JP3627161B2 - Liquid level measuring instrument - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a take-up type liquid level measuring device suitable for measuring a liquid level in a large tank or the like.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a winding type liquid level measuring device using a constant tension spring is known as a liquid level measuring device for measuring the liquid level in a large tank. This liquid level measuring device is configured by attaching a float to the tip of a wire (or tape), providing a spring and sprocket for winding the wire at a constant tension in the body, and directly connecting a counter display to the sprocket. The This level gauge makes the spring tension change by the weight of the wire just above the float so that the float follows the top and bottom of the liquid level, and the length of the wire above the float is adjusted to the liquid level. Is displayed on the counter display section.
[0003]
[Problems to be solved by the invention]
However, this type of liquid level measuring device can measure the liquid level in a large tank relatively accurately without the need for auxiliary power such as electricity or air pressure. When measuring with a drop, or when the liquid level fluctuates significantly, the wire is easily detached from the sprocket or drum due to the inertia of the wire drum or sprocket, and the wire is likely to loosen. There was a problem that it was difficult to measure.
[0004]
The present invention has been made in view of the above points, and an object thereof is to provide a take-up type liquid level measuring device capable of measuring the liquid level of a large tank or the like with high accuracy.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, the liquid level measuring device of the present invention has a winding drum in which a wire is wound in the measuring device main body, and the wire is drawn out from above to the liquid level to reach the liquid level. In the liquid level measuring device for measuring the distance of the wire, a wire feeding length signal generating means for generating a signal indicating the feeding length of the wire, and a liquid level detection signal are generated when connected to the tip of the wire and reach the liquid level. A liquid level detector, a rising end detector for detecting that the liquid level detector is at the rising end, and a liquid level detector, and transmitting the spatial light by directing the liquid level detection signal toward the measuring instrument main body side. A liquid level detection optical signal transmission means for performing, a liquid level detection optical signal reception means for receiving a liquid level detection optical signal sent from the liquid level detection optical signal transmission means, and the rising end Before the wire is unwound from the state where the detector detects the rising edge of the liquid level detector The wire feed length signal from the wire feed length signal generating means is captured until the liquid level detector reaches the liquid level, and the distance from the measuring device main body to the liquid level is calculated based on the wire feed length data. And a power storage means that can be charged to the power supply in the liquid level detector, and when the liquid level detector is located at the rising end, inductive power feeding from the measuring instrument main body via the tuning coil To charge the power storage means.
[0006]
Here, a main electrode and an auxiliary electrode are provided at the lower part of the measuring instrument main body, the main electrode protrudes from the tip of the conical bottom of the measuring instrument main body, and the auxiliary electrode has a cylindrical shape or a plurality of rods. It is good to project in the downward direction from the main electrode.
[0007]
[Action / Effect]
In the liquid level measuring device having such a configuration, when the liquid level is measured, the wire is fed from the winding drum, and the liquid level detector at the tip of the wire is lowered toward the liquid level. At this time, the wire feeding length signal generating means generates a signal indicating the feeding length of the wire, and the calculation control means starts the wire feeding length from the state where the rising edge detector detects the rising edge of the liquid level detector. The signal indicating is taken in. When the liquid level detector reaches the liquid level, the liquid level detection optical signal is transmitted from the liquid level detection optical signal transmission unit of the liquid level detector to the liquid level detection optical signal reception unit on the main body side, and the wire is fed out. Is stopped.
[0008]
The arithmetic control means is configured to feed the wire from the wire feeding length signal generating means until the wire is fed from the state where the rising edge detector detects the rising edge of the liquid level detector until the liquid level detector reaches the liquid level. The long signal is taken in, and the distance from the measuring instrument body to the liquid level is calculated based on the wire feed length data.
[0009]
In this way, instead of detecting loosening of the wire when the float arrives at the liquid level, the wire level detector is electrically detected when the liquid level detector has reached the liquid level and stops feeding the wire. It is difficult to loosen, and the distance to the liquid level can be measured with high accuracy.
[0010]
In addition, chargeable power storage means is provided for the power supply in the liquid level detector, and when the liquid level detector is located at the rising end, the power storage means is charged by induction power feeding from the measuring instrument main body side through the tuning coil. The battery can be charged automatically and reliably as the power source of the liquid level detector, and it is charged without contact, so there is no risk of contact failure and the battery etc. in the liquid level detector can be managed. It can be simplified. If a capacitor is used as the power storage means, maintenance such as battery replacement becomes unnecessary.
[0011]
Furthermore, a main electrode and an auxiliary electrode are provided at the lower part of the measuring instrument main body, the main electrode is provided at the tip of the conical bottom of the measuring instrument main body, and the auxiliary electrode is provided around the main electrode so as to protrude below the main electrode. If so, it is possible to minimize the ripple of the liquid level when the liquid level detector reaches the liquid level to be measured, and to improve the measurement accuracy.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0013]
FIG. 1 shows a longitudinal sectional view of the liquid level measuring device, and FIG. 2 shows a transverse sectional view thereof. Reference numeral 1 denotes a case of the measuring instrument main body, and an opening 1 a for receiving the liquid level detector 10 is formed at the bottom of the case 1.
[0014]
A winding drum 3 for winding the wire 2 is attached in the case 1, and the winding drum 3 is rotationally driven by a winding motor 4 via a speed reducer 4a. Further, the pulley 5 is rotatably mounted next to the winding drum 3, and the wire 2 drawn from the winding drum 3 is hung on the pulley 5. A liquid level detector 10 is connected to the tip of the wire 2. The wire 2 may be a tape-shaped wire.
[0015]
The pulley 5 is provided with a rotary encoder 24 that outputs a frequency signal corresponding to the rotation angle of the pulley 5 as a wire feed length signal generating means. As the rotary encoder 24, one using a magnetic sensor, an optical sensor, or the like is used, and a magnetic pole portion, an opening portion, a reflection portion, and the like are provided at predetermined intervals on the peripheral portion of the pulley 5 corresponding to these sensors.
[0016]
A storage unit 6 for storing the liquid level detector 10 is provided above the opening 1 a at the bottom of the case, and a primary coil 7 for induction feeding is wound around the storage unit 6. As shown in FIG. 4, the primary coil 7 is connected to the output side of the oscillation circuit 8 of the induction power feeding circuit that charges the power supply on the detector side. The oscillation circuit 8 oscillates a high frequency signal of 1 MHz, for example, and supplies it to the primary coil 7. A guide pulley 9 that guides the wire 2 drawn from the pulley 5 is disposed above the storage unit 6.
[0017]
The guide pulley 9 is made of an insulated conductive metal, and a voltage is applied between the wire 2 and the guide pulley 9 to determine whether or not the wire 2 is loosened by determining a conduction state therebetween. The wire looseness detector 26 is configured. In addition, a limit switch or the like for detecting that the liquid level detector 10 is in the rising end, that is, in the storage unit 6, is provided as the rising end detector 25 at the upper part of the storage unit 6.
[0018]
A battery 30 is built in the case 1 as a power source for a power feeding circuit, a detection circuit, and the like. Further, a light receiving element 19 for receiving an optical signal output from the liquid level detector 10 at the time of liquid level detection is provided on the bottom of the case 1 downward. The light receiving element 19 constitutes a liquid level detection optical signal receiving means.
[0019]
As shown in FIG. 3, the liquid level detector 10 connected to the tip of the wire 2 is formed in a cylindrical shape, with a main electrode 13 protruding from the bottom tip, and a cylindrical auxiliary electrode 11 at the bottom. Is provided. The tip of the main electrode 13 is formed slightly above the tip of the auxiliary electrode 11, that is, the tip of the auxiliary electrode 11 protrudes slightly below the main electrode 13, and the bottom of the liquid level detector 10 reaches the liquid level. The surrounding auxiliary electrode 11 is first touched, and the central main electrode 13 is then touched to the liquid surface. The auxiliary electrode 11 is provided with an air escape hole 11a.
[0020]
The liquid level is detected by detecting a change in the resistance value between the main electrode 13 and the auxiliary electrode 11. A light-emitting element 14 that outputs an optical signal at the time of detection is attached upward as liquid level detection optical signal transmitting means on the upper part of the liquid level detector 10.
[0021]
In the liquid level detector 10, as shown in the block diagram of FIG. 4, a liquid level detection circuit 15 for detecting a liquid level by detecting a change in resistance value between the main electrode 13 and the auxiliary electrode 11, and a liquid level detection circuit Circuit board including an oscillation circuit 16 that oscillates in response to a detection signal from 15, a light emitting circuit 17 that emits light from the light emitting element 14 in response to an output from the oscillation circuit 16, and a power supply circuit 18 that serves as a power source for each circuit Is built-in. These circuits and the light projecting element 14 constitute a liquid level detection optical signal transmission means.
[0022]
The power supply circuit 18 is disposed in the upper part of the liquid level detector 10, and is a tuning coil 12 that is tuned to the primary coil 7, a rectifier circuit that rectifies the high-frequency current induced through the tuning coil 12, and a power storage circuit It has a capacitor or a secondary battery. When the liquid level detector 10 is in the measuring device main body at the rising end, the liquid level detector 10 receives high-frequency power through the primary coil 7 and the tuning coil 12, rectifies it, and charges the capacitor (or secondary battery).
[0023]
The measuring instrument main body having the above-described configuration is attached to the inner upper part of the large tank, and is installed so that the liquid level detector 10 is lowered from above toward the liquid level in the tank. On the other hand, a control panel of a measuring instrument that receives signals from the light receiving element 19, which is a liquid level detection light signal receiving means, an encoder 24, etc., and calculates and displays measured values is separately installed.
[0024]
As shown in the block diagram of FIG. 5, the control circuit of the control panel is configured with a microcomputer as a main part, and includes a CPU 20, a ROM 21, a RAM 22, and an input / output circuit 29. The winding motor 4, the rotary encoder 24, the upper end detector 25, the wire looseness detector 26, the operation switch 27, the light receiving element 19, and the oscillation circuit 8 of the induction power feeding circuit are connected to the input / output circuit 29.
[0025]
The CPU 20 takes in the liquid level detection signal and the output signal of the encoder 24 based on the program data stored in the ROM 21 in advance, calculates the distance to the liquid level, and displays the measured value on the display unit 23. To do. Further, in the ROM 21, a correction coefficient corresponding to the distance data is stored in advance as table data or the like in order to correct the calculated distance data. The correction coefficient is calculated in advance from an actual measurement value and stored in accordance with, for example, the slippage of the pulley and the wire and the elongation of the wire.
[0026]
Next, the operation of the liquid level measuring device having the above configuration will be described.
[0027]
When the predetermined operation switch 27 is turned on when measuring the distance to the liquid level in the tank, the CPU 20 enters the liquid level measurement process of FIG. 6. First, in step 100, the liquid level detector 10 is at the rising end. It is determined whether or not. If the ascending end detector 25 detects the ascending end, next, at step 110, the winding motor 4 is driven to the descending side, and at step 120, data acquisition from the encoder 24 is started.
[0028]
Thereby, the winding drum 3 is rotationally driven in the wire feeding direction, and the liquid level detector 10 at the tip of the wire 2 descends in the tank by its own weight. At this time, the pulley 5 is driven to rotate in accordance with the feeding of the wire 2, and a signal indicating the rotation angle is output from the encoder 24, and the signal is captured by the CPU 20. The distance to the surface detector 10 is calculated, and the distance is displayed on the display 23 in step 140. Such processing is repeated every predetermined time (several hundred milliseconds), and the display distance is incremented.
[0029]
On the other hand, if the wire 2 is loosened while the liquid level detector 10 is descending, the wire looseness detector 26 detects it and sends it to the CPU 20. Then, the driving of the winding drum 3 is stopped.
[0030]
When the lower part of the liquid level detector 10 reaches the liquid level, the resistance value between the main electrode 13 and the auxiliary electrode 11 changes due to the liquid, and the liquid level detection circuit 15 detects the arrival of the liquid level. The light emitting circuit 17 operates, and the light projecting element 14 provided on the upper part of the detector performs the light projecting operation.
[0031]
When the liquid level detector 10 reaches the liquid level, the cylindrical auxiliary electrode 11 first touches the liquid level, and then the central conical part touches the liquid level, so that the disturbance of the liquid level is minimized. Therefore, the liquid level detection signal by the main electrode 13 and the auxiliary electrode 11 can be obtained stably.
[0032]
At this time, the light receiving element 19 on the measuring instrument body side receives the optical signal indicating the liquid level detection from the light projecting element 14 and sends the received light signal (liquid level detection signal) to the CPU 20. When this liquid level detection signal is input, the CPU 20 determines that the liquid level is detected, proceeds from step 160 to step 170, stops the winding motor 4 immediately, and stops the descent of the liquid level detector 10. Then, in step 180, the distance data at that time is corrected to calculate the distance data to the final liquid level. In step 190, the distance data, that is, the distance from the upper end of the tank to the liquid level is calculated. This is displayed on the display 23.
[0033]
Thereafter, in step 200, the CPU 20 drives the winding motor 4 to the winding side, winds the wire 2 around the winding drum 3, raises the liquid level detector 10, and in step 210, the liquid level detector. 10 rises to the storage 6 of the measuring instrument main body, and when the rising end detector 25 detects the rising end, the process proceeds from step 210 to step 220 to stop the lifting operation by the winding motor 4 and the liquid of this time Complete the surface measurement.
[0034]
In a state where the liquid level detector 10 is stored in the storage unit 6, the upper tuning coil 12 is positioned relative to the primary coil 7 in the storage unit 6, and the primary coil 7 and the tuning coil 12 are electromagnetically connected. The primary coil 7 is supplied with a high frequency current of, for example, 1 KHz from the oscillation circuit 8. Therefore, a high frequency voltage having the same frequency is induced in the tuning coil 12 on the liquid level detector 10 side, the high frequency power is rectified in the power supply circuit 18, and the capacitor is charged with power. The electric power charged in this capacitor is used for the next liquid level measurement.
[0035]
Thus, in order not to detect the looseness of the wire when the float arrives at the liquid level, but to electrically detect that the liquid level detector 10 has reached the liquid level and stop the winding motor 4, It is difficult for the wire 2 to loosen, and the distance to the liquid surface can be measured with high accuracy. Further, even if the wire 2 is loosened, the wire looseness detector 26 can detect the looseness of the wire. When the looseness is detected, the winding motor 4 is emergency-stopped to prevent the wire from coming off or entangled. can do.
[0036]
The auxiliary electrode provided in the lower part of the liquid level detector 10 may be a plurality of rod-shaped electrodes instead of the cylindrical shape, and if the plurality of rod-shaped electrodes have a shape protruding below the main electrode 13. Similarly to the above, it is possible to detect the position of the liquid level stably and accurately without disturbing the liquid level when reaching the liquid level.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of a measuring device main body showing an embodiment of the present invention.
FIG. 2 is a cross-sectional view of the measuring instrument main body.
FIG. 3 is a cross-sectional view of a liquid level detector.
FIG. 4 is a block diagram of a circuit of the liquid level detector.
FIG. 5 is a block diagram of a control circuit of the liquid level measuring device.
FIG. 6 is a flowchart showing a liquid level measurement operation.
[Explanation of symbols]
2-wire 3-winding drum 4-winding motor 5-pulley 6-housing 7-primary coil 10-liquid level detector 11-auxiliary electrode 12-tuning coil 13-main electrode 14-light projecting element 19-light receiving Element 20-CPU
24-Rotary encoder 25-Up end detector 26-Wire looseness detector

Claims (4)

In a liquid level measuring instrument that has a winding drum in which a wire is wound in the measuring instrument main body and measures the distance to the liquid level by feeding and lowering the wire from above with respect to the liquid level,
Wire feeding length signal generating means for generating a signal indicating the feeding length of the wire;
A liquid level detector connected to the tip of the wire and generating a liquid level detection signal when reaching the liquid level;
A rising edge detector for detecting that the liquid level detector is at the rising edge;
A liquid level detection optical signal transmitting means provided in the liquid level detector, for transmitting the liquid level detection optical signal toward the measuring device main body in a spatial light;
A liquid level detection optical signal receiving means provided on the measuring instrument main body side for receiving a liquid level detection signal sent from the liquid level detection optical signal transmission means;
From the state where the rising end detector detects the rising end of the liquid level detector until the wire is drawn and the liquid level detector reaches the liquid level, the wire feeding length signal from the wire feeding length signal generating means Calculation control means for calculating the distance from the measuring instrument body to the liquid level based on the wire feed length data;
With
When the power source in the liquid level detector is provided with a chargeable storage means, and the liquid level detector is located at the rising end, the storage means is charged by inductive power feeding from the measuring instrument main body side through the tuning coil. A liquid level measuring device characterized by having a structure to perform. A main electrode and an auxiliary electrode are provided at the lower part of the measuring instrument body, the main electrode is projected from the tip of the conical bottom of the measuring instrument body, and the auxiliary electrode is formed in a cylindrical shape around the main electrode and The liquid level measuring device according to claim 1, wherein the liquid level measuring device is provided so as to protrude downward from the main electrode. A main electrode and an auxiliary electrode are provided at the lower part of the measuring instrument body, the main electrode is projected from the tip of the conical bottom of the measuring instrument main body, and the auxiliary electrode is formed around the main electrode as a plurality of rods. The liquid level measuring device according to claim 1, wherein the liquid level measuring device is provided so as to protrude downward from the main electrode. The liquid level measuring device according to claim 1, wherein a capacitor is provided as a power storage circuit in a power circuit in the liquid level detector.

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