JP2010096561A - Calibration device for laser type gas analyzer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To facilitate calibration of a laser type gas analyzer, and to measure a moisture concentration highly accurately. <P>SOLUTION: This calibration device for the laser type gas analyzer including a light emitting unit 250 and a light receiving unit 260, capable of measuring the moisture concentration, wherein a signal processing circuit detects a double-wave signal of a modulating signal of a light source part 204 from an output signal of a light receiving part 207 and measures the concentration of a measuring object gas, includes a pipe 301 connected airtightly between both units 250, 260 and holding a prescribed optical path length of laser light, a gas cleaning bottle 500 for supplying air having a prescribed moisture concentration into the pipe 301, and an oxygen analyzer 400 for measuring an oxygen concentration in moisture-containing air supplied into the pipe 301. In the calibration device, a hydrogen concentration is converted from the measured oxygen concentration, and a measured value of the hydrogen concentration by the gas analyzer is calibrated by using the hydrogen concentration and the optical path length. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a calibration apparatus for a laser-type gas analyzer that measures the concentration of various gases such as gas in a flue and exhaust gas with laser light.

It is known that each gaseous gas molecule has its own light absorption spectrum. For example, FIG. 9 shows an example of an absorption spectrum of NH ₃ (ammonia) gas.
The laser gas analyzer is an analyzer that utilizes the fact that the amount of absorption of a specific wavelength of laser light is proportional to the concentration of the gas to be measured. The gas concentration measuring method includes a two-wavelength difference method and a frequency modulation method. It is divided roughly into. Among these, the present invention is suitable for application to, for example, a laser gas analyzer using a frequency modulation method.

First, the measurement principle of a conventional laser gas analyzer using the frequency modulation method will be described.
FIG. 10 shows a principle diagram of the frequency modulation method, which is described in, for example, Patent Document 1. The gas concentration measuring device described in Patent Document 1 is configured to measure the gas concentration from the transmitted light of the gas cell in which the measurement target gas exists.
In the frequency modulation type laser gas analyzer, the emission light of the semiconductor laser is frequency-modulated at the center frequency f _c and the modulation frequency f _m and irradiated to the gas to be measured. Here, the frequency modulation is to make the waveform of the drive current supplied to the semiconductor laser sine wave.
Since the emission wavelength of the semiconductor laser varies depending on the drive current and temperature as shown in FIGS. 11 and 12, the emission wavelength is modulated with the modulation of the drive current by performing frequency modulation.

As shown in FIG. 10, since the absorption lines of the gas is almost quadratic function with respect to the modulation frequency, the absorption line plays the role of a discriminator, the light receiving portion of the double modulation frequency f _m A frequency signal (second harmonic signal) is obtained. Since the modulation frequency f _m good at any frequency, for example, choose the modulation frequency f _m to several kHz, using a processor of the digital signal processor (DSP) or general-purpose, the second harmonic signal such as extraction Advanced signal processing can be performed.
Further, if envelope detection is performed by the light receiving unit, a fundamental wave by amplitude modulation can be estimated. By detecting the ratio between the amplitude of the fundamental wave and the amplitude of the second harmonic signal in phase synchronization, a signal proportional to the concentration of the gas to be measured can be obtained.

In this frequency modulation method, among the types of semiconductor lasers, in many cases, only a single-wavelength laser beam is emitted using a distributed feedback semiconductor laser (DFB laser) and the gas concentration is measured. In this case, since the spectral line width emitted by the DFB laser is smaller than the absorption line width of the measurement target gas, it is necessary to match the emission wavelength of the DFB laser with the absorption wavelength of the measurement target gas.
As a method for this, there is used a method in which the emission wavelength of the DFB laser is controlled by temperature using a reference gas cell in which the same gas component as that of the measurement target gas is previously enclosed.

As a conventional technique using the detection principle as described above, for example, there is a gas concentration measuring device described in Patent Document 2. FIG. 13 shows the overall configuration of the gas concentration measuring device described in Patent Document 2, and this measuring device measures the gas concentration using reflected light from a gas pipe or the like where the measurement target gas exists. To do.
The gas concentration measuring apparatus 1 mainly includes a light source unit 2, a measuring light condensing unit 3, a measuring light amplifying unit 4, a received signal detecting unit 5, a calibration signal generating unit 6, a fundamental wave signal amplifier 7A and a second harmonic signal amplifier. 7B, a reference signal amplifying unit 7 comprising a signal differential detector 8A and a signal synchronization detector 8B, a wavelength stabilizing control circuit 9, a temperature stabilizing PID circuit 10, a current stabilizing circuit 11, It comprises a measurement / calibration switching unit 12 and a calculation unit 13.

The light source unit 2 generates laser light having a wavelength that matches the absorption line peculiar to the gas to be measured as described above. As shown in FIG. 14, inside the box-shaped case body 26 made of a metal package, A semiconductor laser module 21, a reference gas cell 22, and a photodetector (light receiving unit) 23 are accommodated.
As shown in FIG. 15, a semiconductor laser (laser diode) 24 that emits frequency-modulated laser light from both sides is disposed in the case 21 a of the semiconductor laser module 21. As shown in FIG. 14, an optical cable 25 having a connector 25a extends from the case 21a, and one light emitted from the semiconductor laser 24 is externally transmitted from the measurement light condensing unit 3 in FIG. It is emitted to (atmosphere of measurement object gas).

In FIG. 14, a temperature control element (not shown) such as a Peltier element to which a cooling fin 27 is attached is disposed on the bottom surface of the case body 26. The oscillation wavelength is controlled by controlling the operating temperature to a constant temperature by this temperature control element.
As shown in FIG. 15, aspherical lenses 29 a and 29 b that do not have a flat surface for collecting emitted light are disposed on the optical axes on both the front and rear sides of the semiconductor laser 24. By using these aspheric lenses 29a and 29b as condensing lenses, light is prevented from being reflected back to the semiconductor laser 24.

As shown in FIG. 15, optical isolators 30 a and 30 b are disposed outside the aspheric lenses 29 a and 29 b on the optical axes on both the front and rear sides of the semiconductor laser 24.
These optical isolators 30a and 30b apply a magnetic field to a crystal arranged between a polarizer that passes only light with a 90 ° polarization plane and an analyzer that passes only light with a 45 ° polarization plane, The plane of polarization of the light transmitted through the crystal is rotated to prevent the reflected light from passing through the polarizer, and the reflected light is prevented from returning to the semiconductor laser 24.

14 and 15, the reference gas cell 22 disposed on the optical path on the rear side of the semiconductor laser 24 is used for stabilizing the measurement light oscillation wavelength and calibrating the measurement target gas concentration. In the reference gas cell 22, a through hole for allowing light to pass is formed on the opposite surface of the hollow metal cylinder 22a. After the reference gas is sealed inside the metal cylinder 22a, the through hole is sealed by the glass window 22b. Yes.
The reference gas cell 22 has a predetermined inner diameter, and the sealed reference gas has a composition and pressure substantially equal to the environment of the measurement target gas. For example, if the environment of the measurement location is air, the reference gas has an air balance, that is, the same composition as air, and the pressure is 1 atm.

  The reference gas cell 22 is fixed at a position where the rear emission light on the rear side of the aspherical lens 29b is likely to be incident, and the laser light that has passed through the reference gas cell 22 is received and detected by the photodetector 23 disposed on the rear side thereof. The In the reference gas cell 22, in order to reduce the return light to the semiconductor laser 24, both end surfaces through which light passes are formed obliquely (for example, about 6 ° with respect to the outgoing optical axis).

In FIG. 13, the measurement light condensing unit 3 emits the light from the semiconductor laser 24 to the outside, and condenses the measurement light reflected from the gas pipe to be measured by the lens 31. And the measurement light condensing part 3 detects the condensed light with the photodetector 32, and converts it into an electrical signal.
The measurement light amplifying unit 4 is constituted by a preamplifier, converts the photocurrent detected by the photodetector 32 into a voltage, amplifies it, and outputs it. In the measurement light amplifier 4, the fundamental wave phase sensitive detection signal (f signal: hereinafter abbreviated as fundamental wave signal) and the second harmonic phase sensitive detection signal (2 f signal: hereinafter, detected by the received signal detector 5. The optimum amplification degree is set for each of the fundamental wave signal and the second harmonic signal so that the second harmonic signal and the second harmonic signal are approximately at the same level.

The reception signal detection unit 5 processes the measurement light signal from the measurement light amplification unit 4 when the measurement / calibration switching unit 12 is switched to the measurement light amplification unit 4 side, and generates a fundamental wave signal (f signal), A second harmonic signal (2f signal) and a 2f / f signal are detected.
The reception signal detection unit 5 processes the signal from the calibration signal generation unit 6 when the measurement / calibration switching unit 12 is switched to the calibration signal generation unit 6 side, and the calibration fundamental wave signal (r _f Signal), a calibration second harmonic signal (r _2f signal), and an r _2f / r _f signal.
In the above configuration, the emission wavelength of the semiconductor laser 24 is controlled using the reference gas cell 22. Further, the concentration of the measurement target gas is measured by extracting a 2f signal indicating the gas concentration from the output of the photodetector 32.

JP 7-151681 A (paragraphs [0004], [0005], FIG. 4 etc.) JP 2001-235418 A (paragraphs [0012] to [0024], FIG. 2, FIG. 11 etc.)

The measured values measured by this type of laser gas analyzer vary in absorption intensity depending on the region where the measurement target gas exists (in other words, the propagation distance of light) and the gas concentration. It is generally expressed by the product of distances.
For example, if the same gas concentration, for example, 100 ppm of NH ₃ gas is measured at a distance of 1 m, it becomes 100 ppm · m, and if it is measured at a distance of 5 m, the absorption is 500 ppm · m. The measured value will be larger if you put.
Therefore, in an actual gas analyzer, the measured value is divided by the optical path length (the above-mentioned light propagation distance) in which the measurement target gas exists, and the gas concentration is displayed. In this regard, there is a similar description in paragraph [0004] of Patent Document 1 described above.

When the gas concentration is calculated and displayed as described above, it is necessary to calibrate the measured value of the gas analyzer based on the product of the optical path length and the gas concentration in order to guarantee the measurement performance. That is, for example, a gas cylinder is prepared in accordance with the concentration range of the measurement target gas, and the measured value of the gas concentration is calibrated to match the output.
Thus, in order to guarantee the measurement performance of the gas analyzer, calibration work is indispensable. For this purpose, it is necessary to prepare a gas having a predetermined concentration using a gas cylinder or the like.

However, there is a case where the moisture concentration is measured as a case where these gas cylinders cannot be manufactured.
FIG. 16 is a diagram showing the relationship between temperature and moisture concentration. The water concentration is determined as the ratio of the saturated water vapor pressure at each temperature, with 100% being the boiling point of water being 100%. According to FIG. 16, when calibrating with high-concentration water, the gas analyzer must be placed in an environment of 100 ° C. or higher to boil the water.
Furthermore, in order to stabilize the high concentration of water, temperature control is also required, and as a result, calibration using high concentration of water has been difficult. Even if the calibration is performed using the representative value, there is a problem that the numerical value is not accurate and the measurement value includes an error.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a calibration device that facilitates calibration of a laser gas analyzer and can measure the moisture concentration with high accuracy.

In order to solve the above-described problem, a calibration apparatus according to claim 1 includes a light source unit that emits a frequency-modulated laser beam, and an optical system that collimates the emitted light from the light source unit, and
An optical system that collects light propagated from the optical system through the space where the measurement target gas exists, a light receiving unit that receives the light collected by the optical system, and an output signal of the light receiving unit A light receiving unit having a signal processing circuit
The signal processing circuit is a laser type gas analyzer that detects a signal having a double frequency component of a modulation signal in the light source unit from an output signal of the light receiving unit and measures a concentration of a measurement target gas,
In a calibration apparatus for calibrating a laser type gas analyzer that measures the moisture concentration as the concentration of the gas to be measured,
A pipe that is hermetically connected between the light emitting unit and the light receiving unit, and that can hold a predetermined optical path length of the laser beam;
Moisture-containing gas supply means for supplying air having a predetermined moisture concentration into the pipe;
An oxygen meter for measuring the oxygen concentration in the air supplied to the inside of the pipe,
The hydrogen concentration is converted from the oxygen concentration measured by the oximeter, and the measured value of the hydrogen concentration by the laser gas analyzer is calibrated using the hydrogen concentration and the optical path length.

  A calibration apparatus according to claim 2 is the calibration apparatus according to claim 1, wherein the moisture-containing gas supply means is a gas cleaning bottle that supplies moisture-containing gas obtained by bubbling water with the atmosphere into the pipe. It is composed.

  The calibration apparatus according to claim 3 is the calibration apparatus according to claim 1 or 2, wherein the pipe includes a gas introduction port through which the moisture-containing gas flows, a gas discharge port through which the moisture-containing gas is discharged, And a port to which the oximeter is connected.

  A calibration device according to a fourth aspect of the present invention is the calibration device according to any one of the first to third aspects, wherein the light source unit is configured to change the emission wavelength of the laser element so as to scan the absorption wavelength of the measurement target gas. A laser drive signal generator for combining a wavelength scanning drive signal to be generated and a high-frequency modulation signal for modulating the emission wavelength and outputting the resultant as a laser drive signal; and the laser drive signal output from the laser drive signal generator A current control unit for converting into current, the laser element to which the current output from the current control unit is supplied, and temperature stabilization means for stabilizing the temperature of the laser element, and the signal processing A synchronous detection circuit for detecting an amplitude of the signal of the double frequency component from the output signal of the light receiving unit, and a gas to be measured from a gas absorption waveform existing in the output signal of the synchronous detection circuit; A computing section for detecting a degree, those having a.

  According to the present invention, the measured value of the moisture concentration in the laser gas analyzer has a simple configuration comprising a pipe connected between the light emitting unit and the light receiving unit, and a water-containing gas supply means such as a gas cleaning bottle. Can be easily calibrated, and the moisture detection accuracy of the gas analyzer can be improved.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, FIG. 1 is an overall configuration diagram showing an example of a laser type gas analyzer to which the calibration apparatus of this embodiment is applied. In FIG. 1, flanges 201a and 201b are fixed to walls 101a and 101b of a pipe such as a flue through which the measurement target gas passes, for example, by welding. A bottomed cylindrical cover 203a is attached to one flange 201a via a mounting seat 202a.
A light source unit 204 is disposed inside the cover 203 a, and laser light emitted from the light source unit 204 is collimated into parallel light by an optical system including a collimating lens 205. The collimated light enters the walls 101a and 101b (inside the flue) through the center of the flange 201a. The parallel light is absorbed when it passes through the measurement target gas inside the walls 101a and 101b.

  A bottomed cylindrical cover 203b is attached to the other flange 201b via a mounting seat 202b. The parallel light that has passed through the inside of the flue is condensed by the condensing lens 206 inside the cover 203b and received by the light receiving unit 207. This light is converted into an electrical signal by the light receiving unit 207 and input to the signal processing circuit 208 at the subsequent stage.

FIG. 2 shows the configuration of the light source unit 204.
The light source unit 204 includes a laser drive signal generation unit 204s including a wavelength scanning drive signal generation unit 204a and a high frequency modulation signal generation unit 204b. The wavelength scanning drive signal generation unit 204a makes the emission wavelength of the laser element variable so as to scan the absorption wavelength of the measurement target gas, and the high frequency modulation signal generation unit 204b detects, for example, the absorption wavelength of the measurement target gas. The wavelength is frequency-modulated with a sine wave of about 10 kHz.
A laser drive signal is generated by combining the output signals of these signal generators 204a and 204b in the laser drive signal generator 204s.
The laser drive signal output from the laser drive signal generation unit 204s is converted into a current by the current control unit 204c and supplied to the laser element 204e made of a semiconductor laser.

A thermistor 204f as a temperature detection element is disposed in the vicinity of the laser element 204e, and a Peltier element 204g is disposed in the vicinity of the thermistor 204f.
The Peltier element 204g is PID (proportional / integral / differential) controlled by the temperature control unit 204d so that the resistance value of the thermistor 204f becomes a constant value, and as a result, stabilizes the temperature of the laser element 204e.

As shown in FIG. 3, the output signal of the wavelength scanning drive signal generator 204a is a substantially trapezoidal signal repeated at a constant period.
In FIG. 3, the signal S2 for scanning the absorption wavelength is a portion that linearly changes the magnitude of the current supplied to the laser element 204e via the current control unit 204c. With this signal S2, the emission wavelength of the laser element 204e is gradually shifted. For example, in the case of NH ₃ gas, a line width of about 0.2 nm can be scanned.
The signal S1 is an offset portion that does not scan the absorption wavelength but causes the laser element 204e to emit light, and is set to a value equal to or greater than a threshold current value at which the light emission of the laser element 204e is stabilized.
Further, the signal S3 is a portion where the drive current is substantially zero.

FIG. 4 is a diagram showing the configuration of the signal processing circuit 208 in FIG. 1 together with peripheral circuits.
In FIG. 4, the light receiving unit 207 is configured by a light receiving element such as a photodiode having sensitivity to the emission wavelength of the laser element 204e.
The output of the light receiving unit 207 is a current signal. This current signal is converted into a voltage signal by the I / V converter 208a and input to the synchronous detection circuit 208b to which the 2f signal (second harmonic signal) from the oscillator 208c is added. Only the amplitude of the double frequency component of the modulated signal of the outgoing light is extracted. The output signal of the synchronous detection circuit 208b is sent to a calculation unit 208e such as a CPU via a noise removal filter 208d.

Next, the gas concentration measurement operation by the gas analyzer will be briefly described.
The temperature of the laser element 204e is adjusted in advance by the thermistor 204f so that the measurement target gas can be measured at the center portion of the signal S2 for scanning the absorption wavelength. By driving the laser element 204e in this state, collimated light is emitted into the walls 101a and 101b (inside the flue), and the transmitted light is incident on the light receiving unit 207.

When the measurement target gas such as NH ₃ gas does not exist inside the flue, the 2f signal is not detected by the synchronous detection circuit 208b, and the output waveform of the synchronous detection circuit 208b is almost a straight line. When the measurement target gas exists inside the flue, the absorption waveform of the measurement target gas as shown in FIG. 5 is output from the synchronous detection circuit 208b. Since the peak of the output waveform corresponds to the gas concentration, the calculation unit 208e detects the peak value of the output waveform of the synchronous detection circuit 208b from the output signal of the filter 208d, or integrates the output waveform to measure the target gas. Can be measured.

Next, a calibration apparatus used for this laser type gas analyzer will be described.
FIG. 6 is a cross-sectional view showing a state where a pipe 301 which is a part of the calibration apparatus according to the present embodiment is attached to the gas analyzer. The same components as those in FIG. 1 are denoted by the same reference numerals, and different portions will be mainly described below. In FIG. 6, reference numeral 250 denotes a light emitting unit including the light source unit 204 and the collimating lens 205, and 260 denotes a light receiving unit including the condenser lens 206 and the light receiving unit 207.

In FIG. 6, a pipe 301 is connected between the light emitting unit 250 and the light receiving unit 260 in an airtight state. Since the length of the pipe 301 serves as a reference for determining the optical path length necessary for the calibration of the moisture concentration described above, it is necessary to set the pipe length with sufficient processing accuracy.
The pipe 301 has an inner diameter that can be reliably transmitted to the light receiving unit 260 without blocking the light emitted from the light emitting unit 250.
The pipe 301 is formed with a gas inlet 302 and a gas outlet 303 at two locations along the axial direction thereof, and a water-containing gas can be circulated through the gas inlet 302 and the gas outlet 303. In addition, a port 304 to which the oximeter 400 is connected is provided at a substantially central portion in the longitudinal direction of the pipe 301.

As shown in FIG. 7, the gas introduction port 302 is supplied with a moisture-containing gas generated by an external moisture-containing gas supply means. The moisture-containing gas supply means is a gas washing bottle. 500 and flow paths 501 and 502 are provided.
That is, the gas cleaning bottle 500 bubbles the internal water W with the air supplied from the flow path 501 opened to the atmosphere, and the gas (air) containing the moisture having the concentration defined by the saturated water vapor pressure at that temperature. It is generated and discharged from the flow path 502. The tip of this flow path 502 is connected to the gas inlet 302 of the pipe 301. Reference numeral 503 denotes an exhaust passage connected to the gas outlet 303 of the pipe 301.
When a gas containing high-concentration moisture is required at the time of calibration, the gas cleaning bottle 500, the piping 301, and the flow paths 501-503 are heated by a heater, or the entire apparatus is put in a thermostatic bath or the like to raise the temperature.

The oxygen meter 400 connected to the port 304 of the pipe 301 may be based on any measurement principle and method as long as it can measure the oxygen concentration inside the pipe 301.
As the oxygen meter 400, a zirconia oxygen meter as shown in FIG. 8 can be used. In FIG. 8, a sensor element 401 has a measurement electrode 403 and a reference electrode 404 made of porous platinum formed on the outer surface and the inner surface of a solid electrolyte 402 made of bottomed cylindrical yttria-stabilized zirconia, respectively. It is created by connecting 403 and 404 to the circuit board 409 via lead wires 405 and 406. Although not shown, the circuit board 409 is equipped with a calculation unit for calculating the oxygen concentration and the like from the output signals of the electrodes 403 and 404.
The sensor element 401 is inserted and bonded inside a heater 408 built in the sensor housing 407. Reference numeral 410 denotes a vent provided in the sensor housing 407, and 411 denotes a protective layer for the measurement electrode 403.

Stabilized zirconia, which is a material of the solid electrolyte 402, is made by adding yttria (Y ₂ O ₃ ) or the like as a stabilizer to zirconia (zirconium oxide ZrO ₂ ) as a main component. In actual use, it is necessary to keep the solid electrolyte 402 at a high temperature of 500 ° C. or higher by the heater 408.
In a high temperature state of 500 ° C. or higher, stabilized zirconia has the property of a solid electrolyte (ionic conductive solid) and selectively allows only oxygen ions (O ₂ ⁻ ) to pass therethrough. That is, if there is a difference in oxygen concentration between the inside and outside of the cylindrical solid electrolyte 402, oxygen molecules (O ₂ ) receive electrons and become oxygen ions (O ₂ ⁻ ) (reduction reaction) at the higher concentration side electrode. In the electrode on the lower concentration side, oxygen ions (O ₂ ⁻ ) release electrons and return to oxygen molecules (O ₂ ) (oxidation reaction). These reaction formulas are as follows.
High oxygen concentration side: O ₂ + 4e → 2O ₂ ⁻ (reduction reaction)
Low concentration side of oxygen: 2O ₂ ⁻ → O ₂ + 4e (oxidation reaction)

At this time, an electromotive force determined by the oxygen concentration ratio is generated between the measurement electrode 403 and the reference electrode 404. That is, the oxygen concentration ratio can be measured by measuring the voltage generated between the electrodes 403 and 404 with a measuring instrument having a high input impedance.
Therefore, if one electrode (for example, the measurement electrode 403 outside the solid electrolyte 402) is brought into direct contact with the atmosphere and is kept at a constant oxygen concentration corresponding to the oxygen partial pressure in the atmosphere, the other through the vent 410. The oxygen concentration in the moisture-containing air in contact with the first electrode (the reference electrode 404 inside the solid electrolyte 402) can be obtained.

Next, in the apparatus configuration as described above, air is bubbled by the gas cleaning bottle 500, and a moisture-containing gas having a predetermined concentration is supplied into the pipe 301 from the flow path 502 and the gas inlet 302, so that the moisture concentration of the gas analyzer is supplied. An operation for calibrating the measured value will be described.
The oxygen meter 400 shown in FIG. 8 measures the oxygen concentration of the moisture-containing air in the pipe 301 supplied from the vent 410, and converts the moisture concentration from this oxygen concentration.
That is, when water W is bubbled in the atmosphere by the gas cleaning bottle 500 and the water-containing air supplied from the flow path 502 is filled in the pipe 301, the air in the pipe 301 has an oxygen concentration corresponding to the increase in the moisture concentration. descend.
For example, if the oxygen concentration in the atmosphere supplied from the flow path 501 to the gas cleaning bottle 500 is 20.7%, and this is bubbled by the gas cleaning bottle 500, the oxygen concentration of the moisture-containing air is reduced to 20%. Suppose that In this case, since the moisture concentration increases by 0.7% with respect to the oxygen concentration of 20.7%, the moisture concentration of the moisture-containing air is 3.38% according to Equation 1.
[Formula 1]
Moisture concentration = (Oxygen concentration in the supply air−oxygen concentration after bubbling) / Oxygen concentration in the supply air × 100%

As described above, the moisture concentration can be converted from the oxygen concentration in the pipe 301 measured by the oximeter 400.
Therefore, if the product of the moisture concentration is used as a reference value and the product of the optical path length determined from the axial length of the pipe 301, the measured value of the moisture concentration by the laser gas analyzer can be calibrated.
In addition, when calibrating a high moisture concentration using a heater or the like as in the prior art, it is necessary to stabilize the heater temperature with high accuracy, but in this embodiment, the moisture concentration is based on the oxygen concentration of moisture-containing air. Is easy to calibrate.

It is a lineblock diagram of a laser type gas analyzer to which an embodiment of the present invention is applied. It is a block diagram of the light source part in FIG. FIG. 3 is an output signal waveform diagram of a wavelength scanning drive signal generation unit in FIG. 2. It is the figure which showed the structure of the signal processing circuit in FIG. 1 with the peripheral circuit. It is a figure which shows the position shift of a gas absorption waveform. It is explanatory drawing of the principal part of the calibration apparatus in embodiment of this invention. It is explanatory drawing of the calibration apparatus in embodiment of this invention. It is a block diagram which shows an example of the oxygen meter in FIG. NH ₃ is an absorption spectrum of a gas. It is a principle diagram of a frequency modulation system. It is a figure which shows the change of the light emission wavelength of the semiconductor laser by a drive current. It is a figure which shows the change of the light emission wavelength of the semiconductor laser with temperature. It is a whole block diagram of the gas concentration measuring apparatus described in patent document 2. It is a block diagram of the principal part in FIG. It is a block diagram of the principal part in FIG. It is a figure which shows the relationship between temperature and a water concentration.

Explanation of symbols

101a, 101b: Walls 201a, 201b: Flange 202a, 202b: Mounting seats 203a, 203b: Cover 204: Light source unit 204a: Wavelength scanning drive signal generation unit 204b: High frequency modulation signal generation unit 204c: Current control unit 204d: Temperature control unit 204e: Laser element 204f: Thermistor 204g: Peltier element 204s: Laser drive signal generation unit 205: Collimator lens 206: Condensing lens 207: Light receiving unit 208: Signal processing circuit 208a: I / V converter 208b: Synchronous detection circuit 208c: Oscillator 208d: Filter 208e: Arithmetic unit 250: Light emitting unit 260: Light receiving unit 301: Piping 302: Gas inlet 303: Gas outlet 304: Port 400: Oxygen meter 401: Sensor element 402: Solid electrolyte 403: Measuring power Electrode 404: Reference electrode 405, 406: Lead wire 407: Sensor housing 408: Heater 409: Circuit board 410: Vent 411: Protective layer 500: Gas cleaning bottle 501, 502, 503: Flow path W: Water

Claims (4)

A light-emitting unit having a light source unit that emits frequency-modulated laser light, and an optical system that collimates the light emitted from the light source unit;
An optical system that collects light propagated from the optical system through the space where the measurement target gas exists, a light receiving unit that receives the light collected by the optical system, and an output signal of the light receiving unit A light receiving unit having a signal processing circuit
The signal processing circuit is a laser type gas analyzer that detects a signal having a double frequency component of a modulation signal in the light source unit from an output signal of the light receiving unit and measures a concentration of a measurement target gas,
In a calibration apparatus for calibrating a laser type gas analyzer that measures the moisture concentration as the concentration of the gas to be measured,
A pipe that is hermetically connected between the light emitting unit and the light receiving unit, and that can hold a predetermined optical path length of the laser beam;
Moisture-containing gas supply means for supplying air having a predetermined moisture concentration into the pipe;
An oximeter for measuring the oxygen concentration in the air supplied into the pipe;
With
A laser gas analysis characterized by converting a hydrogen concentration from an oxygen concentration measured by the oximeter and calibrating a measured value of the hydrogen concentration by the laser gas analyzer using the hydrogen concentration and the optical path length. Meter calibration device. In the laser gas analyzer calibration apparatus according to claim 1,
A calibration apparatus for a laser gas analyzer, wherein the moisture-containing gas supply means comprises a gas cleaning bottle that supplies a moisture-containing gas obtained by bubbling water in the atmosphere into the pipe. In the laser gas analyzer calibration apparatus according to claim 1 or 2,
The pipe includes a gas inlet through which the moisture-containing gas flows, a gas outlet through which the moisture-containing gas is discharged, and a port to which the oximeter is connected. Analyzer calibration device. In the laser gas analyzer calibration apparatus according to any one of claims 1 to 3,
The light source unit synthesizes a wavelength scanning drive signal for changing the emission wavelength of the laser element so as to scan the absorption wavelength of the gas to be measured and a high-frequency modulation signal for modulating the emission wavelength as a laser drive signal. A laser drive signal generator for outputting, a current controller for converting the laser drive signal output from the laser drive signal generator into a current, and the laser element supplied with the current output from the current controller; And a temperature stabilization means for stabilizing the temperature of the laser element, and
The signal processing circuit detects the amplitude of the double frequency component signal from the output signal of the light receiving unit, and the concentration of the measurement target gas from the gas absorption waveform existing in the output signal of the synchronous detection circuit. A laser gas analyzer calibration apparatus comprising: a calculation unit for detection.

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