L.R. Grigoryan, N.M. Bogatov, A.L. Grigoryan
Kuban State University
Russian Federation, Krasnodar, Stavropolskaja St., 149
In the present work the problem of development of tools for ensuring human ecological safety is considered which is caused by an increase in the depth of knowledge of human interaction with nature. This topic is quite extensive, but it is obvious that the problem of ensuring the quality of water and food is most relevant. Among the analytical instruments for quality control the most widely used are the meters of ionometric water parameters using an electrometric method based on measuring the relative electrical conductivity characterizing the amount of ion compounds dissolved in the studied medium.
The aim of the work is to find the optimal circuitry for electrometric water analyzers.
The paper presents two variants of constructing devices that differ in their versatility and in the solution of the measurement problems. The operation of both instruments is based on direct measurement of the resistance of the medium under study, determined by the number of investigated compounds in the medium and the distance between the probe electrodes of the instrument. In both variants, digital potentiometers and synchronous detectors realized using the scheme with two additional keys we used. This allows regardless of the type of medium under investigation: first, to change the amplitude of the reference signal and adapt it taking into account the characteristics of the medium, which makes it possible to increase the accuracy of measuring the ion concentration; secondly, to use a smooth (linear) switching mode of the reference signal modulator, which excludes transients during measurement, and reduces the intrinsic error of the ionometer; thirdly, the choice of the synchronous detector circuit has made it possible to practically eliminate the influence of both internal and external interference and interference and, thus, to solve the problem of increasing noise immunity.
The conducted research has shown that in the implementation of environmental safety it is advisable to focus on assessing the quality of water and food. In this context, an analysis of available ionometry equipment has been carried out, which has made it possible to develop a universal ionometer that provides measurement of the electrical conductivity and the pH of the water, as well as the nitrates of fruit and vegetable products. The methods of calibration of the developed ionometers have been optimized and refined. The requirements to the sensor design are optimized depending on the type of the measured parameter, their constructive interface with the meter. Prototype devices have been developed by laboratory and full-scale tests, as well as approbation at enterprises of the agricultural and industrial complexes of the Krasnodar region, which confirmed their high operational and metrological indicators. In particular case as for parameters the following error was obtained by express analysis of water:
– in pH meter mode with the E-201-c pH sensor;
– in conductivity meter mode (measurement of electrical conductivity, mineralization, hardness).
Keywords: personal control of human vital activity, ionometers, conductivity meter, pH-testers, circuit
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