JPH0792006A - Deterioration detecting method for liquid sensor - Google Patents

Abstract

PURPOSE:To detect whether measurement by a liquid sensor is carried out normally or not. CONSTITUTION:A current to be supplied to a light transmission module 8 is photoelectrically converted into a light, which is transmitted in a transmission path optical fiber 9, and the light is reflected in a sensor unit 10 on the basis of a refractive index of a contact substance, transmitted in a transmission path optical fiber 11, and photoelectrically converted by the light receiving module 12 so as to detect the substance in contact with the sensor unit 10. A current fed to the light transmission module 8 before the use of the sensor is varied by means of a driving circuit 14, the minimum current value to be fed to the light transmission module 8 at the time of starting output from the light receiving module 12 is measured, a supply current to the light transmission module 8 after the use of the sensor is varied so as to be compared with a supply current value at the time of starting output from the light receiving module 12, and consequently, the deterioration in the sensor unit 10 is determined.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting deterioration of a liquid sensor using an optical fiber, and more particularly, to prevent a measurement error due to contamination of the sensor portion of the liquid sensor for detecting the position of the liquid surface. The present invention relates to a liquid sensor deterioration detection method for preventing the deterioration.

[0002]

2. Description of the Related Art Conventionally, there are various types of sensors for detecting the position of the liquid surface of a liquid. However, the sensor head has a sensor head structure in which the ends of two multi-component glass fibers are heated and fused to each other. There is known a liquid detection sensor that detects a substance by the amount of light leaking from the sensor head due to the refractive index of the substance in contact with. This type of liquid detection sensor is useful because it can be applied to a flammable liquid from the viewpoint of safety, since the transmission line and the sensor itself use glass fibers. As such a liquid detection sensor 1, as shown in FIG. 4, the optical fibers 2 and 3 for transmission lines whose outsides are covered with a reinforcing member, and the tips of the optical fibers 2 and 3 for transmission lines are heat-fused to form a spherical shape. And a light emitting section 5 and a light receiving section 6 which are respectively connected to the other ends of the transmission path optical fibers 2 or 3. When the light P ₁ emitted from the light emitting section 5 propagates through the optical fiber 2 and reaches the sensor section 4, most of the light leaks P ₂ from the tip of the sensor section 4 into the gas or liquid in which the sensor section 4 is arranged. , Part of the light P ₃ is reflected, propagates through the optical fiber 3, and is received by the light receiving unit 6.

The amount of light P ₂ leaked by the sensor unit 4 depends on the refractive index of the substance on which the sensor unit 4 is arranged. The greater the refractive index, the greater the amount of leaked light P ₂ and the reflected light P ₃ The light intensity of is reduced. The substance in contact with the sensor unit 4 can be identified by the change in the reflected light amount. Especially for substances with different refractive indices, such as air and water,
As shown in FIG. 5 represented by 00, there is a clear difference in the amount of reflected light, and it is possible to easily determine which substance the sensor unit 4 is in contact with.

[0004]

Such a liquid detection sensor 1
The light emitting unit 5 supplies a constant electric power to the LED or the like, emits a constant amount of light, and receives the light reflected by the sensor unit 4. As shown in FIG. 6, the amount of light received by the light receiving unit 6 of the liquid sensor 1 is a 2 of the amount of light emitted from the light emitting unit 5 during propagation through the optical fiber 2 and becomes a ₂ , and the sensor unit 4 uses the sensor unit 4 the remaining amount a ₃ to light leak by refraction index of the material is in contact
Is propagated in the optical fiber 3, and the amount of light is a ₄ due to the propagation loss of the optical fiber 3. The range that can be detected by the sensor unit 4 can be detected until the light received by the light receiving unit 6 is photoelectrically converted and is no longer output.
In, the substance that leaks light can be detected until the amount of reflected light reaches a ₅ .

However, the leakage of light from the sensor unit 4, that is, the loss of the light amount of the sensor unit 4 changes due to dirt on the sensor head. Therefore, if the detection is performed without noticing the dirt on the sensor head, the detection will be erroneously performed. At present, there is no method to detect the dirt of the sensor head, and therefore, there is no means to judge the correctness of the detection.
The drawback was that maintenance was often required.

The present invention has been made to solve the above-mentioned drawbacks, and it is possible to easily judge whether or not the detection of the liquid sensor is correct, and therefore, the correct detection can always be performed by the liquid sensor. An object of the present invention is to provide a liquid sensor deterioration detection method capable of efficiently detecting deterioration of the liquid sensor without performing unnecessary maintenance.

[0007]

In order to achieve the above object, a method for detecting deterioration of a liquid sensor according to the present invention comprises irradiating light from a light emitting section for photoelectric conversion from the sensor section and refracting a substance in contact with the sensor section. A method for detecting deterioration of a liquid sensor that detects a substance in contact with the sensor unit by receiving light reflected by the light amount that is changed in accordance with the rate, and a light emitting unit prior to using the liquid sensor. The minimum supply current value at which the photoelectrically converted output is obtained by changing the current supplied to the light receiving part is measured in advance, and the current supplied to the light emitting part is changed after the liquid sensor is used and photoelectrically converted by the light receiving part. The deterioration of the sensor unit is detected by comparing the minimum supply current value at which an output is obtained and the minimum supply current value before use.

[0008]

Function: The current supplied to the light emitting portion can be changed. When the amount of light emitted by photoelectric conversion in the light emitting unit is lost in the optical fiber of the transmission line, the sensor unit and received by the light receiving unit, photoelectrically converted and output, to the light emitting unit when output is obtained from the light receiving unit The minimum supply current value of is measured in advance before use. When detecting whether the sensor unit is deteriorated, measure the minimum supply current value to the light emitting unit when the output of the light receiving unit is obtained, and measure the minimum value previously measured when the sensor unit is operating normally before use. Compare with the supply current value. When the value of the supply current to the light emitting unit is larger than the value of the supply current measured in advance, it can be known that abnormal light leakage has occurred in the sensor unit, and it can be detected that the sensor unit is deteriorated.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment to which the liquid sensor deterioration detecting method of the present invention is applied will be described with reference to the drawings. As shown in FIG. 1, the liquid sensor 7 includes an optical transmitter module 8 which is a light emitting unit,
An optical fiber 9 for a transmission line, one end of which is connected to the optical transmission module 8 and which propagates light emitted from the optical transmission module 8,
One end of the optical fiber 9 for transmission path is fused with the other end of the optical fiber 9 for transmission path to form a spherical sensor section 10.
An optical receiving module 12 which is a light receiving unit connected to the other end of the transmission path optical fiber 11 is provided.

The optical fibers 9 and 11 for the transmission line are composed of multi-component glass fibers, and their tips are heat-sealed to each other and formed into a spherical shape similar to the sensor section 4 shown in FIG.
It is what constitutes. The sensor unit 10 causes the light transmitted through the optical fiber 9 for transmission path from the spherical tip to leak through the contacting substance, and reflects the light that does not leak to guide it to the optical fiber 11 for transmission path. The amount of reflected light is changed by the refractive index of the substance in contact.

The optical transmission module 8 which emits the light transmitted through the optical fiber 9 for the transmission path to the sensor unit 10 as described above, supplies power to the LED 13 via the light emitting diode (LED) 13 and the terminal T _a. It has a drive circuit 14 for supplying. The drive circuit 14 is provided with a network 15 in which resistors R ₁ and ˜R _n are connected in series and terminals T ₁ and ˜T _n for switching the connection of the resistors R ₁ and ˜R _n , and the resistor R ₁ selected by the CPU 20. , the terminal T ₁ corresponding to to R _n, through T _n is the power supply Vcc
Connected to. Therefore, a desired current can be supplied to the LED ₁₃ by switching the connection of the terminals T ₁ to T _n .

The LED 13 is connected to the ground through a terminal T _b , photoelectrically converts the current from the terminal T _a, and emits a light amount directly proportional to the supply current. The resistance and the light emission amount of the LED ₁₃ are in inverse proportion to each other, and the light emission amount can be changed by switching the contacts of the resistors R ₁ to R _n . The light receiving module 12 also includes a light receiving element 16 and a photoelectric conversion circuit 17. The light receiving element 16 is the sensor unit 1.
The light reflected at 0 and propagated through the transmission line optical fiber 11 is received, and is photoelectrically converted by the photoelectric conversion circuit 17 into a current corresponding to the amount of light and output. An amplifier 18 that amplifies the photoelectrically converted current is provided, and the amplified current is input to the CPU 20. The current value e ₁ output from the light receiving element 16 by the substance detected by the sensor unit 10 with respect to the constant current supplied to the LED ₁₃ is previously input to the CPU 20, and the current value and the current value sent from the amplifier 18 comparing the e _1, if the current value e ₁ or more, so as to actuate the relay circuit 21. Relay circuit 21
Is provided for switching the connection with a warning sound (not shown), a warning device such as a blinking lamp, or a device that detects a decrease in the position of the liquid level and opens and closes the valve. To be Further, the CPU 20 is provided with a display unit 22 for displaying the current value amplified by the amplifier 18 in order to detect whether the sensor unit 10 of the liquid sensor 7 is operating normally.

When the liquid sensor 7 having such a structure is used to detect a liquid, for example, as shown in FIG. 2, the liquid level in the container 25 in which the air 23 and the liquid 24 are stored is lowered. When detecting, the sensor unit 10 is installed so that the descending interface is located at the lowest allowed position. Now, in the figure, the sensor portion 10 is in the liquid 24. In this way, the terminal T ₁ of the liquid sensor 7 in which the sensor unit 10 is installed,
From the drive circuit 14 connected to the selected terminal from the through T _n predetermined current is supplied to the LED 13. A predetermined current is photoelectrically converted into a predetermined amount of light by the LED 13, and is transmitted through the transmission line optical fiber 9. In the sensor section 10, light leaking from the tip according to the refractive index of the liquid 24 and reflected according to the refractive index passes through the transmission line optical fiber 11 and is received by the light receiving element 16. The current photoelectrically converted by the light receiving element 16 and amplified by the amplifier 18 is input to the CPU 20. C
When the sensor unit 10 is in the liquid, the PU 20 has LE
A current value e ₂ output by photoelectrically converting the light received by the light receiving element 16 due to light leakage from the sensor unit 10 with respect to a constant current supplied to D13 is input in advance.

Here, when the liquid level in the container 25 is lowered and the sensor unit 10 is in the air 23, the CPU 20 e
_When a current value of ₂ or more is input, the relay circuit 21 is operated and the connection is switched to a device or the like for issuing an alarm sound or opening / closing a valve, and a desired operation is performed. When the position of the liquid surface or the like is detected in this way, the sensor unit 10 is normally operating with use, or a substance or the like dispersed in the liquid adheres to the surface and the amount of reflected light at the sensor unit 10 is It is necessary to detect whether deterioration has occurred without corresponding to 10 contacting substances. In the case of detecting the deterioration, the amount of light loss of the liquid sensor 7 is measured in advance before the use of the sensor unit 10 and when the sensor unit 10 is operating normally without any dirt or the like. As shown in FIG. 3, the loss light amount of the liquid sensor 7 is the light amount c photoelectrically converted in the optical transmission module 8.
The light of ₁ is transmitted through the transmission line optical fiber 9 and is received by the sensor unit 10 as the light amount c ₂ , and leaks at the sensor unit 10 and the light amount c ₃ passes through the transmission line optical fiber 11 as reflected light (loss light amount). c ₃ ) It is transmitted to the light receiving module 12, and c ₁ at this time is the amount of light loss of the liquid sensor 7. To measure the amount of lost light, change the supply current to the LED 13 and set L when the output is obtained from the optical receiver module 12.
The minimum current value e ₃ supplied to the ED 13 may be measured. It can be understood that the amount of light obtained by photoelectrically converting the current of the current value e ₃ is the lost light amount and corresponds to the current value e ₃ .
This current value e ₃ is stored in the CPU 20.

When the deterioration of the sensor unit 10 is detected, the CPU
The drive circuit 14 is controlled by 20 and the supply current to the LED 13 is changed. The current supplied to the LED 13 when the output is obtained from the light receiving module 11 is measured. The measured value and the current value e ₃ are compared. If the measured value is e _3, it can be seen that the sensor unit 10 is operating normally. When the measured value is larger than the current value e ₃ , for example, when the light receiving module 12 starts the output for the first time at this time even though the light amount c ₅ corresponding to the supply current is emitted from the LED 13, the sensor unit It can be seen that at 10, the light amount of c ₆ -c ₃ is lost. Therefore, the sensor unit 10 knows that there is abnormal light leakage, and the deterioration of the sensor unit is detected. For the detection of deterioration, the current value e ₃ input to the CPU 20 may be compared with the measured current, and if the value is large, a warning sound or the like may be sounded or displayed on the display unit 22.

In this way, the supply current to the LED is changed, the output from the light receiving module is started, and the supply current at this time is measured, so that the deterioration of the sensor portion can be easily detected. The above description is one example of the present invention, and the present invention is not limited to this. That is, the amount of power supply is not limited to being changed by the CPU, but may be changed by manually changing the volume button or the like. Further, the comparison of the measured values can also be performed using a comparator.

[0017]

As is clear from the above description, according to the liquid sensor deterioration detection method of the present invention, the amount of light lost due to transmission or the like is measured in advance, and the current supplied to the light emitting portion at this time is measured in advance. , It is possible to easily detect the deterioration of the sensor unit by changing the supply current to the light emitting unit and comparing the value of the current supplied to the light emitting unit when the output is obtained from the light receiving unit with a previously measured value. You can

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a liquid sensor to which an embodiment of the present invention is applied.

FIG. 2 is a diagram in which the liquid sensor shown in FIG. 1 is applied to detection of a liquid surface.

FIG. 3 is an explanatory diagram for detecting deterioration of the liquid level sensor shown in FIG.

FIG. 4 is a diagram showing a part of the liquid level sensor shown in FIG. 1 and a conventional example.

FIG. 5 is a diagram showing the relationship between the amount of reflected light and the refractive index.

FIG. 6 is a diagram showing the amount of light loss of the liquid sensor.

[Explanation of symbols]

 7 Liquid sensor 8 Light transmitting module (light emitting section) 10 Sensor section 12 Light receiving module (light receiving section)

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location G02B 6/00

Claims (1)

[Claims] 1. A light-receiving portion for irradiating light from a light-emitting portion that performs photoelectric conversion, and a light-receiving portion receiving the reflected light whose light amount is changed corresponding to the refractive index of a substance in contact with the sensor portion. According to the method of detecting deterioration of a liquid sensor that detects a substance in contact with the sensor unit, the output photoelectrically converted by the light receiving unit by changing the current supplied to the light emitting unit prior to use of the liquid sensor is The minimum supply current value obtained is measured in advance, the minimum supply current value at which the output photoelectrically converted by the light receiving unit is obtained by changing the current supplied to the light emitting unit after the use of the liquid sensor, and before use. A method for detecting deterioration of a liquid sensor, characterized by detecting deterioration of the sensor section by comparing with a minimum supply current value.