JPS6329232A - Measuring instrument for corpuscle in liquid - Google Patents

Abstract

PURPOSE:To improve particle detection efficiency and to measure accurate particle characteristics by forming the circulation flow of measuring liquid in a corpuscle measurement area by an in-liquid corpuscle measuring instrument using laser beam. CONSTITUTION:Sample liquid 16 is supplied from a liquid intake 1 and rotated at constant speed by the rotation of a stirrer 2 placed at the internal cylinder bottom part of a measurement cell 20. In such case, laser luminous flux 3 is made incident from an incident window 4 so that it is converged on a point 3a between the center of the cylinder and the center of the cylinder side wall. Scattered light from the corpuscles 17 in liquid which pass the convergence point 3a is received by a light receiving window 5 to form an image on a mask 7 through a convergent lens 6, and the image is converted by a photoelectric converter 8 into an electric signal and the particle size is calculated by a crest value analyzer 9 from the intensity of the scattered light and displayed a particle size display device 10. Thus, the particle detection efficiency is improved to measure accurate particle characteristics.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an in-liquid particulate measurement device, more specifically, a device for measuring particles in liquid, which irradiates a laser beam into a fluid and detects scattered light from particulates suspended in the liquid. This invention relates to an in-liquid particle measuring device that measures particle characteristics such as particle size and number of particles.

[Prior Art] Conventionally, a technique has been known in which the characteristics such as the particle size and number of particles in the measurement area can be determined by making light enter the measurement area and measuring the amount of transmitted light and scattering characteristics. ing.

For example, this technique is used to measure impurity particles r in pure water, but since the fine particles in pure water are small in diameter and exist only sparsely, it is difficult to determine 'A11. cormorant. Therefore, conventionally, in order to increase the scattering intensity from fine particles, the incident light beam from a laser light source is focused on a small area, a high-intensity measurement area is provided, and the scattered light from the particles passing through this area is collected. A method of receiving light is used.

In a particle measuring instrument that irradiates particles with laser light and analyzes scattered light from the particles, it is important how to form a measurement portion that allows particles -f to pass through. In other words, in the case of particle f- in gas, the gas containing particle f- is blown out from the nozzle and the outside is wrapped with clean gas to form the measurement area, or in the case of particle measurement in liquid, the liquid is held. A measurement cell is required to drain the water.

Since this measurement cell is irradiated with laser light, the incident and exit surfaces of the light beam and the receiving surface of the scattered light must be optically transparent, and the side that is scattered to the side perpendicular to the incident light side of the irradiated light must be optically transparent. A four-sided transmission cell is used to receive forward scattered light, and a two-sided transmission cell is used to receive forward scattered light that is scattered to the side opposite to the incident side of the irradiated light.

The particle detection region formed in the 1111 constant cell is often located near the focal point of the laser beam in order to increase the intensity of the light scattered from the particles.

That is, as shown in FIG. 2, in order to measure the scattered light from the fine particles 22 in the liquid that fall into the measurement cell 20,
The laser beam 23 is focused and incident. In that case, the vicinity 23a of the convergence point of the laser beam is used as the particle detection region, and the scattered light from this region is condensed by the condenser lens 24 to perform measurement.

On the other hand, as shown in FIG. 3, there is also a method of detecting all the particles passing through the cross section of the measured cell, in which a sheet-shaped laser beam 23' is made incident over the entire cross section of the cell.

[Problems to be solved by the invention: When producing smaller particles using the latter method, it is necessary to limit the width of the laser beam spread out in a sheet-like manner.
As a result, the cross-sectional area of the all+ constant cell becomes smaller, pressure loss increases, and it tends to become difficult to secure the liquid flow 4-. Therefore, as the particle diameter to be detected becomes smaller, it is thought that the former method of using a condensing point is increasingly used at the expense of detection efficiency. However, all of these methods measure particles in the liquid only once when the liquid passes through the measurement cell, and after the measurement, the liquid is searched out.

An object of the present invention is to provide a method for condensing a laser beam that enables the detection of minute particles while avoiding the transient nature of the sample liquid flow, thereby increasing particle-f detection efficiency in a liquid. Our goal is to provide a particle measuring device.

[Means for Solving the Problem] According to the present invention, in order to solve this problem, a configuration is adopted in which a circulating flow of the measurement liquid is formed in the particulate measurement region.

[For fl] In the present invention, a cylindrical measuring cell is provided which forms a circulating flow to maintain a constant velocity across the particulate measurement area. Inside this measurement cell, a stirring element is arranged which is magnetically coupled to a magnet connected to an external drive motor and rotates as the motor rotates, thereby forming the circulating flow.

There is an example of using a measurement cell and a stirrer in combination for light scattering measurement. It acts to reduce the difference in refractive index in order to weaken the difference in refractive index.

In order to improve heat diffusion when the temperature of the liquid is changed, a stirrer is used as a container to hold the liquid, and as in the present invention, a laminar circulation flow is generated in the measurement cell. to measure particles by forming a

[Example] Hereinafter, the present invention will be described in detail according to an example shown in the drawings.

FIG. 1 schematically shows an apparatus for measuring particulates suspended in a liquid. In the same figure, the reference numeral 20 indicates a measurement cell, which has a cylindrical shape, for example. A part of the measurement cell 20 includes a liquid bubble inlet 1 equipped with a valve 13 for introducing the sample liquid 16 into the measurement cell 20, and a liquid discharge port equipped with a valve 14 for discharging the sample liquid from inside the measurement cell to the outside. 15 is attached. Further, a stirring bar 2 for stirring the liquid is provided at the lower part of the measurement cell 20, as will be described later. This stirrer 2 is composed of a magnet and is magnetically driven from the outside.

Further, on the cylindrical circumferential surface of the measurement cell 20, there is an entrance window 4 that receives a laser beam 3 from a laser light source (not shown), an output window 11 that outputs the laser beam, and a light receiving window that receives scattered light from fine particles. 5 is placed. The 6th window is a quartz glass window, and a thin film coating is applied to the front and back surfaces so that it has low reflection characteristics against the wavelength of incident light.

A condensing lens 6 and a mask 7 are arranged behind the light receiving window 5, and a photoelectric converter 8 that receives scattered light and converts it into an electrical signal, as well as a pulse height analyzer 9 and a particle size indicator 10 connected thereto. will be provided.

In such a configuration, the sample liquid 16 is taken in from the droplet inlet 1 and rotated at a constant speed by two rotations of the JW stirrer placed at the cylindrical bottom of the measurement cell 20. At this time, the laser beam 3 is directed through the entrance window 4 so as to be focused at the midpoint 3a between the center of the cylinder and the side wall of the cylinder. Scattered light from fine particles 17 in the liquid passing through the condensing point 3a of the laser beam 3 is received through the light receiving window 5, and is imaged on the mask 7 by the condensing lens 6.
A photoelectric converter 8 converts the light into an electrical signal, a pulse height analyzer 9 calculates the particle diameter from the intensity of the scattered light, and displays it on a display 10. The mask 7 is provided to limit the size of the measuring portion in the light beam for detecting the passage of particles. The once focused laser beam 3 is emitted from the emission window 11 to the outside of the measurement cell 20 while diverging, and is absorbed by the optical trap 12. The valves 13 and 14 open when a droplet is added, replace the liquid in the cylindrical portion with the liquid flowing in from the droplet holder 1-11, and close after being discharged from the liquid outlet 1115.

In this embodiment, the stirrer 2 is formed of a magnet, rotates by magnetic drive from the outside, and generates a circulating flow in the liquid. In the present invention, the formation of this circulating flow is achieved by the following condition 1.
Perform with -.

The fine particles 17 in the liquid are interlocked with each other due to the action of the molecules of the liquid. Based on this Brownian interlock, it is known that the particle moves at time t<qz uniform distance #L, where L=fl and D=kT/3πηd, where D is the diffusion coefficient.

Here, k is Portzmann's constant, T is the temperature of the liquid, η is the viscosity coefficient of the liquid, d is the particle size of the fine particles, and π is the circular layer ratio.

In the particle detection area 3a, if the time required for one revolution calculated from the circumferential velocity caused by the circulating flow is the above-mentioned time t, a particle that has passed through the particle detection area once will deviate from this area by L after one revolution. It turns out. Therefore, if the average moving distance of the particles is made larger than the width of the detection area 7a limited by the mask 7 in FIG. If this setting is made, it is considered that particles that have passed through the detection area once will not return to this area a second time, considering only the effect of Brownian motion.

- On the other hand, if the circulation flow rate is increased, the flow inside the measurement cell will become turbulent, the liquid will be mixed by turbulent mixing, and new parts of particles can be detected, but the speed of particles passing through the particle detection area If the vectors are not uniform, the scattered light for the same particle will be different, making it unsuitable for measurement. Therefore, it is desirable that the circulating flow be laminar.

Under the conditions described in -1-, the liquid in the measurement cell is mixed appropriately by the rotational movement of the stirrer, and each time it passes through the measurement part, the particle force of a new liquid part is detected, which reduces the measurement time. The particle size/number W:I odor distribution obtained over time is incorporated and comes to accurately reflect the particle size/number density distribution of suspended fine particles in the entire liquid in the cylindrical portion.

In the above embodiments, the content of the invention is as follows: However, the present invention can also be used in a method for determining the particle diameter and molecular speed of particles using the optical f-correlation U.

The apparatus according to the present invention can be used, for example, to measure light scattering of fine particles in ultrapure water, and to measure photon correlation of polymer particles contained in paints, pigments, and the like.

[Effect] As explained above, according to the present invention, since a sheath liquid flow is formed in the particulate measurement area, particle detection efficiency is increased by avoiding the transient nature of the sample liquid. This results in an accurate measurement of particle characteristics +1.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the configuration of the measuring device of the present invention, and FIGS. 2 and 3 are explanatory diagrams explaining different measuring methods. 3...Laser beam 17...Fine particles 20...
Measuring cell patent applicant: Kowa Co., Ltd. (and 1 other person)

Claims (1)

[Scope of Claims] 1) In an in-liquid particulate measurement device that measures particle characteristics by irradiating a laser beam into a fluid and detecting scattered light from particulates suspended in the liquid, a measurement liquid is placed in a particulate measurement area. An in-liquid particle measuring device characterized by forming a circulating flow of. 2) The submerged microparticle device according to claim 1, wherein the circulating flow is laminar. 3) The in-liquid particulate measuring device according to claim 1 or 2, characterized in that the circulation flow rate is slowed down so that the particles are sufficiently displaced during one circulation.