JP4294384B2 - Particle size distribution measuring device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
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.
[0002]
[Prior art]
[Patent Document 1]
JP, 10-197435, A The above-mentioned particle size distribution measuring device disperses particles as a sample in an appropriate liquid (dispersion medium) in a dispersion bath to make a sample solution, and this sample solution is connected to the dispersion bath by a circulation path. In this state, the sample cell is irradiated with, for example, laser light.
[0003]
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.
[0004]
[Problems to be solved by the invention]
By the way, when there are few particles contained in the sample liquid and the particles occasionally pass through the laser irradiation part, scattered light is generated only for a moment. Usually, 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. However, in general, an excessively large particle (several hundred μm to several mm) is used. ) In many cases, the ratio in the total amount of particles is often small. Therefore, even after integration, the scattered light intensity signal from the excessive particles becomes very small in the total scattered light intensity signal, and is indistinguishable from noise. It is difficult to detect as a particle size distribution.
[0005]
On the other hand, without integrating the scattered light based on each particle, the particle size distribution calculation is performed every time one time (one round) of the scattered light intensity signals output from the plurality of detectors is taken in the signal processing unit. Although a method of displaying the diameter distribution on the display screen is conceivable, in this case, unless the signal is taken in at high speed, there is a possibility that the scattered light signal from the excessive particles is 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.
[0006]
Furthermore, when the time constant of the signal processing unit is as large as 1 second, the scattered light intensity signal based on the excessively generated particles is attenuated as shown in FIGS. 6 (B) and (C), This cannot be detected.
[0007]
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.
[0008]
The present invention has been made in consideration of the above-mentioned matters, and the purpose thereof is a particle size distribution capable of reliably detecting the presence of excessive particles slightly contained in a sample and displaying them on a screen. It is to provide a measuring device.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the present invention comprises a plurality of detectors for detecting the light intensity of diffracted light and / or scattered light generated by irradiating light to dispersed sample particles, and outputs from each of these detectors. In a particle size distribution measuring apparatus configured to process a light intensity signal to be processed in a signal processing unit and display the processing result on a display screen, the signal processing unit is used as a member constituting the signal processing unit. The time constant is less than the time required for one sample particle to pass through the sample cell, and the particle size distribution every time light intensity signals from the plurality of detectors are input in this signal processing unit. when performing operations, light intensity signal of excessive particle contained in the sample particles is measured by a pulse, to grasp the content of the excess particles by counting the pulses, and oversize By using the light intensity signal which is continuous in the operation of the sample particles other than by performing a particle size distribution calculation determined the particle size distribution of the sample particles were attached to the particle size distribution determined in the signal processing unit The display operation unit is configured to display on the display screen of the display unit.
[0010]
In the above particle size distribution measuring apparatus, as a component of the signal processing unit, a member having a high-speed response whose time constant is shorter than the time required for one sample particle to pass through the sample cell is used. It becomes possible to follow the change, and capture of the scattered light intensity signal and calculation of the particle size distribution can be performed at high speed. That is, for example, since the scattered light intensity signal can be captured at a high speed, for example, 1 millisecond per scan, it is possible to reliably capture scattered light from a small number of excessive particles that instantaneously pass through the laser light path. By displaying the particle size distribution obtained by performing particle size distribution calculation on the display screen, it is possible to reliably display the particle size distribution from small particles to oversized particles and reliably detect the presence of oversized particles. .
[0011]
And in the particle size distribution measuring apparatus of this invention, when displaying the said particle size distribution calculated | required in the said signal processing part on the said display screen as described in Claim 2, only for the preset time, The maximum value of the frequency distribution of particles is displayed on the display screen, or the particle size distribution obtained in the signal processing unit is displayed on the display screen according to claim 3. It is desirable that the past particle size distribution is overlaid and displayed on the display screen a predetermined number of times. In any of these cases, the measurer can reliably recognize the presence of excessive particles that are displayed only for a moment when the screen is switched at high speed.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
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 the 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.
[0013]
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.
[0014]
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.
[0015]
In FIG. 1, reference numeral 23 denotes a display operation unit attached to the computer 22, which is provided with various function keys 25 around the display unit 24 made of a CRT, a liquid crystal, or the like. The obtained particle size distribution is configured to be displayed on the display screen 24a of the display unit 24 by a graph or a numerical value. A printer 26 outputs the result of the particle size distribution calculation.
[0016]
In the particle size distribution measuring apparatus, the time constant of the signal processing unit 18 provided at the subsequent stage of the detector 17 is the time required for one sample particle P to pass through the flow cell 10 (irradiates the flow cell 10). The member 19, 20, 21, 22 is excellent in high-speed response so that the response speed of the signal processing unit 18 is faster than the time required for crossing the optical axis of the laser beam L). The scattered light intensity signal from the detector 17 is captured 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.
[0017]
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 a, 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.
[0018]
By the way, as already explained, in the particle size distribution measuring apparatus in this embodiment, the time constant of the signal processing unit 18 including the preamplifier 19, the signal switching circuit 20, the AD converter 21, and the computer 22 is One that is shorter than the time required for one sample particle P to pass through the flow cell 10, that is, one that has a high response speed is used. Even if the scattered light from only one large particle is used as the detector 17, In order to reliably capture the light, a material having a sufficiently high sensitivity is used. Therefore, if the particle is large, the light intensity of the scattered light generated in the particle is large. The particle size distribution calculation can be performed using only the signal obtained when passing through.
[0019]
In the particle size distribution measuring apparatus, even in the sample particles 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 signal is captured. In order to prevent omission, the scattered light intensity signal is repeatedly taken 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 particles P, and this particle size distribution is stored in the computer 22. The information is displayed on the display screen 24 a of the display unit 24 of the attached display operation unit 23.
[0020]
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.
[0021]
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.
[0022]
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.
[0023]
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.
[0024]
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.
[0025]
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.
[0026]
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.
[0027]
【The invention's effect】
As described above, according to the particle size distribution measuring apparatus of the present invention, it is possible to reliably detect the presence of excessive particles slightly contained in the sample, and to reliably display this on the screen. According to the particle size distribution measuring device, it is possible to detect contamination of foreign matters such as bubbles and dust, contamination of large particles exceeding the measurement limit of the device, and the like, and wasteful measurement can be prevented.
[Brief description of the drawings]
FIG. 1 is a diagram schematically showing an example of the configuration of a particle size distribution measuring apparatus according to the present invention.
FIG. 2 is a diagram for explaining a display operation on a screen of the particle size distribution measuring apparatus.
FIG. 3 is a diagram for explaining a processing state of a scattered light intensity signal in the particle size distribution measuring apparatus.
FIG. 4 is a view for explaining a display mode of a particle size distribution in the particle size distribution measuring apparatus.
FIG. 5 is a view for explaining a display mode of a particle size distribution in the particle size distribution measuring apparatus.
FIG. 6 is a diagram for explaining a drawback of a conventional technique.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 17 ... Detector, 18 ... Signal processing part, 19 ... Preamplifier, 20 ... Signal switching device, 21 ... AD converter, 22 ... Computer, 24a ... Display screen, 27a-27e ... Particle size distribution, P ... Sample particle, L …light.

Claims (3)

Provided with a plurality of detectors that detect the light intensity of diffracted light and / or scattered light generated by irradiating dispersed sample particles with light, and processing the light intensity signals respectively output from these detectors in the signal processing unit In the particle size distribution measuring apparatus configured to display the processing result on the display screen,
As the member constituting the signal processing unit, a member whose time constant of the signal processing unit is shorter than the time required for one sample particle to pass through the sample cell is used, and in the signal processing unit, the plurality of detectors When the particle size distribution calculation is performed each time the light intensity signal from is input, the light intensity signal of the excessive particles contained in the sample particles is measured in pulses, and the content of the excessive particles is grasped by counting the pulses. In addition, by using a continuous light intensity signal for calculation of sample particles other than oversized particles, particle size distribution calculation is performed to obtain the particle size distribution of the sample particles, and the obtained particle size distribution is the signal. A particle size distribution measuring apparatus configured to display on a display screen of a display unit of a display operation unit attached to a processing unit.   When the particle size distribution obtained in the signal processing unit is displayed on the display screen, the maximum value of the frequency distribution of each particle is displayed on the display screen for a preset time. The particle size distribution measuring apparatus according to claim 1.   When displaying the particle size distribution obtained in the signal processing unit on the display screen, the past particle size distribution is overlaid and displayed on the display screen a predetermined number of times. 2. The particle size distribution measuring apparatus according to 1.

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