JPH056526Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The present invention employs a unique method that has not been seen before, called the multi-fluid modulation method (this is the name given by the inventors). Thus, while using only one detector, two sample fluids (or split into two systems) can be analyzed simultaneously and continuously with great precision. This was done with the aim of providing a completely new fluid analyzer equipped with a mechanism capable of reducing measurement errors due to transient response interference effects between the two sample fluids, so as to obtain even higher measurement accuracy. It is.

[Conventional technology]

For example, it is used to analyze the concentration (and thus the amount) of harmful components (NOx, HyCz, or COx, etc.) contained in the atmosphere, which is an example of a sample fluid, such as automobile exhaust gas or factory exhaust gas. Conventionally, fluid analysis devices include analyzers equipped with a chemical luminescence detector (CLD), analyzers equipped with a flame ion detector (FID), condenser microphone method, microflow method, etc. Various types of detectors (sensors), such as pneumatic detectors and non-dispersive infrared analyzers (NDIR) equipped with solid state detectors such as thermopiles or semiconductors.
A fluid analysis device that employs the following is used.

By the way, when performing the above-mentioned fluid analysis, it is necessary to analyze various substances in the sample fluid, such as NO and NO ₂ , methane (CH ₄ ) and HC other than methane (NMHC), or CO and CO ₂ . It is often necessary to measure the concentration of two components simultaneously and continuously, but in order to achieve this with conventional fluid analyzers, two detectors (sensors) are required. It was hot.

In other words, when simultaneously and continuously measuring NO and NO ₂ , the sample fluid is divided into two measurement systems, and one system is equipped with a first NO detector to independently measure the NO concentration in the sample gas. and the other system is equipped with a second NO detector to measure the total NO concentration in the processing fluid generated by converting NO ₂ in the sample gas to NO. (The NO ₂ concentration is obtained as the difference between the total NO concentration detected by the second NO detector and the NO single concentration detected by the first NO detector, and this method is called the difference method.) In addition, when simultaneously and continuously measuring methane and HC other than methane (NMHC), the sample fluid is divided into two measurement systems, and one system measures the total HC concentration (THC) of the sample fluid. A first HC detector is provided for
The other system contains HCs other than methane in the sample fluid.
The first method is to measure the concentration of methane in the treated gas produced by catalytic combustion and removal of methane.
Two HC detectors are required (in this case, the differential method is also used, and NMHC is based on the THC concentration detected by the first HC detector and the methane concentration detected by the second HC detector). (obtained as the difference from the detected value), and also the CO in the sample fluid
When simultaneously and continuously measuring CO 2 and CO ₂ , the sample fluid is divided into two measurement systems, and one system is
Two different detectors, a CO detector and a CO ₂ detector, are required: one system has a CO detector and the other system has a CO ₂ detector.

By dividing the same sample fluid into two systems as described above, it is possible to analyze not only the simultaneous and continuous analysis of two components in the sample fluid but also the components contained in each of the two different sample fluids. It is clear that two detectors (sensors) are similarly required when simultaneously and continuously analyzing a specific component.

However, as mentioned above, simultaneous and sequential analysis of two components in the same sample fluid, or
When performing simultaneous and continuous analysis of specific components contained in two different sample fluids,
The need to use two detectors as in the conventional device has the following problems: (a) The analyzer becomes larger and the manufacturing cost increases, as well as (b) Since adjustments such as zero and span adjustments are required, measurement requires a lot of effort and is very troublesome. (c) Each detector is not adjusted sufficiently, and there may be zero adjustment errors or sensitivity between the two detectors. If there is a difference, a very large measurement error will occur, leading to various problems.

Therefore, in order to avoid such problems, two components in the same sample fluid can be measured alternately using an analyzer equipped with only one detector, or alternatively, two components in the same sample fluid can be measured alternately. It is also possible to use a so-called batch-processing analysis method, in which measurements are taken in batches, but in that case, there is a disadvantage that the measurement data becomes discontinuous because simultaneous and continuous measurements cannot be performed. When performing analysis using the differential method, there is a risk that measurement accuracy will be significantly degraded. Therefore, adopting such a batch analysis method simply to save on the number of detectors may greatly sacrifice the original purpose of fluid analysis, and may not be a good idea. do not have.

In view of the above-mentioned conventional situation, the present inventors conducted intensive research and developed a completely new fluid analysis method and fluid analysis device that uses a revolutionary technique called the multi-fluid modulation method, which makes it possible to simultaneously and continuously analyze multiple sample fluids (or sample fluids that have been split into multiple systems) using only one detector. The basic concept of this method and device was first described in 1987.
Patent application dated December 11, 1987 and December 12, 1987
This has already been proposed through prior applications such as patent applications filed on .

That is, the fluid analysis device using the multi-fluid modulation method (the method is applied in this device) is shown in the basic conceptual diagram shown in Fig. 6 and the specific configuration diagram of the main parts shown in Fig. 5. As is clear from the above, multiple (two in this example) sample fluids S1,
S2 (which may be originally different or may be a single sample fluid divided into two systems) is fluid-modulated at different frequencies F1 and F2 (Hertz) by comparison fluids R1 and R2, respectively. an analysis section A having only one detector D and to which the fluid-modulated sample fluids S1 and S2 are simultaneously and continuously supplied; The output signal O from the detector D at A is suitably frequency separated and signal rectified.
Using a smoothing means (shown conceptually in FIG. 6), each sample fluid S1, S2 is
The signal components O of each modulation frequency F1, F2 for
a signal processing means B for obtaining analysis values regarding each of the sample fluids S1 and S2 by rectifying and smoothing the sample fluids S1 and S2; , 7th
As specifically shown in the figure, from the output signal O from the detector D, there are two bandpass filters a1 and a that respectively pass only signals in bands around the respective modulation frequencies F1 and F2.
2 are provided in parallel with each other, and in synchronization with the actual fluid modulation operation by the fluid modulation means V1, V2 corresponding to the passband frequencies F1, F2, a Pass filter a1,a
Synchronous detection rectifiers b1 and b2 are provided for detecting and rectifying the output signals from the synchronous detection rectifiers b1 and b2, and a smoothing element c is provided at the subsequent stage of each of the synchronous detection rectifiers b1 and b2 for smoothing the output signals therefrom.
1 and c2 are provided.

In other words, in a fluid analysis device using a multi-fluid modulation method having such a configuration, an appropriate fluid modulation means V1 consisting of, for example, a rotary valve, a two-way switching solenoid valve, a four-way switching solenoid valve, etc.
V2 is used to analyze two sample fluids S1, S2 (or separated flows of the two systems) sample fluids S1, S2 modulated by reference fluids R1, R2 at mutually different frequencies F1, F2, respectively, with only one detector D. By simultaneously and continuously supplying the sample fluids to section A, first, the individual measurement signal components (O1, O2) corresponding to all sample fluids S1, S2 are superimposed all at once from that single detector D. In addition to adopting a unique method that was completely unthinkable in the conventional common sense of obtaining a single measurement signal O (=O1 + O2),
For example, as illustrated in FIG. 6, the output signal O from the
By using the signal processing means B configured in combination with the smoothing means, each of the sample fluids S
Analytical values for each of the sample fluids S1 and S2 are obtained by performing signal processing of separating signal components O1 and O2 of each modulation frequency F1 and F2 for each of the sample fluids S1 and S2, and rectifying and smoothing the signal components, respectively. Therefore, even when performing simultaneous and continuous analysis of two components in the same sample fluid, or simultaneous and continuous analysis of specific components contained in two different sample fluids, only one detector ( Therefore, compared to conventional fluid analysis devices that required two detectors, the entire device can be made smaller and simpler, and costs can be reduced. The basic advantage is that it can be adjusted easily and quickly, and that zero adjustment errors and sensitivity differences between multiple detectors cannot occur as in conventional methods, ensuring good measurement accuracy at all times. have.

Moreover, as the signal processing means B, a computer capable of performing numerical analysis processing such as Fourier analysis (corresponding to frequency separation processing) and absolute value averaging processing (corresponding to rectification/smoothing processing) is used. Alternatively, it is possible to configure appropriate means using various software or hardware, such as using an electric circuit such as a lock-in amplifier. As shown, bandpass filters a1 and a2 and synchronous detection rectifier b
1 and b2, and smoothing elements c1 and c2, which are made up of low-pass filters and capacitors, are connected in series, and two signal processing lines are installed in parallel, so the computer or lock-in amplifier described above is Not only can it be constructed very simply and inexpensively compared to the means used, but also the frequency separation effect, which may not be sufficient with bandpass filters a1 and a2 alone, can be supplemented by synchronous detection rectifiers b1 and b2. Because it is configured to perform more accurate frequency separation, it provides much better signal processing than, for example, a configuration that simply performs frequency separation using a bandpass filter and then immediately performs absolute value rectification. There is also the advantage that performance (S/N ratio) can be obtained.

However, even in the fluid analyzer using the multi-fluid modulation method, which has various useful advantages as described above, the following problems still remain.

That is, as explained using FIG. 7, in the signal processing means B, the measurement signal O inputted from the detector D via the preamplifier 2 is first filtered by bandpass filters a1 and a2. ,
Individual measurement signal components O1 (frequency F1), O2 (frequency F2) corresponding to both sample fluids S1, S2
However, either the fluid modulation frequencies F1 and F2 are set to be sufficiently different, or the two bandpass filters a1 and F2 are set to be sufficiently different.
Unless measures are taken that are extremely difficult in practice, such as using a high-grade material with fairly sharp frequency cut characteristics as a2, reliable frequency separation results cannot be obtained. The signals that have passed through the bandpass filters a1 and a2 include, in addition to the signal O1 with the original frequencies F1 and F2, the other fluid modulation frequency F2 and F1.
This results in a mutual interference effect in which noise components are mixed in.

In this way, each bandpass filter a1, a
If noise components of the other fluid modulation frequencies F2 and F1 due to mutual interference are mixed into the signal that has passed through the two fluid modulation frequencies F2 and F1, the following problems will occur.

In other words, both fluid modulation frequencies F1 and F2 are:
Normally, it can be set arbitrarily, but in that case, generally the signal is
1 and b2, the signal corresponding to the interference noise component remains as a measurement error factor (that is, its average value does not become 0).

This means, for example, that one fluid modulation frequency F
This will be easily understood from FIG. 8A and FIG. 8B, which show an example where F1 is 1Hz and the other fluid modulation frequency F2 is 3Hz.

Furthermore, as is clear from Figure 8A, the measurement error factors due to the mutual interference effects mentioned above are particularly
It appears very large in a system where the measurement signal is a lower frequency signal, but it does not appear so large in a system where the measurement signal is a higher frequency signal, as is clear from Figure 8 (b). It has been experimentally found that there is a tendency for there to be a tendency for interference from the system using the higher frequency signal as the measurement signal to the system using the lower frequency signal as the measurement signal. It can also be verified theoretically from the graphs in Figures A and B.

Further, the above-mentioned problem is not limited to noise components due to mutual interference effects, but also to frequencies F2 and F1 of other systems caused by other factors such as deviations in mechanical duty of the fluid modulation means V1 and V2. A similar problem occurs when a noise component is mixed in.

Therefore, in order to reduce as much as possible the above-mentioned "measurement error caused by interference noise components of the other frequency signal in a system where one frequency signal is the measurement signal", we have further developed As a result of continued research, we have developed the following technology, which we have already proposed in a patent application filed on December 24, 1988.

As shown in FIG. 9, in a fluid analysis device using a multi-fluid modulation method having the basic configuration as described above, both the fluid modulation means V1 and V
2 are set so that the ratio of the fluid modulation frequencies F1 and F2 is an even number or a fraction of an even number (F1=Hz, F2=2hHz or vice versa, where h is an integer).

That is, by adopting such a configuration, for example, the two fluid modulation frequencies V1 and V2 can be set to be sufficiently large different, or the two bandpass filters a1 and a2 in the signal processing means B can be set to be sufficiently different.
In a system where one frequency signal is used as a measurement signal, it is possible to eliminate the interference noise component caused by the other frequency signal in a system where one frequency signal is used as the measurement signal, without using practically difficult means such as using a high-grade product with sharp frequency cut characteristics. Measurement errors and the like caused by this can be easily reduced.

In other words, for example, when one (lower) fluid modulation frequency F1 is 1 Hz and the other (higher) fluid modulation frequency F2 is an even multiple (twice) of that, 2 Hz, as shown in Figure 10A. In addition to the original signal O1 (1Hz), there is interference noise due to the higher fluid modulation frequency (2Hz) in the signal that has passed through bandpass filter a1 in a system where the lower frequency signal (1Hz) is the measurement signal. Even if the noise component (2
Hz) is then synchronously detected and rectified in such a way that the smoothed value by the smoothing element c1 is plus/minus canceled and becomes 0. Therefore, only the original signal O1 (1 Hz) is output from the smoothing element c1. A correct measurement signal corresponding to . Also, contrary to the above, the higher frequency signal (2Hz)
In a system where the measurement signal is , the interference noise component due to the lower frequency signal (1Hz) similarly cancels out the average value plus/minus and becomes 0.
It will be easily understood from FIG. 10(b) that a correct measurement signal without any measurement error can be obtained.

In addition, although FIG. 10 A and B above illustrate the case where the original signal and the interference noise component, which have different frequencies, are in the same phase,
As shown in FIGS. 11A and 11B, even if there is a phase shift θ between them, the interference noise component similarly becomes 0 as its smoothed value is canceled out by plus/minus.

[Problem that the invention attempts to solve]

However, as described above, the bandpass Due to factors such as poor cut-off characteristics of filters a1 and a2 or deviation in mechanical duty of fluid modulation means V1 and V2, "the other frequency (F2) in a system where one frequency signal F1 is the measurement signal" Although the objective of "reducing measurement errors caused by interference noise components" was achieved, it was found that the following problems still remain.

That is, the above bandpass filter a
Measurement error factors such as imperfection in the cutoff characteristics of V1 and a2 and deviations in the mechanical duty of fluid modulation means V1 and V2 are of a nature that constantly occur. V1, V2
are set so that the ratio of the fluid modulation frequencies F1 and F2 by them is an even number or a fraction of an even number.
By using this method, it is possible to make the average value almost 0 within a normal (sufficiently long) measurement time, but as shown in Figure 12, for example, the zero span before measurement During adjustment, etc., in order to perform initial adjustment of one measurement system (in this example, the side where the fluid modulation frequency is 1Hz), a state in which a span fluid is flowed from a state in which zero fluid was being flowed as sample fluid S1 to that measurement system. When the concentration of the sample fluid S1 suddenly changes suddenly (for example, in a step manner), such as when switching to the other measurement system (fluid modulation frequency side of 2 Hz)
The so-called whisker noise x, x corresponding to the sudden change in the concentration of the sample fluid S1 occurs in the output signal from the sample fluid S1 as a transient response interference effect. According to the simulation results, this whisker noise x,
It has been found that measurement errors due to the occurrence of x can reach several percent. Although not shown in the diagram, this phenomenon similarly appears in the output signal from one measurement system (1Hz side) even when initial adjustment is performed on the other measurement system (2Hz side). Needless to say, this problem can occur not only during zero/span adjustment as illustrated here, but also during measurement.

The reason why whisker noise x, x occurs due to the transient response interference effect as described above is that this type of rapid concentration change has the property of occurring instantaneously at arbitrary timing (phase). Therefore, the measurement error caused by the whisker noise x, x due to the influence of transient response interference cannot be canceled in a time-integral manner like the measurement error factors that occur constantly as described above.

The present invention was devised in view of the above circumstances, and its purpose is to make a very simple structural improvement, and the purpose of this invention is to improve the performance of the sample fluid when the concentration of the sample fluid introduced into one of the measurement systems suddenly changes as described above. The object of the present invention is to reduce measurement errors caused by whisker noise due to transient response interference effects on the other measurement system as much as possible.

[Means for solving problems]

In order to achieve the above object, the present invention provides a fluid analysis device using a multi-fluid modulation method, which has the improved basic configuration as described above, as shown in the overall schematic diagram of the configuration in FIG. 1 (diagram corresponding to the claims). , namely: fluid modulation means V1, V2 for modulating the two sample fluids S1, S2 (also divided into two systems) at different frequencies F1, F2 by comparison fluids R1, R2, respectively; an analysis section A having only one detector D and to which each of the fluid-modulated sample fluids S1 and S2 is supplied simultaneously and continuously; and an output signal O from the detector D in the analysis section A. , signal components O1, O2 of each modulation frequency F1, F2 for each sample fluid S1, S2.
In order to obtain analysis values regarding the respective sample fluids S1 and S2 by separating them into rectifying and smoothing processing, the bands around the respective modulation frequencies F1 and F2 are extracted from the output signal O from the detector D. Two band pass filters a1 and a2 are provided in parallel with each other to pass only the signals of , respectively, and fluid modulation means V1 and V1 corresponding to the pass band frequencies F1 and F2 are provided downstream of each of the band pass filters a1 and a2, respectively. In synchronization with the actual fluid modulation operation by V2, the bandpass filter a1,
Synchronous detection rectifiers b1 and b2 are provided to detect and rectify the output signal from a2, and smoothing elements c1 and c2 are provided downstream of each of the synchronous detection rectifiers b1 and b2 to smooth the output signal therefrom. and a signal analysis means B consisting of a signal analysis means B, and a multi-fluid modulation device in which both the fluid modulation means V1 and V2 are set such that the ratio of their fluid modulation frequencies F1 and F2 is an even number or a fraction of an even number. In the fluid analysis device according to this method, in the middle of the supply channel of each of the sample fluids S1 and S2 to each of the fluid modulation means V1 and V2, respectively,
It is characterized in that buffer tanks C1 and C2 are interposed to alleviate the transient response interference effect on the measurement system of the other sample fluid S2 and S1 when the concentration of the sample fluid S1 and S2 suddenly changes.

[Effect]

The effects achieved by employing the above characteristic means are as follows.

That is, according to the fluid analyzer using the multi-fluid modulation method of the present invention, the improved prior art fluid analyzer using the multi-fluid modulation method configured by the combination of Figs. 9 and 7 described above is used, so that not only can the basic effect of reducing as much as possible "measurement errors caused by constant interference noise components of one frequency signal F1, F2 in a system in which the other frequency signal F1, F2 is used as a measurement signal" is exhibited, but also the sample fluid S to both fluid modulation means V1, V2 is not easily transmitted.
In the supply flow paths of the sample fluids S1 and S2, buffer tanks C1 and C2 are provided to reduce the influence of transient response interference on the measurement system of the other sample fluid S2 and S1 when the concentration of the other sample fluid S1 and S2 suddenly changes. As shown in FIG. 2, even if the concentration of the sample fluid S1 and S2 introduced into one measurement system suddenly changes (changes in a step-like manner), the sample fluids S1 and S2 are supplied to the fluid modulation means V1 and V2 after the sudden change in concentration is reduced in the buffer tanks C1 and C2. Therefore, in the buffer tanks C1 and C2,
By setting the capacitance of the first measurement system to an appropriate value, the concentration measurement in one of the measurement systems can be performed without any problems, and the influence of transient response interference on the other measurement system, i.e., the generation of whisker noise x, x can be reduced as much as possible.

[Embodiment] Hereinafter, a specific embodiment of a fluid analysis device using a multi-fluid modulation method according to the present invention will be described with reference to the drawings (FIGS. 3 to 5).

FIG. 3 shows the difference method and multi-fluid modulation method constructed as a specific embodiment of the present invention.
A fluid analysis device for simultaneous and continuous measurement of HC3 components is shown. This is used, for example, when analyzing the concentration of non-methane HC (second component), which is a particularly harmful component among the HC components contained in a sample fluid S such as the atmosphere, automobile exhaust, or factory exhaust. To this end, directly measure the individual concentration of methane (CH ₄ ), which is the first component, and the concentration of the third component (total HC concentration), which is defined as the sum of both the first and second components, The configuration is such that the individual concentration of nonmethane HC, which is the second component, is indirectly measured from the difference between the two concentration measurement results.

That is, the sample fluid S is changed to the first sample fluid S
The first sample fluid S1 and the second sample fluid S2 are configured to separate into two flow paths, and the flow path of the first sample fluid S1 is connected to the other second sample fluid when the concentration of the first sample fluid S1 suddenly changes. It has both a buffer function to alleviate the effects of transient response interference on the measurement system, and a converter function to burn and remove non-methane HC, which is the second component of the first sample fluid S1. By installing a buffer tank C1 consisting of a catalyst device etc., the line is used to measure the individual concentration of methane (CH ₄ ), which is the first component. By interposing the buffer tank C2 which only functions as a buffer to alleviate the transient response interference effect on the measurement system of the other first sample fluid S1 when the concentration of the second sample fluid S2 suddenly changes, the third component Concentration (total HC
It is configured to be a line for measuring concentration).

The first sample fluid S is converted (that is, non-methane HC is removed and contains only methane as HC) by the buffer tank C1 having a function as a converter.
1, and a second sample fluid S2 that is not converted.
Both sample fluids S1 and S2 (that is, the same as the original sample fluid S containing both non-methane HC and methane) are measured using fluid modulation means V1 and V2, respectively, to compare fluids R1 and R2 (generally (zero gas is used), different frequencies F1 and F2 (Hertz) (in this example, F
1 = 1 Hz, F2 = 2 Hz) (that is, the sample fluid and the comparison fluid are passed alternately at a predetermined frequency), and then each fluid-modulated sample fluid S1, S2, R1, R2 is , only one
Analysis section A with HC detectors D (sensors)
The structure is such that it can be supplied simultaneously and continuously. In this case, as the HC detector D in the analysis section A, a type through which the sample fluid passes directly, such as a flame ion detector (FID), is generally used. Both sample fluids S1, S2, R1, R
2 is supplied to the HC detector D in a mixed state.

Therefore, the signal O output from the HC detector D via the preamplifier 2 is composed of individual measurement signal components (O1, O2) corresponding to both sample fluids S1, S2, as schematically shown in the figure. ) are collectively superimposed on one measurement signal (O=O1+O2)
It will be obtained as follows.

Therefore, the output signal O from the HC detector D
As conceptually illustrated in this FIG. Signal components O1, of each modulation frequency F1, F2 for S1, S2,
By performing signal processing of separating into O2 and rectifying and smoothing each sample fluid, the analytical values for each sample fluid S1 and S2, that is, the independent concentration of the first component (methane) and the third component, are obtained.
It is configured so that the measurement results of the concentration of each component (total HC concentration) can be obtained separately and directly, and the individual concentration of the second component (non-methane HC) can be indirectly obtained from the difference between the two concentration measurement results. Constructed to be measurable.

The specific circuit configuration of the signal processing means B is as shown in the block circuit diagram of FIG.

That is, the HC detector D via the preamplifier 2
The signal O outputted from the is branched into two signal processing trains arranged in parallel with each other, and one signal processing train separates only the signal O1 of the modulation frequency F1 (1 Hz) for the first sample fluid S1. A band pass filter a1 is provided for extracting (passing) the first sample fluid S1. Signals representing actual fluid modulation behavior:
1 Hz), it is possible to supplement the frequency separation effect that may be insufficient with the band pass filter a1 alone and achieve even more accurate frequency separation, and at the same time, to be able to convert the separated alternating current into direct current. a synchronous detection rectifier b for synchronously rectifying the output signal O1 from the bandpass filter a1;
1, and a low-pass filter (LPF) as a smoothing element c1 for smoothing the output signal from the synchronous detection rectifier b1 and removing high frequency noise is provided at the subsequent stage, and the other signal processing The series is provided with a bandpass filter a2 for separating and extracting (passing) only the signal O2 of modulation frequency F2 (2 Hz) for the second sample fluid S2, and at the subsequent stage, a band pass filter a2 for separating and extracting (passing) only the signal O2 of the modulation frequency F2 (2 Hz) for the second sample fluid S2. Due to the synchronization signal (signal representing the actual fluid modulation operation by the fluid modulation means V2: 2 Hz) from the synchronization signal generator 1b attached to the modulation means V2, there is a possibility that the bandpass filter a2 alone is insufficient. The bandpass filter a2 is used to supplement the frequency separation effect and perform more accurate frequency separation, and at the same time convert the separated alternating current into direct current.
A synchronous detection rectifier b2 for synchronously rectifying the output signal O2 from the synchronous detection rectifier b2 is provided, and a smoothing element c2 for smoothing the output signal from the synchronous detection rectifier b2 and removing high frequency noise is provided at the subsequent stage.
A low pass filter (LPF) is installed as a
Further, the output signal from the smoothing element c1 in the signal processing system regarding the first sample fluid S1 is set as a negative input, and the output signal from the smoothing element c2 in the signal processing system regarding the second sample fluid S2 is set as a positive input. A subtracter g serving as a subtracting means G is provided. Therefore, the smoothing element c1 outputs the measurement result of the single concentration of methane, which is the first component, and the smoothing element c2 outputs the measurement result of the single concentration of methane, which is the first component.
The measurement result of the component concentration (total HC concentration) is output, and the measurement result of the single concentration of nonmethane HC, which is the second component, is output from the subtracter g.

Note that the signal processing means B is a computer capable of performing numerical analysis processing such as Fourier analysis (corresponding to frequency separation processing), absolute value averaging processing (corresponding to rectification/smoothing processing), and subtraction processing. It is possible to configure it by appropriate means using various software or hardware, such as using a lock-in amplifier and a subtracter, or using other electric circuit configurations such as a lock-in amplifier and a subtracter.
In particular, the device of the present invention has a configuration in which two signal processing series are provided in parallel, each consisting of bandpass filters a1, a2, synchronous detection rectifiers b1, b2, and smoothing elements c1, c2 connected in series, as described above. Therefore, compared to the methods using computers or lock-in amplifiers as mentioned above,
Not only is it extremely simple and inexpensive to configure,
The synchronous detection rectifiers b1 and b2 supplement the frequency separation effect, which may not be sufficient with the bandpass filters a1 and a2 alone, so that even more accurate frequency separation can be achieved. Compared to a configuration in which absolute value rectification is performed immediately after frequency separation using only a bandpass filter, this method has the advantage that significantly superior signal processing performance (S/N ratio) can be obtained.

By the way, each of the fluid modulation means V1 and V2 is
The structure may be arbitrary as long as it can alternately switch the sample fluids S1, S2 and the comparison fluids R1, R2 at a predetermined frequency. For example, it may be configured with a rotary valve as shown in FIG. 5A. Alternatively, it may be constructed using a four-way switching solenoid valve as shown in FIG.

Note that the present invention is not limited to the above-mentioned embodiments, and is applicable to, for example, NOx (NO, NO ₂ , total NO)
It goes without saying that the present invention can also be applied to measurements of other types of three components such as COx (CO, CO ₂ , total CO).

[Effect of idea]

As is clear from the detailed description above, the fluid analysis device using the multi-fluid modulation method according to the present invention basically performs fluid analysis using the multi-fluid modulation method according to the improved prior art described above. In the apparatus, a buffer tank is provided in the middle of the flow path for supplying each sample fluid to each fluid modulation means, for mitigating the influence of transient response interference on the measurement system of the other sample fluid when the concentration of the sample fluid suddenly changes. Although it is a very simple structural improvement such as interposing a In addition to achieving the basic effect of reducing `` to the extent possible, ``transient response interference effects on the other measurement system when the concentration of the sample fluid introduced into one measurement system changes suddenly ( "Measurement error caused by whisker noise"
This has an excellent effect in that it can also significantly reduce

[Brief explanation of the drawing]

1 and 2 are for explaining the basic concept of the fluid analysis device using the multi-fluid modulation method according to the present invention, and FIG. 1 shows the overall schematic configuration diagram (diagram corresponding to claims). , FIG. 2 shows an explanatory diagram of its operation. FIGS. 3 to 5 show the difference method and multi-fluid modulation method configured as a specific embodiment of the present invention.
Showing a fluid analyzer for simultaneous and continuous measurement of three HC components,
FIG. 3 is a schematic diagram of the overall configuration, FIG. 4 is a block circuit diagram of the signal processing means, and FIGS. 5A and 5B are schematic diagrams of examples of the fluid modulation means.
Further, FIGS. 6 to 12 are for explaining the technical background of the present invention and problems in the prior art, and FIGS. 6 and 7 illustrate the multi-fluid modulation method according to the prior art. The overall schematic configuration diagram of the fluid analysis device and the block circuit configuration diagram of its signal processing means are shown; FIGS. 8A and 8B illustrate the problems, and FIG. The overall schematic configuration diagram of a fluid analysis device using an improved multi-fluid modulation method is shown, and FIGS. An explanatory diagram of the problem is shown. S1, S2... Sample fluid, R1, R2...
Comparison fluid, F1, F2...Fluid modulation frequency, V
1, V2...Fluid modulation means (rotary valve),
C1, C2...Battle tank, A...Analysis department,
D...detector, B...signal processing means, O...output signal from detector D, O1, O2...each modulation frequency F1, F2 for each sample fluid S1, S2
signal components, a1, a2... band pass filter, b1, b2... synchronous detection rectifier, c1, c2
...Low pass filter.

Claims (1)

[Claims for Utility Model Registration] Fluid modulation means for modulating two sample fluids (also divided into two systems) at mutually different frequencies with reference fluids, and a single detector. an analysis section to which each of the fluid-modulated sample fluids is simultaneously and continuously supplied; and an analysis section that separates the output signal from the detector in the analysis section into signal components of each modulation frequency for each of the sample fluids. In order to obtain an analysis value for each sample fluid by rectifying and smoothing the fluid, two bandpasses each pass only a signal in a band near each modulation frequency from the output signal from the detector. Filters are provided in parallel with each other, and the output signal from the bandpass filter is detected and rectified in synchronization with the actual fluid modulation operation by the fluid modulation means corresponding to the passband frequency at the downstream stage of each of the bandpass filters. a synchronous detection rectifier for smoothing the output signal from the synchronous detection rectifier; , in a fluid analysis device using a multi-fluid modulation method, in which the ratio of fluid modulation frequencies is set to be an even number or a fraction of an even number. Fluid analysis using a multi-fluid modulation method, characterized in that each of the sample fluids is provided with a buffer tank for mitigating the transient response interference effect on the measurement system of the other sample fluid when the concentration of the other sample fluid suddenly changes. Device.