JP3101776B2 - Turbidity measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a turbidity measuring device widely used for monitoring the environment of water bodies such as rivers and lakes, or for monitoring industrial wastewater.

[0002]

2. Description of the Related Art The turbidity measuring device continuously measures the turbidity of water bodies such as rivers and lakes to monitor the environment of the water bodies, and continuously measures the turbidity of industrial wastewater to monitor the wastewater. It is being done.

A measuring device (turbidity meter) used for continuous measurement of such turbidity includes a surface scattered light system, a transmitted scattered light system, an integrating sphere system, and the like. However, the problem with any type of apparatus is how to reduce the influence of contamination during continuous measurement.

[0004]

That is, in the measuring device of the surface scattered light method, since the measuring cell is not directly immersed in the test water, the turbidity is measured continuously and stably for a long time in the point that the influence of dirt is small. However, it is necessary to pump the water sample with a pump and the installation conditions are severe.

On the other hand, in a measuring device such as a transmission scattered light system in which a measuring cell is immersed directly in a test water, the cell window is contaminated, so that the influence of the cell window must be removed by correction. In many cases, the correction of the stain on the cell window is insufficient, and it has been difficult to stably measure the turbidity over a long period of time. For this reason, in the case of a measuring device of the type in which the measuring cell is immersed in the test water, the cell window has to be cleaned in a certain appropriate period.

It is an object of the present invention to provide a method for measuring turbidity stably over a long period of time by sufficiently removing the influence of dirt on a cell window even if a measuring cell is directly immersed in a sample. It is an object of the present invention to provide a turbidity measuring device that can be used.

[0007]

The above objects are achieved by the turbidity measuring device according to the present invention. A measurement light source that irradiates light for turbidity measurement during the test water, and receives scattered light at two points on an irradiation direction line of the irradiated measurement light, and is arranged at intervals in the irradiation direction. In a turbidity measuring apparatus, a measuring cell provided with two light receiving units and a measuring unit for detecting the turbidity of the test water from a difference between light receiving outputs of scattered light received by the two light receiving units, Irradiating light for cell correction during the test and causing the transmitted light to be received by the two light receiving units; and providing a correction light source equidistant from the two light receiving units and receiving light by the two light receiving units. A correction unit that detects a stain on the measurement cell from the difference in the received light output of the transmitted light and returns a correction output for eliminating the difference in the received light output of the transmitted light to the two light receiving units. Turbidity measuring device.

[0008]

FIG. 1 is a schematic diagram showing an entire measuring cell in one embodiment of the turbidity measuring apparatus of the present invention, and FIG. 2 is a block diagram showing a signal processing section of the measuring cell. The turbidity measuring device of the present invention includes a measuring cell 20, which has a lower half with a step at a lower end to be immersed in a sample 21. Cell 20
A concave portion 22 into which the water sample 21 enters is provided in the lower half portion, and the concave portion 22 is a hole whose lower surface and a pair of opposing side surfaces are open to the outside. A cell window 3 made of transparent glass is adhered to the inner surface of the recess 22 to separate the inside of the lower half of the cell 20 from the recess 22.

Inside the cell window 3 at the upper end of the concave portion 22 of the cell 20, a light source 1 for irradiating the turbidity measurement light downward in the water sample 21 is provided. Inside the cell window 3 on the side wall, two photocells 4 and 5 that receive the scattered light of the measurement light irradiated into the test water 21 are provided at intervals in the vertical direction. The photocells 4 and 5 have built-in preamplifiers (not shown). A light source 2 for irradiating light for cell correction in the water sample 21 is provided inside the cell window 3 on the shorter side wall of the recess 22 opposite to the photocells 4 and 5. Light source 2
Are arranged at positions equidistant from the photocells 4 and 5.
The light source 1 for turbidity measurement and the light source 2 for cell correction are shown in FIG.
As shown in FIG.

An example of the dimensions of each part shown in FIG. 1 of the cell 20 in this embodiment is as follows.
L: 300 mm, L _{1 for} lower half: 150 mm, L
_{2: 100mm, h 1: 50mm} , h 2: 50mm, w
_{1: 35mm, w 2: 30mm} , w 3: is a 20mm.

Further, a signal processing section shown in FIG. 2 is provided in the cell 20. This signal processing unit includes photocells 4, 5,
And a turbidity measuring section comprising a turbidity measuring differential amplifier 8 connected to the gate 6, and a gate 7 connected to the photocells 4, 5 and a correction output connected to the gate 7. And a correction unit including the differential amplifier 9 described above.

The light 10 radiated from the turbidity measuring light source 1 into the water sample 21 travels straight through the water sample 21 and is scattered one after another on the irradiation direction line. ,
The scattered light of the points a and b) is incident on the photocells 4 and 5, respectively, and is received. The light receiving signal is amplified by the preamplifiers of the photocells 4 and 5, and then input to the differential amplifier 8 through the gate 6 opened in synchronization with the lighting of the light source 1.

While the light 10 travels through the water sample 21 from the point A to the point B, the intensity of the light 10 is attenuated by an amount proportional to the turbidity of the water sample 21. The intensity of the scattered light becomes smaller than the intensity of the scattered light by the amount proportional to the turbidity, and the difference between the light receiving outputs of the photocells 4 and 5 becomes an amount proportional to the turbidity of the water sample 21. Therefore, the photocells 4, 5,
The turbidity of the test water 21 is determined and the turbidity is measured by calculating the difference between the light receiving outputs from the sample and amplifying it to an appropriate magnification with respect to the reference value.

However, there is no problem if the cell windows 3 at the photocells 4 and 5 are similarly contaminated. However, if one of the photocells, for example, the cell window 3 at the photocell 4 is contaminated, the photocell 4 is not contaminated. Since the received light intensity is reduced by the amount of dirt on the cell window 3, the received light output is also reduced by that amount, and the turbidity obtained from the difference between the received light outputs of the photocells 4 and 5 becomes smaller than actual. Conversely, if the cell window 3 at the location of the photocell 5 is dirty, the turbidity obtained will be larger than it actually is.

Therefore, the light 11 is irradiated into the water sample 21 by the correction light source 2 which is alternately turned on with the measurement light source 1, and a correction output is generated based on the difference in the light reception output of the light 11 to generate the photocell 4. And 5 is fed back to the preamplifier to correct the stain on the cell window 3. Now, the description will be given on the assumption that the cell window 3 at the photocell 4 is dirty.

The light 1 from the light source 2 for correction enters the water sample 21.
When the light 1 is irradiated, the transmitted light of the light 11 having undergone the same amount of intensity attenuation reaches the photocells 4 and 5 and is received because the light source 2 is equidistant from the photocells 4 and 5. The received light signal is
In the same manner as before, after amplification by the preamplifiers of the photocells 4 and 5, the gate 7 opened in synchronization with the lighting of the light source 2
And input to the differential amplifier 9.

At this time, since the cell window 3 at the location of the photocell 4 is dirty, the photocell 4 has a lower light receiving intensity and a lower light receiving output by an amount corresponding to the contamination of the cell window 3. Therefore, when the difference between the light receiving outputs from the photocells 4 and 5 is calculated by the differential amplifier 9, the contamination of the cell window 3 of the photocell 4 is detected, and the differential amplifier 10 determines the difference between the light receiving outputs with an appropriate magnification with respect to the reference value. A correction output for eliminating the difference between the light receiving outputs of the photocells 4 and 5 is generated. Then, the corrected output is fed back to the preamplifiers of the photocells 4 and 5, and the light output of one or both of the photocells 4 and 5 is corrected so that the difference between the light output of the photocells 4 and 5 becomes zero.

According to such feedback, the photocells 4, 5
Since the influence of the contamination of the cell window 3 at the photocell 4 on the difference between the light receiving outputs of
When the turbidity of the water sample 21 is measured by the light 10 radiated from the light source 1 over a half cycle of the lighting cycle of 2,
Accurate turbidity is always obtained without affecting the contamination of the cell windows 3 at the photocells 4 and 5.

According to the turbidity measuring device of the present invention, as described above, even if the measuring cell 20 is directly immersed in the water sample 21, the influence of the stain on the cell window 3 is sufficiently corrected to be removed, The turbidity can be measured stably over the entire range of the measurement light.
Photocells 4 and 5 of the two scattered lights on the irradiation direction line 0
Since the turbidity of the water sample 21 is obtained based on the difference in the light receiving output due to the above, there is also a merit that the error of the deterioration of the light source 1 is small.

[0020]

As described above, according to the present invention, a measuring light source for irradiating turbidity measuring light into a test water and two scattered lights on the irradiation direction line of the irradiated measuring light are provided. The measuring cell is provided with two light receiving units that receive light and are arranged at intervals in the irradiation direction, and a measuring unit that detects turbidity of the test water from a difference between light receiving outputs of scattered light received by the two light receiving units. In the turbidity measurement device, the measurement cell is provided with a correction light source equidistant from the two light receiving units so that the light for cell contamination correction is irradiated in the test water and the transmitted light is received by the two light receiving units. A correction unit is provided for detecting contamination of the measurement cell from the difference between the received light outputs of the transmitted light received by the two light receiving units and returning a correction output for eliminating the difference between the received light outputs of the transmitted light to the two light receiving units. Therefore, even if the measurement cell is immersed directly in the test water, the effects of cell contamination are sufficiently corrected. More removed, it can be measured stably turbidity over a long period of time.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an entire measuring cell in one embodiment of a turbidity measuring device of the present invention.

FIG. 2 is a configuration diagram illustrating a signal processing unit of the measurement cell of FIG. 1;

FIG. 3 is a waveform diagram showing a lighting cycle of a measurement light source and a correction light source of the measurement cell of FIG.

[Explanation of symbols]

 Reference Signs List 1 light source for measurement 2 light source for correction 3 cell window 4, 5 photocell 6, 7 gate 8, 9 differential amplifier 10 light for measurement 11 light for correction 20 measurement cell 21 water test

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) G01N 21/00-21/61 JICST file (JOIS)

Claims (1)

(57) [Claims] 1. A measuring light source for irradiating light for turbidity measurement into a test water, and two scattered lights on an irradiation direction line of the irradiated measuring light are received. In a turbidity measuring device provided in a measuring cell, two light receiving portions arranged open and a measuring portion for detecting the turbidity of the test water from a difference in a light receiving output of scattered light received by the two light receiving portions are provided. ,
The measurement cell is provided with a correction light source at an equal distance from the two light receiving units, and irradiates light for cell contamination correction during the test water so that the transmitted light is received by the two light receiving units. A correction unit that detects contamination of the measurement cell from a difference in the light reception output of the transmitted light received by the two light reception units and feeds back a correction output for eliminating the difference in the light reception output of the transmission light to the two light reception units; A turbidity measuring device.