JPS591973B2 - Digital integrating spectrometer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a spectrometer for qualitative and quantitative analysis of gases, and in particular to a spectrometer capable of performing long-term integration and measuring the average concentration during the measurement period. The present invention relates to a spectrometer that can be used as a useful measuring device for measuring environmental atmospheric pollution, which has been attracting attention in recent years.

J The higher-order derivative method (
(also known as higher-order differential method).

This higher-order derivative method means that when an absorption spectrum is differentiated with respect to wavelength, the first-order derivative spectrum greatly captures slight changes in the original absorption spectrum before differentiation, and the spectral profile becomes sharp. Furthermore, since the second-order differential spectrum obtained by differentiating this first-order differential spectrum becomes even sharper, qualitative and quantitative analyzes of substances are performed using these first-order or second-order differential spectra. A spectrometer based on this principle is temporally modulated in a sinusoidal wavelength near a predetermined measurement target wavelength, and a light intensity modulation signal with a frequency equal to or twice the modulation frequency f, 2f, is detected. There is a spectrometer that measures the first or second differential value of the spectrum at the wavelength to be measured. When using this spectrometer, if there is a characteristic structure in the absorption spectrum of the gas being measured, the wavelength that shows the characteristic structure (for example, the wavelength that shows a sharp absorption maximum or minimum in the absorption spectrum) can be detected at the measurement target wavelength. As mentioned above, by measuring the first or second derivative of the spectrum at the wavelength to be measured, qualitative and quantitative analyzes can be performed simultaneously and instantaneously. There is an advantage that there is no need to slowly scan the absorption spectrum to measure the absorption spectrum, and the wavelength to be measured can be fixed, allowing for continuous measurement over time. Furthermore, this spectrometer is capable of measuring the concentration of pollutants such as SO2 gas, NO gas, and NO2 gas present in the ambient air in terms of sensitivity. Here we will briefly discuss the measurement of pollutant gases in the ambient atmosphere. In our country,
Since the environmental standard concentration of SO2 gas or NOx (NO gas and NO2 gas are collectively called NOx) in the ambient air is shown as an hourly average value, it is possible to calculate the concentration of these pollutants in the ambient air. When measuring, it is necessary to measure the average value for one hour. Currently, wet methods are mainly used to measure the concentration of pollutant gases in the ambient air.
Mainly, only the hourly average value is measured. Let me explain this in a little more detail. For example, when measuring the concentration of SO2 gas in the ambient air, air is continuously sampled and hydrogen peroxide solution (H2O2 + H2O) is aerated, and at this time hydrogen peroxide solution is poured into the aerated atmosphere. When SO2 gas is present, SO2 reacts with H2O2 to form sulfuric acid H2SO4. When sulfuric acid is produced in hydrogen peroxide, the electrical conductivity increases. Therefore, when the electrical conductivity is recorded with a recorder while continuously passing hydrogen peroxide through the atmosphere, a monotonically increasing chart is drawn on the recording paper that increases over time and reaches its maximum value after one hour. After venting the atmosphere for one hour, the hydrogen peroxide solution is automatically replaced with new one and the next cycle of measurement is performed. That is, a sawtooth chart with a period of one hour is drawn on the recording paper. At this time, 1
The recorder is calibrated so that the maximum value of the sawtooth wave of the chart on the recording paper obtained when the atmosphere is aerated for an hour indicates the average value for one hour. As explained above, in the conventional wet method, the 1-hour average concentration is read from the maximum value of the sawtooth chart on the recording paper (value after 1 hour of ventilation), and the instantaneous precipitation value during that measurement cycle is the value of the sawtooth chart. I can roughly tell from the rate of increase. Therefore, when trying to use a spectrometer based on the higher-order differential method that measures the first or second derivative of specator as described above to measure the concentration of pollutant gases in the ambient air, it is difficult to measure the hourly average concentration. must be measured.

The reason is as follows. In other words, while environmental monitoring has traditionally been carried out by local governments, measurement points (locations where measurements are taken) are distributed throughout the country, and measurements at these measurement points have to be compared with each other, and in the past, Administrative guidance is being given to purify the ambient air by mutual comparison with measured values. It is important to compare the measured values with each other in this way, and since the current measured value is an hourly average concentration, if you try to use a spectrometer to measure the concentration of pollutant gases in the ambient air, it will be difficult to compare the hourly average concentration. The spectrometer must be capable of measuring As explained above, there are two reasons for this: the environmental standard concentration is expressed as an hourly average value, and it must be compared with the measured values obtained by the current wet method, which can only measure hourly average concentrations. In order to use a spectrometer based on the higher-order differential method to measure pollutant gases in the ambient air, it must be able to measure hourly average concentrations.

However, with conventional spectrometers, it was not possible to measure the 1-hour average concentration. To measure the hourly average concentration using a spectrometer, it is necessary to integrate the instantaneous measurement output of the spectrometer for one hour, but conventional integrators have various drawbacks.

That is, the analog integration circuit cannot perform integration over a long period of time such as one hour. If an attempt is made to use a general-purpose digital integrator that performs continuous integration by AD converting analog quantities, a large-capacity integrator would be required, which is undesirable.
If an attempt is made to use a general-purpose digital integrator that performs AD conversion of an analog quantity and performs integration while sampling at a fixed short period, a large-capacity integrator is required, which is uneconomical and undesirable. A digital integrator with too long a sampling period will not be able to accurately integrate instantaneous measurement outputs. No matter how good the sampling period is, a small-capacity digital integrator cannot provide a wide dynamic range. In addition, general-purpose digital average value calculation devices can have a relatively wide dynamic range even with a small-capacity storage circuit, but their output is always only a time-averaged value, which is the output format of the conventional wet method. I can't draw a serrated chart. in this case,
When trying to compare data with conventional wet method data, there were drawbacks such as the fact that a true comparison could not be made because the output format was different. In view of the above points, the present invention converts the instantaneous measurement output of the spectrometer into an AD converter within the electrical processing system of the spectrometer, and then digitally integrates it for one hour while sampling it at a constant cycle. By configuring the spectrometer to be pre-calibrated so that the value is the hourly average concentration,
It is an object of the present invention to provide a spectrometer that can measure an hourly average concentration in an output format that is exactly the same as the output format of a conventional wet method, and can also measure instantaneous concentrations at the same time.

Next, an embodiment of the present invention will be described based on FIG.

In the figure, light emitted from a light source 1 is made into a parallel beam by a collimator lens 5, and then a light absorption cell 10 is installed inside the light absorption cell 10 for collecting the atmosphere and generating an absorption spectrum. The light enters through the entrance window 11. Atmospheric air is continuously introduced into and exhausted from the light absorption cell 10 through an intake port 13 and an exhaust port 14 . The parallel light beam that enters the inside of the light absorption cell 10 is reflected multiple times by the mirrors (21, 22, etc.) of the repeating reflection optical device 20 provided inside the light absorption cell, and then passes through the exit window of the light absorption cell. The light is emitted from the spectrometer 12, is further focused by the collector lens 30 onto the fixed input loss slit 41 of the spectrometer 40, and enters the interior of the spectrometer 40. The light incident on the spectrometer 40 is wavelength-dispersed by the dispersion mechanism 42 of the spectrometer, and monochromatic light passes through the exit slit 55.The light-receiving surface of the head window photomultiplier tube 80 has a substantially uniform light-receiving surface. incident on . The exit slit 55 is formed in a slit plate 50, and the slit plate 50 is attached to a slit vibration device 60. By vibrating the slit vibrating device by the drive circuit 70, the exit slit 55 is made to vibrate sinusoidally in the lateral direction (x direction in FIG. 1) over time, and the light passing through the exit slit is The wavelength is temporally modulated sinusoidally.
Here, taking the measurement of SO2 gas as an example, the exit slit 55 is vibrated around the wavelength showing the maximum absorption of SO2 gas (for example, 300 nm) with an amplitude of about 2 nm, and the angle of the vibration is An analog electric circuit 90 detects an AC signal corresponding to a light intensity modulation signal with a frequency 2ω, which is twice the frequency ω, to generate a DC output signal corresponding to the second derivative of the absorption spectrum of SO2 gas.
The DC signal of this analog electric circuit 90 is an output corresponding to the instantaneous value of the SO2 gas concentration, and this DC output signal is input to one input A of the two-input recorder 96 to calculate the instantaneous value of the SO2 gas concentration over time. (indicated by AO in the figure). At this time, the scale of the two-input recorder 96 and the SO2
By calibrating the relationship with the gas concentration in advance, the instantaneous value of the SO2 gas concentration can be read from the recording paper. On the other hand, the DC output signal of the analog electric circuit 90 is input to the digital electric circuit 200, and the integration starts from an arbitrarily determined integration start time, and the integration results are outputted every moment to the other input B of the two-input recorder 96. and record it.

If the scale of the two-input recorder is calibrated in advance so that the 1-hour integration result on the recording paper indicates the 1-hour average concentration of SO2 gas, the 1-hour average concentration can be directly read from the recording paper. When the integration for one hour is completed, the integrated output value is reset to zero in order to start the next integration, and the integration for the next cycle is started. Therefore, a sawtooth chart with a period of one hour is drawn on the recording paper. This situation is shown in figure B. It was shown in Next, the slit vibrating device 60 is shown in FIG. 2, and will be described in detail based on the same figure.

In FIG. 2, a U-shaped tuning fork 61 with a high natural frequency and high Q is used as a vibration source for the exit slit 55. A plate-shaped body 50 with an outlet slit 55 formed therein is attached to the free end of one leg of this U-shaped tuning fork via a holder 63, and a balancer 62 for keeping the balance of the tuning fork is attached to the free end of the other leg. The oscillator has a very high Q. The U-shaped tuning fork 61 is made of a magnetic material, and a pickup electromagnetic head 64 provided on one leg picks up the natural vibration of the vibrator, and a drive electromagnetic head 65 provided on the other leg picks up the vibrator. is driven by. Both electromagnetic heads 64 and 65 have cores 68, 68' and core 68.
, 68' coils 69, 69! It consists of A constant current is always supplied to the coil 69 of the pickup electromagnetic head 64 from a constant current generation circuit 71 built into the drive circuit 70, and the electromagnetic head 64 acts as an electromagnet, so that when the leg of the tuning fork 61 vibrates, the coil 69 An alternating current is induced at 69. This induced alternating current is amplified by an amplifier 73 built into the drive circuit 70, and a drive voltage is applied to the drive electromagnetic head through a drive voltage adjustment circuit 74 to keep the vibration of the vibrator at a constant amplitude. . In order to keep the amplitude of the vibrator constant, the picked-up alternating current is amplified by an amplifier 75, and this alternating current is passed through a full-wave rectifier circuit 76 and a low-pass filter 77 to a value corresponding to the absolute value of the picked-up alternating current. A drive voltage adjustment circuit 74 automatically adjusts the drive voltage so that an output is generated, and as the output increases, the drive voltage decreases. Next, the analog electric circuit 90 used in the embodiment of the present invention (FIG. 1) is shown in FIG. 3 and will be described in detail.

In the same figure, the electrical output signal of the photomultiplier tube 80 is amplified by a preamplifier 120, and after its DC component is removed by a capacitor 121, the electrical output signal is amplified by a bandpass filter 122, which is twice the frequency ω of the exit slit. An AC signal with a frequency of 2ω is taken out, further amplified by an amplifier 123, and input to a synchronous switch circuit 124. This synchronous switch circuit 124 is turned on when the modulation signal of frequency 2ω is a positive half-wave, and turned off when it is a negative half-wave, thereby performing half-wave rectification of the signal. Furthermore, when the polarity of the output of the amplifier 123 is inverted by the polarity inverting circuit 125, the negative half of the output signal of the amplifier 123 becomes a positive half wave, so this positive half wave is taken out by the synchronization switch circuit 124' and synchronized. By combining the output signal of the switch circuit 124 with the input signal of the low-pass filter 130, the output signal of the amplifier 123 is full-wave rectified. Synchronous switch circuits 124 and 124
The synchronizing signal of ' is generated by passing the drive signal of the frequency ω of the drive circuit 70 through the phase shifter 110 for phase adjustment,
11 to generate a signal with a frequency of 4ω, and a frequency divider 112 to generate two rectangular waves with a frequency of 2ω whose phases are shifted by 1800 from each other. The aforementioned full-wave rectified signal is smoothed by a low-pass filter 130 and then enters the numerator of a divider 135. On the other hand, the DC component of the output of the preamplifier 120 is amplified by the DC amplifier 131 and then input into the denominator of the divider 135. In this way, the output of the divider 135 is set to a value corresponding to the modulation degree of the modulation signal that does not depend on the light source intensity, etc., and this is set to 2
into one input of the input recorder 96. At this time, if the scale of the recorder and the concentration of the gas to be measured (SO2 gas in the example) are calibrated in advance, the instantaneous value of the gas concentration can be continuously recorded. Next, digital electric circuit 2
A first embodiment of 00 is shown in FIGS. 4 and 5 and will be described in detail.

In FIG. 4, 201 is a VF converter, which converts the DC output voltage (analog amount) of the analog electric circuit 90 into a pulse (digital amount) having a frequency proportional to the DC output voltage (analog amount).
Since the DC output voltage of the analog electric circuit 90 changes over time in accordance with changes in gas concentration, the frequency of the pulses generated by the VF converter 201 changes moment by moment. Integration is performed by counting the number of pulses, but since continuous counting requires a counter with a large capacity, the counter is sampled and counted at an appropriate period. 202 is a gate circuit for sampling.

The sampling period (the period when the gate is open) and the gate width (the time during which the gate is open) are determined by the time base circuit 207.
It is determined by the clock pulse generated in gate circuit 2.
The function of 02 is to output the AND of the output pulse of the VF converter and the clock pulse. The pulses that have passed through the gate circuit 202 in this way are transferred to the frequency counter 2.
Count at 03 and add up each time the gate opens.
After one hour of integration in this manner, a reset signal is generated by the time base circuit 207 to clear and set the integration result of the frequency counter 203. The sampling period was determined as follows. In other words, since fluctuations in the concentration of pollutant gases in the ambient air are on the order of several tens of seconds in terms of time, the sampling theorem allows us to measure the fluctuations in the concentration of pollutant gases by sampling at a sampling period of 10 seconds or less. can be calculated correctly. Furthermore, the DC output of the analog electric circuit 90 contains very low-frequency noise having various frequency components, and the highest frequency among these noises is about 0.05 Hz at most. By sampling at sub-second sampling periods, these noises can be averaged out.
The sampling period was set to 10 seconds or less because the result of integration for 1 hour has a better S/N value and can improve measurement sensitivity and measurement accuracy. The gate width when the gate circuit 202 is open is about 100ttsec to 10msec, and when the frequency of the pulse entering the gate is low (when the output of the analog electric circuit 90 is small), the gate width is widened and the frequency of the pulse is high. Time (analog electrical circuit 90
(When the output of Furthermore, when the gas concentration is low, the proportion of noise components in the output of the analog electric circuit increases, so the sampling period was shortened to further improve the S/N ratio, so changing the sampling period was also used when changing the range. Also, when the gas concentration is almost zero, the analog electric circuit 90
There is only a noise component in the output of the analog electric circuit, and at this time, the output of the analog electric circuit becomes a positive voltage or a negative voltage due to the noise, and becomes zero on average. When a signal that goes back and forth between a positive voltage and a negative voltage is converted into a pulse by the VF converter 201, a pulse with a frequency proportional to the voltage is generated for a positive voltage, but a pulse with a frequency proportional to the voltage is generated for a positive voltage. In contrast, no pulse is generated at all.
Therefore, when this number of pulses is integrated, a positive integrated value is always obtained, and this is different from zero, which is the integrated result of the analog quantity, so when the gas concentration is low, correct integration cannot be performed as it is. Therefore, using a circuit as shown in FIG. 5, the reference voltage circuit 208 and the adder circuit 2 are
09, the output of the analog electric circuit 90 is raised in advance to prevent the voltage entering the VF converter 201 from becoming negative. Then, a subtraction circuit 205 subtracts the raised reference voltage from the integrated value. That is, the DC output voltage of the reference voltage circuit 208 is converted into a pulse with a frequency proportional to the DC voltage by the VF converter 201, and then sampled and integrated by the gate circuit 202' and the frequency counter 203'. Since the integration result of the frequency counter 203 is the sum of the signal integration value and the reference voltage integration value, the subtraction circuit 205 calculates the reference voltage integration value (frequency counter 203') from this value.
After subtracting the correct integrated value of the signal, the DA converter 206 converts it into an analog quantity (DC voltage). This DA converter output is input to the 2-input recorder 9.
6 in one B and recorded continuously over time, B in Fig. 1 is obtained. A serrated chart is drawn as shown in
The analog electrical circuit output is input to the other input A of the two-input recorder, and the analog electrical circuit output is input to the other input A of the two-input recorder. The instantaneous values shown in are drawn. The digital integration using the VF converter described above has the advantage of being able to accurately switch ranges by changing the sampling period or gate width, but when the gas concentration is low, pulses with a frequency proportional to the gas concentration can be used. Since the number of pulses is small, the ratio of counting error (sampling error) to the signal when counting the number of pulses passing through the limited gate width becomes large, resulting in poor measurement accuracy. On the other hand, by performing voltage-code conversion, it is possible to eliminate the drawback of poor measurement accuracy during sampling even when measuring low concentration gases. Examples of such implementation are described below. FIG. 6 shows a second embodiment of the digital electrical circuit and will be described in detail below.

The output voltage of the analog electric circuit 90 is set to the reference voltage circuit 208.
is raised in advance by the adder circuit 209, and
Converter 211 converts it into a code (code), and stores it in the storage circuit 21.
2 and sampled, this output is input into one of the adders 213.

The output of the adder 213 is input into the storage circuit 214 which is cleared in advance at the start of the integration, and the next sampling value is added to the storage circuit of the storage circuit 214 and the addition circuit 213 to perform the integration. The sampling period is determined by a clock pulse generated by time base circuit 217. The AD converter 211 uses a unipolar type, and therefore, as in the first embodiment,
In order to perform correct integration when the analog electric circuit output takes a negative voltage, the analog electric circuit output is raised in advance by the reference voltage circuit 208 to prevent it from taking a negative voltage. This reference voltage is encoded by an AD converter 21V and then integrated by an adder 213' and a storage circuit 214'. The subtraction circuit 2 calculates the integration result of this reference voltage from the signal integration value (inflated by the reference voltage).
Subtract by 15. The accumulated value of the correct signal obtained in this way is converted into an analog quantity (DC voltage) by the DA converter 216, and is input to the B input of the two-input recorder 96. After one hour of integration, the time base circuit 217 generates a reset signal, which clears the memory circuits 214 and 214'.

In the second embodiment of the digital electric circuit 200 described above, a unipolar AD converter 211 is used, but a bipolar AD converter 211 is used.
If a D converter is used, there is no need to increase the analog electric circuit output in advance, and the circuit configuration can be simplified.

Such a third embodiment is shown in FIG. In the figure, a bipolar AD converter 220 converts DC voltage into a code, which is stored in a storage circuit 221, and then integrated by an adder 222 and a storage circuit 223. The sampling period and integration time are determined by the clock pulse set signal generated by the time base circuit 225, respectively. 224 is D
The output of the DA converter 224 is input to the B input of the two-input recorder 96.

In the second and third embodiments described above, the dynamic range cannot be very wide.

Therefore, if there is a possibility that the analog electric circuit output may become large, it is recommended to insert an attenuator between the output of the lock-in amplifier 90 and the input of the digital integration circuit, and change the attenuation ratio of this subtracter. Therefore, it is necessary to devise measures similar to those used when changing ranges. In the first, second, and third examples of digital electric circuits explained above, the range can be changed manually, but if the range setting is incorrect, the memory circuit or frequency counter (hereinafter referred to as Even if the capacity of the integration circuit (called an integration circuit) is exceeded, the integration circuit is automatically tagged and integrated again from zero, so it is very effective to record the integration output signal with a recorder. .

FIG. 8 shows a chart on the recording paper of the one-hour integration when the memory circuit is saturated and cleared. In the figure, the t-axis indicates the time axis, and the E-axis indicates the magnitude of the integrated output. The origin 0 is a point where the cumulative time is zero and the cumulative output is zero. As the integration time elapses, the integration output increases and when it exceeds the capacity of the integration circuit, the integration circuit is automatically cleared and the integration output becomes zero. This time is indicated by C in FIG. The integration output immediately before the integration circuit is cleared is a constant determined by the capacity of the integration circuit, and is represented by E in the figure. It was shown in The integration is further progressed in time, and the integration start time is 0.
When one hour has passed since then (indicated by T in the figure), the integration circuit is cleared again by the set signal. The integrated output signal immediately before being cleared is indicated by E1 in the figure. Chart B of such an integrated output signal. The integrated value for 1 hour immediately becomes E. +E1 can be read. At this time, the E axis is a linear scale for the hourly average concentration, so EO + E
1 directly indicates the 1 hour average concentration. As explained above, it is very effective to record the integrated output signal with a recorder. Next, a modification of the digital integration type spectroscopic type will be described.

In the embodiment of the present invention shown in FIG. 1, the exit slit 55 of the spectrometer is vibrated to apply wavelength modulation to the light emitted from the exit slit, but the exit slit is fixed and the optical axis inside the spectrometer is Wavelength modulation may be applied to the light exiting the exit slit by arranging a vibrating mirror or a transmissive refraction plate that undergoes torsional vibration above.

In the embodiment of the present invention shown in FIG. may be placed.

However, if this arrangement is used, the exit slit 55
When the light beam is vibrated, the light beam emitted from the exit slit 55 is also deflected, and the mirrors (21 and 22, etc.) of the repeating reflection optical device 20 built into the light absorption cell 10 are contaminated, and the periphery of the light beam crosses the mirror, resulting in zero light. Since a time signal (a signal that occurs even when the concentration of the gas to be measured is zero) is generated, which is undesirable, it is necessary to vibrate the input loss slit or use a vibrating mirror or torsional vibration on the optical axis inside the spectrometer. Preferably, the light exiting the fixed exit slit using a plate is wavelength modulated. Further, in the embodiment of the present invention, as shown in FIG. 2, the natural vibration of a tuning fork is used as the vibration source of the slit vibrating device, but a parallel spring or a speaker may be used instead of the tuning fork.

Further, in the embodiment of the present invention, the analog electric circuit is a synchronous detection rectifier circuit, but it may be an analog circuit that peak-detects the amplitude of an AC signal.

Further, in the embodiment of the present invention shown in FIG. 1, there was only one exit slit, but for example, there are three exit slits and three photomultiplier tubes are arranged corresponding to each exit slit. A total of three analog electric circuits and three digital electric circuits can be connected in cascade corresponding to each photomultiplier tube to create a spectrometer that can simultaneously measure three component gases. In this case, one 6-input recorder or three 2-input recorders are required. As explained above, according to the present invention, (a) the digital integrated quantity is converted into an analog quantity by the DA converter at the final stage of the digital electric circuit, and the process of integrating is recorded by the recorder, so that the conventional environmental atmospheric It was possible to obtain a sawtooth record with an output format exactly similar to the sawtooth one-hour record of automatic measuring instruments that have been used to measure pollutant gases inside.

As a result, it became possible to mutually compare data measured using the spectrometer according to the present invention with data measured using a conventional automatic measuring instrument, and it was possible to provide a spectrometer that can be used for automatic measurement of environmental atmosphere. (b) The scale of the recorder was calibrated in advance so that the 1-hour integrated value, which increased in a sawtooth pattern, would directly indicate the 1-hour average density, making it possible to read the 1-hour average density directly from the recording paper. (c) Since the instantaneous measurement output signal (analog electrical circuit output signal) and integrated value (digital electrical circuit output signal) are recorded simultaneously with the same recorder, the instantaneous value and integrated value can be clearly seen at a glance, improving environmental purification. It is now possible to obtain data that is useful for data analysis.

(d) Digitally integrating the analog electrical circuit output made it possible to create a highly accurate integrating spectrometer.

(e) Since the analog electrical circuit output was sampled and integrated at a sampling period based on the sampling theorem,
It was possible to construct an integration circuit using small-capacity adders, memory circuits, etc., and it was also possible to perform accurate integration.

(f) Since the sampling period was determined based on the sampling theorem after determining the noise component superimposed on the analog electric circuit output, it is possible to average the noise component in the process of integration. The S/N of the time integrated value was improved.

(b) Since manual range switching was performed, it was possible to provide a digital integrating spectrometer with a wide dynamic range using a digital integrating circuit composed of a small-capacity adder and a memory circuit.

(7) Since the integrated output signal of the digital electric circuit is recorded continuously over time with a recorder, even if the storage capacity is exceeded during integration due to incorrect range setting, the data will be recorded within 1 hour from the top of the chart. I was able to read the integrated output.

Important effects such as:

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a digital integration type spectrometer according to the present invention. FIG. 2 is a block diagram of a wavelength modulation device (slit oscillation device) used in an embodiment of the digital integrating type spectroscopic type according to the present invention. FIG. 3 is a block diagram of an analog electric circuit used in an embodiment of the digital integrating type spectroscopic type according to the present invention. Fourth
5 are block diagrams showing a first embodiment of a digital integration type spectroscopic digital electric circuit according to the present invention. FIG. 6 is a block diagram showing a second embodiment of a digital integration type spectroscopic digital electric circuit according to the present invention.
FIG. 7 is a block diagram showing a third embodiment of a digital integration type spectroscopic digital electric circuit according to the present invention. 1
...Light source, 10 ... Light absorption cell, 20
...Repetitive reflection optical device, 40...Spectrometer, 41...Entrance slit, 42...
・Dispersion mechanism, 55...Exit slit, 60...
...Exit slit vibrator, 80...Photomultiplier tube, 90...Analog electric circuit, 200
...Digital electrical circuit, 96...2
An input recorder is shown.

Claims (1)

[Scope of Claims] 1. A spectrometer including a light source and a wavelength modulation device that temporally modulates the light emitted from the exit slit in a sinusoidal waveform; a photoelectric converter that receives the output signal and converts it into an electrical signal; a light absorption cell disposed on the optical path from the light source to the photoelectric converter through the spectroscope; An analog electrical circuit that generates an analog output signal corresponding to the second derivative of the absorption spectrum of a gas to be measured contained in the atmosphere that is continuously sampled and introduced into the light absorption cell, and an analog output signal of the analog electrical circuit. an AD converter that converts the output signal into a digital quantity, a digital integration circuit that integrates the output signal of the AD converter at a predetermined integration cycle while sampling at a constant sampling cycle, and an integrated output signal of the integration circuit into an analog quantity. a digital electric circuit including a DA converter for converting, and a time base circuit for generating signals indicating the integration period and the sampling period; A digital integrating spectrometer consisting of a multi-input analog recorder that records simultaneously. 2. The digital integrating spectrometer according to claim 1, wherein the light absorption cell is disposed between the light source and the spectrometer. 3. The digital integrating spectrometer according to claim 1, wherein the wavelength modulation device is an exit slit vibration device using a tuning fork as a vibration source. 4. Digital integration according to claim 1, in which a plurality of exit slits are arranged, and the same number of photoelectric converters, analog electrical circuits, and digital electrical circuits as the exit slits are provided to enable simultaneous multi-component measurement. shape spectrometer.