JPH0352821B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a particle analyzer that is applied to a conductive particle detector that outputs a waveform that may include wave height distortion.

Conventional structure and its problems A conductive particle detection device immerses a pair of electrodes in a suspension of measurement particles suspended in a thin electrolyte solution with a salt concentration of about 0.8%, and connects the electrodes between the two electrodes. The two electrodes are separated by an insulating wall with micropores, and a potential difference is applied between the two electrodes so that current flows between the electrodes only through the pores.By applying a water pressure difference between the liquid on both sides, particles flow together with the liquid through the pores. This device utilizes the property that when a particle is passed through, a current change proportional to the particle volume occurs between the electrodes in response to the passage of the particle, if the pore size is appropriately selected relative to the particle size.

A detailed examination of the particle detection waveform reveals that only when the particle passes near the center of the pore, the pulse peak value is proportional to the particle volume, while the waveform that passes near the periphery of the pore shows a partially high pulse peak value. In particular, it has been confirmed that errors occur in particle size information.

The state of passage of particles 12 through pores 11 in Fig. 6a,
As shown in the schematic diagrams B, C, and D and the waveform diagram in FIG. 7, the current line density around the entrance of the pore 11 is high and the sensitivity is high. However, the diagram is a collective representation and is generally diluted to the extent that each state occurs separately.

In A, the particles 12 pass very close to the inner peripheral surface of the pores 11, exhibiting high wave height values at the entrance and exit, and are almost flat between them. B passes near the center of the pore 11, but at the same time two particles 12
It is a way of passing such that there may be
The waveform has two peaks, with a relatively deep valley between them. C shows a case where the particle 12 passes exactly through the center of the pore 11, and shows a neat mountain-shaped waveform with a symmetrical peak at one point. D is a case in which the wave passes obliquely so that it passes near the inner peripheral surface of the pore 11 at the entrance and near the center at the exit, and the waveform has a high wave height section at the entrance followed by a flat section. .

Conductive particle detection devices have a simple structure and high sensitivity, so they are widely used, although they have the disadvantages of clogging of pores for scanning in suspensions and particle signal distortion due to particle passage paths. This is one of the particle measuring devices. In the field of precision particle analysis, countermeasures against the detection distortion of this device have long been an issue, and various studies have been conducted.

``Hydrodynamic focusing'' or ``sheath flow'' applies Bernoulli's principle to narrow down the pore flow path of particles to a narrow area in the center.
It is called. One such method is an improvement method in terms of fluid dynamics, which is found in Japanese Patent Application Laid-Open No. 53-119086 and others.

Another improvement method is to analyze the detected particle signal waveform and select a waveform that ignores all distorted signals other than undistorted signals passing near the center of the pore.

There are many others, but these two are representative.

Although the fluid device that restricts the flow is ideal, it requires a complicated fluid mechanism, making the device expensive and difficult to maintain.

For example, as a discriminating circuit for waveform selection,
Some of these are disclosed in Japanese Patent Publication No. 54-26919 and Japanese Patent Publication No. 12980/1983. In both of these, each voltage level obtained by peak-holding the particle waveform is divided into a predetermined ratio is set as a threshold voltage, and each threshold voltage is compared with the delayed particle waveform. Waveforms are selected by relatively measuring the waveform duration at each level using an integrating circuit and comparing it with a normal reference value.

However, since the number of signals ignored by this waveform selection increases considerably, it is necessary to increase the number of samplings to maintain accuracy, which leaves problems in terms of efficiency and accuracy.

OBJECTS OF THE INVENTION It is an object of the present invention to provide a particle analyzer that is relatively simple in structure, low cost, easy to maintain, has high particle distribution measurement accuracy, and has a high processing speed.

Structure of the Invention The particle analyzer of the present invention includes a means for generating an amount of electricity accompanying the passage of particles through a pore, a means for differentiating the amount of electricity generated, and an output waveform of the differentiating means between both positive and negative levels near the 0 level. means for distinguishing the external time width into long, short T ₁ and T ₂ (T ₁ > T ₂ ) when the output waveform is outside a predetermined threshold of the output waveform, and when the output waveform passes through both the positive and negative levels in one direction. The transit time width is long and short t ₁ , t ₂
(t ₁ > t ₂ ); means for detecting a zero-cross point in the predetermined passing direction when the outside-threshold time width is long T ₁ and the passing time width is short t ₂ ; means for detecting _a zero-cross point in a direction opposite to the predetermined passing direction when the off-threshold time width is short T ₂ and the passing time width is long t ₁ ; When the above-mentioned passing time width is short T ₂ within a predetermined time after that, the above-mentioned outside-threshold time width is short T ₂
and means for detecting a zero-crossing point in the predetermined passing direction when the passing time width is short _t2 , and means for holding the value of the amount of generated electricity at each held point. It is something.

The effects of the structure of the present invention will become clear from the explanation of the operation in the following embodiments.

DESCRIPTION OF THE EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. 1 to 4. FIG. 1 shows the blocks of a waveform processing device which is the main part of the particle analyzer, FIG. 2 shows the waveforms of each part showing its operation, and FIG. 3 shows a conceptual diagram of the overall structure of the particle analyzer.

In FIG. 3, a conductive particle detection device 7 includes a sample container 1, a particle suspension sample 2, a detector (insulating wall) 4 having pores 3, and electrodes 5, 6, and includes a fluid for flowing and quantifying the sample 2. It consists of a control section and a detection section that applies a potential difference to the electrodes 5 and 6 to generate and amplify a detection pulse.

The waveform processing device 8 constitutes the main part of the present invention, and FIG. 1 shows its block diagram. The waveform processing device 8 includes a differentiation circuit 51, a zero cross comparator 52, a Tm center pulse circuit 53, a pulse width detection circuit 54, and digital filters 55, 5.
9, delay circuit 56, phase shift correction circuit 64, double pulse gate circuit 58, one shot circuit 6
3. Consists of a sample hold circuit 65, a peak value A/D conversion circuit 66, AND circuits 57, 60, 61, and an OR circuit 62.

A is an input terminal line that is input from the conductive particle detection device 7 to the differential circuit 51 and the phase shift correction circuit 64, and the waveform of the input pulse is illustrated in a in FIG. 2. That is, the waveforms corresponding to B, A, and C in FIG. 7 are shown in this order.

The output of the differentiating circuit 51 is input to a zero cross comparator 52, a Tm center pulse circuit 53, and a pulse width detection circuit 54. The output of the pulse width detection circuit 54 is input to a digital filter 55,
Its output is input to a delay circuit 56. Tm
The output of the center pulse circuit 53 and the output of the delay circuit 56 are input to an AND circuit 57, and the output thereof is input to a double pulse gate circuit 58. The output of the double pulse gate circuit 58 and
The output of the Tm center pulse circuit 53 is input to an AND circuit 61.

The output of the Tm center pulse circuit 53 is input to the digital filter 59.
and the output of the zero-cross comparator 52 are input to an AND circuit 60. AND circuit 60
The output of and the output of the AND circuit 61 are the OR circuit 6
2, and its output is input to the one-shot circuit 63.
is input.

The output of the phase shift correction circuit 64 is input to a sample hold circuit 65, and when triggered by the output of the one shot circuit 63, the output is output from the sample hold circuit 65 to a peak value A/D conversion circuit 66. The peak value A/D conversion circuit 66 outputs the signal to the grain size recording device 9 shown in FIG.

The operation of the waveform processing device 8 will be explained.

Amplified particle pulses of various waveforms are sent from the detection device 7 to the input terminal line a.

The differentiating circuit 51 is a circuit for obtaining a signal proportional to the rate of change of the signal having an appropriate time constant, and an output corresponding to the slope coefficient value of the input waveform (a) in FIG. 2 is obtained on the signal line b. The differential waveform (b) is obtained.

The zero cross comparator 52 is a saturation amplifier that operates in the positive range of waveform (b), and outputs the line j
As shown in the waveform (j) above, a zero-cross differential pulse waveform (j) is obtained along with a noise pulse.

The Tm center pulse circuit 53 has a threshold voltage given by ±v ₀ , and its output rises when a voltage exceeding +v ₀ on the negative side is input, and falls when it exceeds -v ₀ on the negative side. Therefore, the output waveform becomes a Tm center pulse represented by waveform (e) on line e.
In other words, a pulse is generated when the input is between ±v ₀ at the trailing edge of a pulse with a peak value of +v ₀ or more.

The pulse width detection circuit 54 is a supersaturation amplifier that saturates at a pulse voltage of _v0 or more, and the output waveform (c')
is sent out on line c′.

The digital filter 55 internally generates a 10 μs reference pulse at the rising edge of the input, and does not pass the input pulse if the input pulse width is 10 μs or less. arise.

The delay circuit 56 holds the trailing edge of the normal pulse of waveform (c) for a fixed period of time to apparently delay the pulse and output waveform (d).

The above-described pulse width detection circuit 54, digital filter 55 and delay circuit 56 are configured so that "the output waveform of the differentiating means is positive near 0 level,"
This constitutes a "means A" for distinguishing the external time width into long, short T ₁ and T ₂ (T ₁ >T ₂ ) when it is outside a predetermined threshold between both negative levels.

Examples of long T ₁ and short T ₂ of the off-threshold time width are shown in 4A and 4B.

The AND circuit 57 inputs the Tm center pulse of waveform (e) and the output of the waveform (d) of the delay circuit 56, selects a normal waveform pulse, and outputs a pulse of waveform (f).

That is, waveform C and waveform B are output as normal waveforms, and waveform A is ignored as an abnormal waveform.

The above means A, the zero-cross comparator 52, and the AND circuit 57 serve as the "zero-crossing point in the predetermined passing direction when the above-mentioned out-of-threshold time width is long _T1 and the passing time width is short _t2 .""C" constitutes a means for detecting.

The digital filter 59 internally generates a 2 μs reference pulse at the rising edge of the input, and functions to pass only pulses with a pulse width of 2 μs or more.
As a result, waveform (i) is obtained.

The above-mentioned Tm center pulse circuit 53 and digital filter 59 set the passing time widths of long and short t ₁ , t ₂ (t ₁ > t ₂ ).

Examples of long and short transit time widths t ₁ and t ₂ are also shown in FIGS. 4A and 4B.

The AND circuit 60 inputs the waveform (j) of the zero-crossing differential pulse and the output of the digital filter 59, and selects the zero-crossing point of the Tm center pulse. As a result, only the _j1 pulse in waveform (j) is output.

The above means B, the zero-cross comparator 52, and the AND circuit 60 according to the configuration of the invention are configured to perform a process in a direction opposite to the predetermined passing direction when the off-threshold time width is short _T2 and the passing time width is long _T1 . This constitutes "means D for detecting the zero-crossing point."

The double pulse gate circuit 58 is a constant pulse width pulse generation circuit, and the pulse width is selected to cover the double pulse generation range of the Tm center pulse of waveform (e), and the double pulse of the waveform (b) is connected to the AND circuit 6.
It functions to pass through to 1.

In other words, the above means C distinguishes between waveform C and waveform A, selects only waveform C, and ignores waveform A, but this function is double as shown in waveform (f). The result is that the second peak in the pulse waveform B is also ignored. Therefore, a double pulse gate circuit 58 and an AND circuit 61 are provided to restore the second peak of this ignored double pulse.

The AND circuit 61 is the double pulse gate circuit 5
Since the output waveform (g) of 8 and the output waveform (e) of the Tm center pulse circuit 53 are ANDed, the output waveform (h) is obtained.

That is, the means C and the double pulse gate circuit 5
8 and the AND circuit 61, as stated in the configuration of the invention, ``the above-mentioned off-threshold time width is short _T2 within a predetermined time after the case where the above-mentioned off-threshold time width is long _T1 and the above-mentioned passing time width is short _T2. and when the passing time width is short _t2 , a means for detecting a zero-cross point in the predetermined passing direction is constituted.

As described above, the AND circuit 60 and the AND circuit 61
Output waveform (k) of the OR circuit 62 with two inputs as the output of
coincides with the timing indicating the normal peak value of input waveform (a). At that timing, the one shot circuit 63 is driven to generate a sample hold trigger pulse (l), and the appropriate peak value of the input waveform (a) corrected by the phase shift correction circuit 64 is held in the sample hold circuit 65. Output the waveform (m).

On the other hand, the peak value A/D conversion circuit 66 performs high-speed A/D conversion of the hold peak value using the same trigger pulse (l). This circuit 66 is an integral counting type circuit that starts integration with a trigger pulse and counts by opening the oscillator gate until the hold peak value is reached, and can obtain sufficient speed.

The particle size recording device 9 provides a channel for each wave height value group divided in advance, and records the number of pulses in each channel.
The totals are displayed on CRT or printed paper. As this particle size recording device, for example,
What is disclosed in Publication No. 14739 can be used.

If the particle size distribution is drawn only by conventional wave height classification, the fifth
Since it also detects signals with abnormally high distortion waveforms as shown in Figure B, a strain distribution with more large-diameter particles than the actual distribution in Figure 5A can be obtained. According to this, it is possible to prevent the above-mentioned distorted distribution and obtain a correct actual distribution.

In addition, compared to conventional flow restricting fluid devices, the structure is simpler and costs can be reduced, and compared to conventional waveform selection methods, measurement accuracy is improved if the number of samples is the same.

In the conductive particle detection device 7, when the pore length of the pore 11 of the insulating wall 10 is larger than the pore diameter, the center peak value of the waveform is more accurately proportional to the particle volume regardless of the particle passing position. If the hole length and hole diameter are set in this way, accuracy can be further improved. It has been found that it is good to make the pore length approximately 1.1 to 1.5 times the pore diameter.

Effects of the Invention According to the present invention, there are effects that the structure can be simplified, costs can be reduced, maintenance can be facilitated, and particle size distribution can be measured with high precision.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a waveform processing device according to an embodiment of the present invention, Fig. 2 is a waveform diagram of each part showing its operation, Fig. 3 is a conceptual diagram of the overall configuration, and Fig. 4 is a diagram for explaining the operation. FIG. 5 is a distribution characteristic diagram, FIG. 6 is a sectional view of the main part of the conventional example, and FIG. 7 is its waveform diagram. 51...differentiation circuit (differentiation means), A...extra-threshold time width discrimination means, B...passing time width discrimination means, C...
...Zero cross point detection means, D...Zero cross point detection means, E...Zero cross point detection means, 6
5...Sample hold circuit (hold means).

Claims (1)

[Scope of Claims] 1. A means for generating an amount of electricity accompanying the passage of particles through a pore, a means for differentiating the generated amount of electricity, and an output waveform of the differentiating means outside a predetermined threshold between both positive and negative levels near the 0 level. The out-of-threshold time width when T 1 is long, short T ₁ ,
T ₂ (T ₁ >T ₂ ), and a means for distinguishing the passing time width when the output waveform passes through both the positive and negative levels in one direction as long, short t ₁ and t ₂ (t ₁ >t ₂ ) means for detecting a zero-cross point in the predetermined passing direction when the above-mentioned off-threshold time width is long T ₁ and the above-mentioned passing time width is short t ₂ ; short
means for detecting a zero-cross point in a direction opposite to the predetermined passing direction when T ₂ and the passing time _{width is long t 1 ;} means for detecting a zero-cross point in the predetermined passing direction when the outside-threshold time width is short T ₂ and the passing time width is short t ₂ within a predetermined time after the case of t ₂ ; and means for holding the value of the amount of generated electricity at each point in time. 2. The particle analyzer according to claim 1, wherein the pores in the electrical quantity generating means have a pore length larger than a pore diameter.