SU1733989A1 - Method of determining a sea water salt level and device thereof - Google Patents

Abstract

The invention can be used for hydrological and oceanographic research. Measurements of salinity are performed indirectly, by direct conductometric measurements in one working and two model measuring cells, in pairs. Moreover, the variable factor is the frequency, which varies in the range of 20-500 Hz. From the results of cumulative measurements, the value of salinity is determined. A device that implements a method for determining the salinity of seawater automates the measurement procedure by switching cells in accordance with a given radiation algorithm. 2 sec. item f-ly, 1 ill. C / 1

Description

The invention relates to a measurement technique, in particular, to measuring the concentration of dissolved salts in water, and can be used for automated measurements of salinity in situ in coastal or estuarine areas under conditions of strong desalination of seawater and significant salt variability, for measuring salinity sea ice, river water, as well as in areas of industry where it is necessary to measure low concentrations of dissolved salts,

The known method of determining the concentration by ionic nitration, when the sum of the ions of the dissolved salts is determined and the concentration is estimated from the measurement results.

The disadvantages of the method include the impossibility of using it to determine the salinity in situ, which does not allow its inclusion in the system of automated data collection. The method is very labor intensive. Expensive reagents (e.g., silver nitrate) are required to implement the method.

The closest to the present invention is a method for determining the salinity of seawater, which consists in measuring in two conductometric measuring cells with the test and exemplary salt media, determining the relative electrical conductivity of the test and reference media by the conductometric method and

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calculate the salinity based on the measurement results.

The disadvantage of the method lies in the low accuracy in the region of low salinity and / or non-salinity inconsistencies.

The purpose of the invention is to improve the measurement accuracy in the region of low salinity and / or under conditions of inconsistency in the salt composition.

The drawing shows a block diagram of a device that implements a method for determining the salinity of seawater.

The method is implemented in the following sequence of operations.

Measurements are made in three two-electrode conductometric measuring cells (working and two model), and the sample cells are filled with solutions of different salinity. Different currents are passed through the electrodes of the first model and working measuring cells. The frequency of the alternating current FI is measured in the frequency range of 20-500 Hz, so that, at the frequency of FI, the voltage drops on the working electrodes and the first exemplary cells () are equal.

Pass currents of equal size through the electrodes of the second exemplary and working measuring cells. The frequency of the alternating current is changed to a value of F2 in the frequency range of 20-500 Hz, at which the equality

U2 82

where 1H is the voltage drop across the electrodes of the first exemplary cell;

U2 is the same on the electrodes of the second model cell,

51 values of the salinity of the solution in the first exemplary cell;

52- the same, in the second exemplary cell. Based on known values of Si salinity

and 82 and voltage drops Ui and IJ2 by the formula

0)

Sx si + MS2 Si)

Bx 51 Ui-U2

(2)

calculate the desired salinity value Sx. The closest to the proposed by the technical nature of the device that implements the method of determining the salinity, is a multi-channel conductivity meter containing two conductometric measuring cells, one working and one model, tunable in frequency and amplitude of the alternating current generator and meter.

The disadvantage is low accuracy, especially in the area of low salinity.

The purpose of the invention is to improve the measurement accuracy.

The drawing schematically shows a device for implementing the method.

The device contains an alternating current generator 1 with tunable frequency and

0 amplitude, input device 2, switch 3, voltmeter 4, conductometric probe 5, including the first exemplary cell 6, the working cell 7, the second exemplary cell 8, electrodes 9, horizontal

5 walls 10, connecting jumpers 11. All three cells 6-8 are included in a single structural conductivity probe. The working cell 7 is made flow and is formed of two exemplary cells 6,

0 cell 8 is in between. The two vertical walls of the working cell 7 are the common walls of the adjacent model cells 6 and 8. These walls, as well as two other parallel walls of the model cells.

5 are made of metal and are electrodes. The horizontal walls of 10 cells 6 and 8 are made of dielectric.

To the two-wire input of the input device 2 is connected to the generator 1, and three

0 two-wire, the output of the input device 2 is connected to the corresponding inputs of the switch 3. The fourth and the fifth two-wire inputs of the switch 3 are connected to the electrodes of the exemplary measuring

5 cells 6, 8. The output of the switch 3 is connected to a voltmeter 4.

Since one electrode of cells 6 and 8 form an electrode pair of a working measuring cell 7, the switching of this

0 electrode pairs are provided in switch 3.

The device works as follows.

Alternating current with frequency F

5, the generator 1 is fed to the input of the input device 2, which is, for example, three galvanically developed L-shaped resistive circuits, in which the resistor connected in parallel with the output impedance of the generator is variable and serves to set the current value. From the output of the device 2 through the switch 3 serves an alternating current with a frequency FI in the frequency range 20-500 Hz on

5 electrodes, for example, working 7 and first exemplary 8 (filled with a solution of known salinity Si) cells. Using variable resistors, devices 2 establish equal currents flowing through the named electrodes so that when

The frequency Fi was equal to the voltage drop on the electrodes 9 of the working 7 and the first exemplary 6 measuring cells ().

Using the switch 3, the output of the device 2 is connected to the electrodes 9 of the working 7 and the second model 8, filled with a solution with a salinity S2, of the cells. Pass through the named electrodes currents of equal magnitude. The alternating current frequency of generator 1 is changed to a value of F2 in the frequency range of 20-500 Hz, at which equality (1) is fulfilled.

From the known values of the salinity Si and 82 and the measured values of the voltage Ui and U2, the desired value of salinity Sx is calculated by the formula (2).

Claims (2)

1. The method for determining the salinity of sea water, which consists in measuring in two conductometric measuring cells with the test and exemplary salt medium, determines the specific electrical conductivity of the test and model environments and calculates the salinity based on the results of measurements differing from that, in order to increase the accuracy of determination in the region of low salinity and (or) under conditions of non salt composition, an additional measurement is carried out in a third sample cell filled with a solution with a salinity different from that of the first model cell, for which equal currents are passed through the electrodes of the first model and working measuring cells, change the frequency of the alternating current FI in the frequency range 20-500 Hz, until the voltage on the electrodes is equal working and first model cells (), pass currents of equal magnitude through the electrodes of the second model and working measuring cells, measure the frequency of the alternating current Fa in the frequency range 20-500 Hz until equality Ul si u2 s2 where Ui is the voltage across the electrodes of the first exemplary cell; U2 is the voltage drop across the electrodes of the second exemplary cell; Si is the salinity of the solution in the first model cell; $ 2 is the salinity value of the solution in the second model cell, using the known salinity values of Si and S2, the desired salinity values are calculated by the formula Ј-Ј., Ui (S2-Si) bx b1 Ui-Uz 2. A device for determining the salinity of seawater, containing two conductivity meters, working and exemplary, frequency and amplitude tunable alternator and voltage meter, characterized in that, in order to improve the accuracy of measurements, the device is equipped with an additional second exemplary measuring cell identical to the first model cell, all three cells are cylindrical and combined into one construct, in which the cells are located coaxially so that The barrel cell is made flow through and is located between two sample cells, the working cell walls being common with the walls of adjacent standard cells, these walls, as well as two other parallel walls of the model cells, are made of metal and are electrodes, and the horizontal walls of the sample cells are made of the dielectric material, an input device and a switch are also inserted in the device, where a generator is connected to the two-wire input of the input device, and three two-wire outputs of the input device va connected to three respective inputs of the switch to the fourth and fifth inputs of the two-wire switch of exemplary electrodes connected cells, and the switch output is connected to the meter.