RU2582496C1 - Device for measuring conductive liquids - Google Patents

Abstract

FIELD: measuring equipment.

SUBSTANCE: invention relates to electrical measurements and can be used to measure the electrical conductivity of liquids. Apparatus for measuring fluid conductivity comprises a generator of sinusoidal signals, with a frequency divider, the supply transformer with an excitation winding, a measuring transformer measuring coil, a closed coil of conductive test fluid, an analog-digital converter (ADC), the loop covering transformer excitation coil covering measuring transformer, the key is exemplary conductivity of known value, the control circuit, the computing device.

EFFECT: invention improves the accuracy of measurement of electrical conductivity of liquid media by eliminating the influence of errors due to the instability of the voltage and frequency of the power source, the magnetic permeability transformer cores, as well as eliminates the interference which may be a tip-in transformer cores.

1 cl, 4 dwg

Description

The invention relates to the field of electrical measurements and can be used to measure the electrical conductivity of liquid media for various purposes.

A device for measuring the electrical conductivity of a liquid, consisting of a sinusoidal signal generator, a supply transformer with an excitation winding, a measuring transformer with a measuring winding, a closed loop of an electrically conductive liquid under investigation, a phase-sensitive zero-organ, additional multi-sectional compensation windings with sections and keys, a conductivity store and circuits control, and the generator is connected to the excitation winding of the supply transformer, to the compensation sections bmotok connected through keys store conductances whose input is connected to the control circuit which is connected to a phase sensitive null body, whose input is connected to the measuring instrument transformer winding and the generator. The keys connecting the conductivity store with sections of the compensation windings are also connected to the control circuit [RF Utility Model Patent No. 122777, cl. G01R 27/22].

To implement this device, a high-accuracy class multi-bit conductivity store is required, and it is also impossible to achieve full compensation of magnetic flux in this device due to interference due to interference in the transformer windings.

The closest in technical essence to the present invention is a device for measuring the electrical conductivity of a liquid, consisting of a sinusoidal signal generator, a controlled voltage divider, a supply transformer with an excitation winding, a measuring transformer with a measuring winding, a closed loop of an electrically conductive liquid under study, an analog-to-digital converter (ADC) ), a coil covering an excitation transformer, a coil covering a measuring transformer, a key, a sample the known conductivity of a known magnitude, a control circuit, a computing device, the generator being connected through a controlled voltage divider to the excitation winding of the supply transformer, model conductivity of a known magnitude connected to additional turns through a key, the key connected to a control circuit that is also connected to a voltage divider, ADC and computing device. The measuring winding is connected to the ADC, which, in turn, is connected to a computing device [RF Utility Model Patent No. 143663, cl. G01R 27/22].

In this device, it is difficult to implement an accurate controlled voltage divider due to the instability of the elements of the divider, as well as the influence of the divider on the voltage of the generator.

The objective of the invention is to provide a device for measuring the electrical conductivity of a liquid with the following technical result: increasing the accuracy of measuring the electrical conductivity of liquid media by eliminating the influence of instability of the voltage divider by replacing it with a controlled frequency divider. A controlled frequency divider can be implemented with higher accuracy than a voltage divider, the division coefficient of which is affected by the stability of the elements of the voltage divider.

The essence of the invention lies in the fact that in a device containing a sinusoidal signal generator, a supply transformer with an excitation winding, a measuring transformer with a measuring winding, a closed loop from an electrically conductive test fluid, a control circuit, an exemplary conductivity of known magnitude, a key, additional turns covering the supply and measuring transformers, analog-to-digital converter (ADC) and computing device, a controlled frequency divider is introduced. In this case, the generator is connected via a controlled frequency divider of the alternating voltage to the excitation winding of the supply transformer, model conductivity of known magnitude is connected to the additional turns through the key, the key is connected to the control circuit, which is also connected to the alternating voltage frequency divider, ADC and computing device. The measuring winding is connected to the ADC, which, in turn, is connected to the computing device.

The invention improves the accuracy of measurements of the electrical conductivity of liquid media by eliminating the influence of instability of the voltage divider by replacing it with a controlled frequency divider. A controlled frequency divider can be implemented with higher accuracy than a voltage divider, the division coefficient of which is affected by the stability of the elements of the voltage divider.

In FIG. 1 shows a device for measuring the electrical conductivity of a liquid; FIG. 2 is a diagram illustrating a first clock cycle of the device; FIG. 3 is a diagram illustrating a second clock cycle of the device; FIG. 4 is a diagram illustrating a fourth clock cycle of an instrument.

The invention is illustrated in FIG. one.

A device for measuring the electrical conductivity of a liquid consists of a generator 1 of sinusoidal signals, a controlled frequency divider 2 of an alternating voltage, an excitation winding 3, a supply transformer 4, a closed coil 5 of an electrically conductive test fluid, a measuring transformer 6, a measuring winding 7, an analog-to-digital converter 8, additional turns 9, 10, key 11, model conductivity 12 of known magnitude, control circuit 13, computing device 14.

The device operates as follows.

The voltage from the generator 1 is supplied through a controlled AC frequency divider 2 to the field winding 3 of the supply transformer 4, and the voltage is transmitted either with a coefficient k = 1 or k <1 (U ₁ = kU _g ). In this case, in the liquid coil 5 and the additional coil 9, 10, the EMF is induced. The EMF acting in the liquid coil 5 causes a current, the value of which depends on the electrical conductivity of the liquid and which induces the voltage in the measuring winding 7 of the measuring transformer 6. The EMF acting in the additional coil 9, 10, depending on the position of the key 11, can create a current through the model conductivity 12 if the key is closed, or this current is zero if the key is open. The control circuit 13 allows you to select the operating mode of the AC frequency divider 2, the position of the switch 11, and also controls the operation of the ADC 8 and computing device 14. The measurement is carried out in three cycles at short intervals t → 0. In the first cycle, the division ratio of the controlled divider 2k = 1, the frequency of the alternating voltage after the divider 2 is equal to the frequency of the generator 1, the key 11 is open, and the current does not pass through it. The ADC 8 determines the voltage at the measuring winding 7 and its value is stored in the memory of the computing device 14. In the second cycle, the measurement is carried out at a dividing factor of the controlled divider 2k <1, the frequency on the exciting winding 3 is k times less than the frequency of the generator 1, key 11 is open . ADC 8 determines the voltage value on the measuring winding 7 and its value is stored in the memory of computing device 14. In the third step, the measurement is performed when the division ratio of the controlled divider 2k = 1, the frequency after divider 2 is equal to the frequency of the alternating voltage of generator 1, key 11 is closed, currents in the liquid turn 5 and in the additional turn 9, 10 have the same direction. The ADC 8 determines the voltage at the measuring winding 7 and its value is stored in the memory of the computing device 14. After three clock cycles, the control circuit 13 supplies a signal to the computing device 14, in which the value of the electrical conductivity of the liquid in the liquid coil 5 is determined.

 Consider the operation of the device.

1) The first beat. The division ratio of the controlled frequency divider of the AC voltage k = 1. The frequency of the alternating voltage after the divider is equal to the frequency of the generator, the key is open (Fig. 2):

system of equations describing the operation of the circuit:

where U _g is the voltage of the power source;

U ₂₁ - voltage in the measuring winding of the measuring transformer in the first cycle;

I ₁ - current in the exciting winding of the supply transformer;

I _x is the current in the liquid loop;

I _d - current in an additional turn;

L ₁ is the inductance of the exciting coil;

L _x is the inductance of the liquid loop;

L _d is the inductance of the additional turn;

M ₁₂ - mutual inductance of the exciting winding and the liquid coil;

M ₂₃ - mutual inductance of the measuring winding and the liquid coil;

M ₁₄ - mutual inductance of the exciting and additional coil;

M ₃₄ - mutual inductance of the measuring and additional coil;

G _x is the conductivity of the liquid loop;

G _d - model conductivity in an additional turn;

ω is the frequency of harmonic sinusoidal oscillations.

Solving the system of equations, we obtain that the output signal measured by a voltmeter is [Ivanov, VV, Latyshev, L.N. Analysis of methods and means of measuring the electrical conductivity of liquid media // Oil and Gas Business 2013 No. 2. - Ufa: USTU, 2013. - P. 93.]:

2) The second beat. The division ratio of the controlled frequency divider of the AC voltage k <1. The frequency of the alternating voltage on the exciting winding is k times less than the frequency of the generator, the key is open (Fig. 3):

system of equations describing the operation of the circuit:

where U ₂₂ is the voltage in the measuring winding of the measuring transformer in the second cycle.

Solving the system of equations, we obtain

3) The third measure. The division ratio of the controlled frequency divider of the AC voltage k = 1. The frequency of the alternating voltage after the divider is equal to the frequency of the generator, the key is closed (Fig. 4):

system of equations describing the operation of the circuit:

where U ₂₃ is the voltage in the measuring winding of the measuring transformer in the third cycle.

Solving the system of equations, we obtain the value of the output signal

Thus, we obtained a system of three independent equations

When measuring voltages U ₂₁ , U ₂₂ , U _23, an interference voltage U _p additionally acts, which occurs as a result of the action of external electromagnetic fields on the transformer cores. Taking into account the interference, the system of equations takes the form

such a system has a unique solution

k is the coefficient of the frequency divider

, значение измеряемой проводимости зависит только от класса точности выбранных элементов. Данное устройство позволяет повысить точность измерений электропроводности жидких сред за счет устранения влияния нестабильности делителя напряжения путем замены его управляемым делителем частоты. Управляемый делитель частоты может быть реализован с более высокой точностью, чем делитель напряжения, на коэффициент деления которого влияет стабильность элементов делителя напряжения.As can be seen from the expression $$Gx=G_d\frac{m}{k-\mathrm{one}},\text{(9)}$$

, the value of the measured conductivity depends only on the accuracy class of the selected elements. This device allows to increase the accuracy of measurements of the electrical conductivity of liquid media by eliminating the influence of instability of the voltage divider by replacing it with a controlled frequency divider. A controlled frequency divider can be implemented with higher accuracy than a voltage divider, the division coefficient of which is affected by the stability of the elements of the voltage divider.

Claims (1)

A device for measuring the electrical conductivity of a liquid, containing a sinusoidal signal generator, a supply transformer with an excitation winding, a measuring transformer with a measuring winding, a closed loop of an electrically conductive test liquid, covering the cores of both transformers, additional turns covering the supply and measuring transformers, to which an exemplary is connected via a key known conductivity, the key is connected to a control circuit that is connected to analog-digital the converter and the computing device, the measuring winding is connected to an analog-to-digital converter, which, in turn, is connected to the computing device, characterized in that the output of the generator is connected to a controlled AC frequency divider, the output of the AC voltage divider is connected to the excitation winding of the supply transformer , and the controlled input of the AC voltage divider is connected to the control circuit.

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