JP4153987B2 - Particle size distribution measuring device - Google Patents

Description

  The present invention relates to a particle size distribution measuring apparatus for measuring the particle size distribution of particles such as a granular sample.

  Particle measurement technology is indispensable for determining and evaluating the performance of powders in a wide range of fields such as medicine, food, ceramics, cosmetics, paints, and pigments, and its importance is increasing day by day. Yes. One of the methods for measuring the particle size distribution of such a granular material is a laser diffraction / scattering particle size distribution measuring apparatus. For example, in Patent Document 1, a granular material as a sample is distributed and diffused in a dispersion medium to form a suspension, and this suspension is supplied to the flow cell. In this state, the flow cell is irradiated with laser light. Then, the laser light scattered by the particles in the suspension is detected by a detector, and the resulting diffraction and / or the intensity of the scattered light is processed based on the Franhofer diffraction or Mie scattering theory, The particle diameter is determined.

  In order to supply the suspension to such a flow cell, a circulation channel for circulating the suspension is formed, and in this circulation channel, there is a circulation bath in which a sample is dispersed in a dispersion medium. A circulation pump is interposed, and the dispersion medium sucked up from the dispersion medium tank is injected into the circulation bus through the dispersion medium supply system.

The circulation bath is equipped with a water level sensor that detects the full water level and drought level in order to prevent suspension overflow and abnormal liquid shortage. The state is ensured.
JP 2000-155088 A

  By the way, in order to appropriately determine the particle diameter of the sample, it is important to accurately control the concentration of the suspension. In adjusting the concentration of the suspension, the above-mentioned Patent Document 1 irradiates the flow cell inspection light in a state where the suspension is circulated in the circulation flow path, and the ratio between the light source amount of the inspection light and the transmitted light amount. That is, the concentration is determined based on the transmittance. For example, when it is determined that the concentration is high, the suspension is drained from the circulation channel by an appropriate amount, and then the water level sensor detects that the circulation bus is full. The procedure of supplying the dispersion medium via the dispersion medium supply system, circulating the suspension through the circulation channel again in this state, and determining the concentration by irradiating the inspection light is performed while repeating drainage and full water injection. I am doing so. For this reason, there is a problem that adjustment by subtle injection or the like is difficult, accurate concentration adjustment is difficult, and as a result, high measurement accuracy and reproducibility cannot be obtained in particle size distribution measurement.

  The present invention has been made paying attention to such a problem, and is a particle size distribution measuring device having a circulation structure that is useful for efficiently and automatically adjusting the concentration of powder particles in a dispersion medium. The purpose is to provide.

  In order to achieve the above object, the present invention takes the following measures.

That is, the present invention comprises a general configuration as this kind of particle size distribution measuring apparatus, a liquid level detecting means for detecting the liquid level of the suspension in the circulation bath at at least a number of points, Control means for controlling the injection of the dispersion medium and / or drainage of the suspension based on the detection signal of the level detection means, and the control means provides information on the concentration of particles contained in the suspension. A concentration information acquisition unit that acquires the concentration of particles contained in the suspension based on the acquired concentration information, a first determination unit that determines whether the concentration of particles contained in the suspension is a predetermined concentration, A first calculation unit that calculates the injection amount of the dispersion medium required when it is determined that the determination unit is dark, and driving of equipment necessary for injection of the dispersion medium based on the calculated value of the first calculation unit Drive unit The features.
Further, the present invention comprises a general configuration as this kind of particle size distribution measuring device, a liquid level detecting means for detecting the liquid level of the suspension in the circulation bath at least at a number of points, and Control means for controlling injection of the dispersion medium and / or drainage of the suspension based on a detection signal of the liquid level detection means, and the control means relates to the concentration of particles contained in the suspension. A concentration information acquisition unit that acquires information from the transmittance of inspection light, a first determination unit that determines whether or not the concentration of particles contained in the suspension is a predetermined concentration based on the acquired concentration information, and When the first determination unit determines that the concentration is high, the first calculation unit that calculates the injection amount of the dispersion medium that is necessary, and the injection level and the liquid level detected by the liquid level detection means are filled with water. Judge whether or not A second determination unit, a second calculation unit that calculates a drainage amount of the suspension and an injection amount of the dispersion medium that are necessary when it is determined that the water is full by the injection, the first calculation unit and / or the second calculation unit And a driving unit that drives devices necessary for injecting the dispersion medium and / or draining the suspension based on the calculated values of the two calculating units .

  Since it is possible to detect an intermediate liquid level, it is useful for fine adjustment of the dispersion medium injection and suspension drainage to adjust the concentration of the suspension. It becomes possible to adjust the liquid level of the circulation bath more accurately.

  The liquid level detection means may be configured using a plurality of liquid level sensors, or may be configured by a single liquid level sensor capable of multipoint detection or continuous detection.

  Specific embodiments of the liquid level detection means include a function that can detect full water, drought, and one or more points between them, and a predetermined range from full water to drought can be detected intermittently or continuously. The thing etc. which have a function are mentioned.

  In order to enable automatic adjustment of the concentration of the suspension, the control means acquires a concentration information acquisition unit that acquires information on the concentration of particles contained in the suspension from the transmittance of inspection light, and the acquired concentration A first determination unit that determines whether or not the concentration of the particles contained in the suspension is a predetermined concentration based on the information, and an injection amount of the dispersion medium that is necessary when the first determination unit determines that the concentration is high It is desirable to include a first calculation unit that calculates and a drive unit that drives a device necessary for injecting the dispersion medium based on the calculated value of the first calculation unit.

  In order to allow the suspension concentration to be automatically adjusted without being limited by the capacity of the circulation bath, the control means obtains information on the concentration of the particles contained in the suspension from the inspection light transmittance, etc. An information acquisition unit, a first determination unit that determines whether or not the concentration of particles contained in the suspension is a predetermined concentration based on the acquired concentration information, and when the first determination unit determines that the concentration is high A first calculating unit for calculating a required injection amount of the dispersion medium, and a second determination unit for determining whether or not the injection is full based on the injection amount and the liquid level detected by the liquid level detection means. And a second calculation unit that calculates a drainage amount of the suspension and an injection amount of the dispersion medium that are necessary when it is determined that the water will be full by the injection, and a calculation by the first calculation unit and / or the second calculation unit. Based on the value of the equipment required for injecting the dispersion medium and / or draining the suspension It is preferable that a driving unit that performs dynamic.

  In these, it is appropriate that the control means further includes a requesting unit that requests the introduction of the sample when it is determined that the first determining unit is thin.

  The present invention can finely and accurately adjust the liquid level of the circulation bath through the above-described configuration. For example, when applied to concentration adjustment, the suspension is appropriately diluted. It is possible to control the concentration to an appropriate level and thus to measure the particle size distribution with high reproducibility with high measurement accuracy.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram schematically showing a configuration of a light scattering particle size distribution measuring apparatus according to an embodiment of the present invention. This particle size distribution measuring apparatus connects the circulation bath 11 and the flow cell 12 via the circulation channel 13 so as to circulate the suspension 1a in which the particles of the particulate sample x are dispersed in the dispersion medium 3a. The suspension circulation system 1 and the suspension 1a flowing in the flow cell 12 are irradiated with laser light 2a as inspection light, and the granular material in the suspension 1a based on the diffraction and / or scattered light. An optical measurement system 2 for measuring the particle size distribution of the sample x, a dispersion medium supply system 3 for supplying the dispersion medium 3a to the suspension circulation system 1, and a drain port provided in a part of the circulation channel 1 14 and a suspension drainage system 4 for draining the suspension 1a.

  In the suspension circulation system 1, the circulation bath 11 mixes a granular material sample x (or slurry) that is an input measurement sample and a dispersion medium 3 a (for example, pure water or alcohol) that disperses the powder sample. In the suspension 1a, the stirring blade 15 that can be driven by the stirring motor 15a is immersed in the intermediate liquid tank part 11c between the upper liquid tank part 11a and the lower liquid tank part 11b, and also functions as a drainage pump. A centrifugal circulation pump 16 that also serves as the above is liquid-tightly attached to the bottom of the circulation bus 11 and can be driven by a circulation motor 16a. In the circulation bath 11, liquid level detection means 10 (see FIG. 2) for detecting the liquid level of the suspension 1a is provided. Then, the outlet of the circulation pump 16 attached to the circulation bus 11 is connected to the flow cell 12 via an outgoing pipe 13a that forms a part of the circulation channel 13, and the outlet of the flow cell 12 is connected to a part of the circulation channel 13. The circulation bus 11 is connected via a return pipe 13b.

  The flow cell 12 is arranged in the sample chamber A, and allows the suspension 1a introduced from the outside to flow out in a liquid-tight manner between a pair of translucent transparent plates. The plate is irradiated with laser light 2a.

  The forward piping 13 a has an ultrasonic transducer 18 that generates ultrasonic waves in the middle, and prevents aggregation of powder particles in the suspension 1 a toward the flow cell 12.

  The return pipe 13 b is connected to the intermediate liquid tank section 11 c in the circulation bus 11 so that the circulated suspension 1 a is refluxed to the circulation bus 11.

  On the other hand, as shown in FIG. 1, the optical system measurement system 2 includes a laser light source 21, a light projection lens 22, a narrow-angle scattered light detector 23, and a wide-angle scattered light so as to surround a sample chamber A containing a flow cell 12. The detector 24 is arranged, and the signal processing unit 25 and the arithmetic processing unit 26 that process signals output from the narrow-angle scattered light detector 23 and the wide-angle scattered light detector 24 are configured.

  The laser light source 21 is provided at the facing position of the flow cell 12, and emits parallel laser light 2a. The light projection lens 22 is provided between the laser light source 21 and the flow cell 12, and appropriately collects the laser light 2 a emitted from the laser light source 21 to irradiate the suspension 1 a in the flow cell 12.

  The narrow-angle scattered light detector 23 is disposed at a position that does not directly face the flow cell 12, that is, a position where the laser light 2a that passes through the flow cell 12 and is bent by the movable mirror 23a is condensed and focused. The narrow-angle scattered light detector 23 is formed by concentrically arranging a plurality of photosensors having ring-shaped or semi-ring-shaped light receiving surfaces having different radii around the optical axis of the condenser lens 22. Of the condensed laser light 2x diffracted or scattered by the inner particles, light scattered / diffracted at a relatively small angle is received at each scattering angle, and the light intensity thereof is measured. That is, the photosensor disposed relatively on the outer peripheral side receives light having a larger scattering angle, and the photosensor disposed on the inner peripheral side receives light having a smaller scattering angle. In general, the smaller the particle size, the greater the scattering, so the light intensity detected by the outer photosensor reflects the amount of particles with a smaller particle size, and the light intensity detected by the inner photosensor This reflects the amount of sample particles with a larger diameter.

  The wide-angle scattered light detector 24 is configured around the flow cell 12, and the light scattered / diffracted at a relatively large angle out of the condensed laser light 2 x diffracted or scattered by particles having a smaller particle diameter in the flow cell 12, Detect individually for each scattering angle. Specifically, the wide-angle scattered light detector 24 has a plurality of photosensors 24a provided at positions where the laser light 2x scattered at a different angle from the condensed laser light 2x incident on the narrow-angle scattered light detector 23 can be received. It consists of ˜24h, and the scattered light by the particles in the flow cell 12 is detected for each scattering angle in accordance with each arrangement angle. Photosensors 24a to 24e detect forward scattered light, and photosensors 24f to 24h detect backscattered light.

  The signal processing unit 25 sequentially takes in signals output from the narrow-angle scattered light detector 23 and the photosensors 24a to 24h, performs AD conversion, and inputs the signals to the arithmetic processing unit 26.

  In this embodiment, the arithmetic processing unit 26 uses a general-purpose computer function. As shown in FIG. 3, the arithmetic processing unit 26 includes a CPU 26a, a memory 26b, an input / output interface 26c, and a user interface 26d. The output of the narrow-angle scattered light detector 23 and the photosensors 24a to 24h (digital data regarding the light intensity) converted into digital signals is processed based on Fraunhofer diffraction theory and Mie scattering theory to obtain the particle size distribution in the particle group. And a program for performing a density check described later based on the transmitted light amount and the irradiated light amount are stored. The CPU 26a reads out these programs as appropriate, performs predetermined calculations and processing, stores the calculation results in the memory 26b, or displays them on a display or the like constituting a part of the user interface 26d. In this embodiment, by detecting diffracted light and scattered light in a wide range as described above, the particle size distribution in the particle group is obtained all at once from a relatively large particle size to a very small particle size. Make it possible.

  In order to secure a wider measurement range from large particles to fine particles, not only the laser beam 2a but also LED beams 2z having different wavelengths as shown in FIG. 1 can be used in combination. For this purpose, this apparatus is provided with an LED light source 21z, a light projection lens 22z, and a light receiver 23z corresponding to the laser light source 21, the light projection lens 22, and the narrow-angle scattered light detector 23. The photosensors 24d and 24e are also used to receive the scattered light of the LED light 2z.

  On the other hand, the dispersion medium supply system 3 includes a dispersion medium storage tank 31, a dispersion medium supply pipe 32 having one end immersed in the dispersion medium storage tank 31 and the other end connected to the suspension circulation system 1, and the dispersion medium. An injection pump 33 interposed in the medium supply pipe 32 is provided. By driving the injection pump 33, the dispersion medium 3 a is sucked up from the dispersion medium storage tank 31 and supplied to the suspension circulation system 1. I have to.

  The suspension drainage system 4 is connected to a circulation flow path 13 constituting the suspension circulation system 1 via an electromagnetic switching valve 17 and circulates through the suspension drainage system 4 at a closed position. Disconnected from the channel 13, one end of the suspension drainage system 4 is connected to the circulation channel 13 at the open position, and the suspension 1 a in the circulation channel 13 is discharged to the drain located on the other end side. The switching valve 17 is switched and driven by a solenoid.

  Next, the operation of this particle size distribution measuring apparatus will be described. First, a large amount of the powder sample x is put into the circulation bath 11. Next, the injection pump 33 of the dispersion medium supply system 3 is operated to start supplying (injecting) the dispersion medium into the circulation bus 11. At this time, the switching valve 17 is set to the circulation mode.

  When a predetermined amount of the dispersion medium 3a is supplied in the circulation bus 11 and the circulation flow path 13, the injection pump 33 of the dispersion medium supply system 3 stops based on the output signal S of the liquid level detection means 10, and the dispersion medium 3a. Supply stops.

  Thereafter, by the operation for starting the operation of the dispersion processing, the circulation motor 16a is activated, the circulation pump 16 is activated, and the ultrasonic transducer 18 is activated. As a result, the suspension 1a mixed with the particulate sample x is repeatedly circulated such that it flows through the circulation channel 13 from the circulation bath 11, passes through the flow cell 12 and returns to the circulation bus 11 again.

  The concentration of the obtained suspension 1a is checked by irradiating the flow cell 12 with laser light 2a from the laser light source 21 of the measurement system 2 in a state of circulating in the circulation channel 7. This is performed based on the ratio between the light amount of the light source and the transmitted light amount detected at the center by the narrow-angle scattered light detector 23, that is, the transmittance. The program for checking the density is stored in the memory 26b as described above, and the CPU 26a reads and executes the program as the distributed processing starts. When the concentration of the suspension 1a is not a predetermined concentration, the suspension 1a flowing through the flow cell 12 is subjected to a concentration check again after being diluted by supplying the dispersion medium 3a and being concentrated by adding the powder sample x. When the concentration is suitable for measurement, particle size distribution measurement is performed. If the suspension 1a is already full or may become full by supply, the suspension 1a is drained through the suspension drainage system 4 in advance.

  In the above configuration, the present embodiment employs a multi-point detection type or continuous detection type liquid level sensor 100 in the liquid level detection means 10 shown in FIG. It is designed to detect continuously. The detection signal S of the liquid level sensor 100 is input to the control means 110, and the control means 110 controls the injection of the dispersion medium 3a and / or the drainage of the suspension 1a.

  The liquid level sensor 100 shown in the figure is a float type sensor using a reed relay. When the float 100b moves up and down along the guide rod 100a, a terminal (not shown) provided on the float 100b side extends in the axial direction on the guide rod 100a side. The liquid level is detected intermittently or continuously by contacting a multi-point detection terminal or a continuous detection terminal (not shown) provided along the line. Of course, various liquid level sensors can be used, which will be described later.

  In the present embodiment, the arithmetic processing means 26 serves as the control means 110, and the liquid level control program is stored in the memory 26b. The CPU 26a reads the program as appropriate, and the input / output interface 26c. The output signal S of the liquid level sensor 100 is input via the input, or the set value input by the operator is obtained via the user interface 26d, and predetermined arithmetic processing is performed. And these cooperate, density information acquisition part 111 shown in Drawing 4, the 1st judgment part 112, the 1st calculation part 113, the 2nd judgment part 114, the 2nd calculation part 115, and drive part 116 , And the request unit 117.

  The concentration information acquisition unit 111 acquires the concentration of the particles contained in the suspension 1a from the transmittance of the laser light 2a. The concentration information acquisition unit 111 simply acquires the calculation result of the above-described concentration check program in addition to the predetermined calculation. Including just what comes. The acquired density information is not necessarily the value of the density itself as in this embodiment, and may be a parameter proportional to the density.

  The first determination unit 112 determines whether the concentration of particles contained in the suspension 1a is a predetermined concentration based on the acquired concentration. Although the predetermined density is stored in advance as a default value, it is of course possible that the operator gives a set value.

  The first calculation unit 113 calculates the injection amount of the dispersion medium 3a required when the first determination unit 112 determines that the concentration is high. The density difference and the required injection amount are stored in advance in association with mathematical formulas or tables.

  The second determination unit 114 determines whether or not the injection is full based on the injection amount and the liquid level indicated by the detection signal S of the liquid level sensor 100. The liquid level and the injectable amount up to full water are stored in association with each other in advance using mathematical formulas, tables, or the like as necessary. The second determination unit 114 makes the determination prior to the first calculation unit 113 calculating the injection amount.

  The second calculation unit 115 calculates the amount of the drainage of the suspension 1a and the amount of injection of the dispersion medium 3a necessary to achieve the required concentration when the second determination unit 114 determines that the water will be filled by the injection. To do.

  The driving unit 116 drives devices necessary for injecting the dispersion medium 3a and / or draining the suspension 1a based on the calculated values of the first calculating unit 113 and / or the second calculating unit 115. In this embodiment, as shown in FIG. 2, the injection pump 33 is driven ON / OFF to inject the dispersion medium 3a, and the switching valve 17 is driven to open and close to drain the suspension 1a. In this case, the drive unit 116 may directly monitor and control the discharge amount of the injection pump 33 based on the calculated injection amount, or may determine the target liquid level according to the injection amount and detect the detection signal S of the liquid level sensor 100. Based on the above, ON / OFF drive may be performed to stop the infusion pump 33 when the target level is reached. When the dispersion medium 3 is preloaded like tap water, an electromagnetic valve is generally used, and an electromagnetic valve is also used as the switching valve 17 for discharging the suspension 1a. In these cases, Alternatively, the target liquid level may be determined according to the injection amount, and the opening / closing control for closing the valve when the target level is reached based on the detection signal S of the liquid level sensor 100 may be performed.

  The requesting unit 117 requests the input of the granular material sample x when the first determining unit 112 determines that it is thin, and notifies the operator by text, voice, or the like via the user interface 26d as necessary. . It is more preferable not only to request the input but to determine and request the required input amount.

  FIG. 5 is a flowchart showing an outline of a program executed by the control means 110.

  When density adjustment is started (S1), the density is first acquired (S2), and it is determined whether or not the density is appropriate (predetermined density) (S3). When it is determined that the concentration is high, the injection amount of the dispersion medium 3 necessary to obtain an appropriate concentration is calculated (S4), and whether or not the circulation bath 11 exceeds the full water amount by injection of the calculated injection amount is determined. Judgment is made (S5). If it is determined that it does not exceed, the injection amount is injected (S6), and if it is determined that it exceeds, the optimum discharge amount of the suspension 1 and the injection amount of the dispersion medium 3 are set to obtain an appropriate concentration. Calculate again (S7). Then, discharge and injection are performed based on the calculated amount (S8, S9). On the other hand, if it is determined in step S3 that the sample is thin, a message prompting sample introduction is displayed or the like to request the introduction of the powder sample x (S10). Thereafter, the operator waits for the sample to be loaded (S12), but when the operator inputs that the measurement is to be continued, the concentration adjustment process ends (S14). After Steps S6, S9, and S12, the suspension 1a is homogenized by circulation and stirring (S13), and the process returns to Step S2 again.

  In addition, when not considering whether the circulation bus 11 becomes full, the 2nd judgment part 114, the 2nd calculation part 115, and step S5-S8 are unnecessary.

  As described above, the present embodiment is distributed based on the liquid level detecting means 10 for detecting the liquid level of the suspension 1a in the circulation bath 11 at at least a number of points and the detection signal S of the liquid level detecting means 10. A control means 110 for controlling the injection of the medium 3a and / or the drainage of the suspension 1a is provided.

  Thus, since this embodiment can detect an intermediate liquid level, the injection of the dispersion medium 3a and the drainage of the suspension 1a can be controlled more finely, and the concentration adjustment of the suspension 1a can be performed. It is possible to more accurately adjust the liquid level of the circulation bath 11 that is useful for the above.

  In particular, since one liquid level sensor 100 capable of multi-point detection or continuous detection is adopted as the liquid level detection means 10, the structure can be simplified, the size can be reduced, and a configuration suitable for fine adjustment can be realized. Can do.

  In addition, the control means 110 is configured to automatically perform a series of controls such as concentration acquisition, concentration determination, calculation of the injection amount, and driving of the injection pump 33 and the switching valve 17, so that it searches for injection and drainage. However, it is not necessary to adjust the concentration, and it is possible to quickly shift to particle size distribution measurement by quickly adjusting the concentration by dilution.

  In particular, the control means 110 makes a determination in advance even when the circulation bus 11 overflows due to the injection, and drains the waste water, so that dilution can be performed as little as possible. It can be effective.

  Furthermore, since the control means 110 requests the input of the granular material sample x when it is determined that the concentration is low, the operator needs to promptly respond to the request to increase the concentration. Can be handled efficiently.

  The specific configuration of each part is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

  For example, the liquid level detecting means can be constructed at low cost by using a plurality of liquid level sensors 200 as shown in FIG. 6, or the difference in light reflectance and refraction as shown in FIG. By using the non-contact sensor 300 such as an optical type, a conductive type, a capacitance type, and an ultrasonic type using a difference in angle, it is effectively immersed in the circulation bath 11 and hindering stirring. It can be avoided.

The system diagram which shows the outline | summary of the particle diameter distribution measuring apparatus which concerns on one Embodiment of this invention. The figure which shows the structure of the liquid level detection means in the embodiment. Functional explanatory drawing of the arithmetic processing unit used in the embodiment. The figure which shows the structure of the control means in the same embodiment. 6 is a flowchart showing a density adjustment procedure performed in the embodiment. The figure which shows other embodiment of this invention. The figure which shows other embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS S ... Detection signal x ... Granule 1 ... Suspension circulation system 1a ... Suspension 2 ... Optical side fixed system 3 ... Dispersion medium supply system 3a ... Dispersion medium 4 ... Suspension drainage system 11 ... Circulation bus 12 ... Flow cell 13 ... Circulating flow path 10 ... Liquid level detection means 100, 200, 300 ... Liquid level sensor 110 ... Control means 111 ... Concentration information acquisition part 112 ... First judgment part 113 ... First calculation part 114 ... Second Determination unit 115 ... second calculation unit 116 ... drive unit 117 ... request unit

Claims (5)

A suspension circulation system in which a circulation bath and a flow cell are connected via a circulation channel to circulate a suspension in which particles are dispersed in a dispersion medium, and an inspection light is supplied to the suspension flowing in the flow cell. An optical measurement system that measures the particle size distribution of the sample in the suspension based on diffraction and / or scattered light, a dispersion medium supply system that supplies a dispersion medium to the suspension circulation system, In what comprises a suspension drainage system that drains suspension from a drain outlet provided in the circulation channel,
Liquid level detection means for detecting the liquid level of the suspension in the circulation bath at at least a number of points, and injection of the dispersion medium and / or drainage of the suspension based on detection signals of the liquid level detection means Control means to control,
The control means obtains information on the concentration of particles contained in the suspension from the inspection light transmittance and the like, and the concentration of particles contained in the suspension is predetermined based on the obtained concentration information. A first determination unit that determines whether the concentration is a concentration; a first calculation unit that calculates an injection amount of a dispersion medium that is required when the first determination unit determines that the concentration is high; and the first calculation unit A particle size distribution measuring apparatus comprising: a drive unit that drives a device necessary for injecting the dispersion medium based on the calculated value of A suspension circulation system in which a circulation bath and a flow cell are connected via a circulation channel to circulate a suspension in which particles are dispersed in a dispersion medium, and an inspection light is supplied to the suspension flowing in the flow cell. An optical measurement system that measures the particle size distribution of the sample in the suspension based on diffraction and / or scattered light, a dispersion medium supply system that supplies a dispersion medium to the suspension circulation system, In what comprises a suspension drainage system that drains suspension from a drain outlet provided in the circulation channel,
Liquid level detection means for detecting the liquid level of the suspension in the circulation bath at at least a number of points, and injection of the dispersion medium and / or drainage of the suspension based on detection signals of the liquid level detection means Control means to control,
The control means obtains information on the concentration of particles contained in the suspension from the inspection light transmittance and the like, and the concentration of particles contained in the suspension is predetermined based on the obtained concentration information. A first determination unit that determines whether the concentration is a concentration; a first calculation unit that calculates an injection amount of a dispersion medium required when the first determination unit determines that the concentration is high; the injection amount and the liquid A second determination unit that determines whether or not the water level is filled by injection from the liquid level detected by the level detection means, and the amount of the drainage of the suspension and the injection of the dispersion medium that are necessary when it is determined that the water level is full by the injection A second calculation unit for calculating the amount, and driving of equipment necessary for injecting the dispersion medium and / or draining the suspension based on the calculated values of the first calculation unit and / or the second calculation unit. A particle size distribution measuring device comprising: a drive unit for performing the operation. The particle size distribution measuring apparatus according to claim 1 or 2 , wherein the liquid level detecting means detects full water, drought, and one or more points therebetween. The particle size distribution measuring apparatus according to claim 1 or 2 , wherein the liquid level detection means detects a predetermined range from full water to drought intermittently or continuously. The particle size distribution measuring apparatus according to claim 1, 2, 3, or 4 , further comprising a requesting unit that requests the introduction of a sample when the control means determines that the first determining unit is thin.