RU2209421C2 - Facility measuring conduction of liquid media - Google Patents

Abstract

FIELD: measurement technology. SUBSTANCE: facility includes generator 1 of electric oscillations connected with output to first leads-out of communication elements 2 and 3, lead-out b of detector 13 of asynchronous mode. Communication element 2 is connected with second lead-out to second input of measurement circuit 6 which inductance is measurement winding 9 and with first input connected to first lead-out of HF amplifier 4 that is connected with second output to detector 13 of asynchronous mode. Communication element 3 is connected with second lead-out to second input of comparison circuit 7 which inductance is compensation winding 10 and with first input connected to first output of HF amplifier 5 which is connected with second output to input d of detector 13 of asynchronous mode connected with input a, outputs e and f correspondingly to fourth output, first and second inputs of control unit 14 coupled with third output to input controlling amplitude of generator 1. Control unit 14 is connected with first output to input of controllable element 15 connected with second output to input of meter 16 and element 15 is connected to compensation winding 11. EFFECT: enhanced sensitivity of measurement converter due to amplification of measurement signal at stage of primary conversion of measured value to information signal. 3 dwg

Description

 The invention relates to the field of measuring equipment and can be used in physicochemical analysis of the properties of materials according to their electrical conductivity, and can also be used to monitor the state of liquid or pulp-like technological environments of chemical industries.

 A device for measuring the electrical conductivity of liquid media. A known measuring transducer of conductivity of solutions contains a pumping frequency generator and two series-connected circuits, one of which is connected to a capacitive sensor. The voltages taken from the circuits are detected and compared [1].

 The disadvantage of the solution conductivity meter is the use of a capacitive sensor, which in conditions of contaminated media differs little in accuracy from a contact two-electrode sensor. In addition, the capacitive sensor in the submersible design is practically not used due to the very small electrolytic constant.

 The closest in technical essence (prototype) to the proposed invention is a device for measuring electrical conductivity, containing measuring and comparative circuits connected through a switch to a high-frequency amplifier, forming a self-oscillator, the output of which through an amplitude detector, a first amplifier and a controlled element is connected to the comparative circuit and a meter, a phase detector and a second amplifier, and the first input of the phase detector is connected to the second input of the switch, and the second input of the phases the second detector is connected to the output of the first amplifier [2].

 The disadvantage of the described device is the low sensitivity of the measurements, due to the use of the linear mode of the primary conversion of the measured value into an information signal, which does not allow amplifying the signal at this stage of the transformation.

 The purpose of the invention is to increase the sensitivity of the measuring transducer.

 The essence of the invention lies in the fact that in the device for measuring the electrical conductivity of liquid media containing measuring and comparative circuits, connected in turn to a high-frequency amplifier and forming an oscillator, a controlled element connected to a comparative circuit and meter, an electric oscillation generator is additionally introduced, the output connected to the first output of the first communication element, the first output of the second communication element, the second input of the asynchronous mode detector, and the amplitude control input connected to the third output of the control unit, the second output of the first communication element is connected to the input of the first high-frequency amplifier, the second output of the second communication element is connected to the input of the second high-frequency amplifier, the first output connected to the first input of the comparative oscillating circuit, the second output connected to the fourth input asynchronous mode detector, the first input of which is connected to the fourth output of the control unit, the third input connected to the second output of the first high-frequency amplifier from, and the first and second outputs connected respectively to the first and second inputs of the control unit, the first output connected to the input of the controlled element, and the second output connected to the meter, the compensation winding is connected to the controlled element, the measuring and comparative windings are respectively the inductance of the measuring circuits.

 The technical result is to increase the sensitivity of the measuring transducer by amplifying the measuring signal at the stage of primary conversion of the measured value into an information signal.

 The amplification of the measuring signal at the initial stage of conversion (increasing the efficiency of transformations [4]) is carried out through the use of a transient mode of coupled oscillations (out of synchronism). This makes it possible to use the bifurcation mode as the operating mode, which implements a transition through the boundary of stability loss in the oscillatory system and is highly nonlinear, which provides signal amplification at the stage of the primary transformation of the measured quantity.

 The invention is illustrated by the drawing, in which Fig. 1 shows a block diagram of a device for measuring the electrical conductivity of liquid media, and Fig. 3 is a timing diagram of an asynchronous mode detector and a control unit.

 A device for measuring the electrical conductivity of liquid media contains (see Fig. 1) an oscillation generator 1, connected to the first output of the communication element 2, the first output of the communication element 3, input b of the asynchronous mode detector 13. Communication element 2 is connected to the second input by a second output measuring circuit 6, the oscillatory circuit of which contains the measuring winding 9 of the sensor 8, and the first input connected to the first output of the first high-frequency amplifier 4, which is connected to the input from the detector asynchronously by the second output th mode 13. The communication element 3 is connected by a second output to the second input of the comparative circuit 7, the oscillatory circuit of which contains the comparative winding 10 of the sensor 8, and the first input is connected to the first output of the second high-frequency amplifier 5, which is connected to the input d of the asynchronous mode detector by the second output 13. The high-frequency amplifier 4 and the measuring circuit 6 form an oscillator 17, as well as the high-frequency amplifier 5 and a comparative circuit 7 form an oscillator 18. The synchronous mode detector is connected to input a, outputs e and f n, respectively, with the fourth output, the first and second inputs of the control unit 14. The control unit 14 of the third output k is connected to the amplitude control input of the electric oscillation generator 1, the first output g is connected to the input of the controlled element 15, and the second output h is connected to the input of the meter 16. Controlled element 15 is connected to the compensation winding 11 of the sensor 8.

 In FIG. 2 is a structural diagram of an asynchronous mode detector. The signals supplied to the input b, c, d with the help of voltage comparators Kl, K2, K3 are converted into logic levels, which are fed to certain inputs of the triggers T1 and T2, with a positive half-wave corresponding to a logical unit, negative to a logical zero. Input b receives a signal from a synchronizing generator, and input c and d from synchronized oscillators. In synchronous mode, in-phase oscillations are observed (the phase difference modulo does not exceed π) of a synchronizing generator with a self-oscillator. This corresponds to the presence of a logical unit at the direct outputs of the triggers T1 and T2. At the moment of exit from synchronism, the system goes into the region of antiphase oscillations (phase difference is greater than π), which corresponds to a change in the state of triggers T1 and T2. In the event that the oscillator connected to input c is the first to go out of synchronism, the logical unit appears at output e, otherwise, at output f. By supplying a control signal to input a, the asynchronous mode detector is initialized (a logic zero is set at outputs e and f).

 In addition, the drawing (see figure 3) shows the timing diagrams of the signals at the inputs a, b, c, d and outputs e, f of the asynchronous mode detector 13 and outputs g, h, k of the control unit 14. In this case, the signals at the outputs g, h, k of the control unit 14 are analog and their value is proportional to the conductivity of the controlled element 15, the reading of the meter 16, the oscillation amplitude of the electric oscillation generator 1, respectively, and the figure shows the ratio of the current reading to the maximum value of the output value. For signals at inputs a, b, c, d and outputs e, f of the asynchronous mode detector 13, the active level is a high level of signals. So the presence of a high level signal at input a transfers the asynchronous mode detector to its initial state, i.e. sets the signal low at outputs e, f. The signals at inputs b, c, d have a sinusoidal shape, the phase of which coincides with the currents of the electric oscillation generator 1, high-frequency amplifier 4, and high-frequency amplifier 5, respectively, in the drawing these signals are shown in the form of rectangular pulses for convenience, the high level of which corresponds to a positive half wave of a sinusoidal signal, and a low level - a negative half wave.

где t1_cc - время выхода из режима синхронных колебаний автогенератора 17;

показатель взаимодействия автогенератора 17 с генератором электрических колебаний 1, зависящий от измеряемой проводимости жидкости 12;

распределение амплитуд;

относительная расстройка частоты собственных колебаний автогенератора 17 и частоты собственных колебаний генератора 1, зависящая от измеряемой проводимости жидкости 12;
n₀ - частота собственных колебаний генератора 1;
n₁(G_x) - частота собственных колебаний автогенератора 17;
причем n₀ > n₁(G_x);
γ₁ - коэффициент, пропорциональный проводимости элемента связи 2;
B₁(G_x) - амплитуда колебаний автогенератора 17, зависящая от измеряемой проводимости жидкости 12.The device operates as follows: the high-frequency amplifier 4 and the measuring circuit 6, as well as the high-frequency amplifier 5 and the comparative circuit, form self-oscillators 17 and 18, respectively, while the inductance for the measuring circuit 6 is the coil 9 of the sensor 8, and the inductance of the comparative circuit 7 is winding 10 of the sensor 8. From the output of the generator of electrical oscillations 1, the voltage is supplied to the first output of the communication element 2 and the first output of the communication element 3, as well as to the input b of the asynchronous mode detector 11. Voltage On the first output of the coupling element 2, the measuring circuit 6 is connected to the electric oscillation generator 1 by creating an additional electric current in the oscillating circuit of the measuring circuit 6 proportional to the voltage at the output of the electric oscillation generator 1 and the electrical conductivity of the communication element 2. Similarly, the voltage at the first the output of the communication element 3 determines the connection of the comparative circuit 7 with the generator of electrical vibrations 1 by creating an additional th electric current in the resonant circuit of the comparative circuit 7 proportional to the magnitude of the output voltage of the generator electric oscillation element 1 and the electrical conductivity due 3. As the coupling elements 2 and 3 are applied electrical resistance elements (resistors). In the initial state, the outputs e, f of the detector of the asynchronous mode 13 are set to low levels, at the input of the amplitude control of the electric oscillation generator 1, a certain value of the control voltage value corresponds to the synchronous oscillation mode of the oscillator 18 with the electric oscillation generator 1. The measurement cycle begins with a change in the control signal at the input control the amplitude of the oscillations of the generator 1 to a value corresponding to the mode of asynchronous oscillations of the oscillator 18 with the generator 1, which causes There is a transient process associated with the output of the oscillators 17 and 18 out of synchronism with the generator 1. In this case, the phase difference between the oscillators 17 and 18 and the generator 1 changes upwards. The end of the transition process corresponds to the moment of the appearance of out-of-phase oscillations between the oscillators 17, 18 and the generator 1. The duration of the transition processes in the oscillators 17, 18 are described by the following relationships:

where t1 _cc is the time out of the mode of synchronous oscillations of the oscillator 17;

the interaction index of the oscillator 17 with the generator of electrical oscillations 1, depending on the measured conductivity of the liquid 12;

amplitude distribution;

relative detuning of the frequency of natural oscillations of the oscillator 17 and the frequency of natural oscillations of the generator 1, depending on the measured conductivity of the liquid 12;
n ₀ is the frequency of natural oscillations of the generator 1;
n ₁ (G _x ) is the frequency of natural oscillations of the oscillator 17;
where n ₀ > n ₁ (G _x );
γ ₁ - coefficient proportional to the conductivity of the communication element 2;
B ₁ (G _x ) is the oscillation amplitude of the oscillator 17, depending on the measured conductivity of the liquid 12.

G _x - the value of the measured conductivity of the liquid 12.

где t2_cc - время выхода из режима синхронных колебаний автогенератора 18;

показатель взаимодействия автогенератора 18 с генератором электрических колебаний 1, зависящая от проводимости управляемого элемента 15;

распределение амплитуд;

- относительная расстройка частоты собственных колебаний автогенератора 18 и частоты собственных колебаний генератора 1, зависящая от проводимости управляемого элемента 15;
n₂(G₀) - частота собственный колебаний автогенератора 18;
причем n₀<n₂(G₀);
γ₂ - коэффициент, пропорциональный проводимости элемента связи 3;
B₂(G₀) - амплитуда колебаний автогенератора 18, зависящая от проводимости управляемого элемента 15;
G₀ - проводимость управляемого элемента 15.

where t2 _cc is the time out of the mode of synchronous oscillations of the oscillator 18;

the rate of interaction of the oscillator 18 with the generator of electrical vibrations 1, depending on the conductivity of the controlled element 15;

amplitude distribution;

- relative detuning of the frequency of natural oscillations of the oscillator 18 and the frequency of natural oscillations of the generator 1, depending on the conductivity of the controlled element 15;
n ₂ (G ₀ ) is the natural frequency of the oscillator 18;
where n ₀ <n ₂ (G ₀ );
γ ₂ - coefficient proportional to the conductivity of the coupling element 3;
B ₂ (G ₀ ) is the oscillation amplitude of the oscillator 18, depending on the conductivity of the controlled element 15;
G ₀ - conductivity of the controlled element 15.

или
G₀=F(G_X), (4)
где F(G_x) - функциональная зависимость электрической проводимости управляемого элемента 16 от измеряемой электропроводности жидкой среды 12, полученная путем преобразований из (3).With an increase in the electrical conductivity of the liquid 12, the oscillation amplitude B ₁ (G _x ) of the oscillator 17 and the relative detuning ξ ₁ (G _x ) increase, i.e. the magnitude of the interaction λ ₁ (G _x ) will decrease, which, according to (1), will reduce the time to exit the synchronous oscillations of the oscillator 17 with the generator 1. This means that the first transition process will end in the oscillator 17, which will correspond to the appearance of a high level at the output e asynchronous mode detector 13. According to this signal (Fig. 3), at the output g of the control unit 14, a control signal is set that increases the conductivity of the controlled element 15, which reduces the interaction coefficient λ ₂ (G ₀ ). As a controlled element, a field effect transistor, an optocoupler, etc. can be used. At the same time, a signal proportional to the conductivity of the controlled element 15 is supplied to the input of the meter 16 from the output h of the control unit 14, and a control signal corresponding to the synchronous mode of oscillations of the oscillator 17 with the electric oscillation generator 1 is supplied to the control input of the oscillation amplitude of the electric oscillation generator 1, which synchronizes the fluctuations of the latter. Measurement cycles are repeated until the time intervals between exiting synchronous oscillations tl _cc (G _x ) and t2 _cc (G ₀ ) are equal. Moreover, from (1) and (2) it follows:

or
G ₀ = F (G _X ), (4)
where F (G _x ) is the functional dependence of the electrical conductivity of the controlled element 16 on the measured conductivity of the liquid medium 12, obtained by transformations from (3).

 Thus, the conductivity of the controlled element 15, and hence the value of the control signal and the signal value at the outputs g and h of the control unit 14, respectively, are functions of the electrical conductivity of the liquid medium 12.

где

коэффициент эффективности преобразования известного устройства для измерения электропроводности жидких сред.The gain when converting the measured value into an information signal at λ ₁ (G _x ) → 1 is expressed by the following dependence:

Where

conversion efficiency coefficient of a known device for measuring the electrical conductivity of liquid media.

раз больше, чем в известном устройстве [2]. Высокочувствительный режим измерений реализуется при λ₁(G_x)≈1, что обеспечивается при λ₂(G₀)_→λ₁(G_x) путем поддержания соответствующей амплитуды колебаний генератора 1.Thus, the conversion efficiency or gain in

times more than in the known device [2]. A highly sensitive measurement mode is realized at λ ₁ (G _x ) ≈1, which is ensured at λ ₂ (G ₀ ) _ → λ ₁ (G _x ) by maintaining the corresponding oscillation amplitude of generator 1.

и |ξ₂(G₀)|<|ξ₁₂|, где ξ₁₂ - относительная расстройка частот собственных свободных колебаний автогенераторов 17 и 18;
2) распределение амплитуд взаимно связанных автогенераторов выражается как [3]:

и

λ₁₂(G_x, G₀)- показатель взаимодействия автогенератора 17 с автогенератором 18;
γ₁₂- коэффициент паразитной связи между автогенератором 17 с автогенератором 18.Mutual synchronization of oscillators 17 and 18 in the presence of spurious communication between them is excluded for two reasons:
1) the frequency of the natural oscillations of the generator of electrical oscillations 1 lies between the frequencies of the natural free vibrations of the oscillators 17 and 18, i.e.

and | ξ ₂ (G ₀ ) | <| ξ ₁₂ |, where ξ ₁₂ is the relative detuning of the frequencies of natural free oscillations of the oscillators 17 and 18;
2) the distribution of the amplitudes of mutually coupled oscillators is expressed as [3]:

and

λ ₁₂ (G _x , G ₀ ) - an indicator of the interaction of the oscillator 17 with the oscillator 18;
γ ₁₂ - spurious coupling coefficient between the oscillator 17 with the oscillator 18.

 The oscillation amplitudes of the oscillators are chosen equal, and during the measurement they vary slightly relative to each other.

According to condition 1 and 2, the interaction index of the oscillators λ ₁₂ (G _x , G ₀ ) is close to zero, i.e. mutual synchronization of the oscillators 17 and 18 is impossible.

Sources of Information
1. Auth. St. USSR 144318, class G 01 N 27/02.

 2. Auth. St. USSR 1383184, class G O1 N 27/02.

 3. Sedalishchev V. N. Non-linear piezoresonance sensors. Textbook / AltSTU them. I.I. Polzunova - Barnaul: AltSTU, 1999, p. 33.

 4. Electrical measurements of non-electrical quantities. Ed. 5th, rev. and add. - L .: Energy, 1975, p. 103, 107.

Claims (1)

 A device for measuring the electrical conductivity of liquid media containing measuring and comparative circuits, connected in turn to a high-frequency amplifier, forming a self-oscillator, a controllable element connected to a comparative circuit and meter, characterized in that an electric oscillation generator is additionally introduced into it, connected to the first output by an output the first communication element, the first output of the second communication element, the second input of the asynchronous mode detector, and the control input connected to the third output the control unit, the second output of the first communication element is connected to the second input of the measuring circuit, the first input connected to the first output of the first high-frequency amplifier, which is connected to the third input of the asynchronous mode detector by the second output, the second output of the second communication element is connected to the second input of the comparative circuit, the first input connected to the first output of the second high-frequency amplifier, which is connected to the fourth input of the asynchronous mode detector by the second output, asynchronous detector mode, the first input is connected to the fourth output of the control unit, and the first and second outputs are connected respectively to the first and second inputs of the control unit, the first output connected to the input of the controlled element, and the second output connected to the meter, the compensation winding is connected to the controlled element, measuring and comparative windings are respectively the inductance of the measuring and comparative circuits.

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