KR20220126547A - Method for Temperature Compensation by Controlling Frequency and Mutual Inductance Type Liquid Level Detector Using the Same - Google Patents

Abstract

A temperature compensation method of a mutual induction current type level gauge includes the following steps of: measuring, under a first temperature, a first induced electromotive force by a mutual induction current type level gauge to which power having a first current and a first frequency is supplied; measuring, under a second temperature, a second induced electromotive force by the mutual induction current type level gauge to which power having the first current and a first frequency is supplied; measuring the first induced electromotive force and the second induced electromotive force while changing the first frequency; deriving the first frequency as an optimal frequency when a difference between the first induced electromotive force and the second induced electromotive force is minimized; and supplying the power having the first current and the optimum frequency to the mutual induction current type level gauge. Therefore, temperature compensation of the mutual induction current type liquid level gauge can be performed quickly, accurately, and comfortably without a conventional complicated temperature compensation circuit.

Description

Method for Temperature Compensation by Controlling Frequency and Mutual Inductance Type Liquid Level Detector Using the Same

A method for temperature compensation through frequency control and a mutual induction current type level gauge using the same are provided.

In test facilities or industrial facilities that use or handle liquids (including liquid metals), there are many containers with free liquid level, and information on their liquid level is very important in various operating conditions including incidents and accidents. is needed

If a sudden change in level occurs during normal operation in a test facility or industrial facility, it means that the liquid inside the facility has leaked to the outside of the facility due to partial damage to the facility, or a leak or malfunction of the shut-off valve of the connecting pipe has occurred. If the liquid is toxic or alkali-based, when the liquid leaks outside, damage to human life and damage to facilities due to fire cannot be avoided.

Of course, if a facility or sensor for detecting liquid leakage is provided, damage from an accident can be minimized before it escalates to a major accident. It can detect and respond quickly, and it can be an indicator to confirm whether the facility is operating stably under various operating conditions.

In the meantime, various methods and devices for accurately measuring the liquid level have been devised. In particular, a contact-type level gauge that generates a level signal when the liquid level and the level sensor (electrode) comes into contact is widely used for reasons of intuitive level confirmation, simplicity of operation principle, convenience of maintenance and repair, and low price. Continuous level measurement is impossible because only a predetermined level can be measured, and when the electrode is energized by contact with a surrounding metal or metallic foreign material, an erroneous signal may be generated regardless of the level.

In order to improve this, a mutual induction current type level meter using the conductivity of a liquid has been developed. Mutual induction current-type level gauge is not only capable of continuous level measurement, but also has high signal reliability as it is non-contact with liquid, and is easy to maintain and repair. have.

However, since the mutual induction current type level gauge can generate different level signals even though the liquid level is the same when the temperature of the liquid changes, a complex temperature compensation circuit must be adopted to improve this, and experiments for temperature compensation must be accompanied. In some cases, complex laboratory facilities are also required.

As a related prior art, US Patent No. 4,164,146 discloses "Apparatus and method for monitoring the presence of a conductive media". However, this patent provides an induced voltage signal equal to the magnitude of the induced voltage V generated in the secondary coil multiplied by cos (φ-θ) by separately using a phase shifting circuit for temperature compensation.

In addition, Korean Patent No. 1,892,732 discloses "a broadband molten metal level measuring device and thermal system using a multi-contact temperature sensor". However, this patent does not disclose a temperature compensation technique, although it presents a mutual induction current type level gauge.

In addition, US Patent No. 3,948,100 discloses "Probe for measuring the level of a liquid". However, in this patent, temperature compensation is performed by separately using an additional circuit for installing an external resistor in the secondary coil.

US Patent 4,164,146 Korean Patent 1,892,732 US Patent 3,948,100

One embodiment is to perform temperature compensation of a mutual induction current type level gauge quickly, accurately and conveniently without a conventional complicated temperature compensation circuit.

One embodiment is to omit a conventional experimental facility for complex temperature compensation.

In addition to the above tasks, the embodiment according to the present invention may be used to achieve other tasks not specifically mentioned.

A method for compensating a temperature of a mutual induced current type level gauge according to an embodiment includes measuring a first induced electromotive force by a mutual induced current type level gauge to which power having a first current and a first frequency is supplied under a first temperature , measuring a second induced electromotive force by a mutually induced current type level meter to which power having a first current and a first frequency is supplied under a second temperature, the first induced electromotive force and the second induced electromotive force while changing the first frequency Measuring the electromotive force, deriving a first frequency when the difference between the first induced electromotive force and the second induced electromotive force is minimized as an optimal frequency, and a mutual induced current type level meter with a power source having the first current and the optimal frequency It includes the step of supplying with

Mutual induction current type level gauge according to an embodiment includes a coil bobbin, a primary coil and a secondary coil wound around the coil bobbin, a power supply that provides a first current and a first frequency to the primary coil, and a second coil It includes a signal processing unit for measuring the first induced electromotive force and the second induced electromotive force.

In one embodiment, temperature compensation can be performed quickly, accurately and conveniently without a conventional complicated temperature compensation circuit, and a conventional experimental facility for complicated temperature compensation can be omitted.

1 is a graph showing the difference in induced electromotive force at each temperature level of a conventional mutual induced current type level gauge.
2 is a perspective view illustrating a mutual induction current type level gauge according to an embodiment.
3 is a cross-sectional view illustrating a mutual induction current type level gauge according to an embodiment.
4 is a diagram illustrating a power supply circuit according to an embodiment.
5 is a diagram illustrating a signal processing circuit according to an exemplary embodiment.
6 is a graph illustrating a change in absolute error of an induced electromotive force according to a frequency change in a mutual induced current type level gauge according to an embodiment.
7 is a graph illustrating a change in induced electromotive force according to a change in liquid level for each temperature at a specific frequency in a mutual induced current type level gauge according to an embodiment.
8 is an optimal view of a mutual induction current type level gauge according to an embodiment. It is a graph showing the change of the induced electromotive force according to the change of the liquid level according to the temperature and the frequency.

With reference to the accompanying drawings, the embodiments of the present invention will be described in detail so that those of ordinary skill in the art to which the present invention pertains can easily implement them. The present invention may be embodied in many different forms and is not limited to the embodiments described herein. In order to clearly explain the present invention in the drawings, parts irrelevant to the description are omitted, and the same reference numerals are used for the same or similar components throughout the specification. In addition, in the case of a well-known known technology, a detailed description thereof will be omitted.

Throughout the specification, when a part "includes" a certain component, it means that other components may be further included, rather than excluding other components, unless otherwise stated.

Then, a method for compensating a temperature through frequency control according to an embodiment and a mutual induction current type level gauge using the same will be described.

An embodiment is a mutual induced current type level gauge to which a temperature compensation method of a mutual induced current type level gauge is proposed and applied. According to one embodiment, by minimizing the distortion of the induced electromotive force in the secondary coil according to the temperature change by applying only the constant current (AC) supplied to the primary coil and the optimum frequency of the supply power derived through a simple experiment, the operating temperature Consistent level information can be obtained in a wide range of facilities. Accordingly, according to an embodiment, the use of a conventional complex temperature compensation circuit and an experimental facility for temperature compensation may be excluded.

However, according to the conventional mutual induced current type level gauge, in order to compensate for the generation of different induced electromotive force depending on the temperature at the same liquid level, a conventional complex temperature compensation circuit and an experimental facility for temperature compensation must be used.

1 is a graph showing the difference in induced electromotive force at each temperature level of a conventional mutual induced current type level gauge. Referring to FIG. 1 , it is shown that the conventional mutual induced current type level gauge indicates different induced electromotive force according to temperature at each liquid level. Referring to FIG. 1 , it can be seen that the induced electromotive force of the secondary coil linearly decreases as the liquid level increases at each temperature.

In the mutually induced current type level gauge according to an embodiment, an induced electromotive force is generated in the secondary coil according to Faraday's law as the magnetic flux generated when AC is supplied to the primary coil is linked to the secondary coil, and the magnitude is given by the formula ( 1) is followed.

[Equation 1]

where E ₂ is the induced electromotive force (V) generated in the secondary coil, N ₂ is the number of turns in the secondary coil, ΔΦm is the change in the magnetic flux of the primary coil (Wb), and Δt is the change in the magnetic flux of the primary coil ( sec).

[Equation 2]

And Equation (2) is the magnetic flux (Φm, Wb) generated in the coil wound around the core, the number of turns (N), the current (I, A), the permeability of the core (μ, H/m), and the cross-sectional area of the core ( A, m ² ), and the length of the core (l, m) are correlated. As long as the physical parameters (N, A, l) of the level gauge do not change, the magnitude of the magnetic flux is proportional to the change in the magnitude of the supply current. Accordingly, when the current supplied to the primary coil increases or decreases, the magnetic flux increases or decreases, and the electromotive force induced to the secondary coil also increases or decreases. Therefore, when a constant current of a constant frequency is always supplied to the primary coil at a certain liquid level, the electromotive force induced in the secondary coil always indicates a constant value.

In addition, the magnetic flux generated in the primary coil is linked not only to the secondary coil but also to the liquid around the mutual induction current type level gauge. An eddy current is generated in a direction that disturbs the Therefore, when the liquid level around the mutual induced current level gauge increases, the magnitude of the eddy current generated in the liquid increases relatively, and the magnitude of the induced electromotive force of the secondary coil decreases. As the magnitude decreases, the magnitude of the induced electromotive force of the secondary coil increases. In this way, the mutual induction current type level gauge is to measure the change in the induced electromotive force generated in the secondary coil by the eddy current that increases or decreases according to the change in the liquid level around the level gauge to specify the liquid level.

However, the eddy current increases in proportion to the strength of the magnetic field linkage, the magnitude of electrical conductivity, and the rate of change of magnetic flux. Accordingly, when the temperature of the liquid around the level gauge increases, the resistance of the secondary coil and the electrical resistance of the surrounding liquid increase. As the electrical conductivity decreases, the magnitude of the eddy current decreases, but the induced electromotive force generated in the secondary coil is will increase Accordingly, the user receives the level information distorted according to the temperature change even though the level is the same. Therefore, the mutual induction current type level gauge needs a series of temperature corrections to correct the distortion of the level readings according to the temperature.

Accordingly, according to the conventional mutual induction current type level gauge, a complex temperature compensation circuit is adopted for the primary or secondary coil, and field experiments for temperature compensation are also required.

The mutual induction current type level gauge proposed in one embodiment can minimize distortion of liquid level information due to temperature change through a simple experimental procedure, and is largely fixed to the sensor unit around which the primary/secondary coil is wound and the primary coil. It supplies a constant current of frequency and consists of a power supply unit and a signal processing unit for signal processing.

Referring to FIGS. 2 and 3 , in the mutual induction current type level gauge 1 , the sensor unit is wound on a cross coil bobbin (core) 10 with the same number of windings at a predetermined pitch (equivalent interval) crossing the primary and secondary windings. Coil 20, a protective tube 30 for protecting the primary coil 21 and the secondary coil 22, a guide tube 40 for preventing direct contact between the liquid 8 and the protective tube 30 on the outside thereof, When the instrument is installed in a liquid container, it is composed of a flange 50 for installing a level gauge to support the instrument, a cable connection unit 60 for connecting the power supply line and the signal acquisition line of the power supply unit and the sensor unit, etc., and the primary / secondary coil Reference numeral 20 may be made of a Mineral Insulated (MI) cable 29 using a nickel wire. The pitch of the primary coil 21 and the secondary coil 22 may be different from each other, and the number of windings may be different from each other.

The power supply unit 100 includes a variable current (AC) supply circuit capable of providing an arbitrary constant current to the primary coil 21 and a variable frequency supply circuit capable of providing an arbitrary constant frequency to the primary coil 21 . may include

The power supply unit 100 may include a frequency generation circuit 110 , a constant current control circuit 120 , a display input/output device 130 , and a terminal terminal 140 .

The frequency generating circuit 110 may be configured in an analog circuit method capable of controlling the frequency F from about 1 kHz to about 10 kHz. For example, the frequency generating circuit 110 may be a variable frequency supply circuit.

The constant current control circuit 120 may be composed of an amplifier and a Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET), and according to an input, a desired constant current level (mA) (I) can be output. can do. For example, the constant current control circuit may be a variable current supply circuit.

The display input/output device 130 may display user input and data D such as frequency and current.

The terminal terminal 140 may transmit a signal M to the data acquisition system.

The current supplied to the primary coil 21 is controlled in the range of 1 kHz to 10 kHz by the frequency generation circuit 110 according to a user input through the display input/output device 130 , and by feedback control of the constant current control circuit 120 . It is controlled to a constant current output level (mA) desired by the user. The frequency and current level (mA) of the constant current controlled by the frequency generator circuit 110 and the constant current control circuit 120 are displayed on the display input/output device 130 . This frequency and current information is transmitted to the data acquisition system through the terminal terminal 140 as a signal in the form of about 4mA to 20mA.

The signal processing unit 200 includes a signal processing circuit for collecting the induced electromotive force of the secondary coil 22 . The signal processing unit 200 includes a processor 230 that measures and calculates an induced current, an induced electromotive force, and the like.

The induced electromotive force of the secondary coil 22 passes through the noise removal filter 210 to remove 60Hz noise caused by the power, and the signal level is amplified by the amplifier 220 to facilitate signal processing. The amplified signal is converted into a digital signal by performing signal processing based on a moving average by a program built into the processor 230 . The converted signal is converted into an analog signal 250 in the form of a current of about 4 mA to about 20 mA by a DAC (Digital to Analog Converter) 240 and transmitted (O) to the data acquisition system.

In addition, the signal processing unit 200 includes a port to which a data storage device 260 can be connected to store data independently of the data collection system, a debugging port 280 for debugging an internal signal processing program, and a processor 230 . It may optionally include a reset switch 270 for rebooting when the operation is stopped, and a lamp 290 for checking the operating state of the processor 230 .

The mutual induction current type level gauge 1 may include a touch-type liquid crystal panel capable of checking and controlling input/output power information of the primary/secondary coil 20 .

According to an embodiment, a method for compensating the temperature of a mutual induced current type level gauge through frequency control and a method for deriving a simple optimal frequency therefor are provided.

The change in the induced electromotive force of the secondary coil according to the temperature change is a phenomenon that occurs because the electrical conductivity of the secondary coil and the liquid around the level gauge changes together as the resistance changes according to the temperature change of the secondary coil and the liquid around the level gauge.

When the magnetic flux generated in the primary coil is linked to the secondary coil, an eddy current is generated in the secondary coil and the liquid itself around the level gauge to resist the change in the primary coil's magnetic flux and prevent the magnetic flux change. Since the strength of the eddy current is proportional to the strength of the magnetic field linked to the secondary coil, the electrical conductivity of the secondary coil or liquid, and the rate of change of the flux linkage, as the temperature increases, the induced electromotive force generated in the secondary coil decreases the electrical conductivity. It increases in proportion to the decrease in the intensity of the eddy current. Accordingly, since inconsistent and distorted liquid level information can be provided to the user when the temperature changes at the same liquid level, temperature compensation is required.

The magnitude of the induced electromotive force generated in the secondary coil can also be expressed by Equation (3).

[Equation 3]

where E is the induced electromotive force generated in the secondary coil, X is the impedance, I is the induced current of the secondary coil, R is the winding resistance of the secondary coil, ω is the angular frequency, and L is the inductance of the secondary coil .

Let L be the lowest operating temperature and H the highest operating temperature of the container in which the mutual induction current type level gauge is used, and at each temperature, Expression (3) is expressed at each temperature as follows.

[Equation 4]

[Equation 5]

Since there should be no difference in induced electromotive force according to temperature change at the same liquid level (ΔE = EH - EL = 0), the following equation (6) can be obtained from equations (4) and (5).

[Equation 6]

In Equation (6), since the supply frequency supplies the same frequency, ω has the same angular frequency.

[Equation 7]

[Equation 8]

After all, in Equation (8), there is a specific frequency that eliminates the difference in induced electromotive force due to temperature change. It means that it can be corrected or minimized. In this specification, this specific frequency is referred to as an optimal frequency.

However, in Equation (8), except for the winding resistance of the secondary coil that can be measured at each temperature, the magnitudes of induced current and inductance are virtually unknown depending on the supply frequency, so it is easy to derive the optimum frequency through Equation (8). In the end, a series of experiments are needed to derive the optimal frequency.

In one embodiment, an experiment is performed to confirm that there is an optimal frequency for minimizing distortion of level information according to the temperature of the mutual induction current type level gauge.

The experimental conditions were that at the lowest temperature of 200 °C and the highest temperature of 550 °C, 100 mA AC constant current was supplied at a frequency of 1.5 kHz to 4.5 kHz in 0.1 kHz increments, and Measure the induced electromotive force.

A mutual induction current type level gauge is installed in the chamber containing liquid metal (sodium), and a contact level gauge is installed as a reference level gauge that can check the highest and lowest level.

6 shows the absolute error (ΔE= |E ₅₅₀ - E ₂₀₀ |) of the induced electromotive force that occurs according to the temperature difference at the highest/lowest level of the mutual induction current type level gauge measured while changing the frequency. It is confirmed that the absolute error of the induced electromotive force generated by the temperature difference at the highest/lowest level of the mutual induction current type level gauge decreases to the optimum frequency (2.8kHz) when the frequency is increased, and increases again when the optimum frequency is exceeded.

However, in the 3.0 kHz to 3.2 kHz region, it shows an unstable phenomenon out of the increasing pattern.

7 and 8 show the induced electromotive force measured when the frequency 4.5 kHz is supplied and the induced electromotive force measured when the optimum frequency (2.8 kHz) is supplied for each liquid level at the lowest/highest temperature. Through this, it is confirmed that the induced electromotive force distortion caused by temperature change can be removed only by frequency control without a special temperature compensation circuit, and the error can be further reduced by subdividing the supply frequency.

According to an embodiment, when it is seen that the optimum frequency is not affected by the liquid level as a result of the experiment, it is possible to derive the optimum frequency through a simple experiment in the atmosphere without a special experimental device, and the experimental procedure is as follows.

Install a heater and thermocouple for temperature measurement on the outer surface of the guide tube of the mutual induction current type level gauge.

Install insulation covering the heater and guide tube.

After raising the temperature to the lowest operating temperature, a constant current is supplied to the primary coil while modulating the frequency, and the induced electromotive force generated in the secondary coil is measured.

After raising the temperature to the maximum operating temperature, a constant current is supplied while modulating the frequency to the primary coil, and the induced electromotive force generated in the secondary coil is measured.

Find the optimal frequency at which the error of the measured induced electromotive force at the highest/lowest temperature is minimized.

Since the proposed optimal frequency derivation test method is the same as the liquid-free environment in the container where the mutual induction current type level gauge is installed, additional experiments to derive the optimal frequency by installing it in the container are unnecessary.

According to an embodiment, a variable current (AC)/frequency power supply capable of supplying an arbitrary constant current/constant frequency to the primary coil is provided.

According to Equation (2), a circuit is provided to supply constant current AC in order to ensure that the magnetic flux is always uniformly linked to the secondary coil. made it possible Since the resistance of the primary coil increases when the temperature changes, it includes an electric circuit in which the supply voltage is changed correspondingly to supply a constant current AC to the primary coil.

In order to make the induced electromotive force generated in the secondary coil constant according to Equation (1), the frequency of the supply power must also be constant, so a constant frequency (Hz) supply circuit is provided, and the size of the frequency is also within the range (1 kHz to 10 kHz). ) in 10 Hz increments, and is an electric circuit for frequency modulation during temperature compensation.

According to one embodiment, there is provided a control screen that employs a touch-type display for instructing and controlling input/output information and improving user convenience.

The mutual induction current type level gauge according to an embodiment is provided with a power supply for supplying current and frequency to the primary coil, which indicates the current state of the mutual induction current type level gauge (voltage, current, frequency, etc.) ) may include a display indicating the.

In addition, since a touch-type display is adopted, a function button for input of a control variable is not required, and the desired current and frequency to be supplied can be intuitively and easily changed or selected, so that the user's convenience can be improved.

The touch panel screen consists of a total of four such as the current input/output power status, supply power setting, external transmission signal setting for the primary coil, and external transmission signal setting for the secondary coil, and the configuration and functions of each screen are as follows.

In the current input/output power status screen (Status), the current supply current/voltage/frequency supplied to the primary coil and the induced current/electromotive force generated in the secondary coil are displayed. In addition, when the conditions specified on the supply power setting screen are satisfied, the green light turns on to indicate to the user that a constant current of a constant frequency is being supplied by reaching a steady state.

In the power supply setting screen (Coil setting), the user can specify the current value and frequency to be supplied to the primary coil, and the supply current is -1 mA, -10 mA, -50mA, -100 mA, 1mA, 10 Touch the button set in units of mA, 50mA, 100 mA to set the desired value, and the supply frequency is in units of -10 Hz, -50 Hz, -100 Hz, -1,000 Hz, 10 Hz, 50 Hz, 100 Hz, 1,000 Hz. Touch the button set to to finely set the desired value.

The external transmission signal setting for the primary coil (Output #1 Setting) is the lowest value for sending the signal to an external data processing device by converting the current measured value of the supply current/frequency/voltage of the primary coil into a 4 mA ~ 20 mA signal. (4 mA corresponding value) and maximum value (20 mA corresponding value) can be set through the touch panel screen.

The external transmission signal setting for the secondary coil (Output #2 Setting) converts the current measured value of the induced electromotive force of the secondary coil into a 4 mA ∼ 20 mA signal and transmits the signal to an external data processing device. value) and maximum value (20 mA corresponding value), and set the level in %.

Since one embodiment proposes a new method of correcting the level signal distortion of the mutual induced current type level gauge caused by temperature change at the same liquid level by simply controlling the frequency supplied to the primary coil, the mutual induced current type level gauge The problem of temperature compensation circuit design, which is a technical issue of the company, disappears. And because temperature correction can be performed using the optimum frequency derived only through a simple experimental procedure, there is no need for complicated or expensive temperature correction test facilities and long-term experiments.

One embodiment includes a touch-type liquid crystal panel indicating the input/output status of the mutual induction current type level gauge, so there is no need for a function button for input of control variables, etc., and the desired current and frequency to be supplied can be changed intuitively and easily. Alternatively, it can be selected, so that the user's convenience can be improved.

According to an embodiment, it is possible to obtain consistent level information in a facility with a wide operating temperature range, and stable facility operation is possible through continuous level information acquisition/monitoring. In particular, it is possible to obtain the import substitution effect by self-manufacturing the expensive mutual induction current type level gauge, which had been dependent on imports, at 50% of the import price.

Although the preferred embodiment of the present invention has been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention as defined in the following claims are also provided. is within the scope of the

1: Mutual induction current level gauge 8: Liquid
10: coil bobbin 20: primary and secondary coil
30: Sheriff 40: Information Officer
50: flange 60: cable connection
100: power supply unit 200: signal processing unit

Claims (19)

Measuring a first induced electromotive force by a mutual induced current type level meter to which power having a first current and a first frequency is supplied under a first temperature;
Measuring a second induced electromotive force by the mutual induced current type level meter to which power having the first current and the first frequency is supplied under a second temperature;
measuring the first induced electromotive force and the second induced electromotive force while changing the first frequency;
deriving the first frequency as an optimal frequency when the difference between the first induced electromotive force and the second induced electromotive force is minimized; and
supplying the power having the first current and the optimum frequency to the mutual induction current type level gauge
A method for temperature compensation of a mutual induction current type level gauge comprising a.
In claim 1,
The mutual induced current type level gauge includes a primary coil and a secondary coil,
Measuring the first induced electromotive force in the secondary coil while supplying the first current to the primary coil while changing the first frequency under the first temperature, and
Under the second temperature, while supplying the first current while changing the first frequency to the primary coil, the temperature compensation method of a mutual induced current type level gauge for measuring the second induced electromotive force in the secondary coil .
In claim 1,
A temperature compensation method of a mutual induced current type level gauge for heating the mutual induced current type level gauge in the atmosphere with a heater to measure the first induced electromotive force and the second induced electromotive force.
In claim 1,
A method of compensating for a temperature of a mutual induced current type level gauge for measuring the first induced electromotive force and the second induced electromotive force by heating the liquid after placing the mutually induced current type level gauge in a liquid.
In claim 1,
The first temperature is the minimum operating temperature of the facility in which the mutual induction current type level gauge is used, and the second temperature is the maximum operating temperature of the facility in which the mutual induction current type level gauge is used. How to compensate the temperature of the level gauge.
In claim 5,
The mutual induced current type level gauge includes a primary coil and a secondary coil,
The optimal frequency satisfies the following Equation 1,
[Equation 1]

Here, f is the first frequency, I is the induced current of the secondary coil, R is the winding resistance of the secondary coil, L is the inductance of the secondary coil, the subscript L is the minimum operating temperature, The subscript H is the temperature compensation method of the mutual induction current type level gauge that is the highest operating temperature.
In claim 1,
A method of compensating for a temperature of a mutual induction current type level gauge by compensating the temperature of the mutual induction current type level gauge by frequency modulation without a temperature compensation circuit.
coil bobbin,
a primary coil and a secondary coil wound around the coil bobbin;
a power supply for providing a first current and a first frequency to the primary coil;
A signal processing unit for measuring the first induced electromotive force and the second induced electromotive force in the secondary coil;
Mutual induction current type level gauge comprising a.
In claim 8,
The first induced electromotive force is measured under a first temperature, and the second induced electromotive force is a mutually induced current type level gauge measured under a second temperature.
In claim 9,
The first frequency when the difference between the first induced electromotive force and the second induced electromotive force is minimized is an optimal frequency.
In claim 8,
The power supply unit is a mutual induction current type level gauge including a variable current supply circuit for providing an arbitrary constant current.
In claim 11,
The power supply unit is a mutual induction current type level gauge including a variable frequency supply circuit for providing an arbitrary constant frequency.
In claim 12,
The signal processing unit mutually induced current type level gauge comprising a processor for measuring the first induced electromotive force and the second induced electromotive force.
In claim 8,
Mutual induced current type level gauge further comprising a display for displaying the first current, the first frequency, the first induced electromotive force, and the second induced electromotive force.
In claim 8,
The primary coil is wound with a first number of turns at a first interval, and the secondary coil is wound with a second number of turns at a second interval.
In claim 8,
Mutual induced current type level gauge further comprising a protective tube surrounding the primary coil and the secondary coil.
17. In claim 16,
Mutual induced current type level gauge further comprising a guide tube surrounding the protective tube.
In claim 17,
Mutual induction current type level gauge further comprising a cable connection unit connected to the power supply unit and the signal processing unit.
In claim 18,
A mutual induced current type level gauge further comprising a flange for supporting the mutually induced current type level gauge.

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