JPH1144646A - Method and apparatus for removing spike noise of gas analyzer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and an apparatus for removing a spike noise for gas analyzers, which detect a signal containing a spike noises caused by electromagnetic waves, αwaves, etc., thereby reducing the effect of the spike noise. SOLUTION: A spike noise N2 is detected from a signal S2 outputted by the first-stage amplifier of the detector of a gas analyzer, and a pulse is generated for a given time Ta from the detection of this spike noise N2 . Furthermore, the above-mentioned signal S2 is delayed at least a time TD necessary for the spike noise detection, and a spike noise N3 is removed by blocking the transmission of this delayed signals S3 only for the output time duration of the above- mentioned pulse P6 .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a method and an apparatus for removing spike noise of a gas analyzer.

[0002]

2. Description of the Related Art Conventionally, a signal input from a photodiode P used as a detector of a gas analyzer of a chemiluminescence method is processed by a circuit as shown in FIG.
Used for gas analysis. In FIG. 5, 2 is a first-stage amplifier connected to the photodiode P, 10 is a rectifying amplifier for rectifying a signal amplified by the first-stage amplifier, 11 is an integrating buffer for integrating the rectified signal, and 12 is an integrating buffer. And a buffer for sampling and holding the rectified signal. The rectifying amplifier 10, buffers 12, 13 and the like form a synchronous rectifier circuit 4b.

FIG. 6 exemplifies waveforms at various parts in the circuit of FIG. That is, when the photodiode P is used for the detector, the input signal S _p is affected by disturbances such as electromagnetic waves and α waves.
Spike noise N _p is contained in. This spike noise N _p is the noise impulse, when it is amplified by the first-stage amplifier 2 (current-voltage conversion), spike noise N ₂ included in the signal S ₂ output is provided to the first stage amplifier 2 Feedback resistor Rf and capacitor Cf
Time T ₁ by the time constant (τ = Rf × Cf)
(Approximately 2.3τ), the width is slightly widened.

Since the signal S ₂ is an alternating signal which switches between positive and negative at a frequency of, for example, 1 Hz, it is necessary to rectify the signal S ₂ before integrating it. Sy is a synchronization signal which switches in synchronism with the signal S ₂ per second, S _W1 is a switch to be switched by the synchronizing signal Sy. Three resistors r combined as shown, the switch S _W1, amplifier 10 is a synchronous rectifier circuit positive and negative switches the synchronization signal Sy Thus amplification factor, the signal S ₂ by the synchronous rectifier circuit DC signal S ₁₀ Becomes

[0005] The rectified signal S ₁₀ is integrated by the integrating circuit composed of a resistor R and a capacitor C and the buffer 11 (smoothing circuit) becomes a signal S _11. Further, the signal S ₁₁ is a switch S _W2 operated by the sample / hold signal S / H, the capacitor C ₁ and Buffer 1
It is intermittently transmitted by 2 a signal S ₁₂ in.

In the case of the example shown in FIG.
Signal S from P_PIs gradually increasing, so
Then, a step-like signal S as shown by a virtual line₁₂’Is output
However, in practice, the spike noise
Z N_TenIs integrated together, the time constant (τ = R × C)
2.3 times as long as T_TwoSignal S₁₁, S₁₂Is the noise N _Two
Under the influence of, it will be slightly higher.

Therefore, a spike noise N _P is detected by a detection circuit (not shown), and a hold signal H that generates a pulse for a time T ₂ from the time of detection of the spike noise N _P is generated.
When this hold signal H is activated, since the integrating circuit already spike noise N ₁₀ is input, the hold signal the signal S ₁₂ which outputs a signal S ₁₁ of the previous state from which point The signal S _{C2 held} by the switch SW ₃ operated by H and the capacitor C ₂ was used for gas analysis. That is, the signal S ₁₂ after when detecting spike noise N _P synchronous rectification
A certain period of time until there is no influence of spike noise N _P T
I had ignored it for _two .

[0008]

However [0007] a predetermined time or more time constant of the smoothing circuit for calculating the integral of the signal S ₁₀ in the above methods are synchronous rectification (e.g., time constant × 2.3 times longer) it is necessary to ignore the signals S _12, there is a drawback that the dead time T ₂ of the signal becomes longer. In particular, when the magnitude of the signal input from the detector, as in the example described above is changing, if unable to enter between the long time T ₂ signal,
In some cases, gas analyzers could not perform accurate gas analysis.

The present invention has been made in view of such circumstances, and detects a signal containing spike noise due to an electromagnetic wave or an α wave as in a gas analyzer using a photodiode as a detector. It is an object of the present invention to provide a method and apparatus for removing spike noise of a gas analyzer which reduces the influence of spike noise.

[0010]

According to the present invention, means for solving the above-mentioned problems are constituted as follows. That is, the method for removing spike noise of the gas analyzer of the present invention comprises:
A spike noise is detected from a signal output by a first-stage amplifier connected to a detector of the gas analyzer, a pulse is generated for a predetermined time from the time of detection of the spike noise, and the signal is converted into at least a time necessary for detection of the spike noise. The transmission of the delayed signal is blocked only while the pulse is being output, thereby removing spike noise.

The spike noise eliminator of the gas analyzer according to the present invention further comprises a spike noise detector for inputting a signal output from a first-stage amplifier connected to a detector of the gas analyzer and detecting spike noise from the signal. A pulse generator for generating a pulse for a predetermined time when the spike noise detector detects spike noise, a signal delay unit for delaying the signal by at least a time necessary for detecting the spike noise, and generating the pulse. In a state where the signal is not transmitted, the signal after the delay is transmitted as it is, and in a state where a pulse is generated, a spike noise removing unit which does not transmit the signal is provided.

Therefore, according to the present invention, the spike noise is detected by using the signal before the delay, and the signal after the delay is removed only for a predetermined time during which the influence of the spike noise appears, so that the spike noise input from the detector is removed. Can be eliminated with a short ineffective time such as a fall time generated at the output of the first-stage amplifier. That is, since spike noise is removed before input to the smoothing circuit for integrating the signal from the detector, the influence of spike noise can be removed in a much shorter time regardless of the time constant of the smoothing circuit. . By doing so, in a gas analyzer using the output signal of a detector containing spike noise, even if the input signal from the detector changes, the effect on the gas analysis can be drastically suppressed. it can.

If the pulse generator is of a variable type that extends a predetermined time for generating a pulse in proportion to the magnitude of the peak value of the spike noise, a time affected by the input spike noise is calculated. Since the signal invalid time is set to the minimum necessary time, the influence of spike noise on gas analysis using the output signal of the detector containing spike noise can be suppressed as much as possible.

[0014]

FIG. 1 shows a first embodiment of the present invention. In this figure, reference numeral 1 denotes a spike noise eliminator.
Is a device that removes spike noise from a signal input through a. The spike noise elimination device 1 includes a signal delay unit 3 including a delay element, and a spike noise elimination unit 4 including a switch circuit 4a and a synchronous rectification circuit 4b.
, A spike noise detecting section 5 and a pulse generating section 6 which is, for example, a monostable multivibrator.

FIG. 2 is a waveform diagram showing a simulated signal waveform for explanation in which only spike noise is extracted from the signals of various parts in FIG. Hereinafter, the operation of each unit in FIG. 1 will be described with reference to the signal waveforms in FIG.

[0016] As shown in FIG. 2 includes a spike noise N _P under the influence of disturbances such as electromagnetic waves or α waves in the signal S _P output when the input from the photodiode P. The spike noise N _P is the impulse noise, but when it is amplified by the first-stage amplifier 2, a constant determined by the constant (tau = Rf × Cf) when definite by the feedback resistor Rf and a capacitor Cf provided in the first-stage amplifier 2 It decreases over the fall time T ₁ (eg, 2.3 times the time constant). Therefore, the signal S ₂ output from the first-stage amplifier ₂
To include noise N ₂ having a width of fall time T _1.

According to the present invention, the signal S ₂ is processed by being divided into two signal lines 7 and 8. Sand, in the first signal line 7, is delayed by time T _D required to detect the signal S ₂ of the spike noise N ₂ by the delay element 3. In the second signal line 8, the signal S
₂ is input to the spike noise detector 5 to detect spike noise N ₂ from the signal S ₂ before the delay.

When the spike noise detector 5 detects the spike noise N ₂ , it outputs an arbitrary signal to the pulse generator 6 connected to the spike noise N ₂ , and the pulse generator 6 receiving the signal outputs a predetermined time width _Ta . and outputs a pulse signal P ₆ with. At this time, pulse signal P ₆ to the pulse generating unit 6 generates has at least the fall time above T ₁ of width T _a,
Further, the generation of the pulse signal P ₆ is caused by the spike noise N _B
It delayed only applied to the detection of the time T _D '.

On the other hand, the signal S output from the delay unit 3
₃ is delayed by a time T _D by the delay unit 3, the delay time T _D is at least the time required to detect the spike noise N _B T _D 'above. Therefore, by switching the delayed signal S ₃ by the switch circuit 4 a operating at the B contact by the pulse signal P ₆ , only the signal S ₃ including the spike noise N ₃ is cut off, and only this portion is invalidated. It can be.

As described above, according to the present invention, the signal S _{3 obtained by} cutting out only the portion containing the spike noise N ₃ in advance.
Is a synchronous rectifier circuit 4b conventionally used (see also FIG. 5).
Is used for gas analysis by performing synchronous rectification and smoothing. Therefore, it is no appearing influence of spike noise N _P in the signal S ₄ that is output from the synchronous rectifier circuit 4b.

The time T _D ′ required for detecting the above-described spike noise N ₂ is extremely short, and is generally about several hundred nanoseconds. A time constant (τ) determined by the feedback resistor Rf and the capacitor Cf provided in the first-stage amplifier 2
= Rf × Cf) is the synchronous rectifier circuit 4 as shown in FIG.
The time is much smaller than the time constant (τ = RC) of the smoothing circuit provided in b and can be ignored. Therefore, by implementing the present invention, the portion of the signal to be invalidated can be minimized, so that the reliability of the signal can be improved and the accuracy of gas analysis using this signal can be improved.

FIG. 3 is a block diagram showing another example of the spike noise eliminator 1 'of the present invention. In this figure, components denoted by the same reference numerals as those in FIG. 1 are the same or equivalent members, and thus detailed description thereof will be omitted. This figure differs from FIG. 1 in that the pulse generator 6 is a variable type monostable multivibrator, and the peak value of the spike noise N ₂ is set in this pulse generator 6 in order to set the invalid time of the signal. This is the point that the measuring unit 9 is provided.

FIG. 4 shows the spike noise eliminator 1 'of FIG.
FIG. 6 is a waveform diagram showing a simulated signal waveform for explanation in which only spike noise is extracted from the signals of the respective parts. Hereinafter, FIG.
4, the operation of the present example will be described. In FIG. 4, the same points as those in FIG. 2 will not be described.

In FIG. 4, N _P1 and N _P2 are photocouplers P, N ₂₁ and N ₂₂ are first-stage amplifiers 2, N ₃₁ and N ₃₂ are spike noises output from the signal delay unit 3, x ₁ and x _{2, respectively.}
The peak value of the spike noise, T _21, T ₂₂ denotes the width of the spike noise N _21, N ₂₂ time affects the signal S _2.

The peak value measuring section 9 measures the peak values x ₁ , x ₂ of the spike noises N ₂₁ , N ₂₂ inputted thereto, and calculates a constant a calculated in advance from a time constant (τ = Rf × Cf). , The times T _b1 and T _b2 of the pulse signal generated by the pulse generator 6 are calculated. Then, the pulse generator 6 generates pulse signals P ₆₁ and P ₆₂ during the times T _b1 and T _b2 , and invalidates the signal S ₃ delayed based on the pulse signals P ₆₁ and P ₆₂ , Spike noise N ₃₁ ,
Only it can be removed portion of the N _32.

The width T _{31 of} the spike noises N ₂₁ and N ₂₂ ,
T ₃₂ is a peak value x _{1 of} the spike noises N ₂₁ and N ₂₂ ,
Since widens in proportion to x _2, the spike noise N _31, N ₃₂ using the pulse signal P _61, P ₆₂ having a length proportional to the peak value x _1, x ₂ of the spike noise as in the present example by removing it may be invalidated only signal S ₃ minimum time. Therefore, can further improve the reliability of the measured signal S ₄ for use in gas analysis, it is possible to further carry out the measurement with high accuracy.

In each of the above-described examples, the switch circuit 4a is provided before the synchronous rectifier circuit 4b in order to remove spike noise. However, the present invention is not limited to this. An arbitrary switch circuit may be provided in the middle to invalidate only the spike noise portion. That is, an integration circuit (a circuit that performs a smoothing process)
The spike noise may be removed at any position as long as the preceding stage is used.

In each of the above examples, a chemiluminescence gas analyzer is illustrated as an example of a gas analyzer in which spike noise is included in the output signal of the detector. It is needless to say that the technique is not limited to the detector of the meter, but can be used for other devices such as a gas analyzer using X-rays.

Further, in the above-described example, the pulse generator 6 is a monostable multivibrator (one-shot multivibrator), and has a simpler configuration. However, the present invention is not limited to this, and various methods are conceivable, for example, using a pulse generation circuit using a timer circuit.

[0030]

As described above, according to the method and apparatus for removing spike noise of a gas analyzer of the present invention,
Since the spike noise is detected using the signal before the delay and the signal after the delay is invalidated only for a predetermined time during which the effect of the spike noise appears, the influence of the spike noise input from the detector is removed only for an extremely short invalid time. be able to.
That is, since spike noise is removed before the signal from the detector is input to the integration circuit, the influence of the spike noise can be reduced in a much shorter necessary minimum time regardless of the time constant of the integration circuit. Can be removed. By doing so, in the gas analyzer using the output signal of the detector including the spike noise, even if the input signal from the detector frequently changes, the gas analysis may be adversely affected. Absent.

If the pulse generator is of a variable type that extends a predetermined time for generating a pulse in proportion to the magnitude of the peak value of the spike noise, the time affected by the input spike noise is calculated. Since the invalid time of the signal is set to the minimum necessary time as much as possible, the reliability of the output signal of the detector including spike noise can be increased by minimizing the invalid time.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an example of a spike noise removing device for a gas analyzer according to the present invention.

FIG. 2 is a waveform diagram for explanation in which only spike noise is extracted from a signal flowing through each unit in FIG. 1;

FIG. 3 is a block diagram showing another example of the spike noise elimination device of the gas analyzer of the present invention.

FIG. 4 is an explanatory waveform diagram in which only spike noise is extracted from a signal flowing through each unit in FIG. 3;

FIG. 5 is a block diagram showing an example of a conventionally used spike noise elimination device for a gas analyzer.

FIG. 6 is a waveform chart showing signals at various parts of the spike noise elimination device of FIG. 5;

[Explanation of symbols]

1, 1 ': spike noise eliminator, 2: first stage amplifier,
3 ... signal delay unit, 4 ... spike noise removal unit, 5 ... spike noise detection unit, 6 ... pulse generator, N ₂ ... spike noise, P _6, P _61, P ₆₂ ... pulse, S ₂ ... stage amplifier output Signal, S ₃ ... delayed signal, P ... detector, T
_a, T _b1, T _b2 ... a predetermined time, the time required for detection of T _D ... spike noise, x ... peak value.

Claims (3)

[Claims] 1. A spike noise is detected from a signal output from a first-stage amplifier connected to a detector of a gas analyzer, a pulse is generated for a predetermined time from the detection of the spike noise, and the signal is converted into at least a spike noise. A method for removing spike noise in a gas analyzer, wherein the method is delayed by a time necessary for detection, and the transmission of the delayed signal is blocked only while the pulse is being output to remove spike noise. 2. A spike noise detecting section for inputting a signal output from a first-stage amplifier connected to a detector of a gas analyzer and detecting spike noise from the signal, and detecting a spike noise detected by the spike noise detecting section. A pulse generation unit that generates a pulse for a predetermined time, a signal delay unit that delays the signal by at least a time necessary for detecting spike noise, and transmits the delayed signal as it is when the pulse is not generated. A spike noise elimination device for a gas analyzer, comprising: a spike noise elimination unit that does not transmit the signal when a pulse is generated. 3. The spike noise eliminator of a gas analyzer according to claim 2, wherein the pulse generator is of a variable type that extends a predetermined time for generating a pulse in proportion to the peak value of the spike noise.