JP2023105732A - Concentration measuring device - Google Patents

Abstract

To provide a concentration measuring device capable of measuring even higher concentration by suppressing reduction of transmittance of measuring light.SOLUTION: A concentration measuring device 1 includes: a body 3 having a flow passage 2 for flowing fluid to be measured; a translucent window 6 attached to the body 3 along the flow passage 2 and having a light incident part 4 and a light outgoing part 5 opposed to each other across the flow passage 2; a light emitting part 7 for making the light incident on the flow passage 2 through the light incident part 4; and a light receiving part 8 for receiving the light emitted from the flow passage 2 through the light outgoing part 5. The light translucent window 6 has a projection part 9 projecting in a direction for shortening a separation distance between the light incident part 4 and the light outgoing part 5.SELECTED DRAWING: Figure 1

Description

The present invention relates to a concentration measuring device.

Conventionally, light of a predetermined wavelength is incident on a measurement cell provided with a flow path, and the absorbance is measured by detecting with a photodetector the light absorbed by the gas when passing through the measurement cell. 2. Description of the Related Art There are known concentration measuring devices that apply a law to calculate gas concentration from absorbance (for example, Patent Documents 1, 2, 3, etc.).

In addition, in order to improve measurement accuracy, there is also known a concentration measuring device that splits a part of the light before it enters the measurement cell and detects it as reference light to correct errors in the absorbance calculation value due to deterioration of the incident light. (For example, Patent Documents 3, 4, etc.).

International publication WO2016/017122 pamphlet International publication WO2014/181527 pamphlet International publication WO2018/021311 pamphlet International publication WO2017/029791 pamphlet

In this type of concentration measuring apparatus, a wavelength in the absorption peak wavelength region of the substance to be measured is generally used as the wavelength of the incident light.

On the other hand, as the number of molecules of the substance to be measured increases, that is, as the concentration increases, the transmittance of the measuring light decreases exponentially.

Therefore, in the conventional density measuring apparatus, it is sometimes difficult to measure the required density due to the decrease in transmittance at high density.

SUMMARY OF THE INVENTION Accordingly, it is a primary object of the present invention to provide a concentration measuring apparatus capable of measuring even higher concentrations.

In order to achieve the above object, a concentration measuring device according to an aspect of the present invention includes a main body having a flow path for flowing a fluid to be measured, and attached to the main body along the flow path to sandwich the flow path. a light-transmitting window having a light-incident portion and a light-output portion facing each other; a light-emitting portion that causes light to enter the flow channel through the light-incidence portion; a light-receiving portion that receives light, wherein the translucent window has a protruding portion that protrudes in a direction that shortens the separation distance between the light-incident portion and the light-emitting portion.

In one aspect, the light-transmitting window may include the light entrance section and the light exit section as separate bodies, and the protrusion may include a first protrusion provided in the light entrance section.

In one aspect, the light incident portion includes a first plate-like base portion having a peripheral portion fixed to the main body, and the first protrusion portion is provided to protrude from the first plate-like base portion.

In one aspect, the light-transmitting window includes the light incident portion and the light emitting portion as separate bodies, and the projecting portion includes a second projecting portion provided on the light emitting portion.

In one aspect, the light emitting portion includes a second plate-like base portion having a peripheral portion fixed to the main body, and the second protrusion portion is provided to protrude from the second plate-like base portion.

In one aspect, the light-transmitting window includes a light-transmitting block integrally including the light entrance portion and the light exit portion, and the light-transmitting block is fixed to the main body.

In one aspect, the light-transmitting block has a through hole that forms part of the flow path, and the projecting portion is provided so as to protrude from the inner periphery of the through hole.

In one aspect, the protrusion is annular.

In one aspect, the main body includes a through-hole that intersects with the flow path, and the through-hole engages a first portion through which the flow path opens and the peripheral portion of the first plate-shaped base. a second portion formed of a stepped portion, wherein the main body further includes a first fixing member that presses and fixes the peripheral portion, the projecting portion protrudes from the first portion, and the separation distance is the It is smaller than the diameter of the channel that opens into the through hole.

In one aspect, the main body includes a through hole that intersects with the flow path, and the through hole engages a first portion through which the flow path opens and the peripheral portion of the second plate-shaped base. a third portion formed of a stepped portion, the main body further including a second fixing member that presses and fixes the peripheral edge portion, the projecting portion protrudes from the first portion, and the separation distance is the smaller than the diameter of the channel opening into the through-hole.

In one aspect, the main body includes a through hole that intersects with the flow path, the translucent block is inserted into the through hole so that the through hole and the flow path are aligned, and the main body includes: A fixing member for holding and fixing the light-transmitting block from both sides is included.

According to the present invention, by providing the transmission window with a projecting portion and shortening the optical path length of the measurement light passing through the fluid to be measured, it is possible to suppress a decrease in the transmittance of the measurement light and measure even higher concentrations. It becomes possible.

1 is a cross-sectional view showing a first embodiment of a concentration measuring device according to the present invention; FIG. 2 is an enlarged cross-sectional view of a main part of the concentration measuring device of FIG. 1; FIG. 2 is a cross-sectional view showing an exploded state of the concentration measuring device of FIG. 1; FIG. FIG. 2 is a perspective view showing a translucent window that is a component of the concentration measuring device of FIG. 1; FIG. 5 is a cross-sectional view showing a second embodiment of a concentration measuring device according to the present invention; FIG. 6 is a perspective view showing a translucent window that is a component of the concentration measuring device of FIG. 5; FIG. 7 is a perspective view showing a cross section of the translucent window of FIG. 6;

An embodiment of a concentration measuring device according to the present invention will be described below with reference to FIGS. 1 to 7. FIG. In addition, the same reference numerals are attached to the same or similar components throughout all the drawings and all the embodiments.

First, a concentration measuring device according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 4. FIG. The concentration measuring device 1 of the first embodiment has a main body 3 having a flow path 2 for flowing a fluid G to be measured such as ozone gas, and is attached to the main body 3 along the flow path 2 so as to face each other with the flow path 2 interposed therebetween. a light-transmitting window 6 having a light incident portion 4 and a light emitting portion 5, a light emitting portion 7 for causing light to enter the flow channel 2 via the light incident portion 4, and a light emitting portion 5 to emit light from the flow channel 2. and a light receiving portion 8 for receiving the light. The translucent window 6 has a protruding portion 9 protruding in the direction of shortening the separation distance L (FIG. 2) between the light incident portion 4 and the light emitting portion 5 .

In the first embodiment, the translucent window 6 includes the light entrance section 4 and the light exit section 5 as separate bodies. In addition, the projecting portions 9 are provided in the light incident portion 4 and the light emitting portion 5 respectively, the light incident portion 4 is provided with the first projecting portion 9a, and the light emitting portion 5 is provided with the second projecting portion 9b. ing. In the illustrated example, the light entrance portion 4 and the light exit portion 5 have the same shape and size.

The light incident portion 4 has a first plate-like base portion 4a fixed to the main body 3 at a brim-shaped peripheral edge portion, and a first projecting portion 9a integrally protruding therefrom. The light emitting portion 5 has a second plate-shaped base portion 5a whose peripheral portion is fixed to the main body 3, and a second projecting portion 9b integrally protruding therefrom. With such a configuration, the light entrance portion 4 and the light exit portion 5 have a hat-shaped or convex cross-section. Although not shown, only one of the light entrance portion 4 and the light exit portion 5 may be provided with a protrusion. Mechanically and chemically stable sapphire glass is preferably used for the translucent window 6, but other stable materials such as quartz glass can also be used. Although the first plate-shaped base 4a and the second plate-shaped base 5a in the illustrated example are disk-shaped, they may have other shapes.

The main body 3 has a through hole 10 that intersects with the channel 2 . The channel 2 and the through hole 10 are provided in the base portion 3a of the main body 3. As shown in FIG. The through-hole 10 includes a first portion 10a through which the flow path 2 is opened, a second portion 10b forming a stepped portion to which the peripheral portion of the first plate-like base portion 4a is locked, and the above-mentioned portion of the second plate-like base portion 5a. It has a third portion 10c forming a stepped portion with which the peripheral portion is engaged, a fourth portion 10d to which the first fixing member 3b is fitted, and a fifth portion 10e to which the second fixing member 3c is fitted.

By fixing the first fixing member 3b to the base portion 3a of the main body 3, the peripheral edge portion of the first plate-like base portion 4a is fixed by being sandwiched between the first fixing member 3b and the base portion 3a. Further, by fixing the second fixing member 3c to the base portion 3a of the main body 3, the peripheral edge portion of the second plate-like base portion 5a is sandwiched and fixed between the second fixing member 3c and the base portion 3a. Considering the sealing performance between the first plate-like base portion 4a and the second plate-like base portion 5a and the base portion 3a, a sealing material 11 is arranged as shown in FIG. The sealing material 11 is preferably provided at a position to seal two side surfaces of each of the first plate-shaped base portion 4a and the second plate-shaped base portion 5a. Therefore, grooves into which the sealing material 11 is fitted are formed in the two orthogonal side surfaces forming the stepped portion of the second portion 10b. Similarly, a groove into which the sealing material 11 is fitted is formed in the two orthogonal side surfaces forming the stepped portion of the third portion 10c.

The first portion 10a of the through-hole 10 is closed at its upper and lower surfaces by the light entrance portion 4 and the light exit portion 5, and the flow path 2 formed in the base portion 3a of the main body 3 opens on its peripheral side surface. This constitutes part of the flow path through which the fluid G to be measured flows. In the first portion 10a, the first protruding portion 9a and the second protruding portion 9b protrude inward, and the distance L between the light incident portion 4 and the light emitting portion 5 is shortened. It is smaller than the hole diameter (diameter) H of the channel 2 that opens to the portion 10a. The separation distance L corresponds to the optical path length, which will be described later.

A light-emitting element such as a light-emitting diode or a laser diode is preferably used for the light-emitting portion 7 . The light-emitting portion 7 in the illustrated example is a so-called bullet-shaped light-emitting diode in which the sealing resin covering the LED element is shaped like a bullet. A light-emitting element that emits light having a wavelength corresponding to the type of fluid to be measured is used as the light-emitting unit 7 . For example, when measuring the concentration of ozone gas, a light-emitting element with a wavelength of 230 nm to 320 nm is preferably used. An optical sensor such as a photodiode or a phototransistor can be used for the light receiving unit 8 .

A reference light detector 12 for detecting light emitted from the light emitting section 7 as reference light is provided on the side of the light emitting section 7 . Also, the reference light detector 12 is arranged behind the light emitting unit 7 . That is, the distance between the reference light detector 12 and the translucent window 6 is greater than the distance between the light emitting section 7 and the translucent window 6 . The reference light detector 12 can use an optical sensor similar to the light receiving section 8 .

The light emitter 7 and the reference light detector 12 are attached to the recess 13 a of the holding member 13 . The holding member 13 is fixed to the first fixing member 3b. The first fixing member 3b has a first hole 3b1 having substantially the same diameter and the same axis as the through hole 10 of the base portion 3a. The recessed portion 13a of the holding member 13 has an inner circumference with substantially the same diameter as the first hole 3b1, and the opening of the first hole 3b1 and the opening of the through hole 10 substantially match.

The light receiving portion 8 is attached to the second hole 3c1 of the second fixing member 3c. The second hole 3c1 has substantially the same diameter as the through hole 10 and is positioned on the same axis. A condensing lens 14 is arranged in the second hole 3c1. The condenser lens 14 is provided between the light emitting section 5 and the light receiving section 8 .

The light emitted from the light emitting portion 7 passes through the concave portion 13a, the first hole 3b1, the light incident portion 4, the first portion 10a which is a part of the flow path 2, the light emitting portion 5, and the condensing lens in the first hole 3b1. 14 in order and is received by the light receiving portion 8 . Light of a predetermined wavelength is absorbed by the fluid to be measured when passing between the light entrance portion 4 and the light exit portion 5 .

The detection signal light detected by the light receiving section 8 and the reference light detector 12 is sent to the control section 15 . The control unit 15 controls the current supplied to the light emitting unit 7, and includes a measurement circuit 16 that measures the outputs of the light receiving unit 8 and the reference photodetector 12 as voltages using a known current-voltage conversion circuit. In addition, the control unit 15 can include a data logger 17 for storing measured values measured by the measuring circuit 16, a computer 18 for calculating concentration and correction processing, and the like. Based on this, density calculation processing and correction processing can be performed. Since the method of calculating the gas concentration by applying the Beer-Lambert law and the method of correcting the calculated value using the reference light are well known, detailed description thereof will be omitted.

According to the Beer-Lambert law, the concentration of the fluid to be measured is derived from the following equation (1).

A=aLc (1)
Here, A is the absorbance, a is the molar extinction coefficient, L is the optical path length, and c is the concentration. Also, the absorbance A is defined as A=-log ₁₀ I/I ₀ , where I ₀ is the initial intensity of light of a specific wavelength impinging on the fluid to be measured, and I is the intensity of light transmitted through the fluid to be measured. I/I ₀ is the transmittance.

The optical path length is the length of light passing through the fluid to be measured, and corresponds to the separation distance L. As the concentration of the fluid to be measured increases, the transmittance decreases exponentially, and concentration measurement becomes difficult when the absorption peak saturates.

According to the present invention, by providing the projecting portion 9 to shorten the optical path length, the transmittance is increased compared to the case where the projecting portion 9 is not provided, i.e., when the translucent window is formed of a simple flat plate. can be made As a result, the present invention can measure a higher concentration than when there is no projecting portion 9. FIG.

Next, a concentration measuring device according to a second embodiment of the invention will be described with reference to FIGS. 5 to 7. FIG.

The light-transmitting window 6 of the second embodiment is composed of a light-transmitting block integrally including the light entrance portion 4 and the light exit portion 5 . Other configurations are the same as those of the first embodiment. The light-transmitting block in the illustrated example is a rectangular parallelepiped, but may be cylindrical.

A light-transmitting block that constitutes the light-transmitting window 6 has a through hole 2 a that constitutes a part of the flow path 2 . The protrusion 9 is provided so as to protrude from the inner circumference of the through hole 2a. The through hole 2a matches and communicates with the channel 2 formed in the base portion 3a of the main body 3. As shown in FIG. Although the projection 9 in the illustrated example is annular, it may have other shapes.

A light-transmitting block constituting the light-transmitting window 6 is fitted into a rectangular through-hole 10 provided in the base portion 3a of the main body 3, and is sandwiched and fixed by the first fixing member 3b and the second fixing member 3c. ing. A sealing material 11 is provided between the light-transmitting block constituting the light-transmitting window 6 and the main body 3 .

As in the case of the first embodiment, the density measuring apparatus 1 of the second embodiment has the protrusion 9, so that the optical path length is shortened compared to the case without the protrusion, and higher density can be measured. It becomes possible.

The present invention is not interpreted as being limited to the above-described embodiments, and various modifications are possible without departing from the scope of the present invention.

1 Concentration measuring device 2 Flow path 3 Main body 4 Light incident part 5 Light emitting part 6 Translucent window 7 Light emitting part 8 Light receiving part 9 Protruding part 10 Through hole

Claims (11)

a main body having a channel for flowing the fluid to be measured;
a translucent window attached to the main body along the flow path and having a light incident portion and a light output portion facing each other with the flow path interposed therebetween;
a light-emitting portion that causes light to enter the flow path through the light-incident portion;
a light receiving unit that receives the light emitted from the flow path through the light emitting unit;
The translucent window has a protruding portion that protrudes in a direction that shortens the distance between the light entrance portion and the light exit portion,
Densitometer. the light-transmitting window includes the light entrance section and the light exit section as separate bodies,
wherein the protrusion includes a first protrusion provided on the light incident section,
The concentration measuring device according to claim 1. The light incident part includes a first plate-shaped base part whose peripheral edge is fixed to the main body,
The first projecting portion protrudes from the first plate-shaped base,
3. The concentration measuring device according to claim 2. the light-transmitting window includes the light entrance section and the light exit section as separate bodies,
wherein the protrusion includes a second protrusion provided on the light emitting section,
The concentration measuring device according to claim 1. The light emitting part includes a second plate-shaped base part whose peripheral edge is fixed to the main body,
The second projecting portion protrudes from the second plate-shaped base,
5. The concentration measuring device according to claim 4. the light-transmitting window includes a light-transmitting block integrally including the light entrance portion and the light exit portion;
wherein the translucent block is fixed to the body;
The concentration measuring device according to claim 1. the light-transmitting block has a through hole forming part of the flow path,
wherein the protruding portion is provided to protrude from the inner periphery of the through hole;
7. The concentration measuring device according to claim 6. 8. The concentration measuring device according to claim 7, wherein said protrusion is annular. the body comprises a through-hole intersecting with the channel,
The through-hole includes a first portion through which the flow path is opened and a second portion formed of a stepped portion to which the peripheral portion of the first plate-shaped base engages,
The main body further includes a first fixing member that presses and fixes the peripheral edge,
4. The concentration measuring device according to claim 3, wherein said projecting portion protrudes from said first portion, and said distance is smaller than the diameter of said channel opening to said through hole. the body comprises a through-hole intersecting with the channel,
The through-hole includes a first portion through which the flow path opens, and a third portion formed of a stepped portion to which the peripheral portion of the second plate-shaped base engages,
The main body further includes a second fixing member that presses and fixes the peripheral edge,
6. The concentration measuring device according to claim 5, wherein said projecting portion protrudes from said first portion, and said separation distance is smaller than the diameter of said channel opening to said through hole. the body comprises a through-hole intersecting with the channel,
the light-transmitting block is inserted into the through-hole such that the through-hole and the flow path match;
The main body includes a fixing member that sandwiches and fixes the light-transmitting block from both sides,
The concentration measuring device according to claim 7.