the amplitude and phase components of the multi-parameter MFP signal with the parameters of wastewater samples, a three-parameter method for joint measurement control of the electrical conductivity χ, relative dielectric constant εr and temperature t of wastewater samples from the production of apple juice. An algorithm for joint multi-parameter measurements of the parameters χ, εr and t based on a transformer electromagnetic transducer (MFP) has been developed, the switching scheme provides for heating a wastewater sample during measurement control to simulate production conditions. Since the amplitude and phase components of the MFP multi-parameter signal depend on the temperature t, sample heating also makes it possible to create information redundancy and improve the accuracy of wastewater sample identification. The implementation of the proposed method makes it possible to indirectly determine the composition of wastewater samples, using only one transducer with known physical properties, all this leads to an increase in the accuracy of measuring the parameters of wastewater samples in comparison with reference methods and measuring instruments and ultimately allows choosing a promising method of wastewater treatment in accordance with the analysis of experimental data. The data obtained indicate the acidic composition of wastewater; therefore, it is proposed to neutralise industrial waste at the outlet of the finished product. The methodology of the above studies lies in the fact that, within the framework of a specific scientific approach, it is necessary to expand the functional and technical capabilities of the electromagnetic device by implementing a new multi-parameter electromagnetic method for joint measurements of the physicochemical parameters of wastewater samples. Design/methodology/approach: The essence of the proposed three-parameter method of joint measurement control of parameters χt, εr and t is based on the analysis of the interaction of an external homogeneous magnetic field with the magnetic field of eddy currents induced in a conductive electrolytic liquid (in a wastewater sample). Based on the input of special normalised parameters, as well as the obtained universal transformation functions G = f(x) and φ = f(x), which relate the physicochemical parameters χ, εr and t of the electrolytic liquid medium (wastewater samples from apple juice production) with the amplitude and phase components of the multi-parameter signal MFP, at a constant frequency of the magnetic field f, the implementation of a three-parameter electromagnetic method of joint measurement control of the electrical conductivity χ, relative permittivity εr and temperature t have been proposed. At the same time, using the thermal MFP switching circuit, it is necessary to measure two magnetic fluxes: the reference magnetic flux F0 in the absence of a glass tube with liquid in the converter and the magnetic flux F2 (if there is a wastewater sample in the converter) and the phase angle φ between the flows F0 and F2. To this end, three wastewater parameters, χt, εr and t, are determined jointly by the same MFP in the same control zone. Implementing the proposed method makes it possible to indirectly assess the composition of wastewater, select a promising treatment method, and then take preventive measures related to environmental protection. Findings: The possibility of applying the MFP operating theory to the realisation of an informative three-parameter electromagnetic method of joint measurements of specific conductivity χ, relative permittivity εr and temperature t parameters of wastewater has been studied. An algorithm for modelling the process of joint multi-parameter measurements of specific conductivity χ, relative permittivity εr and temperature t based on MFP has been developed. The basic relations describing a three-parameter method of joint measurements of specific conductivity χ, relative permittivity εr and temperature t of controlled wastewater samples are presented. The obtained numerical values of the physicochemical parameters of the wastewater sample are in good agreement with the data obtained using the controlling methods. Implementation of the proposed three-parameter method allows to increase in the accuracy of identification of wastewater samples due to the obtained multi-parameter information, as well as to determine indirectly the composition of wastewater samples, using a single transducer with certain physical properties; all this leads to increased accuracy of wastewater sample parameters in comparison with the reference methods and measuring tools, and allows to choose a rational and inexpensive treatment method. Research limitations/implications: The method studied has the following limitations: the range of variation of the diameters is 20 mm to 55 mm. The lower limit is set by the frequency of the electromagnetic field, and the upper limit by the diameter of the transducer frame, 57 mm. Measurements are made in homogeneous longitudinal magnetic fields, and the length of the MFP winding must be ten times the diameter to achieve such field homogeneity. The sample length must be greater than or equal to the winding length of the transducer, i.e., lo⩾ ln. The radial misalignment of the product does not affect the measurement results, as the magnetic field of the transducer is homogeneous. The MFP frame limits product misalignment. It is found that sample misalignment in the range of ±4% to 6% has no practical effect on the measurement results of physicochemical parameters of wastewater samples. The change in temperature causes a change in the resistance r of the magnetising winding, so the windings of the converter must be thermally insulated from the environment (wrapped with mitre tape, coated with BF-19 adhesive and then this structure is baked at the temperature t = 300°C in the EKPS-500 muffle furnace). Practical implications: The practical significance of the work lies in the fact that as a result of the analysis of the obtained values of the physicochemical parameters of wastewater samples, it is possible to timely prevent the reasons for the deviation of wastewater from the specified indicators of international standards governing the discharge of wastewater into the city sewerage and to take measures to prevent pollution of artificial and natural reservoirs located in the residential areas, as well as to develop effective methods of wastewater treatment of food and processing industries. The obtained relations, which describe the universal transformation functions G = f(x) and φ = f(x), algorithms for measuring and calculating operations for determining the specific electrical conductivity χ, relative permittivity εr and temperature t of wastewater samples based on MFP, make it possible to design, construct and create automated measuring installations based on intelligent devices that have a phenomenological approach to the measuring control of physical and chemical parameters of electrolytic liquid media as the basis of their operating theory. Originality/value: The electromagnetic transducer (EMT) theory has been further developed with a sample of a weak electrolytic liquid with an acidic composition (a sample of wastewater from apple juice production).

which considers the influence of informative parameters of beer effluents on the components of the amplitude and phase signals of a multiparameter device. Design/methodology/approach: The implementation of the four-parameter method is carried out on the basis of the dependences G1 = f (A1) and G2 = f (A2) at two frequencies of the electromagnetic field f0 and f1 for acid, alkaline and average effluent and allows you to jointly determine the four parameters of effluent samples with the same converter in the same control area. The proposed method makes it possible to improve the accuracy of identifying effluent samples since the obtained multiparameter information makes it possible to determine the nature and properties of effluent samples using only one transducer with certain physical characteristics. The research results lead to the expansion of the technical capabilities of electromagnetic measurement methods, as well as to an increase in the metrological characteristics of electromagnetic transducers and an increase in the accuracy of measuring the parameters of effluent samples compared to reference methods and measuring instruments. Thus, the implementation of this approach contributes to the prediction and prevention of the reasons for the deviation of beer effluent samples from the specified indicators of environmental safety. Findings: The universal conversion functions MFP have been established, connecting the amplitude and phase components of the converter signals with the parameters k, εr, t and ρ of acidic, alkaline and average effluents. Based on the universal transformation functions G1 = f (A1) and G2 = f (A2), a four-parameter electromagnetic method for joint measurements of electrical resistivity k, relative permittivity εr, temperature t and density ρ of acidic, alkaline, and average effluents from breweries has been developed. When conducting research at two close frequencies of the electromagnetic field f0 = 20.3 MHz and f1 = 22 MHz, algorithms were obtained for measuring and calculating procedures for determining k, εr, t and ρ for samples of acidic, alkaline and average effluents from the brewing industry. Research limitations/implications: Research perspectives consist in the creation of automated systems for multiparameter measuring control of the physicochemical characteristics of acidic and alkaline effluent from food and processing industries based on the immersed electromagnetic transducer. Based on the data obtained using informative methods to measure the parameters of effluent samples, an integrated method for treating beer effluents of various compositions will be proposed. At the same time, the scheme of the integrated treatment method should include a filter that provides the introduction of a magnetic fluid and a separation device that allows us to remove a fraction, including pollution in itself. Practical implications: Is that the proposed four-parameter electromagnetic method makes it possible to determine to what composition the controlled samples of wastewater should be attributed (acidic or alkaline). It, in turn, makes it possible to choose a rational method for treating beer effluents and to prevent the reasons for the deviation of effluent samples from the environmental safety indicators set by the standards. Originality/value: of the article is the research related to the expansion of the functional and technical capabilities of the electromagnetic two-frequency transducer MFP through the implementation of a four-parameter electromagnetic method of joint measurements of electrical resistivity k, relative permittivity εr, temperature t and density ρ of acidic, alkaline and average effluents from breweries. The universal transformation functions G1 = f (A1) and G2 = f (A2) found in the work at two close magnetic field frequencies, f0 = 20.3 MHz and f1 = 22 MHz, make it possible to control four physicochemical parameters of acidic, alkaline and average wastewater at the same time by the same MFP. An algorithm has been developed for determining the signal components of a two-frequency thermal MFP, the ranges of which correspond to the ranges of changes in electrical resistivity k, relative permittivity εr, temperature t and density ρ of acidic, alkaline, and average brewery effluents. The basic relations that describe the two-frequency four-parameter electromagnetic method of joint measurements of the physicochemical parameters of acidic, alkaline and averaged beer effluents have been obtained.

electrical conductivity λt and the temperature t of the beer sewage sample. It should be noted that this makes it possible to simultaneously prevent the causes of beer sewage samples deviation from the specified environmental safety indicators and to take adjustments. Design/methodology/approach: The theory of TTC operation concerning the electrical and temperature characteristics testing of beer sewage samples has been further developed by implement new universal transformation functions Δφt = f (Gt) and Δφ = f (xt), which relate the normalized difference components of the converter signals to physical and chemical characteristics of the sample. Due to this, it is possible to simultaneously prevent the causes of beer sewage samples deviation from the specified ecological safety indicators and to take appropriate adjustments. Findings: The method of two-parameter measuring test of the specific electrical conductivity λt and the temperature t of the beer sewage sample was developed on the basis of new universal transformation functions. Analysing the numerical data of electrical conductivity λ, TDS and pH at the initial temperature t1 = 15°C, the alkaline nature of beer sewage was determined. Research limitations/implications: The frequency range of the magnetic field f = 80-100 MHz, it is difficult to maintain in laboratory conditions, so the proposed method requires the use of modern high-frequency equipment, the radius of the probe depends on the radius of the primary converter frame. And therefore is quite a complicate to find appropriate tank. Practical implications: is to determine the nature of beer sewage based on the results of electrical and temperature parameters measurements during implementing a two-parameter eddy current method, which allows to prevent the reasons for beer sewage samples deviations from the specified environmental safety measures and to take appropriate adjustments. An important practical result is also the determination of the signal components and the normalized characteristics of the primary eddy current converter with a sample of beer sewage. They allow to calculate, design and create multi-parameter automated devices for measuring test of the physicochemical parameters of beer sewage samples. In turn, as a result of the physicochemical composition analysis of the sample, improving the accuracy of measurements of physicochemical parameters - there is an opportunity to improve and create advanced methods of wastewater purification on a weak electrolytic basis. Originality/value: The article originality is the investigation of the theoretical rules of thermal TTC by implementing a new multi-parameter eddy current method of measuring the specific electrical conductivity λt and the temperature t of the beer sewage sample based on the implementation of universal transformation functions Δφt = f (Gt) and Δφ = f (xt) that relate the converter signals to the physicochemical characteristics of the beer sewage sample, which helps to prevent the causes of the beer sewage samples deviation from the specified environmental safety indicators and take appropriate adjustments.