RU35895U1 - A device for measuring the electrical conductivity of a liquid in conditions of high pollution - Google Patents

Description

A device for measuring the electrical conductivity of a liquid in conditions of high pollution

The utility model relates to the measurement of the electrophysical parameters of liquids by measuring electrical conductivity and can be used in environmental monitoring systems for water basins, oceanological research, experimental hydrodynamics and other fields of technology where it is necessary to control the parameters of flows of electrically conductive liquid media.

A device is known for measuring the parameters of an electrically conductive liquid medium (conductometer) comprising a contact measuring cell connected to a measuring circuit including a high-frequency generator, a bridge circuit, a differential detector, a DC amplifier and a recording device (see ed. Certificate of the USSR No. 1223115, IPC G01N 27/06, 1984). The device also contains a calibrator, and the cell is equipped with an additional electrode. The presence of a calibrator and an additional electrode allows you to check the device before taking measurements. However, during the measurement process, the conversion coefficient of the device is not controlled, which significantly reduces the reliability of the results, in particular, due to contamination of the surface of the microelectrode.

A conductometer is also known, which contains a contact two-electrode measuring cell connected to a measuring circuit including an adjustable amplifier (see ed. Certificate of the USSR No. 851241, IPC G01 N 27/02, 1979). The conductivity meter also contains supply and measuring transformers placed in a dielectric housing made in the form of a drop-shaped torus with an opening for the flow of the test fluid, an AC voltage source connected to a winding located on the toroidal core of the supply transformer, and a detector connected to the winding located on the toroidal core of the measuring transformer. In addition to this, the conductivity meter also contains the first and second band

r about

t 3 h 45

IPC GO IN 27/02

filters, the inputs of which are connected respectively to the outputs of the detector and the adjustable amplifier, and the outputs are connected to the inputs of the comparison circuit, the output of which through the integrator is connected to the control input of the adjustable amplifier.

In the conductometer, as a result of comparing the signals at the outputs of the bandpass filters and controlling the transfer coefficient of the adjustable amplifier, the conversion coefficients of the measurement channel with a contact measuring cell and the channel with a non-contact two-transformer converter are automatically maintained, which provides conductivity measurement with small errors in dynamic mode and high spatial resolution. This conductivity meter also contains a low-pass filter, a high-pass filter and an adder. The summation of the signals of the two channels allows you to measure the conductivity of the liquid in a wide frequency range. In a conductometer, high accuracy in measuring small-scale conductivity pulsations is ensured provided that high metrological characteristics of the non-contact (low-frequency) channel are maintained. However, under real operating conditions, especially in heavily polluted environments and with a long measurement time, contamination of the hole for the liquid to flow through chips, small fish, algae, etc. At the same time, the results of the conversion of both the absolute value of the measured conductivity and its spectral characteristics are distorted at the detector output, which leads to a change in the transfer coefficient of the adjustable amplifier and inaccurate measurement results of the small-scale structure of the conduction field.

The proposed utility model was created to increase the reliability of the results of measuring the specific electrical conductivity of the liquid by eliminating the registration of the measurement results in case of contamination of the hole for the flow of the studied electrically conductive liquid.

The essence of the utility model consists in the fact that in a conductometer containing a contact measuring cell connected to a measuring circuit including an adjustable amplifier, supply and measuring transformers placed in a dielectric housing made in the form of a drop-shaped torus with an opening for the flow of the studied liquid, the source is variable voltage connected to the winding located on the toroidal core of the supply transformer, a detector connected to the winding located on the toroid the main core of the measuring transformer, the first and second bandpass filters, the inputs of which are connected to the outputs of the detector and the adjustable amplifier, respectively, and the outputs are connected respectively to the first and second inputs of the comparison circuit, the output of which through the integrator is connected to the control input of the adjustable amplifier in the diffuser part of the hole for a liquid electrode is located an annular electrode, a nerve and a second amplifier are introduced into the device, the first inputs of which are connected to the annular electrode by means of respectively, the first and second conductors, covering the toroidal core of the supply transformer, as well as a series-connected adder, synchronous detector, absolute value detector, threshold block and clogging indicator, a differential amplifier and a comparator connected in series, the output of which is connected to the control input of a synchronous detector, as well as a gated unit and inverter, while the outputs of the first and second amplifiers are connected respectively to the first and second inputs of the adder and differential For the amplifier, the second inputs of the first and second amplifiers and the comparator are connected to a bus of zero potential, to which a conductometer housing made of electrically conductive material is connected, and the output of the threshold block through an inverter is connected to the control input of the gated block connected to the output of the measuring circuit. In this case, as a result of a change in the design of the dielectric housing and the introduction of new electronic units and electrical connections, the presence of a foreign object in the confuser part of the hole for fluid flow is detected, which leads to a violation of the conductometer parameters, the output of the measuring circuit is disconnected from the recording device and the clogging fact is displayed, which leads to exclusion of registration of false results.

The essence of the proposed utility model is illustrated by drawings, which depict:

in FIG. 1 - diagram of the proposed conductometer;

in FIG. 2 - design of the part of the device located directly in the studied stream;

in FIG. 3 is an example of performing a comparison scheme;

in FIG. 4 is a design variant of a dielectric housing;

in FIG. 5 - a variant of the construction of the output circuit of the conductometer.

The proposed conductometer contains a contact measuring cell (ID) 1 connected to the measuring circuit (IC) 2, an adjustable amplifier (RU) 3 with a controlled (adjustable) transmission coefficient, a source (East) 4 of an alternating sinusoidal voltage of low or ultrasonic frequency, connected to the primary a winding 5 located on the ferromagnetic toroidal core 6 of the supply transformer 7, a detector (D) 8 connected to the output winding 9 located on the ferromagnetic toroidal core 10 of the measuring transformer Ator 11 (FIG. 1). The conductometer also contains identical first and second bandpass filters (PF) 12 and 13, the inputs of which are connected to the outputs of the detector 8 and amplifier 3, respectively, and the outputs are connected respectively to the first and second inputs of the circuit (CC) 14

comparison, the output of which through the integrator (J) 15 is connected to the control input of the amplifier 3. In the dielectric housing 16, made in the form of a drop-shaped torus, the supply and measuring transformers 7 and 11 are placed coaxially to this housing (Fig. 2). In the diffuser (expanding) part of the hole 17 for the flow of the test fluid, an annular electrode 18 is arranged coaxially with this hole, made primarily of a material resistant to aggressive media, such as titanium. The electrode 18 is advantageously positioned so that the resistance of the sections of the bulk electrolytic conductor formed when the housing 16 is immersed in the test liquid to the right and left of the electrode 18 is approximately equal to each other.

The contact measuring cell 1 is made, in particular, in the form of a conical protrusion 19, the axis of which is parallel to the axis of the torus. A microelectrode 20 is located at the top of the protrusion 19, and an electrode 21 is located on the generatrix. The electrode 20 is made mainly of platinum wire to reduce the error due to polarization phenomena. The ratio of the areas of the electrodes 21 and 20 is predominantly more than 100 in order to almost completely eliminate the polarization of the large electrode 21, which makes it possible to use a less expensive and scarce metal, such as titanium or stainless steel, as an electrode material 21 and concentrate the measurement volume in a small area adjacent to electrode 20. Cell 1 may be located separately from the housing 16 (Fig. 4).

The conductometer contains two amplifiers 22 and 23 with a high input impedance (Fig. 1). At least one of these amplifiers must have gain control to equalize the signals at the outputs of the amplifiers under normal conditions. The first inputs of the amplifiers 22 and 23 are connected to the electrode 18 using the conductors 24 and 25. The conductors 24 and 25 enclose the core 6 of the transformer 7. The conductor 24 can also surround the core 10 (see Fig. 4), which with high input impedance of the amplifiers 22 and 23 does not affect the operation of the device. The conductometer contains a series-connected adder (X) 26, a synchronous detector (SD) 27, an absolute value detector (D) 28, a threshold block (BOP) 29 and a blocking indicator (Ind) 30, and a differential amplifier (DU) 31 and a comparator ( K) 32. The outputs of the first and second amplifiers 22 and 23 are connected respectively to the first and second inputs of the adder 26 and the differential amplifier 31. The second inputs of the amplifiers 22, 23 and the comparator 32 are connected to a zero potential bus, to which a housing 33 made of electrically conductive is connected material. The design of the housing in which the electronic unit is located does not matter to achieve a technical effect. The output of the measuring circuit 2 includes a gated block (SB) 34. The output of the threshold block 29 through an inverter (Inv) 35 is connected to the control input of the gated block 34. The measuring circuit 2 contains, in particular, a high-frequency generator (G) 35 connected to the thread a diagonal of the bridge circuit 36, in one of the arms of which a measuring cell 1 and a field effect transistor 38 are connected via a capacitor 37. A differential detector (DC) 39, a DC amplifier (CNT) 40, an amplifier 3 s are connected in series to the measuring diagonal of the bridge circuit 36 directs transfer coefficient. The output of the amplifier 40 through an integrator (J) 41 is connected to the gate of the field-effect transistor 38. In general, the measuring circuit 2 can be performed according to other known schemes, for example, as described in the description of the invention according to autosweet. USSR No. 859960 IPC G 01 N 27/02, 1979 The gated block 34 can be made in the form of a gated amplifier, a gated analog-to-digital converter, a controlled key, a relay with normally open contacts or another device whose output signal appears when there is a signal at its control input. The clogging indicator 30 may be made in the form of an LED, an indicator light, an illuminated display, or other known means. The comparison circuit 14 is made, in particular, in the form of two bipolar detectors 42 and 43, the inputs of which are the inputs of the circuit 14, and the outputs are connected to the inputs of the adder 44, the output of which is the output of the circuit 14 (Fig. 3). In the General case, the block 14 can be performed according to other schemes, for example, in the form of two unipolar detectors and a differential amplifier. To increase the accuracy and reduce the transient time, amplifiers with automatic adjustment, switches, and other elements and units can be introduced into the comparison circuit 14 (see, for example, ed. Certificate of the USSR N ° 1029062, IPC G 01 N 27/02, 1981. ) The circuits of all electronic units are well known and are given, for example, in the book Design and use of operational amplifiers. Ed. J. Graham. M .: Mir, 1974, 510s. UDC.621.375.1473. The proposed conductometer works as follows. AX 9J / 3 // 4l: ryat (the note direction in Fig. 2 is indicated by arrows). Under the action of a sinusoidal voltage generated by the source 4, a voltage is excited in the volumetric liquid coil 45 and a current flows whose amplitude is proportional to the conductivity of the liquid. The liquid loop 45 in FIG. 1 is shown conditionally limited. In fact, the boundaries of coil 45 are uncertain, and the entire volume of fluid surrounding corneus 16 is involved in its formation. The current flowing in coil 45 excites a signal proportional to fluid conductivity in winding 9, and a voltage appears at the output of detector 8, whose instantaneous value is proportional to conductivity liquids taking into account the effect of spatial averaging. At the same time, voltages are induced at the ends of the conductors 24 and 25, which are amplified by the amplifiers 22 and 23. If there are no foreign objects in the confuser part and ideal parameters of the circuit elements, the voltages at the outputs of the amplifiers 22 and 23 are equal in amplitude and opposite in phase. The signal at the output of the amplifier 31, proportional to the sum of the amplitudes at its inputs, is converted by block 32 into rectangular switching pulses that control the operation of the synchronous detector 27. After summing the equal in amplitude and opposite in phase voltages, the signals at the outputs of the adder 26, synchronous detector 27, absolute detector 28 values and threshold block 29 are equal to zero. At the output of the inverter 35, a signal appears that turns on the gated block 34. In this case, the clogging indicator 30 is turned off. When using real amplifiers and elements between signals at the outputs of amplifiers 22 and 23, additional phase shifts occur. However, the use of a synchronous detector 27, controlled by the switch 32, virtually eliminates errors due to phase shifts. Therefore, in the case of additional phase shifts between the signals at the outputs of amplifiers 22 and 23 with equal amplitudes, the signals at the outputs of blocks 27, 28, 29 are equal to zero, and block 34 translates the signal of the measuring circuit 2 to the output of the conductometer. voltage proportional to the total conductivity of the electrolytic conductor located between the electrodes 20 and 21, and the channel of the zero transistor 38. This voltage is detected and amplified by blocks 39 and 40, is applied to the inputs of amplifier 3 and integrator 41. If the bridge circuit 36 is not balanced, the output voltage amplifier 40 is not equal to zero. The voltage at the output of the integrator 41 and the channel conductivity of the zero transistor 38 are changed until the voltage amplitudes at the inputs of the differential detector 39 become equal to each other. In this case, the voltage at the output of amplifier 40 is zero. In a similar way, the bridge circuit is automatically balanced at any slow changes in the fluid conductivity in the region of the microelectrode 20. With fluctuations in the fluid conductivity relative to the average value, the channel conductivity of the zero transistor 3 8 does not change, since the integrator 41 does not respond to fast changes in the signal at its input. In this case, a signal proportional to fluctuations of the controlled parameter with a minimum distortion of the high-frequency components in the spectrum of the measured quantity is received at the input of amplifier 3. The coefficient of conversion of conductivity to voltage at the output of amplifier 3 with the selected parameters of the remaining elements depends on the state of the surface of electrode 20 and the non-transmission coefficient of amplifier 3, which, in turn, depends on the voltage at its control input. The output signals of the detector 8 and amplifier 3 are fed to the inputs of the bandpass filters 12 and 13, which select a frequency range that is common for the signals at the outputs of the detector 8 and amplifier 3. The upper cut-off frequency of this range is determined mainly by the design and geometric dimensions of the housing 16, as well as incident flow velocity: with increasing velocity and decreasing spatial averaging scale, the upper cutoff frequency increases. In order for bandpass filters to be used over the entire range of possible flow rates, their upper boundary frequency is selected from the condition v where RV is the upper boundary frequency, Hz; MviHH - minimum speed of the incident note, m / s; and o is the scale of spatial averaging, m. For example, with a minimum incident velocity of 5 m / s and a spatial averaging scale of 0.15 m, the upper boundary frequency should be no more than 33 GP. The choice of the lower cutoff frequency of the filters 12 and 13 is less critical. However, with its decrease, the dimensions of filters operating at infra-low frequencies increase, and the speed of the control circuit decreases. Therefore, the lower frequency is chosen mainly in the range of 1-10 Hz. In the circuit 14, a comparison is made of the signals coming from the outputs of the bandpass filters 12 and 13, in frequency, according to the average rectified value. If the conversion coefficients of the ripple of the electrical conductivity at the output of the amplifier 3 and the detector 8 are equal, the signal at the output of the circuit 14 does not appear, and the output voltage of the integrator 15 and the transfer coefficient of the amplifier 3 remain unchanged. In the case of a change in the sensitivity to pulsations of the measured quantity, the signal at the output of the circuit 14, depending on the ratio of the signals at its inputs, causes a change in the voltage at the output of the integrator 15, which, in turn, changes the transmission coefficient of the amplifier 3. Moreover, if the signal at the output of the bandpass filter 13 exceeds the signal at the output of the filter 12, the transmission coefficient of the amplifier 3 decreases, otherwise the transmission coefficient of the amplifier 3 increases. Changes in this coefficient occur until the signal at the output of circuit 14 becomes zero. In this case, the conversion coefficient of the conductivity pulsations at the output of the amplifier 3 is equal to the conversion coefficient at the output of the detector 8, which is known with high accuracy due to the non-contact measurement method. As a result, a signal appears at the output of amplifier 3 and block 34, the instantaneous value of which with high accuracy is proportional to the measured ripple of conductivity. R min

If a foreign object 46 enters the confuser part of the hole in the housing 16, the specific conductivity of which is greater (less) than the specific conductivity of the controlled liquid medium, the contactless channel sensitivity to pulsations of the controlled parameter sharply decreases, the alternating voltage at the output of the bandpass filter 12 decreases. At the output of circuit 14 a mismatch signal appears, which leads to a change in the signal at the output of the integrator 15, a decrease in the gain of the amplifier 3 and the appearance of a significant shnosti controlled parameter measurement. At the same time, the redistribution of the ratio of the resistances of the sections of the bulk liquid conductor 45 located to the left and right of the electrode 18. At the same time, at the end of one of the conductors 24 and 25, the voltage increases (decreases), and on the other it decreases (increases). The output of the synchronous detector 27 appears a voltage of one or another polarity depending on the ratio of the conductivity of the object 46 and the controlled fluid. The output of the detector 28 appears voltage of only one polarity. If this voltage exceeds the threshold level t /

threshold unit 29 is triggered, indicator 30 lights up, signaling the fact of contamination. The signal at the output of the inverter 35 becomes equal to zero. The gated block 34 is turned off, the signal from the output of amplifier 3 does not pass to the output of the conductivity meter, and the registration of false results of conductivity measurement in the dynamic mode is excluded.

Sensitivity to pollution is determined at fixed values of the parameters of the blocks 22, 23, 26, 27 level t / o threshold

block 29.

This level is chosen based on the response to the redistribution of the resistances of the sections of the liquid coil, corresponding to a change in the average conductivity by several percent. A lower value of the threshold can lead to accidental operation of the unit from interference.

liquids.

in the case of natural or artificial cleaning of the hole in the housing 16, the redistribution of the resistances of the sections of the volumetric liquid coil is eliminated, the signals at the outputs of the amplifiers 22 and 23 become equal in amplitude, while the signals at the outputs of the blocks 27, 28 and 29 are zero, the indicator 30 is turned off, the block 34 turns on, passing the output signal corrected for the low-frequency non-contact channel to the output of the conductometer.

A conductivity meter, an implementation example of which is shown in FIG. 1, allows high-precision reliable measurements of electrical conductivity in a dynamic measurement mode. For highly accurate reliable measurements of the absolute values of conductivity, an embodiment of the conductometer circuit shown in FIG. 5. In this embodiment, the output signal of the measuring circuit 2 is summed in block 47 with the output signal of the detector 8 after respectively high-pass and low-pass filtering by a high-pass filter (HPF) 48 and a low-pass filter (LPF) 49. In the considered option, the output signal is also switched off in the event of a contamination of the conductivity meter and an indication of the fact of clogging.

Using the information presented in the application materials, drawings and using existing technologies, materials and the element base, the proposed conductometer can be manufactured in production and used in environmental monitoring systems for water basins used to detect a mobile source of environmental pollution of the aquatic environment according to the results of simultaneous measurement averaged and ripple values of the specific electrical conductivity of the aquatic environment, in oceanological studies , in experimental hydrodynamics and other areas of technology where it is required to control the parameters of flows of electrically conductive liquid media, which characterizes the utility model as industrially applicable.

In accordance with the materials of the application was made and tested a model of the proposed device. Tests of the layout confirmed the possibility of achieving the technical effect indicated in the application.

Claims (1)

A conductometer containing a contact measuring cell connected to a measuring circuit including an adjustable amplifier, power and measuring transformers placed in a dielectric housing made in the form of a drop-shaped torus with a hole for fluid flow, an AC voltage source connected to a winding located on the toroidal core supply transformer, a detector connected to a winding located on the toroidal core of the measuring transformer, first and second oh bandpass filters, the inputs of which are connected to the outputs of the detector and the adjustable amplifier, respectively, and the outputs are connected respectively to the first and second inputs of the comparison circuit, the output of which through the integrator is connected to the control input of the adjustable amplifier, characterized in that it is coaxial in the diffuser part of the hole for fluid flow a ring electrode is located to this hole, two amplifiers, an adder connected in series, a synchronous detector, an absolute value detector, a threshold are introduced into the device block and clogging indicator, a differential amplifier and a comparator connected in series, the output of which is connected to the control input of the synchronous detector, as well as a gated block and inverter, while the first inputs of the first and second amplifiers are connected to the ring electrode using the first and second conductors, respectively the toroidal core of the supply transformer, the second inputs of the first and second amplifiers and the comparator are connected to the zero potential bus, to which the conduit housing is connected a meter made of electrically conductive material, the outputs of the first and second amplifiers are connected respectively to the first and second inputs of the adder and differential amplifier, and the output of the threshold block through an inverter is connected to the control input of the gated block connected to the output of the measuring circuit.