JPH0692910B2 - Electrode level detector - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode type level detecting device for detecting the level position of contents such as a hopper for accommodating ore or the like.

[0002]

2. Description of the Related Art Conventionally, one of insulators having a compensating electrode interposed in the middle is supported by a machine frame and the other is supported by a level detecting electrode, and the electrode is supported in a hopper so that the electrode is grounded. A detection potential is applied, and the ore in the hopper is brought into contact with or separated from the tip of the electrode to detect a change in electric resistance based on the contact or separation, and thereby the ore in the hopper has reached a level position. There is a device that can detect whether or not the interelectrode insulator is dirty by the compensating electrode (for example, Japanese Patent Publication No. 54-31821).

[0003]

By the way, in the above-mentioned conventional apparatus, when dirt or the like adheres to the insulator, the detection sensitivity of the level detection electrode is lowered, which causes malfunction or malfunction. there were.

[0004]

In order to achieve the above object, the present invention firstly supports one of insulators having a compensation electrode in the middle in a machine frame and the level detection electrode in the other. In addition, a voltage is applied between the machine frame and a negative potential to detect a change in the detected object electric resistance due to contact between the level detected electrode and the detected object. A first electric resistance between them, a second electric resistance between the compensation electrode and the machine frame, an electric resistance of the detected object, and a first resistance connected between the level detection electrode and a negative potential. And a second resistor connected between the compensating electrode and the negative potential, and a current flowing through the first electric resistance is zero so as to maintain the equilibrium state of the bridge circuit. And a balance holding circuit
An electrode type level detection device formed so as to detect a change in the electrical resistance of the detected object in the balanced state of the bridge circuit as a level change of the detected object by a change in the current flowing through the first resistor, Secondly, the electrode type level detecting device according to the first aspect is configured to detect a voltage between an output terminal of the balance holding circuit and a negative potential as a stain detection voltage of the insulator. .

[0005]

In the first aspect of the invention, the tip of the level detecting electrode is brought into contact with the object to be detected, and in this state, the balanced state of the bridge circuit is held by the balanced holding circuit. When the object to be detected decreases from this state and is separated from the level detection electrode, the electric resistance of the object to be detected changes, and thus it is possible to detect that the level of the object to be detected is below the level by detecting the resistance change. At this time, even if dirt or the like adheres to the insulator and the first or second electric resistance decreases, the balance holding circuit keeps the balance of the bridge circuit. A current does not flow into the device, and it is possible to prevent malfunction of level detection due to dirt on the insulator.

Further, in the state where the bridge circuit is balanced, even if the first or second electric resistance changes, the level detection voltage taken out from the first resistor changes by the change in the electric resistance of the object to be detected. Therefore, accurate detection can be performed without being affected by dirt on the insulator.

In the second aspect of the invention, the voltage between the output terminal of the balance holding circuit and the negative potential changes based on the second electric resistance due to the dirt of the insulator and the like. It is possible to display the degree of the above or give an alarm.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a side sectional view of a detection device according to the present invention. In the figure, 1 is a machine frame made of a conductor, 2 is a hopper made of a conductor provided in the machine frame 1 and electrically connected to the machine frame 1, and 3 is supported by the machine frame 1 by a flange F. It is a detection unit.

In the detection unit 3, 4 is a level detection electrode, 5 and 6 are insulators, 7 is a leakage compensation electrode, and the compensation electrode 7, the level detection electrode 4 and the machine casing 1 are the insulators 5. , 6 is insulated.

Reference numeral 8 is an ore (for example, coal) stored in the hopper 2, and when the ore 8 reaches a predetermined amount, the ore 8 comes into contact with the tip of the level detecting electrode 4 and the amount thereof decreases so that It is separated from the electrode 4.

Reference numerals 9, 10, and 11 denote terminals connected to the machine frame 1, the leakage compensation electrode 7 and the level detection electrode 4, respectively.
Reference numerals 12 and 13 denote first and second electric resistances caused by the deposit A such as dirt on the insulator between the compensation electrode 7 and the level detection electrode 4 and between the machine casing 1 and the compensation electrode 7, respectively.
Is the electrical resistance of the detected substance by the ore between the level detection electrode 4 and the hopper 2.

FIG. 2 shows a circuit configuration of the detection device of the present invention, and the device is constructed by connecting the following elements to the terminals 9, 10 and 11.

That is, a level detecting resistor (first resistor) 15 and a resistor (second resistor) 16 are connected between the terminal 11 and the negative potential and between the terminal 10 and the negative potential, respectively. Then, the bridge circuit B is configured with the electric resistances 12 and 13 due to the dirt and the detected object electric resistance 14 due to the ore. A DC power supply 18 is connected between the terminal 9 and the negative potential to keep the bridge circuit B in a balanced state, and between the negative potential and the terminal 11 connected to the level detecting electrode 4, that is, the level detecting resistor. The detection voltage 17 at the ore level position is obtained from the container 15.

The operational amplifier (differential amplifier) 19 connected between the terminals 10 and 11 acts as a variable resistor connected in parallel to the resistor 16 by using it as a current source in the forward and reverse directions. However, the balance condition of the bridge circuit B is satisfied.

A balanced compensation voltage 22 between the leakage compensation electrode 7 and the level detection electrode 4 is obtained between the output terminal 20 and the negative potential terminal 21 of the amplifier 19. This balance compensation voltage 22
Changes depending on the second electric resistance 13 due to the dirt of the insulator, and therefore the voltage 22 can be used as the dirt detection voltage of the insulator.

Since the present invention is configured as described above, the operational amplifier 19 acts as a variable resistor connected in parallel to the resistor 16, and the detected object electric resistance 14 and the electric resistances 12 and 13 due to dirt change. However, the balance of the bridge can always be satisfied, and the stable level detection voltage 17 can be obtained while the ore 8 is in contact with the level detection electrode 4. That is, even if the electric resistances 12 and 13 due to dirt change, the detection voltage 17 at the level of the ore is always divided by the ratio of the electric resistance 14 of the object to be detected and the resistor 15 for detection and the electric resistance 14 of the object to be detected. Therefore, it is not affected by the dirt of the insulator. Also,
When the ore 8 is separated from the level detection electrode 4, the detected object electric resistance 14 becomes infinite, so that the state can be detected as a change in the level detection voltage 17. Therefore,
It is possible to accurately detect whether the ore is at the level position in contact with the level detection electrode 4 or at the level position separated from the level detection electrode 4 or less.

As a method of satisfying the bridge balance condition, the resistor 16 may be automatically variable by using a servomotor or the like.

Further, the balanced compensation voltage 2 between the terminals 10 and 11
By detecting 2, the degree of contamination of the insulators 5 and 6 can be detected. That is, by connecting an alarm device or a dirt display device between the terminals 20 and 21, it is possible to give an alarm or display the cleaning time of the dirt of the insulator.

As a result of an experiment of the apparatus of the present invention, when the detected object electric resistance 14 is 10 MΩ to 100 KΩ, there is almost no change in the detected voltage 17 even if the electric resistances 12, 13 due to dirt are changed from ∞Ω to 20 KΩ. The experimental results of

FIG. 3 shows another embodiment of the present invention, in which the detecting apparatus of the present invention is used for detecting the level of the ore 8 ′ piled up on the ground 24. That is, the detection unit 3 is provided at the tip of the crane 25, and the level detection electrode 4 thereof is brought into contact with the top of the ore 8 '.

In this case, the same action and effect can be obtained by constructing a bridge circuit similar to that of FIG. 2 by using the resistance between the level detection electrode 4 and the ground as the electrical resistance of the detected object.

[0022]

As described above, according to the present invention, even if dirt or the like adheres to the insulator, the balance holding circuit maintains the balance of the bridge circuit, so that the insulator surface between the compensation electrode and the level detection electrode is maintained. No current flows through the electric resistance due to dirt and the like, and it is possible to effectively prevent malfunction and malfunction of the level detection due to dirt and the like of the insulator.

Further, by detecting the voltage between the output terminals of the balance holding circuit and the negative potential, the degree of dirt or the like can be detected, and the degree of dirt or the like is displayed or an alarm is issued based on the detected voltage. be able to.

[Brief description of drawings]

FIG. 1 is a side sectional view of an electrode type level detection device of the present invention.

FIG. 2 is a circuit diagram of an electrode type level detection device.

FIG. 3 is a side view of another embodiment of the electrode type level detecting device of the present invention.

[Explanation of symbols]

 1 Machine Frame 2 Hopper 4 Level Detection Electrode 5,6 Insulator 7 Leak Compensation Electrode 8 Ore 12 First Electrical Resistance 13 Second Electrical Resistance 15 First Resistor 16 Second Resistor 19 Operational Amplifier

Claims (2)

[Claims] 1. The level detection is carried out by supporting one of the insulators with a compensation electrode in the middle of the frame and supporting the level detection electrode on the other side, and applying a voltage between the frame and the negative potential. A device for detecting a change in detected object electric resistance due to contact between an electrode and an object to be detected, comprising: a first electric resistance between the level detection electrode and the compensation electrode; and between the compensation electrode and the machine frame. Second electric resistance of the detection object, the electric resistance of the detected object, and the first electric resistance connected between the level detection electrode and the negative potential.
And a second resistor connected between the compensation electrode and the negative potential.
A bridge circuit including a resistor and a balance holding circuit that makes the current flowing through the first electric resistance zero so as to keep the bridge circuit in a balanced state, and in the balanced state of the bridge circuit, An electrode type level detection device formed so as to detect a change in the electrical resistance of the detected object as a level change of the detected object by a change in the current flowing through the first resistor. 2. The electrode type level detection device according to claim 1, wherein the voltage between the output terminal of the balance holding circuit and the negative potential is detected as a stain detection voltage of the insulator.