the sample gas chamber; and a CPU that repeatedly analyzes the gas components in the sample gas. The detection unit includes: a first detector that detects the gas component to be analyzed; and a plurality of second detectors that detect a plurality of components used for interference correction of the gas component to be analyzed. The interface circuit includes: a preprocessing circuit that preprocesses the detection signal of the first detector in a manner that can be input to the CPU and sends it to the CPU; and a second signal processing unit that preprocesses the detection signal of the second detector in a manner that can be input to the CPU and sends it to the CPU in sequence in a time-sharing manner. This can suppress development costs and improve accuracy.

Description

Technical Field

[0001] The present disclosure relates to a gas measuring device. Background Art

[0002] Japanese Patent Publication No. 9-49797 discloses an infrared gas analyzer that switches between a sample gas and a reference gas to measure the concentration of a gas component. In the infrared gas analyzer, a three-way valve is switched to alternately supply the sample gas and the reference gas to a gas chamber at a predetermined period. In parallel, a fan-shaped member is rotated by a motor to intermittently irradiate the gas chamber with infrared light from a light source, so that a detector can alternately detect infrared light that has passed through the sample gas or the reference gas, and analyze the gas components based on the output ratio of the detection output of the reference gas to the detection output of the sample gas. Summary of the invention

[0003] The infrared gas analyzer disclosed in Japanese Patent Application Laid-Open No. 9-49797 is an instrument for detecting the concentration of SO2 in the sample gas. However, the environmental standard is not only defined by SO2, but also by CO, CO2, NO x etc., so there are regulations on CO, CO2, NO in addition to SO2 x Therefore, a multi-component measuring instrument capable of measuring multiple gas components has been developed.

[0004] In order to measure a plurality of gas components, such as SO 2 , CO, CO 2 , and NO, four detectors and a CPU (Central Processing Unit) having at least four ports for receiving output signals from these detectors are required.

[0005] In recent years, in order to further improve the detection accuracy, it is required to detect the components that interfere with the gas to be detected and correct the detection results in addition to detecting the gas components as the detection object. However, in order to improve the previous device for use, the CPU input port is often insufficient. However, in order to change the CPU to design and manufacture a new device, it will cost a huge development cost.

[0006] An object of the present disclosure is to provide a gas measuring device capable of suppressing development costs and improving accuracy.

[0007] The gas measuring device disclosed in the present invention comprises: a sample gas chamber filled with a sample gas; a light source irradiating light to the sample gas chamber; a detection unit detecting the light intensity after the light irradiated from the light source to the sample gas chamber passes through the sample gas chamber; a central processing unit repeatedly analyzing the gas components in the sample gas based on the detection results of the detection unit; and an interface circuit sending the detection signal detected by the detection unit to the central processing unit. The detection unit includes: a first detector detecting the gas component as the analysis object in the sample gas; and a plurality of second detectors detecting a plurality of components used for interference correction of the gas component as the analysis object. The interface circuit includes: a first signal processing unit preprocessing the detection signal of the first detector in a manner that can be input to the central processing unit and sending it to the central processing unit; and a second signal processing unit preprocessing the detection signals of the plurality of second detectors in a manner that can be input to the central processing unit and sending them to the central processing unit in sequence in a time-sharing manner.

[0008] The gas measuring device disclosed in the present invention only needs to change a part of the signal processing unit of the existing structure, so there is no need to change the central processing unit, and the development time is also small. In addition, it is also easy to improve the accuracy of the existing device.

[0009] The above objects, features, aspects and advantages and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 This is a diagram schematically showing the overall configuration of the gas measuring device according to this embodiment.

[0011] Figure 2 It is shown Figure 1 FIG. 1 is a block diagram of the structure of the control device 30.

[0012] Figure 3 This is a diagram for explaining signals input to each port of the CPU. DETAILED DESCRIPTION

[0013] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, the same reference numerals are given to the same or corresponding parts in the drawings, and their description will not be repeated.

[0014] Figure 1 This is a diagram schematically showing the overall configuration of the gas measuring device according to this embodiment. Figure 1 The gas measuring device 1 shown includes a sample gas line ML, a reference gas line RL, a switching valve 5 , and a sample gas cell 9 .

[0015] The sample gas M is introduced into the sample gas line ML. The sample gas line ML includes a filter 2 through which the sample gas M passes, a pump 3 for sending the sample gas M, and a needle valve 4 for adjusting the flow rate of the sample gas M.

[0016] The reference gas R is introduced into the reference gas line RL. The reference gas line RL includes a filter 12 through which the reference gas R passes, a pump 13 for delivering the reference gas R, and a needle valve 14 for adjusting the flow rate of the reference gas R.

[0017] The switching valve 5 includes a three-way valve 5M disposed in the sample gas line ML and a three-way valve 5R disposed in the reference gas line RL. The three-way valves 5M and 5R form a flow path in such a manner that, according to a selection signal SEL, the gas passing through one of the reference gas line RL and the sample gas line ML is sent to the sample gas chamber 9, and the gas passing through the other is discharged. By switching the selection signal SEL, the reference gas and the sample gas are alternately filled into the sample gas chamber.

[0018] The gas measuring device 1 further includes a motor 6 , a sector 8 , a light source 7 , a detection unit 20 , and a control device 30 .

[0019] The sample gas chamber 9 has a gas inlet 9a and a gas outlet 9b. The sample gas or the reference gas is supplied from the gas inlet 9a into the sample gas chamber 9 via the switching valve 5, and is discharged from the gas outlet 9b. A light source 7 for emitting infrared light is provided at one end of the sample gas chamber 9, and a detection unit 20 for detecting infrared light transmitted through the sample gas chamber 9 is provided at the other end of the sample gas chamber 9.

[0020] A fan-shaped member 8 for blocking infrared light is provided between the light source 7 and the end of the sample gas chamber 9. The fan-shaped member 8 has a light-shielding portion and a light-transmitting portion. The fan-shaped member 8 is configured to rotate around the fan-shaped member rotation axis 8e. When the light-transmitting portion is on the sample gas chamber 9, infrared light is irradiated into the sample gas chamber 9, and when the light-shielding portion is on the sample gas chamber 9, irradiation of infrared light into the sample gas chamber 9 is cut off. The control device 30 controls the rotation position of the fan-shaped member 8 through the motor 6, and further, controls the drive of the switching valve 5 in synchronization with the rotation of the motor 6 according to the selection signal SEL.

[0021] The detection unit 20 includes a first detector 21 for detecting a gas to be measured and a second detector for detecting a calibration gas. The first detector 21 includes a SO2 detector 22 for detecting SO2, a NO detector 23 for detecting NO, and a CO detector 24 for detecting CO. The second detector includes a CO2 detector 25 for detecting CO2 and a CH4 detector 26 for detecting CH4.

[0022] SO2, NO, and CO absorb light of specific wavelengths in the infrared region (SO2: 7.4 μm, NO: 5.3 μm, CO: 4.6 μm). Therefore, if the absorption of infrared light after passing through the measurement gas is measured using a detector that is sensitive only to each of these wavelengths, the concentration of each component can be measured.

[0023] Each detector has the detection target gas in the sample gas sealed inside it, and detects the infrared light intensity of the frequency inherent to the detection target gas according to the internal pressure change. Then, the control device 30 that receives the detection output of the detection unit 20 performs a predetermined signal processing and calculates a concentration value representing the concentration of the measurement gas in the sample gas.

[0024] Figure 2 It is shown Figure 1 A block diagram of the structure of the control device 30 is shown. Figure 1 and Figure 2 The structure of the gas measuring device 1 including the internal structure of the control device 30 will be described.

[0025] The gas measuring device 1 comprises: a sample gas chamber 9; a switching valve 5, which selectively supplies a reference gas and a sample gas to the sample gas chamber; a light source 7, which irradiates light to the sample gas chamber; and a detection unit 20, which detects the light intensity of the light irradiated from the light source 7 to the sample gas chamber 9 after passing through the sample gas chamber 9.

[0026] The gas measuring device 1 further includes a control device 30. The control device 30 includes an interface circuit 36, a computing unit (CPU) 31, a storage unit (memory) 32, a concentration display unit 33, an input unit 34, and an output unit 35. The user performs input for calibration, setting, etc. via the input unit 34. In addition, the CPU 31 outputs the concentration value, etc. from the output unit 35.

[0027] The interface circuit 36 ​​transmits the detection signal detected by the detection unit 20 to the CPU 31. The CPU 31 repeatedly analyzes the gas components in the sample gas based on the detection result of the detection unit 20.

[0028] The detection unit 20 includes: a first detector 21, which detects gas components (SO2, NO, CO) as an analysis object; and a CO2 detector 25 and a CH4 detector 26, which respectively detect a plurality of components (CO2, CH4) used for interference correction of the gas components as the analysis object. The interface circuit 36 ​​includes: a first signal processing unit (41, 42, 43), which pre-processes the detection signal of the first detector 21 in a manner that can be input to the CPU 31 and sends it to the CPU 31; and a second signal processing unit (44), which pre-processes the detection signals of the CO2 detector 25 and the CH4 detector 26 in a manner that can be input to the CPU 31, and sends them to the CPU 31 alternately in a time-sharing manner.

[0029] The light irradiated to the sample gas cell by the light source 7 is infrared light. In addition, even a gas measuring device using ultraviolet light can alternately transmit the calibration component in a time-division manner similarly to the present embodiment.

[0030] The gas components to be analyzed include SO2 gas, NO gas, and CO gas. The first detector 21 includes a SO2 detector 22, a NO detector 23, and a CO detector 24. The multiple components used for interference correction include CH4 gas and CO2 gas. The CPU 31 has a first port P1, a second port P2, a third port P3, and a fourth port P4.

[0031] The first signal processing unit (41, 42, 43) has: a first preprocessing circuit 41, which preprocesses the output signal of the SO2 detector 22 and outputs it to the first port P1; a second preprocessing circuit 42, which preprocesses the output signal of the NO detector 23 and outputs it to the second port P2; and a third preprocessing circuit 43, which preprocesses the output signal of the CO detector 24 and outputs it to the third port P3.

[0032] The second signal processing unit 44 is configured to alternately output a signal obtained by preprocessing the output signal of the CH4 detector 26 and a signal obtained by preprocessing the output signal of the CO2 detector 25 to the fourth port P4.

[0033] The first preprocessing circuit 41 includes an analog circuit 51 that adjusts the gain of the output signal of the SO2 detector 22 and a conversion circuit 52 that converts the output of the analog circuit 51 so that it can be input to the first port P1.

[0034] The second preprocessing circuit 42 includes an analog circuit 53 that adjusts the gain of the output signal of the NO detector 23 and a conversion circuit 54 that converts the output of the analog circuit 53 so that it can be input to the second port P2.

[0035] The third preprocessing circuit 43 includes an analog circuit 55 that adjusts the gain of the output signal of the CO detector 24 and a conversion circuit 56 that converts the output of the analog circuit 55 so that it can be input to the third port P3.

[0036] The second signal processing unit 44 includes: a second analog circuit 58, which adjusts the gain of the output signal of the CH4 detector 26; a third analog circuit 57, which adjusts the gain of the output signal of the CO2 detector 25; a multiplexer 59, which alternately selects the output of the second analog circuit 58 and the output of the third analog circuit 57; and a second conversion circuit 60, which converts the output of the multiplexer 59 in a manner that can be input to the fourth port P4.

[0037] With the above-described configuration, in the present embodiment, the signal of the CO 2 detector 25 and the signal of the CH 4 detector are alternately switched in time and input to one port P4 , and the CO 2 concentration and the CH 4 concentration are calculated respectively.

[0038] CO2 and CH4 are both measurement targets for interference correction, and are not the atmospheric pollutants SO2 and NO that are the main measurement targets, or CO that is the measurement target for incomplete combustion monitoring as a dioxin countermeasure. Therefore, for CO2 and CH4, even if the minimum detection limit is slightly increased (about 1.4 times) by eliminating the signal from the detector and performing concentration calculation, it does not hinder gas measurement.

[0039] Figure 3 31 is a diagram for explaining the signals input to each port of the CPU. Ports P1 to P3 of the CPU 31 continuously receive signals from the corresponding detectors without switching. The control device 30 performs switching of the switching valve 5 twice within a period of 20 seconds in one cycle by selecting the signal SEL. In the first half of the cycle of 20 seconds, a detection signal is input when the reference gas R from the reference gas line RL is filled into the sample gas chamber 9, and in the second half of the cycle, a detection signal is input when the sample gas chamber 9 is filled with the sample gas M from the sample gas line ML.

[0040] exist Figure 3 In the above, R represents the detection signal (reference signal) when the reference gas is filled in the sample gas chamber 9, and M represents the detection signal (measurement signal) when the sample gas is filled in the sample gas chamber 9. The CPU 31 calculates the concentration of the measurement target gas in the sample gas by applying the reference signal and the measurement signal to a predetermined calculation formula.

[0041] The port P4 receives the signal from the CO2 detector 25 and the signal from the CH4 detector 26 in a switching manner every 20 seconds. The CPU 31 uses the selection signal SEL2, such as Figure 3 The A input and the B input of the multiplexer 59 are selected as shown. The selection signal SEL2 has a period twice that of the selection signal SEL of the switching valve 5. For CO2 and CH4 used for interference correction, the CPU 31 also calculates the concentration of the measurement target gas in the sample gas by applying the reference signal and the measurement signal to the prescribed calculation formula. The frequency at which the concentration is updated is half of the update frequency of SO2, NO, and CO, which are the main analysis objects. In addition, in the present embodiment, the selection signal SEL2 is output from the CPU 31, but it is also possible to generate SEL2 in the second signal processing unit 44 using the selection signal SEL by providing a frequency dividing circuit in the second signal processing unit 44.

[0042] The CPU 31 corrects the concentrations of SO 2 , NO, and CO updated every 20 seconds on the basis of the concentrations of CO 2 and CH 4 updated every 2 cycles of 40 seconds.

[0043] It is also easy to realize the gas measuring device of this embodiment by improving the existing gas measuring device. For example, in a device that replaces the second signal processing unit 44 and uses the same structure as the preprocessing circuits 41 to 43 to perform only the correction of CO as an interference component but does not perform the correction of CH4 as an interference component, if each preprocessing circuit 41 is composed of a replaceable substrate, it is only necessary to replace one of the existing substrates with the substrate of the second signal processing unit 44 and change the calculation processing of the CPU 31 by changing the software, so that the correction of CH4 as an interference component can be introduced.

[0044] In this case, since it is easy to modify the existing delivered items, the device modification time only takes about half a day, so the measurement time can be shortened, thereby also reducing the man-hours of the service personnel.

[0045] In addition, in the above-described embodiment, the case where there are three gas components as the detection object and two gas components for interference correction is described, but their numbers can also be changed. The gas components as the detection object can also be one to two and four or more. In addition, the gas components for interference correction can also be three or more. Even in this case, one port is used for each gas component as the detection object. By sequentially inputting the gas components for interference correction into one port of the CPU in a time-sharing manner, the number of ports used can be reduced.

[0046] In addition, in the present embodiment, an infrared gas analyzer using a reference gas is described, but the same idea can also be applied to an infrared gas analyzer that does not use a reference gas but performs concentration calculations only based on the measurement signal of the sample gas, and an infrared gas analyzer that does not circulate a reference gas but uses a reference gas chamber obtained by filling and sealing the gas chamber.

[0047] [Way]

[0048] It will be understood by those skilled in the art that the above-described exemplary embodiments are specific examples of the following aspects.

[0049] (First Item)

[0050] The gas measuring device disclosed in the present invention comprises: a sample gas chamber filled with a sample gas; a light source irradiating light to the sample gas chamber; a detection unit detecting the light intensity of the light irradiated from the light source to the sample gas chamber through the sample gas chamber; a central processing unit repeatedly analyzing the gas components in the sample gas based on the detection results of the detection unit; and an interface circuit transmitting the detection signal detected by the detection unit to the central processing unit 31. The detection unit includes: a first detector detecting the gas component to be analyzed in the sample gas; and a plurality of second detectors detecting a plurality of components for interference correction used for interference correction of the gas component to be analyzed. The interface circuit includes: a first signal processing unit preprocessing the detection signal of the first detector in a manner that can be input to the central processing unit and transmitting it to the central processing unit; and a second signal processing unit preprocessing the detection signals of the plurality of second detectors in a manner that can be input to the central processing unit and transmitting them sequentially in a time-division manner to the central processing unit. By setting such a structure, even when the central processing unit has few input ports, the detection results of the plurality of components for interference correction can be processed by the central processing unit.

[0051] (Second item) Preferably, the light irradiated by the light source toward the sample gas cell is infrared light.

[0052] (Item 3) It is more preferred that the gas components to be analyzed include SO2 gas, NO gas, and CO gas. The first detector includes a SO2 detector, a NO detector, and a CO detector. The multiple components used for interference correction include CH4 gas and CO2 gas. The multiple second detectors include a CH4 detector and a CO2 detector. The central processing unit has a first port, a second port, a third port, and a fourth port. The first signal processing unit has: a first preprocessing circuit, which preprocesses the output signal of the SO2 detector and outputs it to the first port; a second preprocessing circuit, which preprocesses the output signal of the NO detector and outputs it to the second port; and a third preprocessing circuit, which preprocesses the output signal of the CO detector and outputs it to the third port. The second signal processing unit is configured to alternately output the signal obtained by preprocessing the output signal of the CH4 detector and the signal obtained by preprocessing the output signal of the CO2 detector to the fourth port.

[0053] (Item 4) More preferably, the first to third preprocessing circuits each include: a first analog circuit that adjusts the gain of the output signal of the corresponding detector; and a first conversion circuit that converts the output of the first analog circuit in a manner that can be input to the corresponding port among the first to third ports. The second signal processing unit includes: a second analog circuit that adjusts the gain of the output signal of the CH4 detector; a third analog circuit that adjusts the gain of the output signal of the CO2 detector; a multiplexer that alternately selects the output of the second analog circuit and the output of the third analog circuit; and a second conversion circuit that converts the output of the multiplexer in a manner that can be input to the fourth port.

[0054] Although the embodiments of the present invention have been described, the embodiments disclosed this time should be considered to be illustrative in all aspects and not restrictive. The scope of the present invention is indicated by the claims, and it is intended to include all modifications within the meaning and scope equivalent to the claims.

Claims

1. A gas measuring device comprising: a sample gas chamber filled with a sample gas; a light source for irradiating light toward the sample gas chamber; a detection unit configured to detect the light intensity of the light irradiated from the light source to the sample gas cell after passing through the sample gas cell; a central processing unit that repeatedly analyzes gas components in the sample gas based on the detection result of the detection unit; as well as an interface circuit that sends the detection signal detected by the detection unit to the central processing unit, in, The detection unit comprises: a first detector for detecting a gas component to be analyzed in the sample gas; and a plurality of second detectors for detecting a plurality of components for interference correction used for interference correction of the gas component to be analyzed, The interface circuit comprises: a first signal processing unit that pre-processes the detection signal of the first detector so that it can be input to the central processing device, and sends the pre-processed signal to the central processing device; and The second signal processing unit pre-processes the detection signals of the plurality of second detectors in a manner such that the detection signals can be input into the central processing device, and sends the detection signals to the same input port of the central processing device in sequence in a time-sharing manner.

2. The gas measuring device according to claim 1, characterized in that: The light irradiated by the light source toward the sample gas cell is infrared light.

3. The gas measuring device according to claim 2, characterized in that: The gas components to be analyzed include SO2 gas, NO gas and CO gas. The first detector includes a SO2 gas detector, a NO gas detector and a CO gas detector, The multiple components used for interference correction include CH4 gas and CO2 gas, The plurality of second detectors include a CH4 gas detector and a CO2 gas detector, The central processing unit has a first port, a second port, a third port and a fourth port, The first signal processing unit comprises: a first preprocessing circuit, which preprocesses the output signal of the SO2 gas detector and outputs it to the first port; a second preprocessing circuit, which preprocesses the output signal of the NO gas detector and outputs it to the second port; as well as a third preprocessing circuit, which preprocesses the output signal of the CO gas detector and outputs it to the third port, The second signal processing unit is configured to alternately output a signal obtained by preprocessing the output signal of the CH4 gas detector and a signal obtained by preprocessing the output signal of the CO2 gas detector to the fourth port.

4. The gas measuring device according to claim 3, characterized in that: The first to third preprocessing circuits each include: a first analog circuit that adjusts the gain of the output signal of the corresponding detector; and a first conversion circuit that converts the output of the first analog circuit so that it can be input to a corresponding port among the first port to the third port; The second signal processing unit includes: a second analog circuit, which adjusts the gain of the output signal of the CH4 gas detector; a third analog circuit, which adjusts the gain of the output signal of the CO2 gas detector; a multiplexer that alternately selects an output of the second analog circuit and an output of the third analog circuit; and The second conversion circuit converts the output of the multiplexer in a manner such that the output can be input to the fourth port.

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