JPH11230889A - Particle counter turbidity meter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a highly sensitive turbidimeter for measuring a turbidity of a range responsive to applications by grouping to a plurality of groups based on number of particles, and calculating number of detected particles at each group. SOLUTION: A comparison selector having a plurality of comparators 39 to 42 and a plurality of detecting levels 43 to 46 and a counted value output circuit of a logic circuit 47 for calculating number of particles of each particle size group from the output of the selector and a switch 48 for deciding an output of the circuit 47 are added to a rear stage of an amplifier 36. The circuit 47 calculates the number of the particles of the each group based on the outputs from the respective comparators. The levels 43 to 46 set arbitrary detecting levels and obtain outputs response to the detected number of the particles at respective detected level from the comparators, i.e., at the respective groups. The circuit 47 counts the individual numbers of the particles of the groups 1 to 4 by using the outputs. And, further, the counted value is output to the calculating circuit via the switch 48 to measure a turbidity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water quality meter used in a water purification plant or the like, and more particularly to a high-sensitivity turbidity meter for counting fine particles in water and measuring turbidity. The present invention relates to a signal processing method for measuring.

[0002]

2. Description of the Related Art A water quality meter used in a water purification plant or the like includes a turbidity meter for measuring and controlling the degree of turbidity of water.
The turbidity of water supply in conventional water treatment plants is 2 degrees (pp
m) It is required to manage the turbidity as follows, and the turbidity measurement method is defined as a surface scattered light method, a scattered light method, an integrating sphere method and the like. However, the demand for the safety of tap water is increasing year by year, and it cannot be met by the conventional management level. In particular, the problem of toxicity of microorganisms contained in tap water is significant, and in 1996, as a result of a mass infectious disease caused by a protozoa of cryptosporidium of several μm in Japan, filtered water was used as a provisional guideline of the Ministry of Health and Welfare. Turbidity was required to be controlled below 0.1 degrees. As the turbidity management standard was reduced to 1/20 of the conventional one, the sensitivity of the conventional turbidity meter became insufficient. Therefore, the development of a high-sensitivity turbidity meter based on a new principle was required. Have been.

A turbidity meter of a fine particle counter type used for measuring turbidity of ultrapure water or the like meets this requirement. This particle counter type turbidity meter employs a method of counting the number of particles in a fluid to be measured and converting the counted value into turbidity. Laser light is used as a light source to detect particles, and when this is irradiated on the fluid to be measured flowing in the measurement cell, the laser light collides with fine particles in the fluid and scatters. Light is captured as an optical pulse by an optical sensor, and the number of particles that have passed is counted from the number of changes.

Conventionally, in this turbidimeter of the particle counter type, a signal detected by an optical sensor is converted into an electric signal, and the presence or absence of a light pulse is detected by one comparator having a certain detection level. The value of this light pulse is measured as the concentration of fine particles per unit volume, and is converted into turbidity. At this time, the intensity of the scattered light or the interference light varies depending on the particle diameter according to the theory of Mie scattering. In general, those having a small particle diameter have low scattered light intensity, and those having a large particle diameter have high scattered light intensity.

In the case of a turbidimeter of the fine particle counter type, the size of the particle to be measured is about 0.1 μm to about several tens μm. Therefore, the detection level of the comparator is usually set to a level at which particles of 0.1 μm can be detected.

[0006]

On the other hand, the size of Cryptosporidium is said to be about 4 μm to 7 μm. In order to more reliably determine the presence or absence of Cryptosporidium in tap water, the turbidity within this range is determined. There is a demand for selective measurement. However, the conventional device has a problem that only one detection level can be set, and only the overall turbidity of particles of about 0.1 μm to about 10 μm in the fluid can be measured.

SUMMARY OF THE INVENTION An object of the present invention is to provide a high-sensitivity turbidity meter of a fine particle counter type capable of measuring the turbidity in a range according to the use such as the turbidity of the whole or a certain particle diameter group, eliminating the above-mentioned disadvantages. Is to provide.

[0008]

The feature of the present invention to achieve the above object is that a fluid to be measured is guided to a measuring cell, a laser beam is irradiated in the cell, and the fluid is scattered by particles in the fluid to be measured. A particle counter type turbidity that captures the scattered light or the interference light due to the scattered light and the irradiation light as a light pulse, calculates the number of particles by counting the light pulses, and calculates and outputs the number of particles or the converted turbidity. In other words, the apparatus includes a counting and identifying means for performing a plurality of grouping based on the size of the number of detectable particles and calculating the number of detected fine particles for each of the groups.

According to the above means, not only the overall turbidity in the fluid to be measured but also the turbidity can be output according to the particle diameter.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a diagram showing a configuration of a main part of the present invention.

A fluid 2 to be measured supplied from a sample water inlet 1
Is led to the lower part of the defoaming tank 7 through a pipe 3, a pressure reducing valve 4, a regulating valve 5, and a pipe 6. The defoaming tank 7 is composed of a short inner cylinder 8 and a long outer cylinder 9. The outer cylinder 9 further has an overflow port 11 for maintaining the height of the water surface 10 of the fluid to be measured at an upper portion of its outer peripheral surface. Further, at the lower part of the outer peripheral surface, an outlet 14 for sending out the fluid to be measured 2 to the detector 13 through the pipe 12
Are provided respectively.

The detector 13 has a transparent and cylindrical measuring cell 15 for guiding the fluid 2 to be measured and measuring its turbidity, and a laser having a built-in optical lens system for irradiating the measuring cell 15 with a laser beam. A unit 16 and a light receiving unit 17 for receiving the laser beam passing through the measuring cell 15 are arranged.

The fluid 2 to be measured having passed through the measuring cell 15 is discharged from the discharge port 19 through the pipe 18 under atmospheric pressure. The fluid 2 to be measured overflowing from the discharge port 19 and the overflow port 11 is drained out of the apparatus via a pipe 20 and a discharge port 21.

On the other hand, the laser unit 16 and the light receiving unit 17 in the detector 13 are electrically connected to the converter 22, respectively, to supply power and process detection signals. Further, the converter 22 performs a predetermined operation on the detection signal to obtain a turbidity value of the fluid to be measured, displays the turbidity value on a display device such as a liquid crystal display (not shown), and outputs an output signal 23 corresponding to the display value. The converter 22 is connected to a power source 2 from the outside.
4 supplies.

A lid 25 is fitted on the upper end of the defoaming tank 7, and a temperature sensor 26 such as a thermocouple is held on the lid 25. And transmits the temperature of the fluid 2 to be measured to the converter.

In this configuration, the fluid 2 to be measured guided to the inner cylinder 8 of the defoaming tank 7 contains many bubbles due to changes in temperature and pressure, and these bubbles are opened to the atmosphere. Dissipated from the water surface 10 into the atmosphere. A fluid to be measured having few air bubbles is collected between the inner cylinder 8 and the outer cylinder 9 and sent out from the outlet 14 to the detector 13, so that measurement with less influence of the air bubbles can be performed. At this time, the fluid 2 to be measured flowing in the measurement cell 15
Is determined by the head difference ΔH between the water surface 10 and the discharge port 19 and the pipe resistance.

Next, the principle of measurement in the detector 13 will be described with reference to FIG.

The laser unit 16 is composed of a semiconductor laser 31 as a light source and a condenser lens 32, and is arranged so that the generated laser light 33 is focused in a measuring cell 15 made of quartz glass or the like. The measured fluid 2 flows in the measurement cell 15 in the direction of the arrow. The measured fluid 2 contains a large number of fine particles 34. These fine particles 34
Is irradiated with the laser light, a scattering phenomenon occurs and scattered light 35 is generated. The laser light 33 (transmitted light) and the scattered light 35 generate interference light behind the measurement cell 15. The interference light (shading of the transmitted light) is detected by the light receiving unit 17 including two light receiving elements, and differentially amplified by the amplifier 36. The presence or absence of a pulse in the interference light converted into the electric signal is determined by the comparator 37. The detection level 38 at this time is adjusted to the light intensity of the minimum detectable particle diameter. The output waveform is shown in FIG.

Each time the fine particles 34 shown in FIG. 2 pass one by one, a peak waveform 41 is output. In this example, since there is only one detection level 38 by the comparator 37, only particles having a certain particle diameter or more can be detected. Therefore, the turbidity of the required particle size group cannot be measured.
FIG. 4 shows an embodiment of the present invention which solves this problem.

In the embodiment of the present invention shown in FIG. 4, a plurality of comparators 39, 40, 4 are provided after the amplifier 36.
1, 42 and a plurality of detection levels 43, 44, 45, 4
6 are added, a logic circuit 47 for calculating the number of particles for each particle size group from the output thereof, and a count output circuit by a switch 48 for determining the output of the logic circuit 47. Here, the logic circuit 47 calculates the number of particles of each group based on four outputs from each comparator, and is configured based on an AND circuit.

Each detection level 43, 44, 45, 46
By setting an arbitrary detection level, an output corresponding to the number of detected particles can be obtained from each comparator for each detection level, that is, for each particle diameter group. The method of giving the particle size group is, for example, as follows.

Group 1: 0.1 μm to 0.5 μm Group 2: 0.6 μm to 3 μm Group 3: 4 μm to 8 μm Group 4: 9 μm To the above-described group assignment, the detection level of each comparator is: 0.1 μm, 0.6 μm, 4 μ respectively
The detection level at which particles of m and 9 μm or more can be detected is set. By doing so, each comparator performs an output corresponding to the number of particles larger than the set size, and using this output, the logic circuit 47 can count the number of individual particles of the four groups. By outputting the count value to an arithmetic circuit (not shown) via the switch 48, the turbidity can be measured.

FIG. 5 shows the state of the output waveform of FIG. Each of the detected peak signals has a different detection signal value depending on the size of the particle diameter. In the example of FIG. 5, the number of particles in Group 1 is one and the number of particles in Group 3 is two. I understand.

In the actual measurement, the turbidity of each group is required as a whole, but which output is to be used can be selected by the switch 48 as needed. Also, as shown in FIG. 6, by providing two output functions of the switch, two systems such as an output of a specific particle diameter group and an output of the whole particle or an output of two particle diameter groups are provided. Needless to say, turbidity can be output and displayed at the same time.

The number of particle size groups can be easily changed by increasing the required number of comparators of the comparison and selection circuit and setting different detection levels.

FIG. 7 shows another embodiment. In this example, the detection level of each comparator can be changed to an arbitrary level. In this configuration, by setting the variable detection levels 50 and 51, the range of the particle diameter group can be freely adjusted. Specifically, for example, if the variable detection level 50 is set to a level of 4 μm or more and the variable detection level 51 is set to a level of 7 μm or more, the logic circuit 47 counts the number of particles with a range of 4 μm to 7 μm as a specified range. It can be carried out.

When the number of particles having a certain level is measured, for example, when the target is determined in advance, the method of this embodiment realizes the design of the turbidimeter with fewer components. It is possible.

Further, by setting the levels of the variable detection levels 50 and 51 so as to approximate each other, it is also possible to selectively obtain the turbidity of only a specific particle diameter.

Further, in each embodiment of the present invention,
In the logic circuit 47, only the counting of the number of particles is performed. However, it is also possible to incorporate an arithmetic circuit and calculate the turbidity in the logic circuit 47.

[0031]

According to the present invention, it is possible to output not only the overall turbidity in the fluid but also the turbidity according to the particle size, and to know the particle size distribution of the turbidity in tap water. . This allows not only to accurately determine the presence or absence of harmful protozoa with a certain particle size, such as cryptosporidium,
It can greatly contribute to the safe supply of tap water.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a main part of an embodiment of the present invention.

FIG. 2 is a diagram illustrating the principle of signal detection in a conventional example.

FIG. 3 is an output waveform of signal detection according to a conventional example.

FIG. 4 is a configuration diagram showing a signal detection unit of the present invention.

FIG. 5 is an output waveform of signal detection according to the present invention.

FIG. 6 is a configuration diagram showing another example of the switch.

FIG. 7 is a configuration diagram showing another embodiment of the present invention.

[Explanation of symbols]

2 fluid to be measured, 15 measuring cell, 16 laser unit, 17 light receiving unit, 33 laser light, 35 scattered light, 36 amplifier, 37 comparator 1, 38 detection level 1, 39 to 42 Comparators 2-5, 43-4
6 ... Detection levels 2 to 5, 47 ... Logic circuit, 48 ... Switcher, 50,51 ... Variable detection level.

Continued on the front page (72) Inventor Shigeo Nishino 882 Mage, Oaza-shi, Hitachinaka-shi, Ibaraki Pref.

Claims (7)

[Claims] 1. A fluid to be measured is guided to a measuring cell, a laser beam is irradiated in the cell, and scattered light scattered by particles in the fluid to be measured or interference light by the scattered light and the irradiating light is converted into an optical pulse. And calculate the number of particles by counting light pulses, and calculate the number of particles or the converted turbidity.
A particle counter type turbidimeter for outputting, comprising count identification means for performing a plurality of grouping based on the size of the number of detectable particles and calculating the number of detected particles for each group. A turbidity meter with a fine particle counter. 2. A plurality of comparison / selection means according to claim 1, wherein said counting and identification means sets a detection level corresponding to a minimum diameter of particles to be detected, and detects particles having a diameter equal to or greater than the set particle diameter. And a particle diameter calculating means for calculating the number of particles by using an output obtained from the comparing and detecting means for each of the plurality of groups set, wherein a fine particle counter type turbidity meter is provided. . 3. A plurality of comparison / selection means according to claim 1, wherein said counting and identification means sets a detection level corresponding to a minimum diameter of the particles to be detected, and detects particles having a diameter equal to or greater than the set particle diameter. And, for each of the plurality of groups set, a particle diameter calculation for calculating the number of particles by using an output obtained from the comparison detection means, and calculating a turbidity based on the calculated number of particles. And a particle counter type turbidity meter. 4. The turbidity meter according to claim 2, wherein the detection level set by said comparison and selection means is variable. 5. The particle counter type turbidimeter according to claim 2, wherein said particle diameter calculating means calculates the total number of particles in a plurality of the set groups. 6. The method according to claim 3, wherein the particle diameter calculating means calculates the number of all particles in the plurality of groups and / or calculates turbidity based on the calculated number of particles. A particle counter type turbidimeter characterized by the above-mentioned. 7. The switching output means according to claim 5, wherein any two of the output of each of the plurality of groups and the output of the entire group of the particle diameter calculating means are selected and output simultaneously. A particle counter type turbidimeter characterized by the above-mentioned.