CA1207553A - Apparatus for determining the density, concentration, specific gravity, etc. of a liquid - Google Patents
Apparatus for determining the density, concentration, specific gravity, etc. of a liquidInfo
- Publication number
- CA1207553A CA1207553A CA000425055A CA425055A CA1207553A CA 1207553 A CA1207553 A CA 1207553A CA 000425055 A CA000425055 A CA 000425055A CA 425055 A CA425055 A CA 425055A CA 1207553 A CA1207553 A CA 1207553A
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- Canada
- Prior art keywords
- light
- liquid
- wall surface
- refractive index
- inlet
- Prior art date
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Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/41—Refractivity; Phase-affecting properties, e.g. optical path length
- G01N21/43—Refractivity; Phase-affecting properties, e.g. optical path length by measuring critical angle
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- Physics & Mathematics (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Investigating Or Analysing Materials By Optical Means (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
An apparatus for determining the density, concentration, specific gravity, etc. of a liquid by employing an optical system include a light-transmissible body having an arcuately shaped interfacial wall surface adapted to be immersed in, or brought into contact with the liquid.
An apparatus for determining the density, concentration, specific gravity, etc. of a liquid by employing an optical system include a light-transmissible body having an arcuately shaped interfacial wall surface adapted to be immersed in, or brought into contact with the liquid.
Description
~2075S3 APPARATUS FOR DETERMINING THE DENSITY
CONCENTRATION, SPECIFIC GRAVITY, ETC. OF A LIQUID
BACICGROUND OF THE INVENTION
Field of the Invention:
-This invention relates to an apparatus for determining the density, concentration, specific gravity, etc. of a liquid by employing an optical system.
Description of the Prior Art:
There is known an apparatus for determining the density, concentration, specific gravity, etc. of a liquid by employing an optical system. The apparatus includes a light-transmissible body immersed in the liquid to be tested, and having an interfacial wall surface, contacting the liquia.
Light is emitted against the interfacial wall surface, and the light reflected thereon is received by a light-responsive element. The amount of the reflected light detected by the element i5 used for determining the density, concentration, specific gravity, etc. of the liquid. The apparatus is, however, inaccurate, since its light-receiving element receives not only the reflected light, but also external light, and is greatly influenced by the external light particularly when the amount of the reflected li~ht is small.
In order to overcome this problem, Japanese Patent Laid-Open Publication No. 139560/1978 (unexamined application) proposes the provision of a reflecting mirror on the interfacial wall surface to effect the total reflection of the incident light to minimize the reduction in the amount of the reflected -- 120'75S3 light. This ~icco~ is, hoveve~, dif~icul~ to mount, and has a ~ixed angle o incidence ~hich pec~its the total reflec~ion of incident light only unde~ specific conditions. Accocdingly, only a s~aLI change appears in the amount o~ Lig~t, and the re~ult~ o~ ~easuce~ent ace greatly a~fecte~ by exte~nal light.
This lo~rs the accuracy of the apparatus. Moreovee, t~
apparatus is difficult eo manuactu~e aè a reasonable cost.
SUMM~RY OE THE INVEN~ION
It is an object of the present invention to obviate o~
~tigate the above d~sadvant~ses.
According to the present invention there is provided an apparatus for determining the characteristic of a liquid that varies as the refractive index of the liquid varies, said apparatus including a light transmissible body made of a material with.a refractive index higher than the refractive index of the liquid and having a light inlet, a light outlet and an interfacial wall surface extending between said inlet and said outlet to transmit light therebetween said interfacial wall surface being immersible in said l.iquid and having an arcuate 2C contour with a radius of curvature selected so that light directed from said inlet to said interfacial wall surface has an incidence angle relative to said wall greater than the critical an~le as determined by the refractive index of the body and of the liquid and smaller than a right angle.
EXAklPLE ONLY WITH REFERENCE TO THE ACCOMPANYING DRAWINGS IN
WHICH:
CONCENTRATION, SPECIFIC GRAVITY, ETC. OF A LIQUID
BACICGROUND OF THE INVENTION
Field of the Invention:
-This invention relates to an apparatus for determining the density, concentration, specific gravity, etc. of a liquid by employing an optical system.
Description of the Prior Art:
There is known an apparatus for determining the density, concentration, specific gravity, etc. of a liquid by employing an optical system. The apparatus includes a light-transmissible body immersed in the liquid to be tested, and having an interfacial wall surface, contacting the liquia.
Light is emitted against the interfacial wall surface, and the light reflected thereon is received by a light-responsive element. The amount of the reflected light detected by the element i5 used for determining the density, concentration, specific gravity, etc. of the liquid. The apparatus is, however, inaccurate, since its light-receiving element receives not only the reflected light, but also external light, and is greatly influenced by the external light particularly when the amount of the reflected li~ht is small.
In order to overcome this problem, Japanese Patent Laid-Open Publication No. 139560/1978 (unexamined application) proposes the provision of a reflecting mirror on the interfacial wall surface to effect the total reflection of the incident light to minimize the reduction in the amount of the reflected -- 120'75S3 light. This ~icco~ is, hoveve~, dif~icul~ to mount, and has a ~ixed angle o incidence ~hich pec~its the total reflec~ion of incident light only unde~ specific conditions. Accocdingly, only a s~aLI change appears in the amount o~ Lig~t, and the re~ult~ o~ ~easuce~ent ace greatly a~fecte~ by exte~nal light.
This lo~rs the accuracy of the apparatus. Moreovee, t~
apparatus is difficult eo manuactu~e aè a reasonable cost.
SUMM~RY OE THE INVEN~ION
It is an object of the present invention to obviate o~
~tigate the above d~sadvant~ses.
According to the present invention there is provided an apparatus for determining the characteristic of a liquid that varies as the refractive index of the liquid varies, said apparatus including a light transmissible body made of a material with.a refractive index higher than the refractive index of the liquid and having a light inlet, a light outlet and an interfacial wall surface extending between said inlet and said outlet to transmit light therebetween said interfacial wall surface being immersible in said l.iquid and having an arcuate 2C contour with a radius of curvature selected so that light directed from said inlet to said interfacial wall surface has an incidence angle relative to said wall greater than the critical an~le as determined by the refractive index of the body and of the liquid and smaller than a right angle.
EXAklPLE ONLY WITH REFERENCE TO THE ACCOMPANYING DRAWINGS IN
WHICH:
2 -: ~ .
FIGURE 1 is a side elevational view oi an apparatus ~or determining the density, concentration, or speci~ic gravity of a li~uid;
FIGURE 2 is a sectional view taken alon~ the line X-X
of FIGURE l;
FIGURE 3 is a side elevational view of a further embodiment of the apparatus shown in FIGURE l;
FIGURE 4 is a sectional view taken taken along the line X-X of FIGURE 3;
FIGURE 5 is a side elevational view showing further a modified form of the light-transmissible body of the apparatus shown in FIGURE 1 and 3; and FIGURE 6 is a view similar FIGURE 3, but showing another embodiment of this invention.
DESCRIPTION OF THE PREFER~ED EMBODIM~NTS
Referring to FIGURES 1 and 2 of the drawings, liquid 1 to he examined has a refractive index of nl, and a light-transmissible body 2 is immersed therein and has a refractive index of n2 which is higber than that of the liquid 1. The light-transmissible body 2 is made of optical glass or plastic or like material, and has a light inlet 3, a light outlet 4 and an interfacial wall surface 5 therebetween~ The inlet 3 faces a source 6 of light, and a lens 7 is disposed between the inlet 3 /,~h f - rece ~`v~ rl5 and the light source 6, while a l1gh~ 06ponive element 8 faces outlet 4. The element 8 produces an output signal dependant upon the amount of light received by the element. The inlet 3 has a pair of guide wall surfaces 9 and 10, while tbe outlet 4 5i3 likewise has a pa r of guide wall surfaces 11 and ~. Thus, the ~ody 2 defines a path for light having a reflecting zone and transmitting zones. The light emitted by the source 6 is converted to parallel rays passing through the lens 7, enters the body 2 through its inlet 3, and is re~lected on the interfacial wall surface 5. The reflected light leaves body 2 through its outlet 4. Each of the inlet 3 and the outlet 4 may form an integral part of the body 2, or may alternatively comprise a separate ~emher formed from a good conductor of light, such as optical fiber, an~ connected to the body 2, for example, in such a manner that the conductors may be provided ~etween the inlet 3 and the source 6 and bet~een outlet 4 and the light-receiving element 8. In the latter case, the body 2 can more effectively collect the light from the source 6.
The light-transmissible body 2 has a ~lat sur~ace 13 in an area between the inlet 3 and the outlet 4, and remote ~rom the inter~acial wall surface 5. The ~lat sur~ace 13 does not directly participate in measurementO The wall surface 5 has an arcuate conto~r forming a part of an imaginary circle of which the center and radius are shown at O and R respectively and along which the light advances to the light receiving element 8, and to which the guide walls 10 and 12 are tangential.
The shape of the wall surface 5 is so selected as to ensure that all of the rays advancing straight through the inlet
FIGURE 1 is a side elevational view oi an apparatus ~or determining the density, concentration, or speci~ic gravity of a li~uid;
FIGURE 2 is a sectional view taken alon~ the line X-X
of FIGURE l;
FIGURE 3 is a side elevational view of a further embodiment of the apparatus shown in FIGURE l;
FIGURE 4 is a sectional view taken taken along the line X-X of FIGURE 3;
FIGURE 5 is a side elevational view showing further a modified form of the light-transmissible body of the apparatus shown in FIGURE 1 and 3; and FIGURE 6 is a view similar FIGURE 3, but showing another embodiment of this invention.
DESCRIPTION OF THE PREFER~ED EMBODIM~NTS
Referring to FIGURES 1 and 2 of the drawings, liquid 1 to he examined has a refractive index of nl, and a light-transmissible body 2 is immersed therein and has a refractive index of n2 which is higber than that of the liquid 1. The light-transmissible body 2 is made of optical glass or plastic or like material, and has a light inlet 3, a light outlet 4 and an interfacial wall surface 5 therebetween~ The inlet 3 faces a source 6 of light, and a lens 7 is disposed between the inlet 3 /,~h f - rece ~`v~ rl5 and the light source 6, while a l1gh~ 06ponive element 8 faces outlet 4. The element 8 produces an output signal dependant upon the amount of light received by the element. The inlet 3 has a pair of guide wall surfaces 9 and 10, while tbe outlet 4 5i3 likewise has a pa r of guide wall surfaces 11 and ~. Thus, the ~ody 2 defines a path for light having a reflecting zone and transmitting zones. The light emitted by the source 6 is converted to parallel rays passing through the lens 7, enters the body 2 through its inlet 3, and is re~lected on the interfacial wall surface 5. The reflected light leaves body 2 through its outlet 4. Each of the inlet 3 and the outlet 4 may form an integral part of the body 2, or may alternatively comprise a separate ~emher formed from a good conductor of light, such as optical fiber, an~ connected to the body 2, for example, in such a manner that the conductors may be provided ~etween the inlet 3 and the source 6 and bet~een outlet 4 and the light-receiving element 8. In the latter case, the body 2 can more effectively collect the light from the source 6.
The light-transmissible body 2 has a ~lat sur~ace 13 in an area between the inlet 3 and the outlet 4, and remote ~rom the inter~acial wall surface 5. The ~lat sur~ace 13 does not directly participate in measurementO The wall surface 5 has an arcuate conto~r forming a part of an imaginary circle of which the center and radius are shown at O and R respectively and along which the light advances to the light receiving element 8, and to which the guide walls 10 and 12 are tangential.
The shape of the wall surface 5 is so selected as to ensure that all of the rays advancing straight through the inlet
3 be effectively reflected under prescribed conditions. If the light L advancing straight along the guide wall 9 is reflected at point P on the wall sur~ace 5, a straight line connecting the lZ07SS3 center point O and the point P defines a normal line M, ana the light L and the normal line M define an incidence angle therebetween. If the angle ~ is larger than the critical angle, but smaller than a right angle, the light L is totally reflected at point P. The arcuate configuration of the wall surface 5 need be so formed as to satisfy these conditions.
- 4a -120755~
On the other hand, if the light L' advancing straight along the guide wall 10 is reflected at a point Q on the wall surface 5, a straight line connecting the points O and Q
defines a normal line N, and the light L' and the normal line N define an incidence angle ~' therebetween. The light L' is totally reflected at the point Q if the incidence angle ~' is not larger than a right angle. The shape of the wall surface 5 need satisfy these conditions, too.
This means that all the rays of light between the light L and the light L' are totally reflected on the wall surface 5 under prescribed conditions if the wall surface 5 has an arcuate contour forming a part of an imaginary circle passing through the points P and Q.
The normal line N and the light L' define a right angle therebetween, and the normal line N and the light L also define a right angle therebetween. The normal line N and the light L have an intersection S therebetween. The distance OS
between the points O and S is equal to R sin ~, and the radius R of the imaginary circle is equal to the distance OS between the points O and S plus the thickness t of the body 2 between the guide walls 9 and 10. Accordingly, the radius R can be obtained by the following equations (1) and (2):
R = R sin ~ + t (1) R = t/(l - sin ~) (2) The length Q of the arc PQ defined between the points P and Q
is expressed by the following equation:
Q = R~(2 ~3) (3) ~207SS3 in which (2 ~ ~) is the angle which the normal lines M and N
define therebetween at the point O.
The invention will now be described by way of example with reference to the application of a light-transmissible body 2 made of glass to a sugar solution having a concentration of 0 to about 65%. The glass of which the body 2 is made has a refractive index n2 of 1.520 at 20C, while a sugar solu-tion having a concentration of 0%, which is simple water, has a refractive index nl of 1.330 at 20C.
If the incidence angle ~ of the light L is e~ual to the critical angle, and if the thickness t between the guid~ ~alls 9 and 10 is 3 mm, the critical angle ~ is expressed as follows:
Refractive index (nl) of a sugar -1 solution havinq a concentration of 0%
Refractlve lnex ~nz)or tne llgnt-transmissible body Thus, ~ = sin 1 1 5332-o~~~ = 61.05 (degree of angle) The radius R defining the arcuate contour of the wall surface 5 can be obtained by equation (2), as follows:
L -~sin-61.0~~- = 24.01 (mm) The length Q of the arc between the points P and Q is:
Q = (90 - 61.05~ x 24.01 x 326~o = 12.13 (mm) Z0 Thus, the apparatus of this invention which is suitable for determining the concentration of a sugar solution having a concentration of 0 to 65~ may comprise an arcuately shaped interfacial wall surface forming a part of an imaginary circle ~Z07S53 having a radius R of 24.01 mm, and having an arc length (Q) of 12.13 mm, and a light inlet 3 and a light outlet 4 each having a width of 3 mm, and connected to the opposite ends, respectively, of the arcuate surface tangentially thereto.
The next is the explanation as to the measurement of concentration of the above sugar solution according to the apparatus designed hereinabove.
The arcuate wall surface 5 of the light-transmissible body 2 is brought into contact with, or immersed in the liquid 1 to be examined which is in the present case a sugar solution.
If the sugar solution has a concentration of 0%, all of the rays emitted by the light source 6 and advancing straight through the inlet 3 are totally reflected on the wall surface 5 in the area having an arc PQ length of 12.13 mm between the points P and Q. The reflected light passes through the outlet
- 4a -120755~
On the other hand, if the light L' advancing straight along the guide wall 10 is reflected at a point Q on the wall surface 5, a straight line connecting the points O and Q
defines a normal line N, and the light L' and the normal line N define an incidence angle ~' therebetween. The light L' is totally reflected at the point Q if the incidence angle ~' is not larger than a right angle. The shape of the wall surface 5 need satisfy these conditions, too.
This means that all the rays of light between the light L and the light L' are totally reflected on the wall surface 5 under prescribed conditions if the wall surface 5 has an arcuate contour forming a part of an imaginary circle passing through the points P and Q.
The normal line N and the light L' define a right angle therebetween, and the normal line N and the light L also define a right angle therebetween. The normal line N and the light L have an intersection S therebetween. The distance OS
between the points O and S is equal to R sin ~, and the radius R of the imaginary circle is equal to the distance OS between the points O and S plus the thickness t of the body 2 between the guide walls 9 and 10. Accordingly, the radius R can be obtained by the following equations (1) and (2):
R = R sin ~ + t (1) R = t/(l - sin ~) (2) The length Q of the arc PQ defined between the points P and Q
is expressed by the following equation:
Q = R~(2 ~3) (3) ~207SS3 in which (2 ~ ~) is the angle which the normal lines M and N
define therebetween at the point O.
The invention will now be described by way of example with reference to the application of a light-transmissible body 2 made of glass to a sugar solution having a concentration of 0 to about 65%. The glass of which the body 2 is made has a refractive index n2 of 1.520 at 20C, while a sugar solu-tion having a concentration of 0%, which is simple water, has a refractive index nl of 1.330 at 20C.
If the incidence angle ~ of the light L is e~ual to the critical angle, and if the thickness t between the guid~ ~alls 9 and 10 is 3 mm, the critical angle ~ is expressed as follows:
Refractive index (nl) of a sugar -1 solution havinq a concentration of 0%
Refractlve lnex ~nz)or tne llgnt-transmissible body Thus, ~ = sin 1 1 5332-o~~~ = 61.05 (degree of angle) The radius R defining the arcuate contour of the wall surface 5 can be obtained by equation (2), as follows:
L -~sin-61.0~~- = 24.01 (mm) The length Q of the arc between the points P and Q is:
Q = (90 - 61.05~ x 24.01 x 326~o = 12.13 (mm) Z0 Thus, the apparatus of this invention which is suitable for determining the concentration of a sugar solution having a concentration of 0 to 65~ may comprise an arcuately shaped interfacial wall surface forming a part of an imaginary circle ~Z07S53 having a radius R of 24.01 mm, and having an arc length (Q) of 12.13 mm, and a light inlet 3 and a light outlet 4 each having a width of 3 mm, and connected to the opposite ends, respectively, of the arcuate surface tangentially thereto.
The next is the explanation as to the measurement of concentration of the above sugar solution according to the apparatus designed hereinabove.
The arcuate wall surface 5 of the light-transmissible body 2 is brought into contact with, or immersed in the liquid 1 to be examined which is in the present case a sugar solution.
If the sugar solution has a concentration of 0%, all of the rays emitted by the light source 6 and advancing straight through the inlet 3 are totally reflected on the wall surface 5 in the area having an arc PQ length of 12.13 mm between the points P and Q. The reflected light passes through the outlet
4, and reaches the light-receiving element 8. In this case, the largest amount of reflected light is received by the element 8.
As the concentration of sugar solution as the liquid 1 to be examined increases, the critical angle ~, which depends on the light-transmissible body 2 and the concentration of the solution, varies. The critical angle ~ increases with an increase in the concentration of sugar in the solution, and there results a gradual reduction in that area in the portion PQ of the wall surface 5 in which the incidence angle of light exceeds the critical angle. The light gradually becomes unable to meet the rule of total reflection, beginning with the rays ~07SS3 close to the light L advancing straight along the guide wall 9. Accordingly, the amount of the reflected light received by the element 8 shows a gradual reduction. These changes are shown in TABLE 1. The data given therein testify the S accuracy of the apparatus, since a change in the concentration of sugar in the solution gives rise to a great change in the electromotive force (mV) generated in the light-receiving element which is responsive to the change in said concentration.
TABLE 1 shows the relation between the co~centration of sugar in the solution and the electromotive force (mV) generated in the light-receiving element. These results were obtained by using a NATIONAL MB-22N (trade mark) lamp having a voltage of 2 V applied thereto as the Iight source 6, and an O~RON
EE-66 (trade mark) device having an impedance of 150 ohms as the light-receiving element,8.
1;i~07~
Table 1 Concentration of cane sugar and Electromotive force generated in light~receiving element ~mV, 20C) \ Run Average +
Conc~ 1 2 3 4 5 deviation tration \ . .. ~ _ _ 0 119,4 119.0119.3 119.1119.4llg.24 + 0.18 9.8 101.2 101.5101.6 101.5101.8101.52 + 0.22 21.2 81.6 82.082.1 81.882.381.g6 + 0.27 31.8 65.3 65 165.1 64.965.Z65.1~ + 0.19 42.0 49.3 49.249.3 48.848.849.08 ~ 0.26 51.6 33.8 34.234.1 33.733.933.94 + 0~21 62.7 18.0 18.5ï8.2 18.218.318.24 + 0.18 67.3 11.9 1~.812.3 12.212.012.04 + 0.21 The design of the apparatus hereinabove described by way of example is based on the critical angle ~ obtained on the basis of the refractive index (nl) of a sugar solution having the minimum concentration, i.e., 0% which is in fact simple water. This is, however, not always the case, but the design of the light-transmissible body may have to be based on the critical angle ~
obtained on the basis of the refractive index (n2) corresponding to the minimum value of the concentration range to be measured.
In the event only a particular value of concentration is to be measured, the refractive index (nl) corresponding thereto may be used as a basis for the design of the light-transmissible body.
The apparatus of this invention, which is designed and _9_ 1207~iS3 used as hereinabove described, ensures a high accuracy in th~
determination of any unknown value of concentration if the electromotive force generated in the light-receiving element is previously obtained for each value of concentration to be determined.
As is obvious from the foregoing description, the apparatus of this invention is characterized in that the light-transmissible body which is immersed in, or brought into contact with the liquid to be examined has an arcuately shaped interfacial wall surface having a radius R so selected in rela-tion to the critical angle ~ obtained from the refractive index (nl) of the liquid and the refractive index (n2) of the light-transmissible body as to define an incidence angle ~
which enables the maximum reflection of light on the inter-facial wall surface. According to the apparatus shown in FIGURE l, the light reflected on the interfacial wall surface
As the concentration of sugar solution as the liquid 1 to be examined increases, the critical angle ~, which depends on the light-transmissible body 2 and the concentration of the solution, varies. The critical angle ~ increases with an increase in the concentration of sugar in the solution, and there results a gradual reduction in that area in the portion PQ of the wall surface 5 in which the incidence angle of light exceeds the critical angle. The light gradually becomes unable to meet the rule of total reflection, beginning with the rays ~07SS3 close to the light L advancing straight along the guide wall 9. Accordingly, the amount of the reflected light received by the element 8 shows a gradual reduction. These changes are shown in TABLE 1. The data given therein testify the S accuracy of the apparatus, since a change in the concentration of sugar in the solution gives rise to a great change in the electromotive force (mV) generated in the light-receiving element which is responsive to the change in said concentration.
TABLE 1 shows the relation between the co~centration of sugar in the solution and the electromotive force (mV) generated in the light-receiving element. These results were obtained by using a NATIONAL MB-22N (trade mark) lamp having a voltage of 2 V applied thereto as the Iight source 6, and an O~RON
EE-66 (trade mark) device having an impedance of 150 ohms as the light-receiving element,8.
1;i~07~
Table 1 Concentration of cane sugar and Electromotive force generated in light~receiving element ~mV, 20C) \ Run Average +
Conc~ 1 2 3 4 5 deviation tration \ . .. ~ _ _ 0 119,4 119.0119.3 119.1119.4llg.24 + 0.18 9.8 101.2 101.5101.6 101.5101.8101.52 + 0.22 21.2 81.6 82.082.1 81.882.381.g6 + 0.27 31.8 65.3 65 165.1 64.965.Z65.1~ + 0.19 42.0 49.3 49.249.3 48.848.849.08 ~ 0.26 51.6 33.8 34.234.1 33.733.933.94 + 0~21 62.7 18.0 18.5ï8.2 18.218.318.24 + 0.18 67.3 11.9 1~.812.3 12.212.012.04 + 0.21 The design of the apparatus hereinabove described by way of example is based on the critical angle ~ obtained on the basis of the refractive index (nl) of a sugar solution having the minimum concentration, i.e., 0% which is in fact simple water. This is, however, not always the case, but the design of the light-transmissible body may have to be based on the critical angle ~
obtained on the basis of the refractive index (n2) corresponding to the minimum value of the concentration range to be measured.
In the event only a particular value of concentration is to be measured, the refractive index (nl) corresponding thereto may be used as a basis for the design of the light-transmissible body.
The apparatus of this invention, which is designed and _9_ 1207~iS3 used as hereinabove described, ensures a high accuracy in th~
determination of any unknown value of concentration if the electromotive force generated in the light-receiving element is previously obtained for each value of concentration to be determined.
As is obvious from the foregoing description, the apparatus of this invention is characterized in that the light-transmissible body which is immersed in, or brought into contact with the liquid to be examined has an arcuately shaped interfacial wall surface having a radius R so selected in rela-tion to the critical angle ~ obtained from the refractive index (nl) of the liquid and the refractive index (n2) of the light-transmissible body as to define an incidence angle ~
which enables the maximum reflection of light on the inter-facial wall surface. According to the apparatus shown in FIGURE l, the light reflected on the interfacial wall surface
5 is directly received in the light-receiving element. It is alternatively possible to embody this invention in the form of an apparatus which determines the concentration, etc. of a li~uid by comparing the light reflected on the wall surface 5 and the light which does not pass through the light-transmissible body 2, as shown in FIGURES 3 and 4 by way of example.
Referring, therefore, to FIGURES 3 and 4, a mass of optical fiber 14 d~fines a light inlet and a mass of optical fiber 15 defines a light outlet. They are connected to the opposite ends, respectively, of the light-transmissible body 2.
The optical fiber 14 has another end connected to a light 1;Z07553 source 6. The optical fiber 15 has another end connected to one part 16a in a light-receiving element 16. A mass of optical fiber 17 extends between the light source 6 and another part 16b in the element 16. A light reducing device 20 is provided in fxont of the light source 6 for the purpose of correcting the difference in brightness between the light 18 passing through the body 2 and reflected on the wall surface 5 and reaching the one par_ 16a, and the light 19 passing directly from the light source 6 to the another part - 10 16b. The concentration, etc. of the liquid is determined based on the amount of such correction. The apparatus shown in FIGURES 3 and 4 provides a higher degree of accuracy in the determination of the concentration, density, specific gravity, etc. of a liquid.
Referring to FIGURE 5, the light-transmissible body 2 shown therein has an interfacial wall surface 5 having a semi-circular contour in the direction of advancing path of the light, and is, thereforer compact in construction.
~ttention is now directed to FIGURE 6 showing a modified form of the apparatus shown in FIGURE 3. The apparatus includes a pair of casings 21 and 22 placed one upon the other, and openably joined together by a hinge 23. The casing 22 has a recess 24 which is complementary to the arcuate wall surface 5 of the light-transmissible body 2 for holding therein the liquid 1 to be examined. A battery 25 for switching on the light source 6 and a voltage controller 26 are disposed in the casing 22. Reference numeral 27 denotes a lead wire for source ~20~553 of light. In the case of this apparatus, the liquid 1 to be examined is extracted and filled in the recess 24. This apparatus is compact in construction, and portable.
Although the invention has hereinabove been described with reference to several embodiments thereof, it is to be understood that further modifications or variations may be easily made by anybody of ordinary skill in the art with~t departing from the scope of this invention which is define~
by the appended claims. The following modifications are, f~r example, possible:
1. The whole wall surface 5, except the area between the points P and Q, may be treated in a manner not preventing the reflection of light, for example, masked or covered by a paint, while only the area between the points P and Q may be transparent. This arrangement contributes to preventing any reduction in the amount of reflected light to a further extentO
2. Although in the embodiments hereinabove described, the incidence angle ~ defined between the light L and the normal line M is equal to the critical angle ~, it is possible to employ an incidence angle ~ which is larger than the critical angle ~.
3. The distance t between the guide walls 3 and 10 in the light inlet may be varied appropriately.
As is obvious from the foregoing description, the apparatus of this invention can make accurate determination of density, concentration, specific gravity, etc. of a liquid, since the total reflection of incident light on the arcuate wall surface ~207553 under prescribed conditions minimi~es a reduction in the amount of reflected light to thereby ensure a great change in the amount of light received by the light-receiving element.
Moreover, the apparatus is easy to manufacture.
Referring, therefore, to FIGURES 3 and 4, a mass of optical fiber 14 d~fines a light inlet and a mass of optical fiber 15 defines a light outlet. They are connected to the opposite ends, respectively, of the light-transmissible body 2.
The optical fiber 14 has another end connected to a light 1;Z07553 source 6. The optical fiber 15 has another end connected to one part 16a in a light-receiving element 16. A mass of optical fiber 17 extends between the light source 6 and another part 16b in the element 16. A light reducing device 20 is provided in fxont of the light source 6 for the purpose of correcting the difference in brightness between the light 18 passing through the body 2 and reflected on the wall surface 5 and reaching the one par_ 16a, and the light 19 passing directly from the light source 6 to the another part - 10 16b. The concentration, etc. of the liquid is determined based on the amount of such correction. The apparatus shown in FIGURES 3 and 4 provides a higher degree of accuracy in the determination of the concentration, density, specific gravity, etc. of a liquid.
Referring to FIGURE 5, the light-transmissible body 2 shown therein has an interfacial wall surface 5 having a semi-circular contour in the direction of advancing path of the light, and is, thereforer compact in construction.
~ttention is now directed to FIGURE 6 showing a modified form of the apparatus shown in FIGURE 3. The apparatus includes a pair of casings 21 and 22 placed one upon the other, and openably joined together by a hinge 23. The casing 22 has a recess 24 which is complementary to the arcuate wall surface 5 of the light-transmissible body 2 for holding therein the liquid 1 to be examined. A battery 25 for switching on the light source 6 and a voltage controller 26 are disposed in the casing 22. Reference numeral 27 denotes a lead wire for source ~20~553 of light. In the case of this apparatus, the liquid 1 to be examined is extracted and filled in the recess 24. This apparatus is compact in construction, and portable.
Although the invention has hereinabove been described with reference to several embodiments thereof, it is to be understood that further modifications or variations may be easily made by anybody of ordinary skill in the art with~t departing from the scope of this invention which is define~
by the appended claims. The following modifications are, f~r example, possible:
1. The whole wall surface 5, except the area between the points P and Q, may be treated in a manner not preventing the reflection of light, for example, masked or covered by a paint, while only the area between the points P and Q may be transparent. This arrangement contributes to preventing any reduction in the amount of reflected light to a further extentO
2. Although in the embodiments hereinabove described, the incidence angle ~ defined between the light L and the normal line M is equal to the critical angle ~, it is possible to employ an incidence angle ~ which is larger than the critical angle ~.
3. The distance t between the guide walls 3 and 10 in the light inlet may be varied appropriately.
As is obvious from the foregoing description, the apparatus of this invention can make accurate determination of density, concentration, specific gravity, etc. of a liquid, since the total reflection of incident light on the arcuate wall surface ~207553 under prescribed conditions minimi~es a reduction in the amount of reflected light to thereby ensure a great change in the amount of light received by the light-receiving element.
Moreover, the apparatus is easy to manufacture.
Claims (11)
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. Apparatus for determining the characteristic of a liquid that varies as the refractive index of the liquid varies, said apparatus including a light transmissible body made of a material with a refractive index higher than the refractive index of the liquid, having a light inlet, a light outlet and an interfacial wall surface extending between said inlet and said outlet to transmit light therebetween and a light-receiving element facing said light outlet and for producing an output signal dependent upon the amount of light received thereby, said interfacial wall surface being immersible in said liquid and having an arcuate contour with a radius of curvature selected so that light directed from said inlet to said interfacial wall surface has an incidence angle relative to said wall greater than the critical angle as determined by the refractive index of the body and of the liquid and smaller than a right angle.
2. An apparatus as set forth in claim 1, wherein said light transmissible body is made of a material selected from the group comprising optical glass and plastics.
3. An apparatus as set forth in claim 1, wherein said interfacial wall surface has a semi-circular contour.
4. An apparatus as set forth in claim 1, wherein optical fiber is provided between a source of said light and said light inlet, and between said light outlet and said light-receiving element.
5. An apparatus as set forth in any one of claims 2, 3 or 4, wherein said interfacial wall surface is masked except for an area close to said light inlet.
6. An apparatus as set forth in claim 1, further including a light-reducing device provided adjacent to a source of said light, and optical fiber connected said light-reducing device to said light-receiving element which constitutes an optical system, so that the light reaching said light-receiving element through said body and the light reaching said light-receiving element through said optical fiber may be compared quantitatively for determining said density, concentration, and specific gravity.
7. An apparatus as set forth in claim 1, wherein a known density, concentration, and specific gravity, of the liquid are obtained in terms of the electromotive force generated in said light-receiving element to determine an unknown density, concentration, specific gravity, of a liquid to be measured.
8. An apparatus as set forth in claim 1, wherein said body is immersed in said liquid.
9. An apparatus as set forth in claim 6, further including a pair of casings placed one upon the other, and openably joined together, the optical system being disposed in the upper of said casings, while a power source and a housing portion for containing said liquid are provided in the lower casing.
10. An apparatus as set forth in claim 9, wherein said housing portion has a contour which is complementary to said interfacial wall surface.
11. Apparatus for determining the characteristic of a liquid that varies as the refractive index of the liquid varies, said apparatus including a light transmissible body made of a material having a refractive index higher than the refractive index of the liquid, said body having a light inlet, a light outlet and an interfacial wall surface extending between said inlet and said outlet to transmit light therebetween said interfacial wall surface having an arcurate contour with a radius of curvature selected to provide a point on said surface at which light impinges on said surface at an incident angle corresponding to the critical angle as determined by the refractive index of the body and of the liquid, the location of said point moving along said surface as the refractive index of the liquid varies, the intensity of light transmitted from the inlet to the outlet being determined by the location of said point.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP5283482A JPS58169050A (en) | 1982-03-31 | 1982-03-31 | Apparatus for measuring density, concentration, specific gravity and the like of liquid |
| JP57-52834 | 1982-03-31 | ||
| JP57-200157 | 1982-11-15 | ||
| JP20015782A JPS5990032A (en) | 1982-11-15 | 1982-11-15 | Device for measuring density, concentration, specific gravity or the like of liquid |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1207553A true CA1207553A (en) | 1986-07-15 |
Family
ID=26393504
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000425055A Expired CA1207553A (en) | 1982-03-31 | 1983-03-31 | Apparatus for determining the density, concentration, specific gravity, etc. of a liquid |
Country Status (8)
| Country | Link |
|---|---|
| CA (1) | CA1207553A (en) |
| DE (1) | DE3311202A1 (en) |
| DK (1) | DK158166C (en) |
| FR (1) | FR2524643B1 (en) |
| GB (1) | GB2121556B (en) |
| IT (1) | IT1161809B (en) |
| NL (1) | NL8301172A (en) |
| SE (1) | SE460561B (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6275230A (en) * | 1985-09-26 | 1987-04-07 | チバ−ガイギ− アクチエンゲゼルシヤフト | Analyzing method |
| FR2594951B1 (en) * | 1986-02-24 | 1989-08-04 | Photonique Ind | PROCESS FOR MEASURING THE PHYSICAL CHARACTERISTICS OF A LIQUID OR GASEOUS MEDIUM AND FIBER OPTIC DEVICE FOR IMPLEMENTING IT |
| GB8614741D0 (en) * | 1986-06-17 | 1986-07-23 | Bellhouse Medical Products Ltd | Optical sensor |
| DE3705359A1 (en) * | 1987-02-17 | 1988-08-25 | Schmidt & Haensch Franz | ELECTRONIC REFRACTOMETER |
| GB8818690D0 (en) * | 1988-08-05 | 1988-09-07 | Red Kite Technology Ltd | Refractive index measurement |
| DE4038354C2 (en) * | 1990-12-01 | 1994-06-30 | Bruker Analytische Messtechnik | ATR measuring probe |
| FR2694629B1 (en) * | 1992-08-10 | 1995-06-30 | Berechet Ion | SEMIGLOBULAR-COMPACT REFRACTOMETRIC SENSOR. |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1209036A (en) * | 1967-06-19 | 1970-10-14 | Nat Res Dev | Improvements in or relating to refractometers |
| DE2137842C3 (en) * | 1971-07-28 | 1981-11-05 | Ulrich, Helmut, Dipl.-Chem., 8000 München | Refractometer |
| GB1563374A (en) * | 1977-03-31 | 1980-03-26 | Marconi Co Ltd | Device for providing an indication of the refractive index of a fluid |
| US4240747A (en) * | 1979-10-03 | 1980-12-23 | Battelle Memorial Institute | Refractive-index responsive light-signal system |
-
1983
- 1983-03-26 DE DE19833311202 patent/DE3311202A1/en active Granted
- 1983-03-30 GB GB08308781A patent/GB2121556B/en not_active Expired
- 1983-03-30 DK DK147083A patent/DK158166C/en not_active IP Right Cessation
- 1983-03-30 IT IT8320383A patent/IT1161809B/en active
- 1983-03-30 SE SE8301800A patent/SE460561B/en not_active IP Right Cessation
- 1983-03-31 CA CA000425055A patent/CA1207553A/en not_active Expired
- 1983-03-31 NL NL8301172A patent/NL8301172A/en not_active Application Discontinuation
- 1983-03-31 FR FR8305312A patent/FR2524643B1/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| FR2524643A1 (en) | 1983-10-07 |
| DE3311202A1 (en) | 1983-10-06 |
| DK147083D0 (en) | 1983-03-30 |
| DK147083A (en) | 1983-10-01 |
| FR2524643B1 (en) | 1986-05-09 |
| GB2121556B (en) | 1985-10-23 |
| SE8301800L (en) | 1983-10-01 |
| IT8320383A0 (en) | 1983-03-30 |
| DK158166C (en) | 1990-08-27 |
| SE460561B (en) | 1989-10-23 |
| GB2121556A (en) | 1983-12-21 |
| DK158166B (en) | 1990-04-02 |
| DE3311202C2 (en) | 1988-05-11 |
| IT1161809B (en) | 1987-03-18 |
| NL8301172A (en) | 1983-10-17 |
| SE8301800D0 (en) | 1983-03-30 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |