Method of measuring level of dielectric matter

FIELD: electric measurement engineering.

SUBSTANCE: method can be used for measurement of electrical parameters of two-terminal networks used as detectors of physical processes (temperature, pressure, level of liquid and loose maters et cetera) at industrial installations, transportation vehicles and in systems for measuring level of setting-up of rocket-space equipment. Sinusoidal voltage is formed in capacitive level gauge and complex current is measured which passes through dry capacitive level gauge as well as through filled-in capacitive level gauge. Equivalent circuit of capacitive level gauge is specified which circuit consists of electric capacitance and active resistance. Sinusoidal voltage is formed in capacitive detector at two frequencies. After it complex current is measured through dry level detector and through reference detector for any of those frequencies. Results of measurement are registered, electric capacitance of capacitive level gauge is measured and registered and increment in electric capacitance of capacitive level gauge is measured and registered when submerging gauge into dielectric matter completely. Subsequent measurement and registration of complex current is carried out through capacitive level gauge filled with dielectric matter and through reference gauge for any of mentioned frequencies. For any periodical measurement the electric capacitance of capacitive level gauge is measured and registered. Relative filling of capacitive level gauge with dielectric matter is measured as difference of values of electric capacitance of dry capacitive level gauge and electric capacitance of filled-up capacitive level gauge related to increment in electric capacitance of capacitive level gauge submerged into liquid totally.

EFFECT: improved precision of measurement; improved adaptability to manufacture.

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The invention relates to electrical engineering, and specifically to the measurement of electrical parameters of two-terminal used as sensors of physical processes (temperature, pressure, liquid level and granular media and other industrial objects, vehicles, as well as in systems for measuring the level of filling of rocket and space technology.

The known method, is selected as the analogue of the Method of measuring the three parameters of two-terminal frequency-independent bridges AC", described in the patent No. 2144196, CL G 01 R 17/10, 27/02, is to balance the bridge at the first frequency using the sign information of the projection of the signal offset at the second frequency, the size of the regulated impacts on changing one of the three adjustable parameters of the shoulder in comparison determining module signal offset at the second frequency, and the direction to choose the sign of the increment of this module during the test measurement of the third parameter of the shoulder comparison to the set of its values.

The disadvantages of analogue is the low accuracy of determination of parameters of the remote for a distance of dvukhpolosnykh (e.g., capacitive level switch, low performance in some cases its use, for example, in the alarm device passing in owner dielectric liquid of given heights of the tank.

However, the specifics of operation of rocket and space technology for the measurement of parameters of two-terminal address their demands, contributing to the search for new technical solutions in the field of measurements. We denote the most characteristic of them:

- the distance of 500 meters of the measurement object from the measurement tools. An example is the process of determining the parameters of the impedance of the capacitive sensor level control refills, built in tank missiles, which is a test case or at the launch site during its refueling propellant;

- high accuracy of measurement remote dvukhpolosnykh, which is a capacitive level sensor. It is obvious that the accuracy of the measurement is directly related to the amount of warranty reserves of fuel on Board the rocket. The higher the accuracy, the less warranty reserves of fuel, the higher the efficiency of a rocket that can take greater payload;

the requirement of high-tech training missiles, excluding pre-setting of measurement instruments by the human operator, as well as allowing one measurement tools with multiple capacitive level sensors missiles one by one;

- high performance parameter definitions dupoly is nick, allows you to extend the functionality of the measuring method and use it in a similar way in the transmitter side terminal of the automatic control system, which is the control system fuel rockets.

The closest in technical essence and the achieved positive effect to the claimed method is a method of measuring the level of a dielectric substance, described in the book "Capacitive samarapungavan level" authors Cbecindia, Fbhrendes, Aievoli, Moscow: publishing house "Energy", 1966, p.28.

The method of determining the level of the dielectric substance is the formation of a sinusoidal voltage on the capacitive level sensor measurement of complex current through dry capacitive level sensor and the measurement of complex current through the capacitive fill level sensor.

In the presented prototype of a method of measuring the level of the dielectric fluid is based on the addition of current sensors, using tightly coupled inductive arms of the bridge on the sum of the measuring transformer. The rate at which the current enters the total amount is determined by the number of turns of the shoulder, and the sign of the coefficient - direction enable winding of the shoulder. The equilibrium condition of the measuring circuit is equality n is Liu sum of all the currents, flowing through the sensors. The ratio of the number of turns of tightly coupled inductive shoulders determines the relative fill level of the capacitive level sensor of the dielectric substance.

When using the prototype to determine the level of the dielectric substance by using a capacitive level sensor, remote on a sufficiently large distance (500 metres) from the measurement tools, the result is a high degree of accuracy. Low adaptability and precision measurements of the prototype due to the following:

- prototype method does not have the full invariance with respect to the long lines of communication between the measuring tool and the capacitive level sensor, i.e. does not exclude the influence of long lines of communication on the result of the determination level;

the prototype measures the complex currents through capacitive level sensors, which do not take into account the values of the dielectric substance (dielectric permittivity of the substance and of the gas environment on the matter, including temperature, changing the geometric dimensions of the capacitive level sensors due to exposure to cryogenic temperatures). Accordingly, before the process of filling required preliminary manual setting measurement tools to set the parameters of the liquid and the sensor when determining the level of filling for each date the ICA individually;

the relatively poor performance of the method of measurement (before 10 sec) on the measurement. This is due to design of the bridge measurement tools, representing a tracking system that is balanced by active and reactive components of the impedance of the capacitive sensor. As well as the process of continuous fueling of the rocket, the poor performance of process level measurement introduces additional error.

Thus, the disadvantages of the prototype are:

- low accuracy level at a sufficiently remote from the measuring capacitive level sensor;

- low performance way of measuring associated with the process of balancing the bridge;

- low technological level definitions related preliminary manual setting measurement tools on the settings refills. The presence of the human factor in technology determine the level introduces additional error in the precision of its definition.

The objective of the method of determining the level of the dielectric substance is to improve the accuracy of its determination, which consists in the elimination of the influence of long lines of communication on the result of the determination, as well as improving the manufacturability and performance level definitions, that is, a full automation% of the SSA determination level, the exclusion of the human factor and manual procedure setting measurement tools.

The solution of this problem is achieved in that in the method of determining the level of a dielectric substance, which consists in forming a sinusoidal voltage on the capacitive level sensor measurement of complex current through dry capacitive level sensor and the measurement of complex current through the capacitive fill level sensor, unlike the prototype set the equivalent circuit of the capacitive level sensor consisting of electrical capacitance and resistance, the formation of a sinusoidal voltage on the capacitive level sensor is produced at two frequencies, then produce consistently measurement of complex current through the dry level sensor and standard on each of the two frequencies, and the results of the measurements record, define and record the electrical capacity of the dry level sensor, calculate and record the increment of the electrical capacitance of the capacitive level sensor with immersion in a dielectric substance, occasionally produce consistent measurement and fixation of the complex current through the fill dielectric substance capacitive level sensor and standard on each of the two specified frequencies for each periodic measurements define and record e is actrices capacitance of the capacitive level sensor then determine the relative filling of the dielectric substance capacitive level sensor as the difference of values of electrical capacitance capacitive fill level sensor and an electric capacity of dry capacitive level sensor is related to the increment of the electric capacity is fully immersed in a dielectric substance capacitive level sensor.

The implementation of such characteristics as the calculation of the parameters of dry and fill dielectric substance capacitive level sensor, and calculating the increment of capacitance level sensor when it is full immersion in a dielectric substance is provided in the same conditions in the presence of a long line. This gives an opportunity to consider the effects of long lines at the two calculations with automatic adjustment of measuring instruments. As a collection of characteristics, providing a determination of the relative filling of the dielectric substance capacitive level sensor, as the difference of values of electrical capacitance capacitive fill level sensor and an electric capacity of dry capacitive level sensor is related to the increment of the electric capacity is fully immersed in a dielectric substance capacitive level sensor, eliminates the effects of long lines on the result of determination otnositelnoj the fill level sensor. Thus, the claimed method acquires a new quality of invariance with respect to the measurement conditions with a long line or without it, and it is the quality that allows high accuracy to determine the level of the dielectric substance, as in a remote location capacitive level sensor, and in proximity of the sensor.

The set of features that after measurement of the complex currents through dry capacitive level sensor and standard on each of the two frequencies to determine the parameters C and R, as well as to determine the increment of the electrical capacitance of the sensor when it is full immersion in a dielectric substance (including thermal and physical parameters of the dielectric substance), automates the configuration process measurement and achievement improve manufacturability and accuracy of determining the level of dielectric substances, eliminating the human error factor from the configuration procedures of measuring.

For the practical implementation of the method the authors used the technology computer-aided design of electronic circuits, built on the use of programmable logic integrated circuits (FPGA) design by Xilinx. This uses software Foundation Series. This design package includes the complex of tools, enable the development of a FPGA by Xilinx, starting from the description of the internal contents of your device to download the FPGA configuration and debug directly on the PCB. Software Foundation Series allows you to implement all necessary functions, including the implementation of numerical methods for computing the values of physical quantities.

Figure 1 shows the equivalent circuit of the capacitive level sensor.

Figure 2 presents a vector diagram of the circuit of the capacitive level sensor.

As an example of the method let us consider the procedure of determining the level of charging of the dielectric substance in the tank products of rocket and space technology. As the dielectric substance can be considered, for example, kerosene.

Capacitive level sensor corresponds to the equivalent circuit shown in figure 1, where: Cphave a working electrical capacitance sensor, which carries useful information about the filling level of the tank; R - resistance leakage current through the dielectric, which depends on the grade of kerosene and introduces error in the measurement of the filling level, if not to take into account. Figure 2 presents a vector diagram of the capacitive level sensor for which the fair the following relations:

is due to the specifics of operation of rocket and space technology capacitive level sensor is located at a distance of 500 meters from the measurement tools.

According to a given circuit, the capacitive level sensor have the following expression to determine its parameters:

To determine the parameters necessary to perform the measurement of current through the capacitive level sensor and the reference. Since capacitive level sensor is a two-tier dvukhpolosnykh, in accordance with the characteristic formula of the invention the measurement of complex voltage needs to be performed at two frequencies ω1and ω2.

For this purpose, according to the sign of the claims produce the formation of a sinusoidal voltage on a capacitive level sensor at two frequencies ω1and ω2. Then measure the complex values of the currents through dry capacitive level sensor and the standard for each of the specified frequencies. The values of currents through the pattern match expressions

According to the vector diagram of figure 2, the modules of the measured complex currents through capacitive level sensor can be written by the following expression:

It should be noted that the above steps produce settings for measuring perexadiashi tank products CT, consisting in the measurement of complex currents through dry capacitive level sensor connected to measurement through the communication line. The measured results of the complex currents are recorded. From the point of view of practical implementation of the procedure of fixing can be made in the form of saving the measurement results in the storage device, based on technology Xillinx.

Then determine the state of the capacitive level sensor in accordance with the dependencies (3) and (4). The results of determination of parameters of dry capacitive sensor Withpand R are fixed and represent the source data needed to perform the further sequence of the method. The setup procedure of measuring completes the action according to the formula of the invention for determining the increment of the electrical capacitance of the capacitive level sensor is completely submerged in this case in kerosene. The dependence on which is calculated increment of electric capacity, is

CDRY- the capacitance of the capacitive level sensor, which is determined taking into account the influence of the communication line based on (3);

εW- permittivity kerosene;

εG- the dielectric constant of the gas cushion located in the tank R Is T over kerosene.

The result of the determination of the increment of capacity made by the dependence (9)is fixed.

The set of features that provides the definition of the parameters of dry capacitive level sensor and the incremental electric capacity when it is full immersion in kerosene taking effect on the determination results of the communication line, allows the configuration process measurement tools to automate. Thus the combination of the above features allows you to increase the adaptability and precision of measurement by eliminating the instrumental error of the human factor.

When making the filling tank products CT occasionally produce consistent measurement of complex current through the capacitive fill level sensor and standard on each of the two specified frequencies. Moreover, the result of measurement of the complex currents through the fill capacitive sensor communication line has a similar effect as in the measurement of the complex current through dry capacitive sensor. The measurement results are recorded. Then after each measurement of the complex current through fill capacitive sensor and the standard is the definition of its parameters in accordance with expressions (3) and (4). The results of determination of parameters of the sensor are fixed. The electric capacity of the capacitive fill level sensor is in the guise of a variable, therefore, it can be called With currentTECH.

Then carry out a definition (level) relative capacitive filling level sensor kerosene. According to the features of patent claims is as follows. First, determine the difference of values of electrical capacitance is filled capacitive sensor (let's call it the current electrical capacity WithTECH) and electrical capacitance dry capacitive sensor, calculated when the setup of measurement. This difference can be identified by the expression

where CTECK -the capacitance value of the filling level sensor, calculated in accordance with expression (3). The analytical expression of the electric capacitance filled with kerosene capacitive level sensor can be written in the following form:

where h is the current height of immersion capacitive level sensor in kerosene;

H - total height of immersion of the sensor in kerosene.

Next, the ratio of the difference between the electric capacitances according to the expression (10) and incremental electric capacity fully immersed capacitive level sensor in the fuel, which can be written in the following form

The set of features that characterize the determination of the relative is more capacitive filling level sensor kerosene as the difference of values of electrical capacitance capacitive fill level sensor and an electric capacity of dry capacitive level sensor attributed to the increment of electric capacity fully immersed in kerosene capacitive level sensor, provides the exception of the impact of the communication line to the result. From the analytical dependence (12) it should be obvious, WithDRYand CTECHwas determined by accounting for the effects of line, FromCRit was also determined taking into account the influence of the communication line. Therefore, according to expression (12) effect of line analytically excluded.

Thus, the above set of features characterizes the way as invariant with respect to the communications line.

The process of determining the level periodically lasts as long as the tank product CT will not be filled to the desired level.

The claimed method of determining the level of the dielectric substance may be implemented using devices, functional blocks which are executed on the chip 2S200PQ208 by Xilinx. Numerical solutions presented above expressions can be implemented using the software package Foundation Series.

The claimed method the authors tested on models of the product. Currently, the authors create a system for measuring the level of filling of the rocket unit, which is designed to modernize the ground equipment one of the starting launchers polygon "Baikonur".

ISOE is ishema literature

1. Agamalov YU, Bobylev D.A., Kneller has WORKED Meter analyzer parameters complex resistance-based personal computers. Measuring equipment. 1996, No. 6, p.56-60.

2. Cbecindia, Fbhrendes, Ahinovi. Capacitive samarapungavan level. M: publishing house "Energy", 1966, C. - 135.

3. Ahinovi. "Automatic trim extreme digital bridges AC", Kyiv:, Naukova Dumka, 1983, p.9-10.

4. RF patent №2025666, CL G 01 F 23/26, "Multi-point level switch (and its variants)".

5. Patent No. 2144196, CL G 01 R 17/10, 27/02, "a method of measuring the three parameters of two-terminal frequency-independent bridges AC".

The method of determining the level of a dielectric substance, which consists in forming a sinusoidal voltage on the capacitive level sensor measurement of complex current through dry capacitive level sensor and the measurement of complex current through the capacitive fill level sensor, characterized in that specify the equivalent circuit of the capacitive level sensor consisting of electrical capacitance and resistance, the formation of a sinusoidal voltage on the capacitive level sensor is produced at two frequencies, then produce consistently measurement of complex current through the dry level sensor and standard on each of two hours is from, moreover, the results of the measurements record, define and record the electrical capacity of the dry level sensor, calculate and record the increment of the electrical capacitance of the capacitive level sensor with immersion in a dielectric substance, occasionally produce consistent measurement and fixation of the complex current through the fill dielectric substance capacitive level sensor and standard on each of the two specified frequencies for each periodic measurements define and record the capacitance of the capacitive level sensor, then determine the relative filling of the dielectric substance capacitive level sensor as the difference of values of electrical capacitance capacitive fill level sensor and an electric capacity of dry capacitive level sensor is related to the increment of electric capacity fully immersed in a dielectric substance capacitive level sensor.



 

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