JP2012173192A - Liquid level detection device and liquid level detection method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of detecting a liquid level using a resistance temperature sensor such that the resistance temperature sensor is prevented from deteriorating and the power consumption is suppressed.SOLUTION: A liquid level detection device includes a liquid level sensor B with a pair of resistance temperature sensors 2a, 2b, and a device body A. The device body A includes a first constant voltage circuit 3a which applies a relatively large constant voltage to one 2a of the resistance temperature sensors; a second constant voltage circuit 3b which applies a fine constant voltage to the other 2b of the resistance temperature sensors; a resistance 4 interposed between the one of the resistance temperature sensors and the first constant voltage circuit, and the other of the resistance temperature sensors and the second constant voltage circuit; a first resistance value measuring circuit 7a which measures the resistance value of the one of the resistance temperature sensors; a second resistance value measuring circuit 7b which measures the resistance value of the other of the resistance temperature sensors; comparing means 8 of receiving and comparing the output of the first resistance value measuring circuit and the output of the second resistance value measuring circuit with each other; and control means 9 of controlling the operation of the whole device.

Description

  The present invention relates to a liquid level detection device and a liquid level detection method using the same, and more particularly, in an apparatus and method for detecting a liquid level using a resistance temperature detector, to suppress deterioration of the resistance temperature detector. The present invention relates to a liquid level detection device capable of suppressing power consumption and a liquid level detection method using the same.

  Conventionally, as a method for detecting the liquid level in a container such as a chemical tank, a liquid level detection device using a liquid level sensor provided with a resistance temperature detector having different heat dissipation constants in the liquid phase and the gas phase has been provided. Has been.

  That is, as a liquid level sensor, a liquid level sensor using light, a capacitance type liquid level sensor, and the like are known. However, in a liquid level sensor using light, a raw material compound is decomposed by light irradiation. Such a problem is not preferable in the case of a capacitance type liquid level sensor because the raw material compound may be decomposed by an electric current (charge). As a liquid level sensor having no dots, a liquid level sensor using a resistance temperature detector is provided.

  Here, the liquid level sensor using a resistance temperature detector will be described. In general, a liquid level sensor using a resistance temperature detector has two protective tubes each enclosing a resistance temperature detector. The two protection tubes are inserted into the container, a relatively large current is passed through the resistance temperature detector in one protection tube, and a minute amount is applied to the resistance temperature detector in the other protection tube. Apply current.

  Then, the resistance temperature detector that has passed a large current generates heat. At this time, the resistance temperature of the resistance temperature detector is different between the liquid phase and the gas phase, that is, the resistance temperature detector is in the liquid phase. Since the heat dissipation constant in this case is larger than the heat dissipation constant in the gas phase, the temperature of the resistance temperature detector in the gas phase is higher than that in the liquid phase.

  This means that the resistance value in the gas phase has a resistance value higher than the resistance value in the liquid phase. It is possible to determine whether the resistance temperature detector is above or below the liquid level by observing the difference from the voltage output of the resistance temperature detector through which a large current flows. That is, when the difference is small, it can be determined that the resistance temperature detector is below the liquid level, and when the difference is large, it can be determined that the resistance temperature detector is above the liquid level. The surface can be detected.

  Here, the basic configuration of the liquid level detecting device 51 using the resistance temperature detector will be described with reference to FIG. 7. In FIG. 7, reference numerals 52 and 53 are resistance temperature detectors provided in the liquid level sensor. It is. 52 is a resistance thermometer on one side, 53 is a resistance thermometer on the other side, a relatively large current is passed through the resistance thermometer 52 on one side, and the resistance thermometer 53 on the other side. A small current is passed through.

  A first constant current circuit 54 for flowing a relatively large constant current is connected to one resistance temperature detector 52, and a small constant current is passed to the other resistance temperature detector 53. A second constant current circuit 55 is connected.

  In addition, the conventional liquid level detection device 51 has an operational amplifier 56 that inputs the terminal voltage of one resistance temperature detector 52 and the terminal voltage of the other resistance temperature detector 53 and outputs the difference voltage therebetween. The output of the operational amplifier 56 is input to the comparator 57.

  Further, the operating point voltage set by the first voltage dividing resistor 58 and the second voltage dividing resistor 59 is input to the comparator 57, and the comparator 57 outputs the output of the operational amplifier 56 and the The operating point voltages are compared.

  In this configuration, when the resistance temperature detectors 52 and 53 are in the gas phase, the terminal voltage of one resistance temperature detector 52 is larger than the terminal voltage of the other resistance temperature detector 53 + the operating point voltage. Therefore, the comparator 57 outputs a high level voltage. On the other hand, when the resistance temperature detectors 52 and 53 are in the liquid phase, the terminal voltage of one resistance temperature detector 52 is changed to the other resistance temperature detector. Since the comparator 57 outputs a low level voltage, the resistance temperature detectors 52 and 53 are in the gas phase or in the liquid phase. Can be discriminated.

Japanese Patent No. 3869169 Japanese Patent No. 30009809 Japanese Patent No. 3985071 Japanese Patent No. 3985072

  However, in the conventional liquid level detection device as described above, since the constant current is supplied to the resistance temperature detector using the constant current circuit, the resistance temperature detector is greatly deteriorated and the power consumption is not increased. The problem of not obtaining

That is, the resistance value of the resistance temperature detector increases as the temperature of the resistance temperature detector increases. At this time, in the conventional constant current method described above, the supplied current value (I) is constant. In addition, as can be derived from the following equation (1), the power consumption increases as the resistance value (R) increases, and the amount of heat generated by the resistance thermometer increases and the resistance of the resistance thermometer becomes severely deteriorated. The problem can be pointed out.
P (heat generation amount) = I ² × R (1)

  Accordingly, the present invention provides an apparatus and method for detecting a liquid level using a resistance temperature detector, and providing a liquid level detection apparatus capable of preventing deterioration of the resistance temperature detector and suppressing power consumption. It is an issue.

The liquid level detection device of the present invention is
Applying a constant voltage of a different voltage to at least one pair of resistance temperature detectors inserted in a container containing a liquid, respectively detecting the resistance value of the pair of resistance temperature detectors, and detecting the detected resistance A liquid level detection device that detects whether the resistance temperature detector is in a liquid phase or a gas phase based on a difference in value, and detects a liquid level,
A liquid level sensor comprising at least one pair of resistance temperature detectors;
A resistance voltage of the pair of resistance thermometers is detected by applying a constant voltage of a different voltage to the at least one pair of resistance thermometers, and the resistance thermometer is in the liquid phase based on the difference between the detected resistance values. An apparatus main body for detecting whether it is inside or in the gas phase,
A first constant voltage circuit for heating one of the resistance temperature detectors by applying a constant voltage having a relatively large voltage value to one of the pair of resistance temperature detectors;
A second constant voltage circuit for applying a constant voltage having a minute voltage value to the other of the pair of resistance temperature detectors;
A resistance circuit interposed between one of the resistance temperature detectors and the first constant voltage circuit;
A resistor circuit interposed between the other resistance temperature detector and the second constant voltage circuit;
A first resistance value measurement circuit for measuring one resistance value of the resistance temperature detector;
A second resistance value measurement circuit for measuring the other resistance value of the resistance temperature detector;
A comparison means for inputting and comparing the output of the first resistance value measurement circuit and the output of the second resistance value measurement circuit;
Control means for controlling the operation of the entire apparatus,
The liquid level can be detected by detecting whether the resistance temperature detector is in a liquid phase or a gas phase based on a comparison result of the comparison means.

And the liquid level detection method of the present invention using this liquid level detection device,
Inserting a pair of resistance thermometers into the container, applying a constant voltage of a relatively large voltage value to one of the pair of resistance thermometers and heating one of the resistance thermometers,
Add a constant voltage of a minute voltage value to the other of the pair of resistance temperature detectors,
While measuring one resistance value of the resistance temperature detector and the other resistance value of the resistance temperature detector,
Compare one resistance value of the resistance temperature detector with the other resistance value of the resistance temperature detector,
The comparison result is compared with a preset value to detect whether the resistance temperature detector is in the liquid phase or in the gas phase, and the liquid level in the container is detected.

  In the liquid level detection device and the liquid level detection method of the present invention, the resistance value between one of the resistance temperature detectors heated by applying a relatively large current and the other of the resistance temperature detectors to which a minute current can be applied. In the liquid level detecting device and method for detecting whether the resistance temperature detector is in the liquid phase or in the gas phase based on the difference between the resistance temperature detectors, a constant voltage is applied to each of the resistance temperature detectors. Therefore, this makes it possible to suppress self-heating of the resistance temperature detector and to reduce power consumption.

That is, as shown in the following equation (2), the current value (I) is inversely proportional to the resistance value (R), but in the present invention, the voltage (E) is constant in order to apply a constant voltage to the resistance temperature detector. For this reason, when the resistance value (R) of the resistance temperature detector increases with the temperature rise of the resistance temperature detector, the current value (I) decreases.
I = E / R (2)

  Further, as derived from the equation (1), when the current value is reduced, the amount of heat generated by the resistance temperature detector is also reduced.

  Therefore, according to the present invention, when the temperature of the resistance thermometer increases by supplying power to the resistance thermometer, and the resistance value of the resistance thermometer increases, the power consumption decreases and It is possible to obtain an effect that the self-heating amount of the temperature resistor is also lowered.

It is a block diagram which shows the structure of the Example of the liquid level detection apparatus of this invention. It is a flowchart for demonstrating the Example of the liquid level detection method of this invention. It is a side view which shows the structure of the liquid level sensor used for the Example of the liquid level detection apparatus of this invention. It is a partial cross section for demonstrating the protective tube which comprises the liquid level sensor used for the Example of the liquid level detection apparatus of this invention. It is a figure which shows the relationship between the reinforcement member and protective tube which comprise the liquid level sensor used for the Example of the liquid level detection apparatus of this invention. It is a figure for demonstrating the usage method of the liquid level sensor used for the Example of the liquid level detection apparatus of this invention. It is a block diagram for demonstrating the structure of the conventional liquid level detection apparatus.

  The liquid level detection device according to the present invention applies a constant voltage of a different voltage to at least one pair of resistance temperature detectors inserted in a container containing a liquid, and a pair of resistance temperature detectors to which a constant voltage is applied. The liquid level detection device detects the liquid level by detecting whether the resistance temperature detector is in the liquid phase or in the gas phase based on the difference between the detected resistance values. The resistance of the pair of resistance thermometers by applying a constant voltage of a different voltage to the liquid level sensor equipped with the resistance thermometer and at least one pair of resistance thermometers provided in the liquid level sensor. An apparatus main body is provided for detecting each value and detecting whether the resistance temperature detector is in the liquid phase or the gas phase based on the difference in the detected resistance values.

  The apparatus main body includes a first constant voltage circuit for heating one of the temperature measuring resistors by applying a constant voltage having a relatively large voltage value to one of the pair of temperature measuring resistors, and a pair of the temperature measuring resistors. And a second constant voltage circuit for applying a constant voltage having a minute voltage value to the other of the temperature resistors.

  The apparatus main body includes a resistance circuit interposed between one of the resistance temperature detectors and the first constant voltage circuit, and a resistance circuit interposed between the other of the resistance temperature detectors and the second constant voltage circuit. Each of these resistor circuits includes a current adjusting resistor and a reference resistor.

  Further, the apparatus main body includes a first resistance value measurement circuit for measuring one resistance value of the resistance temperature detector, and a second resistance value measurement circuit for measuring the other resistance value of the resistance temperature detector. And a comparison means for inputting and comparing the output of the first resistance value measurement circuit and the output of the second resistance value measurement circuit, and further controls the operation of the entire apparatus. The control means for doing is provided.

  Then, based on the comparison result of the comparison means, it is possible to detect whether the resistance temperature detector is in the liquid phase or in the gas phase, thereby making it possible to detect the liquid level of the liquid in the container.

  That is, in the liquid level detection method of the present invention using the liquid level detection device configured as described above, a pair of resistance temperature detectors are inserted into a container, and one of the resistance temperature detectors is relatively large. A constant voltage having a voltage value is applied to heat one of the resistance temperature detectors, and a constant voltage having a minute voltage value is applied to the other resistance temperature sensor.

  And while measuring one resistance value of the resistance temperature detector and the other resistance value of the resistance temperature detector, respectively, comparing one resistance value of the resistance temperature detector and the other resistance value of the resistance temperature detector, By comparing the comparison result with a preset value, it is detected whether the resistance temperature detector is in the liquid phase or in the gas phase, and the liquid level in the container is detected.

  Here, when one resistance value of the resistance temperature detector coincides with the other resistance value of the resistance temperature detector, it is determined that the resistance temperature detector is in the liquid phase, and one resistance value of the resistance temperature detector When the resistance value is larger than the other resistance value of the resistance temperature detector, the voltage value, resistance, etc. applied to the resistance temperature detector are adjusted so that it can be determined that the resistance temperature detector is in the gas phase. Good.

  An embodiment of the liquid level detection device of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the liquid level detection device of the present embodiment, where 1 is the liquid level detection of the present embodiment. Device.

  And the liquid level detection apparatus 1 of a present Example has the liquid level sensor equipped with the resistance temperature element inserted in the container which put the liquid, The said resistance temperature sensor is at least one pair. It has.

  In addition, the liquid level detection device 1 of the present embodiment applies a constant voltage of a different voltage to the pair of resistance temperature detectors, detects the resistance value of each resistance temperature detector, and detects the detected resistance value. An apparatus main body for detecting whether the resistance temperature detector is in a liquid phase or a gas phase is provided based on the difference between the two.

  That is, in the figure, A is the apparatus main body, and in the figure, B is the liquid level sensor, and the liquid level sensor B is provided with at least two temperature measuring resistors 2a and 2b that are paired with each other. In this embodiment, the resistance temperature detectors 2a and 2b are both made of Pt1000.

  In the present embodiment, a constant voltage having a relatively large voltage value is applied to one of the temperature measuring resistors (referred to as “one temperature measuring resistor 2a”) by the apparatus main body A, thereby The other resistance temperature detector 2a (referred to as "the other resistance temperature detector 2b") is applied with a constant voltage having a minute voltage value.

  And while detecting the resistance value of each resistance temperature detector 2a, 2b which added the constant voltage, the resistance value of one resistance temperature detector 2a and the resistance value of the other resistance temperature detector 2b are compared, and it is a difference It is possible to detect whether the resistance temperature detectors 2a and 2b are in the liquid phase or in the gas phase.

  That is, in FIG. 1, the apparatus main body A is used to apply a constant voltage to the first resistance temperature detector 2a and a first constant voltage circuit 3a for applying a constant voltage to the one resistance temperature detector 2a. A second constant voltage circuit 3b is included. Then, the first constant voltage circuit 3a applies a constant voltage having a relatively large voltage value to the one resistance temperature detector 2a, thereby heating the one resistance temperature detector 2a, and the second constant voltage circuit 3b. Is used to apply a small constant voltage to the other resistance temperature detector 2b. In this embodiment, the constant voltage circuits 3a and 3b are constituted by a one-chip microcomputer.

  Each of the first constant voltage circuit 3a and the second constant voltage circuit 3b is connected to a resistor circuit 4 having a current adjusting resistor 5 and a reference resistor 6. The first constant voltage circuit 3a and one resistance temperature detector 2a, and the second constant voltage circuit 3b and the other resistance temperature detector 2b, respectively.

  In the figure, reference numerals 7a and 7b denote resistance value measuring circuits. That is, in the apparatus main body A in this embodiment, the first resistance value measuring circuit 7a that measures the resistance value of the one resistance temperature detector 2a and the second resistance value of the other resistance temperature detector 2b are measured. The resistance value measurement circuit 7b is a resistance value measurement circuit based on the Wheatstone bridge method.

  In addition, the apparatus main body A in this embodiment has a comparator. That is, 8 is a comparator in the figure, and in the liquid level detection device 1 of the present embodiment, the comparator 8 compares the resistance value of the resistance temperature detector 2a2b measured by the resistance value measuring circuits 7a and 7b. Thus, the difference is obtained.

  That is, the difference between the resistance value of one resistance temperature detector 2a and the resistance value of the other resistance temperature detector 2b is obtained by the comparator 8, and the result indicates whether the resistance temperature detectors 2a, 2b are in the liquid phase. It is decided to determine whether it is in phase.

  Specifically, when the resistance temperature detectors 2a and 2b are in the liquid phase, there is no difference between the resistance value of one resistance temperature detector 2a and the resistance value of the other resistance temperature detector 2b. When the resistance value of the resistance temperature detector 2a matches the resistance value of the resistance temperature detector 2b and the resistance temperature detectors 2a, 2b are in the gas phase, the resistance value of the resistance temperature detector 2a is The constant voltage value, current adjustment resistance, reference resistance, and the like applied to the resistance temperature detectors 2a and 2b are adjusted in advance so as to be larger than the resistance value of the resistance temperature detector 2b.

  And in the apparatus main body A in a present Example, according to the difference of the resistance value of one resistance temperature sensor 2a calculated | required by the said comparator 8, and the resistance value of the other resistance temperature sensor 2b, a resistance temperature sensor is provided. The display device 11 such as an LED having a different color is operated depending on whether it is in a liquid phase or in a gas phase.

  That is, in the figure, reference numeral 9 denotes a microcomputer as a control unit for controlling the overall operation of the apparatus main body A. The microcomputer 9 includes a switch group 10, a display device 11 such as an LED, a power source and the like (not shown). ), And the comparator 8 and the constant voltage circuits 2a and 2b are connected. In response to the output of the comparator 8, the temperature measuring resistors 2a and 2b are The operation of the display device 11 is controlled by determining whether it is in the phase or in the gas phase. When it is in the liquid phase, the LED corresponding to the liquid phase is turned on. The corresponding LED is turned on.

  Next, an embodiment of the liquid level detection method using the liquid level detection device 1 of the present embodiment configured as described above will be described with reference to the flowchart of FIG. A pair of resistance temperature detectors 2a, 2b provided in the liquid level sensor B is inserted into the container containing the.

  In this state, a constant voltage having a relatively large voltage value is applied to one resistance temperature detector 2a from the first constant voltage circuit 3a, thereby heating one resistance temperature detector 2a and the other temperature measurement resistor 2a. A constant voltage having a minute voltage value is applied to the temperature resistor 2b (S1).

  The resistance value of one resistance temperature detector 2a and the resistance value of the other resistance temperature detector 2b are measured by the first resistance value measurement circuit 7a and the second resistance value measurement circuit 7b, respectively (S2). The resistance values output from the first resistance value measuring circuit 7a and the second resistance value measuring circuit 7b are compared by the comparator 8, and the resistance value of one resistance temperature detector 2a and the other resistance temperature detector The difference between the resistance values 2b is obtained (S3).

  Then, according to the output of the comparator 8, based on a preset criterion, the controller 9 determines whether the resistance temperature detector is in the liquid phase or in the gas phase (S4). Different LEDs are turned on (S5). Specifically, in this embodiment, the value of the constant voltage applied to the resistance temperature detectors 2a and 2b, the current adjustment resistance, the reference resistance and the like are adjusted in advance, and the resistance temperature detectors 2a and 2b are liquid. When in phase, the resistance value of one resistance temperature detector 2a matches the resistance value of the other resistance temperature detector 2b, and the difference becomes 0, and the resistance temperature detectors 2a, 2b are in the gas phase. Sometimes, the resistance value of one resistance temperature detector 2a is set larger than the resistance value of the other resistance temperature detector 2b, and the controller 9 outputs the resistance value based on this reference. Judging according to the difference in resistance value, the LED corresponding to the gas phase or the liquid phase is turned on.

  As described above, in the liquid level detection apparatus 1 of the present embodiment, the liquid level is detected using the resistance temperature detectors having different heat dissipation constants in the liquid phase and in the gas phase, and thus light is used. Unlike the liquid level detector using a liquid level sensor or a capacitance type liquid level sensor, the resistance value of a resistance temperature detector with a large constant voltage and a constant voltage with a small voltage It is possible to determine whether the resistance temperature detector is above or below the liquid level only by looking at the difference from the resistance value of the resistance temperature detector to which the temperature is added.

At this time, in the liquid level detection device of the present embodiment, since a constant voltage is applied to the resistance temperature detector, the resistance value (R) of the resistance temperature detector is increased with the temperature rise of the resistance temperature detector. As it becomes clear from the following equation (2), the current value (I) becomes smaller as the value becomes larger. This makes it possible to suppress self-heating of the resistance temperature detector and to reduce power consumption.
I = E / R (2)

Further, as derived from the following equation (1), when the current value (I) decreases, the amount of heat generated by the resistance temperature detector also decreases.
P (heat generation amount) = I ² × R (1)

  Therefore, according to the liquid level detection device of the present embodiment, when the temperature of the resistance thermometer increases by supplying power to the resistance thermometer, and the resistance value of the resistance thermometer increases, the power consumption It is possible to obtain an effect that the self-heating amount of the resistance temperature detector is also reduced.

  Next, a specific example of the liquid level sensor B according to the present invention will be described. FIG. 3 is a side view for explaining the configuration of the liquid level sensor B in the present example.

  The liquid level sensor B in this embodiment has a plurality of protective tubes, and a resistance temperature detector is inserted into each of the plurality of protective tubes.

  That is, in the figure, reference numeral 22 denotes a protective tube. In this embodiment, the protective tube 22 includes two protective tubes each having the same length, for a total of four. Thus, the liquid level can be detected at two locations in the container. Specifically, a pair of short protective tubes for detecting when the remaining amount of the chemical solution in the container becomes small, Equipped with a pair of long protective tubes to detect when the chemical solution is gone.

  In the present embodiment, the protective tube 22 includes a protective tube main body having a predetermined length and a predetermined diameter, and a detection unit connected to the tip of the protective tube main body. The diameter is smaller than the tube body.

  That is, in the drawing, reference numeral 23 denotes a protective tube body. In this embodiment, the protective tube body 23 has a protective tube body 23a on one side having a total length of 116 mm and a protective tube body 23b on the other side having a total length of 106 mm. These protective tubes 23a and 23b are both in the form of hollow pipes and have an outer diameter of 3.2 mm.

  And the detection part is connected with the front-end | tip part of these protection tube main bodies 23a and 23b, respectively. That is, in the figure, reference numeral 24 denotes a detection portion. In this embodiment, each detection portion 24 is a hollow pipe shape having an outer diameter of 2.3 mm and an overall length of 50 mm, and the protective tube main bodies 23a, 23b and Are communicated with the protective tube main bodies 23a and 23b.

  In this embodiment, the protective tube main bodies 23a, 23b and the detection unit 24 are connected by step welding, but it is not always necessary to connect the protective tube main bodies 23a, 23b and the detection unit 4 by welding. In addition, for example, the detection unit 24 may be formed by swaging the tip portions of the protective tube main bodies 23a and 23b.

  Here, FIG. 4 is a view showing a cross section of a part of the protective tube 22, in which 2a and 2b are the resistance temperature detectors. The resistance temperature detectors 2 a and 2 b are inserted into the detection unit 24 and connected to the apparatus main body A through lead wires 26.

  In addition, the detection unit 24 in the present embodiment has a spherical tip at the tip thereof, whereby the remaining amount of the chemical solution in the container decreases, and the liquid level of the chemical solution is below the detection unit 24. Sometimes, it is possible to prevent the chemical solution from remaining at the tip of the detection unit 24.

  Next, in FIG. 3, reference numeral 27 denotes a mounting portion. That is, the liquid level sensor B is used by being inserted into the chemical solution container. At this time, in this embodiment, the protective tube 23a, 23b is arranged in the chemical solution container by the mounting portion 27. .

  That is, the attachment portion 27 in the present embodiment is connected to the proximal end portion of the protective tube 22 at one end side, and in use, the surface connecting the protective tube 22 faces the chemical solution container side, It is connected to a port formed on the upper surface of the container.

  In addition, a tube 28 is connected to the other end of the mounting portion 27, and the lead wire 26 connected to the resistance temperature detectors 2 and 3 is inserted into the tube 28. ing.

  A connector 30 is provided on the proximal end side of the tube 28, and the temperature measurement is performed via the lead wire 26 by connecting the connector 30 to a connector (not shown) of the apparatus main body A. The resistors 2a and 2b are connected to the apparatus main body A, thereby making it possible to apply a constant voltage to the temperature measuring resistors 2a and 2b and to measure the resistance values of the temperature measuring resistors 2a and 2b.

  Accordingly, by attaching the mounting portion 27 to the upper surface of the chemical solution container and connecting the connector 30 to the apparatus main body A, the protective tubes 22 are respectively inserted into the chemical solution containers, and the temperature measurement in the protective tube 22 is further performed. By applying a constant voltage to the resistors 2a and 2b and measuring the resistance value of the resistance temperature detector, it is possible to detect the remaining amount of the chemical solution in the chemical solution container.

  Next, in FIG. 3, 29 is a reinforcing member for preventing damage to the protective tube 22 and the like. That is, the liquid level sensor B of the present embodiment includes a reinforcing member for preventing the protective tube 22 from being damaged when vibration is applied to the container.

  The reinforcing member 29 in this embodiment has an endless belt shape with a rectangular front body shape, and the four protective tubes 22 are fixed to the four corners on the inner peripheral side of the reinforcing member 29. is doing.

  Here, FIG. 5 is a figure for demonstrating the relationship between the said reinforcement member 29 and the said protective tube 22, and has shown the state seen from the front side. As shown in FIG. 3, the reinforcing member 29 is provided in the vicinity of the distal end side of the protective tube main body 23 in the protective tube 22, and the inner wall of the reinforcing member 29 and the protective tube main body 23 are provided. The protective tube 22 is arranged at the four corners on the inner peripheral side of the reinforcing member 29 so that the outer peripheral portion abuts.

  Further, in this state, the outer peripheral portion of the protective tube main body 23 and the contact portion on the inner wall of the reinforcing member 29 are fixed by welding. Therefore, in the liquid level sensor B of the present embodiment, it is possible to prevent the protective tube 22 from being damaged when vibration is applied to the container, and it is easy to process the reinforcing member, and to reduce the cost. Is possible.

  Further, at this time, in the present embodiment, the reinforcing member 29 has its four corners on the inner peripheral side curved in an arc shape, as is apparent from FIG. The shape is in line with the arc shape of the outer periphery.

  Therefore, according to the present embodiment, it is possible to prevent a space from being formed between the outer periphery of the protective tube main body 23 and the four corner portions on the inner peripheral side of the reinforcing member 29, and the protective tube 22 is made strong. It is possible to fix the protective member 29 and prevent the protective tube 22 from being damaged.

  Then, the case where the liquid level of the liquid in the container is detected using the liquid level sensor B of the present embodiment configured as described above will be described with reference to FIG. 6. In FIG. Is a chemical solution in the chemical solution container 31, and 33 is a liquid level of the chemical solution 32.

  When the liquid level is detected by using the liquid level sensor B, the attachment portion 27 is attached to the upper surface of the chemical liquid container 31, thereby disposing the protective tube 22 in the chemical liquid container 31. .

  At the same time, as described above, by connecting the connector 30 provided on the proximal end side of the tube 28 to the connector of the apparatus main body A, the resistance temperature detectors 2a, 2b and the like are connected via the lead wire 26. Connect the device main body A.

  In that state, for each of the resistance temperature detectors 2a and 2b accommodated in the two pairs of protective tubes 22, a constant voltage having a relatively large voltage value is applied to one resistance temperature detector 2a. The other resistance temperature detector 2b is applied with a constant voltage of a minute voltage value, and the resistance value of each resistance temperature detector 2a, 2b is measured, and one of the resistance temperature detectors having a large voltage value constant voltage is applied. The difference between the resistance value of the resistor 2a and the resistance value of the other resistance temperature detector 2b to which a constant voltage of a minute voltage value is applied is compared, and the resistance temperature detectors 2a and 2b are in the liquid phase based on the difference. Whether the gas phase is in the gas phase or not, the LED corresponding to the gas phase or liquid phase is turned on.

  Therefore, in the liquid level detection device 1 of the present embodiment, the resistance temperature detector can be disposed in the container only by attaching the liquid level sensor 1 to the upper surface of the container. Work is very easy.

  Further, in the liquid level sensor 1 of the present embodiment, a reinforcing member 29 having an endless belt shape with a square front shape is used, and the inner wall of the reinforcing member 29 and the outer periphery of the protective tube main bodies 23a and 23b. The protective tube 22 is disposed at the four corners on the inner peripheral side of the reinforcing member 29 so that the portions abut, and in this state, the outer peripheral portions of the protective tube main bodies 23a and 23b and the inner wall of the reinforcing member 29 are connected. Since it is fixed by welding, it is possible to prevent the protective tube 22 from being damaged when vibration is applied to the container, and it is easy to process the reinforcing member and to reduce the cost.

  Further, in the present embodiment, the reinforcing member 29 has the four corners on the inner peripheral side curved in an arc shape, and the curved shape is a shape along the outer peripheral shape of the protective tube main bodies 23a and 23b. Therefore, it is possible to prevent a space from being formed between the outer periphery of the protective tube main bodies 23a and 23b and the four corners on the inner peripheral side of the reinforcing member 29, and the protective tube 22 is firmly fixed to the reinforcing member 29. It is possible to prevent the protection tube 22 from being damaged.

  In the apparatus and method for detecting a liquid level using a resistance temperature detector, the present invention makes it possible to prevent deterioration of the resistance temperature detector and suppress power consumption. The present invention can be applied to any apparatus and method for detecting a surface.

DESCRIPTION OF SYMBOLS 1 Liquid level detection apparatus A Apparatus main body B Liquid level sensor 2a One resistance temperature sensor 2b The other resistance temperature sensor 3a 1st constant voltage circuit 3b 2nd constant voltage circuit 4 Resistance circuit 5 Current adjustment resistance ( R1)
6 Reference resistance (Rref)
7a First resistance value measurement circuit 7b Second resistance value measurement circuit 8 Comparator 9 Control unit 10 Switch group 11 Display device 22 Protection tube 23a, 23b Protection tube body 24 Detection unit 26 Lead wire 27 Attachment portion 28 Tube 29 Reinforcement Member 30 Connector 31 Chemical liquid container 32 Chemical liquid 33 Liquid surface

Claims (7)

The resistance of the pair of temperature measuring resistors (2a, 2b) is obtained by applying a constant voltage of a different voltage to at least the pair of temperature measuring resistors (2a, 2b) inserted in the container containing the liquid. A liquid level detection device that detects the liquid level by detecting whether the resistance temperature detector (2a, 2b) is in the liquid phase or in the gas phase based on the difference between the detected resistance values. There,
A liquid level sensor (B) comprising the at least one pair of resistance temperature detectors (2a, 2b);
The resistance value of the pair of temperature measuring resistors (2a, 2b) is detected by applying constant voltages of different voltages to the at least one pair of temperature measuring resistors (2a, 2b) and the difference between the detected resistance values. An apparatus main body (A) for detecting whether the resistance temperature detector is in a liquid phase or a gas phase based on the above-mentioned apparatus main body (A),
A first constant voltage circuit (3a) for heating one of the resistance temperature detectors by applying a constant voltage having a relatively large voltage value to one of the pair of resistance temperature detectors (2a);
A second constant voltage circuit (3b) for applying a constant voltage of a minute voltage value to the other (2b) of the pair of resistance temperature detectors;
A resistance circuit (4) interposed between one of the resistance temperature detectors (2a) and the first constant voltage circuit (3a);
A resistance circuit (4) interposed between the other temperature measuring resistor (2b) and the second constant voltage circuit (3b);
A first resistance value measurement circuit (7a) for measuring the resistance value of one of the resistance temperature detectors (2a);
A second resistance value measurement circuit (7b) for measuring the resistance value of the other (2b) of the resistance temperature detector;
Comparison means (8) for inputting and comparing the output of the first resistance value measurement circuit (7a) and the output of the second resistance value measurement circuit (7b);
Control means (9) for controlling the operation of the entire device,
The liquid level can be detected by detecting whether the resistance temperature detector (2a, 2b) is in a liquid phase or a gas phase based on the comparison result of the comparison means (8). Detection device.   The liquid level detection device according to claim 1, wherein each of the resistance circuits (4) includes a current adjustment resistor (5) and a reference resistor (6). The liquid level sensor (B)
A plurality of protective tubes (22) each enclosing a resistance temperature detector (2a, 2b);
An attachment portion (27) for attaching the plurality of protection tubes (22) to a container, to which proximal ends of the plurality of protection tubes (22) are coupled;
A reinforcing member (29) to which the plurality of protective tubes (22) are fixed,
Each of the plurality of protective tubes (22) is
A protective tube body (23) having a base end connected to the mounting portion (27);
The diameter of the protective tube main body (23) connected to the distal end portion of the protective tube main body (23) is made smaller and the distal end portion is formed in a spherical shape, and the resistance temperature detectors (2a, 2b) are provided inside. A detector (24) disposed,
The reinforcing member (29) has an endless belt shape,
The protective tube (22) is disposed on the inner peripheral side of the reinforcing member (29) so that the inner wall of the reinforcing member (29) and the outer peripheral portion of the protective tube (22) are in contact with each other. The liquid level detection device according to claim 1, wherein an outer peripheral portion of the liquid member is fixed to an inner wall of the reinforcing member by welding.   The liquid level detection device according to claim 3, wherein the reinforcing member (29) is formed in a prismatic shape, and the protective pipe (22) is disposed on inner wall portions at four corners of the reinforcing member (29). .   The liquid level detection device according to claim 4, wherein the four corners on the inner peripheral side of the reinforcing member (29) are curved along the outer peripheral shape of the protective tube (22). A method for detecting a liquid level in a container using the liquid level detection device according to claim 1 or 2,
The at least one pair of resistance temperature detectors (2a, 2b) is inserted into the container,
Applying a constant voltage of a relatively large voltage value to one (2a) of the pair of resistance thermometers to heat one of the resistance thermometers,
Apply a constant voltage of a minute voltage value to the other (2b) of the pair of resistance temperature detectors,
While measuring the resistance value of one (2a) of the resistance temperature detector and the resistance value of the other (2b) of the resistance temperature detector,
Comparing the resistance value of one of the resistance temperature detectors (2a) and the resistance value of the other resistance temperature detector (2b);
By comparing the comparison result with a preset value, it is detected whether the resistance temperature detector (2a, 2b) is in the liquid phase or in the gas phase, and the liquid level in the container is detected. Liquid level detection method. When the resistance value of one of the resistance temperature detectors (2a) and the resistance value of the other resistance temperature detector (2b) match, it is determined that the resistance temperature detector pair (2a, 2b) is in the liquid phase;
When the resistance value of one of the resistance temperature detectors (2a) is larger than the resistance value of the other resistance temperature detector (2b), it is determined that the resistance temperature detector pair (2a, 2b) is in the gas phase. The liquid level detection method according to claim 6.

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