RU2115112C1 - Shf method determining concentration of electrolyte and gear for its realization - Google Patents

Abstract

FIELD: electrical engineering. SUBSTANCE: method determining concentration of electrolyte put into cell placed into circuit of controlled SHF generator includes change of frequency after equal time intervals and calculation of parameters of electrolyte by changing frequency. Cell is manufactured in the form of cylindrical cavity resonator in which electromagnetic oscillation of H₀₁₁ type is excited. Electrolyte is injected into specified volume of resonator, frequency of SHF generator is continuously tuned to own resonance frequency of oscillation of H₀₁₁ resonator. Amplitude of output signal of cell is measured on resonance frequency. When amplitude reaches normed threshold at which maximum sensitivity is observed injection of electrolyte is stopped and concentration of electrolyte is calculated by measured resonance frequency. Gear for realization of method has cell in circuit of controlled SHF generator, microprocessor, comparator, digital-to-analog converter, actuating mechanism controlling injection/discharge of electrolyte and pressure in cell made in the form of cylindrical cavity resonator. Output of it is connected to first input of comparator which second input is connected through digital-to-analog converter to first output of microprocessor which input is connected to output of comparator. Its second output is connected to input of controlled SHF generator and its third output is connected through actuating mechanism to controlling input of cell. Controlled SHF generator incorporates master generator and program-controlled frequency-setting circuit composed of varicap and short-circuited long line of variable length connected through multiplexer to higher digits of controlling input of controlled SHF generator which lower-order digits are connected through digital-to-analog converter to electrodes of varicap. EFFECT: increased sensitivity, expanded measurement range and functional capabilities of gear. 4 cl, 4 dwg

Description

 The proposed invention relates to physico-chemical research and can be used in chemical and other related industries.

 Known amplitude-frequency method for determining the concentration of electrolyte (see book. Lopatin B. A. High-frequency titration with multi-link cells. M.: Chemistry, 1980, S. 9-13), placed in a capacitive measuring cell (EIA) with n resonant links frequency-setting circuit of a high-frequency generator (HHF), and selection of a resonant frequency according to an amplitude-frequency characteristic, including a change in frequency and voltage at equal time intervals, calculation of electrolyte parameters at a variable frequency.

 The disadvantage of this method is the low accuracy and efficiency associated with the replacement of one EIA with another, not a wide measurement range, since each cell works only in its own range, a large methodological error due to the fact that the desired electrolyte characteristics, although found through the frequency, are by additional conversion of the amplitude-frequency characteristic, that is, in amplitude.

 The closest is a method for determining the concentration of electrolyte (see RF Patent, N 2011983, G 01 N 27/02, 1994, Bull. 8), placed in a multi-link cell of the frequency-setting circuit of a high-frequency generator, including changing the frequency at regular intervals, calculation of electrolyte parameters by changing frequency, changing cell geometry by sequentially connecting pairs of electrodes of a given geometry in various combinations in the frequency-setting circuit, determining the ratio of frequency changes to the current frequency value and determined the concentration of electrolyte in frequency from the smallest ratio.

 The disadvantages of this method are the relatively narrow range of conductivity measurements, as well as the extremely uneven distribution of the sensitivity of the output signal to a change in conductivity.

 A device for determining the concentration of electrolyte (see book. Lopatin B. A. High-frequency titration with multi-link cells. M: Chemistry, 1980, pp. 9-13), consisting of a high-frequency generator, the circuit of which includes a multi-link capacitive measuring cell .

 The disadvantage of this device is the low accuracy, limited measurement range, since each cell operates only in its own range, a sufficiently long time for one experiment, associated with the introduction of jumpers for sequential time switching of the electrodes of the multilink cell.

 The prototype is a device (see RF Patent, N 2011983, G 01 N 27/02, 1994, Bull. 8), consisting of a multi-link cell, a high-frequency generator, a bi-directional multiplexer and a microprocessor.

 The disadvantage of this device is the low and uneven sensitivity and a limited measurement range.

 The present invention is aimed at increasing sensitivity, expanding the measurement range and functionality.

The goal is achieved by:
in the method for determining the concentration of electrolyte placed in a cell included in the circuit of a controlled frequency generator, including changing the frequency at regular intervals, calculating the parameters of the electrolyte at a variable frequency, a microwave frequency generator is used as a controlled frequency generator, the cell is made in the form of a cylindrical cavity resonator in which electromagnetic oscillation of type H _{011 is} excited, the electrolyte is introduced into the predetermined volume of the resonator by constantly tuning the frequency of the controlled microwave - a frequency generator for the natural resonant frequency of the oscillation H _{011 of the} resonator, measure the amplitude of the output signal of the cell at the resonant frequency, when the amplitude reaches the normalized threshold value at which the maximum sensitivity is observed, the electrolyte inlet is stopped, and the desired electrolyte concentration is calculated from the measured resonant frequency;
in the method according to claim 1, a volume of electrolyte with a measured concentration is dosed;
in a device for determining the concentration of an electrolyte containing a cell in a controlled frequency generator circuit and a microprocessor, a controlled microwave frequency generator is used as a controlled frequency generator, an additional comparator, a digital-to-analog converter, an actuator for controlling the electrolyte inlet-outlet and pressure in the cell are introduced, which made in the form of a cylindrical volume resonator, the output of which is connected to the first input of the comparator, the second input of which is through digital-analog the converter is connected to the first output of the microprocessor, the input of which is connected to the output of the comparator, the second output to the input of the controlled microwave frequency generator, the second output to the input of the controlled microwave frequency generator, and the third output through the actuator to the control input of the cell;
in the device according to claim 3, the controlled microwave frequency generator includes a master oscillator and a program-controlled frequency-drive circuit consisting of a varicap and a shorted long line of variable length connected through the multiplexer to the upper bits of the control input of the controlled microwave frequency generator, the younger the discharges of which are connected to the varicap electrodes through a digital-to-analog converter.

The essence of the proposed method is as follows: the cell is made in the form of a cylindrical OR, in which electromagnetic oscillation of type H _{011 is} excited, the electrolyte is started into the given volume of the resonator, constantly tuning the frequency f of the controlled microwave frequency generator to its own resonant frequency of the OR oscillation, the amplitude U is measured _i output cell (amplitude proportional to the loaded Q of the output signal Q of the cylindrical PRs) at a resonant frequency when the amplitude value is normalized th threshold E _oj, where maximum sensitivity is observed, stop the electrolyte inlet and the measured resonance frequency is calculated desired concentration.

 In FIG. 1 and 2 are dependencies that explain the essence of the method.

где
h_rc=h_т/c - нормированный уровень электролита;
ε = ε_a/ε₀ - относительная диэлектрическая проницаемость электролита;
θ_γ - добротность, определяемая потерями энергии в проводящей среде;
Q_ст - потерями в металлической стенке ОР;
k₁, k₂, k₃, k₄ - числовые константы.A variable volume of electrolyte with electrical conductivity γ, functionally related to the concentration, is placed in the internal cavity of a cylindrical OR with a given geometry (Fig. 3). In the PR excite oscillation type H ₀₁₁ . The resonance frequency f and the Q factor of the loaded system (cylindrical OR with a variable volume of electrolyte) act as information parameters of the OR. Dependences f and Q for the most high-Q oscillations H ₀₁₁ for the case of a horizontal electrolyte level h _t :

Where
h _rc = h _t / c is the normalized electrolyte level;
ε = ε _a / ε ₀ is the relative dielectric constant of the electrolyte;
θ _γ is the quality factor determined by the energy loss in a conducting medium;
Q _article - losses in the metal wall of the OP;
k ₁ , k ₂ , k ₃ , k ₄ are numerical constants.

зависимости чувствительности добротности (или амплитуды выходного сигнала ОР U_i = Q) от величины γ при разных величинах h_rc. Анализ графиков фиг. 1 и 2 показывает, что максимум чувствительности (точки перегиба кривых Q = F₂(γ) ) в диапазоне от 10^-4 см/м до 1 см/м приходятся на один уровень Q= Q_Smax, который лишь при γ <10^-4 см/м функционально зависит от γ (кривая Q_Smax=F₃ (γ), см. идентичную кривую S_max=k•F₃ (γ) на фиг. 2).In FIG. Figure 1 shows the calculated family of dependences of the Q factor Q OR of the electrolyte conductivity γ for various values of the electrolyte level (for ε = 3, the nature of the dependences does not change when changing, for example, for aqueous solutions ε = 80, but only the value Q changes), and in Fig. 2

the dependence of the quality factor (or the amplitude of the output signal OP U _i = Q) on the value of γ for different values of h _rc . The graph analysis of FIG. 1 and 2 shows that the sensitivity maximum (the inflection point of curves Q = F ₂ (γ)) in the range of 10 ^-4 cm / m to 1 cm / m fall on one level Q = Q _Smax, which is only for γ <10 ^{- 4} cm / m functionally depends on γ (curve Q _Smax = F ₃ (γ), see the identical curve S _max = k • F ₃ (γ) in Fig. 2).

(1)
можно получить аналитическую зависимость

и, также, что главное, ей обратную
γ = F $\genfrac{}{}{0ex}{}{\text{-1}}{\text{5}}$ (f). (5)
Алгоритм определения функции (5): в точках пересечения кривых F₂(h_rc,ε,γ) (2) (фиг. 1) с кривой Q_Smax=F₃ (γ) каждому уровню h_rc ставится в соответствие электропроводность γ (например, γ = 10^-2 см/м _→ h_rc= 0,02) ) далее, используя зависимость f = F₁(h_rc,ε) (1), каждому уровню h_rc ставится в соответствие частота, таким образом, каждой частоте f_i соответствует своя электропроводность γ_i при условии постоянства ε. . При условии постоянства величины ε электролита величину γ рассчитывают по f генератора СВЧ.Thus, the algorithm that describes the proposed method, at maximum and constancy of sensitivity in the specified wide range, is as follows: continuously supplying electrolyte to a cylindrical OR, constantly supporting by changing the frequency of the microwave OR generator in resonance, measure Q and when it reaches Q _Smax = F ₃ (γ) (i.e., when the amplitude of the output signal OP reaches the value of the normalized threshold proportional to Q _Smax ), the resonance frequency f is measured. Knowing the dependence (see Fig. 1)

(1)
can get analytical dependence

and also, most importantly, the opposite
γ = F $\genfrac{}{}{0ex}{}{\text{-1}}{\text{5}}$ (f). (5)
Algorithm for determining function (5): at the points of intersection of the curves F ₂ (h _rc , ε, γ) (2) (Fig. 1) with the curve Q _Smax = F ₃ (γ), each level h _rc corresponds to the electrical conductivity γ (for example , γ = 10 ^-2 cm / m _ → h _rc = 0.02)) then, using the dependence f = F ₁ (h _rc , ε) (1), each level h _rc is associated with a frequency, thus, each frequency f _i corresponds to its own electrical conductivity γ _i provided that ε is constant. . Given the constancy of ε of electrolyte, γ is calculated from f of the microwave generator.

A variant of the proposed method is the following: using dependencies (5) and (1), it is possible to form a proportional dose volume with the known (or measured by the proposed method) γ (concentration) electrolyte practically inversely to it (γ): the electrolyte inlet into the OP continues until the output amplitude is equal signal to the normalized threshold, while the natural resonant frequency of the loaded system is maintained equal to the frequency of the controlled microwave frequency generator and is determined by the function f = F ₅ (γ), in this case the conductivity meter serves t device for the direct conversion of the value of γ in the dose volume using for automatic titration.

 In FIG. 3 shows a structural diagram of a device that implements the proposed method, and in FIG. 4 is a diagram of the construction of a software-controlled frequency generator.

 The device consists of a cylindrical OP 1 with a variable volume of electrolyte, included at the output of the microwave generator 2 with a program-controlled frequency-setting circuit 3, organizing a controlled microwave frequency generator, microprocessor 4, digital-to-analog converter 5 (DAC), comparator 6, and an actuator 7 for controlling the inlet-outlet of the electrolyte and the pressure in the cell, made in the form of a cylindrical OR.

 The frequency-setting circuit 3 contains a shorted long line 8, varicap 9, multiplexer 10 for switching line 8 along the high-order bits of microprocessor 4 and DAC 11 for converting the low-order bits of microprocessor 4 to the controlled voltage of varicap 9.

через мультиплексор 10 изменяют длину закороченной длинной линии 8 (полосковой длинной линии), перестраивая генератор 2 по поддиапазонам. Младшие разряды кода

через ЦАП 11 преобразуются в управляющее напряжение, воздействующее на варикап 9, перестраивая плавно генератор 2 внутри поддиапазона. Длинная линия 8 с переменной длиной и варикап 9 включены в частотно-задающую цепь генератора 2, образуя эквивалентные L_i и C_i, соответственно шаг дискретности определяется кодом, изменяющимся в пределах {N_min,N_max} с дискретой ΔN = 1, соответствующим { ω_н,ω_в} частотам диапазона с нормой Δω. Исходя из погрешности изменения частоты ε_ω = Δω/ω и кода ε_N = ΔN/N_min, вычисляются значения
N_max = ω_в/Δω и N_min = ω_н/Δω ,
т.е. код N_i= ω_i/Δω. Текущая частота ω_i генератора 2 зависит от параметров L_i, C_i частотно-задающей цепи 3:

Задавая погрешность дискретизации частоты ε_ω = Δω/ω₀, код N_i вычисляется как
N_i = (i•ε_ω)^-1. (6б)
Микропроцессор 4 управляет частотой генератора 2 через код N_i и погрешность ε_ω, изменяет напряжение на ЦАП 5 для регистрации (или задания) концентрации (объема, удельной электропроводности) по измеряемой частоте резонанса, а также служит для расчета, коррекции и колировки идентифицируемых характеристик электролита.A change in the frequency f (ω = 2πf) occurs, for example, according to a linear law in the range from the lower ω _n to ω _{in the} upper frequency. The generator 2 is controlled by the N _i code of the microprocessor 4. The high order bits of the code

through the multiplexer 10 change the length of the shorted long line 8 (strip long line), rearranging the generator 2 on the subbands. Low-order bits of code

through the DAC 11 are converted into a control voltage acting on the varicap 9, smoothly rebuilding the generator 2 within the subband. A long line 8 with a variable length and a varicap 9 are included in the frequency-setting circuit of the generator 2, forming equivalent L _i and C _i , respectively, the step of discreteness is determined by a code that varies within {N _min , N _max } with a discrete ΔN = 1 corresponding to { ω _n , ω _in } the frequencies of the range with the norm Δω. Based on the error in the change in the frequency ε _ω = Δω / ω and the code ε _N = ΔN / N _min , the values are calculated
N _max = ω _in / Δω and N _min = ω _n / Δω,
those. code N _i = ω _i / Δω. The current frequency ω _{i of the} generator 2 depends on the parameters L _i , C _{i of the} frequency-setting circuit 3:

Setting the sampling error of the frequency ε _ω = Δω / ω ₀ , the code N _{i is} calculated as
N _i = (i • ε _ω ) ^-1 . (6b)
The microprocessor 4 controls the frequency of the generator 2 through the code N _i and the error ε _ω , changes the voltage on the DAC 5 to record (or set) the concentration (volume, electrical conductivity) by the measured resonance frequency, and also serves to calculate, correct and color the identifiable characteristics of the electrolyte .

Компаратор 6 выполняет функцию амплитудного детектора и сравнивает с уставкой E_oj детектируемое напряжение U_i на выходе ячейки 1. При равенстве U_i= E_oj на выходе компаратора 6 формируется импульс управления τ_i микропроцессором 4 по условию:

В момент неравенства напряжений низкий потенциал логического нуля инициирует изменение кода N_i микропроцессора 4 по программе, а при появлении потенциала высокого уровня логической единицы в момент равенства напряжений интерфейсные программы прерываются и в микропроцессоре регистрируются коды N_i, N_j для расчета искомых характеристик. После идентификации параметров исследуемого электролита по соответствующим программам осуществляется j-ый цикл измерения. Каждый цикл измерения содержит i-циклов взвешивания при фиксации кода N_j, а при задании кода N_i измерение i-ого цикла включает j-циклов взвешивания.DAC 5 is used to convert the code N _j to the threshold voltage E _oj for setting (or measuring) the normalized volume (concentration) of electrolyte in OP 1. DAC 5 is included with other units of the device in servo feedback and organizes a sensor analog-to-digital converter. At the output of the DAC 5 from the code N _j and the reference voltage, a controlled setpoint voltage is generated by the microprocessor 4

The comparator 6 performs the function of an amplitude detector and compares with the setpoint E _{oj the} detected voltage U _i at the output of cell 1. If U _i = E _oj , the control pulse τ _i is generated by the microprocessor 4 by the condition:

At the moment of voltage inequality, the low potential of a logical zero initiates a change in the code N _{i of the} microprocessor 4 according to the program, and when a potential of a high level of a logical unit appears at the moment of voltage equality, the interface programs are interrupted and the codes N _i , N _j are recorded in the microprocessor to calculate the desired characteristics. After identifying the parameters of the studied electrolyte according to the appropriate programs, the j-th measurement cycle is carried out. Each measurement cycle contains i-weighing cycles when fixing the code N _j , and when setting the code N _{i, the} measurement of the i-th cycle includes j-weighing cycles.

 Consider the operation of the device as an example of the first mode.

In the initial state, in the jth cycle, the codes of the setpoint N _j and frequency control ω _{i of the} generator 2 - N _i are generated at the outputs of the microprocessor 4.

In the diagnostic mode, to monitor the state of the functioning of health, the frequency ω ₀ for an empty cell is determined (set) by normalizing the values of N _i in the i-th cycles and N _j in the j-th cycles. If necessary, the initial values (N _i , N _j , ω ₀ ) are calibrated during calibration on solutions with normalized characteristics at given volumes v _{j of} filling cell 1.

In calibration mode, the obtained values of ω _0ij frequencies are stored in the RAM of microprocessor 4 and are accepted as normalized values for the ij-th measurement cycle.

In the jth measurement cycle, OR 1 is filled with the v _jth volume of the studied electrolyte solution with the corresponding concentration value. The microprocessor 4 controls the frequency ω _{i of the} generator 2 according to a linear law with the code N _i . The frequency of generator 2 sequentially changes from ω _iв to the i-th frequency value corresponding to the resonance of the studied electrolyte with C _j -th concentration (with v _j -th filling volume of cell 1). The frequency sampling step Δω is determined by a single bit of code N _i with an error ε _ω .
At the output of OP 1, a voltage of amplitude U _{i is} detected. When U _i reaches a value equal to the set voltage E _oj , the comparator switches to the state of the logical unit, the interface programs are interrupted, and the code N _{im is} registered in the RAM of the microprocessor 4, which corresponds to the tuning frequency of the cylindrical OP. In this case, for the jth measurement cycle, the desired electrolyte parameters are calculated.

Q_пуст - добротность пустого ОР; α - коэффициент пропорциональности.The value of the setpoint voltage E _oj is determined during the calibration process from the relation

Q is _empty - quality factor of empty OR; α is the coefficient of proportionality.

.The setpoint code N _j from (7) and (9) is

.

и связан с кодом (см. (6.б))

Нормированные параметры в микропроцессоре 4 функционально взаимосвязаны и рассчитываются по соответствующим алгоритмам.When three frequency reports fall into the passband of an empty OR, the setpoint code is N _j through the error ε _ω taking into account ε _ω = Δω / ω ₀ ; Δω _nn = ω ₀ / Q is _empty = ω ₀ / 2Q _Smax = ω ₀ • α / 2E _0j and (7) has the form

and associated with the code (see (6.b))

The normalized parameters in microprocessor 4 are functionally interconnected and calculated according to the corresponding algorithms.

 The actuator 7, controlled by the microprocessor 4, performs the inlet-outlet of the electrolyte and creates a vacuum in the cell at the time of inlet and overpressure at the time of release of the electrolyte.

The effectiveness of the proposed invention is expressed:
1. in expanding the range of measurements. In the prototype, it is equal to one order of change in electrical conductivity, for the proposed technical solution, taking into account theoretical and experimental studies, - three order of change of γ;
2. in increasing the sensitivity due to the higher quality factor of the loaded system. The quality factor of a cylindrical OR as a system with dispersed parameters is about two orders of magnitude higher than the quality factor of an oscillating system with lumped prototype parameters;
3. in increasing functionality - the ability to dispense electrolyte according to known or measured electrical conductivity, along with measuring concentration, as in the prototype;
4. the constancy of the sensitivity of the output signal to a change in the measured value by several orders of magnitude (Fig. 2).

The method was tested on an experimental setup (Fig. 3) containing a cylindrical OR made of copper:
Diameter OR mm - 70
Height OR mm - 100
Resonant oscillation frequency of empty OR, GHz - 3.7
As a conductive medium, model solutions of KaCl were used. The measurements consisted in measuring the resonant frequency and quality factor of the loaded system at various levels and conductivities of the electrolyte:
Q = f _res / Δf 0.707.
The experiment showed that the constancy and maximum sensitivity, for given cell sizes, falls in the range from 10 ^-4 cm / m to 10 ^-1 cm / m (Fig. 1). The discrepancy with the theoretical measurement range is explained by the dispersion of the electrical conductivity of aqueous solutions and the difficulty of realizing very small levels (less than 0.01 • s).

 Actual graphs compared to FIG. 1 completely coincide in character, but the maximum figure of merit of an empty OR is practically 1.7 - 1.9 times less due to energy losses for removing it from the resonator.

 Thus, due to the proposed set of actions and the device that implements them, in contrast to the known technical solutions, the range of measuring the concentration of electrolytes is significantly expanded with a constant and maximum sensitivity of the output signal to the measured concentration and the functionality is expanded by dosing.

Claims (4)

1. The method of determining the concentration of electrolyte placed in a cell included in the circuit of a controlled frequency generator, including changing the frequency at regular intervals, calculating the parameters of the electrolyte at a variable frequency, characterized in that a microwave frequency generator is used as a controlled frequency generator, the cell is a cylindrical cavity resonator, wherein the electromagnetic wave is excited type H ₀₁₁ begin to release the electrolyte in a predetermined volume of the cavity is constantly adjusting ca Toth managed microwave frequency oscillator to its own resonant frequency vibrations H ₀₁₁ resonator alter cell output signal amplitude at the resonance frequency reaches the value of the normalized threshold amplitude at which there is maximum sensitivity cease electrolyte output and the measured resonance frequency is calculated desired electrolyte concentration.  2. The method according to p. 1, characterized in that the volume of electrolyte is dosed with the measured concentration.  3. A device for determining the concentration of electrolyte containing a cell in the circuit of a controlled frequency generator and a microprocessor, characterized in that a controlled microwave frequency generator is used as a controlled frequency generator, an additional comparator, a digital-to-analog converter, an actuator for controlling the electrolyte inlet-outlet and pressure in the cell, which is made in the form of a cylindrical volume resonator, the output of which is connected to the first input of the comparator, the second input of which is The digital-to-analog converter is connected to the first output of the microprocess, the input of which is connected to the output of the comparator, the second output to the input of the controlled microwave frequency generator, and the third output through the actuator to the control input of the cell.  4. The device according to claim 3, characterized in that the controlled microwave frequency generator includes a master oscillator and a program-controlled frequency-master circuit, consisting of a varicap and a shorted line of variable length connected through a multiplexer to the senior bits of the controlled input of the controlled A microwave frequency generator, the least significant bits of which are connected to the varicap electrodes through a digital-to-analog converter.

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