RU2499231C1 - Device to measure level of dielectric substance - Google Patents

Device to measure level of dielectric substance Download PDF

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RU2499231C1
RU2499231C1 RU2012117010/28A RU2012117010A RU2499231C1 RU 2499231 C1 RU2499231 C1 RU 2499231C1 RU 2012117010/28 A RU2012117010/28 A RU 2012117010/28A RU 2012117010 A RU2012117010 A RU 2012117010A RU 2499231 C1 RU2499231 C1 RU 2499231C1
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calculator
input
electric capacitance
level
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Станислав Викторович Балакин
Ярослав Вячеславович Хачатуров
Владимир Юрьевич Федулов
Илья Евгеньевич Одновол
Сергей Владимирович Сидоров
Дмитрий Леонидович Сербинов
Александр Юрьевич Федулов
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Открытое акционерное общество "Ракетно-космическая корпорация "Энергия" имени С.П. Королева"
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Abstract

FIELD: measurement equipment.
SUBSTANCE: device for measurement of a dielectric substance level comprises a standard, the first output of which is connected to the first input of a switching unit, and the second output is connected to the output of a generator of sine voltage and to the first measurement input of the device. Metering inputs of the device from the second to (n+1), where n - quantity of dipoles, are connected to inputs of the switching unit, the outlet of which via serially connected current-voltage converter, a scale amplifier and an analogue-to-digital converter is connected to the input of the measurement control block, outputs of which are connected to the switching unit, the scale amplifier and the analogue-to-digital converter, and also to the control block by frequency and to a calculator of electric capacitance and a calculator of active resistance. The measurement control block is connected to a mode control block, outputs of which are connected to inputs of the control block by frequency, a calculator of full increment of electric capacitance, a calculator of level, a calculator of current increment of electric capacitance and a block of switching control, the outlet of which is connected to the switching unit. The electric capacitance calculator is connected to the calculator of current increment of electric capacitance and to the calculator of full increment of electric capacitance, which is connected to the level calculator. The analogue-to-digital converter is connected to the electric capacitance calculator and the active resistance calculator, which are connected to the control block by frequency, the outlet of which is connected to the generator of sine voltage. The calculator of current increment of electric capacitance is connected to the level calculator, at the same time the output of the switching control unit is the device output. At the same time the device comprises the second unit of substitution circuit unit, besides, outputs of the first and second blocks of substitution circuit setting are connected to the first switch, the control input of which is connected to the control input of the second switch and to the mode control block. At the same time the output of the first switch is connected to the calculator of electric capacitance and active resistance calculator, which is connected to the second switch, the output of which is connected to the threshold element, which is connected to the measurement control block, and the output of the threshold element is an output of the device and is connected to the control input of the third switch, which is connected to the level calculator, at the same time the outlet of the second switch and the outlet of the third switch are the device outputs.
EFFECT: higher reliability of measurement.
3 dwg

Description

The invention relates to electrical engineering, and specifically to measuring the electrical parameters of two-terminal devices used as sensors for physical processes (temperature, pressure, level of liquid and granular media, etc.) at industrial facilities, vehicles, as well as in systems for measuring the level of refueling space technology.

The “Multipoint level switch (its variants)” device, described in RF patent No. 2025666, IPC: G01F 23/26, including a group of capacitive measuring sensors, an alternating voltage generator, two switches, two current-voltage converters, and a subtracting device, was selected as an analogue , synchronous detector, comparator, two triggers, differentiator, clock, coincidence circuit, pulse counter, adder and digital indicator. Moreover, each measuring sensor is made in the form of two plane-parallel capacitors with unequal areas of the electrodes, which are located horizontally and symmetrically with respect to the middle lines of the sensors. In addition, instead of transformer-type current comparators, a subtractor device was used, which can be built on an integrated circuit.

However, the specifics of the operation of rocket and space technology products for measuring the level of dielectric matter sets its own requirements, contributing to the search for new technical solutions in the field of measurements. Denote the most characteristic of them.

- Distance to 500 meters of a capacitive level sensor from a measuring instrument. An example of this is the process of determining the complex resistance parameters of a capacitive refueling level sensor mounted in a rocket tank, which is located in the test building or on the launch complex during refueling with fuel components.

- High accuracy of measurement of parameters of a remote two-terminal device, which is a capacitive level sensor. Obviously, the accuracy of measurements is directly related to the volume of guaranteed fuel reserves on board the rocket. The higher the accuracy of the measurements, the lower the required guaranteed fuel reserves, the higher the efficiency of the rocket, allowing to bring a large payload.

- The requirement for a high-tech rocket preparation, excluding the procedure for pre-setting the measuring instrument by a human operator, as well as allowing the operation of one measuring instrument with several capacitive rocket level sensors in turn.

- High speed measurement of the level of the dielectric substance, which allows to expand the functionality of the device and use it in a similar way in the level gauge of the on-board terminal automatic control system, which is the rocket fuel consumption control system.

The device described in the article by Yu.R. Agamalov, D. A. Bobylev, V. Yu. Kneller “Measuring instrument-analyzer of complex resistance parameters based on a personal computer” in the journal “Measuring Technique” 1996, No. 6 was chosen as another analogue .

The device for determining the parameters of a two-terminal network contains the first and second measuring inputs, a sinusoidal voltage generator, an equivalent circuit setting unit, a standard, the first output of which is connected to the first input of the switching unit, a current-voltage converter, a scale amplifier, and an analog-to-digital converter.

The analogue uses a scheme of indirect measurement of parameters when generating a voltage of a sinusoidal effect on the measurement object, which has found application due to the invariance with respect to the nature of the measurement object and its equivalent circuit. In the analogue, two complex currents are measured, which are converted into proportional voltages, the voltage at the measurement object and at the resistive measure standard. In order to obtain the measurement information necessary for calculating the complex resistance or conductivity, the measurement circuit is connected cyclically by signals from a personal electronic computer (PC) first to the measurement object and then to the resistive measure with the corresponding phase switching of the reference voltage with discreteness Δ ψ = π 2 n

Figure 00000001
where n is an integer. As a result of each measurement cycle, a voltage is obtained that corresponds to the projection of the measured voltage vector onto the phase-shifting reference voltage vector (symmetrical rectangular meander). Codes that carry information about the projections of the vector of the measured voltage on the vector of the reference voltage are sent to a PC to calculate the real and imaginary components of the voltage at the measurement object and resistive measure. It can be seen from the description that the measurement circuit used in the analogue requires phase measurements and a four-wire circuit for connecting the measured object. When using an analog to measure the parameters of a remote measurement object, a result is obtained with a large measurement error. This is because the sinusoidal effect on the remote measurement object will receive an ambiguous phase shift due to the influence of a long line, and therefore, with respect to the cyclically phase-shifting reference meander, the sinusoidal effect will have an indefinite phase shift, which will lead to a significant measurement error.

The disadvantages of analogues include: insufficient accuracy in determining the parameters of a capacitive level sensor remote at a certain distance; low performance in some cases of its use, for example, in signaling devices for the passage of a given height of a tank by the level of a dielectric fluid; lack of adaptability of rocket preparation, due to the need for preliminary adjustment of equipment by the operator.

The closest in technical essence and the achieved positive effect to the claimed device is the device described in RF patent RU 2262668 C2, IPC: G01F 23/26, “Device for measuring the level of dielectric substance”, authors Balakina SV, Dolgova B.K. ., Khachaturova Y.V., Odnovola I.E., selected as a prototype.

A device for measuring the level of a dielectric substance containing a standard, the first output of which is connected to the first input of the switching unit, and the second output of the standard is connected to the output of the sinusoidal voltage generator and to the first measuring input of the device, while the measuring inputs of the device are from second to (n + 1) -th, where n is the number of two-terminal devices, are connected to the corresponding inputs of the switching unit, the output of which is through a series-connected current-voltage converter, a large-scale amplifier, and analog-to-digital The new converter is connected to the first input of the measurement control unit, the first to fifth outputs of which are connected respectively to the first control inputs of the switching unit, a scale amplifier, and an analog-to-digital converter, as well as to the first input of the frequency control unit and to the first inputs of the electric capacitance calculator and active resistance calculator, and the second input of the measurement control unit is connected to the first output of the mode control unit, the outputs of which are connected from the second to the sixth respectively directly to the second input of the frequency control unit, to the first input of the calculator of the full increment of the electric capacitance, to the first input of the level calculator, to the first input of the calculator of the current increment of the electric capacitance and to the input of the switching control unit, the output of which is connected to the second control input of the switching unit, the output of the calculator of the electric capacitance is connected to the second input of the calculator of the current increment of the electric capacitance and to the second input of the calculator of the full increment of the electric capacitance, the output of which is connected to the second input of the level calculator, while the output of the analog-to-digital converter is connected to the second inputs of the electric capacitance calculator and the active resistance calculator, the third inputs of which are connected to the first output of the frequency control unit, the second output of which is connected to the control input of the generator sinusoidal voltage, and the output of the calculator of the current increment of the electric capacitance is connected to the third input of the level calculator, while the output of the control unit Switchgears is an output device.

When the prototype is in operation while measuring the level of a dielectric substance using a capacitive level sensor remote at a sufficiently large distance (up to 400 meters) from the measuring instrument, the result obtained has a small measurement error. The calculation of the parameter values (electric capacitance and active resistance) of a dry and capacitive level sensor filled with a dielectric substance, as well as the calculation of the value of the total increment of the electric capacitance of a level sensor when it is completely immersed in a dielectric substance, is ensured under the same conditions of a long communication line. These conditions make it possible to take into account the influence of the long communication line on the results of calculations by the prototype of the level sensor parameters and to almost completely eliminate the influence of the long line on the level calculation result. However, the practice of operating rocket and space technology at launch complexes shows that often in the contact groups of cable cable electrical connectors there are transient resistances or breaks, since the communication line passes through cable mast farms under atmospheric precipitation. In this case, a significant error may arise when measuring the main parameter - the level of the dielectric substance. And this can have serious consequences, for example, refueling tanks of a carrier rocket.

From the above it follows that the disadvantage of the prototype is the significant influence of the cable communication line on the result of level measurement in the case when the parameters of the communication line significantly change directly during normal operation.

The technical result of the proposed device for measuring the level of the dielectric substance is to increase the reliability in its measurement, which consists in eliminating incorrect results of measuring the level of the dielectric substance, which can occur due to changes in the electrical resistance of the long communication line that occurs when there is poor contact in the electrical connectors, when the conductive wires are broken , on "cold" rations, with moisture and for a number of other reasons.

The technical result is achieved by the fact that in the device for measuring the level of the dielectric substance containing the standard, the first output of which is connected to the first input of the switching unit, and the second output of the standard is connected to the output of the sinusoidal voltage generator and to the first measuring input of the device, while the measuring inputs of the device are the second in (n + 1) th, where n is the number of two-terminal devices, are connected to the corresponding inputs of the switching unit, the output of which is through a series-connected current-to-converter voltage, a scale amplifier, and an analog-to-digital converter are connected to the first input of the measurement control unit, the first to fifth outputs of which are connected respectively to the first control inputs of the switching unit, a scale amplifier, and an analog-to-digital converter, as well as to the first input of the frequency control unit and to the first inputs of the electric capacitance calculator and the active resistance calculator, and the second input of the measurement control unit is connected to the first output of the mode control unit, the outputs of the second from the sixth are connected respectively to the second input of the frequency control unit, to the first input of the calculator of the full increment of the electric capacitance, to the first input of the level calculator, to the first input of the calculator of the current increment of the electric capacitance and to the input of the switching control unit, the output of which is connected to the second the control input of the switching unit, and the output of the calculator of the electric capacitance is connected to the second input of the calculator of the current increment of the electric capacitance and to the second input the calculator of the full increment of the electric capacitance, the output of which is connected to the second input of the level calculator, while the output of the analog-to-digital converter is connected to the second inputs of the electric capacitance calculator and the active resistance calculator, the third inputs of which are connected to the first output of the frequency control unit, the second output of which is connected to the control input of the sinusoidal voltage generator, and the output of the calculator of the current increment of the electric capacitance is connected to the third input of the calculation level switch, while the output of the switching control unit is the output of the device, in contrast to the prototype, the second block for setting the equivalent circuit is introduced, and the outputs of the first and second blocks for setting the equivalent circuit are connected respectively to the first and second inputs of the first key, the control input of which is connected to the control input the second key and to the seventh output of the mode control unit, while the output of the first key is connected to the fourth inputs of the electric capacitance calculator and the active resistance calculator, the output which is connected to the input of the second key, the first output of which is connected to the first input of the threshold element, the second input of which is connected to the sixth output of the measurement control unit, and the output of the threshold element is the output of the device and connected to the control input of the third key, the input of which is connected to the output of the calculator level, while the second output of the second key and the output of the third key are the outputs of the device.

The signs characterizing the introduction of the second block of the task of the equivalent circuit, the connection of the first and second blocks of the task of the equivalent circuit via a managed key to the inputs of the calculator of electric capacitance and the calculator of active resistance, allow you to connect the second equivalent circuit and determine the value sequentially, after calculating the parameters of the two-terminal device and accordingly determining the level transient resistance in the electrical measuring circuits of a capacitive level sensor. The signs characterizing the connection of the output of the active resistance calculator through the second controlled key and the newly introduced threshold element to the control input of the third key allow the measured value of the active resistance of the capacitive level sensor circuits to be compared in the threshold element with an allowable resistance value. If the measured value of the circuit resistance goes beyond the tolerance, the output of the level calculator is disconnected from the output of the device through the third key. In this case, the results of calculating the level are not supplied to the output of the device, that is, they are recognized as unreliable by setting from the output of the threshold element to the output of the device a sign of inaccuracy of the calculated level value. Thus, the claimed device acquires a new quality that does not allow errors in the value of the refueling level and, consequently, errors during refueling of the pH due to malfunctions in the long communication line between the capacitive sensor and the measuring equipment. This quality significantly increases the reliability of measuring the fuel level in preparing the product for regular operation.

Figure 1 presents a functional diagram of a device for measuring the level of dielectric substance.

Figure 2 presents the algorithm of the device for measuring the level of dielectric substance.

Figure 3 presents the algorithm for measuring currents through a capacitive level sensor and a reference.

The functional diagram of a device for measuring the level of a dielectric substance shown in FIG. 1 contains n-two-terminal devices, in particular, capacitive level sensors 1-1, ..., 1-n, a cable communication line 2, measuring inputs of a device 3, 4-1, ... 4- n, as well as a sinusoidal voltage generator 5 connected to a reference 6, the output of which is connected through a series-connected switching unit 7, a current-voltage converter 8, a scale amplifier 9 and an analog-to-digital converter 10 connected to the input of the measurement control unit 11, the control unit I have a frequency of 12, equivalent circuit assignment blocks 13 and 14, a mode control unit 15, a first key 16, an electric capacitance calculator 17, an active resistance calculator 18, a full increment calculator of an electric capacitance 19, a second key 20, a current increment calculator of an electric capacitance 21, switching control unit 22, third key 24, threshold element 25. The output of the analog-to-digital converter 10 is connected to the second inputs of the calculator of the electric capacitance of the sensor 17 and the calculator of the active resistance 18. Capacitive sensors through the measuring inputs of the device 3, 4-1, ..., 4-n, they are connected to the corresponding inputs of the switching unit 7, and the outputs from the first to the sixth measurement control unit 11 are connected to the control inputs of the switching unit 7, current-voltage converter 8, scale 9 an amplifier, analog-to-digital converter 10, to the first input of the frequency control unit 12, to the first inputs of the calculator 17 of the electric capacitance and the calculator 18 of the active resistance and to the second input of the threshold 25 element, the output of which is connected to the control input retego key 24. Moreover, the block 12 outputs the frequency control connected to the control input sinusoidal voltage generator 5 and to the third inputs of the calculator 17 and the capacitance calculator 18 resistance. The first to seventh mode control unit 15 is connected respectively to the measurement control unit 11, to the frequency control unit 12, to the first inputs of the calculator 19 of the full increment of the electric capacitance, the calculator 21 of the current increment of the electric capacitance, the level calculator 23, respectively, to the control unit 22 by switching to the control inputs of the keys 16, 20. Blocks for setting equivalent circuits 13 and 14 are connected to the inputs of the key 16, the output of which is connected to the third inputs of the computers of the electric capacitance and active resistance otivleniya. The output of the calculator 17 of the electric capacitance is connected to the second inputs of the calculator 19 of the full increment of the electric capacitance and the calculator 21 of the current increment of the electric capacitance, the output of which is connected to the third input of the calculator 23 level, the output of which is connected to the input of the third key 24, the output of which is the output of the device. The output of the active resistance calculator 18 is connected to the input of the second key 20, the first output of which is connected to the input of the threshold 25 element, the output of which is the output of the device and connected to the control input of the third 24 keys, and the second output of the second key 20 is the output of the device. The output of the switching control unit 22 is connected to the second control input of the switching unit 7 and is the output of the device. Moreover, the n-capacitive level sensors are connected to the measuring 3 and 4-1, ..., 4-n inputs through a shielded cable line 2 communication. The screens of the communication line at the measuring inputs are connected and connected to the earth terminal of the sinusoidal voltage generator 5.

We will consider the operation of the device using an example of measuring the level of a dielectric substance, for example, kerosene or oxygen, in the tanks of a multi-stage rocket. Capacitive level sensors connected via cable line 2 communications are removed from the device at a distance of up to 500 meters. The electrical capacitance of a dry level sensor can be about 500 pF, and the stray electrical capacitance of the core-screen of a cable communication line, which can be used, for example, cable PK 75, can be about 30,000 pF. The electrical equivalent circuit of the capacitive level sensor corresponds to the parallel connected capacitance Cp and the active resistance R. The active component of the total resistance of the capacitive level sensor is determined by the insulation resistance of the cable communication line, kerosene grade and humidity of the gas tank of the fuel tank. The value of the active component can range from 200 kOhm to 20 mOhm. Therefore, taking this component into account when determining the complex resistance of a capacitive level sensor is essential for the accuracy of measuring the level of a dielectric substance.

Presented in figure 2, the algorithm of the device for measuring the level of dielectric substance provides an explanation of the operation of the device according to figure 1. Blocks marked with a dotted line and including one or another function of the algorithm indicate that this function belongs to the covered block.

According to the algorithm of figure 2, the operation of the device consists of two modes.

- The device settings mode, which consists in sequential measurement through a cable line 2 of the current connection through each capacitive level sensor and a standard, followed by calculation of the electric capacitance values of each dry (unfilled with a dielectric substance) capacitive level sensor. Then follows the calculation of the increment value of the electric capacitance of each sensor completely immersed in the dielectric substance. When calculating the increment value of the electric capacitance of the level sensor, completely immersed in the dielectric substance, the calculated value of the electric capacitance of the dry sensor and the specified values of the dielectric constant of the fuel (oxidizer, fuel) and the gas medium of the tank cushion are used. Moreover, all measured and calculated values of the values are stored in the memory of the functional blocks of the device.

- The level measurement mode, which consists in measuring the current values through each capacitive sensor and a standard through a cable connection line, followed by calculating the values of the current electric capacitance of each capacitive level sensor filled with a dielectric substance. Then, the current increment of the electric capacitance of each filled sensor is calculated, after which the relative filling, expressed as a percentage, of each capacitive sensor is calculated (the level is calculated). In this case, in contrast to the prototype, additional functional units are introduced into the device that implement an additional, newly introduced mode of monitoring the state of electric circuits of capacitive sensors. The newly introduced monitoring of the sensor circuits is only used in level measurement mode. The results of monitoring the state of the sensor circuits through the newly introduced functional unit turn off / connect the level calculator to the output of the device, while the indication of the reliability of the measurement is removed / set.

The device for measuring the level of dielectric substance according to figure 2 works as follows. The mode control unit 15 first sets a device setting mode.

In this case, the number of necessary measurements is given to the measurement control unit 11, in this case 2 for each sensor, since the capacitive level sensor is a two-element two-terminal device. The values of the currents obtained through the measurement through each sensor and the reference will be used in the future to calculate the real dry electrical capacitance of each sensor in the setup mode and to calculate the real current electric capacitance of each sensor in the level measurement mode (when each sensor is filled with a dielectric substance).

In the frequency control unit 12, the frequencies ω 1 , ω 2 are set at which currents will be measured.

In the calculator 19 of the full increment of the electric capacitance, the values of the dielectric constant of the oxidizing agent and fuel, as well as the dielectric constant of the gaseous medium in the gas cushion, are provided. These parameters are necessary to obtain the calculated values of the total increment of the electric capacitance of each capacitive sensor, completely immersed in the corresponding dielectric substance.

In the calculator 21 of the current increment of the electric capacitance, the dielectric constants of the oxidizing agent and fuel, as well as the dielectric constants of the gaseous medium in the gas cushion, are issued. These parameters are necessary to obtain the calculated values of the current increment of the electric capacitance of each capacitive sensor, which is filled in the process of filling with a dielectric substance.

The newly introduced first key 16, to the first and second inputs of which the task units 13 and 14 of the equivalent circuit are connected, and the block 14 is reintroduced, will issue to the fourth inputs of the electric capacitance calculator 17 and the active resistance calculator 18, respectively, the equivalent circuits of the measurement objects, in particular capacitive sensors level. If the mode control unit 15 does not specify the mode of monitoring the state of the sensor electrical circuits (it is set only in the mode of measuring the level of dielectric substance), then the block 13 is connected to the inputs of the blocks 17 and 18 through the key 16 and the corresponding equivalent circuit is issued. Otherwise, block 14 is connected and another equivalent circuit is issued. Moreover, the second inputs of blocks 17 and 18, connected to the output of the analog-to-digital converter 10, are issued in the process of setting or measuring the level of the current values, and the third inputs of blocks 17 and 18 are fed from the output of the control unit 12 according to the frequency of the frequency values at which current measurements. The equivalent circuit of the measurement object formed by block 13 corresponds to a parallel connected electric capacitance and active resistance, while the calculated dependencies for determining the parameters of the measurement object are of the following form and which are fixed in the above blocks:

C = ( I ω one I ω one E T R E T ) 2 - ( I ω 2 I ω 2 E T R E T ) 2 ω one 2 - ω 2 2 ; ( one )

Figure 00000002

R = ω one 2 - ω 2 2 ( I ω 2 I ω 2 E T R E T ) 2 ω one 2 - ( I ω one I ω one E T R E T ) 2 ω 2 2 . ( 2 )

Figure 00000003

where ω 1 , ω 2 are known values and are set by the frequency control unit 12; R ET - the known value and is set by block 13 defining the equivalent circuit; I ω1 , I ω2 - values of currents, which are measured both during setup and in the measurement process and are formed from the output of the analog-to-digital converter.

The equivalent circuit formed by block 14 corresponds to a series-connected electric capacitance and active resistance, while the calculated dependence for determining the resistance of the electric circuit of a capacitive level sensor has the following form and which is fixed in block 18

r = R E T ω one 2 ( I ω one E T I ω one ) 2 - ω 2 2 ( I ω 2 E T I ω 2 ) 2 ω one 2 - ω 2 2 . ( 3 )

Figure 00000004

In the switching control unit 22, the number of capacitive level sensors connected to the device is set, and a signal is also output through which the unit 22 through the switching unit 7 controls the connection of the current-voltage of the second measuring input (first capacitive level sensor) to the measuring circuit of the converter 8.

After the mode control unit 15 has brought the device to the initial state necessary for the process of setting it up, the setting process begins.

In this case, according to FIG. 2, the measurement control unit 11 measures and fixes currents through the first capacitive level sensor and a reference in accordance with the algorithm of FIG. 3. According to Fig. 3, the measurement control unit 11, to which the number of measurements is set by the mode control unit 15 (in this case 2), sets the frequency control unit 12 to the first frequency setting signal at which current measurements should be made through the first capacitive level sensor and a reference 6. According to FIG. 3, block 11 assigns the current measurement frequency index i to 1 and sets the corresponding signal to frequency control unit 12. After that, the frequency control unit 11 sets and fixes the value of the first frequency ω i in the calculator 17 of the electric capacitance and in the calculator 18 of the active resistance, and sends a signal to the control input of the sinusoidal voltage generator 5, according to which the latter generates a voltage of a given first frequency ω i .

Voltages of a given frequency U ωi are supplied to the measuring inputs of the device to power the connected capacitive level sensor and reference. Next, the measurement control unit 11 sets the position key j of the switching unit 7. The position of the key is 2, and the value j is assigned the value 1. According to this feature, the first or current capacitive level sensor is disconnected from the measuring circuit, and instead of it, the reference 5 is connected to the measuring circuit. As a reference, a resistor of resistance R ET can be used.

The current value is measured as follows. According to figure 1, the current through the reference from the output of the switching unit 7 is fed through a current-voltage converter 8 to the input of the scale amplifier 9. The scale amplifier provides voltage amplification in accordance with the scale that the measurement control unit sets to it 11. From the output of the scale amplifier, the voltage is supplied to the input of the analog-to-digital Converter 10 integrating type. The analog-to-digital converter (ADC) is a push-pull iterator. The choice of this type of ADC is primarily due to the high linearity of the characteristics, high resolution and good suppression of high-frequency noise. The ADC operates in two cycles, the first cycle is the charge of the integrator, the second cycle is its discharge. In the first cycle, the input signal is integrated, which is a periodic function, in the second cycle, the signal from the reference voltage source is integrated. The resolution of the ADC, which determines the resolution of the device as a whole, is proportional to the time of the second cycle (discharge of the integrator), as well as the frequency of the filling pulses. The ADC clock switching and the supply of filling pulses are controlled by the measurement control unit 11. The digitized value of the measured current is supplied to the measurement control unit 12 to control the gain scale. The control of the gain scale is aimed at improving the accuracy of the ADC. The scaling is designed in such a way that the digital value of the signal taken from the ASC should not be less than half the capacity of the ADC. The scaling algorithm is presented in figure 2. According to this algorithm, the number α is analyzed, which is equal to the ratio of the total ADC capacitance to the digital value of the measured current. Based on the calculated value of α, one of four scales is selected (16; 8; 4; 2; 1). The current value measured with an appropriate scale is recorded in the calculator 17 of the electric capacitance, in the calculator 18 of the active resistance for its further use in the calculations according to the expressions (1), (2) and (3). Further, according to FIG. 3, if j is not equal to 2, then its value in the measurement control unit 11 increases by one and a control signal is generated there to switch the key of the switching unit 7 to the second position. This corresponds to the fact that the standard is switched off and a capacitive level sensor is connected to the measuring circuit.

Further, the procedure for measuring current through a level sensor is determined by the steps described when measuring current through a standard. After the measured value of the current through the capacitive level sensor is recorded in the calculator 17 of the electric capacitance and the calculator 18 of the active resistance, the algorithm according to figure 3 will go on to analyze the condition in which j is 2. Since the key of the switching unit 7 is in the second position, that condition will be fulfilled and the algorithm will proceed to the analysis of the following condition, in which the analysis of the current measurement frequency will be carried out. Since the measurement was carried out at the first frequency, the condition will not be satisfied, and the algorithm will proceed to the steps to set the second frequency ω i . As a result, the action i: = i + 1 will be performed and the measurement control unit 11 will set a signal to set the second frequency ω i . According to this signal, the frequency control unit 12 generates a signal to the sinusoidal voltage generator 5 in order to set a second frequency intended for supplying a capacitive level sensor or reference. At the same time, the frequency control unit 12 sets and fixes the value of the second frequency in the calculator 17 of the electric capacitance and in the calculator 18 of the active resistance, which is then used to calculate the parameters of the two-terminal device. After that, the measurement control unit 11 initiates a measurement. The procedure for measuring currents at a second frequency is repeated as described above.

After the number of measurements i is equal to 2, the condition of the last block of the algorithm according to figure 3 will be satisfied and the algorithm will finish its work. This will correspond to the completion of the current measurement procedure through the first capacitive level sensor.

According to figure 2, the algorithm calculates and fixes in blocks 17 and 18 the values of the electric capacitance and active resistance of the first capacitive level sensor. The results of calculating the value of the electric capacitance from the block 17 go to the calculator 19 of the full increment of the electric capacitance and to the calculator 21 of the current increment of the electric capacitance, which are recorded by a command from the block 15 control modes in the memory cells corresponding to the number of the connected measuring input. The calculated value of the active resistance from the output of block 18 is supplied through the second key 20 to the output R of the device. The value of active resistance characterizes the state of the land and onboard cable networks and is analyzed by the equipment interfaced with the device for compliance with the required operational characteristics.

The control signal of the mode control unit 15 in the calculator 19 of the full increment of the electric capacitance calculates the total increment of the electric capacitance of the capacitive level sensor, completely immersed in the dielectric substance, according to the following relationship:

FROM P R = FROM FROM At X ( ε F - ε G ) , ( four )

Figure 00000005

where С СУХ - electric capacitance of a dry capacitive level sensor, calculated according to dependence (1);

ε W - dielectric constant of the dielectric substance;

ε G is the dielectric constant of the gas cushion located in the tank of the rocket above the dielectric substance. The results of calculating the total increment of the electric capacitance are recorded in the level calculator 23 in the memory cell corresponding to the number of the measured input (capacitive level sensor number).

Then the algorithm proceeds to the analysis of the condition k = n. The condition will not be fulfilled, since the second measuring input 4-1 (the first capacitive level sensor) has been connected. Therefore, the algorithm will proceed to the action k = k + 1 in the switching control unit 22, which, through the switching unit 7, will disconnect the measurement input 4-1 and connect the measurement input 4-2. Signs characterizing the connection of the output of the mode control unit to the input of the switching control unit, the output of which is connected to the second control input of the switching unit, provide a serial connection of the measuring inputs of the device to the measuring circuit of the current-voltage converter, thereby improving the efficiency of the device, connecting the device in series capacitive level sensors. Further operation of the device will correspond to the above actions until the condition k = n is satisfied, i.e. until the values of the electric capacitances of the dry level sensors are calculated and the values of the electric capacitances of all n-level sensors completely immersed in the dielectric material, connected in series through the cable network 2 to the measuring inputs, are calculated. When the condition k = n is fulfilled, the device setup mode ends and the algorithm proceeds to measure the level of the dielectric substance. In the level measurement mode, the calculator 19 of the full increment of the electric capacitance is turned off, since this function is used in this mode. The calculated values of the electric capacitance of the fully immersed capacitive sensors are recorded in the level calculator 23 and will be used in calculating the level for each capacitive sensor in the level measurement mode.

The mode control unit 15 sets the dielectric substance level measurement mode and in the switching control unit 22 assigns k a value of 1. In this case, the mode control unit sets either the dielectric substance level measurement mode or the state monitoring mode of the electrical circuits of the level sensors.

In the first case, block 15 connects via block 16 the block 13 for setting the equivalent circuit to the inputs of calculator 17 of electric capacitance and calculator 18 of active resistance, and also through the second key 20, the output of calculator 18 of active resistance connects to the input of the device. The output of the level calculator 23 through the third key remains connected to the output of the device, which gives the value of the level of the dielectric substance.

In the second case, block 15 connects via block 16 the block 14 for setting the equivalent circuit to the inputs of calculator 17 of electric capacitance and calculator 18 of active resistance, and also through the second key 20, the output of calculator 18 of active resistance connects to the input of the threshold element 25, the memory of which is from block 11 measurement control entered the limit value of the resistance of the electrical circuits of the sensors. In this case, the threshold element 25 controls the key 24, which in case of exceeding the measured resistance value of the sensor circuit limit value disconnects the output of the level calculator 23 from the output of the device, which gives the value of the level of dielectric substance. In this case, the threshold element sets at the device output a sign of inaccuracy of the level value.

The switching control unit through the switching unit 7 connects the first measuring input to the measuring circuit. After that, the mode control unit 15 generates a signal in the measurement control unit 11, by which the latter starts the current measurement algorithm through the standard and the first capacitive level sensor filled with dielectric material. The procedure for measuring currents through a capacitive level sensor and a standard is carried out by blocks 8, 9, 10 and 11 and is presented by the algorithm according to figure 3 of the prototype.

After the process of measuring currents through the capacitive level sensor and the reference is completed, the algorithm according to Fig. 2 will proceed to calculate the current value of the electric capacitance of the filled level sensor and its active resistance, using the measured current values through the capacitive level sensor and the reference. The above procedures are performed by blocks 17 and 18. The calculated value of the electric capacitance of the filled sensor C TEK from the output of block 17 goes to the calculator 21 of the current increment of the electric capacitance, which calculates and fixes the value of the increment of the electric capacitance of the sensor in the memory cell corresponding to the number of the measuring input. The value of the increment of the electric capacity of the filled sensor is calculated by the following dependence:

Δ FROM T E TO = FROM T E TO - FROM FROM At X , ( 5 )

Figure 00000006

where C TEK is the current value of the electric capacitance of the level sensor filled with a dielectric substance calculated on the basis of measured currents.

For the first case, the calculated value of the active resistance of the capacitive level sensor filled with a dielectric substance from the output of block 18 is sent to the R output of the device and is used to assess the state of the sensor and its cable network.

Then, according to the control action of the mode control unit 15, the level calculator 23 calculates the relative filling of the capacitive level sensor with the dielectric material, and the calculator 21 sets the value of the current increment of the electric capacitance ΔC TEK of the level sensor filled with the dielectric substance into the level calculator 23.

The level 23 calculator calculates it according to the following relationship:

h H = Δ FROM T E TO FROM P R = FROM T E TO - FROM FROM At X FROM FROM At X ( ε F - ε G ) . ( 6 )

Figure 00000007

The value of the full increment of the electric capacitance of a fully immersed sensor is stored in the memory of the level 23 computer in the device setup mode.

Signs characterizing the connection through the key 16 of the blocks 13, 14 defining the equivalent circuit to the inputs of the calculator 17 of the electric capacitance and the calculator 18 of the active resistance, provide control of the state of the electrical circuits of capacitive level sensors. And the signs characterizing the connection through the second key 20 of the output of the calculator 18 of the active resistance to the input of the threshold element 25, in the memory of which from the measurement control unit 11 a limit value of the resistance of the sensor electrical circuits is entered, while the threshold element 25 controls the key 24, which if the measured value is exceeded the value of the resistance of the sensor circuit limit value disconnects the output of the level 23 computer from the output of the device, provide disconnection from the device output of an invalid value gravel level of dielectric substance. Thus, the combination of the above features gives the claimed device, in contrast to the prototype, a new quality - improving the reliability in measuring the level of dielectric substance, which consists in eliminating incorrect measurement results that can occur due to changes in the electrical resistance of a long communication line that occurs when there is poor contact in the electrical connectors , with breaks in conductive conductors, on "cold" rations, with moisture, and for a number of other reasons. In this case, the threshold element sets at the device output a sign of inaccuracy of the level value.

The value of the h / H level of the capacitive sensor is fed to the output of the device with which the launch complex equipment is interfaced, which controls the supply of fuel components (dielectric substances) through the ground processing equipment to the rocket tanks.

Then the algorithm proceeds to the analysis of the condition k = n. The condition will not be fulfilled since the first measuring input has been connected. Therefore, the algorithm will proceed to the action k = k + 1 in the switching control unit 22, which, through the switching unit 7, will disconnect the measurement input 4-1 and connect the measurement input 4-2. Further operation of the device will correspond to the above actions until the condition k = n is satisfied, i.e. until the values of the level of filling of the dielectric substance of each capacitive level sensor are calculated.

After that, the mode control unit 15 sets the condition for monitoring the state of the electrical circuits of the level sensors, while the key 16 connects the equivalent circuit setting unit 14 to the inputs of the electric capacitance calculator 17 and the active resistance calculator 18, the output of which through the second key 20 will be connected to the threshold element 25.

In this case, the mode control unit 15 will assign a value of one in the switching control unit 22, as a result of which the latter will connect the first measuring input through the switching unit 7 and start the process of monitoring the state of the electrical circuits of the first capacitive level sensor, will be repeated again. The procedure of cyclic control of the electrical state of each level sensor will continue until the condition k = n is fulfilled.

In the example of the device in formulas (1), (2) and (3) there is such a function as the extraction of the square root. The square root algorithm is widely known (for example, see RF patent RU 2262668 C2, IPC: C01F 23/26).

The claimed device by the authors tested on a breadboard product. Currently, the authors are creating a system for measuring the level of a rocket block refueling system, which is designed to modernize the ground equipment of one of the launch launchers of the Baikonur training ground and the launch complex of the Kuru cosmodrome of the Guiana Space Center.

Used Books

1. Balakin S.V., Dolgov B.K., Khachaturov Y.V., Odnovol I.E. "Device for measuring the level of dielectric substance", RF patent No. 2262668 C2, class. C01F 23/26.

2. Agamalov Yu.R., Bobylev D.A., Kneller V.Yu. Measuring instrument-analyzer of complex resistance parameters based on a personal computer. Measuring technique. 1996, No.6, p. 56-60.

3. RF patent No. 2025666, cl. G01F 23/26, "Multipoint level switch (options)."

Claims (1)

  1. A device for measuring the level of a dielectric substance containing a standard, the first output of which is connected to the first input of the switching unit, and the second output of the standard is connected to the output of the sinusoidal voltage generator and to the first measuring input of the device, while the measuring inputs of the device are from second to (n + 1) -th, where n is the number of two-terminal devices, are connected to the corresponding inputs of the switching unit, the output of which is through a series-connected current-voltage converter, a large-scale amplifier, and analog-to-digital The new converter is connected to the first input of the measurement control unit, the first to fifth outputs of which are connected respectively to the first control inputs of the switching unit, a scale amplifier, and an analog-to-digital converter, as well as to the first input of the frequency control unit and to the first inputs of the electric capacitance calculator and active resistance calculator, and the second input of the measurement control unit is connected to the first output of the mode control unit, the outputs of which are connected from the second to the sixth respectively directly to the second input of the frequency control unit, to the first input of the calculator of the full increment of the electric capacitance, to the first input of the level calculator, to the first input of the calculator of the current increment of the electric capacitance and to the input of the switching control unit, the output of which is connected to the second control input of the switching unit, the output of the calculator of the electric capacitance is connected to the second input of the calculator of the current increment of the electric capacitance and to the second input of the calculator of the full increment of the electric capacitance, the output of which is connected to the second input of the level calculator, while the output of the analog-to-digital converter is connected to the second inputs of the electric capacitance calculator and the active resistance calculator, the third inputs of which are connected to the first output of the frequency control unit, the second output of which is connected to the control input of the generator sinusoidal voltage, and the output of the calculator of the current increment of the electric capacitance is connected to the third input of the level calculator, while the output of the control unit Switching is the device output, characterized in that a second equivalent circuit setting unit is introduced, the outputs of the first and second equivalent circuit setting units being connected respectively to the first and second inputs of the first key, the control input of which is connected to the control input of the second key and to the seventh output of the control unit modes, while the output of the first key is connected to the fourth inputs of the calculator of electric capacitance and the calculator of active resistance, the output of which is connected to the input of the second key, ne the first output of which is connected to the first input of the threshold element, the second input of which is connected to the sixth output of the measurement control unit, and the output of the threshold element is the output of the device and connected to the control input of the third key, the input of which is connected to the output of the level calculator, while the second output of the second key and the output of the third key are the outputs of the device.
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RU2262669C2 (en) * 2003-10-01 2005-10-20 Открытое акционерное общество "Ракетно-космическая корпорация "Энергия" им. С.П. Королева" Method of measuring level of dielectric matter
RU2262668C2 (en) * 2003-10-01 2005-10-20 Открытое акционерное общество "Ракетно-космическая корпороация "Энергия" им. С.П. Королева" Device for measuring level of dielectric matter
US7891243B2 (en) * 2005-11-30 2011-02-22 SIE Sensorik Industrie-Electronik GmbH Sensor for the contactless detection of the level of a liquid and adhering high-conductivity medium, especially blood, through a non-metal wall of a container
US8096178B2 (en) * 2005-07-07 2012-01-17 Endress + Hauser Gmbh + Co. Kg Apparatus for capacitive ascertaining and/or monitoring of fill level
RU2445584C1 (en) * 2010-12-03 2012-03-20 Федеральное государственное унитарное предприятие "Научно-производственное объединение автоматики имени академика Н.А. Семихатова" Dielectric substance level measuring device

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
RU2262669C2 (en) * 2003-10-01 2005-10-20 Открытое акционерное общество "Ракетно-космическая корпорация "Энергия" им. С.П. Королева" Method of measuring level of dielectric matter
RU2262668C2 (en) * 2003-10-01 2005-10-20 Открытое акционерное общество "Ракетно-космическая корпороация "Энергия" им. С.П. Королева" Device for measuring level of dielectric matter
US8096178B2 (en) * 2005-07-07 2012-01-17 Endress + Hauser Gmbh + Co. Kg Apparatus for capacitive ascertaining and/or monitoring of fill level
US7891243B2 (en) * 2005-11-30 2011-02-22 SIE Sensorik Industrie-Electronik GmbH Sensor for the contactless detection of the level of a liquid and adhering high-conductivity medium, especially blood, through a non-metal wall of a container
RU2445584C1 (en) * 2010-12-03 2012-03-20 Федеральное государственное унитарное предприятие "Научно-производственное объединение автоматики имени академика Н.А. Семихатова" Dielectric substance level measuring device

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