JPH0792003A - Electrode rod for water level sensor - Google Patents

Abstract

PURPOSE:To prevent the generation of a sensor output, which indicates the existence of water, when no water is detected in water level detection inside a metallic tank. CONSTITUTION:The electrode rod applied to a water level sensor, in which a sensor output is taken out from an intermediate point between a resistor and the electrode rod by connecting one pole side of a power source to the electrode rod installed through a metallic tank top part via the resistor and connecting the other pole side of the power source to the metallic tank, is provided with a first electrode 3, which is installed in the metallic tank 1 top part while insulated with an insulator 6 and is connected to the power source via the resistor, for external output and a second electrode 5, which is installed in a tank inside side end part 3b of the first electrode 3 electrically connected with the metallic body 13 via a connector 11 contactably with water inside the metallic tank 1 and is electrically connected to the end part 3b of the first electrode 3 via the resistor 12, for water level detection.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode rod suitable for a water level sensor for detecting the water level in a metal tank.

[0002]

2. Description of the Related Art Conventionally, as an electrode rod of this type, there is one shown in FIG. 5, for example. In FIG. 5, one end of the electrode rod 2 penetrating the top of the metal tank 1 has the metal tank 1
A first electrode 3 as an electrode for external extraction that is located outside and the other end is located inside the metal tank 1, and a water level detection electrode that is connected to an end of the first electrode 3 on the tank inner side via a connecting fitting 4. And the second electrode 5 as. The intermediate outer peripheral portion of the first electrode 3 is covered with an insulator 6 such as ceramic,
Threaded portions 3a and 3b are formed at both ends of the first electrode 3 protruding from the insulator 6. Further, a mounting metal 7 for mounting the electrode rod 2 on the metal tank 1 is provided on the intermediate outer peripheral portion of the insulator 6. A screw portion 5 a is formed at one end of the second electrode 5. The first electrode 3 and the second electrode 5 are electrically connected to each other by screwing the threaded portions 3b and 5a into the coupling fitting 4, as shown in the figure,
Two electrodes with different lengths can be connected.

Next, the water level detection principle of the water level sensor using the electrode rod 2 having the above structure will be described. First, the electrode rod 2
The second electrode 5 side is inserted into the metal tank 1 and the screw part 7a of the mounting bracket 7 is screwed into the mounting part of the metal tank 1, so that the electrode rod 2 is attached to the top of the metal tank 1 as shown in FIG. Fixed to. Then, as shown in FIG. 6, the threaded portion 3 a, which is the end portion of the first electrode 3 protruding to the outside of the metal tank 1 on the outer side of the tank, is electrically connected to the power source 9 via the resistor 8. The resistance value R _F of the resistor 8 is the resistance value R of water.
_It is usually much larger than _W (several KΩ) (R _F >> R _W ).
It is a thing. In this state, the sensor output can be taken out with the intermediate point between the first electrode 3 and the resistor 8 as the sensor output end OUT. In addition, water is usually put in the metal tank 1 up to the position indicated by the water surface W in FIG.

If there is water in the metal tank 1 (a state where the water surface W is higher than the lower end of the second electrode 5 and the second electrode 5 and the water are in contact with each other), the second electrode 5 and the metal tank 1 do not collect water. It becomes an electrically connected state via. Therefore, water is electrically connected between X and Y in the equivalent circuit of FIG. 7, and the resistance value R _F of the resistor 8 and the resistance value R _{W of} water are connected in series as shown in FIG. It constitutes a closed circuit.

[0005] In this case, when the power supply voltage and E (v) the sensor output V is, V = _{[R W / (R F + R} W) ] · E ··· (1) becomes, for example 100KΩ the R _F, R _{When W} is 1 KΩ and E is 10 v, V = [1 × 10 ³ / (100 + 1) 10 ³ ] · 10 ≈0.1 (v) On the other hand, there is no water in the metal tank 1 (the lower end of the second electrode 5). (The water surface W is at a lower position and the second electrode 5 does not come into contact with water)
In this case, the second electrode 5 and the metal tank 1 are in an insulated state, and the circuit in FIG. 7 is in an electrically insulated state between X and Y.

In this case, the sensor output V becomes V = E (2), which is the power supply voltage E. In this way, the metal tank 1
The value of the sensor output V differs depending on whether or not there is water inside, and the water level in the metal tank 1 is detected based on the change in the sensor output V.

[0007]

By the way, the first electrode 3
The second electrode 5 and the second electrode 5 are normally insulated from the metal tank 1 by the insulator 6.
It is conceivable that the surface (part A in FIG. 5) becomes wet.
In this case, the connection fitting 4 is electrically connected to the metal tank 1 through the water attached to the surface of the insulator 6,
Regardless of the presence or absence of water in the metal tank 1, the resistance value R _W is inserted in series as shown by the broken line in FIG. 7. Then, in this case, in the configuration of the conventional electrode rod 2, as is apparent from the circuit diagram of FIG. 7, in a normal state, the second electrode 5 is electrically connected to the metal tank 1 through water. The circuit configuration is the same, and the sensor output is the same as when there is water, even though there is no water. Therefore, for example, when such an electrode is used in a boiler device or the like, there is a risk that a sensor output with water is generated when there is no water in the tank, and a dangerous state such as empty cooking may occur. was there.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an electrode rod for a water level sensor that never generates a sensor output with water when there is no water.

[0009]

Therefore, according to the present invention, the end of the electrode outside the tank of the electrode rod mounted on the metal tank with an insulator interposed therebetween so as to penetrate the top of the metal tank for storing water is Connect to one pole side of the power supply through the body,
In the electrode rod applied to the water level sensor configured to connect the other pole side of the power source to the metal tank and take the sensor output from the intermediate point between the resistor and the electrode rod, the electrode rod mounting portion of the metal tank An external lead-out electrode that is attached to the metal tank so that one end is located outside the tank and the other end is located inside the tank, and the tank external end is connected to the power source through the resistor; A resistor separate from the resistor is attached to an end of the extraction electrode on the inner side of the tank so as to be able to come into contact with water in a metal tank via a connector, and to an end of the outer extraction electrode on the inner side of the tank. And a water level detection electrode electrically connected via the.

[0010]

In such a structure, by inserting a resistor between the first electrode and the second electrode, water is present in the metal tank and the second electrode and the metal tank are electrically connected via the water. In this case, the external resistor and the resistor between the first electrode and the second electrode are inserted in series in the sensor circuit. On the other hand, in the case of an abnormal state in which the connector part is electrically connected to the metal tank due to the adhesion of water on the surface of the insulator, the first electrode and the second electrode
The resistor between the electrodes is substantially removed from the circuit (reduced in resistance). As a result, the sensor output has different values and can be distinguished between a state with water and an abnormal state in which water is attached to the surface of the insulator and the connector is electrically connected to the metal tank.

Therefore, when there is no water in the metal tank, the sensor output indicating the presence of water is never generated, and by using such an electrode rod, the water level sensor can be made to have a fail-safe structure.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of a first embodiment of an electrode rod for a water level sensor according to the present invention. Incidentally, the same parts as those of the conventional example shown in FIG. In FIG. 1, the electrode rod 10 of this embodiment is a first electrode as an electrode for external extraction.
The electrode 3 and the second electrode 5 as a water level detecting electrode are connected by a connecting tool 11 formed of an insulator such as ceramic, and the first electrode and the second electrode 5 are connected to each other by a resistor inside the connecting tool 11. It is electrically connected via 12. The resistance value R of the resistor 12 is, for example, an extremely large value as compared with the resistance value R _{W of} water (R >> R _W ). Also, the insulator 6
Between the connector and the connector 11, there is interposed a metal body 13 that is screwed into a threaded portion 3b that is an end of the first electrode 3 on the inner side of the tank and electrically connected to the first electrode 3. .

Next, the operation will be described. As shown in FIG. 2, the metal tank 1 is mounted on the top of the metal tank 1 via a mounting bracket 7 as shown in FIG.
The screw part 3 a of the first electrode 3 is connected to the power source 9 and the power source 9. In this state, the power supply voltage is E, the resistance value of the resistor 8 outside the tank is R _F , the resistance value of the resistor 12 between the first electrode 3 and the second electrode 5 is R, and the resistance value of water is R _W.

First, when there is water in the metal tank 1 (the water surface W is higher than the lower end of the second electrode 5 and the second electrode 5 is in contact with water), all the resistances are in the sensor circuit as shown in FIG. in a state of being inserted in series, the sensor output V becomes V = _{[(R + R W) / (} R F + R + R W) ] · E ··· (3).

When there is no water, the second electrode 5 and the metal tank 1 (between X and Y in FIG. 3) are insulated from each other, so that the circuit is opened and the sensor output V is the same as the conventional one. Then, V = E (4) In addition, the surface of the insulator 6 (the portion indicated by A in FIG. 1)
Water adheres to the metal body 13 electrically connected to the first electrode 3 through the water and electrically connected to the metal tank 1 (at the Z position as shown by the dotted line in FIG. 3). for electrically connected) to the metal tank 1 side, if there is no water in the metal tank 1, between X and Y in FIG. 3 becomes open, the sensor output V is, V = [R _W / (R _F + R _W)] · E becomes a ... (5). On the other hand, if there is water in the metal tank 1, X in FIG.
Since the sensor output V is also electrically connected between Y and Y, the sensor output V is V = [R ₀ / (R _F + R ₀ )] · E (6) where R ₀ = R _W (R + R _W ) a / (R + 2R _W).

Here, for example, E = 10v, R _F = 10
If 0 KΩ, R = 100 KΩ, and R _W = 1 KΩ,
From the equation (3), the sensor output V with water is V = [(1 + 100) × 10 ³ / (100 + 100 +)
1) × 10 ³ ] · 10≈5 (v).

Further, the sensor output V without water is
From the equation (4), V = 10 (v). Further, the sensor output V in the abnormal state where the surface of the insulator 6 is wet with water is expressed by the following equation (5) when there is no water: V = [1 × 10 ³ / (100 + 1) × 10 ³ ] · 10 ≈0. 1 (v), and in the case of the presence of water, R ₀ ≈1 and from the equation (6), V = [1 / (100 + 1)] · 10 ≈0.1 (v).

Further, E = 10v, R _F = R = R _W = 1K
Assuming Ω, if there is water in the metal tank from the formula (3), it is about 7v, if there is no water from the formula (4), it is 10v, if there is water in an abnormal state, it is 5v from the formula (5), water In the case of none, the formula (6) becomes about 3v. As described above, in the case of the electrode rod configuration of the present embodiment, the sensor outputs with and without water in the normal state where the surface of the insulator 6 is not wet with water, and the surface of the insulator 6 is exposed to water. The sensor output in a wet abnormal state has different values. Therefore, in the abnormal state, the value does not become the same as the sensor output indicating the presence of water, and at least the sensor output indicating the presence of water does not occur even though the water is not in the metal tank 1. When applied to, it is possible to reliably avoid a dangerous state such as cooking in the air, and it is possible to configure a highly safe water level sensor.

Next, FIG. 4 shows a second embodiment of the electrode rod according to the present invention. The same parts as those in the first embodiment shown in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted. 4, in the electrode rod 20 of the present embodiment, the connecting tool 11 and the metal body 12 are alternately connected by a plurality of metal screw rods 14, and the metal screw rods are electrically connected to each other via the resistor 12. To form a second electrode 5 ', and the uppermost metal screw rod 14 of this second electrode 5'is shown in FIG.
Similarly to the above, the first electrode 3 is electrically connected through the resistor 12.

According to the electrode rod 20 having such a structure,
As in the example, when there is no water, the output with water is generated.
In addition to the effect that there is no
The sensor output varies depending on the position.
The water surface position in the metal tank 1 can be detected in stages
It becomes Noh. That is, the number of the resistors 12 is N, and the second electrode
From the lower end side of 5 ', the resistance value is R _1,R_2,..., R_NWhen
Then, if there is a water surface W on the J-th connecting part from the lower end
When the sensor output V is: V = [(R₁+ R₂+ ・ ・ + R_J) / (R₁+ R₂+ ・
・ + R_N)] · E, and the value of the sensor output V varies depending on the position of the water surface W.
Therefore, the sensor output corresponding to the water level can be obtained.

In each of the embodiments of the present invention, the connector for connecting the first electrode and the second electrode may be made of a semiconductive material such as conductive rubber (rubber containing carbon). In this case, the resistor that electrically connects the two electrodes is not needed, and the connector also serves as the resistor.

[0022]

As described above, according to the present invention, since the resistor is interposed between the first electrode and the second electrode, water adhering to the surface of the insulator around the first electrode can be removed. It is possible to distinguish between an abnormal state in which the metal tank and the first electrode are electrically connected through the state and a state in which water is present in a normal state. Therefore, when applied to a water level sensor, it is possible to provide a water level sensor having a fail-safe configuration that never produces a sensor output with water even though there is no water.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of an electrode rod for a water level sensor according to the present invention.

FIG. 2 is a configuration diagram of a water level sensor to which the electrode rod according to the first embodiment is applied.

FIG. 3 is a circuit diagram for explaining the operation of the first embodiment.

FIG. 4 is a configuration diagram showing a second embodiment of an electrode rod for a water level sensor according to the present invention.

FIG. 5 is a configuration diagram of a conventional electrode rod for a water level sensor.

FIG. 6 is a configuration diagram of a water level sensor to which an electrode rod according to the conventional example is applied.

FIG. 7 is a circuit diagram for explaining the operation of the above conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Metal tank 10,20 Electrode rod 3 1st electrode 5,5 '2nd electrode 6 Insulator 8 Resistor 9 Power supply 11 Connecting tool 12 Resistor 13 Metal body 14 Metal screw rod W Water surface

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Koichi Hobara, 1-13-8 Kamikizaki, Urawa-shi, Saitama Nihon Signal Co., Ltd. Yono Works (72) Masayoshi Sakai 1-1-13 Kamikizaki, Urawa-shi, Saitama No. 8 Japan Signal Co., Ltd. Yono Office

Claims (1)

[Claims] 1. A tank outside end of an electrode rod attached to a metal tank with an insulator interposed so as to penetrate the top of a metal tank for storing water, and one end of one side of a power source through a resistor. In the electrode rod applied to the water level sensor configured to connect the other pole side of the power source to the metal tank and take out the sensor output from the intermediate point between the resistor and the electrode rod, the electrode of the metal tank An electrode for external extraction, which is attached to the rod mounting portion so as to be insulated from the metal tank so that one end is located outside the tank and the other end is located inside the tank, and the outside end of the tank is connected to the power source through the resistor. And a resistor attached to an end of the external extraction electrode on the inner side of the tank so as to be able to contact with water in the metal tank via a connecting tool. Another resistor Electrically water level sensor electrode rod, wherein the water level detecting electrodes, by being configured with a connecting with.