JPH02259549A - Liquid concentration sensor - Google Patents

Abstract

PURPOSE:To obtain the rigid sensor of simple constitution by reflecting a light beam which is projected on a glass rod as a detection part by a reflecting film, and reflecting part of it totally by the internal surface of the glass rod and making the light incident on a photodetection part. CONSTITUTION:The end surface of one end side of the glass rod 12 is cut slantingly at an angle alpha to the axis and coated with the reflecting film 12a to constitute the detection part. The light receiving and emitting integrated element 14 composed of a light emitting diode 14a and a photosensor 14b in one body is provided on the other end side of the glass rod 12. Then the light emitting diode 14a is driven by a light emission part driving device 15 to project the light beam with specific intensity. The emitted light is propagated in the glass rod 12 and reflected by the reflecting film 12a. At a sensing part A, part of the light beam is transmitted through liquid 7 to be measured, but the rest light beam is reflected totally and made incident on the photosensor 14b. The quantity of the light beam which is reflected totally by the internal surface of this glass rod 12, i.e. the quantity of the light incident on the photosensor 14b is detected to measure the concentration of the liquid 7 to be measured.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention utilizes the fact that the reflection characteristics at the detection section change depending on the concentration value of the liquid to be measured. This invention relates to a liquid concentration sensor that determines the concentration of a tlj constant liquid.

(Prior Art) Conventionally, it has been known that there is a certain correlation between the concentration (volume fraction) of a liquid and the refractive index of the liquid. Taking advantage of this correlation, a liquid concentration sensor as shown in FIG. 8 is used.

In the figure, 1 is a first optical fiber, one end of this optical fiber 1 is connected to an optical splitter 2, and the other end has a cladding portion 1a peeled off and has a refractive index of nc.

The core portion 1b of is exposed and serves as a detection portion.

The exposed core portion 1b of the detection portion is curved, and a reflective film 1c is formed at the tip. 3 is a light emitting part with a built-in light emitting diode that emits a light beam to the detection part 1;
is connected to the optical splitter 2 via an optical fiber 4 . Reference numeral 5 denotes a photodetection section with a built-in photosensor, which is connected to the optical splitter 2 via a third optical fiber 6. 8
9 is an A/D converter that converts the analog electrical signal from the photodetector 5 into digital data; The CPU 11 that performs calculations is a display unit that displays the calculation results of the CPU 9.

The core portion 1b which is the detection portion of the first optical fiber 1
is placed in the liquid to be measured 7 having a refractive index of nM.

Next, the operation of the above configuration will be explained. The light beam emitted from the light emitting section 3 is sent to the second optical fiber 4. It reaches the core portion 1b of the first optical fiber 1 via the optical splitter 2. here,
Since the propagation mode in the optical fiber 1 is multimode, the angle of the light beam with respect to the inner surface of the core portion 1b includes various components.

Therefore, a part of the light beam is transmitted to the measurement liquid on the exposed inner surface of the core portion 1b, but the remaining light beam is totally reflected on the exposed inner surface of the core portion 1b. Then, the totally reflected light beam is reflected by the reflective film 1c, the optical path is branched by the optical splitter 2, and the light beam is transmitted to the photodetector 5 via the third optical fiber 6.
incident on the photo sensor.

The light beam incident on the photodetector 5 is converted into an analog electrical signal here. This analog electrical signal is converted into digital data by an A/D converter 8. Next, the concentration of the liquid to be measured 7 is determined by arithmetic processing using this digital data by the CPU 9 which has read various comparison data from the ROM 10, and the result of this calculation (concentration) is displayed on the display unit 11.

According to the above configuration, the exposed core portion 1b of the light beam
The proportion of the amount of light that is totally reflected on the inner surface is a function of the refractive index nM of the liquid 7 to be measured. On the other hand, since there is a certain correlation between the concentration of the liquid to be measured 7 and the refractive index of the liquid to be measured 7, the amount of light beam that causes total reflection, that is, the amount of light that enters the photosensor in the photodetector 5 By detecting this, the concentration of the liquid to be measured 7 can be measured. By arbitrarily selecting the curvature of the core portion 1b, it is possible to measure the concentration of all liquids 7 to be measured whose refractive index is nM<n(0. For example, since there is no generation of electrical sparks and no influence of electromagnetic induction, it is possible to realize a liquid concentration sensor suitable for chemical plants and the like that require safety and explosion-proof properties.

(Problem to be solved by the invention) However, in the conventional example with the above configuration, the CPU.

Since the ROM is used, there are problems in that the circuit configuration becomes complicated and expensive.

Furthermore, since the first optical fiber 1 is used as the detection section, there is a problem that the detection section is easily broken. Also,
Since the diameter of the first optical fiber 1 used as the detection section is small, the light emission section 3 and the light detection section 5 cannot be provided on the end face of the optical fiber 1, and the light emission section is connected via the optical splitter 2. 3 and a photodetector 5 are connected to the first optical fiber 1. Therefore, there is also a problem that the structure becomes complicated.

The present invention has been made in view of the above problems, and its object is to provide a liquid concentration sensor that is durable and has a simple structure.

(Means for Solving the Problems) The present invention solves the above problems, in which a reflective film is formed on one end side of a solid rod made of a transparent material, and is disposed in a liquid to be measured.
a light emitting part provided at the other end of the solid rod for emitting a light beam to the detection part; and a light emitting part provided integrally with the light emitting part at the other end of the solid rod. , a photodetection section that detects the reflected light from the detection section and generates a voltage according to the intensity of the reflected light; a reference voltage generation section that generates a predetermined reference voltage; and the reference voltage generation section. a comparison section that compares a reference voltage from the photodetector with a voltage from the photodetection section, and a display section that displays a display according to the comparison result of the comparison section, and the reflection characteristic at the detection section is measured. The present invention is characterized in that the display section is configured to display a display according to the concentration of the liquid to be measured by utilizing the fact that the concentration changes depending on the concentration of the liquid.

(Function) In the liquid concentration sensor of the present invention, the light beam emitted from the light emitting part to the solid rod which is the detection part is reflected by the reflective film, and then a part of it is totally reflected by the inner surface of the solid rod, and the light beam is emitted from the light detection part to the solid rod which is the detection part. incident on . Then, this incident light is converted into a voltage according to the amount of light by the photodetector, and after this detected voltage is compared with a reference voltage, a display according to the concentration of the liquid to be measured is performed on the display.

(Example) Next, one embodiment of the present invention will be described using the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention.

In the figure, 12 is a glass rod made of quartz and having a refractive index of nco. One end side (tip side) of this glass rod 12 is used as a detection part, and has a so-called obliquely cut cylindrical shape with an end face cut obliquely at an angle α with respect to the axis. The end face is coated with a reflective film 12a. On the other end side (base end side) of the glass rod 12,
A holder 13 is provided. This holder 13 includes a light emitting diode 14a as a light emitting part whose light emitting surface is in contact with the end surface of the other end of the glass rod 12, and a photosensor 1 as a light detecting part whose light receiving surface is also in contact with the end surface of the other end.
A light emitting/receiving integrated element 14 is provided which is integrally provided with the light emitting/receiving element 4b.

15 is a light emitting unit driving device for driving the light emitting diode 14a, and 16 to 18 are predetermined reference voltages vA.

Reference voltage generation circuits that generate VB and vc, 19 to 21 are reference voltages vA + of the reference voltage generation circuits 16 to 18;
Comparators 22-24 compare VB+VC and the voltage from photosensor 14b. This is a display device driven by the outputs of comparators 19-21.

The glass rod 12 is placed in a liquid to be measured 7 having a refractive index of nM.

Next, the operation of the above configuration will be explained. light emitting diode 14
a is driven by the light emitting unit driving device 15 and emits a light beam of a predetermined intensity. The light beam emitted from the light emitting diode 14a propagates within the glass rod 12 and is reflected by the reflective film 12a.

Since this light beam is multimode, part of the light beam is transmitted to the liquid to be measured 7 at the sensing portion A, but the remaining light beam is totally reflected. The totally reflected light beam then enters the photosensor 14b.

According to this configuration, the amount of light beam that causes total reflection is a function of the refractive index nM of the liquid 7 to be measured. On the other hand, since there is a certain correlation between the concentration of the liquid 7 to be measured and the refractive index nM of the liquid 7 to be measured, the amount of light beam that causes total reflection on the inner surface of the glass rod, that is, the photo sensor 14b
By detecting the amount of light incident on the liquid 7, the concentration of the liquid 7 to be measured can be measured.

The light beam incident on the photosensor 14b has an analog voltage v proportional to the amount of light of the light beam.

is converted to This analog voltage VD is
is applied to one terminal of 21. Here, this analog voltage VD is compared with the reference voltage vA+''B*VC applied to the other terminals of the comparators 19-21.

Therefore, the detected analog voltage V. When the voltage reaches the reference voltage vA, an indication is made on the display 22. Further, when the detected analog voltage VD reaches the reference voltage V, a display is performed on the display 22 and the display 23. and,
When the detected analog voltage vl) reaches the reference voltage vc, a display is performed on the display 229, the display 23, and the display 24. In other words, with the display of such a display,
The concentration of the liquid 7 to be measured can be known. Note that this display is performed by lighting or extinguishing each indicator.

Note that by arbitrarily selecting the cut angle α of the end face coated with the reflective film 12a, it is possible to measure the concentration of all liquids 7 to be measured whose refractive index satisfies nM<nco.

Moreover, according to such a configuration, there is no generation of electrical sparks and no influence of electromagnetic induction, so it is possible to realize a liquid concentration sensor suitable for chemical plants and the like that require safety and explosion-proof properties. Furthermore, since the material of the glass rod 12 is quartz, it has excellent chemical resistance.

Furthermore, compared to the conventional example described above, since the glass rod 12 is used as the detection section, the detection section is more durable. Furthermore, since the diameter of the glass rod 12 used as the detection section is large, the light emitting/receiving integrated element 14, in which the light emitting diode 14a as the light emitting section and the photosensor 14b as the light detecting section are integrally provided, is mounted on the holder 13. Since it is provided on the end face of the glass rod 12 via the holder, the structure becomes simple.

Furthermore, since there is no need to use a CPU or ROM, the configuration becomes simple and inexpensive.

Here, FIG. 2 shows the relationship between the alcohol concentration of the liquid to be measured 7 and the output voltage of the photosensor 14b when the apparatus having the above configuration was actually tested under the following conditions.

■Glass rod 12 Material: quartz glass Size: φ3N■, length 30mm α-79@ ■Receiving/emitting integrated element 14 TLP907 (manufactured by Toshiba) ■Measurement liquid 7 Distilled water and alcohol concentration 40% Mixed liquid with whiskey - Room temperature: 20°C As shown in FIG. 2, it was confirmed in experiments that there is a linear relationship between the alcohol concentration and the output voltage of the photosensor 14b.

FIG. 3 is a circuit diagram showing an example of a specific circuit configuration of the present invention. In this figure, R1 to R6 are resistors that constitute a reference voltage generation circuit together with a reference voltage source (not shown).

That is, the reference voltage is created by dividing the reference voltage through resistance. Moreover, 01 to C3 are comparators, the output of the photosensor 14b is applied to the + side input terminal, and the reference voltage from the resistor is applied to each of the − side terminals. D1 to D5 are light emitting diodes (
LED).

When the characteristics of the photosensor 14b are as shown in FIG. 2 above, the reference voltage applied to the comparator C1 is set to 36
30m V, the reference voltage applied to comparator C2 is 35
90mV, the reference voltage applied to comparator C3 is 35El
Om V , the reference voltage applied to comparator C4 is 352
The reference voltage and resistors R1 to R6 are set so that the voltage is 0mV.
Set each resistance value. In this case, the light emitting diode D1 starts emitting light when the power is turned on. When the alcohol concentration of the liquid 7 to be measured exceeds 5%, the output voltage of the photosensor 14b is 38! lOm becomes smaller than V, and the output of comparator C1 becomes low level. Therefore, current flows through the light emitting diode D2 as well as the light emitting diode D1, and the light emitting diode D2 emits light. Similarly, when the alcohol concentration exceeds 10%, the light emitting diodes DI, D2 and D3 emit light, and when the alcohol concentration exceeds 15%, the light emitting diodes Di, D2. D3 and D4 emit light, and when the alcohol concentration exceeds 20%, the light emitting diodes DI, D2. D3
．． D4 and D5 emit light. In this way, the liquid to be measured 7
Since the number of light emitting diodes that emit light changes according to the alcohol concentration, visibility is also extremely good. Furthermore, the resistance R
By changing each resistance value of 1 to R6, each light emitting diode can be turned off or turned off at a desired alcohol concentration.

In the above embodiment, the tip of the glass rod 12 has a beveled cylindrical shape, but the shape is not limited thereto.

For example, as shown in FIG. 4, a reflective film 30a may be provided on the cut surface of a glass rod 30 whose tip is cut into a ■ shape, or as shown in FIG. 5, whose tip is cut into a conical shape. A reflective film 31a is applied to the cut surface of the glass rod 31.
may be provided. Furthermore, as shown in FIG. 6, in the glass rod 12, a part of the light beam is transmitted to the liquid to be measured 7, and the remaining light beam is reflected on the glass surface other than the part A (sensing part) where it is totally reflected. Coat 12b (for example,
Aluminum vapor deposition) may also be performed. By doing so, the performance of the sensor can be improved.

FIG. 7 is an external view showing the external appearance of the liquid concentration sensor according to the present invention. The same numbers are given to the parts that have already been explained, and the explanation will be omitted. In this figure, SW is a main switch, and by operating this switch SW, each part starts operating.

Note that the number of displays in FIG. 1 or the number of light emitting diodes in FIGS. 3 and 7 is not limited to the above embodiment. That is, it is possible to display at a desired resolution by adjusting the number of displays and light emitting diodes.

(Effects of the Invention) As described in detail above, in the present invention, the detection section is formed at one end of the solid rod made of a transparent material, and the light emitting section and the light detection section are formed at the other end of the solid rod. In addition to providing it integrally,
The reference voltage of the reference voltage generation circuit and the detection voltage of the photodetector were compared, and the number of light emitting diodes corresponding to the concentration of the liquid was made to emit light. Therefore, it is possible to realize a liquid concentration sensor that is durable and has a simple configuration.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing one embodiment of the present invention, and FIG.
3 is a circuit diagram showing a specific circuit example of the present invention, and FIGS. 4 to 6 are configuration diagrams showing other examples of the glass rod,
FIG. 7 is an external view showing the external appearance of a liquid concentration sensor, and FIG. 8 is a configuration diagram showing the configuration of a conventional example. 7... Liquid to be measured 12... Glass rod 2a
. . . Reflective film 13 . . Holder 4 .

Claims (1)

[Claims] A reflective film is formed on one end of a solid rod made of a transparent material, and includes a detection section disposed in the liquid to be measured, and a detection section for emitting a light beam to the detection section. a light emitting part provided on the other end side; and a light emitting part provided integrally with the light emitting part on the other end side of the solid rod, which detects the reflected light at the detection part and generates a voltage according to the intensity of the reflected light. a reference voltage generation section that generates a predetermined reference voltage; a comparison section that compares the reference voltage from the reference voltage generation section with the voltage from the photodetection section; and a display section that displays a display according to the comparison result of the comparison section, and displays the display according to the concentration of the liquid to be measured by utilizing the fact that the reflection characteristics at the detection section change depending on the concentration of the liquid to be measured. A liquid concentration sensor characterized in that the liquid concentration sensor is configured to perform the following on the display section.