JPS62177417A - Liquid level detector - Google Patents

Abstract

PURPOSE:To detect a liquid level with higher order by feeding back the output light intensity from a light source and comparing an output signal from a light source driving circuit with a signal from a detection part for measurement and calculating it. CONSTITUTION:When a driving command signal is sent from a comparison circuit 11 to a LED driving circuit 13, an intense optical signal is outputted and inputted to a sensor head 23 for reference and a sensor head (detecting part) 25 for the signal. Then, the signal inputted to the head 23 detecting part is converted into the electrical signal in accordance with the intensity of the optical signal with a reference photodetection means 1 (a ferrule 3, etc.) and afterwards, amplified 9 and compared with an output value from a reference voltage circuit 7 with the circuit 11 and calculated therewith. On the other hand, the signal inputted to the head 25 is converted into the electrical signal in accordance with the intensity of the optical signal with a photodetection means 29 (a ferrule 27, etc.) for the signal and afterwards, amplified 33 and given to a comparison circuit 35 and compared with an output signal value from the circuit and calculated therewith. Then, arithmetic operation is performed based on output signal values from the amplification circuit 33 and the circuit 13 and the quantity of loss in the head 25 is calculated, by which the liquid level can be detected with high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION -2 The present invention generally relates to a liquid level detection device, and more particularly to a liquid level detection device for detecting the level of a liquid such as wood or oil stored in a storage tank by optical means. This invention relates to a detection device.

A light source such as a light emitting diode (hereinafter referred to as rLEDJ), a semiconductor laser (hereinafter referred to as rLDJ), a He-Me laser, and an optical liquid level detector.

A liquid level detection device that detects liquid level using optical means consisting of an optical transmission line such as an optical fiber and a light receiving element such as an avalanche photodiode (hereinafter referred to as rAPD) and a PIN photodiode (hereinafter referred to as rPINPD) is a In general, the optical transmission loss at the liquid level detection section is measured by detecting the magnitude of the electrical signal output from the light receiving element according to the light intensity received by the light receiving element. The liquid level detection section formed at the end of the device determines whether the device is in the air or in the liquid.

The child actor who recognizes the transmission loss of light in the liquid level detection section 111 by detecting the magnitude of the electrical signal mentioned above is 1.
As is well known, electronic circuits are used as signal amplification means to amplify the minute signals output from the light receiving element, comparators etc. are used as determination means to determine the magnitude of the signal output from the signal amplification means. Examples include various electronic circuit devices.

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- By the way, in the conventional liquid level detection device having the above-mentioned structure, a device having a constant current type stabilizing power supply circuit was used as a drive circuit as a drive means for driving a light source. Therefore, fluctuations in the light source output caused by temperature changes in electronic circuit elements, etc. become large. For example, when the element temperature changes in the range of θ℃ to 50℃, the output light intensity from the light source also increases by ±0.2 dB or more. It is difficult to control fluctuations in the output power, and the fluctuations in the output directly result in detection errors.

Also, loss changes due to light leakage that occurs at curved portions of optical fibers that serve as optical transmission lines for transmitting light output from light sources! ! Since it is difficult to eliminate lI (usually about ±0.1 dB), the optical signal from the liquid level detection section with the above-mentioned gh factor added may be input to the light receiving element. becomes.

Furthermore, the circuit components that make up the photodetector and the various electronic circuit elements that serve as signal processing means, such as amplifying the signal output from the photodetector, are subject to fluctuations of about ±0.05dB due to temperature changes. Since the output varies within the range, it is necessary to stabilize the output light intensity from the light source, as well as countermeasures against fluctuations in the optical signal due to loss fluctuations due to light leakage, etc. that occur in the optical transmission path, and temperature fluctuations in the signal processing means. It would have been impossible to detect the liquid level with higher accuracy without taking measures against output fluctuations due to

1. The present invention was devised to improve the problems of the prior art as described above, and its purpose is to stabilize the output light intensity from the light source and to reduce the transmission occurring in the optical transmission line. It is an object of the present invention to provide a liquid level detection device that can perform liquid level detection with higher accuracy by taking predetermined measures against fluctuations in the optical signal inside and fluctuations in the output of the signal processing means.

8' and - The above object is achieved by the liquid level detection device according to the present invention. 28' In short, the present invention includes: a measuring detector for detecting a liquid level that receives a received optical signal and outputs an optical signal according to the surrounding medium; and a measuring detector in the vicinity of the measuring detector. A reference detecting section is arranged and receives a given optical signal and outputs a reference optical signal, and the measuring detecting section and the reference detecting section are connected to a single light source means and are connected to each other. Output from the reference detection section via a plurality of optical transmission line means arranged under substantially the same IIi setting conditions and an optical transmission line means connected to a preset signal reference value and the reference detection section. and a correction means for determining a difference value between the signal and the optical/electrical converted signal, and feedback-controlling the driving means for driving the light source means based on the difference A4; A liquid that identifies the liquid level by comparing and calculating an output signal from the driving means and a photo-to-electrically converted signal output from the measuring detecting section via an optical transmission line means connected to the measuring detecting section. This is a liquid level detection device characterized by having a surface identification means.

Support 1 The present invention will be explained in detail below with reference to one drawing.

FIG. 1 is a schematic diagram showing the configuration of a liquid level detection device according to an embodiment of the present invention. In FIG. 1, a measurement detection section, that is, a signal sensor head 25, and a reference detection section, that is, a reference sensor head 23, are both housed in a housing, that is, a sensor head section 3.
It is held within 9. The details of the configuration of the sensor head section 39 are as shown in FIG. 2, for example. That is,
The sensor head section 39 includes a bushing section 55 and a holder section 5.
7. It consists of a shielding part 59 with an opening 11 near the center, and the bushing part 55 and the shielding part I'i! 159 are assembled at both ends of the holder portion 57, respectively. The bushing portion 55 is connected to an optical transmission path means, that is, an optical fiber 19.21.
The optical fiber cable 47 having the configuration shown in FIG. 3 is held from its outer circumferential side. The holder part 57 has a reference holder constructed by the optical fiber core wire 81.63 of the optical fiber 19.21 extended from the bushing part 55 and the optical fiber core wire 63 from which the coating is removed. and a signal sensor head 25 that faces the opening of the shielding part 59 and is made of an optical fiber from which the coating of the optical fiber core wire 61 has been removed. The reference sensor head 23 receives a signal from the light source, that is, the LED 15.
5 detects fluctuations in the optical signal such as transmission loss fluctuations caused by various factors specific to optical fibers,
It is provided to compensate for fluctuations in the optical signal, and is arranged as close to the signal sensor head 25 as possible. The periphery of the reference sensor head 23 is a cavity through which gas (for example, air) having a lower refractive index than the cladding 45 of the optical fiber can freely enter and exit. Among the optical fibers 19 and 21, the optical fiber 21t on which the reference sensor head 23 is formed
7) Jj connects the LED 15 and the reference light receiving means 1, while the optical fiber 19 on which the signal sensor head 25 is formed connects the LED 15 and the signal light receiving means 29. Connected. The optical fiber 19.21 is an optical fiber cable 47 having a configuration as shown in FIG. . That is, the optical fiber cable 47 has optical fibers 19 and 21, which are composed of optical fiber cores in which the outer periphery of an optical fiber consisting of a core and a cladding is coated concentrically with, for example, an ultraviolet curable silicone resin member, facing each other. Optical fibers twisted together and twisted together facing each other/＜19
．． 21 is an elastic adhesive such as silicone rubber adhesive 5
Glue and fix using 3. Then, the optical fiber 19.21 adhesively fixed with the adhesive 53 is covered with, for example, a polyvinyl chloride sheath (i.e., PVC sheath) 49 without being tightly attached to its outer peripheral surface, and the optical fiber 19.21 and the PVC sheath are A tension member 51 made of polyaramid fiber is disposed in the space formed by the tension member 49.

The reason for configuring the optical fiber cable 47 as described above is to prevent the optical fibers 19 and 21 from bending due to contraction and expansion of the covering member such as the PVC sheath 49! This is to compensate for fluctuations in transmission loss of optical signals by minimizing the noise as much as possible.

On the other hand, the optical fiber 19.21 is connected to the light source connector ferrule 14, which is shown in an enlarged view in FIG. are connected via. The light input end face of the optical splitter 17 is arranged with respect to the center of the end face as shown in FIG. so that the core 41.4 is approximately symmetrical.
3 and a cladding 45 are arranged.

The reference light-receiving means 1 includes a reference light-receiving connector ferrule 3 that holds the end of an optical fiber 21 connected to a reference sensor head 23, and a light-receiving element disposed in close proximity to the reference light-receiving connector ferrule 3. It has a PIN photodiode 5 as a PIN photodiode 5, performs optical/electrical conversion on the optical signal output from the reference sensor head 23, and outputs it to the amplifier circuit 9.

Similarly, the signal light receiving means 29 also includes the signal sensor head 25.
It has a signal i′f light-receiving connector ferrule 27 that holds the end of the optical fiber 19 connected to the signal i'f connector ferrule 27, and a PIN photodiode 31 as a light-receiving element disposed in close proximity to the signal i'f light-receiving connector ferrule 27. The optical signal outputted from the optical sensor head 25 is subjected to optical/electrical conversion and outputted to the amplifier circuit 33.

The correction means includes a reference voltage circuit 7, an amplifier circuit 9 . It consists of a comparison circuit 11.

The liquid level identification means is an amplifier circuit 33. It is composed of a comparison circuit 35. The amplifier circuit 9 and the amplifier circuit 35 have the ability to cancel out output fluctuations (usually within a range of about ±0.05 dB) from each other even if the electronic circuit elements that make up the amplifier circuit 33 generate output fluctuations (usually within a range of about ±0.05 dB). Identical circuit elements are used where possible. The comparison circuit 11 is
The signal output from the amplifier circuit 9 and the voltage reference value output from the reference voltage circuit 7 are compared, and the difference between the output signal from the amplifier circuit 9 and the voltage reference value output from the reference voltage circuit 7 is calculated. The drive command signal to be output to the LED drive circuit 13 is adjusted to m so that it becomes O. The comparison circuit 35 compares and calculates the signal output from the amplifier circuit 33 and the output signal from the LED drive circuit 13 whose drive is sequentially adjusted by the comparison circuit 11, and compares the output signal from the amplifier circuit 33 and the LED drive circuit. The liquid level is determined by calculating the output signal from LED 13 (the difference between the amount of incident light entering the signal sensor head 25 from the LED l 5 and the output light output from the signal sensor head, that is, the loss result of the optical signal). For example, a digital display device is used as the display unit 37 for detecting the liquid level, and digitally displays data representing the liquid level according to the display output from the comparison circuit 35.

42 In the liquid level detection device having the configuration as described above, the LED [! ! By outputting the drive command signal to the 1 circuit 13, the LHD 1 5 outputs an optical signal having an intensity corresponding to the drive command signal.

The optical signal is transmitted through the optical splitter 17 and the optical fibers 19 and 21 to the reference sensor head F while causing approximately the same optical transmission loss.
13. The signal is input to the signal sensor head 25. The optical signal 1) input to the reference sensor head 23 is given to the reference light receiving means 1 while causing a certain transmission loss in the reference sensor head 23, and is outputted from the reference sensor head 23 in the reference light receiving means I. After the optical signal is converted into an electrical signal according to the intensity of the optical signal, it is output to the amplifier circuit 9. The electrical signal output from the reference light receiving means 1 is amplified by the amplifier circuit 9 and then input to the comparison circuit 11, where it is compared with the output value from the reference voltage circuit 7. As a result of the comparison operation, the difference value between the two is 0.
The output signal from the LED drive circuit 13 is feedback-controlled by the drive command signal from the comparator circuit 11 so that the output light intensity from the LED l 5 is stabilized.

On the other hand, the optical signal input to the signal sensor head 25 is
When the signal sensor head 25 is below the liquid level and when it is above the liquid level, it is applied to the signal light receiving means 29 as an optical signal having a different transmission loss, and the signal light receiving means 29 receives the signal. After being converted into an electrical signal according to the intensity of the optical signal output from the sensor head 25, the optical signal is output to the amplifier circuit 33. The electric signal output from the signal light receiving means 29 is amplified in the amplifier circuit 33 and then given to the comparison circuit 35, where it is compared with the signal value output from the LED drive circuit 13 which is feedback-controlled by the comparison circuit 11. be done.

As a result of the comparison operation, the output signal value from the amplifier circuit 33 and the output signal value from the LED drive circuit 13 are calculated,
By determining the amount of loss in the signal sensor head 25, the liquid level is detected and output to be displayed on the display unit 37.

As explained above, according to one embodiment according to the present invention,
A reference sensor head 23 is disposed near the signal sensor head 25 held by the housing, and
The optical fiber 19 connecting the LED 15 and the signal sensor head 25 and the optical fiber 21 connecting the LED 15 and the reference sensor head 23 are arranged under substantially the same installation conditions, and the optical fiber 19.21 is connected to the LED connection part. They are heat-sealed and arranged so as to be approximately symmetrical with respect to the center of the cut cross section of the connection part, and are twisted so as to face each other in the vicinity of the signal sensor head 25 and the reference sensor head 23. ,
Since it was decided to be constructed by bonding with adhesive, L
In order to detect transmission loss fluctuations caused by factors specific to the optical fiber in the section from the ED l 5 to the signal sensor head 25 with high precision, feedback control of the output light intensity is possible with higher precision than in the conventional example. It is tE.

Furthermore, since the amplifier circuits 9 and 33 provided in the correction means and the liquid level identification means are constructed of the same circuit element, it is possible to cancel fluctuations in the output signal from the amplifier circuits 9 and 33 due to temperature fluctuations. Because it became possible,
It is now possible to detect even minute fluctuations in liquid level, which were previously difficult to measure.

As explained above, according to the present invention, the optical transmission path means for connecting the light source and the measurement detection section, and the optical transmission path means for connecting the light source and the reference detection section are abbreviated as Install under the same installation conditions and drive the light source according to the optical/electrical converted signal output from the reference detection section! ! The output light intensity from the light source is feedback-controlled by adjusting the output signal from the l f first stage, and the output signal from the light source driving means is compared with the optical/electrical converted signal output from the measurement detector. Since the liquid level is identified by this method, it is possible to provide a liquid level detection device that can perform liquid level detection with higher accuracy than conventional devices.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the configuration of a liquid level detection device according to an embodiment of the present invention. FIG. 2 is an axial cross-sectional view of a sensor head section used as a reference detection section and a measurement detection section constituting the liquid level detection device shown in FIG. 1. FIG. 3 is a cutaway sectional view of the optical transmission path means constituting the liquid level detection device shown in FIG. 1. FIG. 4 is a sectional view of the light source means constituting the liquid level detection device shown in FIG. 1. FIG. 5 is a view showing an end face of the optical transmission line means at the connection portion that connects the light source means and the optical transmission line means shown in FIG. 4. 11: Comparison circuit 13: LED drive circuit 15: LED 16: Light source means 19: Optical fiber 21: Optical fiber 23: Reference sensor head 25: Signal sensor head 35: Comparison circuit 8; 3 figure procedure correction! # (Spontaneous) September 30, 1985 Patent Application No. 17774 of 1988 Name of the invention Person who corrects liquid detection device

Claims (1)

[Claims] 1) A measurement detection section for detecting a liquid level that receives a given optical signal and outputs an optical signal according to the surrounding medium, and a measurement detection section disposed near the measurement detection section. A reference detection unit that receives a given optical signal and outputs a reference optical signal, the measurement detection unit and reference detection unit, and a single light source means are connected, and are connected to each other. The light output from the reference detection section is transmitted through a plurality of optical transmission line means arranged under the same installation conditions, a preset signal reference value, and an optical transmission line means connected to the reference detection section. a correction means for determining a difference value between the signal and the electrically converted signal, and feedback-controlling a driving means for driving the light source means based on the difference value; The liquid level is identified by comparing and calculating the output signal from the measuring detecting section with a photo-to-electrically converted signal output from the measuring detecting section via an optical transmission line means connected to the measuring detecting section. A liquid level detection device comprising: identification means. 2) The optical transmission line means is formed by twisting a plurality of optical transmission line means facing each other and adhering them with an adhesive, and attaching the plurality of optical transmission line means adhered with an adhesive to the outer periphery of the optical transmission line means. 2. The liquid level detection device according to claim 1, wherein the liquid level detection device is covered with a covering member with a gap between the surface and the surface. 3) The optical transmission line means has a core such that, at the connection part with the light source means, the core of the optical fiber forming the optical transmission line means is approximately relative to the center of the cut cross section of the optical transmission line means at the connection part. 2. The liquid level detection device according to claim 1, wherein the liquid level detection device is symmetrically fused and arranged. 4) The liquid level detection device according to claim 1, wherein the measurement detection section and the reference detection section are both held by a housing. 5) The liquid level detection device according to claim 1, wherein the correction means and the liquid level identification means are provided with signal amplification means made of the same circuit element.