JP3174623B2 - Gas analyzer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas analyzer for measuring the concentration of a specific component in a sample gas.

[0002]

2. Description of the Related Art For example, a cell into which a sample gas is introduced is irradiated with ultraviolet light from a light source, ultraviolet light transmitted through the cell is detected by a detector, and SO ₂ is absorbed based on the amount of ultraviolet light absorbed at that time. Can be measured. by the way,
When measuring the SO ₂ concentration in this manner, the conventional ultraviolet absorption SO ₂ analyzer was configured as shown in FIG. 4 because CO ₂ becomes an interference component.

That is, in FIG. 4, reference numerals 40 and 50 denote SO ₂ and CO ₂ meters to which a sample gas from the same sample gas source is branched and supplied. And SO ₂ total 40,
Analysis unit 41, detector 42, preamplifier 43, low-pass filter
44, a synchronous detection rectifier circuit 45 and a smoothing circuit 46. Also,
The CO ₂ meter 50 includes an analyzer 51, a detector 52, a preamplifier 53, a low-pass filter 54, a synchronous detection rectifier circuit 55, and a smoothing circuit 56. Reference numeral 61 denotes a synchronous signal generator that outputs a synchronous signal to the synchronous detection and rectification circuits 45 and 55, and 62 denotes a subtractor that subtracts the output of the CO ₂ meter from the output of the SO ₂ meter 40. According to the ultraviolet absorption SO ₂ analyzer configured as above, the CO ₂
Interference effects can get the SO ₂ concentration was removed.

[0004]

However, the ultraviolet absorption SO ₂ analyzer having the above configuration has the following disadvantages. That is, since the SO ₂ meter 40 and the CO ₂ meter 50 cannot measure the same sample gas at exactly the same time, if a time difference occurs between the SO ₂ meter 40 and the CO ₂ meter 50, an error occurs in the measurement result. Will happen. Further, since an extra CO ₂ meter 50 having the same configuration as that of the SO ₂ meter 40 is required, the cost increases, the number of parts increases, and the measurement accuracy between the SO ₂ meter 40 and the CO ₂ meter 50 increases. UV absorption SO ₂
It is difficult to maintain the reliability of the analyzer.

As described above, when measuring the concentration of SO ₂ , CO ₂ becomes an interference component.
As shown in FIG. 7, a phase at which a signal (measurement component signal) a corresponding to SO ₂ (shown by a solid line) is generated, and a signal (interference component signal) b corresponding to CO ₂ (shown at a virtual line) are generated. The phase is different. The present invention has been made in consideration of such a matter, and an object of the present invention is to process an output signal from a single analysis unit without providing a plurality of analysis units. It is an object of the present invention to obtain a gas analyzer capable of eliminating the influence of interference of the gas and accurately measuring the concentration of the component to be measured.

[0006]

In order to achieve the above-mentioned object, a gas analyzer according to the present invention provides a gas analyzer in which a signal corresponding to a component to be measured from a detector and a signal corresponding to an interference component are superimposed. The output signal is supplied to two signal processing lines, and one of the signal processing lines performs synchronous phase detection and rectification so as to correspond to the phase at which the component signal to be measured is generated. Synchronous phase detection and rectification are performed so as to correspond to the phase at which the signal is generated, and the interference component signal that has entered the one component signal to be measured is canceled by the interference component signal obtained by the other signal processing line. .

[0007]

For example, when measuring the concentration of SO ₂ , CO ₂ becomes an interference component, but a signal corresponding to SO ₂ , that is,
Since the phase at which the component signal to be measured is generated is different from the signal corresponding to CO ₂ , that is, the phase at which the interference component signal is generated, the output signal of the detector is supplied to two signal processing lines. In the signal processing line, synchronous phase detection and rectification are performed so as to correspond to the phase in which the component signal to be measured is generated. In the other signal processing line,
Synchronous phase detection and rectification corresponding to the phase at which the interference component signal is generated, and the interference component signal entering one of the component signals to be measured is canceled by the interference component signal obtained by the other signal processing line. , It is possible to obtain only the measurement target component signal from which the interference component signal is removed.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 shows an example of the configuration of an analyzer in an SO ₂ analyzer as an example of the gas analyzer according to the present invention. In this figure, reference numeral 1 denotes an ultraviolet light source composed of, for example, a low-pressure mercury lamp. Reference numeral 2 denotes a cell to which the sample gas S and the reference gas R are alternately supplied at a constant cycle. The cell 2 is provided with a gas inlet 3 and a gas outlet 4, and although not shown in detail, an end facing the light source 1 and The end facing the ultraviolet detector 5 described later is sealed by a cell window that transmits ultraviolet light. Reference numeral 5 denotes an ultraviolet detector (hereinafter, referred to as a detector) including a photoelectric tube, a photodiode, or a photomultiplier tube, and reference numeral 6 denotes a preamplifier.

[0009] Then, reference numeral 7 denotes a sample gas S for the cell 2.
And a reference gas R for alternately switching and supplying the gas at a constant cycle. In this embodiment, the gas switching supply device comprises a rotary valve. That is, the valve body 8 is provided with two gas inlets 9 and 10 and two gas outlets 11 and 12 so as to divide the periphery into four equal parts, and the inside thereof is driven by a motor (not shown) in the direction of the arrow. Is provided with a rotor 13 which also serves as a partition that is driven to rotate. The one gas inlet 9 is connected to a sample gas source (not shown) via an appropriate pipe, and the other gas inlet 10 is
It is connected to a reference gas source (not shown) via an appropriate pipe. Further, one gas outlet 11 is connected to the gas inlet 3 of the cell 2, and the other gas outlet 12 is connected to an exhaust passage (not shown) together with the gas outlet 4 of the cell 2.

In the SO ₂ analyzer configured as described above, the sample gas S and the reference gas R are supplied to the cell 2 via the gas switching supply unit 7 while irradiating the cell 2 with ultraviolet rays from the ultraviolet light source 1. Are alternately supplied at regular intervals, so-called fluid modulation is performed, and the detector 5 outputs an AC signal. in this case,
In addition to SO ₂ which is a component to be measured in the sample gas S,
When CO ₂ which is an interference component is mixed, the detector 5 outputs a signal (hereinafter, referred to as an SO ₂ signal) a corresponding to SO ₂ from the detector 5 as shown in FIG. A signal s ₀ on which a signal b corresponding to ₂ (hereinafter referred to as a CO ₂ signal) b is superimposed is output.

In the present invention, a signal processing section as shown in FIG. 1 is provided on the output side of the preamplifier 6 in order to separate and remove the CO ₂ signal b from the SO ₂ signal a. That is, in this figure, reference numeral 14 denotes a band-pass filter for removing noise included in the output from the detector 5.
On the output side of the band-pass filter 14, two signal processing lines 15, 16 are provided in parallel with each other. Any two signal processing lines 15 and 16 consists of synchronous detection rectifier circuit 17, 18 a smoothing circuit 19, 20., wherein the SO ₂
A signal s _{0 in} which a CO ₂ signal b is superimposed on a signal a is input. Reference numeral 21 denotes a synchronization signal generator, and reference numeral 22 denotes an adder for adding signals processed by the signal processing lines 15 and 16, respectively. Reference numeral 23 denotes a level adjuster for adjusting the level of the output signal of the signal processing line 16 to the level of the output signal of the signal processing line 15.

The synchronous detection rectifier circuits 17 and 18 synchronously detect the signal s ₀ by the synchronous signal t output from the synchronous signal generator 21 at the same timing, but the phases at the time of synchronous detection are different from each other. It is. That is, the synchronous detection and rectification circuit 17 performs synchronous phase detection and rectification so as to correspond to the phase at which the SO ₂ signal a is generated, and the synchronous detection and rectification circuit 18 performs so as to correspond to the phase at which the CO ₂ signal b is generated. First, synchronous phase detection and rectification are performed. The adjustment of the deviation of the processing phase in these two circuits 17, 18 is performed by a phase adjustment circuit (not shown) incorporated in these circuits 17, 18.

Next, a signal processing operation in the signal processing unit configured as described above will be described with reference to FIG. Now, when the signal s ₀ as shown in FIG. 3B is input from the preamplifier 6 to the band-pass filter 14, the band-pass filter 14 removes extra noise included in the signal s ₀ . This signal s after noise removal
₀ is input to the signal processing lines 15 and 16, respectively. The synchronous detection and rectification circuit 17 performs synchronous phase detection and rectification so as to correspond to the phase at which the SO ₂ signal a is generated, and outputs a signal as shown in FIG. Also,
The synchronous detection and rectification circuit 18 performs synchronous phase detection and rectification so as to correspond to the phase at which the CO ₂ signal b is generated, and outputs a signal as shown in FIG.

The signals output from the synchronous detection and rectification circuits 17 and 18 are respectively subjected to smoothing processing in smoothing circuits 19 and 20, and become signals as shown in FIGS. That is, the output signal of the signal processing line 15 includes the positive SO ₂ signal a and the negative CO ₂ signal b. On the other hand, the output signal of the signal processing line 16 includes the positive SO ₂
A negative SO ₂ signal a having an absolute value considerably smaller than the signal a and a positive CO ₂ signal b having an absolute value equal to the negative CO ₂ signal b are included.

Therefore, the output signal of the signal processing line 15 is:
By adding the output signal of the signal processing line 16 after the level adjustment and the output signal of the signal processing line 16 in the adder 22, the positive and negative CO
₂ signal b is canceled, as shown in FIG. (G), CO ₂
Only the SO ₂ signal a that does not include the signal b is output.

In the above embodiment, the phase of the signal s ₀ is adjusted by the synchronous detection rectifier circuits 17 and 18 so that the timing of inverting the signal s ₀ is different from each other.
The synchronous signal t having the same timing is input from the synchronous signal generator 21 to the synchronous detection and rectification circuits 17 and 18. However, exactly the same synchronous detection and rectification circuits 17 and 18 are used. Synchronous signals at different timings may be input to the circuits 17 and 18, respectively.

In the above embodiment, the detector 5
Although the signal from is processed in an analog manner, it may be digitally processed instead.

In the above-described embodiment, the sample gas S and the reference gas R are switched at a constant period in order to obtain a signal s ₀ that changes alternately from the detector 5, and these are alternately supplied to the cell 2. A so-called fluid modulation method is adopted, but instead, for example, an ultraviolet light source 1 and a cell 2 are used.
A so-called chopper modulation method in which a chopper is provided between the two may be adopted.

Further, in the above embodiment, the SO ₂
Although the case of compensating for the interference of CO ₂ when measuring the concentration, the present invention can be widely applied to the case where the signal corresponding to the component to be measured and the signal corresponding to the interference component are generated in different phases. Needless to say.

[0020]

As described above, according to the present invention,
By simply processing an output signal from a single analysis unit without providing a plurality of analysis units, it is possible to eliminate the influence of interference of the interference component and accurately measure the concentration of the measurement target component.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration example of a signal processing unit of a gas analyzer according to the present invention.

FIG. 2 is a diagram showing a configuration example of an analysis unit of the gas analyzer according to the present invention.

FIG. 3 is a waveform chart for explaining the operation of the present invention.

FIG. 4 is a block diagram showing a conventional gas analyzer.

[Explanation of symbols]

5: detector, 15, 16: signal processing line, s ₀ : output signal of the detector, a: component signal to be measured, b: interference component signal.

────────────────────────────────────────────────── ─── Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) G01N 21/00-21/01 G01N 21/17-21/61 JICST file (JOIS)

Claims (1)

(57) [Claims] An output signal from a detector in which a signal corresponding to a component to be measured and a signal corresponding to an interference component are superimposed is supplied to two signal processing lines. Synchronous phase detection and rectification to correspond to the phase at which the component signal to be measured occurs, and synchronous phase detection and rectification to correspond to the phase at which the interference component signal occurs in the other signal processing line. A gas analyzer characterized in that an interference component signal entered into a measurement target component signal is canceled by an interference component signal obtained by the other signal processing line.