JPH0479531B2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a particle analyzer that uses a conductive particle detector that outputs a waveform that may include wave height distortion.

[Conventional technology]

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 separates the electrodes with an insulating wall with micropores. However, a potential difference is applied between the two electrodes so that current flows between the electrodes only through the pores. In other words, when a water pressure difference is applied between the liquid on both sides and the particles flow together with the liquid through the pores, if the pore size is chosen appropriately for the particle size, a current change proportional to the particle volume will occur between the electrodes in response to the passage of the particles. This is a device that takes advantage of the characteristics that occur in 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. As shown in the schematic diagrams A, B, C, and D of the passage of particles 12 through the pore 11 in FIG. 7 and the waveform diagram in FIG. 8, the area around the entrance of the pore 11 has a high current line density and sensitivity. is high. However, the diagram is a collective representation, and the suspension is generally diluted to such an extent that each state occurs separately. A, the particle 12 is placed very close to the inner peripheral surface of the pore 11.
When passing through, the wave height value is high at the entrance and exit, and the area between them is almost flat. B is a case where two particles 12 pass near the center of the pore 11, and two particles 12 may exist at the same time, and the waveform has two peaks, with a relatively deep peak between them. It forms a valley. 3 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 pore passes obliquely near the inner peripheral surface of the pore 11 at the entrance and near the center at the exit;
The waveform has a high wave height section at the entrance and a flat section following this. Conductive particle detection devices have a simple structure and high sensitivity, so they are widely used, although they have problems with pore clogging when scanning suspensions and particle signal distortion due to particle passage paths. This is one of the particle measuring devices available today. 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.
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 waveform of the detected particle signal 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.

[Problems to be solved by the invention]

Although the fluid device that restricts the flow described above 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. Patent Application No. 59-115331 (filed on June 4, 1988)
This patent application is filed by the same applicant, and the invention particle analyzer of this application improves the above-mentioned problem. However, with this particle analyzer,
There were problems in that the conditions were difficult to set, the analysis accuracy was not high enough, and the circuit was complicated. An object of the present invention is to provide a particle analyzer with a simpler circuit configuration and higher analysis accuracy.

[Means to solve the problem]

The technical means (structure of the invention) taken by this invention to solve the above problems are as follows. That is, 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 positive and negative levels near 0 level. a discriminating means that generates a pulse when the pulse is outside a predetermined threshold; a predetermined threshold variable means that changes the predetermined threshold to a large or small degree according to a large or small change in the input signal; and an output waveform of the differentiating means is at 0 level. 0 level detection means for detecting a point in time; signal level holding means for holding the signal level of the generated quantity of electricity according to an output signal of the discrimination means and an output signal of the 0 level detection means; and an output of the discrimination means. A/D converter for A/D converting the output signal of the signal level holding means according to the signal;
D conversion means.

[Effect]

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

【Example】

An embodiment of the present invention will be described based on FIGS. 1 to 3. FIG. 1 shows a block diagram of a waveform processing device which is the main part of a particle analyzer, FIG. 2 shows waveforms of each part showing its operation, and FIG. 3 is 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 differentiator circuit 31, an ACl circuit (Automatic Comparator Level circuit) 32, an insulated comparator 33, a trailing edge comparator 34, a zero cross comparator 35, an AND circuit 36, a one shot circuit 37, a convert start pulse circuit 38, and a phase shift correction. circuit 39, sample hold circuit 40, peak value A/D conversion circuit 41, and
It consists of a T _n center pulse circuit 42. a is an input terminal line that is input from the conductive particle detection device 7 to the differentiation circuit 31 and the phase shift correction circuit 39. The differentiating circuit 31 is an example of the "differentiating means" referred to in the configuration of the invention. Leading edge comparator 33, trailing edge comparator 34
and T _n center pulse circuit 42 are an example of the "discrimination means" referred to in the configuration of the invention. The zero cross comparator 35 is an example of "0 level detection means" in the configuration of the invention. The ACL circuit 32 is an example of the "predetermined threshold variable means" in the configuration of the invention. The sample hold circuit 40 is an example of "signal level hold means" in the configuration of the invention. The peak value A/D conversion circuit 41 is an example of "A/D conversion means" in the configuration of the invention. The output terminal of the differentiating circuit 31 is connected to the input terminals of a leading edge comparator 33, a trailing edge comparator 34, and a zero cross comparator 35. A T _n center pulse circuit 42 is connected between the output terminals of the leading edge comparator 33 and the trailing edge comparator 34,
The output terminal of the T _n center pulse circuit 42 and the output terminal of the zero cross comparator 35 are connected to the input terminal of the AND circuit 36 . The output terminal of the AND circuit 36 is connected to the input terminal of the one shot circuit 37, and the output terminal of the one shot circuit 37 is connected to the trigger terminal of the sample hold circuit 40. The one shot circuit 37 generates a trigger pulse for the sample hold circuit 40. The output terminal of the phase shift correction circuit 39 is connected to the input terminal of the sample hold circuit 40, and the output terminal of the sample hold circuit 40 is connected to the input terminal of the peak value A/D conversion circuit 41. An output terminal of the sample hold circuit 40 is connected to an input terminal of a peak value A/D conversion circuit 41. The sample hold circuit 40 outputs an output to the peak value A/D conversion circuit 41 when triggered by the output of the one shot circuit 37. The peak value A/D conversion circuit 41 outputs the signal to the grain size recording device 9 shown in FIG. The output terminal of the trailing edge comparator 34 is connected to the input terminal of the convert start pulse circuit 38;
The output terminal of the conversion start pulse circuit 38 is connected to the trigger terminal of the peak value A/D conversion circuit 41. The trigger pulse generated by the conversion start pulse circuit 38 is input to the peak value A/D conversion circuit 41. Next, the operation of the waveform processing device 8 will be explained based on FIG. 2. Particle pulses of various waveforms amplified from the conductive particle detection device 7 are input to the differentiation circuit 31 and the phase shift correction circuit 39 via the input terminal a. The waveform of the input signal is illustrated in FIG. 2a. That is, the waveforms corresponding to B, A, and C in FIG. 7 are shown in this order. The differentiating circuit 31 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 shown in FIG. Waveform b is obtained. The ACL circuit 32 includes a leading edge comparator 33,
This is a circuit that supplies a comparison voltage for the trailing edge comparator 34, and the comparison voltage changes from large to small according to large and small changes in the input signal. Note that when there is no signal, a bias DC voltage is supplied. The output voltage of the ACL circuit 32 is applied as a positive voltage to the leading edge comparator 33 (see _E1 in Fig. 2b), whereas a negative voltage is inverted and applied to the trailing edge comparator 34 (see Fig. 2b). (see E ₂ ),
The output of the differentiating circuit 31 is similarly applied. The leading edge comparator 33 generates an output pulse when the output waveform of the differentiating circuit 31 exceeds the level voltage on the positive side (see FIG. 2c). The trailing edge comparator 34 generates an output pulse when the output waveform of the differentiating circuit 31 exceeds the level voltage to the negative side (see 2d). The T _n center pulse circuit 42 rises when the output of the leading edge comparator 33 falls;
A falling pulse is generated at the rising edge of the output of the trailing edge comparator 34 (see FIG. 2e). The zero cross comparator 35 sets the comparison voltage to approximately zero voltage and generates an output pulse when it slightly exceeds zero (see FIG. 2f). The output of the zero cross comparator 35 and the output of the T _n center pulse circuit 42 are connected to an AND circuit 36.
, the AND circuit 36 outputs a pulse to the one-shot circuit 37 (see FIG. 2g). This pulse causes one-shot circuit 37
outputs a hold start trigger signal to the trigger terminal of the sample and hold circuit 40 (see FIG. 2h). Upon receiving the hold start trigger signal, the sample hold circuit 40 holds the input signal from the phase shift correction circuit 39 at that point in time (see FIG. 2j). On the other hand, the output of the trailing edge comparator 34 is input to the conversion start pulse circuit 38, and the conversion start pulse circuit 38 outputs the conversion start pulse to the peak value A/D conversion circuit 41 according to the rising edge of the trailing edge pulse. (See Figure 2 i). The peak value A/D conversion circuit 41 A/D converts the signal peak value held by the conversion start pulse and outputs it to the grain size recording device 9. Next, we will consider means for obtaining a stable pulse output without being affected by waveform distortion or signal level fluctuation when voltages are compared between differential signals using a comparator. FIG. 4 shows the characteristics of the leading edge pulse and the trailing edge pulse. The left side of the figure shows a normal waveform, and the right side shows an abnormal waveform. A shows the input waveform, B shows the differential waveform, C shows the leading edge pulse, and D shows the trailing edge pulse. Differentiating the blood cell signal emphasizes the distorted parts. Therefore, if the comparator voltage is set to be constant as shown in FIG. B, the pulse width will not only be applied to the distorted portion but also fluctuate depending on the magnitude of the input signal. In order to solve these two problems, the following two methods can be considered. (1) Automatically pick up the half-width of the differential signal. (2) Move the comparison voltage of the comparator according to the input level. The circuit shown in FIG. 5 employs the method described below. In FIG. 5, 33 is a leading edge comparator;
C ₁ is a capacitor, R ₁ , R ₂ and R ₃ are resistors, and V _C is a DC power supply. A capacitor C ₁ and a resistor R ₁ constitute a differentiating circuit 31. 32a is the positive side portion of the ACL circuit 32. When there is no signal, a comparison voltage V _C is applied to the input terminal of the leading edge comparator 33. When there is an input signal, it is reduced to R ₃ /(R ₂ + R ₃ ) and the comparison voltage V _C
and is applied to the (-) input terminal of the leading edge comparator 33. At this time, the (+) input terminal has
The differential signal shown in Figure C, which is differentiated by the time constants C ₁ and R ₁ , is applied, and the comparator comparison voltage is synchronized with the input signal (dashed line). The waveforms of this circuit are shown in FIG. A represents the input waveform, B represents the differential waveform, and the broken line represents the comparator voltage. C is the comparator output waveform. The characteristics of this circuit are that it is not susceptible to the influence of the intermediate portion of the differential waveform, and that the comparison voltage also changes in a manner that follows changes in the signal level, so that fluctuations in the pulse width can be suppressed. With the above configuration, the influence of low-level distortion in the middle part of the output of the differentiating circuit 31 is suppressed from being applied to the zero-cross comparator 35, the leading edge comparator 33, and the trailing edge comparator 34, and the accuracy of particle analysis is suppressed. In addition, the circuit configuration is simpler than that of the invention disclosed in Japanese Patent Application No. 115331/1986. Further, the reliability of the output of the trailing edge pulse increases, and it becomes possible to actually use it as a conversion start pulse, and it becomes possible to sample and hold pulses other than the normal pulse level. Therefore, simpler logic can be used, the circuit configuration can be further simplified, and accuracy can be improved. Therefore, it is also possible to obtain an accurate particle size distribution signal by simply adding a processing circuit to a conventional detection mechanism without using a sheath mechanism.

【Effect of the invention】

According to this invention, compared to the one disclosed in Japanese Patent Application No. 59-115331, it is possible to simplify the circuit configuration and further improve the accuracy of analysis.

[Brief explanation of the drawing]

Fig. 1 shows the block of the waveform processing device which is the main part of a particle analyzer according to an embodiment of the present invention, Fig. 2 shows the waveforms of each part showing its operation, and Fig. 3 shows the overall configuration of the particle analyzer. Figure 4 is a characteristic diagram showing the characteristics of leading edge pulses and trailing edge pulses, Figure 5 is a circuit diagram around the leading edge comparator circuit, Figure 6 is an improved characteristic diagram, and Figure 7 is a conventional characteristic diagram. A sectional view of the main part of the example, and FIG. 8 is a waveform diagram thereof. 31...differentiation circuit (differentiation means), 32...ACL
circuit (predetermined threshold variable means), 33...leading edge comparator, 34... trailing edge comparator, 42...T _n
Center pulse circuit, 33, 34, 42... Discrimination means, 35... Zero cross comparator (0 level detection means), 40... Sample hold circuit (signal level holding means), 41... Peak value A/
D conversion circuit (A/D conversion means).

Claims (1)

[Claims] 1. means for generating an amount of electricity accompanying the passage of particles through the pores, means for differentiating the generated amount of electricity, and generating a pulse when the output waveform of the differentiating means is outside a predetermined threshold between positive and negative levels near the 0 level; Discrimination means;
The predetermined threshold is set to large or small depending on large or small changes in the input signal.
a predetermined threshold variable means that changes by a small amount; a 0 level detecting means for detecting a point in time when the output waveform of the differentiating means is at the 0 level; and an output signal of the discriminating means and an output signal of the 0 level detecting means. A particle analyzer comprising: a signal level hold means for holding a signal level of an electric quantity; and an A/D conversion means for A/D converting the output signal of the signal level hold means based on the output signal of the discrimination means.