JPH0692908B2 - Interface position detection method and device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for detecting an interface position in a system having one or more interfaces formed from two or more kinds of fluids having different heat transfer coefficients.

[0002]

2. Description of the Related Art Conventionally, there is a method of utilizing the difference in physical properties of substances on both sides of an interface as means for detecting the interface position. For example, by utilizing the difference in specific gravities of two fluids that form an interface, it is possible to measure the interface position by measuring that the apparent weight of the float changes on both sides of the interface when the interface reaches a preset level. A method for detecting the interface position by opening and closing a small sketch provided on the float when the interface position moves, using a means for detecting and a float that falls due to displacement of the interface based on the difference in specific gravity between two fluids was there. However, in the technology that utilizes the change in the apparent weight of the float on both sides of the interface, the system that measures the weight change of the float affects the apparent weight of the float,
It is practically difficult to reduce the weight of the float.

Further, in the technology utilizing the fall of the float due to the change of the interface position, it is practically difficult to downsize the sensor for detecting the fall of the float, and the electric signal is taken out from the sensor. It was difficult to protect the conducting wire for the above, and it could not be used in a closed container in many cases. Furthermore, by utilizing the difference in the optical refractive index or the total reflection angle on both sides of the interface, if the interface contacts a part of the optical waveguide, light scattering and a change in the waveguide path occur, Although there is a method to detect the existence of the interface by this, the optical waveguide tends to be expensive in this technology, and it is often the case that an optically active metal surface near the interface position detection end, for example, has a high reflectance. It malfunctioned and could not be put to practical use. Alternatively, there is a means for detecting the position of the interface by utilizing the difference in electrical conductivity on both sides of the interface, but it has not been possible to detect the interface between fluids having low electrical conductivity.

Further, the heating element and the temperature sensor are paired, and the temperature rise of the sensor due to a constant amount of heat generated by the heating element is different between two or more fluids forming an interface. The temperature sensor shows a low temperature in the phase with high thermal conductivity or large specific heat and the temperature in the phase with low thermal conductivity or small specific heat There has also been a method of utilizing the property that the sensor exhibits a high temperature. However, the method of detecting the interface position by utilizing the difference in heat transfer resistance between the fluids on both sides of the interface causes a malfunction due to a change in ambient temperature. Therefore, a pair of elements including a heating element and a temperature sensor are combined. , A total of two sets are installed on both sides of the interface so as to cancel the uniform temperature change of the entire system under test, but since each element is located at a specific position, There is a problem in that the uneven distribution due to heat and the disturbance cannot be canceled out, and a malfunction easily occurs.

Therefore, the present applicant has improved the above-mentioned problems inherent in this type of conventional method and apparatus and substantially eliminates the occurrence of malfunction of the apparatus due to thermal non-uniformity of the system to be measured and disturbance. Developed a new technology and applied for a patent application (Japanese Patent Application No. 1-158426), but the object of the invention is, in principle, compact formation and cost reduction. In view of the above, it is an object of the present invention to provide an interface position detecting apparatus and method that can be used for detecting a fluid interface in a closed container and that is not affected by optical disturbance.

[0006]

DISCLOSURE OF THE INVENTION The present invention is a further improvement of the above-mentioned technology for which a patent application was filed, and uses two small temperature-sensitive elements having different resistance values to cause self-heating. As a result, the interface position detecting means can be made more compact, and two sheath tubes having a small diameter can be used, the heat capacity can be reduced, and the interface change measuring method and device having a quicker response can be obtained. Aim to get. Further, another object is to develop the present detection method and device which can be provided at a practical cost despite the improvement in line with the above-mentioned object.

[0007]

In order to achieve the above-mentioned object, the present invention has the respective constituents as described below. (1) Two sensing elements having different resistance values are connected in parallel, and a pair of sensing elements are arranged in the measured system so that the sensing element positions are horizontal. A current is passed through the temperature element to the extent that the element can sufficiently heat up due to self-heating, and a current that causes only a temperature rise that can be ignored by the element due to self-heating is passed to the other temperature sensitive element. Through
By utilizing the fact that the temperature difference between the two temperature-sensitive elements changes in accordance with each phase with the interface composed of at least two-phase fluids in the system under measurement as a boundary, the position of the interface can be determined. How to measure. (2) At least two or more pairs of sensing pairs each consisting of a pair of temperature sensitive elements are arranged vertically in the system to be measured, and one of the temperature sensitive elements is placed in a known fluid phase. It is set as the reference value of the temperature difference of the sensing pair, and by comparing this with the temperature difference value of the temperature sensing element of the other set, the phase where the temperature sensing element of the other set is placed is detected, How to measure position. (3) Two temperature-sensitive elements having different resistance values are connected in parallel, and a pair of detection elements are arranged in the measured system so that the position of each temperature-sensitive element is horizontal. A current is passed through the temperature element to the extent that the element can sufficiently heat up due to self-heating, and a current that causes only a temperature rise that can be ignored by the element due to self-heating is passed to the other temperature sensitive element. Through
By utilizing the fact that the temperature difference between the two temperature-sensitive elements changes in accordance with each phase with the interface composed of at least two or more phases of fluid in the system under measurement as a boundary, the position of the interface is determined. Measuring device. (4) At least two or more pairs of detection pairs each consisting of two temperature-sensitive elements are arranged vertically in the system to be measured, and one of the temperature-sensitive elements is placed in a known fluid phase. It is set as a reference value of the temperature difference of the sensing pair, and by comparing this with the temperature difference value of the temperature sensitive element of the other set, the phase in which the temperature sensitive element of the other set is placed is detected, and A device that measures position.

[0008]

The operation of the interface position detecting method and apparatus according to the present invention will be described in principle with reference to FIG. 1 as follows. In FIG. 1, TR ₁ , TR ₂ , TR ₃ ,
TR ₄ is a temperature sensitive element, and the temperature sensitive elements TR ₁ and TR ₃ , and the temperature sensitive elements TR ₂ and TR ₄ have the same characteristics and the same resistance value, and the temperature sensitive element TR ₁ (= TR ₃ ) << sense Temperature element TR ₂ (=
TR ₄ ). The temperature-sensitive elements TR ₁ and TR ₂ and the temperature-sensitive elements TR ₃ and TR ₄ are connected in parallel with each other and the same voltage is applied. The applied voltage is the temperature sensitive element TR ₁ (= T
R ₃ ) << Due to the relationship of the temperature sensitive element TR ₂ (= TR ₄ ), the temperature sensitive element TR ₁ (= TR ₃ ) is energized with a current that can be sufficiently heated by self-heating and Temperature element TR
₂ (= TR ₄ ) is supplied with a current that causes only a negligible temperature rise due to self-heating. Both temperature sensitive elements are insulated and insulated from each other.

Temperature sensitive elements TR ₁ , TR ₂ , TR ₃ , TR ₄
At one end of each of the electric resistors R _{1 having} a low temperature coefficient,
R ₂ , R ₃ and R ₄ are connected to each other, and the temperature sensitive element TR ₁ ,
One bridge circuit is formed by TR ₂ and electric resistors R ₁ and R ₂ . The electric resistors R ₁ , R ₂ , R ₃ and R ₄ are
It may be arranged outside the system to be measured. In a resistance bridge circuit formed by a temperature sensitive element and an electric resistor, a terminal C ₂ on one end side of the electric resistor R ₁ , R ₂ , R ₃ , R ₄ and the temperature sensitive elements TR ₁ , TR ₂ , TR ₃ , terminal C ₁ of the one end of the TR ₄
The voltage applied between the resistor R ₁ and the temperature sensitive element R ₁ , the resistor R ₂ and the temperature sensitive element TR _2, and the resistor R respectively.
₃ and the temperature-sensitive element TR ₃ , and the resistor R ₄ and the temperature-sensitive element TR ₄ are divided in voltage, and the connection point P between the resistor R ₁ and the temperature-sensitive element TR ₁ is divided.
₁ and the resistor R ₂ and the connecting point between the temperature sensitive device TR ₂ P ₂
By measuring the voltage change between (a resistor R ₃ thermosensitive element TR ₃ and the connection point P _3, the connecting point P ₄ of the resistor R ₄ and the temperature sensitive element TR _4), the temperature sensing element TR _The difference in the resistance value due to the temperature difference between ₁ and TR ₂ can be read as a voltage.

That is, two kinds of fluids A that form an interface,
If the thermal conductivity of B is A> B and the temperature coefficient of the temperature sensitive element is positive, the resistance value indicated by the temperature sensitive element TR ₁ is low if the element is in the fluid A in FIG. Becomes higher in the fluid B. Further, although the resistance values indicated by the temperature sensitive elements TR ₁ and TR ₂ increase or decrease as a whole due to the temperature rise or fall of the system under measurement, the measurement point P _{1 of} the bridge circuit,
As long as the voltage between P ₂ is measured, the temperature change of the measured system is canceled out, and as a result, it is determined whether the detection pair is in the two-phase fluid A or B having different thermal conductivities. can do. Based on the same principle, even if the temperature distribution changes in the vicinity of the sheath W containing the detection pair in parallel with the interface of the system under measurement, the effect is canceled by the temperature sensitive elements TR ₁ and TR _2. Therefore, also in that case, it can be determined which side of the two phases having different heat transfer coefficients is located. Therefore, once the types of gas phase and liquid phase are determined, it is possible to detect which detection pair the interface position is between within a practical temperature range and within a length range in which a plurality of detection pairs are arranged. obtain.

[0011]

EXAMPLES Some preferred examples of the method and apparatus of the present invention will be described below, but various design changes are possible within the technical level in the art at the time of the application of the present invention. Therefore, the gist of the present invention should not be limitedly interpreted based on only the specific examples described in the present examples without showing a particular reason.

(No. 1) FIG. 1 is a schematic view of an embodiment of the device of the present invention, in which the interface position between air B and water A is to be detected. In FIG. 1, temperature sensitive elements TR ₁ and T
R ₂ , TR ₃ and TR ₄ are, for example, platinum resistance temperature detectors,
A sensor such as a thermistor is covered with glass, epoxy resin or the like and electrically insulated. Sheath W
Is a stainless steel tube having a thickness of 0.15 mm, and the inside of the tube is filled with urethane foam resin to thermally insulate the temperature sensitive elements TR ₁ and TR ₂ and the temperature sensitive elements TR ₃ and TR ₄ . Electric resistor R ₁ =
R ₃ = 100 Ω, temperature sensitive element TR ₁ = TR ₃ = 100 Ω,
Electric resistor R ₂ = R ₄ = 1000Ω, temperature sensitive element TR ₂ = TR
₄ = 1000Ω. Electric resistors R ₁ , R ₂ , R ₃ , R ₄
Used a metal film resistor with a low temperature coefficient.

Temperature sensitive element TR ₁ (= TR ₃ ) << TR ₂ (=
TR ₄ ), and utilizing this relationship, the temperature-sensitive elements TR ₁ and TR ₃ self-heat and heat up sufficiently, and the temperature-sensitive elements TR ₂ and TR ₄ also self-heat. The voltage was applied so that the temperature rise was negligible. A voltage of 2.5 V was applied between terminals C _{1 and} C _{2 in the} atmosphere at 25 ° C.
After a few minutes, the voltages between the terminals P _{1 and} P _{2 and} between the terminals P _{3 and} P ₄ were measured and both were -2.0 mV. 25 this
When immersed in water A at ℃, the voltage between terminals P _{1 and} P ₂ is 2.
It was 5 mV. At this time, the voltage between the terminals P ₃ -P ₄ -
It was 2.0 mV. Thus, between terminal P ₁ -P _2, the voltage corresponding to the phase of the measurement system is obtained, conversely, by measuring the potential difference between the terminals P ₁ -P _2,
It is possible to determine whether one set of temperature sensitive elements is in two different types of A phase or B phase, and by installing a plurality of pairs of these detection elements, which is the interface position? Therefore, it is possible to detect the position change of the interface according to the present embodiment.

(Part 2) The same apparatus as in (Example 1) was used. Atmosphere B of the measured system
The same phase-voltage characteristics as those obtained when the temperature was measured at 20 ° C. and the temperature of the aqueous phase A at 25 ° C. (Example 1) were obtained. Therefore, this example demonstrates that the interface position can be measured stably even if there is a thermal disturbance in one system. (Part 3) The same device as in (Example 1) was used. Atmosphere B of the measured system
The same phase-voltage characteristics as those obtained when the temperature was measured at 30 ° C. and the temperature of the aqueous phase A at 20 ° C. (Example 1) were obtained. Therefore, this example proved that the interface position can be measured stably even if there is a thermal disturbance in one system.

(Part 4) The same apparatus as (Example 1) was used. Atmosphere B of the measured system
The temperature of the aqueous phase A was set to 25 ° C., the temperature of the aqueous phase A was set to 25 ° C., and the same phase as in the case of measuring the temperature of the aqueous phase A by heating from the bottom of the aqueous phase A (Example 1), A voltage characteristic was obtained. Therefore, it was found that this embodiment is practical as a method and apparatus for detecting the interface position without causing an error even if there is a thermal disturbance.

(No. 5) Based on the same principle as (Example No. 1), an apparatus as shown in FIG. 2 was used. That is, in one detection pair, the self-heating temperature sensing element and the temperature sensing element capable of ignoring self-heating are separately housed in two small-diameter sheath tubes to enhance the thermal response speed. . Three detection pairs were installed in each sheath tube. The temperature of the atmosphere B of the measured system is 25 ° C., the temperature of the aqueous phase A is 25 ° C., and the interface is in the state of the interface 1,
Terminals P ₁ -P ₂ , Terminals P ₃ -P ₄ and Terminals P ₅ -P ₆
When the potential difference between each was measured, it was -2.0 mV at all three points. Next, when the sheath tube was dropped into the aqueous phase A and the interface was displaced to the interface 2, the terminal P ₁ was reached in a few seconds.
The potential difference between −P ₂ became 2.5 mV. At this time, terminal P
₃ -P _4, the potential difference between the terminals P ₅ -P ₆ are both -2.0mV
Met.

Next, when the sheath tube was lowered into the aqueous phase A so that the interface was displaced to the interface 3, the potential difference between the terminals P _{3 and} P ₄ became 2.5 mV in a few seconds. At this time, the potential difference between the terminals P _{1 and} P ₂ is 2.5 mV, the terminal P ₅
The potential difference between the -P ₆ was -2.0mV. In this embodiment,
The thermal response speed is increased by reducing the diameter of the sheath tube,
It is possible to make the interface detection device capable of further rapid detection, and by installing a plurality of detection pairs, it is practical to measure the position change of the interface finely.

(Part 6) The same apparatus as in (Example 5) was used. Atmosphere B of the measured system
When the temperature of the water phase A is set to 25 ° C., the temperature of the water phase A is set to 90 ° C., and the interface is set to the interface 1, the terminals P ₁ -P ₂ and the terminal P ₃ −
When the potential difference between P ₄ and terminals P ₅ -P ₆ was measured,
Both were -2.0 mV. Next, when the sheath tube was lowered so that the interface was displaced to the interface 2, the terminal P ₁
The potential difference of −P ₂ was 0.7 mV. Terminal P ₃ at this time
-P _4, the potential difference between the terminals P ₅ -P ₆ were both -2.0 mV. When the interface was further lowered to the interface 3, the potential difference between the terminals P ₁ -P ₂ and the terminals P ₃ -P ₄ was 0.7.
got mV. At this time, the potential difference between the terminals P _{5 and} P ₆ is −
It was 2.0 mV. Therefore, this example shows that it is practical as a method and apparatus for measuring the interface position change without error even at a practically high temperature of the measured system.

(No. 7) The same apparatus as in (Example 5) was used. Atmosphere B of the measured system
At 25 ° C., the temperature of the water phase A at 2 ° C., and the interface at the interface 1 state, the terminals P ₁ -P ₂ and the terminal P ₃ −
When the potential difference between P ₄ and terminals P ₅ -P ₆ was measured,
Both were -2.0 mV. Next, when the sheath tube was lowered so that the interface became the interface 2, the potential difference between the terminals P _{1 and} P ₂ was 2.8 mV. At this time, the potential difference between the terminals P ₃ -P ₄ and the terminals P ₅ -P ₆ was -2.0 mV. Next, when the sheath tube was lowered so that the interface became the interface 3, both the potential differences between the terminals P ₁ -P ₂ and the terminals P ₃ -P ₄ were 2.8 mV. At this time, the potential difference between the terminals P _{5 and} P ₆ was −2.0 mV. Therefore, this embodiment is practical because the change in the interface position can be measured stepwise even when the system under measurement has a practically low temperature.

[0020]

As described above, according to the method and apparatus of the present invention, the detection pair can be either of A and B two phases depending on the practical temperature environment in which the system under measurement is placed. It is possible to determine whether or not there is, and by installing a plurality of pairs of the same pair, it is possible to detect the change in the interface position stepwise. Further, it is possible to substantially eliminate the occurrence of malfunction due to thermal disturbance in the system to be measured or optical disturbance. In addition to being compact in principle, there is no need to secure a space for installation, and the configuration is simplified as much as possible to reduce manufacturing costs. Made possible Further, according to the method and apparatus of the present invention, the interface position can be detected in accordance with the practical temperature environment of the measured system, and so on. Can not,
It has a special action and effect.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an embodiment of the device of the present invention.

FIG. 2 is a schematic view of another embodiment of the device of the present invention.

[Explanation of symbols]

TR ₁ temperature sensing element TR ₂ temperature sensing element R ₁ electric resistor R ₂ electric resistor C ₁ terminal C ₂ terminal P ₁ measuring terminal P ₂ measuring terminal W sheath D urethane foam insulation A water phase B air phase

Claims (4)

[Claims] 1. A temperature-sensing element of a pair of detection elements, each of which is formed by connecting two temperature-sensing elements having different resistance values in parallel, is arranged in the system under measurement so that the position of each temperature-sensing element is horizontal. A current is passed through one temperature-sensitive element to the extent that the element can heat up sufficiently by self-heating, and the other temperature-sensitive element only heats up to a level that can be ignored by the same element due to self-heating. Passing an electric current, the temperature difference value between the two temperature-sensitive elements, by utilizing the fact that it changes depending on each phase, with an interface consisting of fluid of at least two phases or more in the system to be measured as a boundary, A method of measuring the position of an interface. 2. At least two or more detection pairs each consisting of a pair of temperature-sensitive elements are arranged vertically in the system to be measured, and one of the temperature-sensitive elements is used as a known fluid phase. The temperature difference reference value of the detection pair is placed in the inside, and by comparing this with the temperature difference value of the temperature sensing element of the other set, the phase in which the temperature sensing element of the other set is detected, A method of measuring the position of an interface. 3. A temperature-sensing element of a pair of detection elements, each of which is formed by connecting two temperature-sensing elements having different resistance values in parallel, is arranged in the system under measurement so that the position of each temperature-sensing element is horizontal. A current is passed through one temperature-sensitive element to the extent that the element can heat up sufficiently by self-heating, and the other temperature-sensitive element only heats up to a level that can be ignored by the same element due to self-heating. Passing an electric current, the temperature difference value between the two temperature-sensitive elements, by utilizing the fact that it changes depending on each phase, with an interface consisting of fluid of at least two phases or more in the system to be measured as a boundary, A device that measures the position of the interface. 4. At least two or more detection pairs each consisting of a pair of temperature sensitive elements are arranged vertically in the system to be measured, and one of the temperature sensitive elements is used as a known fluid phase. The temperature difference reference value of the detection pair is placed in the inside, and by comparing this with the temperature difference value of the temperature sensing element of the other set, the phase in which the temperature sensing element of the other set is detected, A device that measures the position of the interface.