Hydraulic systems in modern vehicles and agricultural machines have many components. In order to achieve high efficiency of the system, the system requires an accurate filtration system that allows you to reduce the amount of contaminants. Therefore, an important aspect is to determine the content of impurities in the working liquid, so we can diagnose and then predict the durability of the entire hydraulic system. This paper presents selected methods and means of state assessment, as well as the methodology for testing the working fluid. The results of experimental studies conducted in accordance with the developed methodology have been presented, which made it possible to obtain an appropriate analysis of results and draw appropriate conclusions. The results of the research confirmed the validity of the research activities undertaken using the passive experiment.

The paper represents the mathematical model for diagnostics of solar cell. The research objectives are the problem of determining a solar cell technical condition during its operation. The solar cell diagnostics is based on the mathematical model of solar cells. The single-diode solar cell model is characterized by a slight deviation of the theoretically calculated characteristics from the characteristics of the real solar cell, one of the reasons being the complexity of the accurate measurement of the series resistance. The single-diode solar cell model uses the current and voltage ratio in the form of an implicit function and it cannot be solved directly. For its solution it is necessary to use numerical methods. This is main disadvantage of the single-diode solar cell model. The methodological approach to increasing the reliability of the solar cell diagnostic has been proposed, in terms of multi-parameter the solar cell diagnostic by applying the solar cell impedance model.

The paper presents the possibilities of using vibroacoustic methods in the study of the technical condition of designed multimedia mobile scenes. In particular, the possibility of implementing modal analysis methods in modelling and diagnostic research process has been presented. The use of virtual methods enables diagnostic tests both at the design stage and at the stage of normal operation, whereas modal methods help to explain the nature of the work of the element under investigation.

Abstract. This article presents low cost diagnostic system, dedicated to rolling bearings. This system can be widely used in existing machines, to improve their reliability and reduce the costs of maintenance. Low cost electronics sensors, a few microchips, a multi-meter and a programmable micro-controller, which can send data to a computer, were selected. A computer is not necessary in this system, because data can be directly presented on LCD displays; moreover, alarm levers can be signaled with flashing lights and buzzers. This shows that an operational system can be produced with low cost, which is not obvious for managers and mechanical engineers.