JP2022186267A - gas measuring device - Google Patents

Abstract

To provide a gas measuring device capable of improving accuracy while suppressing development costs.SOLUTION: A gas measuring device 1 includes: a sample cell 9; a light source 7; a detection unit 20 that detects the intensity of light transmitting through the sample cell 9; and a CPU 31 that repeatedly analyzes gas components in sample gas. The detection unit 20 includes: a first detector 21 that detects a gas component to be analyzed; and a plurality of second detectors 25 and 26 that detect a plurality of components for interference correction of the gas component to be analyzed. An interface circuit 36 includes: preprocessing circuits 41, 42, and 43 that pre-process a detection signal of the first detector 21 so that the detection signal can be input to the CPU 31, and transmit it to the CPU 31; and a second signal processing unit 44 that pre-processes detection signals of the detectors 25 and 26 so that the detection signals can be input to the CPU 31, and sequentially transmit them to the CPU 31 in a time division manner.SELECTED DRAWING: Figure 2

Description

The present disclosure relates to gas measurement devices.

Japanese Patent Application Laid-Open No. 9-49797 (Patent Document 1) discloses an infrared gas analyzer that measures the concentration of gas components by switching between a sample gas and a reference gas. In this infrared gas analyzer, a three-way valve is switched to alternately supply the sample gas and the reference gas into the cell at predetermined intervals. In parallel with this, the sector is rotated by the motor, and the infrared light from the light source is intermittently irradiated into the cell. As a result, the detector alternately detects the infrared light that has passed through the sample gas or the reference gas, and the gas components can be analyzed based on the output ratio between the detection output of the reference gas and the detection output of the sample gas.

JP-A-9-49797

The infrared gas analyzer disclosed in JP-A-9-49797 mentioned above detects the concentration of SO ₂ in the sample gas, but it also detects CO, CO ₂ , NOx, etc. in addition to SO ₂ . , environmental standards have been established and there is a need to monitor concentrations. Therefore, multi-component instruments have also been developed that are capable of measuring multiple gas components.

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

In recent years, in order to further improve the detection accuracy, it is required to detect, in addition to the gas components to be detected, components that interfere with the gas to be detected, and to correct the detection results. However, in order to retrofit the existing devices, there is often a shortage of CPU input ports. However, designing and manufacturing a new device by changing the CPU requires a large amount of development cost.

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

The gas measuring device of the present disclosure includes a sample cell filled with a sample gas, a light source for irradiating the sample cell with light, and a detection unit for detecting the light intensity of the light emitted from the light source to the sample cell and transmitted through the sample cell. a central processing unit for repeatedly analyzing the gas components in the sample gas based on the detection result of the detecting unit; and an interface circuit for transmitting a detection signal detected by the detecting unit to the central processing unit. The detection unit includes a first detector that detects a gas component to be analyzed in the sample gas, and a plurality of second detectors that detect a plurality of components for interference correction of the gas component to be analyzed. The interface circuit includes a first signal processing unit that preprocesses the detection signals of the first detector so that they can be input to the central processing unit and transmits them to the central processing unit; and a second signal processing unit for performing preprocessing so that the signals can be input to the central processing unit and sequentially transmitting the signals to the central processing unit in a time division manner.

Since the gas measuring device according to the present disclosure requires only part of the signal processing unit to be changed in the existing configuration, there is no need to change the central processing unit, and the number of man-hours required for development can be reduced. It is also easy to modify existing equipment to improve accuracy.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows roughly the structure of the whole gas measuring apparatus of this Embodiment. 2 is a block diagram showing the configuration of a control device 30 of FIG. 1; FIG. FIG. 2 is a diagram for explaining signals input to each port of a CPU; FIG.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The same or corresponding parts in the drawings are denoted by the same reference numerals, and the description thereof will not be repeated.

FIG. 1 is a diagram schematically showing the overall configuration of the gas measuring device of this embodiment. A gas measuring device 1 shown in FIG. 1 includes a sample gas line ML, a reference gas line RL, a switching valve 5 and a sample cell 9 .

A 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 out the sample gas M, and a needle valve 4 for adjusting the flow rate of the sample gas M.

A 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 that delivers the reference gas R, and a needle valve 14 that adjusts the flow rate of the reference gas R.

The switching valve 5 includes a three-way valve 5M arranged in the sample gas line ML and a three-way valve 5R arranged in the reference gas line RL. The three-way valves 5M and 5R configure flow paths so that the gas that has passed through either the reference gas line RL or the sample gas line ML is sent to the sample cell 9 and the gas that has passed through the other is exhausted according to the selection signal SEL. do. By switching the selection signal SEL, the sample cell is alternately filled with the reference gas and the sample gas.

The gas measuring device 1 further includes a motor 6 , a sector 8 , a light source 7 , a detector 20 and a controller 30 .

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

A sector 8 is provided between the light source 7 and the end of the sample cell 9 for interrupting infrared light. This sector 8 has a light-shielding portion and a light-transmitting portion. The sector 8 is configured to rotate around the sector rotation axis 8c. Infrared light is irradiated into the sample cell 9 when the light-transmitting portion is above the sample cell 9, and irradiation of infrared light into the sample cell 9 is blocked when the light-shielding portion is above the sample cell 9. . The control device 30 controls the rotational position of the sector 8 via the motor 6 and also controls the drive of the switching valve 5 by the selection signal SEL so as to be synchronized with the rotation of the motor 6 .

The detection unit 20 includes a first detector 21 that detects the gas to be measured and a second detector that detects the correction gas. The _first detector 21 includes an SO2 detector 22, an NO detector 23, and a CO detector 24, which detect SO2, NO, and CO, respectively. The second detector includes a CO2 detector 25 and a CH4 detector 26 that detect _CO2 and CH4, _respectively .

SO ₂ , NO, and CO each absorb light of specific wavelengths in the infrared region (SO ₂ : 7.4 μm, NO: 5.3 μm, CO: 4.6 μm). Therefore, the concentration of each component can be measured by measuring the infrared absorption after passing through the measurement gas with a detector that is sensitive only to each of these wavelengths.

Each detector has a gas to be detected in the sample gas sealed therein, and detects the intensity of infrared light at a frequency unique to the gas to be detected based on internal pressure changes. Then, the controller 30, which receives the detection output from the detector 20, performs predetermined signal processing to calculate a concentration value indicating the concentration of the measured gas in the sample gas.

FIG. 2 is a block diagram showing the configuration of the control device 30 of FIG. 1. As shown in FIG. The configuration of the gas measuring device 1 including the internal configuration of the control device 30 will be described with reference to FIGS. 1 and 2. FIG.

The gas measurement apparatus 1 includes a sample cell 9, a switching valve 5 for selectively supplying a reference gas and a sample gas to the sample cell, a light source 7 for irradiating the sample cell with light, and a light source 7 for irradiating the sample cell 9 with light. A detection unit 20 is provided for detecting the intensity of the emitted light transmitted through the sample cell 9 .

The gas measuring device 1 further includes a control device 30 . The control device 30 includes an interface circuit 36 , a computing section (CPU) 31 , a storage section (memory) 32 , a density display section 33 , an input section 34 and an output section 35 . The user performs input for calibration, setting, etc. via the input unit 34 . The CPU 31 also outputs density values and the like from the output unit 35 .

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 section 20 .

The detection unit 20 includes a first detector 21 for detecting gas components (SO ₂ , NO, CO) to be analyzed, and a plurality of components (CO ₂ , CH ₄ ) for interference correction of the gas components to be analyzed. Detecting CO2 detector 25 and CH4 detector 26 are included. The interface circuit 36 includes a first signal processing unit (41, 42, 43) that preprocesses the detection signal of the first detector 21 so that it can be input to the CPU 31 and transmits it to the CPU 31, a CO2 detector 25 and a CH4 detector. and a second signal processing section (44) that pre-processes the detection signals of 26 so that they can be input to the CPU 31 and alternately transmits them to the CPU 31 in a time division manner.

The light with which the light source 7 irradiates the sample cell is infrared light. It should be noted that, even in a gas measuring device using ultraviolet light, it is possible to alternately transmit correction components in a time-division manner as in the present embodiment.

Gas components to be analyzed include _SO2 gas, NO gas, and CO gas. First detector 21 includes SO 2 detector 22 , NO detector 23 and CO detector 24 . The multiple components 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.

First signal processing units (41, 42, 43) include a first preprocessing circuit 41 that preprocesses the output signal of the SO2 detector 22 and outputs it to the first port P1, and a first preprocessing circuit 41 that preprocesses the output signal of the NO detector 23. It has a second preprocessing circuit 42 that processes the signal and outputs it to the second port P2, and a third preprocessing circuit 43 that preprocesses the output signal of the CO detector 24 and outputs it to the third port P3.

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. be.

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.

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.

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.

The second signal processing unit 44 includes a second analog circuit 58 that adjusts the gain of the output signal of the CH4 detector 24, a third analog circuit 57 that adjusts the gain of the output signal of the CO2 detector 25, and a second analog circuit. 58 and the output of the third analog circuit 57 alternately, and a second conversion circuit 60 for converting the output of the multiplexer 59 so that it can be input to the fourth port P4.

With the configuration as described above, in the present embodiment, the signal from the CO2 detector 25 and the signal from the CH4 detector are alternately switched temporally and taken into one port P4 to obtain the _CO2 concentration and the _CH4 concentration. are calculated respectively.

Both CO ₂ and CH ₄ are measurement targets for interference correction, and are not the air pollutant components SO ₂ and NO, which are the main targets of measurement, or CO, which is the measurement target for monitoring incomplete combustion as a countermeasure against dioxins. Therefore, for CO ₂ and CH ₄ , even if the signal from the detector is thinned out for concentration calculation and the minimum detection limit is slightly increased (approximately 1.4 times), there is no problem in gas measurement.

FIG. 3 is a diagram for explaining signals input to each port of the CPU. Ports P1-P3 of CPU 31 continuously receive signals from corresponding detectors without switching. The control device 30 switches the switching valve 5 twice in one cycle of 20 seconds according to the selection signal SEL. In the first half of one cycle of 20 seconds, a detection signal when the sample cell 9 is filled with the reference gas R from the reference gas line RL is input. A detection signal is input when 9 is filled.

In FIG. 3, R indicates the detection signal (reference signal) when the sample cell 9 is filled with the reference gas, and M indicates the detection signal (measurement signal) when the sample cell 9 is filled with the sample gas. 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 arithmetic expression.

The port P4 receives the signal from the CO2 detector 25 and the signal from the CH4 detector 26 by switching every 20 seconds per cycle. The CPU 31 selects the A input and the B input of the multiplexer 59 as shown in FIG. 3 using the selection signal SEL2. The selection signal SEL2 has a period twice as long as that of the selection signal SEL for the switching valve 5. FIG. The CPU 31 also applies the reference signal and the measurement signal to a predetermined arithmetic expression for CO ₂ and CH ₄ for interference correction, thereby calculating the concentration of the gas to be measured in the sample gas. The frequency at which this concentration is updated is half that of SO ₂ , NO, and CO, which are the main objects of analysis. In the present embodiment, the selection signal SEL2 is output from the CPU 31, but by providing a frequency dividing circuit in the second signal processing section 44, the selection signal SEL2 is used in the second signal processing section 44. SEL2 can also be made.

The CPU 31 corrects the concentrations of SO ₂ , NO, and CO, which are updated every 20 seconds for one cycle, by the concentrations of CO ₂ and CH ₄ , which are updated every 40 seconds for two cycles.

The gas measuring device of this embodiment can also be easily realized by modifying an existing gas measuring device. For example, instead of the second signal processing unit 44, only the interference component CO is corrected by a configuration similar to the preprocessing circuits 41 to 43, and the interference component _CH4 is not corrected. On the other hand, if each preprocessing circuit 41 is composed of one replaceable substrate, one of the existing substrates is replaced with the substrate of the second signal processing unit 44, and the arithmetic processing of the CPU 31 is performed by software. Correction for the interfering component, _CH4 , can be introduced just by changing it.

In this case, it is easy to modify the already delivered equipment, and it takes about half a day to modify the equipment.

In the above-described embodiment, the case where there are three types of gas components to be detected and two types of gas components for interference correction has been described, but these numbers may be changed. The number of gas components to be detected may be one or two, or four or more. Moreover, three or more kinds of gas components for interference correction may be used. Even in such a case, one port is used for each gas component to be detected, and the number of ports used can be reduced by sequentially inputting the gas components for interference correction into one port of the CPU in a time-sharing manner. .

In addition, in the present embodiment, an infrared gas analyzer using a reference gas has been described. Similar considerations apply to infrared gas analyzers that use reference cells that are filled and sealed rather than flow through.

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

(Section 1) The gas measurement apparatus of the present disclosure includes a sample cell filled with a sample gas, a light source for irradiating the sample cell with light, and the light intensity of the light emitted from the light source to the sample cell transmitted through the sample cell. A central processing unit for repeatedly analyzing the gas components in the sample gas based on the detection result of the detecting unit, and an interface circuit for transmitting the detection signal detected by the detecting unit to the central processing unit 31. The detection unit includes a first detector that detects a gas component to be analyzed in the sample gas, and a plurality of second detectors that detect a plurality of components for interference correction of the gas component to be analyzed. The interface circuit includes a first signal processing unit that preprocesses the detection signals of the first detector so that they can be input to the central processing unit and transmits them to the central processing unit; and a second signal processing unit for performing preprocessing so that the signals can be input to the central processing unit and sequentially transmitting the signals to the central processing unit in a time division manner. With such a configuration, even if the central processing unit has a small number of input ports, the central processing unit can handle the detection results of a plurality of components for interference correction.

(Section 2) Preferably, the light with which the light source irradiates the sample cell is infrared light.

(Section ₃ ) More preferably, 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 for interference correction include CH4 gas and CO2 gas. The plurality of second detectors includes 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 section includes a first preprocessing circuit that preprocesses the output signal of the SO2 detector and outputs it to a first port, and a second preprocessing circuit that preprocesses the output signal of the NO detector and outputs it to a second port. It has a preprocessing circuit and a third preprocessing circuit that preprocesses the output signal of the CO detector and outputs it to a third port. The second signal processor is configured to alternately output a signal obtained by preprocessing the output signal of the CH4 detector and a signal obtained by preprocessing the output signal of the CO2 detector to the fourth port.

(Section 4) More preferably, each of the first to third preprocessing circuits includes a first analog circuit that adjusts the gain of the output signal of the corresponding detector, and the output of the first analog circuit to the first to third preprocessing circuits. and a first conversion circuit for converting so as to allow input to a corresponding port of the three 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, the output of the second analog circuit and the third analog circuit. A multiplexer alternately selects the output of the analog circuit, and a second conversion circuit converts the output of the multiplexer so that it can be input to the fourth port.

The embodiments disclosed this time should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is indicated by the scope of the claims rather than the description of the above-described embodiments, and is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.

1 gas measuring device, 2, 12 filter, 3, 13 pump, 4, 14 needle valve, 5 switching valve, 5M, 5R three-way valve, 6 motor, 7 light source, 8 sector, 8c sector rotating shaft, 9 sample cell, 9a gas inlet, 9b gas outlet, 20 detector, 21-26 detector, 30 controller, 31 central processing unit, 33 concentration display unit, 34 input unit, 35 output unit, 36 interface circuit, 41-43 pretreatment Circuit 44 Second signal processing unit 51, 53, 55, 57, 58 Analog circuit 52, 54, 56, 60 Conversion circuit 59 Multiplexer ML Sample gas line P1 to P4 ports RL Reference gas line.

Claims (4)

a sample cell filled with a sample gas;
a light source that irradiates the sample cell with light;
a detection unit that detects the intensity of the light emitted from the light source to the sample cell and transmitted through the sample cell;
a central processing unit that repeatedly analyzes the gas components in the sample gas based on the detection result of the detection unit;
An interface circuit that transmits a detection signal detected by the detection unit to the central processing unit,
The detection unit is
a first detector that detects a gas component to be analyzed in the sample gas;
a plurality of second detectors for detecting a plurality of components for interference correction of the gas component to be analyzed;
The interface circuit is
a first signal processing unit that preprocesses the detection signal of the first detector so that it can be input to the central processing unit and transmits the signal to the central processing unit;
a second signal processing unit that pre-processes the detection signals of the plurality of second detectors so that they can be input to the central processing unit and sequentially transmits them to the central processing unit in a time division manner. 2. The gas measuring device according to claim 1, wherein the light with which said light source irradiates said sample cell is infrared light. _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 plurality of components for interference correction includes _CH4 gas and _CO2 gas;
the plurality of _second detectors includes 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 is
a first preprocessing circuit that preprocesses an output signal of the SO ₂ gas detector and outputs the signal to the first port;
a second preprocessing circuit that preprocesses the output signal of the NO gas detector and outputs the signal to the second port;
a third preprocessing circuit that preprocesses the output signal of the CO gas detector and outputs the output signal to the third port;
The second signal processing unit alternately outputs 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. 3. The gas measurement device of claim 2, configured to: Each of the first to third preprocessing circuits
a first analog circuit that adjusts the gain of the corresponding detector output signal;
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 to third ports;
The second signal processing unit is
a _second analog circuit for adjusting the gain of the output signal of the CH4 gas detector;
a third analog circuit for adjusting the gain of the output signal of the _CO2 gas detector;
a multiplexer that alternately selects the output of the second analog circuit and the output of the third analog circuit;
4. The gas measurement device according to claim 3, further comprising a second conversion circuit for converting the output of said multiplexer so that it can be input to said fourth port.

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