JP4134240B2 - Particle size distribution measuring device - Google Patents

Description

  The present invention relates to a particle size distribution measuring apparatus, and in particular, includes a plurality of detectors that detect the light intensity of diffracted light and / or scattered light generated by irradiating dispersed sample particles with light. The present invention relates to a particle size distribution measuring apparatus configured to process each output light intensity signal in a signal processing unit and display the processing result on a display screen, for example.

  The particle size distribution measuring apparatus disperses particles as a sample in an appropriate liquid (dispersion medium) in a dispersion bath to obtain a sample solution, and circulates and supplies the sample solution to a sample cell connected to the dispersion bath through a circulation path. In this state, the sample cell is irradiated with, for example, laser light.

When the sample liquid contains a large amount of particles, the particles are constantly present in the portion of the sample cell that is irradiated with the laser beam, and the scattered light is irradiated by irradiating the particle with the laser beam. Is stably generated, and this scattered light is incident on a detector provided in front, side or rear of the sample cell.
Japanese Patent Laid-Open No. 10-197435

By the way, when there are few particles contained in the sample liquid and the particles occasionally pass through the laser irradiation portion, scattered light is generated only for a moment. Normally, in this type of particle size distribution measuring apparatus, the scattered light intensity signal is repeatedly taken and integrated to increase the reproducibility of the measurement. In general, however, oversized particles ( several hundred μm to several The amount of (mm) is often small in the total amount of particles. Therefore, even after integration, the scattered light intensity signal from the oversized particles is negligible in the total scattered light intensity signal and is indistinguishable from noise. It is difficult to detect as a particle size distribution.

  On the other hand, without integrating the scattered light based on each particle, the particle size distribution calculation is performed each time a scattered light intensity signal output from a plurality of detectors is taken in one scan (one round) in the signal processing unit. Although a method of displaying the particle size distribution on the display screen is conceivable, in this case, unless the signal is captured at high speed, there is a possibility that the scattered light signal from the oversized particles may be missed. That is, as shown in FIG. 6A, if the signal capture interval is long, the scattered light intensity signal from the excessive particles is not captured.

  Further, when the time constant of the signal processing unit is as large as 1 second, the scattered light based on excessive particles that are generated for a moment is attenuated and cannot be detected as shown in FIGS.

  The inconvenience as described above is not only a so-called wet particle size distribution measuring device for measuring particles dispersed in a sample solution, but also a so-called dry particle size distribution for measuring particles dispersed in air such as air. This is also occurring in the measurement apparatus.

  The present invention has been made in consideration of the above-mentioned matters, and its purpose is to reliably detect the presence of excessive particles slightly contained in the sample and display them on the screen as well as bubbles, dust, etc. It is an object of the present invention to provide a particle size distribution measuring apparatus that can detect unnecessary foreign matters and even large particles exceeding the measurement limit to prevent useless measurement.

In order to achieve the above object, the invention according to claim 1 is provided corresponding to a scattered light angle for detecting the light intensity of the diffracted light and / or scattered light generated by irradiating the dispersed sample particles with light. A plurality of detectors, and the signal processing unit sequentially receives the light intensity signals output from these detectors and inputs them to the arithmetic processing unit to perform the particle size distribution calculation. In a particle size distribution measuring apparatus configured to be performed every time an intensity signal is captured , scattered light in which scattered light from oversized particles is superimposed on scattered light from sample particles other than oversized particles of several hundred μm to several mm. The light intensity signal obtained from the detector at the time of detecting the signal includes a pulse distinguishable from the light intensity signal obtained from the detector when the scattered light from the sample particles other than the excessive particles is detected. place Uptake interval of the light intensity signal parts Yes shorten, as the arithmetic processing unit, to determine the content of the excess particles by counting the pulses, and displays this on the display unit of the display screen It is characterized by the construction.

  In the above particle size distribution measuring apparatus, for example, by capturing the scattered light intensity signal at a high speed of, for example, 1 millisecond per scan, the scattered light from a small number of excessive particles that instantaneously pass through the laser beam path can be reliably captured. Thus, the content of excessive particles can be reliably grasped and displayed on the screen, whereby the particle size distribution from small particles to excessive particles can be accurately measured.

In the particle size distribution measuring apparatus, as described in claim 2, the signal processing unit may be configured to display a calculation result of the particle size distribution calculation on a display screen .

  As described above, according to the particle size distribution measuring device of the present invention, the sample particles including small particles to excessive particles can be detected and grasped reliably by detecting and grasping the presence and content of the excessive particles slightly contained in the sample. It is possible to accurately measure the particle size distribution, etc., and to detect foreign substances such as bubbles and dust, as well as large particles exceeding the measurement limit of the device, preventing unnecessary measurement. be able to.

  Hereinafter, the details of the present invention will be described with reference to the drawings. 1 to 3 show an embodiment of the present invention. First, FIG. 1 schematically shows an example of a particle size distribution measuring apparatus according to the present invention. In this figure, 1 is a dispersion bath, inside which a stirring blade 3 rotated by a motor 2 is provided. In addition, an ultrasonic transducer 4 that is vibrated by an oscillator (not shown) is provided outside the bottom. The dispersion bath 1 is supplied with a liquid 6 as a dispersion medium in a tank 5 through a dispersion medium supply pipe 8 having an electromagnetic valve 7 and is supplied to the dispersion bus 1 by an appropriate method. Sample particles P dispersed in the dispersion medium 6 become a predetermined sample liquid 9.

  In FIG. 1, reference numeral 10 denotes a flow cell as a sample cell to which the sample liquid 9 is circulated, and is connected to the dispersion bath 1 by a circulation channel 13 including a pump 11 and a switching valve 12. A sample liquid circulation system 14 is configured. On one side of the flow cell 10, a laser irradiation system 15 including, for example, a laser light source 15a, mirrors 15b and 15c, and a beam expander 15d is provided. Further, on the other side of the flow cell 10, a detector that detects scattered light generated when the laser light L emitted by the condenser lens 16 and the laser irradiation system 15 is irradiated on the sample particles P in the sample liquid 9. 17 is provided. Here, the detector 17 is provided in front of the flow cell 10, for example, a ring detector 17a as a front detector for detecting light scattered at a relatively small angle, and a relatively large angle provided on the side of the flow cell 10. The side detector 17b for detecting the light scattered by and the rear detector 17c for detecting the light scattered at a larger angle provided behind the flow cell 10, and the side detector 17b and the rear detector 17c, Each consists of a plurality of photodiodes.

  Reference numeral 18 denotes a signal processing unit for processing the scattered light intensity signal from the detector 17 and includes the following members. That is, 19a to 19c are preamplifiers (referred to simply as the preamplifier 19 when collectively referred to), and are provided corresponding to the detectors 17a to 17c. Reference numeral 20 denotes a signal switch for sequentially switching scattered light intensity signals that have passed through the preamplifier 19 and sending them to the AD converter 21. A computer 22 is an arithmetic processing unit that performs various controls on each unit of the apparatus and processes a scattered light intensity signal from the detector 17 input via the AD converter 21 to perform a particle size distribution calculation. It is.

  In FIG. 1, reference numeral 23 denotes a display operation unit attached to the computer, which is provided with various function keys 25 around the display unit 24 made of CRT, liquid crystal, etc., and obtained by particle size distribution calculation in the computer 22. The obtained particle size distribution is displayed on the display unit 24 by a graph or a numerical value. A printer 26 outputs the result of the particle size distribution calculation.

Then, in the above particle size distribution measuring apparatus, as the response speed of the signal processing unit 1 8 provided downstream of the detector 17 is increased, an excellent high-speed response as the respective members 19, 20, 21, 22 The scattered light intensity signal from the detector 17 is taken in at a high speed, for example, 1 millisecond per scan, and can be processed. The detector 17 has a sufficiently high sensitivity so that even scattered light from only one large particle can be reliably captured.

  In order to perform the particle size distribution measurement using the particle size distribution measuring apparatus having the above-described configuration, the sample liquid 9 in a uniform steady state without segregation is circulated through the circulation system 14, and the flow cell 10 filled with the sample liquid 9 is supplied to the flow cell 10. On the other hand, when the laser light L is irradiated from the laser light source 15, the laser light L generates scattered light in the sample particles P in the sample liquid 9. This scattered light is incident on the detector 17 provided corresponding to the angle of the scattered light. A scattered light intensity signal is output from the detector 17 based on the incidence of the scattered light, subjected to predetermined processing by the preamplifier 19, and then sent to the AD converter 21 via the signal switching circuit 20, and further to the computer 22 Is taken in.

However, as already explained, the particle size distribution measuring apparatus in this embodiment, the preamplifier 19, as a signal processing unit 18 of the signal switching circuit 20, AD converter 21 and a computer 22, a fast response speed In addition to using a detector, the detector 17 is sufficiently sensitive so that even scattered light from only one large particle can be reliably captured. Since the light intensity of the scattered light generated in the particles is large, the particle size distribution calculation can be performed only with a signal obtained when one sample particle P passes through the flow cell 10.

  In the particle size distribution measuring apparatus, in the sample particle P containing a small amount of excessive particles, scattered light from particles other than the excessive particles is stably detected. Scattered light in which scattered light from excessive particles is superimposed only at the moment of passing. In the particle size distribution measuring apparatus, since the time constant of the signal processing unit 18 from the preamplifier 19 to the computer 22 is sufficiently shortened, the scattered light intensity signal is not attenuated by the excessive particles, and this scattered light intensity is eliminated. In order not to miss the signal capture, the scattered light intensity signal is repeatedly captured at high speed, and based on this, the particle size distribution calculation is performed in the computer 22 to obtain the particle size distribution in the sample particle P. The information is displayed on the display screen 24 a of the display unit 24 of the display operation unit 23 attached to the computer 22.

  As described above, in the particle size distribution measuring apparatus according to this embodiment, the constituent members 19 to 22 of the signal processing unit 18 have high-speed responsiveness, and the scattered light intensity signals are captured from the plurality of detectors 17. To the particle size distribution calculation and the particle size distribution display at high speed, the particle size distribution calculation is performed every time the scattered light intensity signal is captured, and the particle size distribution is displayed on the display screen 24a. It is possible to reliably detect excessive particles contained in a small amount in the sample particle P, which is difficult in the particle size distribution measuring apparatus.

  FIGS. 2 and 3 are diagrams for schematically explaining this. The scattered light intensity signal from the detector 17 is processed by the signal processing unit 18 having a short time constant. The scattered light intensity signals attenuated as shown in FIGS. 3A and 3B are not attenuated as shown in FIGS. 3A and 3B, and are sent to the computer 22 in this state. In the computer 22, the particle size distribution is obtained by performing the particle size distribution calculation at a high speed every time the scattered light intensity signal is input. Since the particle size distribution calculation is performed every time the scattered light intensity signal is input, the particle size distribution is obtained as indicated by reference numerals 27a to 27e in FIG. In this case, when the sample particles P include excessive particles, the distribution of the excessive particles is displayed as indicated by reference numeral 28 in FIG.

  As described above, the particle size distribution measuring apparatus according to the present invention can follow an instantaneous change by using a component having high-speed response as the constituent members 19 to 22 of the signal processing unit 18 so that the light can be tracked. The intensity signal can be taken in and the particle size distribution calculation can be performed at high speed. However, along with this, the display of the particle size distribution on the display screen 24a is also performed at high speed. Switch. Therefore, it is preferable to display the particle size distribution so that the particle size distribution changing on the display screen 24a in which the display contents are switched at high speed can be reliably captured.

  FIG. 4 schematically shows an example of the residual display method of the particle size distribution. FIG. 4A shows the maximum value of the frequency distribution of each particle on the display screen 24a for a set time. An example of remaining display is shown, and FIG. 5B shows an example in which past particle size distributions are overlaid and displayed by a preset number of times. In any of these cases, an observer such as a measurer can surely recognize the presence of oversized particles that are displayed only for a moment when the screen is switched at high speed.

  And when displaying the said particle size distribution on the display screen 24a, you may make it display the particle size (D80, D90, etc.) with respect to the arbitrarily set integrated distribution value by a numerical value or a graph.

  In the case of a graph display, the particle size distribution may be displayed as a bar graph. Further, as shown in FIG. 5, the time is taken on the horizontal axis and the horizontal axis is swept as shown by the arrow in the figure to show the particle size. It may be possible to constantly check the change of.

  Note that the scattered light information of the particles passing through the flow cell 10 can be obtained from the continuous signal information. However, since the information on the excessively contained particles is small, the scattered light intensity signal is measured in pulses. Therefore, the signal frequency of the pulse corresponds to the measurement frequency of the excessive particles. Therefore, the particle size calculation can be obtained by measuring the pulse scattered light of one particle with a plurality of detectors. By counting the number of pulses, the content of excessive particles can be grasped.

It is a figure which shows roughly an example of a structure of the particle size distribution measuring apparatus of this invention. It is a figure for demonstrating the display operation on the screen of the said particle size distribution measuring apparatus. It is a figure for demonstrating the processing state of the scattered light intensity signal in the said particle size distribution measuring apparatus. It is a figure for demonstrating the display mode of the particle size distribution in the said particle size distribution measuring apparatus. It is a figure for demonstrating the display mode of the particle size distribution in the said particle size distribution measuring apparatus. It is a figure for demonstrating the fault of a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 17 Detector 18 Signal processing part 19 Preamplifier 20 Signal switcher 21 AD converter 22 Computer 24a Display screen 27a-27e Particle size distribution P Sample particle L Light

Claims (2)

It has a plurality of detectors provided corresponding to the angle of scattered light that detects the light intensity of diffracted light and / or scattered light generated by irradiating the dispersed sample particles with light, and is output from each of these detectors. The particle size distribution is configured so that the signal processing unit sequentially captures the light intensity signal and inputs it to the arithmetic processing unit to perform the particle size distribution calculation, and to perform this particle size distribution calculation every time the light intensity signal is captured. In the measuring device, the light intensity signal obtained from the detector when the scattered light obtained by superimposing the scattered light from the excessive particles on the scattered light from the sample particles other than the excessive particles of several hundred μm to several mm is excessive. The light intensity signal capturing interval of the signal processing unit is shortened so as to include a pulse that can be distinguished from the light intensity signal obtained from the detector when detecting scattered light from sample particles other than particles, To grasp the content of the excess particles by counting the serial pulse, a particle size distribution measuring apparatus characterized by being configured to display this on the display unit of the display screen. The particle size distribution measuring apparatus according to claim 1, wherein the signal processing unit is configured to display a calculation result of the particle size distribution calculation on a display screen .

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