JP2507666Y2 - Liquid concentration sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a liquid concentration sensor.

(Prior Art) Conventionally, it is known that the concentration (volume%) of a liquid and the refractive index of the liquid have a certain correlation. Utilizing this correlation, a liquid concentration sensor as shown in FIG. 8 is considered.

In the figure, a transparent solid rod (hereinafter referred to as a glass rod) 1 made of glass is made of quartz and has a refractive index of n1. One end side (front end side) of this glass rod 1 is used as a detection portion, and the end surface is formed in a hemispherical shape. Then, an aluminum reflection film 1a is formed on the end surface by vapor deposition or the like. On the other end side (base end side) of the glass rod 1, a holder 2 is provided with a light emitting / receiving integrated element 3. The integrated light emitting and receiving element 3 includes a light emitting diode 3a as a light emitting portion whose light emitting surface abuts on the other end side end surface of the glass rod 1, and a photo detector as a light detecting portion whose light receiving surface abuts on the other end side end surface. The diode 3b is integrally provided.

The light emitting section drive circuit 4 is a circuit for driving the light emitting diode 3a, and the concentration measuring circuit 5 is a circuit for obtaining a concentration signal of the liquid to be measured 6 having a refractive index of n2 from an analog electric signal obtained from the photodiode 3b. Reference numeral 7 denotes a display unit for displaying the concentration signal output from the concentration measuring circuit 5.

Next, the operation of the above configuration will be described. Light emitting diode 3a
Are driven by the light emitting unit drive circuit 4 to emit a light beam. The light beam emitted from the light emitting diode 3a propagates in the glass rod 1 and is reflected by the reflection film 1a. This reflected beam is incident on the sensing portion A. At the sensing portion A, a part of the light beam is transmitted into the liquid to be measured 6, but the remaining light beam is totally reflected. Then, the totally reflected light beam is incident on the photodiode 3b.

The light beam incident on the photodiode 3b is converted into an analog current signal here. This analog current signal is converted into a concentration signal of the liquid 6 to be measured by the concentration measuring circuit 5 and displayed on the display unit 7.

According to the above configuration, the light amount of the light beam that causes total reflection is a function of the refractive index n2 of the measured liquid 6. On the other hand, since the concentration of the liquid to be measured 6 and the refractive index n2 of the liquid to be measured 6 have a certain correlation, the light amount of the light beam causing total reflection,
That is, the concentration of the liquid 6 to be measured can be measured by detecting the amount of light incident on the photodiode 3b.

(Problems to be Solved by the Invention) In the liquid concentration meter of the conventional example having the above configuration, since the glass rod 1 is exposed to the outside, sunlight, incandescent lamps, and ambient light due to fluorescent lamps enter the glass rod 1. There is a problem that it is incident and accurate density measurement cannot be performed.

Also, since the glass rod 11 is exposed to the outside,
It also has the problem of being fragile.

The present invention has been made in view of the above problems, and its purpose is to minimize the light that enters the internal detection unit through the liquid introduction port without hindering the introduction of the liquid to be measured into the detection unit. Another object of the present invention is to provide a liquid concentration sensor capable of performing accurate measurement and protecting a solid rod.

(Means for Solving the Problems) The present invention for solving the above problems includes a solid rod made of a transparent resin, which is disposed in a liquid to be measured, and a detecting portion formed on one end side of the solid rod. , A light emitting portion which is provided on the other end side of the solid rod and emits a light beam to the reflection film of the detection portion, and a reflection light from the reflection film of the detection portion which is provided on the other end surface of the solid rod. In a liquid sensor having a light detection unit for detecting, a light blocking member that covers the entire solid rod through a space, and a liquid to be measured is detected in the detection unit at a position facing a reflective film of the detection unit. A light-shielding member having a liquid introduction port for introduction is provided.

(Operation) In the liquid sensor of the present invention, when the solid rod and the light-shielding member covering the entire solid rod are arranged in the liquid to be measured, the solid rod and the light-shielding member are covered with a hole formed at a position facing the reflective film. The measurement liquid is introduced, and the concentration of the measurement liquid is detected using the detection unit.

Further, since the light shielding member that covers the entire solid rod through the space is present, the solid rod can be protected and sunlight and disturbance light are less likely to enter the detection unit inside the light shielding member.

In particular, since the liquid introduction port is formed at a position on the light shielding member facing the reflection film of the detection unit, the liquid introduction port does not interfere with the introduction of the liquid to be measured into the detection unit and the internal liquid is introduced through the liquid introduction port. Light entering the detection unit can be minimized, sunlight and ambient light reaching the detection unit can be minimized, and accurate measurement can be performed.

(Embodiment) Next, an embodiment of the present invention will be described with reference to the drawings. First
FIG. 2 is a side view of a partial cross section showing an embodiment of the present invention,
Fig. 1 is a perspective view of Fig. 1, Fig. 3 is a side view of the structure in Fig. 1 with the light-shielding cap removed, Fig. 4 is a plan view of Fig. 3, and Fig. 5 is an assembling of each case in Fig. 3. FIG. 6 is an exploded perspective view for explaining FIG. 6, FIG. 6 is a plan configuration diagram when a cap is inserted and attached in FIG. 4, and FIG.

First, the external structure of the liquid densitometer of this embodiment excluding the cap will be described with reference to FIGS. 3 to 5. In these figures, 11 is a lower case as a case, 12 is an upper case, and 13 is a battery holder for accommodating a battery 14, which is assembled as shown in FIG. 5 to form a liquid concentration sensor housing. There is.

Reference numeral 15 is an acrylic resin (PMMA) rod provided at the tip of the lower case 11. A reflective film 15a is formed on the tip of the rod 15. Reference numeral 16 is a light receiving and emitting integrated element that abuts on the base end of the rod 15, and 17 is a printed circuit board provided in the upper case 12. The integrated light emitting and receiving element 16 is a light receiving section.
It is composed of 16a and a photodetector 16b, and is attached to a printed circuit board 17. 18 is provided on the printed circuit board 17,
It is an LCD display board that displays the measured density value. This LCD
The display plate is visible from the outside through a hole 12a provided in the upper case 12.

As shown in FIG. 6, the liquid densitometer of this embodiment can be fitted with a cap 19 that engages with the lower case 11 when it is not used for measurement.

Next, the light-shielding cap 31 as a light-shielding member that covers the entire rod 15 through a space will be described with reference to FIGS. 1 and 2. The liquid introduction port 3 is provided at the tip of the light-shielding cap 31, that is, at the portion of the solid rod 15 facing the reflection film 15a.
1a is bored (in this embodiment, about φ2 mm). Inside the light-shielding cap 31, a light-shielding chamber 31b in which the detecting portion B of the rod 15 is disposed is formed (in this embodiment, the inner wall surface of the light-shielding cap 31 is painted black). .). Two projections 31c are provided on the inner wall surface of the light shielding cap 31. Further, the base of the light-shielding cap 31 is provided with two air vents 31d.

On the other hand, a step portion 11a is formed at the tip of the lower case 11 so that the base end of the light shielding cap 31 can be fitted therein. Then, the projection 3 of the light-shielding cap 31 is provided on the step portion 11a.
There are provided two recesses 11b with which 1c can be engaged, and two grooves 11c facing the air vent 31d. In this embodiment, the distance between the detecting portion B of the rod 15 and the inner wall surface of the light shielding cap 31 is 1 mm or more.

Next, the electrical configuration of the liquid concentration sensor of this embodiment will be described with reference to FIG. In this figure, reference numeral 21 is a subtraction circuit for adjusting the offset of the analog electric signal from the light emitting / receiving integrated element 16. This offset adjustment is done by a variable resistor (VR
It can be changed in 1). Reference numeral 22 is an amplifier circuit that amplifies the analog signal whose offset has been adjusted.
This amplified analog signal can also be changed by using a variable resistor (VR2). Reference numeral 23 is a comparator that compares the amplified analog signal with a predetermined value, and 24 is an arithmetic circuit and an LCD drive circuit that generate a signal for liquid crystal display and drive the LCD using the generated signal. .

Next, the operation of the above configuration will be described. When the light shielding cap 31 of this liquid concentration sensor is attached and arranged on the liquid to be measured, the liquid to be measured enters through the liquid introduction port 31a. At this time, the shading cap 31 has an air vent 31d and a lower case 11
Since the step 11a is provided with the groove 11c, the liquid to be measured comes in smoothly.

Then, the light emitting section 16a of the light emitting / receiving integrated element 16 is driven by a light emitting section drive circuit (not shown) to emit a light beam. The light beam emitted from this light emitting diode is a rod
The light propagates through 15 and is reflected by the reflection film 15a. This reflected beam enters the detector B (see FIG. 1). At the detection unit B,
Some of the light beams pass through the liquid to be measured, while the rest of the light beams are totally reflected. Then, the totally reflected light beam is incident on the photosensor of the light receiving / emitting integrated element 16.

The light beam incident on the photosensor is converted here into an analog current signal. This analog current signal is
It is converted into a density signal through the circuit explained in the figure and the LCD
It is displayed on the liquid crystal display board 18.

According to the above configuration, the rod 15 as a whole includes the light shielding cap 31.
Since it is covered by, the sunlight and the ambient light from the incandescent lamp and the fluorescent lamp do not enter the rod 15, and accurate measurement can be performed. In particular, since the liquid introduction port 31a is formed at a position on the light-shielding cap 31 that faces the reflection film 15a of the detection unit B, the liquid introduction port does not interfere with the introduction of the liquid to be measured into the detection unit B and It is possible to minimize the amount of light that enters the detection unit B inside the detection unit 31a via 31a, minimize the sunlight and ambient light that reach the detection unit B, and perform accurate measurement.

Further, since the rod 15 is covered with the light-shielding cap 31 through the space, the detecting portion B of the rod 15 is not broken during the measurement.

The present invention is not limited to the above embodiment. In the above embodiment, the light shielding cap 31 having the light shielding chamber 31b formed therein is attached to the lower case 11, but it may be formed integrally with the lower case 11.

(Effects of the Invention) As described above, according to the present invention, a solid rod made of a transparent resin, which is disposed in the liquid to be measured, and a detecting portion formed on one end side of the solid rod. , A light emitting portion which is provided on the other end side of the solid rod and emits a light beam to the reflection film of the detection portion, and a reflection light from the reflection film of the detection portion which is provided on the other end surface of the solid rod. In a liquid sensor having a light detection unit for detecting, a light shielding member that covers the entire solid rod through a space, and a liquid to be measured is detected in the detection unit at a position facing a reflective film of the detection unit. A light-shielding member having a liquid introduction port for introduction was provided.

Therefore, since the light blocking member that covers the entire solid rod through the space is present, the solid rod can be protected, and sunlight and ambient light are less likely to enter the detection unit inside the light blocking member.

In particular, since the liquid introduction port is formed at a position on the light shielding member facing the reflection film of the detection unit, the liquid introduction port does not interfere with the introduction of the liquid to be measured into the detection unit and the internal liquid is introduced through the liquid introduction port. Light entering the detection unit can be minimized, sunlight and ambient light reaching the detection unit can be minimized, and accurate measurement can be performed.

[Brief description of drawings]

1 is a partial sectional side view showing an embodiment of the present invention, FIG. 2 is a perspective view of FIG. 1, FIG. 3 is a side view of FIG. 1 with a light-shielding cap removed, and FIG. Fig. 3 is a plan configuration diagram, Fig. 5 is an exploded perspective view for explaining the assembling of each case in Fig. 3, Fig. 6 is a plan configuration diagram when a cap is inserted in Fig. 4, and Fig. 7 is FIG. 8 is a block diagram for electrically explaining the liquid concentration sensor of the present embodiment, and FIG. 8 is a configuration diagram for explaining a conventional liquid concentration sensor. In these figures, 11: lower case (case) 12; upper case, 15; solid rod 16a; light emitting part, 16b; photodetection part 31a; liquid inlet port, 31b; light shielding chamber B; detection part

Claims (1)

(57) [Scope of utility model registration request] 1. A solid rod (15) made of a transparent resin, which is disposed in a liquid to be measured, and a detection section (B) formed at one end side of the solid rod (15).
And a light emitting part (1) provided on the other end side of the solid rod (15) for emitting a light beam to the reflecting film (15a) of the detecting part (B).
6a), and a light concentration sensor (16b) provided on the other end surface of the solid rod (15) for detecting the reflected light from the reflection film (15a) of the detection unit (B). In the light-shielding member that covers the entire solid rod (15) through a space, the liquid to be measured is detected at the detection unit (B) at a position facing the reflection film (15a) of the detection unit (B). A liquid concentration sensor comprising a light-shielding member having a liquid introduction port (31a) to be introduced therein.