JP2013096810A - Device and method for optical gas measurement - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly accurate device and method for analyzing gas.SOLUTION: Provided is an optical gas measurement device for analyzing a plurality of components contained in target gas. The optical gas measurement device detects a differential signal by using different laser light for each component of a measurement target and by splitting the laser light into measurement laser light that passes a measurement cell and reference laser light that does not pass the measurement cell. Signal processing means, which generates the differential signal corresponding to the difference between intensity of the measurement laser light and intensity of the reference laser light received by light receiving means, includes a plurality of differential detectors having different detection sensitivities for detecting the difference between intensity of the measurement laser light and intensity of the reference laser light. Highly accurate measurement is made by switching the differential detector to be used to input the differential signal to an analyzer depending on a wavelength of laser light entering the measurement cell.

Description

  The present invention relates to an optical gas measurement device and an optical gas measurement method for analyzing a plurality of components contained in a gas by irradiating a measurement target gas with laser light.

  As a method of analyzing a plurality of components contained in a gas (gas) flowing in the pipeline, there is a method of analyzing the gas flowing in the pipeline by irradiating it with laser light. For example, Patent Document 1 filed by the applicant of the present application discloses an exhaust gas that irradiates laser light into an exhaust path through which exhaust gas discharged from an internal combustion engine circulates and analyzes the exhaust gas based on laser light that has passed through the exhaust gas. An analyzer is described. The exhaust gas analyzer includes a laser beam generator that generates a plurality of laser beams having absorption wavelengths that match the components of the exhaust gas, and a plurality of laser beams generated by the laser beam generator are used as a signal laser beam and a reference laser beam, respectively. A demultiplexing unit that demultiplexes the laser beam, a signal multiplexing unit that multiplexes each signal laser beam demultiplexed by the demultiplexing unit into a single signal laser beam, and demultiplexing by the demultiplexing unit A reference multiplexing unit that multiplexes each reference laser beam into a single reference laser beam, an irradiation unit that irradiates a single signal laser beam to the exhaust path, and a single unit that has passed through the exhaust path A sensor unit including a light receiving unit that receives the signal laser beam, and a personal computer that calculates each component from a difference between the light intensity of the laser beam detected by the sensor unit and the light intensity of the single reference laser beam. .

Japanese Patent No. 4490333

  The exhaust gas analyzer described in Patent Document 1 uses laser light corresponding to each component of the gas to be measured flowing through the exhaust gas, that is, the pipe, and passes the laser light to the exhaust path, that is, the pipe through which the gas to be measured flows. The measurement target component is analyzed by detecting the difference between the measurement light to be incident and the reference light that does not pass through the pipeline, and the difference between the measurement light that has passed through the pipeline and the reference light that does not pass through the pipeline. Can do. In addition, the exhaust gas analyzer described in Patent Document 1 can simplify the device configuration by combining a plurality of laser beams corresponding to each component of the gas to be measured into one measurement path, The apparatus can be made inexpensive. Here, although the exhaust gas analyzer described in Patent Document 1 can measure each component of the gas to be measured, a component with low measurement accuracy may occur.

For example, the exhaust gas analyzer described in Patent Document 1 is a component (chemical species) to be measured that has a particularly strong light absorption amount compared to other components (for example, H ₂ O in exhaust gas). If there is, the difference detector is saturated with the measurement value of the light absorption amount, the measurement value of the light absorption amount of the other component (chemical species) can be suppressed low, and the measurement sensitivity of the component becomes low. That is, if the exhaust gas analyzer uses a difference detector for detecting a component having a strong light absorption amount, the detection sensitivity of the weak light absorption amount is lowered. Here, the amount of light absorption is determined by density x inherent absorption intensity of the component. For this reason, even if the concentration in the gas to be measured is the same, if the intrinsic absorption intensity of the component is greater than the other components, the amount of light absorption is stronger than the other components, and measurement is performed even if the intrinsic absorption intensity of the component is the same When the concentration contained in the target gas is higher than that of other components, the amount of light absorption becomes stronger than that of other components.

  The present invention has been made in view of the above, and provides an optical gas analyzer and a gas analysis method capable of analyzing a plurality of types of substances contained in a gas to be measured with higher accuracy. Objective.

  In order to solve the above-described problems and achieve the object, the present invention is an optical gas measurement device that analyzes a plurality of components contained in a measurement target gas, the measurement cell through which the measurement target gas flows, and the gas A light emitting unit that can switch and output a plurality of laser beams including wavelengths corresponding to a plurality of components to be measured, and branches the output laser beams into a measurement laser beam and a reference laser beam, and the measurement laser beam into the measurement cell A light emitting means having a measuring light optical system to be incident on the light source and a reference light optical system for guiding the reference laser light; and controlling the operation of the light emitting means to select a laser light having a wavelength corresponding to a component to be measured. Then, after the selected laser beam is incident on the measurement cell and measurement of the component to be measured is completed, the laser beam having a wavelength corresponding to the component to be measured to be measured next is selected and selected. A light emission control means for making the laser light incident on the measurement cell; a first light receiving device for receiving the measurement laser light that has passed through the measurement cell; and the reference laser light guided by the reference light optical system. A light receiving means including a second light receiving device, a signal processing means for generating a difference signal between the intensity of the measurement laser light received by the light receiving means and the intensity of the reference laser light, and a signal generated by the signal processing means An analysis device that analyzes a component to be measured based on the signal processing means, wherein the signal processing means includes a difference detector having different detection sensitivities for detecting a difference between the intensity of the measurement laser beam and the intensity of the reference laser beam. A plurality of the detectors are provided, and the difference detector that inputs a difference signal to the analyzer is switched according to the wavelength of the laser light incident on the measurement cell.

  The light emitting unit emits a laser beam including a wavelength corresponding to a component to be measured of the gas, and branches the laser beam emitted from the light emitting unit into a measurement laser beam and a reference laser beam. A plurality of light emission units each including a light emitting unit optical system for guiding a demultiplexer and the measurement laser beam demultiplexed by the demultiplexer and the reference laser beam, each of which emits a laser beam having a wavelength corresponding to a different component; A first unit that multiplexes the measurement laser beams of the plurality of light emitting unit units, and a second multiplexer that multiplexes the reference laser beams of the plurality of light emitting unit units, The measurement light optical system causes the measurement laser light combined by the first multiplexer to be incident on the measurement cell, and the reference light optical system is the reference combined by the second multiplexer Guide the laser light and control the emission The stage switches the light emitting unit for outputting the laser light every time, and causes the laser light output from one light emitting unit to enter the measurement cell, and the signal processing means enters the measurement cell. It is preferable to switch the difference detector that detects the difference signal output to the analysis device in accordance with the light emitting unit that outputs laser light.

  The signal processing means inputs a first signal switching device for switching the difference detector that inputs a light reception signal output from the first light receiving device, and a light reception signal output from the second light receiving device. A second signal switching device that switches between the difference detectors, and the first signal switching device and the second signal switching device switch the difference detector that receives a light reception signal, so that a difference signal is sent to the analysis device. It is preferable to switch the difference detector for inputting.

  Moreover, it is preferable that the signal processing means includes a signal switching device that switches a difference signal input to the analysis device among the difference signals output from the plurality of difference detectors.

  Further, the analysis device determines the difference detector that outputs a difference signal to be used when analyzing each gas type based on the magnitude of the difference signal of each gas type, and operates the signal processing unit. Is preferably controlled.

  Moreover, it is preferable that the said signal processing means outputs the difference signal output from a difference detector with a lower detection sensitivity to the said analysis apparatus in the measurement at the time of a measurement start.

  The signal processing means preferably has a difference between the sensitivity of the difference detector and the sensitivity of the difference detector adjacent to the difference detector in the range of 5 to 20 times.

  The signal processing means preferably includes two difference detectors.

  Further, it is preferable that the light emission control unit sweeps a laser beam having a wavelength corresponding to a measurement target component to be measured in a range including a wavelength corresponding to the measurement target component and outputs the laser light from the light emitting unit. .

  In order to solve the above-described problems and achieve the object, the present invention switches and outputs a measurement cell through which a measurement target gas flows and a plurality of laser beams including wavelengths corresponding to a plurality of components of the measurement target of the gas. A light emitting unit that branches the output laser light into measurement laser light and reference laser light, a measurement light optical system that causes the measurement laser light to enter the measurement cell, and a reference light optical system that guides the reference laser light Controlling the operation of the light emitting means and the light emitting means, selecting a laser beam having a wavelength corresponding to the component to be measured to be measured, causing the selected laser beam to enter the measurement cell, and After the measurement is completed, a light emission control means for selecting a laser beam having a wavelength corresponding to a component to be measured next to be measured, and causing the selected laser beam to enter the measurement cell; and the measurement cell Light receiving means comprising a first light receiving device for receiving the measurement laser light that has passed and a second light receiving device for receiving the reference laser light guided by the reference light optical system; and the measurement laser light received by the light receiving means. Signal processing means for generating a difference signal between the intensity of the reference laser light and the intensity of the reference laser light, and an analysis device for analyzing a component to be measured based on the signal generated by the signal processing means, the signal processing An optical unit that analyzes a plurality of components contained in a measurement target gas using an optical gas measurement device including a plurality of difference detectors having different detection sensitivities for detecting a difference between the intensity of the measurement laser beam and the intensity of the reference laser beam. A method of detecting a wavelength of a laser beam incident on the measurement cell, and before inputting a differential signal to the analyzer based on the detected wavelength of the laser beam. And having a step of switching the differential detector, the.

  The optical gas measurement device and the optical gas measurement method according to the present invention have an effect that gas can be analyzed with higher accuracy.

FIG. 1 is a schematic diagram showing a schematic configuration of an example of a gas concentration measuring apparatus which is an embodiment of the optical gas measuring apparatus of the present invention. FIG. 2 is an explanatory diagram illustrating an example of a current signal supplied from the first driver to the first LD. FIG. 3 is an explanatory diagram showing an example of the relationship between the intensity of laser light incident on the measurement cell and time. FIG. 4 is a flowchart showing the measurement operation of the gas concentration measuring apparatus. FIG. 5 is an explanatory diagram illustrating an example of a difference signal detected by the first difference detector. FIG. 6 is an explanatory diagram illustrating an example of a difference signal detected by the second difference detector. FIG. 7 is a schematic diagram showing a schematic configuration of another example of the gas concentration measuring apparatus. FIG. 8 is a flowchart showing the measurement operation of the gas concentration measuring apparatus. FIG. 9 is an explanatory diagram illustrating an example of a difference signal detected by the first difference detector. FIG. 10 is an explanatory diagram illustrating an example of a difference signal detected by the second difference detector. FIG. 11 is a schematic diagram showing a schematic configuration of another example of the gas concentration measuring apparatus. FIG. 12 is a flowchart showing the measurement operation of the gas concentration measuring apparatus. FIG. 13 is a flowchart showing an example of the determination process of the difference detector of the gas concentration measuring apparatus. FIG. 14 is a schematic diagram illustrating a schematic configuration of a test apparatus including a gas concentration measuring device. FIG. 15 is a graph illustrating an example of a measurement result of the test apparatus illustrated in FIG. FIG. 16 is a graph showing another example of the measurement result of the test apparatus shown in FIG.

  Hereinafter, an optical gas measuring device and a gas measuring method according to an embodiment of the present invention will be described in detail with reference to the drawings. In the following embodiment, a case will be described in which the present invention is used as a gas concentration measurement device that measures the concentration of a plurality of target components contained in exhaust gas (gas to be measured) flowing through a pipeline. However, the present invention is not limited to the above.

Moreover, when using as a gas concentration measuring apparatus, the density | concentration of a some component (gas seed | species, chemical species) can be measured about the various gas which flows through a pipe line. For example, a gas concentration measuring device may be attached to a diesel engine and the concentrations of a plurality of components contained in exhaust gas discharged from the diesel engine may be measured. Note that an engine that exhausts exhaust gas, that is, a device that exhausts (supplies) a gas to be measured is not limited thereto, and various internal combustion engines such as a gasoline engine and a gas turbine can be used. Examples of the device having an internal combustion engine include various devices such as vehicles, ships, and generators. Furthermore, it is also possible to measure the concentrations of the components to be measured contained in the exhaust gas discharged from the garbage incinerator. Examples of components (substances, gas species, chemical species) to be measured include carbon monoxide (CO), carbon dioxide (CO ₂ ), methane (CH ₄ ), and water (H ₂ O). Further, nitrogen oxides, sulfide oxides, ammonia, and the like can be used as components (substances) to be measured.

(Embodiment 1)
FIG. 1 is a schematic diagram showing a schematic configuration of a gas concentration measuring apparatus which is an embodiment of the optical gas measuring apparatus of the present invention. A gas concentration measuring apparatus 10 shown in FIG. 1 includes a measuring cell (gas measuring cell) 12, a light emitting means 14, a light emission controlling means 15, a light receiving means 16, a signal processing means 18, and an analyzing apparatus 20. .

  The measurement cell 12 is a conduit through which exhaust gas flows. In the measurement cell 12, the exhaust gas sampled from the pipe flows, and the exhaust gas whose measurement has been completed is discharged to the outside. The measurement cell 12 basically includes a main pipe connected to an exhaust gas inflow pipe and an exhaust gas outflow pipe, an incident pipe for allowing laser light to enter the main pipe, and an emission pipe for emitting laser light that has passed through the main pipe. . Note that the entrance tube and the exit tube are provided with windows through which laser light can pass. The main pipe is a cylindrical tubular member, and an inflow pipe is connected near one end, and an outflow pipe is connected near the other end. That is, the main pipe is disposed at a position that becomes a part of the flow path through which the exhaust gas flows. Thereby, exhaust gas flows in order of an inflow pipe, a main pipe, and an outflow pipe. Further, the exhaust gas flowing through the inflow pipe basically flows to the main pipe, and then flows to the outflow pipe.

  The measurement cell 12 receives laser light from the incident tube and is emitted from the emission tube. The passage path of the laser light in the main tube can be set in various ways. For example, the laser beam can pass in a direction orthogonal to the axial direction of the main tube. Further, the laser beam may be allowed to pass through a predetermined angle with respect to the axial direction of the main pipe. Further, a reflecting member may be provided so that the laser beam is reflected in the main tube and reciprocated through the main tube.

  Note that the measurement cell 12 may be provided between the first pipe and the second pipe through which the exhaust gas flows. That is, a measurement cell may be provided in a pipeline through which a measurement target gas flows. In this case, the exhaust gas is supplied from the upstream side of the first pipe, passes through the first pipe, the measurement cell 12, and the second pipe, and is discharged downstream from the second pipe. An exhaust gas generator (supply device) is disposed upstream of the first pipe.

  The light emitting unit 14 includes a first LD 34a, a second LD 34b, a third LD 34c, a fourth LD 34d, duplexers 38a, 38b, 38c, 38d, multiplexers 42a, 42b, and a condensing optical system 43. . The light emitting means 14 is connected to each other by optical fibers 36a, 36b, 36c, 36d, 40a, 40b, 40c, 40d, 41a, 41b, 41c, 41d, 44 for guiding laser light.

  The first LD 34a, the second LD 34b, the third LD 34c, and the fourth LD 34d are light-emitting elements that output laser beams in wavelength ranges that measure different components to be measured. For example, the first LD 34a is a light emitting element that outputs laser light L1 in a wavelength range that can measure water, and the second LD 34b is light emission that outputs laser light L2 in a wavelength range that can measure carbon monoxide. The third LD 34c is a light emitting element that outputs a laser beam L3 in a wavelength range capable of measuring carbon dioxide, and the fourth LD 34d outputs a laser beam L4 in a wavelength range capable of measuring methane. It is a light emitting element. In addition, the laser beam in the wavelength region in which the component to be measured can be measured is a laser beam including a wavelength corresponding to the component to be measured. For example, a laser beam in a wavelength region in which a component to be measured can be measured is a laser beam including a wavelength that is absorbed or scattered by the measurement target substance.

  Here, in the light emitting means 14, the first LD 34a, the optical fibers 36a, 40a, 41a, and the demultiplexer 38a constitute one light emitting unit, and the second LD 34b, the optical fibers 36b, 40b, 41b, and the demultiplexer 38b emit one light. The third LD 34c, the optical fibers 36c, 40c, 41c, and the demultiplexer 38c become one light emitting unit, and the fourth LD 34d, the optical fibers 36d, 40d, 41d, and the demultiplexer 38d become one light emitting unit. . The light emitting unit has basically the same configuration except that the wavelengths of laser beams output from the first LD 34a, the second LD 34b, the third LD 34c, and the fourth LD 34d are different. Hereinafter, the light emitting unit having the first LD 34a, the optical fibers 36a, 40a, 41a, and the duplexer 38a will be described as a representative.

  First, the first LD 34a is a light emitting element that outputs the laser light L1 as described above. Next, the optical fibers 36a, 40a, and 41a are members (light guide members) for guiding laser light. The optical fiber 36a connects the first LD 34a and the duplexer 38a, and makes the laser beam output from the first LD 34a enter the duplexer 38a. The optical fiber 40a connects the duplexer 38a and the multiplexer 42a, and causes the laser beam output from the duplexer 38a to enter the multiplexer 42a. The optical fiber 41a connects the duplexer 38a and the multiplexer 42b, and makes the laser beam output from the duplexer 38a enter the multiplexer 42b.

  The duplexer 38a splits the laser light emitted from the first LD 34a into two laser lights. Specifically, the duplexer 38a splits the laser light L1 emitted from the first LD 34a into two laser lights L1.

  The light emitting unit having the first LD 34a, the optical fibers 36a, 40a, 41a, and the branching filter 38a is configured as described above, and the laser beam L1 emitted from the first LD 34a passes through the optical fiber 36a and is branched. It is incident on 38a. The laser beam L1 emitted from the first LD 34a is divided into two by the duplexer 38a, one laser beam L1 is incident on the multiplexer 42a, and the other laser beam L1 is incident on the multiplexer 42b. .

  Similarly, in the light emitting unit having the second LD 34b, the optical fibers 36b, 40b, 41b, and the demultiplexer 38b, the laser light L2 emitted from the second LD 34b passes through the optical fiber 36b and enters the demultiplexer 38b. . The laser beam L2 emitted from the second LD 34b is divided into two by the demultiplexer 36b, one laser beam L2 is incident on the multiplexer 42a, and the other laser beam L2 is incident on the multiplexer 42b. .

  In the light emitting unit having the third LD 34c, the optical fibers 36c, 40c, 41c, and the demultiplexer 38c, the laser light L3 emitted from the third LD 34c passes through the optical fiber 36c and is incident on the demultiplexer 38c. The laser beam L3 emitted from the third LD 34c is divided into two by the demultiplexer 38c, one laser beam L3 is incident on the multiplexer 42a, and the other laser beam L3 is incident on the multiplexer 42b. .

  In the light emitting unit having the fourth LD 34d, the optical fibers 36d, 40d, 41d, and the demultiplexer 38d, the laser light L4 emitted from the fourth LD 34d passes through the optical fiber 36d and is incident on the demultiplexer 38d. The laser beam L4 emitted from the fourth LD 34d is split into two by the duplexer 38d, one laser beam L4 is incident on the multiplexer 42a, and the other laser beam L4 is incident on the multiplexer 42b. .

  The light emitting unit may be provided with an adjustment mechanism (VOA) that can change the attenuation within a certain range on the downstream side of the duplexers 38a, 38b, 38c, and 38d.

  The multiplexers 42a and 42b multiplex a plurality of laser beams. The multiplexer 42a is coupled to the optical fibers 40a, 40b, 40c, and 40d, and multiplexes one of the laser beams L1, L2, L3, and L4 that have passed through the optical fibers 40a, 40b, 40c, and 40d. . The multiplexer 42b is coupled to the optical fibers 41a, 41b, 41c, and 41d, and multiplexes the other laser beams L1, L2, L3, and L4 that have passed through the optical fibers 41a, 41b, 41c, and 41d. . The laser beam combined by the multiplexer 42a becomes a measurement laser beam. The laser beam combined by the multiplexer 42b becomes a reference laser beam.

  The condensing optical system 43 is an optical system that guides the measurement laser light output from the multiplexer 42 a to the incident portion of the measurement cell 12. The condensing optical system 43 has a lens or the like, condenses the measurement laser light output from the multiplexer 42 a, and makes it incident on the measurement cell 12. The optical fiber 44 is an optical member that guides the reference laser beam output from the multiplexer 42b.

  The light emission control unit 15 includes a first driver 47a, a second driver 47b, a third driver 47c, a fourth driver 47d, and an LD controller 48. The first driver 47a, the second driver 47b, the third driver 47c, and the fourth driver 47d are drive units that output current signals. The first driver 47a outputs a current signal to the first LD 34a. The second driver 47b outputs a current signal to the second LD 34b. The third driver 47c outputs a current signal to the third LD 34c. The fourth driver 47d outputs a current signal to the fourth LD 34d.

  The LD controller 48 sends control signals to the first driver 47a, the second driver 47b, the third driver 47c, and the fourth driver 47d, and the first driver 47a, the second driver 47b, The operation of the third driver 47c and the fourth driver 47d is controlled.

  Here, FIG. 2 is an explanatory diagram illustrating an example of a current signal supplied from the first driver to the first LD. The LD controller 48 sends a control signal to the first driver 47a, in which the current value of the current signal gradually increases and the current value changes from the maximum value to 0 after a certain time has elapsed. When the first driver 47a receives the control signal from the LD controller 48, as shown in FIG. 2, the first driver 47a sends a current signal whose current value gradually increases linearly from the time ts to the time te to the first LD 34a.

  Further, when the LD controller 48 sends a control signal in which the current value of the current signal gradually increases to the first driver 47a and the current value changes from the maximum value to 0 after a lapse of a certain time, the same applies to the second driver 47b. Send control signal. When the LD controller 48 sends the second driver 47b a control signal in which the current value of the current signal gradually increases and the current value changes from the maximum value to 0 after a certain time has elapsed, the same control is performed to the third driver 47c. Send a signal. If the current value of the current signal gradually increases to the third driver 47c and the LD controller 48 sends a control signal for changing the current value from the maximum value to 0 after a certain time has elapsed, the LD controller 48 performs similar control to the fourth driver 47d. Send a signal. When the LD controller 48 sends the fourth driver 47d a control signal in which the current value of the current signal gradually increases and the current value changes from the maximum value to 0 after a predetermined time has elapsed, the same control is performed to the first driver 47a. Send a signal. Also, the LD controller 48 processes the LD control signal (a signal indicating the driving state of each light emitting unit) to be sent to the first driver 47a, the second driver 47b, the third driver 47c, and the fourth driver 47d. Also sent to the means 18 and the analyzer 20.

  As described above, the light emission control unit 15 uses the LD controller 48 to set the current value of the current signal one by one with respect to the first driver 47a, the second driver 47b, the third driver 47c, and the fourth driver 47d. By gradually sending a control signal that changes the current value from the maximum value to 0 after a lapse of a certain time, laser light is sequentially emitted from the first LD 34a, the second LD 34b, the third LD 34c, and the fourth LD 34d in order. Can be output. Further, as shown in FIG. 2, the control signal is a control signal in which the current value changes from the maximum value to 0 after a lapse of a certain time, whereby each of the first LD 34a, the second LD 34b, the third LD 34c, and the fourth LD 34d. The wavelength of the laser beam output from the laser beam varies with time. That is, the laser light output from each of the first LD 34a, the second LD 34b, the third LD 34c, and the fourth LD 34d is a laser light having a swept wavelength.

  Here, FIG. 3 is an explanatory diagram showing an example of the relationship between the intensity of laser light incident on the measurement cell and time. The light emission means 14 and the light emission control means 15 output the measurement laser light output from the combining section 42a and the output from the combining section 42b by outputting the laser light sequentially swept from the plurality of light emitting section units in this way. As shown in FIG. 3, the laser beam output gradually increases, and the waveform in which the output changes from the maximum value to 0 after a lapse of a certain time is repeated a plurality of times. Here, the output waveform 72 from the time t1s to the time t1e is an output waveform of the laser light L1, and the output waveform 74 from the time t2s to the time t2e is an output waveform of the laser light L2 and from the time t3s to the time. An output waveform 76 during t3e is an output waveform of the laser beam L3, and an output waveform 78 between time t4s and time t4e is an output waveform of the laser beam L4. In FIG. 3, the waveforms 72, 74, 76, and 78 are the same, but the wavelength of the output laser light and the swept wavelength range are different from those of the waveforms 72, 74, 76, and 78. Become. That is, the light emitting unit 14 and the light emission control unit 15 sequentially output laser light from each of the light emitting unit, and cause the laser light output from one light emitting unit to enter the measurement cell 12 in order.

  Returning to FIG. 1, the description of the gas concentration measuring apparatus 10 will be continued. The light receiving means 16 has two light receiving devices 50a and 50b. The light receiving device 50 a receives the measurement laser light that has been combined by the combining unit 42 a, passed through the condensing optical system 43, output from the light emitting means 14, and then passed through the measurement cell 12. In addition, the light receiving device 50 b receives the reference laser light that has been output from the multiplexing unit 42 b of the light emitting unit 14, passes through the optical fiber 44, and does not pass through the measurement cell 12. The light receiving devices 50a and 50b are, for example, photodetectors such as photodiodes (PD), and detect the intensity of received laser light. The light receiving means 16 sends the intensity of the received laser beam as a light reception signal to the signal processing means 18.

  The signal processing means 18 is a means for processing the light reception signals output from the light receiving device 50a and the light receiving device 50b of the light receiving means 16, and includes a first signal switching device 60a, a second signal switching device 60b, and a first difference detector 62a. And a second difference detector 62b.

  The first signal switching device 60a is connected to the light receiving device 50a, the first difference detector 62a, and the second difference detector 62b, and receives the light receiving signal (light receiving signal of the measurement laser light) output from the light receiving device 50a. Whether to input to the first difference detector 62a or to input to the second difference detector 62b is switched. Specifically, the first signal switching device 60a sets the output destination of the received light signal between the first difference detector 62a and the second difference detector 62b based on the control signal output from the LD controller 48. Switch.

  The second signal switching device 60b is connected to the light receiving device 50b, the first difference detector 62a, and the second difference detector 62b, and receives the light reception signal (the light reception signal of the reference laser light) output from the light reception device 50b. Whether to input to the first difference detector 62a or to input to the second difference detector 62b is switched. Specifically, the second signal switching device 60b determines the output destination of the received light signal between the first difference detector 62a and the second difference detector 62b based on the control signal output from the LD controller 48. Switch.

  The first difference detector 62a detects the light reception signal sent from the first signal switching device 60a and the light reception signal sent from the second signal switching device 60b, and sends the detected difference to the analysis device 20 as a difference signal. . Similar to the first difference detector 62a, the second difference detector 62b detects the received light signal sent from the first signal switching device 60a and the received light signal sent from the second signal switching device 60b, and detects the detected difference. Is sent to the analysis device 20 as a differential signal. Here, the first difference detector 62a and the second difference detector 62b have basically the same configuration except that the gain of the difference signal, that is, the difference in the intensity of the detectable difference signal and the resolution are different. . In the present embodiment, the first difference detector 62a can detect a difference signal having a greater difference in the intensity of the difference signal that can be detected than the second difference detector 62b, that is, a larger difference signal. The first difference detector 62a has a lower resolution than the second difference detector 62b because the difference in the intensity of the difference signal that can be detected is larger than that of the second difference detector 62b. The operation of the signal processing means 18 will be described later.

  The analysis device 20 performs analysis based on the signals sent from the first difference detector 62a and the second difference detector 62b, conditions for driving the light emitting means 14, and the like, and the concentrations of the components to be measured. Is calculated. That is, the analysis device 20 analyzes the difference signal based on the difference detector that has output the difference signal, the output intensity of the laser light, the relationship between the magnitude and concentration of the difference signal, and the like, and the component to be measured included in the exhaust gas. The concentration of is calculated. As described above, the analysis device 20 analyzes the difference signal to calculate the absorption amount of the laser light by the component of the measurement object of the exhaust gas in the measurement cell 12, and the measurement included in the exhaust gas based on the absorption amount. Calculate the concentration of the component of interest.

  The gas concentration measuring apparatus 10 is configured as described above, and the light emission control means 15 controls the light emission means 14 to sequentially output laser light from each LD. The light emitting means 14 separates the output laser light into measurement laser light and reference laser light. Thereafter, the measurement laser light passes through a predetermined path of the measurement cell 12 and then reaches the light receiving means 16. Note that if the measurement target component is contained in the exhaust gas in the measurement cell 12, a part of the measurement laser light passing through the measurement cell 12 is absorbed and scattered by the measurement target component. For this reason, the output of the laser beam that reaches the light receiving means 16 varies depending on the concentration of the component to be measured in the exhaust gas. Further, the reference laser beam reaches the light receiving means 16 without passing through the measurement cell 12. The light receiving means 16 converts the received measurement laser light and reference laser light into light reception signals and outputs them to the signal processing means 18. The signal processing means 18 processes the light receiving signal sent from the light receiving means 16 and outputs it as a differential signal to the analysis device 20. Based on the difference signal and various conditions, the analysis device 20 calculates the concentration of the measurement object of the exhaust gas flowing in the measurement cell 12 from the magnitude of the difference signal (the reduction rate of the measurement laser light). Further, the gas concentration measuring apparatus 10 can sequentially calculate and / or measure the concentrations of the components to be measured by switching the laser light incident on the measurement cell 12.

  Next, the operation of the gas concentration measuring device 10 will be described in more detail. Here, FIG. 4 is a flowchart showing the measuring operation of the gas concentration measuring apparatus. FIG. 5 is an explanatory diagram illustrating an example of a difference signal detected by the first difference detector. FIG. 6 is an explanatory diagram illustrating an example of a difference signal detected by the second difference detector. The process shown in FIG. 4 is a process executed by the signal processing means 18. Note that the processing shown in FIG. 4 is executed by the first signal switching device 60a and the second signal switching device 60b of the signal processing means 18 based on the LD control signal. First, the signal processing means 18 receives an LD control signal as step S12. When the signal control means 18 receives the LD control signal in step S12, it determines in step S14 whether the first difference detector processes it. That is, based on the LD control signal, the LD that outputs the laser beam, that is, the component to be measured is specified, and it is determined whether the difference detector used when measuring the component is the first difference detector. Note that the relationship between the LD control signal and the difference detector to be used may be set in advance.

  If it is determined in step S14 that the first difference detector processes (Yes), the signal processing means 18 transmits the received light signal to the first difference detector as step S16, and proceeds to step S20. If it is determined in step S14 that the first difference detector does not perform processing (No), the signal processing seed means 18 transmits the received light signal to the second difference detector as step S18, and proceeds to step S20. The signal processing means 18 determines whether the processing is finished as step S20. If the signal processing means 18 determines that the process is not finished (No) in step S20, the signal processing means 18 proceeds to step S12 and repeats this process. If the signal processing means 18 determines that the process is finished (Yes) in step S20, the process is finished.

  As shown in FIG. 4, the gas concentration measurement apparatus 10 switches between processing the light reception signal by the first difference detector 62a or the second difference detector 62b based on the LD control signal, thereby changing the laser. The difference signal can be detected by an appropriate difference detector corresponding to the light emitting unit that outputs light and the component to be measured. Specifically, as shown in FIGS. 5 and 6, the gas concentration measuring apparatus 10 receives a light reception signal detected from time t1s to time t1e, that is, while laser light is being output from the first LD 34a. By making it input into the 1st difference detector 62a, the difference signal 82 is detectable with the 1st difference detector 62a. The gas concentration measuring apparatus 10 inputs the light reception signal detected during the period from the time t2s to the time t4e, that is, while the laser light is being output from the second LD 34b, the third LD 34c, and the fourth LD 34d, to the second difference detector 62b. Thus, the difference signals 84, 86, and 88 can be detected by the second difference detector 62b.

  As described above, the gas concentration measuring apparatus 10 includes a plurality of differential detectors having different gains, and each component (gas species, chemical species) to be measured, that is, the wavelength (wavelength band) of laser light incident on the measurement cell. Each gas type can be detected with higher accuracy by switching the difference detector to be used every time. That is, even when the gas concentration measuring apparatus 10 measures a plurality of types of components having different difference signal intensities, the difference signal of some components is small and the concentration cannot be measured with an appropriate resolution, and the difference signal is large. Therefore, it is possible to suppress the occurrence of a situation such as the value overflowing and the accurate value not being known. In addition, since the gas concentration measuring device 10 does not need to change the gain and sensitivity of the difference detector, an inexpensive difference detector can be used.

  The gas concentration measuring device 10 includes a first signal switching device 60a and a second signal switching device 60b, and switches between inputting the light reception signal to the first difference detector 62a and the second difference detector 62b. It can be suppressed that a difference signal larger than the output that can be processed is input to the first difference detector 62a and the second difference detector 62b, basically the second difference detector 62b. Thereby, the lifetime of an apparatus can be lengthened.

In the present embodiment, two difference detectors are used, but the number of difference detectors is not limited to this. The gas concentration measuring apparatus 10 can be simplified in configuration by using two difference detectors as in the present embodiment. Here, in the gas concentration measuring apparatus 10, the difference between the sensitivity (gain) of the difference detector and the sensitivity of the difference detector whose sensitivity is adjacent to the difference detector is not less than 5 times and not more than 20 times. It is preferable that the difference in sensitivity is 10 times. As a result, a difference signal with a wider range of output can be suitably detected with a smaller number of difference detectors, and the concentration can be detected with higher accuracy. For example, when measuring a plurality of components contained in exhaust gas, the amount of light absorbed by H ₂ O (about 12%) at a temperature of 600 ° C. is compared between the wavelength used for H ₂ O measurement and the CO measurement wavelength. If 1 is 1, the light absorption amount due to the maximum CO generation amount (about 6%) at the normal gasoline engine outlet is 0.18. For this reason, by making the gain (sensitivity) of the difference detector for other component measurement (for example, CO) about 5 times or more the gain of the difference detector used for H ₂ O measurement, H ₂ O and CO are Both the other components included can be detected with high accuracy. In addition, the CO concentration during steady operation is low (approximately 0.2% or less). For this reason, assuming that the light absorption amount by H ₂ O (about 12%) is 1, the light absorption amount of CO during steady operation is 0.006. In this case, from the viewpoint of the gain of the difference detector of the gas concentration measurement device, the measurement value at this time may be about 1/10 of the CO measurement range. For this reason, the accuracy can be maintained high by setting the difference in gain between the two difference detectors to 20 times or less.

  In addition, the gas concentration measuring apparatus 10 can detect the peak value of the detection result of the component to be measured with high accuracy by sweeping the wavelength of the laser light. Further, the gas concentration measuring apparatus 10 can measure one gas type in a short time with respect to the movement of the measurement cell 12 of the measurement target gas. Thereby, even if the gas concentration measuring apparatus 10 measures a some component sequentially, it can perform the measurement with respect to the same object fundamentally.

(Embodiment 2)
In the above embodiment, the difference detector that detects the difference signal to be analyzed is switched by switching the difference detector that inputs the light reception signal, but the present invention is not limited to this. Hereinafter, another embodiment will be described with reference to FIGS. Here, FIG. 7 is a schematic diagram showing a schematic configuration of another example of the gas concentration measuring apparatus. The gas concentration measuring apparatus 100 shown in FIG. 7 is the same as the gas concentration measuring apparatus 10 except for the signal processing means 118. Therefore, in the configuration of the gas concentration measuring apparatus 100, the same components as those of the gas concentration measuring apparatus 10 are denoted by the same reference numerals, and the description thereof is omitted. Hereinafter, points unique to the gas concentration measuring apparatus 100 will be described. To do.

  A gas concentration measuring apparatus 100 shown in FIG. 7 includes a measurement cell 12, a light emitting means 14, a light emission controlling means 15, a light receiving means 16, a signal processing means 118, and an analyzing apparatus 20. The measurement cell 12, the light emission means 14, the light emission control means 15, the light reception means 16, and the analysis device 20 have the same configuration as each part of the gas concentration measurement device 10 shown in FIG. Omitted.

  The signal processing unit 118 is a unit that processes a light reception signal output from the light receiving device 50a and the light receiving device 50b of the light receiving unit 16, and includes a first difference detector 62a, a second difference detector 62b, and a signal switching device 164. .

  The first difference detector 62a detects the light reception signal sent from the light receiving device 50a and the light reception signal sent from the light receiving device 50b, and sends the detected difference to the signal switching device 164 as a difference signal. The second difference detector 62b detects the light reception signal sent from the light receiving device 50a and the light reception signal sent from the light receiving device 50b, and sends the detected difference to the signal switching device 164 as a difference signal. Here, the first difference detector 62a and the second difference detector 62b have the same configuration as the first difference detector 62a and the second difference detector 62b of the gas concentration measuring device 10.

  The signal switching device 164 is connected to the first difference detector 62a, the second difference detector 62b, and the analysis device 20, and inputs the difference signal output from the first difference detector 62a to the analysis device 20. Whether to input the difference signal output from the second difference detector 62b to the analysis device 20 is switched. Specifically, the signal switching device 164 analyzes either the difference signal of the first difference detector 62a or the difference signal of the second difference detector 62b based on the LD control signal output from the LD controller 48. 20 to switch the input.

  Next, the operation of the gas concentration measuring apparatus 100 will be described. Here, FIG. 8 is a flowchart showing the measuring operation of the gas concentration measuring apparatus. FIG. 9 is an explanatory diagram illustrating an example of a difference signal detected by the first difference detector. FIG. 10 is an explanatory diagram illustrating an example of a difference signal detected by the second difference detector. The process shown in FIG. 8 is a process executed by the signal switching device 164 of the signal processing unit 118. First, the signal processing means 118 receives an LD control signal as step S32. When the signal control means 118 receives the LD control signal in step S32, it determines in step S34 whether to process with the first difference detector. That is, based on the LD control signal, the LD that outputs the laser beam, that is, the component to be measured is specified, and it is determined whether the difference detector used when measuring the component is the first difference detector. Note that the relationship between the LD control signal and the difference detector to be used may be set in advance.

  If it is determined in step S34 that the first difference detector processes (Yes), the signal processing means 118 transmits the detection result of the first difference detector to the analyzer as step S36, and proceeds to step S40. That is, the signal switching device 164 of the signal processing means 118 sends the difference signal output from the first difference detector 62a to the analysis device 20. If the signal processing means 118 determines in step S34 that the first difference detector does not perform processing (No), the signal processing means 118 transmits the detection result of the second difference detector to the analysis device as step S38, and proceeds to step S40. That is, the signal switching device 164 of the signal processing unit 118 sends the difference signal output from the second difference detector 62b to the analysis device 20. In step S40, the signal processing unit 118 determines whether the processing is finished. If the signal processing means 118 determines in step S40 that the process is not completed (No), the signal processing means 118 proceeds to step S32 and repeats this process. If the signal processing unit 118 determines that the process is completed (Yes) in step S40, the process ends.

  As shown in FIG. 8, the gas concentration measurement apparatus 100 sends the difference signal processed by the first difference detector 62a to the analysis apparatus 20 based on the LD control signal or the difference processed by the second difference detector 62b. By switching whether the signal is sent to the analysis device 20, the difference signal can be detected by the appropriate difference detector corresponding to the light emitting unit that outputs the laser light and the component to be measured.

  Specifically, as shown in FIGS. 9 and 10, the gas concentration measuring apparatus 100 detects the difference signal by both the first difference detector 62a and the second difference detector 62b from time t1s to time t4e. The The gas concentration measuring device 100 detects a difference signal by both the first difference detector 62a and the second difference detector 62b, and outputs a difference signal to be input to the analysis device 20 based on the LD control signal by the signal switching device 164. Switch. Specifically, the signal switching device 164 performs the difference signal output from the first difference detector 62a as shown in FIG. 9 during the time t1s to the time t1e, that is, while the laser beam is output from the first LD 34a. Is input to the analysis device 20. As a result, the gas concentration measurement apparatus 100 inputs the difference signal surrounded by the dotted line 170 to the analysis apparatus 20. As shown in FIG. 10, the signal switching device 164 outputs the difference output from the second difference detector 62b during the period from time t2s to time t4e, that is, while the laser light is being output from the second LD 34b, the third LD 34c, and the fourth LD 34d. The signal is input to the analysis device 20. As a result, the gas concentration measurement apparatus 100 inputs the difference signal surrounded by the dotted line 172 to the analysis apparatus 20.

  Since the gas concentration measuring device 100 can directly input the light reception signal output from the light receiving means 16 to the difference detector, that is, it can be configured not to pass through the signal branching or signal switching device, it is input to the difference detector. The signal to be processed can be a signal with less noise. Thereby, the noise of a difference signal can be decreased more.

(Embodiment 3)
Hereinafter, another embodiment will be described with reference to FIGS. 11 to 13. Here, FIG. 11 is a schematic diagram showing a schematic configuration of another example of the gas concentration measuring apparatus. The gas concentration measuring device 200 shown in FIG. 11 is basically the same in configuration as the gas concentration measuring device 10 except for the analyzing device 220. Therefore, in the configuration of the gas concentration measuring apparatus 200, the same components as those of the gas concentration measuring apparatus 10 are denoted by the same reference numerals, and the description thereof is omitted. Hereinafter, points unique to the gas concentration measuring apparatus 200 will be described. To do.

  A gas concentration measuring apparatus 200 shown in FIG. 11 includes a measuring cell 12, a light emitting means 14, a light emission controlling means 15, a light receiving means 16, a signal processing means 18, and an analyzing apparatus 220. The measurement cell 12, the light emitting means 14, the light emission control means 15, the light receiving means 16, and the signal processing means 18 have the same configuration as each part of the gas concentration measuring apparatus 10 shown in FIG. Is omitted. Here, the first signal switching device 60 a and the second signal switching device 60 b of the signal processing means 18 of the gas concentration measuring device 200 are not the LD control signals sent from the LD controller 48 but the signals sent from the analysis device 220. Based on the above, the difference detector for inputting the received light signal is switched.

  Similarly to the analysis device 20 described above, the analysis device 220 outputs the difference signal used for the analysis for each component (gas type) in parallel with the measurement of the concentration of the component (gas type) to be measured based on the difference signal or the like. To decide. That is, the analysis device 220 determines whether to perform concentration detection using the difference signal of the first difference detector 62a or to detect concentration using the difference signal of the second difference detector 62b for each component (gas type). Based on the result, the operation of the first signal switching device 60a and the second signal switching device 60b is controlled.

  Next, the operation of the gas concentration measuring apparatus 200 will be described in more detail. Here, FIG. 12 is a flowchart showing the measuring operation of the gas concentration measuring apparatus. FIG. 13 is a flowchart showing an example of the determination process of the difference detector of the gas concentration measuring apparatus. The process shown in FIG. 12 is a process executed by the signal processing means 18 and the analysis device 220.

  In step S60, the analyzer 220 of the gas concentration measuring apparatus 200 determines a difference detector to be used for each target gas type (component to be measured) based on the analysis result. The analysis device 220 determines whether to use the difference signal of the first difference detector 62a for the analysis or the difference signal of the second difference detector 62b for the analysis for each gas type using the past analysis result. The process of step S60 will be described later.

  The analysis device 220 receives the LD control signal as step S62. When receiving the LD control signal in step S62, the analysis device 220 determines in step S64 whether or not to process with the first difference detector. That is, based on the LD control signal, the LD that outputs the laser beam, that is, the component to be measured is specified, and it is determined whether the difference detector used when measuring the component is the first difference detector. Note that the analysis device 220 identifies the relationship between the LD control signal and the difference detector to be used, using the relationship determined in step S60.

  If it is determined in step S64 that the first difference detector processes (Yes), the analysis device 220 transmits a light reception signal to the first difference detector as step S66, and proceeds to step S70. The analysis device 220 transmits a control signal to the first signal switching device 60a and the second signal switching device 60b, and transmits a received light signal from the first signal switching device 60a and the second signal switching device 60b to the first difference detector 62a. Let If it is determined in step S64 that the first difference detector does not perform processing (No), the analysis device 220 transmits a light reception signal to the second difference detector as step S68, and proceeds to step S70. The analysis device 220 transmits a control signal to the first signal switching device 60a and the second signal switching device 60b, and transmits a light reception signal from the first signal switching device 60a and the second signal switching device 60b to the second difference detector 62b. Let

  In step S70, the analysis device 220 determines whether the process is finished. If it is determined in step S70 that the process is not finished (No), the signal processing means 18 determines in step S72 whether the analysis has been executed a predetermined number of times or more. That is, it is determined whether the concentration of the measurement target component has been detected a predetermined number of times or more using the relationship determined in step S60. If the analysis device 220 determines in step S72 that the analysis has been executed a predetermined number of times or more (Yes), the analysis device 220 proceeds to step S60 and determines again the difference detector to be used. If the analysis device 220 determines in step S72 that the analysis has not been executed a predetermined number of times or more (No), the analysis device 220 proceeds to step S62 and repeats this process. If the analysis device 220 determines in step S70 that the processing is complete (Yes), the analysis device 220 ends this processing.

  Next, the process of step S60 will be described with reference to FIG. In step S80, the analysis device 220 detects the magnitude of the difference signal of the gas type. The analysis device 220 only needs to make a determination based on the difference signal used when detecting the concentration of the corresponding gas type. Even if the analysis device 220 detects the magnitude of the difference signal using only the most recent detection result. The magnitude of the difference signal may be detected using the detection results for the most recent multiple times. Here, the analysis device 220 calculates the magnitude of the difference signal based on the relationship between the sensitivity of the first difference detector and the sensitivity of the second difference detector, and the first difference detector and the second difference detector. Whichever detection result is used, detection is performed in a state where the difference signal can be determined based on the same reference.

  If the analyzer 220 detects the magnitude of the difference signal of the target gas type in step S80, it determines whether the magnitude of the difference signal is equal to or greater than a predetermined value in step S82. When determining that the magnitude of the difference signal is equal to or larger than the predetermined value (Yes) in Step S82, the analysis device 220 sets the gas type to be analyzed by the first difference detector as Step S84, and proceeds to Step S88. That is, the analysis device 220 is set to use the difference signal detected by the first difference detector when the gas type is analyzed. If it is determined in step S82 that the magnitude of the difference signal is not equal to or greater than the predetermined value (No), the analyzer 220 sets the gas type to be analyzed by the second difference detector as step S86, and proceeds to step S88. That is, the analysis device 220 is set to use the difference signal detected by the second difference detector when analyzing the gas type.

  After executing the processes of steps S84 and S86, the analysis device 220 determines whether or not all the gas types have been set as step S88. If the analysis device 220 determines in step S88 that the setting of the gas type has not been completed (No), the analysis device 220 proceeds to step S80 and executes the above-described process for the gas type that has not been set. If the analysis device 220 determines in step S88 that the setting of the gas type has been completed (Yes), it ends this processing.

  As described above, the gas concentration measuring apparatus 200 can perform measurement with higher accuracy by switching the difference signal to be used based on the analysis result. For example, even when the concentration of the component to be measured changes during measurement and the magnitude of the difference signal changes, the difference detector to be used can be switched according to the change. Thereby, the density | concentration of the component of a measuring object can be measured with higher precision.

  The gas concentration measuring apparatus 200 preferably uses a difference detector on the side having a lower sensitivity and a side capable of detecting a difference in the output of a larger received light signal at the start of component (gas type) analysis. Thereby, the load concerning a difference detector can be made small. The gas concentration measuring apparatus 200 has the same signal processing means as that of the gas concentration measuring apparatus 10, but the same processing can be executed when the gas concentration measuring apparatus 200 has the same structure as that of the gas concentration measuring apparatus 100. .

  Moreover, although the gas concentration measuring devices 10, 100, and 200 of the above embodiment have been described assuming that there are four light emitting unit units of the light emitting means, the number of light emitting unit units, that is, the number of LDs is not particularly limited. The gas concentration measuring devices 10, 100, and 200 only need to include two or more LDs. The light emitting means includes a plurality of light emitting unit units and outputs a plurality of laser beams respectively corresponding to the components to be measured. However, the present invention is not limited to this. The gas concentration measuring devices 10, 100 and 200 are provided with a laser beam output device capable of switching the wavelength of the laser beam to be output, and the wavelength of the laser beam output from the laser beam output device is sequentially switched every time. May be. In this way, by switching the laser beam with one laser beam output device, laser beams having wavelengths corresponding to different components may be output.

  Moreover, in the said embodiment, although the main pipe of the measurement cell and the guide pipe | tube which flows waste gas were made into the separate member in all, it is good also as integral. For example, the main pipe of the measurement cell may be directly connected to a device that discharges exhaust gas.

  Moreover, the tube shape of the main tube of the measurement cell is not limited as long as the laser beam can pass therethrough, and the tube may have a circular cross section, a polygonal cross section, or an elliptical cross section. Moreover, the cross section of the inner periphery and the outer periphery of the tube may have different shapes.

  Moreover, in the said embodiment, although the density | concentration of the component of a measuring object was measured, it is not limited to this. For example, the amount may be measured instead of the concentration.

[Measurement example]
Next, measurement examples will be described with reference to FIGS. FIG. 14 is a schematic diagram illustrating a schematic configuration of a test apparatus including a gas concentration measuring device. FIG. 15 is a graph illustrating an example of a measurement result of the test apparatus illustrated in FIG. FIG. 16 is a graph showing another example of the measurement result of the test apparatus shown in FIG.

  A test apparatus 300 shown in FIG. 14 has a gas concentration measuring device 302 attached to an internal combustion engine unit 304. Further, the test apparatus 300 outputs the measurement result of the gas concentration measurement apparatus 302 to the PC 306. The internal combustion engine unit 304 has the same configuration as an engine installed in a car. The internal combustion engine unit 304 is an internal combustion engine that discharges exhaust gas, an ECU 312 that controls the engine 310, a gear 314 that is connected to the output shaft of the engine 310, and an output shaft and gear 314 of the engine 310. The connected control dynamo 316, the bench control device 318 that controls the operation of the ECU 312 and the control dynamo 316 to control the operation of the internal combustion engine unit 304, and the exhaust pipe 320 that guides the exhaust gas discharged from the engine 310. And a catalyst 322 for removing various substances contained in the exhaust gas, mainly nitrogen oxides. The control dynamo 316 is a generator or the like, and serves as a resistance to rotation of the engine 310 and can apply a load to the engine 310.

  The gas concentration measuring device 302 is disposed in the exhaust pipe 320 of the internal combustion engine unit 304. The gas concentration measuring device 302 includes a measuring cell 332, a multi-component laser exhaust gas measuring device 334, an optical fiber 336, and a signal line 338. The gas concentration measuring device 302 schematically shows each part, but has basically the same configuration as the gas concentration measuring device 10 described above. In the gas concentration measurement device 302, the measurement cell 332 corresponds to the measurement cell 12 of the gas concentration measurement device 10. The multi-component laser exhaust gas measuring device 334 incorporates the light emitting means 14, the light emission control means 15, the light receiving device 50b of the light receiving means 15, the signal processing means 18, and the analyzing device 20 of the gas concentration measuring device 10. The optical fiber 336 is an optical member that guides the measurement laser light output from the condensing optical system. In the gas concentration measuring device 302, a light receiving device corresponding to the light receiving device 50 a of the light receiving means 16 is attached to the measurement cell 332. The signal line 338 transmits the received light signal received by the light receiving device to the multi-component laser exhaust gas measuring device 334.

In this measurement example, the component of exhaust gas discharged from the engine 310 was measured by the gas concentration measurement device 302 using the test device 300. In this measurement example, carbon monoxide (CO), carbon dioxide (CO ₂ ), methane (CH ₄ ), and water (H ₂ O) were measured when the engine 310 was started.

First, using a gas concentration measuring device 302 for comparison, all of carbon monoxide (CO), carbon dioxide (CO ₂ ), methane (CH ₄ ), and water (H ₂ O) with only one differential detector. The concentration of was measured. The measurement results are shown in FIG. Next, the gas concentration measuring device 302 is used in the above-described method, specifically, using the difference signal detected by the second difference detector, carbon monoxide (CO), carbon dioxide (CO ₂ ), methane (CH ₄ ). ) And the concentration of water (H ₂ O) was measured using the difference signal detected by the first difference detector. The measurement results are shown in FIG.

  As shown in FIG. 15 and FIG. 16, the difference detection used in accordance with the components using two difference detectors than when all the components are measured with one difference detector (see FIG. 15). It can be seen that a clearer analysis result can be detected by switching the instrument (see FIG. 16).

10, 100, 200 Gas concentration measurement device 12 Measurement cell 14 Light emission means 15 Light emission control means 16 Light reception means 18 Signal processing means 20 Analysis device 34a 1st LD
34b 2nd LD
34c 3rd LD
34d 4th LD
36a, 36b, 36c, 36d, 40a, 40b, 40c, 40d, 41a, 41b, 41c, 41d, 44 Optical fiber 38a, 38b, 38c, 38d Demultiplexer 42a, 42b Combiner 43 Condensing optical system 47a First 1 driver 47b second driver 47c third driver 47d fourth driver 48 LD controller 50a, 50b light receiving device 60a first signal switching device 60b second signal switching device 62a, 62b difference detector

Claims (10)

An optical gas measurement device for analyzing a plurality of components contained in a measurement target gas,
A measurement cell through which the gas to be measured flows,
A light emitting unit that can switch and output a plurality of laser beams including wavelengths corresponding to a plurality of components to be measured of the gas, branches the output laser light into a measurement laser beam and a reference laser beam, and the measurement laser beam A light emitting means comprising a measurement light optical system to be incident on a measurement cell and a reference light optical system for guiding the reference laser light;
The operation of the light emitting means is controlled, a laser beam having a wavelength corresponding to the component to be measured to be measured is selected, the selected laser beam is incident on the measurement cell, and the measurement of the component to be measured is completed. Then, light emission control means for selecting a laser beam having a wavelength corresponding to a measurement target component to be measured next, and causing the selected laser beam to enter the measurement cell
A light receiving means including a first light receiving device that receives the measurement laser light that has passed through the measurement cell, and a second light receiving device that receives the reference laser light guided by the reference light optical system;
Signal processing means for generating a differential signal between the intensity of the measurement laser light received by the light receiving means and the intensity of the reference laser light;
An analyzer for analyzing a component to be measured based on the signal generated by the signal processing means,
The signal processing means includes a plurality of difference detectors having different detection sensitivities for detecting the difference between the intensity of the measurement laser light and the intensity of the reference laser light, and depending on the wavelength of the laser light incident on the measurement cell, An optical gas measuring device, wherein the differential detector for inputting a differential signal to the analyzing device is switched. The light emitting unit emits a laser beam including a wavelength corresponding to a component to be measured of the gas, and a demultiplexing unit that branches the laser beam emitted from the light emitting unit into a measurement laser beam and a reference laser beam. And a plurality of light emitting unit units each including a light emitting unit optical system for guiding the measurement laser beam demultiplexed by the demultiplexer and the reference laser beam, and emitting laser beams each having a wavelength corresponding to a different component And a first multiplexer that multiplexes the measurement laser beams of the plurality of light emitting unit units, and a second multiplexer that multiplexes the reference laser beams of the plurality of light emitting unit units,
The measurement light optical system makes the measurement laser light combined by the first multiplexer incident on the measurement cell,
The reference beam optical system guides the reference laser beam combined by the second multiplexer;
The light emission control unit switches the light emitting unit that outputs laser light every time, and causes the laser light output from one light emitting unit to enter the measurement cell,
2. The signal processing unit switches the difference detector that detects a difference signal output to the analysis device according to the light emitting unit that outputs laser light incident on the measurement cell. The optical gas measuring device described in 1. The signal processing means includes a first signal switching device that switches the difference detector that receives the light reception signal output from the first light receiving device, and the difference detection that receives the light reception signal output from the second light receiving device. A second signal switching device for switching the device,
The first signal switching device and the second signal switching device switch the difference detector that inputs a difference signal to the analysis device by switching the difference detector that inputs a light reception signal. Item 3. The optical gas measurement device according to Item 1 or 2.   3. The optical according to claim 1, wherein the signal processing unit includes a signal switching device that switches a difference signal input to the analysis device among the difference signals output from the plurality of difference detectors. Gas measuring device.   The analysis device determines the difference detector that outputs a difference signal to be used when analyzing each gas type based on the magnitude of the difference signal of each gas type, and controls the operation of the signal processing means. The optical gas measuring device according to any one of claims 1 to 4, wherein   6. The optical gas measurement device according to claim 5, wherein the signal processing means outputs a difference signal output from a difference detector having a lower detection sensitivity to the analysis device in measurement at the start of measurement. .   The signal processing means is characterized in that a difference between the sensitivity of the difference detector and the sensitivity of the difference detector adjacent to the difference detector is 5 to 20 times. Item 7. The optical gas measurement device according to any one of Items 1 to 6.   The optical gas measuring device according to any one of claims 1 to 7, wherein the signal processing means includes two difference detectors.   The light emission control unit sweeps a laser beam having a wavelength corresponding to a measurement target component to be measured in a range including a wavelength corresponding to the measurement target component, and outputs the laser light from the light emitting unit. The optical gas measuring device according to any one of claims 1 to 8. A measurement cell through which a measurement target gas flows and a plurality of laser beams including wavelengths corresponding to a plurality of components of the measurement target of the gas can be switched and output, and the emitted laser beam is branched into a measurement laser beam and a reference laser beam A measurement unit that controls the operation of the light emitting means and performs measurement. After selecting the laser beam having a wavelength corresponding to the component, making the selected laser beam incident on the measurement cell, and completing the measurement of the component to be measured, it corresponds to the component to be measured next. A light emission control means for selecting a laser beam having a wavelength and causing the selected laser beam to enter the measurement cell; a first light receiving device for receiving the measurement laser beam that has passed through the measurement cell; A light receiving means including a second light receiving device for receiving the reference laser light guided by the reference light optical system, and a difference signal between the intensity of the measurement laser light received by the light receiving means and the intensity of the reference laser light. A signal processing unit for generating, and an analysis device for analyzing a component to be measured based on the signal generated by the signal processing unit, wherein the signal processing unit includes the intensity of the measurement laser beam and the reference laser beam. An optical gas measurement method for analyzing a plurality of components contained in a measurement target gas with an optical gas measurement device including a plurality of difference detectors having different detection sensitivities for detecting a difference with intensity,
Detecting the wavelength of laser light incident on the measurement cell;
And switching the difference detector for inputting a difference signal to the analyzer based on the detected wavelength of the laser beam.

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