JPH03146825A - Interface detector - Google Patents

Abstract

PURPOSE:To surely detect an interface even when few specific gravity or impedance between upper and lower layers exists by receiving modulated light projected from the inside of a guide pipe on one side to that of a guide pipe on the other side, and detecting the interface by observing the output level of a light receiving means with a modulation light reception circuit. CONSTITUTION:A pair of guide pipes 22, 24 are provided with translucent property, and are arranged keeping a prescribed gap. Also, a modulation light driving circuit drives a light emitting means by outputting a modulation signal. The light receiving means receives the modulated light projected from the inside of the pipe 22 on one side to the pipe 24 on the other side via the pipes 22, 24 and an object to be inspected. The modulation light reception circuit detects the interface 8 with the interface detector 10 by observing the output level of the light receiving means. Therefore, since there is no influence on the transmittancy of the upper layer 4 and the lower layer 6 even when the specific gravity or the impedance of the upper layer 4 and the lower layer 6 is changed, the interface 8 can be surely detected. Similarly, when small difference in the specific gravity or impedance between the upper layer 4 and the lower layer 6 exists, the interface 8 can be detected.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to the interface between a reference layer and a comparison layer of a fluid to be inspected, such as a liquid, gas, or powder, which has a difference in light transmittance. The present invention relates to an interface detection device for detecting.

[Prior Art] In the first conventional interface detection device, the specific gravity of each interface formed between the reference layer and the comparison layer of the fluid to be detected is measured, and detection is performed based on the difference in specific gravity. I have to.

In addition, in the conventional second interface detection device, the electrical characteristics of the impedance such as capacitance and conductance of each interface formed between the reference layer and the comparison layer of the fluid to be detected are measured. Detection is performed based on the difference in impedance.

[Problems to be Solved by the Invention] However, in the first conventional technique, it is difficult to detect the interface when the difference in specific gravity between the reference layer and the comparison layer is small.

In the second conventional technique, it is difficult to detect the interface when the difference in impedance between the reference layer and the comparison layer is minute or the same. Furthermore, if the specific gravity or impedance changes due to a change in the components or properties of the reference layer or comparison layer, it is difficult to detect the interface.

The present invention solves the above-mentioned technical problem, and even when the specific gravity or impedance of the reference layer or the comparison layer changes, or when there is not much difference in the specific gravity or impedance between the reference layer and the comparison layer, An object of the present invention is to provide an interface detection device that can reliably detect an interface.

[Means for Solving the Problem] - The interface detection device according to claim (1) detects an interface formed by two layers of a fluid body to be detected, a reference layer and a comparison layer, which have different light transmittances. A pair of light-transmitting guide pipes arranged at a predetermined interval, a light emitting means, and a modulated light drive circuit that outputs a modulation signal and modulates and drives the light emitting means. , a light receiving means for receiving modulated light projected from inside one guide pipe into the inside of the other guide pipe through both guide pipes and the inspection object; and a modulated light for detecting an interface by looking at the output level of the light receiving means. The device is characterized in that it includes a light receiving circuit;

The interface detection device of claim (2) is the same as that of claim (1), wherein the one guide pipe is provided with a light emitting means, and the other guide pipe is provided with a light receiving means, the optical axes of which are set to coincide with each other. A modulated light output circuit and a modulated light receiving circuit are installed outside the guide pipe, and a high frequency It is characterized by being electrically connected by a cable.

The interface detection device according to claim (3) is the same as that according to claim (1), further comprising: a light emitting means, a light receiving means, a modulated light output circuit, and a modulated light receiving circuit outside the guide pipe, and a light emitting means output from the light emitting means. A light receiving means transmits and projects the modulated light to a predetermined fixed position in the one guide pipe, and receives the modulated light at a predetermined fixed position in the other guide pipe where the optical axis coincides with the light. It is characterized by the provision of an optical fiber cable that transmits data up to

The interface detection device according to claim (4) detects an interface between two layers of a fluid to be detected, a reference layer and a comparative layer, which have different light transmittances, and a pair of guide pipes arranged at a predetermined interval over an interface detection range; a light emitting means; a modulated light drive circuit that outputs a modulation signal and modulates and drives the light emitting means; both guide pipes. and a light receiving means for receiving the modulated light projected from inside one guide pipe to the inside of the other guide pipe through the inspection object, and an optical axis between both guide pipes of the light emitting means and the light receiving means. Modulated light that determines the difference between the output level of the moving means to be moved, the light receiving means, and a predetermined reference output level corresponding to the interface, and drives the moving means according to the determined difference so that the difference disappears. A light-receiving calculation circuit, and is characterized in that the output level of the light-receiving means in the reference layer and in the comparison layer is measured in advance, and the interface is detected based on the output level of the light-receiving means. .

The interface detection device of claim (5) is the same as that of claim (4), characterized in that it includes an indicating means for indicating the position of the interface.

9- The interface detection device of claim (6) is defined by claim (4) or (
5), a light emitting means is provided on one of the guide pipes;
and a light receiving means is movably inserted into the other guide pipe with its optical axis aligned, and a modulated light output circuit and a modulated light reception calculation circuit are provided outside the guide pipe, and the output of the modulated light output circuit and the light emitting means are provided. The device is characterized in that a high-frequency cable is used to electrically connect the input of the modulated light receiving calculation circuit and the light receiving means.

The interface detection device according to claim (7) is the one according to claim (4) or (5) of λ111, and further includes a light emitting means outside the guide pipe.
In addition to providing a light receiving means, a modulated light output circuit, and a modulated light receiving calculation circuit, the modulated light outputted from the light emitting means is movably transmitted and projected into the one guide pipe, and the optical axis is The present invention is characterized in that an optical fiber cable is provided which transmits the modulated light received movably within the other guide pipe to the light receiving means.

0 The interface detection device according to claim (8) detects an interface between two layers of a fluid to be detected that have different light transmittances, and uses modulated light modulated at a predetermined frequency. The present invention is characterized in that the modulated light that is projected and passed through the inspection object is received, and the interface is detected based on a change in the level of the received light.

[Function] In the interface detection device according to claim (1), the pair of guide pipes have translucency and are arranged at a predetermined interval. The modulated light drive circuit outputs a modulation signal to modulate and drive the light emitting means. The light receiving means receives modulated light projected from inside one guide pipe to inside the other guide pipe via both guide pipes and the object to be inspected. The modulated light receiving circuit detects the interface by looking at the output level of the light receiving means.

Therefore, even if the specific gravity or impedance of the reference layer or comparison layer changes, the translucency of the reference layer and comparison layer is not affected, so the interface can be reliably detected. Similarly, even when there is not much difference in specific gravity or impedance between the reference layer and the comparison layer, the interface can be reliably detected.

Moreover, since the light emitting means is modulated and driven, the intensity of the modulated light projected from the light emitting means can be increased. When considering heat resistance, corrosion resistance, adhesion resistance, dust resistance, etc., it may be necessary to use a material with poor translucency for the guide pipe, such as FEP, or the translucency of the object to be inspected. Even when it is necessary to detect an interface between two objects with low intensity, the highly intense modulated light can pass through these guide pipes and the object to be inspected. Therefore, even in these cases, the interface can be easily detected.

Furthermore, since modulated light is used, the S/N ratio can be increased, and the system can be made resistant to noise such as disturbance light.

In the interface detection device according to claim (4), the moving means includes:
The optical axis between the guide pipes of the light emitting means and the light receiving means is integrally moved. The modulated light reception calculation circuit determines the difference between the output level of the light receiving means and a predetermined reference output level corresponding to the interface, and drives the moving means according to the determined difference so that the difference disappears.

Therefore, even if the specific gravity or impedance of the reference layer or comparison layer changes, the translucency of the reference layer and comparison layer is not affected, so the interface can be reliably detected. Similarly, even when there is not much difference in specific gravity or impedance between the reference layer and the comparison layer, the interface can be reliably detected. Further, the light emitting means and the light receiving means can move to follow the interface and detect the interface.

Moreover, since the light emitting means is modulated and driven, the intensity of the modulated light projected from the light emitting means can be increased. When considering heat resistance, corrosion resistance, adhesion resistance, dust resistance, etc., there may be cases where the guide pipe must be made of a material with poor translucency, such as FEP3, or the material to be inspected. Even when it is necessary to detect an interface between objects that have poor light transmittance, strong modulated light can pass through these guide pipes and the object to be inspected. Therefore, even in these cases, the interface can be easily detected.

Furthermore, since modulated light is used, the S/N ratio can be increased, and the system can be made resistant to noise such as disturbance light.

In the interface detection device of claim (5), claim (4)
The method further includes indicating means for indicating the position of the interface.

Therefore, the position of the interface can be easily known.

In the interface detection device according to claim (2) or (6),
In the device according to claim (1), (4), or (5), the modulated light output circuit and the modulated light receiving circuit or the modulated light output circuit and the modulated light receiving calculation circuit are provided outside the guide pipe.

Therefore, even if the test target is at a high or low temperature, the modulated light output circuit and the modulated light receiver circuit or the modulated light output circuit and the modulated light receiver calculation circuit operate reliably without being affected by the temperature of the test target. be able to.

In the interface detection device according to claim (3) or (7),
In claim (1), (4) or (5), the light emitting means, the light receiving means, the modulated light output circuit and the modulated light receiving circuit, or the light emitting means, the light receiving means, the modulated light output circuit and the modulated light receiving calculation circuit are , installed outside the guide pipe.

Therefore, even if the test target is high or low temperature, the light emitting means, the light receiving means, the modulated light output circuit and the modulated light receiving circuit or the light emitting means, the light receiving means, the modulated light output circuit and the The modulated light reception calculation circuit can operate reliably.

The interface detection device according to claim 8 detects an interface between two layers of fluid having different light transmittances to be detected. This device outputs modulated light modulated at a predetermined frequency. The modulated light that is projected and passes through the inspection target is received. The interface is detected by a change in the level of the received light.

Therefore, even if the specific gravity or impedance of the two layers changes, the translucency of the two layers is not affected, so the interface can be reliably detected.

Similarly, even if there is not much difference in specific gravity or impedance between the two layers, the interface can be reliably detected.

Moreover, since modulated light is emitted from the light projecting means, the intensity of the modulated light projected from the light projecting means can be increased. Even when it is necessary to detect an interface between objects to be inspected whose light transmittance is not very good, the highly intense modulated light can be transmitted through the objects to be inspected. Therefore, even in these cases, the interface can be easily detected.

Furthermore, since modulated light is used, the S/N ratio can be increased, and the system can be made resistant to noise such as disturbance light.

[Example] The present invention will be explained in detail below with reference to the drawings.

FIG. 1 shows an interface detection device according to an embodiment of the present invention.
The figure is a diagram showing details of the level detection probe section 12,
FIG. 3 is a circuit diagram of the level detection amplifier section 14.

In the storage tank 2, an upper layer 4, which is a reference layer to be detected, and a lower layer 6, which is a comparison layer, are stored. This upper layer 4
The interface 8 formed between the upper layer and the lower layer 6 is detected by the interface detection device 110. In this embodiment, both the upper layer 4 and the lower layer 6 have translucency, but the upper layer 4 is more transparent than the lower layer 6.
The description will be made on the assumption that the interface 8 has better translucency, and the upper layer 4 is a liquid and the lower layer 6 is a precipitate.

The interface detection device 10 includes a level detection probe unit 12 provided in the storage tank 2 to detect an interface 8 within the storage tank 2, and a level detection amplifier unit 1 provided outside the storage tank 2 (for example, remotely).
4.

FIG. 2 shows details of the level detection probe section 12.

The flange 2o of the level detection probe section 12 is provided with holes 2a and 20b. The guide pipes 22 and 24 are
The O-ring 26 is fitted and inserted vertically into the storage 17-note type 2 through the holes 20a, 20b at regular intervals.

The guide pipes 22 and 24 are long enough to cover the range in which the interface 8 is to be detected. Guide pipe 22.
24 is approximately cylindrical, and its upper end is open;
Its lower end is sealed. The guide pipes 22 and 24 are
For example, polytetrafluoroethylene (so-called Teflon)-based PFA or FEP is used and has translucency. However, these PFA and FEP are semitransparent and do not have very good light transmittance. The guide pipes 22 and 24 have good properties in terms of heat resistance, corrosion resistance, adhesion resistance, and the like.

Inside the guide pipe 22.24 is a holding pipe 28.30.
are inserted respectively. The holding pipe 28.30 consists of 5US304, for example. The holding pipe 28.30 is
A length that covers the range in which the interface 8 is detected is used. At the tip of the holding pipe 28.30, there is a retainer 32.
34 are fixed respectively. The cages 32 and 34 are made of, for example, FRP. A light emitting diode 36 that outputs a laser beam as a light emitting means and a photodiode 38 as a light receiving means are respectively fixed to the side surfaces of the holders 32 and 34. Note that the light emitting diode 36 may be a normal light emitting diode that outputs a plurality of spectral components. The length and orientation of the holding pipes 28, 30 are adjusted so that the optical axes of the light emitting diode 36 and the photodiode 38 coincide. When the optical axes of the light emitting diode 36 and the photodiode 38 coincide, the guide pipe 22, 24 and the holding pipe 2
8.30 are fastened with screws 40.42, respectively.

A case cover 44 is provided on the flange 20.

A terminal plate 46 is provided on the case cover 44 . A lead terminal 36a of the light emitting diode 36 is connected to the lower end of a high frequency cable 48. The upper end of the high frequency cable 48 is connected to an input terminal 50 of the terminal board 46. A lead terminal 38a of the photodiode 38 is connected to the lower end of the high frequency cable 52. The upper end of the high frequency cable 52 is connected to an output terminal 54 of the terminal board 46.

The flange 56 provided on the upper part of the storage tank 2 and the flange 20 of the level detection probe section 12 are fixed by bolting. The optical axes of the light emitting diode 36 and the photodiode 38 are fixedly arranged at a position where the interface 8 is to be detected, and are arranged parallel to the interface 8. The guide pipes 22, 24 and the flange 20 are airtightly connected by an O-ring 26.

Guide pipe 22, 24 and flange 20 are O-ring 2
6, and the flange 56 and the flange 20 are fixed by bolting, so that the inside of the storage tank 2 and the outside of the storage tank 2 are cut off from each other in terms of ventilation. Also,
Since the tips of the guide pipes 22 and 24 are sealed,
No object to be detected enters the guide pipes 22,24.

Therefore, even if the object to be inspected is corrosive or harmful gas is generated from the object to be inspected, the object to be inspected or the gas will not enter the guide pipes 22 and 24 or come out of the storage tank 2. do not have.

FIG. 3 shows a circuit diagram of the level detection amplifier section 14. The level detection amplifier unit 14 includes a modulated light driving circuit 62 and a modulated light receiving circuit 64 provided inside the casing 60 , and a terminal plate 66 provided in the casing 60 .

The modulated light drive circuit 62 includes a pulse generation circuit 68 and an amplifier circuit 70. The pulse generation circuit 68 is, for example, a fourth
As shown in Figure (1), a 20kHz pulse signal is output. The duty ratio of this pulse signal is set so that the time during which the light emitting diode 36 is lit is shortened. This pulse signal is amplified by an amplifier circuit 70. This amplification factor is set so that the forward current increases within the rated range when the light emitting diode 36 emits light. The pulse signal amplified by the amplifier circuit 70 is applied to the output terminal 72 of the terminal plate 66.

The modulated light receiving circuit 64 includes a bandpass filter 74, an amplifier circuit 76, a rectifier circuit 82 made up of diodes 78 and 80, a relay driver transistor 84, and a relay 86. The bandpass filter 74 passes only a specific frequency component of the signal input to the input terminal 88 of the terminal board 66, for example, a signal of 20 kHz. Therefore, the bandpass filter 74 removes noise included in the pulse signal output from the photodiode 38 when the photodiode 38 receives disturbance 1 - light. The amplification circuit 76 amplifies the signal of a specific frequency component that has passed through the bandpass filter 74 with an appropriate amplification factor. The rectifier circuit 82 converts the AC signal, which is a specific frequency component that has been appropriately amplified through the band-pass filter 74, into DC. The output of the rectifier circuit 82 is applied to the base of the transistor 84. The emitter of transistor 84 is grounded.

A DC voltage of 1 B is applied to the collector of the transistor 84 via the relay coil 90 of the relay 86 .

When the relay coil 90 of the relay 86 is energized, the common contact 92c of the relay switch 92 of the relay 86
conducts to the individual contact 92a. When the relay coil 90 is demagnetized, the common contact 9 of the relay switch 92
2c is electrically connected to the individual contact 92b. Individual contact 92a,
92b and common contact 92c are connected to connection terminals 94a, 94b, and 94c of terminal board 66, respectively.

Connection terminals 94a, 94b, 94c
A load (not shown) such as an alarm lamp, an alarm buzzer, an actuator such as a motor, etc., which operate in response to the switching mode of the relay switch 92, is connected to.

A high frequency cable 96 is wired between the input terminal 50 of the terminal board 46 of the level detection probe section 12 and the output terminal 72 of the terminal board 66 of the level detection amplifier section 14. In addition, the terminal plate 46 of the level detection probe section 12
A high frequency cable 98 is wired between the output terminal 54 of and the input terminal 88 of the terminal board 66 of the level detection amplifier section 14.

In the interface detection device 10 configured in this way, the light emitting diode 36 is modulated and driven by the output of the modulated light drive circuit 62 via the high frequency cable 48.96, and outputs a modulated laser beam of a predetermined intensity. do. Here, FIG. 5 shows the optical output-forward current characteristics of a general light emitting diode. As can be understood from Fig. 5, when the light-emitting diode is driven in pulses (line 2 in Fig. 5), the forward current is sufficiently increased compared to when the light-emitting diode is driven with direct current (line 2□ in Fig. 5). can be washed away (approximately 10 times more).

Therefore, the intensity of the laser light output from the light emitting diode 36 is strong. Therefore, the guide pipe 22.2
Even if the light transmittance of the guide pipe 22.2 is low, the laser light output from the light emitting diode 36 is attenuated.
Pass through 4. Furthermore, even if the object to be inspected has low transparency, the laser light output from the light emitting diode 36 passes through the object, although it is attenuated. Moreover, the pulse generation circuit 6
The duty ratio of the pulse signal output from 8 is set small.

Therefore, a sufficient amount of the 16th current can be passed through the light emitting diode 36, and the output from the light emitting diode 36 can be increased. Furthermore, since modulated light is used, the S/N ratio can be increased, and the system can be made resistant to noise such as disturbance light. The laser light output from the light emitting diode 36 is given to the photodiode 38 via the guide pipe 22, the liquid to be detected, and the guide pipe 24.

The photodiode 38 outputs a voltage corresponding to the amount of received modulated laser light to the bandpass filter 74 of the modulated light receiving circuit 64 via the high frequency cable 52.98.

Note that it is preferable to use a photodiode 38 that has linearity between the amount of received light and the output voltage. If there is no linearity, it may be corrected using a correction circuit or the like to obtain linearity.

At a certain distance and under a certain amount of light, depending on the transparency of the object to be detected, the photodiode 3
The amount of light received by photodiode 8 increases or decreases, that is, the output voltage of photodiode 38 increases or decreases. Therefore, the interface 8 of the detection target
exists at the point where the transparency changes, so the photodiode 3
8, the change point of the amount of received light, that is, the photodiode 38
The interface 8 can be detected by detecting the point of change in the output voltage.

Here, when the upper layer 4 has higher transparency than the lower layer 6 and the optical axes of the light emitting diode 36 and photodiode 38 are on the upper layer 4, the amount of light received by the photodiode 38 when the light emitting diode 36 is turned on is La, and the amount of light received by the photodiode 38 at this time is La. Let the output voltage of the diode 38 be Va.

In addition, when the optical axis is in the lower layer 6, the light emitting diode 5 The amount of light received by the photodiode 38 when 36 is turned on is Lb.

The output voltage from the photodiode 38 at this time is vb
shall be.

When the precipitate accumulates and the interface 8 rises from below to above the optical axes of the light emitting diode 36 and the photodiode 38, as shown in FIG. As shown in FIG. 8, the output voltage V changes with a slope from the amount of light received La in the upper layer 4 (output voltage Va) to the amount of light received Lb in the lower layer 6 (output voltage vb).

Therefore, a voltage E intermediate between the output voltage Va at the upper layer 4 and the output voltage vb at the lower layer 6 of the photodiode 38 represents the interface 8.

Here, the voltage E is as follows. This voltage E allows the interface 8 to be detected.

When the interface 8 is located below the optical axis formed by the light emitting diode 36 and the photodiode 38 (■ in FIG. 7), the upper layer 4 has high transparency. In this case, the amount of light received by the photodiode 38 is La when the light emitting diode 36 is turned on. Therefore, the photodiode 38 outputs a pulse signal having a high output voltage Va when receiving light, as shown at m and m3 in FIG. 4(2). Noise components due to the disturbance light incident on the photodiode 38 are removed by the bandpass filter 74 (FIG. 4(3)).

The rectifier circuit 82 outputs a high-level DC signal, as shown by Ol in FIG. 4 (4). This DC signal is the base-emitter voltage of the transistor 84. taller than.

Therefore, transistor 84 becomes conductive.

As a result, the relay coil 90 of the relay 86 is energized. Therefore, the common contact 92 of the relay switch 92
c is electrically connected to the individual contact 92a.

When the interface 8 rises and coincides with the optical axis formed by the light emitting diode 36 and the photodiode 38 (■ in FIG. 7), the transparency decreases to an intermediate level between the upper layer 4 and the lower layer 6. In this case, the amount of light received by the photodiode 38 decreases, and when the light emitting diode 36 is turned on, it becomes (La+Lb)/
It is 2. Therefore, from the photodiode 38,
As shown at p, to I)s in FIG. 4(2), a pulse signal of voltage E whose level has been reduced is output. As a result, the output of the rectifier circuit 82 decreases, and the output of the rectifier circuit 82 decreases to 02 in FIG.
As shown in , the base-emitter voltage VIL! of transistor 84 is VIL! be at a lower level. The output voltage of the rectifier circuit 82 is the base-emitter voltage V of the transistor 84.
At a level below BE, transistor 84 turns off.

This demagnetizes the relay coil 90 of the relay 86. Therefore, the switching mode of the relay switch 92 changes, and the common contact 92c separates from the individual contact 92a and becomes conductive to the individual contact 92b.

When the interface 8 further rises by -1- and rises by 2'' from the optical axis formed by the light emitting diode 36 and the photodiode 38 (■ in FIG. 7), the transparency decreases to that of the lower layer 6. Therefore, the output of the photodiode 38 becomes a voltage vb at a further lowered level, as shown at r, to r3 in FIG. 4(2). Therefore, the rectifier circuit 82 outputs a DC signal with a reduced level, as shown at 08 in FIG. 4(4). This DC signal is the base-emitter voltage of the transistor 84. lower. Therefore, transistor 84 remains cut off. by this,
The switching mode of the relay switch 92 is the common contact 92
c and the individual contact 92b remain electrically connected.

In this embodiment, when the interface 8 is below the optical axis of the light emitting diode 36 and the photodiode 38, the connection terminals 94a and 94c are electrically connected, and the connection terminals 94b and 94c are electrically disconnected. Therefore, the load connected between the connection terminals 94a, 94c is activated,
The load connected between the connection terminals 94b, 94c is disabled. When the interface 8 is aligned with the optical axis of the light emitting diode 36 and the photodiode 38, or when it is located above, the connection terminals 94b and 94c are electrically connected, and the connection terminals 94a and 94c are electrically disconnected.

Therefore, the load connected between the connection terminals 94 b and 94 c is activated and the load connected between the connection terminals 94 b and 94 c is activated.
The load connected between a, 94c is disabled. This allows the interface 8 to be detected.

Note that since the modulated light output circuit 62 and the modulated light receiving circuit 64 are provided outside the guide pipes 22 and 24 and the storage tank 2, they are not affected by the temperature of the test target even if the test target is high or low temperature. The modulated light output circuit 62 and the modulated light receiving circuit 64 can operate reliably without any interference.

In the embodiments shown in FIGS. 1 to 3 described above, the level detection probe section 12 is provided from the upper part of the reservoir layer 2, but
As another embodiment of the present invention, as shown in FIG. 9, the level detection probe section 12 may be provided at another location, such as the side of the reservoir layer 2, to form an interface detection device 10a.

FIGS. 1O and 11 are diagrams showing parts of other embodiments of the present invention, and parts corresponding to the embodiments of FIGS. 1 to 3 are given the same reference numerals.

What should be noted in this example is that the high frequency cable is 48°52
, 96.98 in place of fiber optic cable 102.1
04, 106, 108 are used, optical connectors 110, 112 are used in place of the input terminal 50 and output terminal 54 of the terminal board 46, respectively, and optical connectors 110, 112 are used in place of the output terminal 72 and input terminal 88 of the terminal board 66. Optical connectors 114 and 116 are used, respectively, and a light emitting diode 36 and a photodiode 38 are provided in the casing 60 to configure the interface detection device 10b.

In this embodiment, the modulated light output from the light emitting diode 36 is transmitted through the fiber optic cable 106.102 and the end face 102a of the fiber optic cable 102.
Light is projected from. The modulated light projected from this end surface 102a is received by the end surface 104a of the optical fiber cable 104 via the guide pipe 22.24 and the object to be detected. The modulated light received by this end face 104 is transmitted to the photodiode 38 via optical fiber cables 104 and 108.

Here, the rated temperature of the light emitting diode and photodiode within the film is -30 to 125°C. Further, as for the temperature-light output characteristic, as shown in FIG. 12, the output decreases as the temperature increases.

In this embodiment, the light emitting diode 36 and photodiode 38 are connected to the reservoir 2 and the guide pipes 22, 24.
It is provided in the outer casing 60.

Therefore, in this embodiment, the light emitting diode 36. Photodiode 38 is also not affected. Furthermore, this allows the photodiode 38 to output high-output modulated light.

FIG. 13 is a diagram showing another embodiment of the present invention, and parts corresponding to those in the embodiment of FIGS. 1 to 3 are given the same reference numerals. What should be noted in this embodiment is the light emitting diode 36,
The photodiode 38 moves to follow the interface 8, and the interface 8 is detected by the interface detection device 10c.
The position of is indicated.

This interface detection device 10c includes an indicator 210, 211 as an indicating means for indicating the position of the interface 8, a servo motor 212, and a light emitting diode 36 and a photodiode 38 that integrally move according to the rotation of the servo motor 212. In addition to following the interface 8, the indicator 210.2
a link mechanism 213 for causing the interface 8 to point to the interface 8;
Modulated light reception calculation circuit 21 that drives the servo motor 212
4. Note that the servo motor 212 and the link mechanism 213 constitute a moving means.

In the level detection amplifier section 14, the output of the rectifier circuit 82 is given to a modulated light reception calculation circuit 214.

The modulated light reception calculation circuit 214 is a DC/AC conversion circuit 24
1, an amplifier 242, and a variable resistor 243 for applying a bias voltage. The output of the rectifier circuit 82 is given to a DC/AC conversion circuit 241. variable resistance 243
The voltage -B applied to is divided into voltage -E and applied to the DC/AC conversion circuit 241. This divided bias voltage -E is a voltage representing the interface 8, that is, the optical axis of the light emitting diode 36 and the photodiode 38 is at the interface 8.
This cancels out the output of the rectifier circuit 82 in the case of . Therefore, as shown in FIG. 14, the voltage rOJ input to the DC/AC conversion circuit 241 represents the interface 8,
The DC/AC conversion circuit 24 converts the voltage between the interface 8 and the
1 can be entered. DC/AC conversion circuit 24-
33=l converts DC voltage to AC voltage. The DC/AC conversion circuit 241 advances the phase of the AC output when the input voltage is "+". When the input voltage is "-", the phase of the AC output is delayed. The output of the DC/AC conversion circuit 241 is given to an amplifier 242 and amplified. amplifier 2
The output amplified by 42 is sent to the detection coil 2 of the servo motor 212 via the terminal 246 of the terminal board 66.
12b.

In the level detection probe section 12, the light emitting diode 36 fixed to the holder 32 and the photodiode 38 fixed to the holder 34 are connected vertically to the lower ends of the high frequency cables 48 and 52, which are expanded and contracted to have equal lengths. Hanging freely and movably. The upper end of the high frequency cable 48°17 is
It is wound around the drum 218. Therefore, drum 21
8, the light emitting diode 36 and the photodiode 38 integrally move up and down over the range in which the interface 8 is detected.

The light emitting diode 36 is connected to the modulated light output circuit 62 via the high frequency cable 48.96 and the slip ring 225.
It is modulated and driven by , and outputs modulated light 4- with a predetermined intensity. The photodiode 38 outputs a voltage corresponding to the amount of received modulated light to the bandpass filter 74 of the modulated light reception calculation circuit 214 via the high frequency cable 52.98 and the slip ring 225.

The indicator 210 includes a dial 226 and a pointer 227. The pointer 227 is coaxial with the gear 228 and rotates as the gear 228 rotates. The dial 226 is coaxially and fixedly provided to the gear 228.

The indicator 211 includes a potentiometer 229 coaxial with the gear 228, a voltage/current converter 230, and an indicator 231. A DC voltage is applied to the potentiometer 229. Movable contact 229a of potentiometer 229
slides according to the rotation of gear 228. Movable contact 22
The output from 9a is converted into a current by a voltage/current converter 230, and is provided to an indicator 231 consisting of a remotely located ammeter. Therefore, remotely,
By looking at the indicator 231, the position of the interface 8 can be known.

The servo motor 212 includes a drive coil 212a and a detection coil 212b. AC power from an AC power source 33 is supplied to the drive coil 212a via the capacitor 32. The alternating current output of the modulated light reception calculation circuit 214 is given to the detection coil 212b. Modulated light reception calculation circuit 2
14 is the phase of the output given from drive coil 212a.
If the phase of the voltage is ahead of that of servo motor 2,
12 rotates in the normal direction as shown by arrow 234. If the phase of the output given from the modulated light reception calculation circuit 214 lags behind the phase of the voltage of the drive coil 212a, the servo motor 212 rotates in the opposite direction to the arrow 234. .

The link mechanism 213 includes a gear 235 provided on the rotating shaft of the servo motor 212 and a gear 23 that engages with the gear 235.
6, a drum 218 provided coaxially with the gear 236, a slip ring 225, a gear 237, a gear 228 that engages with the gear 237, and a high frequency wave that is wound around the drum and suspends the light emitting diode 36 and the photodiode 38, respectively. and cables 48 and 52.

When the servo motor 212 rotates, the gear 236 rotates at a reduced speed. By the rotation of the gear 236, the drum 21
8 and gear 237 rotate. As the drum 218 rotates, the high frequency cables 48,52 expand and contract. As a result, the light emitting diode 36 and the photodiode 38
move up and down integrally within the guide pipes 22,24. Further, when the gear 237 rotates, the gear 228 rotates while being decelerated. This causes the pointer 227 and the movable contact 229a of the potentiometer 229 to rotate.

In the interface detection device 10c configured in this way, the light emitting diode 36 and the photodiode 38 are connected to the interface 8.
For example, when the lower layer 6 is ejected and the interface 8 is lowered, the output voltage of the photodiode 38 is Va. Therefore, the DC/AC conversion circuit 241
The voltage input to is Va-E, which is "+".

As a result, the phase of the output of the DC/AC conversion circuit 241 advances. Therefore, the servo motor 212
As shown in 4, it rotates in the forward direction. As a result, the light emitting diode 36 and the photodiode +:38 move down in one direction. Also, the pointer 227 of the indicator 210 is set to the arrow 23.
As the indicator 231 rotates as shown in 8, the pointer 231a7 of the indicator 231 descends.

When the light emitting diode 36 and the photodiode 38 reach the interface 8, the output of the photodiode 38 decreases from Va to E. Therefore, the voltage input to the DC/AC conversion circuit 241 is EE and rOJ. As a result, the phase advance of the output of the DC/AC conversion circuit 241 is eliminated, and the output becomes "0". Therefore, servo motor 212 stops rotating. Further, the pointer 227 of the indicator 210 stops rotating and indicates the position of the interface 8, and the pointer 231a of the indicator 231
stops descending and indicates the position of the interface 8.

When the light emitting diode 36 and the photodiode 38 are located below the interface 8, for example, when the lower layer 6 accumulates and the interface 8 rises, the output voltage of the photodiode 38 is
Vb. Therefore, the voltage input to the DC/AC conversion circuit 241 is Vb-E, which is "-". As a result, the phase of the output of the DC/AC conversion circuit 241 is delayed. Therefore, the servo motor 212
38- Rotate in the opposite direction of 4. As a result, the light emitting diode 36 and the photodiode 38 rise in one direction. Further, the pointer 227 of the indicator 210 rotates in the opposite direction of the arrow 238, and the pointer 231a of the indicator 231 rises.

When the light emitting diode 36 and the photodiode 38 reach the interface 8, the output of the photodiode 38 increases from vb to E. Therefore, the voltage input to the DC/AC conversion circuit 241 is "0". As a result, the phase advance of the output of the DC/AC conversion circuit 241 is eliminated, and the output becomes rOJ. Therefore, servo motor 212 stops rotating. In addition, the indicator 21
The zero pointer 227 stops rotating and indicates the position of the interface 8, and the pointer 231a of the indicator 231 stops rising and indicates the position of the interface 8.

In this way, the interface 8 is detected and the interface 8
The location of is indicated. Also, following the fluctuation of the interface 8,
A light emitting diode 36 and a photodiode 38 follow the interface 8, and the position of the interface 8 is continuously indicated.

In the embodiment shown in FIG. 13, the guide pipe 22°24
A light emitting diode 36 and a photodiode 38 are provided in the interior, and a high frequency cable 48.52.96.98 is used.
Similar to the embodiment shown in FIGS. and 11, the high frequency cable 4
Fiber optic cable 1 instead of 8.52.96.98
02.104.106.108, the light emitting diode 36 and the photodiode 38 may be provided in the casing 60 to constitute an interface detection device.

Further, as another embodiment of the present invention, the guide pipe 22.
24 may be omitted to configure the interface detection device.

Further, although the light receiving means and the light emitting means are described as photodiodes and light emitting diodes, other light receiving means and light emitting means such as a phototransistor may be used.

Further, the modulated light output circuit, the modulated light receiving circuit, and the modulated light receiving calculation circuit may be configured with other circuits.

In addition, in the above-mentioned example, the reference layer and the comparison layer were explained as a liquid and a precipitate, but it can also be implemented in a fluid body such as a gas or powder.

[Effect 1 of the Invention As described above, in the interface detection device according to claim (1), the pair of guide pipes have translucency and are arranged at a predetermined interval. The modulated light drive circuit outputs a modulation signal to modulate and drive the light emitting means.

The light receiving means receives modulated light projected from inside one guide pipe to inside the other guide pipe via both guide pipes and the object to be inspected. The modulated light receiving circuit detects the interface by looking at the output level of the light receiving means.

Therefore, even if the specific gravity or impedance of the reference layer or comparison layer changes, the translucency of the reference layer and comparison layer is not affected, so the interface can be reliably detected. Similarly, even if there is not much difference in specific gravity or impedance between the reference layer and the comparison layer, it is possible to reliably detect the interface.

Moreover, since the light emitting means is modulated and driven, the intensity of the modulated light projected from the light emitting means can be increased. When considering heat resistance, corrosion resistance, adhesion resistance, dust resistance, etc., it may be necessary to use a material with poor translucency for the guide pipe, such as FEP, or the translucency of the object to be inspected. Even when it is necessary to detect an interface between two objects with low intensity, the highly intense modulated light can pass through these guide pipes and the object to be inspected. Therefore, even in these cases, the interface can be easily detected.

In the interface detection device according to claim (4), the moving means includes:
The optical axis between the guide pipes of the light emitting means and the light receiving means is integrally moved. The modulated light reception calculation circuit determines the difference between the output level of the light receiving means and a predetermined reference output level corresponding to the interface, and drives the moving means according to the determined difference so that the difference disappears.

Therefore, even if the specific gravity or impedance of the reference layer or comparison layer changes, the translucency of the reference layer or comparison layer is not affected, so that the interface can be reliably detected. Similarly, even when there is not much difference in specific gravity or impedance between the reference layer and the comparison layer, the interface can be reliably detected. Further, the light emitting means and the light receiving means can move to follow the interface and detect the interface.

Moreover, since the light emitting means is modulated and driven, the intensity of the modulated light projected from the light emitting means can be increased. When considering heat resistance, corrosion resistance, adhesion resistance, dust resistance, etc., it may be necessary to use abrasive materials with poor translucency for the guide pipe, such as FEP, or Even when it is necessary to detect an interface between objects whose luminous intensity is not very good, the strong modulated light can pass through these guide pipes and the inspection object. Therefore, even in these cases, the interface can be easily detected.

In the interface detection device of claim (5), claim (4)
The method further includes indicating means for indicating the position of the interface.

Therefore, the position of the interface can be easily known.

In the interface detection device according to claim (2) or (6),
In the device according to claim (1), (4), or (5), the modulated light output circuit and the modulated light receiving circuit or the modulated light output circuit and the modulated light receiving calculation circuit are provided outside the guide pipe.

Therefore, even if the test target is high or low temperature, the modulated light output circuit and the modulated light receiver circuit or the modulated light output circuit and the modulated light receiver calculation circuit can operate reliably without being affected by the temperature of the test target. can.

In the interface detection device according to claim (3) or (7),
In claim (1), (4) or (5), the light emitting means, the light receiving means, the modulated light output circuit and the modulated light receiving circuit, or the light emitting means, the light receiving means, the modulated light output circuit and the modulated light receiving calculation circuit are , installed outside the guide pipe.

Therefore, even if the test target is high or low temperature, the light emitting means, the light receiving means, the modulated light output circuit and the modulated light receiving circuit or the light emitting means, the light receiving means, the modulated light output circuit and the The modulated light reception calculation circuit can operate reliably.

The interface detection device according to claim 8 detects an interface between two layers of fluid having different light transmittances to be detected. This device outputs modulated light modulated at a predetermined frequency. The modulated light that is projected and passes through the inspection target is received. The interface is detected by a change in the level of the received light.

Therefore, even if the specific gravity or impedance of the two layers changes, the translucency of the two layers is not affected, so the interface can be reliably detected.

Similarly, even if there is not much difference in specific gravity or impedance between the two layers, the interface can be reliably detected.

Moreover, since modulated light is emitted from the light projecting means, the intensity of the modulated light projected from the light projecting means can be increased. Even when it is necessary to detect an interface between objects to be inspected whose light transmittance is not very good, the highly intense modulated light can be transmitted through the objects to be inspected. Therefore, even in these cases, the interface can be easily detected.

Furthermore, since modulated light is used, the S/N ratio can be increased, and the system can be made resistant to noise such as disturbance light.

[Brief explanation of the drawing]

FIG. 1 shows an interface detection device according to an embodiment of the present invention.
The figure is a diagram showing details of the level detection probe section, and the third
The figure is a circuit diagram of the level detection amplifier unit 14, Figure 4 is a waveform diagram for explaining the operation of the modulated light output circuit and the modulated light receiver circuit, and Figure 5 is a diagram showing the case where the light emitting diode is driven with direct current and the case where the pulse modulation is performed. FIG. 6 is a diagram showing the current-output characteristics when driven; FIG. 6 is a diagram showing the relationship between the transparency of the object to be detected and the amount of light received by the light-receiving element/output voltage; FIG. This is a diagram showing the state in which the interface has changed. Figure K is a diagram showing the relationship between the amount of light received by the photodiode 6 (output voltage) and the distance from the optical axis to the interface at that time, and Figure 9 is the diagram shown in this figure. 10 and 11 are diagrams showing a level detection probe section and a level detection amplifier section, respectively, of another embodiment of the invention, and FIG. 12 is a diagram showing a part of another embodiment of the invention. is a diagram showing the relative output vs. ambient temperature characteristics of the light emitting diode 36, FIG. 13 is a diagram showing another embodiment of the present invention, and FIG. 14 is a diagram showing the distance from the interface when a bias voltage is applied. It is a figure showing the relationship with the voltage input into a voltage/current converter. 2...Storage tank 4...Upper layer 6...Lower layer 8...Interface 10, 10b, 10c -...Interface detection device 22,
24...Guide pipe 36...Light emitting diode 38...Photodiode 48, 52.96.98...High frequency cable 62...
- Modulated light output circuit 64... Modulated light receiving circuit 102, 104.106.108... Optical fiber cable 210, 211... Indicator 212... Servo motor 213... Link mechanism 214... Modulation Light receiving calculation circuit JP-A-3 146825 (14) Fig. 2 ■ 362 Emitting power and output voltage ■) Introduction Cabinet 1 and 22 Ran 111 O and 2 Interchange 1 [''8 plane (optical axis) Distance to interface

Claims (8)

[Claims] (1) An interface detection device that detects an interface between two layers of a fluid to be detected, a reference layer and a comparison layer, which have different light transmittances, and which has light transmittance and is arranged at a predetermined interval. a pair of guide pipes arranged with a gap between them; a light emitting means; a modulated light drive circuit that outputs a modulation signal and modulates and drives the light emitting means; An interface detection device comprising: a light receiving means for receiving modulated light projected inward from the other guide pipe; and a modulated light receiving circuit for detecting an interface by checking the output level of the light receiving means. (2) A light emitting means is inserted into the one guide pipe, and a light receiving means is inserted into the other guide pipe at a predetermined fixed position with their optical axes aligned, and a modulated light output circuit and a modulating light output circuit are installed outside the guide pipe. Claim (1) characterized in that a light receiving circuit is provided, and a high frequency cable is electrically connected between the output of the modulated light output circuit and the light emitting means and between the input of the modulated light receiving circuit and the light receiving means. interface detection device. (3) A light emitting means, a light receiving means, a modulated light output circuit, and a modulated light receiving circuit are provided outside the guide pipe, and the modulated light output from the light emitting means is delivered to a predetermined fixed position within the one guide pipe. Claim (1) characterized in that an optical fiber cable is provided for transmitting and projecting light and transmitting modulated light received at a predetermined fixed position in the other guide pipe where the optical axes coincide to the light receiving means. ) interface detection device. (4) An interface detection device that detects an interface between two layers of a fluid to be detected, a reference layer and a comparison layer, which have different light transmittances, and which has light transmittance and detects the interface. a pair of guide pipes disposed at a predetermined interval over a range to be inspected; a light emitting means; a modulated light drive circuit that outputs a modulation signal and modulates and drives the light emitting means; a light receiving means for receiving modulated light projected from the inside of one guide pipe to the inside of the other guide pipe; a moving means for integrally moving an optical axis between both the guide pipes of the light emitting means and the light receiving means; a modulated light reception calculation circuit that determines the difference between the output level of the light receiving means and a predetermined reference output level corresponding to the interface, and drives the moving means so that the difference disappears according to the determined difference; An interface detection device comprising: measuring an output level of a light receiving means in advance in a reference layer and a comparison layer, and detecting an interface based on the output level of the light receiving means. (5) The interface detection device according to claim (4), further comprising instruction means for indicating the position of the interface. (6) A light emitting means is inserted into the one guide pipe, a light receiving means is movably inserted into the other guide pipe with their optical axes aligned, and a modulated light output circuit and a modulated light reception calculation circuit are provided outside the guide pipe. Claim (4) or (4), characterized in that the output of the modulated light output circuit and the light emitting means and the input of the modulated light reception calculation circuit and the light receiving means are electrically connected by high frequency cables. 5) Interface detection device. (7) A light emitting means, a light receiving means, a modulated light output circuit, and a modulated light receiving calculation circuit are provided outside the guide pipe, and the modulated light outputted from the light emitting means is movably transmitted into the one guide pipe. Claim (4) or (5), characterized in that an optical fiber cable is provided for projecting light and transmitting the modulated light received movably within the other guide pipe to the light receiving means with the optical axes aligned. Interface detection device. (8) An interface detection device that detects an interface formed by two layers of a fluid with different light transmittances, which outputs modulated light modulated at a predetermined frequency, and An interface detection device, characterized in that it receives modulated light that has passed through an object to be inspected, and detects an interface based on a change in the level of the received light.