JPS62135750A - Immersion type turbidity meter - Google Patents

Abstract

PURPOSE:To measure with a high accuracy a low turbidity by preventing a part of an irradiated light to a liquid to be measured, from reaching directly a photodetector, and also forming a diameter of a through-hole for making the irradiated light escape to the outside of a detector, to a diameter being a little larger than a beam diameter of the irradiated light. CONSTITUTION:A light beam emitted from a light source in a measuring part 18 is inputted to an optical fiber 8, and sent to an optical system 9. The optical system 9 converts this light beam to roughly parallel rays and emits them vertically to a window 7. An irradiated light 10 which has been projected into a liquid to be measured, in an inside case 5 generates a scattered light by a turbidity particle. In such a scattered light, a scattered light which has transmitted through a photodetecting window 12 provided in parallel to an optical axis of the irradiated light 10 is measured by a photodetector 13, and sent to the measuring part 18 through a signal line 14, etc. Also, a diameter of a through-hole 11 for making the irradiated light 10 escape to the outside of a detector 1 is formed to a size being a little larger than a beam diameter of the irradiated light 10. In such a way, the light beam which has passed through the through-hole 11 is obstructed by a stray light preventive plate 6 and does not reach the photodetector 13, even when it is reflected by a structure of the outside of the detector 1, and a disturbance of a stray light can be suppressed almost completely.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an immersion turbidity meter used for monitoring turbidity in purified water at terminals such as water treatment plants, pump stations, and water taps.

[Technical background of the invention and its problems]

At water treatment plants, water quality measurement is necessary for process management, and it is monitored to see whether the treated water is maintained at a set water quality. Water quality items to be monitored include turbidity,
Residual chlorine + p)I is the main component.

In addition, terminals such as pump stations and water taps monitor whether the water quality is maintained at the time of water delivery from the water purification plant using the above three items.

By the way, when measuring the three water quality items mentioned above, compactness of the device, reduction in the amount of sample water used, long-term stability, and ease of maintenance are required. Are suitable. and.

Immersion type instruments that determine H1'l for the above three items have already been sold. Among these, the pl+ meter can almost satisfy the measurement accuracy and the various requirements mentioned above.

Residual chlorine meters have recently been developed using a diaphragm electrode method, which also satisfies the above-mentioned requirements.

On the other hand, immersion type turbidity meters include transmitted light measurement method, scattered light measurement method, and transmitted light scattered light comparison method, but the measurement range is 0 to 20 ppH1 and the accuracy is about 5% of full scale. Therefore, it is unsatisfactory for use in water purification plants and terminals that require a measurement range of 0 to 2 ppm and an accuracy of about 5% of full scale. Therefore, until now, we had no choice but to use turbidity meters that measure surface scattered light using ground water sampling. With this surface scattered light measurement method, it has not been possible to make it more compact or to reduce the amount of sample water used.

Therefore, it has been desired to realize a submerged bed turbidity meter that can measure turbidity of 0 to 2 Pρm with high accuracy.

[Object of the Invention] An object of the present invention is to provide a submerged bed turbidity meter that can measure turbidity as low as 0 to 2 ppm with high precision in an immersion type.

[Summary of the invention]

The present invention is an immersed layer turbidimeter in which light from a light source placed outside the liquid in the bath is transmitted to a detector via an optical fiber, and this light is converted into almost parallel light into the liquid in the bath. An optical system for irradiating the measurement liquid and a light receiver for receiving scattered light from the inserted measurement liquid are arranged in a detector case that is fluid-tightly separated from the introduction part of the measurement liquid, and the optical system By providing a stray light prevention plate having a through hole for introducing the liquid to be measured, which is formed in the light emission direction with a diameter slightly larger than the beam diameter of the light, it is possible to prevent light other than the scattered light from the liquid to be measured from the optical system. The light is emitted from the through hole to the outside of the detector case, and the light reflected from outside the detector case is prevented from reaching the light receiver, so that stray light other than scattered light does not enter the light receiver. Highly accurate 31 with low turbidity of O~2ppm! It becomes possible to set I. Furthermore, maintenance is facilitated because there is no light source or other items that require maintenance inside the immersed detector.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

An embodiment of the immersed bed turbidity meter according to the present invention is shown in FIG.

As shown in Fig. 1, a detector (1) immersed in a liquid to be measured (20), a holder (16) that supports it, and an upper end of the holder (16) protruding from the liquid. A detection section is composed of a relay box (17) provided on the ground, and together with a measurement section (18) installed on the ground, a submerged layer turbidity meter is constructed. Although not shown, the measurement unit (18) includes a light source such as a halogen lamp, tungsten lamp, or laser, and an optical system that collects the light from the light source and inputs it to the end of the optical fiber. Contains a conversion circuit and the like for indicating turbidity based on input from the detector (1).

Detector case (2) forming the outer shell of the detector (1)
The outer case (3) is joined to the end of the holder (16) and communicates with the inside of the holder through the communication port (4), and the inner wall surface of this outer case (3) where the communication port (4) is provided. The opening on the opposite side of the wall facing the communication port (4) is closed by a stray light prevention plate (6), which is provided by partitioning the inside of the outer case with a space between it and other inner wall surfaces. It consists of an inner case (5).

Further, a window (7) made of a transparent material such as glass is provided on the wall facing the communication port (4) of the inner case (5).

An optical fiber (8), one end of which is connected to the light source and optical system installed in the measurement section (18), is connected to the relay box (18).
7) and the inside of the holder (16), the other end is located near the communication port (4), and the optical fiber (8)
At the terminal, there is a window (
7) An optical system such as a collimator that emits light perpendicular to the
9) is provided. In addition, the stray light prevention plate (6) has
A through hole (11) having a diameter slightly larger than the beam diameter of the irradiation light (10) is formed concentrically with the optical axis of the irradiation light. In addition, a light-receiving window (1
2) is provided. Furthermore, this light receiving window (12)
A light receiver (13) is placed inside the outer case (3) directly facing the light receiver (13), and the signal line (14) of this light receiver (13) is connected to the measuring section ( 1
8) is led to the conversion circuit.

In the immersion turbidity meter of the embodiment of the present invention configured as described above, the light emitted from the light source in the measuring section (18) is collected by the optical system and input into the optical fiber (8). , sent to the collimator (9). The collimator (9) converts the light emitted from the optical fiber (8) into substantially parallel light and emits it perpendicularly to the window (7). The irradiation light (10) projected into the liquid to be measured in the inner case (5) generates scattered light due to turbidity particles. Since this scattered light increases in proportion to turbidity, turbidity can be detected by measuring this scattered light. In the immersion type turbidimeter according to one embodiment of the present invention, out of this scattered light, the irradiated light (10
) The scattered light (90° scattered light) transmitted through the light-receiving window (12) provided parallel to the optical axis of the sensor is measured by the light receiver (13). The amount measured by this photoreceiver (13) is the signal line (14).
), the signal is sent to the 111 running section (18) via a holder (16) and a relay box (17), where it is subjected to signal processing such as amplification and conversion in a conversion circuit to indicate turbidity.

By the way, in order to increase the sensitivity at low turbidity, it is necessary to suppress stray light and improve the S/N ratio.

As a measure for this, in the present invention, firstly, the light irradiated into the liquid to be measured is substantially parallel light. When projected directly into the liquid to be measured from the optical fiber (8), the light spreads in a skirt shape by about 15%, and a portion reaches the light receiver (13) as stray light. 0-2
Since the amount of scattered light at low turbidity such as ρρm is extremely small, if the above-mentioned stray light enters, the S/N ratio becomes low and sensitivity cannot be obtained. This is prevented by using parallel light.

As a second measure, the diameter of the through hole (11) for allowing the irradiation light (10) emitted from the collimator (9) into the liquid to be measured to escape to the outside of the detector is set to be smaller than the beam diameter of the irradiation light (10). This is because the dimensions are slightly larger. As a result, even when the light passing through the through hole (11) is reflected by a structure outside the detector, such as a wall or piping, it is blocked by the stray light prevention plate (6) and reaches the light receiver (13). do not.

As explained above, according to the embodiments of the present invention, interference by stray light could be almost completely suppressed, making it possible to measure turbidities as low as 0 to 22 concave with high accuracy. In addition, the immersed detector (1) is composed of components that do not require maintenance, such as an optical fiber (8), a collimator (9), and a light receiver (13), and the light source is placed on the ground. Maintenance has also become extremely easy since it can be replaced.

In the above embodiment, the light source is placed inside the measuring section (18), but the same effect can be obtained even if the light source is placed inside the relay box (17) outside the liquid. Also, optical fiber (8)
Although a collimator has been described as an example of the optical system (9) that converts the light emitted from the optical system into nearly parallel light, any optical system that can emit light that is close to parallel light can be applied. In addition, the light receiving window (
12), the light receiver (13) directly receives the scattered light, but a condenser lens may be provided.6 Furthermore, in the embodiment, the light receiver (13) is configured to receive the 90' scattered light from the liquid to be measured. (13) is arranged, but the light receiver (13) can also be arranged at a position where forward scattered light and back scattered light are measured.

〔Effect of the invention〕

As described in detail above, according to the present invention, by making the irradiation light onto the liquid to be measured in the inner case of the detector almost parallel light, a part of the irradiation light is prevented from directly reaching the light receiver. In particular, the diameter of the through hole through which the irradiated light escapes to the outside of the detector case is made slightly larger than the beam diameter of the irradiated light, and the light exiting from this through hole is transmitted to structures outside the detector, e.g. wall,
Even when reflected by piping, etc., the reflected light is prevented from reaching the light receiver as stray light, which prevents stray light other than scattered light from entering the light receiver. This enables highly accurate measurement of turbidity as low as 2 ppm. Furthermore, since there is no light source or other items that require maintenance inside the immersed detector, maintenance has become extremely easy.

[Brief explanation of drawings]

FIG. 1 is a sectional view of essential parts showing the configuration of an immersion turbidity meter according to an embodiment of the present invention.

Claims (1)

[Claims] In an immersion type turbidity meter that detects the turbidity of the liquid to be measured by irradiating light onto the liquid to be measured introduced into the detector case immersed in the liquid to be measured and receiving the scattered light from the liquid to be measured. , an optical system that irradiates the introduced liquid to be measured as substantially parallel light from a light source that is disposed in a detector case that is liquid-tightly separated from the introduction part of the liquid to be measured, and that is transmitted via an optical fiber; a light receiver that receives scattered light from the introduced liquid to be measured;
a stray light prevention plate having a through hole for introducing the liquid to be measured into the detector case, the diameter being slightly larger than the beam diameter of the light in the light emission direction of the optical system; The immersion type is characterized in that it is configured to emit light other than scattered light from the liquid to be measured from the system to the outside of the detector case from the through hole, and to prevent reflected light etc. from outside the detector case from reaching the light receiver. Turbidity meter.